Cation Exchange Capacity Research Papers (original) (raw)

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- Sustainable Development, Conservation Agriculture, Soil Quality, Soil Degradation

The effect of Fe oxidation state on the surface charge (CEC) and solubility of smectites were studied using the <2-t~m, Na+-saturated fraction of an Upton, Wyoming; a Czechoslovakian; and a New Zealand montmorillonite; and a Garfield, Washington, nontronite. The reduction of structural Fe 3+ in the octahedral sheet of each clay produced a net increase in the negative surface charge of the clay. The observed cation-exchange capacities deviated from the linear relationship predicted by charge-deficit calculations, assuming changes only in the Fe2+/Fe a+ ratio, and reversibly followed Fe reduction according to a 2nd-degree polynomial function. The deviations suggest reversible changes in mineral structiite and composition during Fe reduction. These clays were susceptible to partial dissolution in citrate bicarbonate (CB) and citrate-bicarbonatedithionite (CBD) solutions. Small amounts of Fe and Si dissolved as a result of Fe reduction in CBD, but affected < 1% of the total clay mass except for the Czechoslovakian clay in which 2% of the clay dissolved. Although slightly more Fe dissolved than Si, no change in surface charge was noted. Almost no dissolution of these elements was detected in CB solution. In contrast, significant Al was detected in the CB solution, suggesting a heterogeneous dissolution mechanism. The CEC, however, was unchanged by the CB treatment. These results may be explained by the adsorption of hydrogen ions into the vacated AP + sites in the mineral structure. Dissolution seems to have been independent of the effects of Fe oxidation state on surface charge.

- by D.C. Golden
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- Geology, New Zealand, Iron, Soil sciences

The capability of 14 zeolites synthesized from different fly ashes (ZFAs) to sequestrate Cr(III) from aqueous solutions was investigated in a batch mode. The influence of pH on the sorption of Cr(III) was examined. ZFAs had a much greater ability than fly ash to remove Cr(III), due to the high cation exchange capacity (CEC) and the high acid neutralizing capacity (ANC) of ZFAs. The mechanism of Cr(III) removal by ZFAs involved ion exchange and precipitation. A high-calcium content in both the fly ashes and ZFAs resulted in a high ANC value and, as a result, a high immobilization capacity for Cr(III). The pH strongly influenced Cr(III) removal by ZFAs. Inside the solubility range, removal of chromium increased with increasing pH. Hydroxysodalite made from a high-calcium fly ash had a higher sorptive capacity for Cr(III) than the NaP1 zeolite from medium-and low-calcium fly ashes. On the other hand, at pH values above the solubility range, the efficiency of chromium removal by the ZFAs approached 100% due to the precipitation of Cr(OH) 3 on the sorbent surfaces. It is concluded that ZFAs and high-calcium fly ashes may be promising materials for the purification of Cr(III) from water/wastewater.

- by Feleke Zewge
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- Engineering, Chemistry, Water, Carbon

While non-point nutrient loads are important determinants of biological productivity in Southeastern Piedmont impoundments, productivity can be attenuated by concomitant sediment loads that reduce the biological availability of these... more

- by Zhulu Lin
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- Water quality, Multidisciplinary, Software modelling and simulation, Iron Oxide
- by Sankar Ghatak
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- Thermogravimetry, Insertion, Thermal Analysis, X ray diffraction

We compared the microbial community composition in soils from the Brazilian Amazon with two contrasting histories; anthrosols and their adjacent nonanthrosol soils of the same mineralogy. The anthrosols, also known as the Amazonian Dark Earths or terra preta, were managed by the indigenous pre-Colombian Indians between 500 and 8,700 years before present and are characterized by unusually high cation exchange capacity, phosphorus (P), and calcium (Ca) contents, and soil carbon pools that contain a high proportion of incompletely combusted biomass as biochar or black carbon (BC). We

- by Siu M Tsai
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- Microbiology, Mineralogy, Soil, Microbial Ecology

Synthetic saponite-like materials were prepared by traditional hydrothermal crystallisation at 513 K of 1 SiO 2 ; 0.835MgO; 0.056Al 2 O 3 ; 0.056Na 2 O; nH 2 O gel with variable amount of H 2 O. The obtained layered materials were submitted to a systematic study of textural properties, morphology, thermal behaviour of the produced materials by combining different experimental techniques (XRD, SEM, TEM, N 2 physisorption, Solid State MAS NMR). For the first time, a fine characterisation of the surface acidity of the produced saponites performed by FTIR spectroscopy of CO probe molecule (complemented with NH 3 ) was given.

- by Leonardo Marchese and +1
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- Engineering, Materials Engineering, Mechanical Engineering, Chemical Engineering

The near infrared analysis (NIRA) approach was studied to examine its capability for predicting spectral feature soil properties from the reflectance curves in the near infrared (NIR) region (1-2.5 um) of arid and semiarid soils. High-resolution diffuse reflectance spectra (3113 spectral points) in the NIR region were recorded for 91 soil samples from Israel. Six soil properties (clay content, specific surface area, cation-exchange capacity, hygroscopic moisture, carbonate content, and organic matter content) were measured by routine methods employed in soil laboratories. An empirical model to predict each property from its spectral signature was developed by adapting the NIRA technique. Several data manipulations were used to obtain optimum performance. The optimum performance of all properties was found to be between 25 and 63 spectral points. Strong support for the NIRA capability was provided by its ability to examine most of the spectral assignments. A slight bias was observed for the prediction of both organic matter and hygroscopic moisture, suggesting that more attention in the prediction of these constituents is required. It was concluded that NIRA is a promising method for rapid and nonrestrictive analysis of soil materials, and further study of the synergism between NIRA and soil materials is recommended. N EAR-INFRARED ANALYSIS is a laboratory approach that analyzes the diffuse reflectance radiation with regard to a material's chemistry (Stark et al., 1986). This methodology was developed 25 yr ago for rapid analysis of moisture in grains (Ben-Gera and Norris, 1968). Today, NIRA is well accepted and widely used in many other disciplines (Davies and Grant, 1987; Norris, 1988). This method is known for its rapidity, convenience, simplicity, accuracy, and ability to analyze many constituents at the same time (Stark et al., 1986). In

- by E. Ben-dor
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- Environmental Science, Near Infrared, Soil Analysis, Biological Sciences

apsule'': Soil pH greatly in¯uenced adsorption and movement of heavy metals.

