Cadmium Sorption by Some Alkaline Soils of North-West India (original) (raw)
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Thermodynamics of Cadmium Sorption on Different Soils of West Bengal, India
The Scientific World Journal, 2014
A sorption study was conducted on different soils collected from five agroecological zones of West Bengal, India, to understand the soil environmental behavior and fate of cadmium. For this purpose batch adsorption experiments were carried out at the native soil pH and at three different temperatures (25 ∘ C, 35 ∘ C, and 45 ∘ C). The adsorption data fitted by a linear least squares technique to the different sorption isotherms. Most data obtained give the good fit to both Freundlich and modified Langmuir isotherms, but they are not consistent with the linear Langmuir adsorption model. Thermodynamic parameters, namely, thermodynamics equilibrium constant at a particular temperature ( 0 ), Gibbs free energy at a particular temperature (Δ 0 ), and change of enthalpy (Δ 0 ) and change of entropy at temperature (Δ 0 ), were also determined by applying sorption value and concentrations of Cd in equilibrium solution within the temperature range. The thermodynamic parameters revealed that Cd sorption increases as the values of 0 , Δ 0 , Δ 0 , and Δ 0 were increased on reaction temperatures. The spontaneous sorption reaction can be concluded due to high values of Δ 0 . The positive values of Δ 0 indicated that the Cd sorption is an endothermic one. Under these present conditions, the soil and its components possibly supply a number of sites having different adsorption energies for cadmium sorption.
Adsorption of cadmium on two different soils from Egypt (clays and sandy loam soils) was studied. Data on adsorption isotherms, competitive effects and/or inorganic complex formation of NaCl and Na 2 SO 4 are presented. The adsorption was described by a Langmuir or a Frendlich equation. The maximum adsorption derived from the Langmuir equation was taken to measure the adsorption capacity, while the Langmuir parameter was taken to point out the relative degree of affinity or energy at different cadmium adsorption conditions. In particular, the clay soil had higher adsorption capacities in all cases than the sandy loam soil. The higher clay content, CEC, OM and the surface area of the clay soil may account for the higher capacity. It appears likely that the existence of NaCl decreases the maximum adsorption of cad-mium in both soils and also reduces the bonding energy coefficients less than those in presence of Na 2 SO 4 apparently favoring the dissociation of adsorbed Cd complex. Due...
Sorption of cadmium in some arable and forest soils
Journal of Radioanalytical and Nuclear Chemistry, 2000
The behavior of cadmium labeled with 109 Cd in different depth horizons of arable and forest soils were studied under static (batch) conditions in three interconnected processes, which consist of sorption, desorption and extraction. In the sorption, Cd 2+ was applied in the aqueous calcium nitrate solution. Both untreated soils and peroxide treated soils were used in order to remove organic matter from some of the soil samples used in parallel. The influence of the V/m ratio on the sorption coefficients was investigated in preliminary experiments with untreated soils. Contrary to the usually short-term sorption, a long-term sorption of cadmium was investigated in untreated and treated soil horizons, which lasted more than fortnight. Kinetic studies of sorption were carried out and cadmium concentration dependence in aqueous phase of the second order kinetic constants was observed. For evaluation of sorption and desorption processes Freundlich isotherms were used. It was found that the Freundlich adsorption intensity coefficient is more time dependent than the absorption capacity coefficient, and the sorption itself consists of rapid and slow processes according to the soil constituents. Desorption and extraction processes revealed the possibility of cadmium recovery from various soil horizons. Based on the obtained results two-or three-stage theory of cadmium retention in soils was proposed. Some new insight into the role of organic matter in the sorption/desorption process of cadmium is also presented.
