Organically Modified Clays (original) (raw)

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.

The use of modified clay materials for the sorption of various industrial pollutants

2011

The Authors dealt with the use of modifi ed clay materials for the removal of dangerous industrial pollutants. Three modifi cation methods (namely modifi cation by Keggin's polycation, modifi cation by means of humic substances and pillarization at 450 °C) were applied for the creation of modifi ed materials. Clay materials modifi ed by humic substances were used for the sorption of Cr(VI) from aqueous medium in the form of dichromates. Other ways of modifi cation and their combinations were used for the preparation of the sorbents of dangerous gaseous pollutants (toluene, xylene). It was discovered that some modifi ed clay materials sorb the gaseous pollutants twice as much as common sorbent (activated carbon).

Sorption study of organic contaminant on raw and modified clay materials

MATEC Web of Conferences, 2013

The adsorption of volatile organic compound VOC (o-xylene) was studied by a static headspace coupled to gas chromatography in natural and intercalated clay. Vapor-solid adsorption isotherms of o-xylene were measured at 20 • C, 30 • C and 40 • C. Clay was modified with hexadecyl trimetyl ammonium bromide (HDTMA). Absolute values of the amounts of o-xylene adsorbed in intercalated clay were about eighteen times higher than natural clay. The adsorption isotherm were analysed with Langmuir, Freundlich, Langmuir-Freundlich and Toth models. Langmuir-Freundlich model describes well the equilibrium adsorption data. The evaluation of thermodynamic parameters presents an exothermic and spontaneous adsorption process.

The use of clays to sequestrate organic pollutants. Leaching experiments

Chemosphere, 2008

Leaching experiments are performed from clay-pollutant systems in order to evaluate the capability of clays to sequestrate organic pollutants from wastewaters. Reference kaolinite KGa-1b, montmorrillonite SWy-2 and reference soil BCR Ò -700 are the sorbent materials. 2,4,6-trichloroaniline (2,4,6-TCA) and 4chlorophenol (4-CP) are the typical pollutants, sorbed at amounts of 10.0 mg g À1 and 5.8 mg g À1 on SWy-2 and 7.3 mg g À1 and 2.2 mg g À1 on KGa-1b, respectively.

Organically Modified Clay for Adsorption of Petroleum Hydrocarbon

European Chemical Bulletin, 2015

Organically modified clay mineral was prepared by exchanging hexadecyl trimethyl ammonium bromide (HDTMA) onto kaolinite clay mineral. The prepared organoclay was characterized using FTIR, XRD and TGA for assigning the surface groups, layer spacing and thermal stability. The adsorption efficiency of the produced organoclay towards hydrocarbons that likely to be present in oily wastewaters and oil spills (gasoline and kerosene) was studied. Different process parameters as contact time, adsorbent dose and HDTMA concentration were studied. The obtained results clarified that the adsorption capacity of the prepared organoclay was potentially enhanced than that of unmodified clay. The batch adsorption capacity was found to be more than 5g/g and 7g/g with respect to kerosene and gasoline, respectively after 24h of contact.

Analytical Method for the Sorption of Hydrophobic Organic Pollutants in Clay-Rich Materials

Environmental Science & Technology, 1995

MODIFIED CLAY AS SOIL AMENDMENT FOR REMEDIATION: STUDIES OF LEACHING AND SORPTION KINETICS

Soil contamination with metals and metalloids is serious environmental problem nowadays, caused mainly by intensive anthropogenic activities such as industry, traffic or mining. Soil remediation regarding metals and metalloids in polluted sites includes methodologies based on chemical precipitation, ion exchange, carbon adsorption, membrane filtration, adsorption and co-precipitation. Soil amendments that affect metal immobilization can be used for remediation of soil. Use of clay, natural (raw) or modified, as a soil amendment is one of the most perspective soil remediation methodologies due to the efficiency and cost effectiveness. Clay consists of crystalline-hydrated aluminosilicates and it has high exchange capacity that is important property for the process of binding of metals and metalloids. Efficiency of clay as an immobilization agent for metal binding was tested by sorption and batch leaching tests. Sorption capacity for raw and modified clay samples was experimentally tested under various pH and temperature conditions. Samples of modified clay as a sorbent were tested for sorption of Pb as monocontaminant and at complex contamination of metals. Clay modification was done by using Ca and Na salts, HNO3 (protonated forms), Fe-oxyhydroxide, hydroxyapatite. Higher sorption capacity was observed for clay modified with hydroxyapatite and Ca salts. Sorption capacity increased with a rise of temperature at the optimum pH 5.0-5.5. Immobilization of metals with cheap soil amendments such as clay in situ is effective method for reduction of environmental hazards with low and medium target concentrations of metals or metalloids at relatively stable environment. Increased efficiency can be reached by using clay modified with hydroxyapatite as soil amendment. Keywords: modified clay, soil amendments, soil remediation, sorption kinetics