- by Liovando Da Costa
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- Soil, Brazil, Hazardous Waste, Environmental Pollution

In this study, total heavy metal contents and their relationships with soil microbiological characteristics were investigated in agricultural soils which were with polluted heavy metals. Total heavy metal content of the soils varied from... more

- by R kkk
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- Soil Science, Environmental Soil Science, Soil Pollution, Biological Sciences

field study was conducted at five villages of Botswana namely, Tsabong, Tshane, Mathathane, Motlhabaneng and Tsetsejwe during the periods of June to August 1999 and June to August 2000. The objective of the study was to assess and compare the soil physicochemical properties of soils at the five villages and to study the effect of cultivation on some soil physical properties. Parameters measured in the field included soil pH, organic carbon (OC), phosphorus (P), cation exchange capacity (CEC), exchangeable cations (Ca, Mg, K and Na), bulk density (BD), soil penetration resistance and infiltration rate. Soil pH, OC, CEC, Mg, Ca and BD were found to be significantly different in the five villages. The non-cultivated soil was found to have significantly lower bulk density, higher infiltration rate and higher penetration resistance compared to the cultivated soil. Soil from the Kgalagadi area was found to be significantly lower in nutrients in comparison with the soil from the Bobirwa ar...

- by Flora Pule-Meulenberg
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- Phosphorus, Soil Degradation, Field Study, soil pH

Crown defoliation of oak (Quercus robur and Q. petraea) was analysed in 808 trees during three forest condition surveys (1988, 1993, and 1999) in the southern Sweden. From 1988 to 1999 crown defoliation increased by more than 20%. Changes in crown defoliation were related to the pH in the upper 20-30 cm of the mineral soils, which was closely connected to other measures of soil fertility (cation exchange capacity, CEC and C/N ratio). Trees growing on soils with a high pH (≥4.00, in BaCl 2 filtrate), high CEC and low C/N ratio had significantly lower crown defoliation than trees growing on more acid soils (pH <4.00), indicating that less favourable soil conditions may further enhance oak decline. Age did not differentiate trees with respect to crown defoliation, indicating that decline in crown condition was not due to an age-related increase in crown transparency. Considering only trees younger than 100 years, a significant interaction was observed between changes in crown defoliation and soil pH. Trees younger than 100 years old growing on more acidic soils had a greater increase in crown transparency than trees on more basic soils between 1988 and 1999. Trees ≥100 years old had significantly higher defoliation on more acidic than on more basic soils, however defoliation dynamics of these trees over 1988-99 was not related to soil acidity. Two biotic agents (insect and fungal leaf infections) evaluated in this study did not prove to be important drivers of defoliation dynamics.

- by kerstin sonesson
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- Soil, Environmental Monitoring, Fungi, Multidisciplinary

The floodplain of the Morava River in Strážnické Pomoraví, south-east Moravia, Czech Republic contains a very valuable record of regional environmental change, which goes back to several thousand years. Its interpretation has been limited by poor stratigraphic correlation and dating of the sediments. We present a geochemical solution to this challenge. We studied 8 outcrops of floodplain deposits from 4 localities along a 6 km long part of the current meander belt of the Morava River in Strážnické Pomoraví using geochemical proxy analyses, magnetic susceptibility measurements, 14 C dating of wood remnants, and sediment micromorphology. The proxy methods are based on elemental analysis (EDXRF) and analysis of the cation exchange capacity of clay minerals; granulometric analyses provided the basis for lithological and facies assignment of the sediments. Our geochemical and mineralogical interpretations have further been tested by microstratigraphically studying the optical properties of the fine fraction. Horizons older than about 3 centuries were 14 C dated using wood remnants and the age of deposits from the last century was determined on the base of several proxies reflecting their industrial contamination by heavy metals and magnetic particles. The mean depositional rate over the period from about 1000 to about 1900 AD ranged from 0.2 to 0.6 mm y − 1 , depending on the sedimentary facies. The coeval lithological change in the majority of the studied sections indicated a change of the meander belt structure at between~1200 AD and~1600 AD probably as a consequence of changes of channel structure. The alluvial deposition in the 20th century was strongly affected by the river regulation.