Sorption of Cadmium in Some Soil Amendments for In Situ Recovery of Contaminated Soils
Although Cd concentrations in uncontaminated soils are usually low, pollution of soils by Cd from different sources of contamination pose problems. The application of soil amendments to increase plant production has been used as a viable alternative for recovery of soils contaminated with Cd. However, emphasis needs to be placed on the nature of Cd sorption processes in order that the amendments can be managed appropriately. A range of materials including vermicompost, sugarcane filter cake, palm kernel pie, lime, phosphate rock, and zeolite were used for the sorption studies. Total and nonspecific Cd sorption was estimated by batch experiments, and specific sorption was obtained by the difference between the former and the latter. Best adsorbents for specific Cd sorption from soil amendments were lime and zeolite. Langmuir adsorption isotherms fitted reasonably well in the experimental data, and their constants were evaluated, with R 2 values from 0.80 to 0.99. The maximum adsorption capacity of Cd(II) was higher for mineral amendments than for organic amendments and ranged from 0.89 to 10.86 gkg −1 . The small value (0.08 Lmg −1 ) of the constant related to the energy of adsorption indicated that Cd was bound weakly to the palm kernel pie. Thermodynamic parameter, the Gibbs free energy, was calculated for each system, and the negative values obtained confirm that the adsorption processes were spontaneous. The values of separation factor, R L , which has been used to predict affinity between adsorbate and adsorbent were between 0 and 1, indicating that sorption was very favorable for Cd(II).
THERMODYNAMIC STUDY OF Cd (II) SORPTION ON SOIL
revagrois.ro
Sorption is a major process responsible for the fate of heavy metals in soils, since the mobility of heavy metals is directly related to their partitioning between the soil solid phase and soil solution. Among the heavy metals cadmium is one of the most toxic with adverse health effects. The objective of this study is to analyze the sorption of Cd(II) from aqueous solution on soil from the industrial area of the city of Iasi (Romania) as a function of temperature at natural pH of the solution using a batch technique. A maximum uptake of about 9.7 mg of cadmium per g of soil and aprox. 95 % removal of metal was observed at 20 g/L soil amount, 200 mg/L cadmium solution and 41 °C, with an equilibrium time of 24 hours. Sorption isotherm of Cd(II) on soil were represented by Freundlich and Dubinin-Radushkevich models and the parameters indicated that the sorption of Cd(II) increased with increasing temperature of the system. Enthalpy (ΔH 0 ), entropy (ΔS 0 ) and Gibbs free energy (ΔG 0 ) were calculated from the temperature dependent sorption data, and the results indicated that the sorption of Cd(II) on soil is a spontaneous, feasible and endothermic process.
Adsorption behavior and mechanism of Cd(II) on loess soil from China
Journal of Hazardous Materials, 2009
Cadmium is a toxic heavy metal that has caused serious public health problems. It is necessary to find a cost effective method to deal with wastewater containing Cd(II). Loess soils in China have proven to be a potential adsorbent for Cd(II) removal from wastewater. The adsorption capacity of loess towards Cd(II) has been determined to be about 9.37 mg g −1 . Slurry concentration, initial solution pH, reaction time and temperature have also been found to significantly influence the efficiency of Cd(II) removal. The adsorption isotherms and kinetics of loess soil from China can be best-fit with the Langmuir model and pseudo-second order kinetics model, respectively. The thermodynamic analysis revealed that the adsorption process was spontaneous, endothermic and the system disorder increased with duration. The natural organic matter in loess soil is mainly responsible for Cd(II) removal at pH < 4.2, while clay minerals contribute to a further gradual adsorption process. Chemical precipitation dominates the adsorption stage at pH > 8.97. Further studies using X-ray diffraction, Fourier transform infrared spectra of Cd(II) laden loess soil and Cd(II) species distribution have confirmed the adsorption mechanism.
