Study On Adsorption/Desorption Properties Of Cellulose-Based Membrane For Pb²⁺

Cellulose is environmentally friendly and degradable,which has a wide range of sources and a certain adsorption capacity.Cellulose-based membranes are prepared from cellulose in the alkaline composite solution system,used for the treatment of heavy metal Pb2+,which has the advantages of high adsorption efficiency,environmental protection of reagents,simple operation and easy recovery.In this paper,cellulose membrane(CM),KMnO4 pretreatment cellulose membrane(PPCM)and sodium alginate cellulose membrane(SACM)were prepared by phase conversion method using cellulose as raw material.The effects of preparation conditions and adsorption conditions on the adsorption capacity of three cellulose membranes for Pb2+ were studied.The adsorption kinetic model and adsorption isotherm model were analyzed.XRD and TG were used to characterize the three kinds of membranes,and SEM,FTIR and EDS were used to analyze the three kinds of membranes before and after adsorption for Pb2+,and the adsorption mechanism was obtained.The effects of desorption conditions on the three membranes were investigated to determine the optimal desorption capacity.The main findings of the paper are as follows:(1)Adsorption/desorption properties of CM for Pb2'The maximum adsorption capacity of CM for Pb2+ is 343.00 mg/g,and the adsorption process conforms to the quasi-second-order kinetic model and Freundlich model.After adsorption of Pb2+,the pores of CM are filled and saturated,and become dense and rough.The adsorption capacity of CM for Pb2+ is improved though the chelation of C=O and N—H groups,part of the crystalline form of cellulose changed from type ? to type ?,the thermal stability of CM is lower than that of cellulose,the optimal desorption capacity of CM for Pb2+ is 90.12 mg/g.(2)Adsorption/desorption properties of PPCM for Pb2+The maximum adsorption of PPCM for Pb2+ is 436.78 mg/g.The adsorption process conforms to the quasi-second-order kinetic model and the Freundlich isotherm model.After the adsorption of Pb2+,the surface of the PPCM becomes rough and dense.The amount of C=O groups and N—H groups in PPCM is more than CM,and the amide group appears,those groups are conducive to chelation with Pb2+,and improves the adsorption capacity of PPCM.Its crystallinity and thermal stability are lower than CM.The optimal desorption capacity of PPCM for Pb2+ is 107.62 mg/g.(3)Adsorption/desorption properties of SACM for Pb2+The maximum adsorption of SACM for Pb2+ is 509.35 mg/g.The adsorption process conforms to the quasi-second-order kinetic model and the Freundlich isotherm model.SACM has a three-dimensional network structure,after adsorbing Pb2+,the network structure is filled and saturated,and the carboxyl groups on the membrane are saturated.After the adsorption of Pb2+,the C=O group of the carboxyl group,the O-C-O group and the C-O group of the acetal interact with Pb2+ and disappear,and the crystallinity and thermal stability of SACM are higher than those of PPCM.The best desorption capacity is 116.85 mg/g.