- by Aleš Bajer and +1
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- Geology, Geochemistry, Clay Minerals, Environmental Change

Adsorption, exchange and retention phenomena at the solid-aqueous solution interface. 1. Influence of structural, textural and superficial properties of solids. A crucial step, leading to a proper understanding of adsorption mechanisms at the solid-aqueous solution interface, lies in the precise determination of the structural, textural and energetic properties of the solid phases under study. The various conventional techniques for characterizing the textural properties (specific surface area and porosity) are first reviewed. The use of a new adsorption volumetric technique in quasiequilibrium conditions is then detailed. Using such a technique, the gas adsorption isotherm can be obtained precisely on the whole domain of monolayer filling. The DIS (Derivative Isotherm Summation) method applied to the experimental results then allows a study of the surface energetic heterogeneity, which was difficult to assess using conventional techniques. Two examples are then used to illustrate the potentialities of the technique. Through a judicious choice of the adsorbate, such analysis can be used to characterize the exchange properties of solids and to assign precisely the crystallographic origin of the Cationic Exchange Capacity (CEC) of kaolinite. It can also be utilized to understand the retention mechanisms of organic pollutants such as phenol on activated carbons. © 2000 Académie des sciences / Éditions scientifiques et médicales Elsevier SAS

- by L. Michot and +1
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- Activated Carbon, Specific surface area, Cation Exchange Capacity, Adsorption Isotherm Models

Esterification of acetic acid with n-butanol catalyzed by supported heteropoly acid dodecatungstophosphoric acid, H3PW12O40 (DTP), on acid modified Montmorillonite clay (AT-Mont) matrix were carried out. Among different catalysts, 20% DTP supported onto AT-Mont (15 min) showed the highest catalytic activity with 88% conversion having nearly 100% selectivity towards n-butyl acetate.

- by SIDDHARTHA BHORODWAJ
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- Chemical Engineering, Catalysts, Heterogeneous Catalysis, Catalyst

Natural organic biomass burning creates black carbon which forms a considerable proportion of the soil’s organic carbon. Due to black carbon’s aromatic structure it is recalcitrant and has the potential for long-term carbon sequestration in soil. Soils within the Amazon-basin contain numerous sites where the ‘dark earth of the Indians’ (Terra preta de Indio, or Amazonian Dark Earths (ADE)) exist and are composed of variable quantities of highly stable organic black carbon waste (‘biochar’). The apparent high agronomic fertility of these sites, relative to tropical soils in general, has attracted interest. Biochars can be produced by ‘baking’ organic matter under low oxygen (‘pyrolysis’). The quantities of key mineral elements within these biochars can be directly related to the levels of these components in the feedstock prior to burning. Their incorporation in soils influences soil structure, texture, porosity, particle size distribution and density. The molecular structure of biochars shows a high degree of chemical and microbial stability. A key physical feature of most biochars is their highly porous structure and large surface area. This structure can provide refugia for beneficial soil micro-organisms such as mycorrhizae and bacteria, and influences the binding of important nutritive cations and anions. This binding can enhance the availability of macro-nutrients such as N and P. Other biochar soil changes include alkalisation of soil pH and increases in electrical conductivity (EC) and cation exchange capacity (CEC). Ammonium leaching has been shown to be reduced, along with N2O soil emissions. There may also be reductions in soil mechanical impedance. Terra preta soils contain a higher number of ‘operational taxonomic units’ and have highly distinctive microbial communities relative to neighbouring soils. The potential importance of biochar soil incorporation on mycorrhizal fungi has also been noted with biochar providing a physical niche devoid of fungal grazers. Improvements in soil field capacity have been recorded upon biochar additions. Evidence shows that bioavailability and plant uptake of key nutrients increases in response to biochar application, particularly when in the presence of added nutrients. Depending on the quantity of biochar added to soil significant improvements in plant productivity have been achieved, but these reports derive predominantly from studies in the tropics. As yet there is limited critical analysis of possible agricultural impacts of biochar application in temperate regions, nor on the likelihood of utilising such soils as long-term sites for carbon sequestration. This review aims to determine the extent to which inferences of experience mostly from tropical regions could be extrapolated to temperate soils and to suggest areas requiring study.

- by neil hipps
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- Soil Mechanics, Carbon Sequestration, Biological Sciences, Environmental Sciences

The sandy carbonatic soils of Pacific atolls are considered infertile and poorly suited to agriculture. The Republic of the Marshall Islands is comprised predominantly of atolls, and there is scant information on the fertility status of the Marshall Island soils. We conducted a survey of the soils to quantify chemical properties and determine significant trends related to soil distribution and climate. A total of 116 surface (0-15 cm) soil samples from 13 atolls and 42 subsoil (15-45 cm) samples from five of the atolls were analyzed for pH, electrical conductivity (EC), organic carbon (OC), total nitrogen (TN), cation exchange capacity (CEC), and nutrient levels. A missing element study in the greenhouse on a typical soil from Majuro Atoll was conducted to rank soil nutrient deficiencies. There were some strong differences in soil chemical properties between the two depths, but not necessarily between the two soil series constituting the sampled soils. Soil chemical properties were not affected by a strong rainfall gradient running from the southern (≈4000 mm) to the northern (≈1350 mm) atolls, but human activity had a significant effect on some properties. Soils located near the center of islands tend to show higher concentrations of OC than soils located along the ocean exposed shoreline. The missing element study indicated that the soil was deficient in Cu, P, N, S, and K. Potassium was the most serious nutrient constraint whereas the micronutrients Fe, Mn, Zn, and B did not limit maize growth significantly in a greenhouse pot experiment. Interpreting soil test data on atoll soils, however, remains difficult for two reasons: (i) the soil tests have not been calibrated with crop growth, and (ii) standard soil tests may not be applicable to the unique physical and chemical properties of atoll soils.

- by Anna Khoo
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- Biological Sciences, Environmental Sciences, Maize, Crop Production

The aim of this study was to speed up the composting process of municipal solid wastes, piles of material were inoculated with a mixed of endogenous microorganism. The bacteria identified were Bacillus subtillis and Pseudomonas fluorescens and one fungus, Aspergillus fumigatus. An inoculant was prepared in a concentration of 1x10 7 UFC/ml for each microorganism and was applied through aspersion, 2 L m -3 . The following parameters were evaluated: Physical aspect, temperature, moisture content, pH, C:N ratio, organic matter, electric conductivity and cation exchange capacity. The results showed that inoculated piles reached the stability and maturity, four weeks earlier than the control pile without inoculation. These results suggested that the inoculant was useful to accelerate the composting process in the urban wastes.