Cadmium desorption behaviour in selected sub-tropical soils: Effects of soil properties
Journal of Geochemical Exploration, 2014
To predict the environmental fate and mobility of contaminants, it is critical to study desorption behaviour of contaminants in soil system. Cadmium (Cd) desorption kinetics studies were conducted in ten sub-tropical soils of the northern part of Iran, with a wide range of physico-chemical properties. Treatments consisted of two levels of cadmium (15 and 30 mg kg −1 as CdCl 2 ). Soils were incubated at 20% moisture (w/w) level and 25 ± 1 ºC. After weeks, cadmium desorption pattern was investigated by Diethylene Triamine Pentaacetic Acid (DTPA) extraction with equilibration periods from 30 to 960 min. Results showed that two constant rate, parabolic diffusion and simple Elovich equations best described Cd desorption in these soils. The coefficients of kinetic equations had significant correlation with each other. The findings of this investigation indicated that pH, cation exchange capacity, organic matter, and oxalate extractable Fe are the most important soil characteristics in controlling Cd desorption behaviour in sub-tropical soils.
European Journal of Soil Science, 1999
Solution cadmium (Cd) concentrations and sorption and desorption of native and added Cd were studied in a range of New Zealand soils. The concentration of Cd in solution and the concentrations and patterns of native soil Cd desorbed and added Cd sorbed and desorbed varied greatly between the 29 soils studied. Correlation analysis revealed that pH was the most dominant soil variable affecting solution Cd concentration and sorption and desorption of native and added Cd in these soils. However, organic matter, cation exchange capacity (CEC) and total soil Cd were also found to be important. Multiple regression analysis showed that the log concentration of Cd in solution was strongly related to soil pH, organic matter and total Cd, which in combination explained 76% of the variation between soils. When data from the present study were combined into a single multiple regression with soil data from a previously published study, the equation generated could explain 81% of the variation in log Cd solution concentration. This reinforces the importance of pH, organic matter and total Cd in controlling solution Cd concentrations. Simple linear regression analysis could at best explain 53% of the total variation in Cd sorption or desorption for the soils studied. Multiple regression analysis showed that native Cd desorption was related to pH, organic matter and total Cd, which in combination explained 85% of the variation between soils. For sorption of Cd (from 2 mg Cd g ±1 soil added), pH and organic matter in combination explained 75% of the variation between soils. However, for added Cd desorption (%), pH and CEC explained 77%. It is clear that the combined effects of a range of soil properties control the concentration of Cd in solution, and of sorption and desorption of Cd in soils. The fraction of potentially desorbable added Cd in soils could also be predicted from a soil's K d value. This could have value for assessing both the mobility of Cd in soil and its likely availability to plants.
Sorption characteristics of lead and cadmium in some soils of India
Geoderma, 2003
To evaluate the sorption mechanism of heavy metals viz. cadmium (Cd) and lead (Pb) in major soil types, an experiment was conducted on Vertic Ustochrept, Typic Eutrochrept, Typic Ustipsamment, Typic Haplustalf and Typic Ustorthent representing five agroecological zones (AEZ) of India. The thermodynamic parameters viz. Kj, DGj, DHj and DSj were determined by using sorption data and concentrations of Cd and Pb in equilibrium solution at two different temperatures 25 F 2 and 45 F 2 jC of soil suspension. Results showed that the data of heavy metals sorption could be described satisfactorily by Freundlich and modified (two surfaces) Langmuir isotherms. The Pb sorption was maximum in the order of Vertic Ustochrept>Typic Eutrochrept>-Typic Ustochrept>Typic Haplustalf>Typic Ustorthent. The magnitude of Cd sorption was 4 to 6 times less than that of Pb. The Vertic Ustochrept sorbed Cd 4.0 and 2.5 times and Pb by 2.0 and 1.9 times more than that of Ustorthent and Haplustalf soils, respectively. Such variations in Cd and Pb sorption maxima were correlated with the differences in pH, CEC and organic matter content of the soils. Thermodynamic parameters revealed that heavy metal sorption increased as the value of Kj, DGj, DHj and DSj increased with temperature. The high values of DGj both for Pb and Cd indicated that both the reactions are spontaneous. The values of DHj were found to be negative for Cd and positive for Pb concluded that Cd sorption reaction was exothermic while Pb sorption was found to be an endothermic reaction in all the soils. D