Preparation and absorption properties of polyaspartic acid/lignocellulose hydrogels

Polyaspartic acid(PASP)/lignocellulose (LNC) hydrogels were synthesized through aqueous polymerization method; the effects of pretreatment time, pretreatment temperature, KMnO₄ concentration, glutaraldehyde amount, PASP amount, reaction time and reaction temperature on adsorption property of PASP/LNC hydrogels for Pb²⁺, Cd²⁺ were evaluated; the maximum adsorption capacity of PASP/LNC hydrogels was calculated by Langmuir adsorption isotherm; HNO₃ was used to perform desorption and regeneration experiments of PASP/LNC hydrogels; the structure of the hydrogels was characterized by SEM and FTIR. The adsorption result shows that when the pretreatment time is 15 min, the pretreatment temperature is 50 ℃, the KMnO₄ concentration is 0.06 mol·L^-1, the glutaraldehyde amount is 1.00 g, the PASP amount is 11 g, the reaction time is 3.5 h and the reaction temperature is 70 ℃, the equilibrium adsorption capality for Pb²⁺, Cd²⁺ could reach 980.39 mg·g^-1, 813.01 mg·g^-1. The adsorption/desorption cycling experiment indicates that the adsorption capality of PASP/LNC hydrogels is ideal after four cycles of adsorption/desorption, so PASP/LNC hydrogels are confirmed as a adsorbent for recycling. The characterization results show that the surface of PASP/LNC hydrogels has gap of varying sizes, polycondensation reaction is developed between —COOH of PASP and O—H of LNC, which forms hydrogels of three-dimensional network structure.