Humic acid with hydroxyl-, phenoxyl-, and carboxyl-reactive groups can form coordination compounds with metals. The ionexchange equilibrium method using Dowex AG 50W-X8, 20-25 mesh Na ؉ form was used to determine stability constants of complexes formed between humic acid (isolated from the soil) 50+250 g (+3 ؋ 10 ؊ 5 +15 ؋ 10 ؊ 5 mol/liter) and metal salts solution 200 g at pH 3.5. The stability constant (log K) for di4erent metal+humic acid complexes indicated the following order of the stabilities of complexes formed between humic acid and metal ions: Cu > Fe > Pb > Ni > Co > Ca > Cd > Zn > Mn > Mg. The data on stability constants demonstrated substantial deviation from Irwing+Williams series reported for divalent ions. The molar humic acid/metal ratios were also calculated. Some of the factors a4ecting the stability constants such as cation exchange capacity of humus soil, molecular radius, and molecular surface area of humic molecules were also estimated. The signi5cance of the data to predict the behavior of these complexes in the environment is discussed.

- by Shri Pandey
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- Algorithms, Environmental Pollution, Environmental Sciences, Humic Substances

Growing agricultural crops under Millettia ferruginea (Hochst.) Baker, a tree that is endemic to Ethiopia, is an age-old practice in the country, but the beneficial effects of the tree on crops have not been scientifically quantified. To... more

- by Legesse Negash
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- Agroforestry, Canopy, Phosphorus, Maize

of forest humus forms, based on taxonomic studies (Green et al., 1993; Brê thes et al., 1995), to a quantitative A quantitative assessment of forest humus forms is suggested, on evaluation of humus quality, through development of a the basis of a scale ranging from 1 (Eumull) to 7 (Dysmoder) which humus index. This index assumes that humus forms can is called the humus index. Regression analyses showed that this index was well-correlated with several morphological as well as chemical be scaled and this scale can be correlated with morphovariables describing forest floors and topsoil profiles: thickness of the logical or chemical data describing forest floors and Oe horizon, depth of the crumby mineral horizon, Munsell hue, pH KCl topsoil profiles. In particular, it can be hypothesized and pH H2O , H and Al exchangeable acidity, percentage base saturation, that scaling humus forms according to the degree of cation-exchange capacity, exchangeable bases, C and N content and incorporation of litter (development of Oi, Oe, and Oa available P of the A horizon. The suggested humus index could be horizons) and to the development of a crumby structure J.-F. Ponge, Museum National d'Histoire Naturelle, Laboratoire d'É cologie Gé né rale,

Lack of adequate nutrient supply and poor soil structure are the principal constraints to crop production under low input agriculture systems of West Africa. Experiments at two sites (Mediga and Yimtenga) were conducted in Burkina Faso to assess the impact of compost on improving crop production and soil properties. In the first experiment, compost was applied at the rate of 0 and 10 Mg ha−1 in Mediga on a Ferric Lixisol, and 5 and 0 Mg ha−1 on a Ferric-gleyic Lixisol in Yimtenga. A second experiment was conducted in Yimtenga to assess the role of compost in mitigating the effect of delay in sowing on crop performance. 0 and 5 Mg ha−1 compost plots were sown within the normal period for sowing sorghum (Sorghum bicolor L. Moench) and with a delay of 1 month. A randomised block design was used with four replications for the two experiments.Semi-structured interviews were used to study socio-economic issues of compost technology. No significant difference in soil organic matter content was found between treatments receiving compost and no-compost. However, compost application increased soil cation exchange capacity (CEC) from 4 to 6 cmol kg−1. Soil pH was also increased by the compost application. Sorghum yield tripled on the 10 Mg ha−1 compost plots and increased by 45% on the 5 Mg ha−1 compost plots, compared to no-compost plots. Compost application mitigated the negative effects of a delay in sowing. The study showed that farmers were aware of the role of compost in sustaining yield and improving soil quality. However, lack of equipment and adequate organic material for making compost, land tenure and the intensive labour required for making compost are major constraints for the adoption of compost technology. It was concluded that compost application could contribute to increase food availability in the Sahel and therefore, efforts should be made to alleviate the socio-economic constraints to the adoption of compost technology.

- by L Mando
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- West Africa, Land tenure, Environmental Sciences, Burkina Faso

The total specific surface area (TSSA) and smectitic layer charge (Q s ) calculated from the structural formulae and unit-cell dimensions of 12 pure smectite samples were used as a reference in the design and evaluation of TSSA and Q s measurement techniques based on cation exchange capacity (CEC), H 2 O retention at 47% RH, and ethylene glycol monoethyl ether (EGME) retention. A thermogravimetric analysis-mass spectrometry (TGA-MS) technique was used to study the release of H 2 O from smectite on heating, and to introduce a correction for H 2 O remaining in the smectite after heating to 110ºC, because the sample weight at this temperature has been used routinely as a reference in CEC and EGME sorption measurements. A temperature of 200ºC was found to be the optimum reference for such measurements.

- by Jan Środoń
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- Geology, Density, Clay Minerals, Temperature

This study was carried out to test the feasibility of a mixture of sand, cement and clay for their permeability and compressive strength. Various samples with different mass ratios of this mixture were tested to determine their permeability and compressive strength. The best proportions of 25% sand 50% cement and 25% clay show the highest compressive strength and low permeability in comparison with the other proportions. The maximum compressive strength was for the sample that contains 25% sand and 75% cement with a value of 12.83 kN/m 2 obtained after two weeks of curing, while samples that having 25% sand, 25% clay and 50% cement showed also quite good compressive strength with values of 11.05 kN/m 2 . This composition showed a permeability value of 9.15x10 -6 cm/s. The cation exchange capacity was estimated for this mixture to be 53.1 meq/100 g. This composite has a low cost, efficient and durable.

