Study On Synthesis And Adsorption/Desorption Of Heavy Metal By Lignocelluloses Based Hydrogels

Lignocellulose based hydrogels were prepared, the adsorption and desorption properties of Pb2+ and Cd2+ were studied. The effects of different preparation conditions of the hydrogels were inspected. The structural changes in the hydrogels were characterized. The swollen properties of hydrogels were inspected by changing time, temperature, the intensity of ion and pH. Adsorption characteristics of hydrogels were investigated by changing adsorption time, adsorption temperature、initial metal ions concentrations, and the pH of solution, and the adsorption mechanism was also explored. Subsequently, the effects of desorption time, desorption temperature, and the concentration of HNO3 on desorption properties of the hydrogels were studied.The main experimental results were as follows:1. Synthesis of lignocellulose-g-acrylic acid hydrogels and the adsorption/desorption properties of Pb2+、Cd2+Preparation results showed that, the adsorption capacity of LNC-g-AA hydrogels reached the maximum with weight ratios of acrylic acid to lignocellulose 7, and neutralization degree 50%. The testing of swollen properties showed that LNC-g-AA hydrogels could better response with the changing of time, temperature, the intensity of ion and pH. Adsorption results showed that, adsorption time 120 min and 60min, adsorption temperature 30℃ and 40℃ , the initial concentration of Pb2+、Cd2+ 0.04mol/L and 0.05mol/L, and pH 5.5, respectively, were the best adsorption condition of LNC-g-AA hydrogels, and the adsorption maximum capacities for Pb2+、 Cd2+ were 953.9 mg/g and 403.8 mg/g. In desorption examination, the researched the effects of desorption time, desorption temperature, and the concentration of HNO3 on desorption capacities of LNC-g-AA hydrogels for Pb2+、Cd2+ were researched. The research results determined that the largest desorption amount for Pb2+、Cd2+ were 850.1 mg/g and 366.5mg/g respectively when reaction time 60min and 30min, temperature 30℃ , and 0.04 mol/L HNO3, the desorption efficiencies were 89.1% and 90.8%, respectively.2. Adsorption/desorption properties and adsorption mechanisms of Pb2+、Cd2+ of lignocellulose-g-acrylic acid bonded lanthanum nitrate (La3+/(LNC-g-AA)) hydrogelsPreparation results indicated that, the adsorption capacities of La3+/(LNC-g-AA) hydrogels reached the maximum with weight ratios of acrylic acid to lignocellulose 7, and neutralization degree 50%. The testing of swollen properties showed that La3-/(LNC-g-AA) hydrogels could better response with the changing of time temperature, the intensity of ion and pH. Adsorption results showed that the optimum adsorption condition were adsorption time 120 min, adsorption temperature 30℃ and 40℃ , the initial concentration of Pb2+、Cd2+ 0.04mol/L and 0.05mol/L. and pH 5.5, respectively, and the maximum adsorption capacities for Pb2+、Cd2+ were 934.7 mg/g and 363.0 mg/g. And the adsorption mechanisms contained that physical adsorption mainly dependent on the structure of the hydrogels and chemical adsorption dependent on the chelation and ion exchange interaction. In desorption examination, the effects of desorption time and desorption temperature and the concentration of HNO3 on desorption capacity of La3+/(LNC-g-AA) for Pb2+、Cd2+ were researched, the maximum desorption capacities of La3+/(LNC-g-AA) for Pb2+、Cd2+ were 916.8mg/g and 336.5mg/g respectively when desorption time 30min, desorption temperature 30℃ , and 0.04 mol/L HNO3, respectively, the desorption efficiencies were 98.1% and 92.7%, respectively.3. Synthesis and adsorption/desorption properties of Pb2+、Cd2+ of lignocellulose-g-acrylic acid/acrylamide/montmorillonite (LNC-g-AA/AM/MMT) hydrogelsPreparation results showed that, the best preparation condition of LNC-g-AA/AM/MMT were weight ratios of acrylic acid to acrylamide 7, neutralization degree 50%, initiator content 0.30%, content of crosslinking agent 0.03%, and MMT content 25%. Adsorption results showed that the best adsorption condition were adsorption time 120 min and 60 min. adsorption temnerature 40 ℃ and 30℃ , the initial concentration of Pb2+、Cd2+ solution 0.04mol/L and 0.06mol/L, and pH 5.5, respectively, the adsorption capacities of LNC-g-AA/AM/MMT were 504.2 mg/g and 246.9 mg/g, respectively. The effects of desorption time, desorption temperature and the concentration of HNO3 on desorption capacity of LNC-g-AA/AM/MMT for Pb2+?Cd2+ were researched. The results showed that the maximum desorption capacities of LNC-g-AA/AM/MMT for Pb2+/Cd2+ were 470.9mg/g and 229.4mg/g respectively when desorption time 60min. desorption temperature 40℃ and 30℃ , and 0.04mol/L and 0.02mol/L HNO3, respectively, the desorption efficiencies were 93.4% and 92.9%, respectively.