Silver-complexed chitosan microparticles for pesticide removal

Two types of chitosan microparticles (CMs) and their silver-complexes CMs ( SCMs) were prepared using different crosslinking agents, i.e. glutaraldehyd e and epichlorohydrin, in order to investigate the adsorption and release b ehaviors of a typical pesticide, methyl parathion (MP). The pH and concentr ation dependencies on Ag(I) and MP adsorptions on both the CMs and SCMs wer e studied. The epichlorohydrin-crosslinked CM apparently showed the superio rity of Ag(I) adsorption over the glutaraldehyde-crosslinked CM, neverthele ss, adsorption behavior of MP on SCM derived from each CM was observed vice versa. Release behavior of MP from the MP-loaded SCMs was also observed in aqueous acetic acid and sodium acetate buffer solutions at low pH as well as in those containing two kinds of ammonium reagents. The aqueous solution s containing ammonium thiocyanide and ammonia could be applied for MP relea se from the MP-loaded SCMs without Ag(I) leakage from the particles. Furthe rmore, from the iteration of adsorption and release experiments of MP, glut araldehyde-crosslinked SCM provides good reusability for MP removal. (C) 20 00 Elsevier Science BN. All rights reserved.