- by Reyad Shawabkeh
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- Electronic, Compressive Strength, Heavy Metal, Cost Efficiency

Application of the methylene blue test methods in determining soil properties, including specific surface area (SSA), cation exchange capacity (CEC), swell index, and swell potential are investigated on clayey soil samples with widely different mineralogy. The results indicate that the MB methods yield accurate prediction of some soil index properties, and they are easy to apply with simple test equipment. The results also show that the testing methods can be applied for soils that have widely different mineralogy. External and internal surface areas of soils can be measured by the MB adsorption methods. Effect of particle size on the MB surface area measurement accuracy was also studied using samples passing 0.425 mm (No. 40) and 0.075 mm (No. 200) sieves. The results show that there is no significant difference in the amount of absorbed methylene blue of the soil samples passing the No. 40 and No. 200 sieves. The test results also indicate that the MB-CEC values are generally lower than those obtained by the ammonium acetate method. The correlation coefficient between the MB-CEC and NH 4 -Na results is 0.88 indicating that MB can be used effectively to measure CEC of soils. The results also show that swell index and swell potential of the soils can be estimated with MB methods accurately, economically and readily. Significant relationship is observed between the swelling potential and MBV (methylene blue value) for a wide range of soils. A new classification for swelling soils is proposed using MBV.

Surface (0-15 cm) and subsurface (30-45 cm) soil samples from under canopy, edge of canopy and away from canopy of isolated Cordia africana Lam. and Croton macrostachyus Del. trees and their leaves were examined to investigate leaf nutrient content, root biomass and the contribution of trees on farms to soil fertility parameters in Badessa area, eastern Ethiopia. Leaves of C. macrostachyus had 20% higher P and 25% lower K contents than those of C. africana. The studied species had comparable leaf N content. Both species produced shallow lateral roots that extended beyond the canopy zone. Typically, higher fine root biomass was observed in the surface soils than the subsurface soils. Both species did not affect soil organic C, pH and cation exchange capacity. Surface and subsurface soils under tree canopies had 22-26 and 12-17% higher N, respectively, than the corresponding soils away from tree canopies. Surface soil available P under tree canopies was 34-50% higher than the corresponding soil away from canopies. Available P content of subsurface soil was im-proved only under C. africana canopy. The available P of surface soil under C. macrostachyus canopy was more than double that for C. africana. Trees of both species increased underneath surface and subsurface exchangeable K by 18-46% compared with the corresponding controls. In conclusion, C. macrostachyus and C. africana trees on farms keep soil nutrient high via protection against leaching, translocation of nutrients from deeper to the surface layer and accumulation of litter, which create a temporary nutrient pool in the surface soils under their canopies.

- by Legesse Negash
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- Soil Science, Biological Sciences, Environmental Sciences, ROOT

Bentonite, which consist essentially of clay minerals belonging to the smectite group, have a wide range of chemical and industrial uses. The structure chemical composition, exchangeable-ion type and small crystal size of smectite are responsible for several properties, including a large chemically active surface area, a high cation-exchange capacity and interlamellar surface having usual hydratation characteristics. A sample collected from Zaghouan (North East Tunisia, North Africa) is studied through some physico-chemical methods. Results from X-ray diffraction, chemical analysis, infrared spectroscopy, thermogravimetric analysis (TGA) and differential thermal analysis (DTA), cation exchange capacities, specific and total surfaces, confirm the general smectite character of the sample. The adsorption capacity of this clay was tested out using three metallic ions (Pb2+, Zn2+, Ni2+). The results showed that, in all cases, adsorption can be illustrated by Freundlich or Langmuir isothe...

- by fadhila ayari
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- Clay Minerals, Infrared spectroscopy, Mathematical Sciences, North Africa

A review is given of the academic and industrial aspects of the preparation, characterization, materials properties, crystallization behavior, melt rheology, and processing of polymer/layered silicate nanocomposites. These materials are attracting considerable interest in polymer science research. Hectorite and montmorillonite are among the most commonly used smectite-type layered silicates for the preparation of nanocomposites. Smectites are a valuable mineral class for industrial applications because of their high cation exchange capacities, surface area, surface reactivity, adsorptive properties, and, in the case of hectorite, high viscosity and transparency in solution. In their pristine form they are hydrophilic in nature, and this property makes them very difficult to disperse into a polymer matrix. The most common way to remove this difficulty is to replace interlayer cations with quarternized ammonium or phosphonium cations, preferably with long alkyl chains.

- by praveen M
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- Engineering, Atomic Force Microscopy, bisphenol A, Composite Material

Selected physico-chemical and chemical characteristics of 13 coconut coir dust (mesocarp pithy tissue plus short-length ®bres) samples from Asia, America and Africa were evaluated as peat alternatives. All properties studied diered signi®cantly between and within sources, and from the control Sphagnum peat. pH of coir dust was slightly acidic, whereas salinity varied dramatically between 39 and 597 mS m À1 in the saturated media extract. The cation exchange capacity and carbon/nitrogen (C/N) ratio ranged from 31.7 to 95.4 cmol c kg À1 and from 75 to 186, respectively. Most carbon was found as lignin and cellulose. The concentrations of available nitrogen, calcium, magnesium and micro-elements were low, while those of phosphorus and potassium were remarkably high (0.28±2.81 mol m À3 and 2.97±52.66 mol m À3 for P and K, respectively). Saline ion concentrations, especially chloride and sodium, were also high. Ó

