The Preparation Of Modified Straw Biological Adsorbent And Its Adsorption Study On Chromium Pollution Wastewater

In recent years,chromium water pollution is very serious in China.In this study,taking the corn straw as raw material by using citric acid and chitosan and Fe₃O₄ on the modification,preparation of two kinds of adsorption material,through SEM,XRD,Zeta,FTIR and XPS methods had been used to characterize the composition,surface morphology,the batch adsorption of Cr?VI?test to study the different factors on the MC and the absorption effect of the SMC,and studied the adsorption kinetics and isothermal adsorption and FTIR and XPS analysis,to further explore the mechanism of adsorption.The main contents and results were as follows:The pores of the modified straw?MC?increased and the surface contained a large number of carboxyl groups.The adsorption capacity of the MC on Cr?VI?was twice that before the modification.The adsorption experiment results showed that the optimal pH value of Cr?VI?adsorption by MC was 3 and reached saturation at 80 min.The adsorption process of Cr?VI?by MC was in accordance with the quasi-second-order kinetic model.The Langmuir model had a higher degree of fitting for the process of Cr?VI?adsorption by MC,and the anion had a negative effect on the adsorption process of MC.FTIR analysis showed that the main functional groups in MC adsorption of Cr?VI?were carboxyl group and hydroxyl group.Magnetic composite?SMC?of ball surface carries a positive charge,contains a large amount of reactive functional groups,and has strong paramagnetism,the experimental results show that the adsorption of SMC adsorption optimal pH value of 3,but Cu?II?presence will reduce the adsorption capacity of SMC in 100 min adsorption is close to balance,quasi level 2 dynamic model of SMC adsorption of Cr?VI?the process of fitting effect is better,Langmuir is more suitable to describe the adsorption process of Cr?VI?by SMC.As the temperature increases,the adsorption capacity of Cr?VI?by SMC increases.The adsorption was endothermic and spontaneous.FTIR and XPS analysis showed that the main functional groups in the adsorption process were carboxyl group,hydroxyl group and amino group,mainly coordination and electrostatic adsorption,and part of Cr?VI?was reduced to Cr?III?.The desorption regeneration test showed that in 100 ml,0.2 mol·l^-11 NaOH solution,the desorption took about 400 min,and the regeneration rate of 2 g SMC reached 80%.