Preparation Of Chitosan-based Biochar And The Study In Adsorption Properties For Dyes

Dye wastewater is large discharged,polluting and difficult to biochemical treat.Adsorption is a hotspot in the treatment research of dye wastewater.In this study,nitrogenous chitosan was selected as the raw material,and chitosan-based biochars were prepared for dye adsorption by means of high-temperature treatment,KOH activation and freeze-drying.The preparation conditions and adsorption laws were explored.The adsorption mechanism of dyes is described.(1)Based on the adsorption performance of malachite green(MG),the effects of the preparation conditions of chitosan-based biochar were analyzed,and the optimal preparation temperature of 700? and the KOH activation of 25% by mass were determined.The specific surface area of the activated chitosan-based biochar(ACB)was 444.8766m2/g.the average pore size was 1.8501 nm,and the adsorption amount of MG reached 303.6mg/L.Effects of MG concentration,p H,temperature and time on the adsorption performance of MG were investigated,and the adsorption kinetics analysis and isothermal adsorption model analysis were performed.Adsorption process of ACB to MG was multi-layer adsorption which complied with the secondary kinetic model and Freundlich isothermal adsorption model.This biochar got a high degree of surface heterogeneity.(2)The chitosan sol was freeze-dried to obtain the chitosan xerogel,and the activated chitosan-based carbon aerogel(ACCA)was prepared by co-heating with KOH at 700?.The specific surface area reach 1035.6340m2/g,and obvious vertical slices structure can be observed in the surface.In the conditions of 25?,p H=7 and 2000mg/g of solution concentration,adsorption amount of MG reached 966.46mg/g in 4 hour;the effects of MG concentration,p H,temperature and time on the adsorption performance were investigated.The adsorption process was multi-layer adsorption which complied with the secondary kinetic model and Freundlich isothermal adsorption model.This carbon aerogel had a three-dimensional network structure,few types of functional groups were laid on the surface and it was stable.(3)FTIR,XPS,SEM-EDS were implied before and after adsorption explore the mechanism of adsorption.The adsorption process of ACCA on MG mainly includeselectrostatic interaction,ion exchange,?-? stacking,hydrogen bonding and pore retention.