- by R. Puchades and +1
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- Soil, Sustainable agriculture, Biotechnology, Calcium

Fly ash Hydrothermal synthesis Ageing process Gismondine zeolite type Zeolite Na-P1 Cation exchange capacity Statistical design of experiments Response parameter Major and interaction effects Major and trace elements iii

- by Nicholas M Musyoka
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- Fly Ash, Cation Exchange Capacity

After Darcy proposed his law for the water flow through sands, the generalizations and vulgarizations abounded and the Darcy's proposal was intended to be applied to very different kinds of fluids and materials albeit the proposal was originally referred exclusively to the water flow through sands. And although a few authors warned that the discharge velocity versus hydraulic gradient relationship is valid only in a limited grain size range, the proposition is so general that it becomes void of meaning. In this paper we do propose that the Darcy's Law proportionality ratio is not dependent exclusively on the permeable material grain size characteristics as stated in current textbooks. In clean sands, gravels and boulders the flow occurs in closed channels and should be analyzed with current hydraulic concepts. On the other end, in fine grained materials the mineralogical characteristics of the silts and clays control the capillary water flow.

soil clays and become nonexchangeable, thus nonavailable to immediate uptake by plants (Scott and Smith,

Biochar—charcoal used to amend land and sequester carbon—is attracting considerable interest. Its distinctive physical/chemical/biological properties, including high water-holding capacity, large surface area, cation exchange capacity, elemental composition, and pore size/volume/distribution, effect its recognized impacts, especially on microbial communities. These are explored in the context of agriculture, composting, and land remediation/restoration. Considerable focus is given to mycorrhizal associations, which are central to exploitation in environmental technologies involving biochar. The characteristics of biochar, its availability for nutrient cycling, including the beneficial and potentially negative/inhibitory impacts, and the requisite multidisciplinary analysis (physicochemical, microbiological, and molecular) to study these in detail, are explored.

- by Garry Evans
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- Microbiology, Carbon Sequestration, Multidisciplinary, Pore Size

Quantitative techniques for spatial prediction in soil survey are developing apace. They generally derive from geostatistics and modern statistics. The recent developments in geostatistics are reviewed particularly with respect to non-linear methods and the use of all types of ancillary information. Additionally analysis based on non-stationarity of a variable and the use of ancillary information are demonstrated as encompassing modern regression techniques, including gener-Ž . Ž . alised linear models GLM , generalised additive models GAM , classification and regression Ž . Ž . trees RT and neural networks NN . Three resolutions of interest are discussed. Case studies are used to illustrate different pedometric techniques, and a variety of ancillary data. The case studies focus on predicting different soil properties and classifying soil in an area into soil classes defined a priori. Different techniques produced different error of interpolation. Hybrid methods such as CLORPT with geostatistics offer powerful spatial prediction methods, especially up to the catchment and regional extent. It is shown that the use of each pedometric technique depends on q .au A.B. McBratney . 0016-7061r00r$ -see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž . PII: S 0 016-7061 00 00043-4 ( ) A.B. McBratney et al.r Geoderma 97 2000 293-327 294 the purpose of the survey and the accuracy required of the final product. q

- by I. Odeh and +1
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- Cartography, Soil Science, Fuzzy Logic, Pedometrics

- by Suprakas Sinha Ray
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- Engineering, Atomic Force Microscopy, bisphenol A, Composite Material

Waste of polystyrene was converted into a cation exchange resin and was used for the removal of lead and cadmium metals from aqueous solution. Wastes consisting of coffee cups were crushed into small pieces and immersed into a solution of sulfuric acid in order to attach sulfonic group to polymer chain, these groups are responsible for the exchange properties of the modified plastic. The cation exchange capacity (CEC) was determined and was comparable to commercial exchangers. The adsorption isotherms of resin with synthetic wastewater containing lead and cadmium ions were tested. Adsorption analysis results obtained at various concentrations showed that the adsorption pattern on the resin followed Langmuir isotherms.

Parent material composition, particle disintegration by glaciers and lacustrine environment govern the geological development and engineering characteristics of clay deposits in southern Saskatchewan. The pre-existing expansive clay minerals were preserved due to the restrained leaching in the Regina Lake and the prevalent aridity in the area. The main objective of this paper was to develop a fundamental understanding of the clay deposit for the use in the design and construction of civil infrastructure. The results indicated the presence of expansive clay minerals in the deposit, with smectite accounting for 35% of the material. The major exchangeable cation was found to be Ca2+ which accounted for more than half of the total measured cation exchange capacity of 40 (cmol(+)/kg). The most likely exchange complex governing water adsorption of the clay was determined to be Ca2+-smectite. Alongside a high initial saturation (86%), this complex resulted in moderate volume changes in the clay. The swelling pressure was fully developed within the first hour of the constant volume test. The corrected swelling pressure was determined to be 120 kPa leading to an estimated heave of 36 mm in the surface layer of the deposit. The compression index and the swelling index were found to be 0.25 and 0.08, respectively.

- by Maki Ito
- •
- Civil Engineering, Geology, Mineralogy, Leaching

Adsorption of methylene blue from aqueous solutionsonto unexpanded and expanded perlite samples activatedby H2SO4 and NaCl solutions has beeninvestigated, to assess the possibility of usingperlite for removing cationic dyes from aqueoussolutions. The effects of pH and temperature of dyesolution on the adsorption capacities have beenevaluated. The experimental data were correlatedreasonably well by the Langmuir adsorption isothermand the isotherm parameters (Q m and K) have beencalculated. The removal efficiency (P) anddimensionless separation factor (R) have shown thatperlite can be used for removal of methylene blue fromaqueous solutions, but unexpanded perlite is more effective.