The Use of Modified Bentonite for Removal of Aromatic Organics from Contaminated Soil* 1

Journal of colloid and interface …, 1997

and Reliability Act (CERCLA). The aromatic fraction of This study investigates the clay-aromatic interactions with a gasoline's hazardous constituents includes benzene, toluene, view to the use of bentonite clay for binding benzene, toluene, ethylbenzene, and xylene (commonly called the BTEX comethylbenzene, and o-xylene (BTEX compounds) in contaminated pounds). soils. BTEX compounds are the most toxic aromatic constituents Today, several options such as chemical degradation, soil of gasoline present in many underground storage tanks. Modified flushing, thermal treatment, soil vapor extraction, and bio-(organophilic) and ordinary bentonites are used to remove these degradation are available to treat aromatic wastes and the organics. The organophilic bentonites are prepared by replacing matrices they contaminate, particularly soils (3). The applithe exchangeable inorganic cations present in bentonite particles cation of these techniques entails high costs. In addition, the with a quaternary ammonium salt. Various clay-to-soil ratios were applied to determine the efficiency of the modified bentonite in present methods of disposing of these wastes (i.e., placement enhancing the cement-based solidification/stabilization (S/S) of in drums for burial, pooling for evaporation, and storage in BTEX contaminated soils. Toxicity characteristics leaching procelined disposal sites) are not reliable and do not provide a dure (TCLP) tests were performed on soil samples to evaluate the permanent solution for containment. It is essential that a leaching of the organics. In addition, X-ray diffraction analyses safe and cost-effective cleanup process be developed as an were conducted to assess the changes in the basal spacing of the alternative to the current treatment and disposal practices. clays as a result of their interaction with BTEX compounds. The One such treatment process could be developed using findings of this study reveal that organophilic bentonite can act modified (organophilic) clays to adsorb aromatic comas a successful adsorbent for removing the aromatic organics from pounds from contaminated soils and prevent them from polcontaminated soil. Thus, this material is viable for enhancing the luting the groundwater. Research conducted (4-6) on the performance of cement-based S/S processes, as an adsorbent for adsorption of organics by clays indicates that quaternary petroleum spills, and for landfill liners and slurry walls. ᭧ 1997 Academic Press ammonium cations such as hexadecyltrimethylammonium Key Words: bentonite; aromatic compounds (BTEX); organo-(HDTMA) interact with clays and replace the exchangeable philic clay; cement-based solidification/stabilization (S/S) proinorganic cations on their surfaces, forming a stationary cess; basal spacing; XRD analysis. phase in the clay particles. In addition, as a result of the larger size of the HDTMA cations compared with that of the replaced cations, the interlamellar distance (basal spac-191

Asemi-Empirical Study of the Adsorption of Some Organic Pollutants on Modified Iraqi Clays

Baghdad Science Journal, 2016

In this work semi–empirical method (PM3) calculations are carried out by (MOPAC) computational packages have been employed to calculate the molecular orbital's energies for some organic pollutants. The long– chain quaternary ammonium cations called Iraqi Clays (Bentonite – modified) are used to remove these organic pollutants from water, by adding a small cationic surfactant so as to result in floes which are agglomerates of organobentonite to remove organic pollutants. This calculation which suggests the best surface active material, can be used to modify the adsorption efficiency of aniline , phenol, phenol deriviatives, Tri methyl glycine, ester and pecticides , on Iraqi Clay (bentonite) by comparing the theoretical results with experimental results achived in previous experimental studies between some organic pollutants and modified bentonite by (1- Hexadecyl pyridinium bromide) (HDPYBr). The theoretical calculation is made by using three surface active materials [1- (Hexade...

Organically Modified Clays (original) (raw)

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