Chitosan/PVA silver nanocomposite for butachlor removal: Fabrication, characterization, adsorption mechanism and isotherms.

Silver nanoparticle (AgNP) incorporated chitosan-Polyvinyl alcohol (Ch/PVA) hydrogel nanocomposite was fabricated by repeated freeze-thaw treatment using glutaraldehyde as crosslinker for removal of herbicide butachlor from aqueous solution. Ch/PVA hydrogel provided a matrix for in-situ immobilization of AgNPs and were characterized by various physicochemical techniques. AgNPs of size 5-20 nm possessed crystalline structure, led to increase in thermal stability and surface area after incorporation into Ch/PVA hydrogel. Ch/PVA hydrogel nanocomposite showed maximum adsorption of butachlor (86.55 %) at 30 °C and pH 3.0, while Ch/PVA-Ag showed a slight increase in adsorption of butachlor following pseudo-second order kinetics. Langmuir and Freundlich models with different error functions (R2, R2adj, RSME, χ2 and RSS), confirmed monolayer adsorption of butachlor.