- by Yavuz Alkan
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- Environmental Engineering, Chemical Engineering, Civil Engineering, Thermodynamics

In this study, a three-level Box-Behnken factorial design combined with response surface methodology for modeling and optimizing of operation parameters of hydrocyclones, namely feed solid, inlet pressure, vortex diameter and apex diameter, to produce three group bentonite concentrates was developed. In order to produce bentonite concentrates, mathematical model equations were derived by computer simulation programming applying the least squares method using Minitab 15 software. Second-order response functions were produced for the cation exchange capacity (CEC), free swelling volume (FSV) and apparent viscosity (AV) of bentonite concentrates. Predicted values are in good agreement with experimental values. After hydrocyclone separation the CEC increased by 138%, the FSV by 194% and AV by 325% in the bentonites, which in their natural state are not suitable for industrial use. Additionally, this study has shown that the Box-Behnken and response surface methodology could be applied efficiently for the modeling of hydrocyclone separation of bentonite and it is an economically efficient way to obtain the maximum amount of information in a short period of time and with the minimum number of experiments.

- by Eyüp SABAH and +1
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- Engineering, Earth Sciences, Process Optimization, Response Surface Methodology

Conversion of native forest ecosystem to cropland has considerably degraded the soil nutrient levels in the Bale Mountains, south-eastern highlands of Ethiopia. This study investigated the effects of land use change through conversion of native forest to cropland and/or grazing land on soil pH (H 2 O), base cations (Ca 2+ , Mg 2+ , K + , Na + ), CEC and percentage base saturation (PBS) in three adjacent land-use types: cropland, grazing land and native forest. A total of 108 soil samples (3 replications Â 3 land-use types Â 4 profiles Â 3 soil depth layers, 0-0.2, 0.2-0.4 and 0.4-1.0 m) were collected for laboratory analyses. Results showed that soil pH, Na + and K + , CEC, and PBS varied significantly with respect to land use and soil depth while Ca 2+ and Mg 2+ varied with soil depth (r < 0.05). Conversion of native forest ecosystem to cropland during a 15-year period significantly increased soil pH and PBS while reducing Na + and K + . The CEC in the cropland was reduced by 37.7% ($2.6% per annum) compared to the native forest, which could be attributed to the decline in organic matter concentrations. If such rapid declines in soil nutrient concentrations continue unabated, the soils will reach at the point of no return within a few decades. Although the effect of grazing on most of the properties was found to be minimal, adapting the number of stock to the carrying capacity of the land and thereby enhancing the natural regeneration, combined with proper cropland management practices could help restoring soil nutrients for sustainable agricultural production and ecosystem functions. ß

- by Fantaw Yimer
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- Forestry, Sustainable agriculture, Forest Ecology And Management, Forest Ecology

Percobaan kalibrasi di lapang telah dilaksanakan di tanah Ultisol Deli Serdang, Sumatera Utara untuk mempelajari faktor-faktor tanah yang berpengaruh terhadap ketersediaan K, memilih metode ekstraksi, menentukan batas kritis, dan menghitung kebutuhan pupuk K untuk kedelai. Percobaan mengunakan rancangan acak kelompok, lima tingkat takaran K, sembilan ulangan, dan menggunakan kedelai sebagai tanaman indikator. Takaran kalium yang digunakan terdiri atas: 0, 20, 40, 80, dan 160 kg K/ha dari pupuk KCl. Hasil penelitian menunjukkan bahwa Corganik dan kapasitas tukar kation tanah merupakan faktor tanah utama yang berpengaruh terhadap ketersediaan K di tanah-tanah Ultisol. Pemupukan K nyata meningkatkan hasil biji kering kedelai di lokasi Tanjung Gusti dimana hasil tanaman meningkat dari 0.81 menjadi 1.99 t/ha akibat pemberian 80 kg K/ha atau terjadi peningkatan sekitar 146%. Pengekstrak HCl 25% ditemukan sebagai metode ekstraksi K yang sesuai untuk menduga kadar K tanah Ultisol dalam kaitannya dengan penghitungan kebutuhan pupuk K untuk kedelai. Kelas ketersediaan hara kalium tanah Ultisol untuk kedelai berdasarkan pengekstrak HCl 25% adalah rendah (< 340), sedang (340-1150) dan tinggi (>1150 ppm K 2 O). Kebutuhan pupuk untuk mencapai hasil maksimum adalah 210, 190, dan 150 kg KCl/ha, sedangkan untuk mencapai hasil optimum hanya 85, 2, dan 0 kg KCl/ha masing-masing untuk kelas K tanah rendah, sedang, dan tinggi.

- by dedy tanjung
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- Field Experiment, Potassium, Soybean, Randomized Block design
- by Tamez Uddin
- •
- Environmental Engineering, Chemical Engineering, Civil Engineering, Thermodynamics

Diffuse reflectance spectroscopy (DRS) is attracting much interest in the soil science community because it has a number of advantages over conventional methods of soil analyses. The techniques are more rapid, timely, cheaper and hence more efficient at obtaining the data when a large number of samples and analysis are required. Moreover, a single spectrum may be used to assess various physical, chemical and biological soil properties. Until now, research in soil spectroscopy has focused on spectral calibration and prediction of soil properties using multivariate statistics. In this paper we show how these predictions may be used in an inference system to predict other important and functional soil properties using pedotransfer functions (PTFs). Thus we propose the use of soil spectral calibration and its predictions as input and as a complement to a soil inference system (SPEC-SINFERS). We demonstrate the implementation of SPEC-SINFERS with two examples. As a first step, soil mid-infrared (MIR) spectra and partial least squares (PLS) regression are used to estimate soil pH, clay, silt, sand, organic carbon content and cation exchange capacity. A bootstrap method is used to determine the uncertainties of these predictions. These predictions and their uncertainties are then used as input into the inference system, where established PTFs are used to infer (i) soil water content and (ii) soil pH buffering capacity together with their uncertainties. An important feature of SPEC-SINFERS is the propagation of both input and model uncertainties.

