Physicochemical study of novel organoclays as heavy metal ion adsorbents for environmental remediation (original) (raw)
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Clay Soil Modification Techniques for the Adsorption of Heavy Metals in Aqueous Medium: A Review
INTRODUCTION Variety of clays and clay minerals play an important role in the environment and used as an effective adsorbent material for the removal of toxic metal ions from water solution (Crini, 2010). The use of clays as adsorbent have advantages upon many other commercially available adsorbents in terms of low-cost, an abundant availability, high specific surface area, excellent adsorption properties, nontoxic nature, and large potential for ion exchange (
Adsorption of heavy metals on Na-montmorillonite. Effect of pH and organic substances
Water Research, 2003
Clays (especially montmorillonite and bentonite) are widely used as barriers in landfills to prevent contamination of subsoil and groundwater by leachates containing heavy metals. For this reason it is important to study the adsorption of metals by these clays. The sorption of seven metals (Cd, Cr, Cu, Mn, Ni, Pb and Zn) on Na-montmorillonite was studied as a function of pH and in the presence of ligands, forming complexes of different stabilities with the metals of interest. The continuous column method was used as it better simulates natural conditions. The total capacity of Na-montmorillonite towards these metals was determined. The pH variations influence to a higher extent the concentrations of Cu, Pb and Cd in the effluent. Moreover the results suggest that complex formation hinders the sorption of the metals on the clay, with an increasing influence in the order: Mn ⩽ Pb ⩽ Cd ⩽ Zn < Ni < Cu < Cr. The evaluation of the total capacity of Na-montmorillonite shows that this clay is a good sorbent towards all examined metals.
Talanta, 2006
In this work, a hydrophilic clay, Na-montmorillonite from Wyoming, USA, was rendered organophilic by exchanging the inorganic interlayer cations for hexadecyltrimethylammonium ions (HDTA), with the formulae of [(CH 3) 3 N(C 16 H 33)] + ion. Based on fact that organo-clay has high affinities for non-ionic organic molecules, 1,3,4-thiadiazole-2,5-dithiol was loaded on the HDTA-montmorillonite surface, resulting in the 1,3,4-thiadiazole-2,5-dithiol-HDTA-montmorillonite complex (TDD-organo-clay). The following properties of TDD-organo-clay are discussed: selective adsorption of heavy metal ions measured by batch and chromatographic column techniques, and utilization as preconcentration agent in a chemically modified carbon paste electrode (CMCPE) for determination of mercury(II). The main point of this paper is the construction of a selective sensor, a carbon paste electrode modified with TDD-organo-clay, its properties and its application to the determination of mercury(II) ions, as this element belongs to the most toxic metals. The chemical selectivity of this functional group and the selectivity of voltammetry were combined for preconcentration and determination.
Clays in the removal of heavy metals
A review paper discussing the applicability of clays to the removal of heavy metals from solution and the usefulness of such applications in environmental management and sustainable industrial practices. Clays are those aluminosilicate minerals which make up the colloid fraction (<2μm) of soils and act as natural scavengers for heavy metal ions. The mechanism of adsorption is seen to be the primary method applicable to the removal of heavy metal ions. Their tetrahedral and octahedral layers are seen to incorporate different ions which develop a range of properties with differing responses to experimental conditions such as contact time, temperature, pH, concentration of adsorbent, concentration of adsorbate etc. Numerous case studies of published work relating to heavy metal removal using clays are presented. Those heavy metals targeted are Zn, Cr, Co, Cu, Pb, Ma, Ni, and Cd due to their abundance in natural systems following anthropogenic and natural inputs. Clays are seen to be an effective alternative to the widely used activated carbon in the removal of metal ions from solution and should be used in order to improve cost control and reduce waste given sufficient performance when compared to alternatives.
