Preparation and heavy metal ions biosorption of graft copolymers from enzymatic hydrolysis lignin and amino acids

Novel biosorbents, graft copolymers, were prepared via Mannich reaction from enzymatic hydrolysis lignin with glycine and cystine, respectively. The element content, FT-IR and fluorescence spectra, relative viscosity, and particle size of the copolymers were systematically investigated. Furthermore, effects of initial pH, ionic strength, temperature, contact time and initial metal ion concentration on the biosorption capacities of Cu(II) and Co(II) ions onto the copolymers were studied using batch sorption technique. It was found that the copolymers exhibited excellent biosorption characteristics for Cu(II) and Co(II) ions. The sorption kinetic data can be described well with a pseudo-second-order model, and the equilibrium data can be fitted well to the Langmuir and Freundlich isotherm for Cu(II) and Co(II) biosorption process, respectively. Surface complexation and ion-exchange modeling were performed to elucidate the biosorption mechanism involved because surfaces of the copolymers contained three main types of acid/base sites from the amino acid grafted copolymer units.