- by Budiman Minasny
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- Soil Science, Science Communication, Multivariate Statistics, Prediction

This work describes chromatographic properties of reversed-phase/cation-exchange/anion-exchange trimodal stationary phases. These stationary phases were based on high-purity porous spherical silica particles coated with nano-polymer beads using an electrostatically driven self-assembly process. The inner-pore area of the material was modified covalently with an organic layer that provided both reversed-phase and anion-exchange properties while the outer surface was coated with nano-sized polymer beads with strong cation-exchange characteristics. This design ensured spatial separation of the anion-exchange and the cation-exchange regions, and allowed reversed-phase, anion-exchange and cation-exchange retention mechanisms to function simultaneously. Chromatographic evaluation of ions and small molecules suggested that retention of ionic analytes was influenced by the ionic strength, pH, and mobile phase organic solvent content, and governed by both ion-exchange and hydrophobic interactions. Meanwhile, neutral analytes were retained by hydrophobic interaction and was mainly affected by mobile phase organic solvent content. Depending on the specific application, selectivity could be optimized by adjusting the anion-exchange/cation-exchange capacity ratio (selectivity), which was achieved experimentally by using porous silica particles with different surface areas.

- by Christopher Pohl
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- Engineering, Technology, Self Assembly, Polymers

Belowground carbon allocation (BCA) in forests regulates soil organic matter formation and influences biotic and abiotic properties of soil such as bulk density, cation exchange capacity, and water holding capacity. On a global scale, the total quantity of carbon allocated belowground by terrestrial plants is enormous, exceeding by an order of magnitude the quantity of carbon emitted to the atmosphere through combustion of fossil fuels. Despite the importance of BCA to the functioning of plant and soil communities, as well as the global carbon budget, controls on BCA are relatively poorly understood. Consequently, our ability to predict how BCA will respond to changes in atmospheric greenhouse gases, climate, nutrient deposition, and plant community composition remains rudimentary. In this synthesis, we examine BCA from three perspectives: coarse-root standing stock, belowground net primary production (BNPP), and total belowground carbon allocation (TBCA). For each, we examine methodologies and methodological constraints, as well as constraints of terminology. We then examine available

- by Kurt Pregitzer
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- Global change, Fossil Fuels, Soil organic matter, Species Composition

This work presents an unconventional procedure for the recovery of spent Al-rich caustic soda solutions from the pickling of dies for the production of aluminium extrusions. Caustic soda was regenerated at roughly 70%, by precipitating aluminate, after addition of a silica source, in the form of zeolite A, a microporous material that is widely used in many technological sectors. It was shown that the process is reliable and can be repeated for several cycles, provided the concentration of the caustic soda solution is suitably restored. The by-product obtained, zeolite A, proved to be a high-grade material with performance as a cation exchanger and physical sorbent that is certainly comparable to that reported in literature (e.g., cation exchange capacity equal to 5.14 meq g À1 vs. 5.48 meq g À1 and water vapour adsorption capacity of 26.5% vs. 27.6% at 16 torr and 298 K). The economics of the process, although not examined yet, would appear generally favourable, considering that zeolite A is a valuable by-product which widely covers the costs for the recovery of the spent solutions. There are, therefore, significant prospects for the use of zeolite A, particularly as a builder in detergent formulation.

- by Paolo Aprea
- •
- Kinetics, Metallurgy, Environmental Management, Crystallization

The use of urban organic solid waste compost as organic fertilizer is an important alternative to solid waste management. This waste has been applied to agricultural lands because of the benefits in relation to soil chemical properties. A greenhouse experiment was conducted to investigate the effects of the application of urban waste compost, at the rate of 30 g dm

- by Takashi Muraoka and +1
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- Solid Waste Management, Magnesium, Solid waste, Potassium

Soil fertility depletion has been described as the single most important constraint to food security in West Africa. Over half of the African population is rural and directly dependent on locally grown crops. Further, 28% of the population is chronically hungry and over half of people are living on less than US$ 1 per day as a result of soil fertility depletion.

- by Joseph Kimetu
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- West Africa, Food Security, Environmental Sciences, Agricultural Systems

- by praveen m
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- Engineering, Atomic Force Microscopy, bisphenol A, Composite Material

This paper reviews the factors affecting trace metal behaviour in estuarine and riverine floodplain soils and sediments. Spatial occurrence of processes affecting metal mobility and availability in floodplains are largely determined by the topography. At the oxic-anoxic interface and in the anoxic layers of floodplain soils, especially redox-sensitive processes occur, which mainly result in the inclusion of metals in precipitates or the dissolution of metal-containing precipitates. Kinetics of these processes are of great importance for these soils as the location of the oxic-anoxic interface is subject to change due to fluctuating water table levels. Other important processes and factors affecting metal mobility in floodplain soils are adsorption/desorption processes, salinity, the presence of organic matter, sulphur and carbonates, pH and plant growth. Many authors report highly significant correlations between cation exchange capacity, clay or organic matter contents and metal contents in floodplain soils. Iron and manganese (hydr)oxides were found to be the main carriers for Cd, Zn and Ni under oxic conditions, whereas the organic fraction was most important for Cu.

- by Filip M G Tack
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- Kinetics, Trace Metals, Multidisciplinary, Plant growth