A review on the application of clay minerals as heavy metal adsorbents for remediation purposes
Environmental Technology & Innovation, 2020
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Treated Clay Mineral as Adsorbent for the Removal of Heavy Metals from Aqueous Solution
Applied Science and Engineering Progress, 2021
The decontamination of heavy metals present in aquatic bodies is a significant challenge that requires urgent attention. Analytical methods such as BET, XRF, SEM-EDX, and XRD was employed to characterize the raw clay (NT) and acid treated clay (AT). The adsorption of Cr (VI) and Fe (III) onto AT was performed using the batch method. The effects of time, adsorbent dose, temperature, and pH show that the optimal conditions are 50 min, 0.3 g, 35°C, and pH 6. The surface area of AT was 389.37 m2/g, and the adsorption equilibrium time of AT was 50 min. Langmuir isotherms had the best fit. Adsorption capacity is 18.15 and 39.80 mg/g for Cr (VI) and Fe (III) ions, respectively. An increase in area considerably improved the adsorption capacity of AT in the surface specific area. The interaction of Cr (VI) and Fe (III) ions onto AT indicated spontaneous and endothermic reaction. The chromium (VI) kinetic constant (k2 = 1.679) was faster compared to Fe (III) rate constant (k2 = 0.0526). It ag...
Sorption of Heavy Metal on Natural Clay
Revista de Chimie
Sorption of heavy metals on Na-montmorillonite was studied as a function of solution pH and different concentrations of background electrolyte and also a function of added metal ion at constant pH. Equilibrium isotherms have been measured and analyzed using a Langmuir isotherm model. The metal ions were predominantly adsorbed on the permanent charge sites in a easily replaceable state. There was also evident a substantial involvement of the hydroxyl groups on the edges of Na-montmorillonite in specific adsorption of the cations especially at higher pH.
Competitive Removal of Heavy Metals from Aqueous Solutions by Montmorillonitic and Calcareous Clays
Water Air and Soil Pollution
A batch sorption method was used to study the removal of few toxic metals onto the Late Cretaceous clays of Aleg formation (Coniacian–Lower Campanian system), Tunisia, in single, binary and multi-component systems. The collected clay samples were used as adsorbents for the removal of Pb(II), Cd(II), Cu(II) and Zn(II) from aqueous solutions. Results show that the natural clay samples were mainly composed of silica, alumina, iron and magnesium oxides. N2-adsorption measurements indicated mesoporous materials with modest specific surface area of <71 m2/g. Carbonate minerals were the most influencing parameters for heavy metal removal by natural clays in both single and multi-element systems. The affinity sequence was Pb(II)>Cu(II)>Zn(II)>Cd(II) due to the variable physical properties of the studied metals. The maximum adsorption capacity reached 131.58 mg/g in single systems, but decreased to <50.10 mg/g in mixed systems. In single, binary and muti-element systems, the studied clay samples removed substantial amounts of heavy metals, showing better effectiveness than the relevant previous studies. These results suggest that the studied clay samples of the Late Cretaceous clays from Tunisia can be effectively used as natural adsorbents for the removal of toxic heavy metals in aqueous systems.
Adsorption of organic pollutants by natural and modified clays: A comprehensive review
Separation and Purification Technology, 2019
Adsorption process has been widely used for treatment of wastewaters due to its simplicity and lower costs as compared to other traditional technologies. Among the alternative sorbent materials, the use of abundantly available clays for adsorption of organic pollutants has garnered increasing attention worldwide. Clays, in its natural and modified forms, have been extensively employed for the removal of organic contaminants from different wastewaters. The current review appraises the sorption performance of natural and modified clays for environmental remediation applications. The adsorption capacity of phenolic compounds, aromatic compounds, pesticides and herbicides, and other organic contaminants are comprehensively reviewed. The effect of the experimental conditions (pH, initial concentration (C o), surfactant loading, etc.) on the adsorption capacity is also appraised. Furthermore, the adsorption mechanisms, structures, and adsorptive characteristics of natural and modified clay sorbents are included. A statistical analysis of the adsorption isotherms reveals that Langmuir and Freundlich are the most examined models in fitting the experimental adsorption data. In addition, the adsorption kinetics is predominantly based on the pseudo-second-order model. The current review is an attempt to draw a prior knowledge about the technical viability of clay sorption process by assessing outcomes of the studies published between 2000 and 2018.