Abstract:

The adsorption properties of self-made wood flour/chitosan graft acrylic acid-acrylamide copolymerization resin(adsorbing resin R)are discussed under different adsorption conditions. The optimum using conditions of the adsorbing resin R in the Pb²⁺ solutions are 30℃, pH=6.0, resin usage 0.2 g·L^-1, the initial concentration of Pb²⁺ 0.75 mmol·L^-1, the adsorbing time 8 h(static)or 6 h(dynamic). Under the above-mentioned conditions, the adsorption capacity of Pb²⁺ for the adsorbing resin R is 2.52 mmol ·g^-1 and its removing percent of Pb²⁺ is 97.1%. The adsorption capacities of the adsorbing resin R obviously reduced while NaCl, NaNO₃ or urea is added in the Pb²⁺ ion solutions, the decreasing rate is the fastest when NaNO₃ is adding in the Pb²⁺ solution and it is the slowest when urea is added in the Pb²⁺ solution. The repeated using property of the adsorbing resin R is better. The adsorption mechanism is explored by the adsorption isotherm, the adsorption kinetics and thermodynamics, and the change of the surface morphology, etc. The surface morphology and the grain distribution of the adsorbing resin R before adsorbing Pb²⁺ is uneven. And the grain structure of the surface before adsorbing Pb²⁺ is disrupted and the "white" spots obviously increased and gradually changed uniform when the adsorbing time increased. The Pb²⁺ adsorption process for the adsorbing resin R is fit for pseudo-first kinetic model, and ΔG is negative, and ΔS and ΔH is positive, that is, the adsorption process is spontaneous and the increasing temperature is favorable for the Pb²⁺ adsorption onto the adsorbing resin R.

Key words: chitosan, adsorbing resin, wood flour, acrylic acid, acrylamide, graft copolymerization, adsorption mechanism