Preparation and ammonium adsorption behavior of interpenetrating polymer networks hydrogel of chitosan‐g‐poly(acrylic acid)/bentonite and chitosan‐glutaraldehyde

Abstract

Abstract In this article, new interpenetrating polymer network (IPN) hydrogel as an efficient adsorbent for ammonium was prepared by a two‐step process. First, semi‐IPN hydrogel of chitosan‐g‐poly(acrylic acid)/bentonite (CAB) and chitosan (CTS) was synthesized by grafting polymerization in the presence of exfoliated bentonite as both cross‐linking agent and nanoscale inorganic filler. Second, cross‐linking polymer network of chitosan‐glutaraldehyde (CGA) was formed by reaction of CTS with glutaraldehyde (GA). The obtained IPN hydrogel (CAB/CGA) was characterized by Fourier‐transform infrared spectroscopy, scanning electron microscopy and its swelling degree and PZC value were also measured. These results demonstrate that copolymerized graft reaction was occurred between CTS, AA and bentonite forming CAB, and CGA presented as a cross‐linker in CAB/CGA polymer network. CAB/CGA has a moderate swelling degree of 7.8. CAB/CGA exhibits high adsorption capacity and fast adsorption rate for ammonium. Adsorption process reaches equilibrium in 30 min and fits well to Langmuir adsorption model with a fairly high maximum adsorption capacity of 41.06 mg g −1 . The material has a good regeneration ability. After five times of adsorption–desorption, there was almost no decrease in ammonium adsorption capacity. Moreover, the low swelling degree leads to an improvement in material strength and a reduction of equipment cost.