Covalent attachment of phenyl and carboxyphenyl layers derived from diazonium salts onto activated charcoal for the adsorption of pesticides

Abstract

The past and recent uncontrolled use of organochlorine pesticides imposes serious problems due to their adverse undesired effects in ecosystems. Finding new ways to dispose of these molecules is therefore mandatory. The covalent modification of activated charcoal powder (ACP) by substituted aryl groups can be achieved by reaction with aryl radicals obtained through the sonically induced dediazonation of diazonium salts. Seventeen organochlorine pesticides were adsorbed on ACP covalently grafted with phenyl and carboxyphenyl layers. The sorption percentages of the pesticides onto the carboxyphenyl modified ACPs [measured by GC-ECD (Gas Chromatography – Electron Capture Detector)] were in the range of 90–100% (DDT, δ-HCH, γ-HCH and endrin aldehyde), 80–90% (methoxychlor, endosulfan II, p,p-DDD and β-HCH) and 60–80% (α-HCH, DDE, endosulfansulfate, endrin, endosulfan I, aldrin, heptachlorepoxid, dieldrin and heptachlor). A tentative explanation is given for these differences based on steric effects.