title: Adsorption of chlorpyrifos, penconazole and metalaxyl from aqueous solution by modified clays.
abstract: Sorption of three pesticides (chlorpyrifos, metalaxyl and penconazole) has been measured on a commercial clay montmorillonite and on the same mineral modified with either of two cationic-surfactant micelles. Both micelle-clay complexes, commercial names Cloisite 20A and Cloisite 30B, showed a good capacity to sorb all three pesticides from water, whereas their sorption on the natural montmorillonite was not described by an isotherm. Modelling sorption on both micelle-clay complexes showed that the Freundlich sorption constant (K(F)) was higher for chlorpyrifos on Cloisite 20A (K(F) = 7.76) than on Cloisite 30B (K(F) = 5.91), whereas the sorption of metalaxyl was stronger on Cloisite 30B (K(F) = 1.07) than on Cloisite 20A (K(F) = 0.57). Moreover the micelle-clay complex Cloisite 20A also showed a good affinity for penconazole, the maximum quantity adsorbed (q(m)) of 6.33 mg g(-1) being 45% more than that on Cloisite 30B. Single-batch adsorption of each pesticide onto both micelle-clay complexes was studied using the Freundlich isotherm for chlorpyrifos and metalaxyl and the Langmuir isotherm for penconazole. The Cloisite 20A micelle-clay complex was predicted to require 23% less adsorbent to treat certain volumes of wastewater containing 30 mg L(-1) chlorpyrifos, 43% more to treat metalaxyl similarly and 57% less to treat penconazole compared with Cloisite 30B.
authors.affiliation: Istituto di Chimica Agraria ed Ambientale, Universita Cattolica del Sacro Cuore, Piacenza, Italy. nicoleta.suciu@unicatt.it
authors.forename: Nicoleta A
authors.initials: NA
authors.lastname: Suciu
authors.forename: Ettore
authors.initials: E
authors.lastname: Capri
mesh_terms: D000327:Adsorption; D000409:Alanine / Q000031:analogs & derivatives / Q000737:chemistry; D000538:Aluminum Silicates / Q000737:chemistry*; D001546:Bentonite / Q000737:chemistry*; D002412:Cations; D004390:Chlorpyrifos / Q000737:chemistry; D000077215:Clay; D007700:Kinetics; D008823:Micelles; D010575:Pesticides / Q000737:chemistry / Q000302:isolation & purification*; D012996:Solutions / Q000737:chemistry; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*; D013816:Thermodynamics; D014230:Triazoles / Q000737:chemistry; D014865:Waste Disposal, Fluid / Q000379:methods*; D014867:Water / Q000737:chemistry*
chemical_list: D000538:Aluminum Silicates; D002412:Cations; D008823:Micelles; D010575:Pesticides; D012996:Solutions; D013501:Surface-Active Agents; D014230:Triazoles; D014867:Water; D001546:Bentonite; C028175:metalaxyl; C087058:penconazole; D004390:Chlorpyrifos; D000409:Alanine; D000077215:Clay