Study On Preparation Of Biochar And Adsorption Kinetics Of Pb²⁺ In Waste Water From Lead-acid Battery Factory

Lead-acid batteries are very mature for automotive and industrial applications and have been successfully used in utility energy storage.Lead pollution produced in the process of production and recovery has irreversible harm to human health.It is of great significance to develop a kind of adsorbent with economic stability and easy separation for the treatment of lead battery pollution.Biochar,which is prepared from biomass,has great potential in the treatment of lead-containing wastewater from lead battery plants because of its wide source and low cost.The adsorption performance of original biochar for pollutants is not ideal.In this study,coconut peel was used as biochar raw material,and Fe（NO₃）₃and Mg Cl₂/KMn O₄/Ce（NO₃）₃were impregnated together with thermochemical conversion method to obtain biomass-derived unmodified magnetic biochar and three modified bimetallic loaded magnetic biochar.In this study,the adsorption performance of Biochar for Pb²⁺in simulated lead-acid battery factory wastewater was analyzed through adsorption experiment and characterization experiment.The main contents and research results are as follows:（1）Unmodified biomass-derived magnetic biochar（FBC）,alkaline earth metal-loaded magnetic biochar（MFBC）,transition metal-loaded magnetic biochar（KFBC）and rare earth metal-loaded magnetic biochar（CFBC）were prepared by thermal transformation.Characterization experiments showed that the defect degree of modified biochar increased,oxygen content increased,contact Angle decreased from 10°to 0-4°;Metal oxides were added to the surface of biochar,which increased the mineral content of biochar,but the magnetic properties of biochar decreased slightly after modification.Effects of p H values,interfering ions and initial solution concentration of four biochar on the adsorption performance of Pb²⁺.When p H value is 5,the adsorption capacity of the four biochar is the best,and the maximum adsorption capacity can reach 114.7 mg/g.When Ca²⁺concentration increased to 5 m M,the adsorption capacity of the magnetic biochar to Pb²⁺decreased by more than 10%.The adsorption process of MFBC belongs to multi-layer adsorption,and the theoretical maximum adsorption capacity is202.3 mg/g.FBC,KFBC and CFBC belong to monolayer adsorption,and the theoretical maximum adsorption capacity is 29.6 mg/g,168.6 mg/g and 140.8 mg/g,respectively.（2）The fitting results of the four adsorption kinetics showed that the adsorption processes of FBC,MFBC,KFBC and CFBC were dominated by chemisorption.The adsorption capacities were 26.4702mg/g,114.4755 mg/g,118.1883 mg/g and 122.7613 mg/g,respectively.With the passage of time,the adsorption amount of magnetic biochar does not increase,and the reaction reaches dynamic equilibrium.Elovich showed that the adsorption process was influenced by both physical adsorption and chemical adsorption.The adsorption process is a combination of fast adsorption and slow adsorption,but physical adsorption is not stronger than chemical adsorption in the whole process.（3）The biochar was characterized by FTIR,XRD and XPS before and after adsorption,and the surface oxygen-containing functional groups,crystal structure and chemical bonds were compared and analyzed.XPS results showed that O1s peak shift,lattice oxygen and chemisorbed oxygen content increased,hydroxyl oxygen content decreased.The results of FTIR and XRD showed that the peak intensity of surface hydroxyl and carboxyl groups decreased due to the consumption.The diffraction peaks of lead carbonate and basic lead carbonate appeared on MFBC surface,and the diffraction peaks of lead carbonate also appeared on CFBC surface,while the crystal structure of KFBC surface hardly changed.Quantitative analysis shows that the adsorption dominated by ash and oxygen-containing functional groups after modification is relatively large.KFBC has the highest proportion of the adsorption amount dominated by oxygen-containing functional groups,which can reach 15.17%.The ash dominated adsorption capacity of MFBC accounted for a large proportion,up to 90.09%,indicating that the metal oxide loading provided support for the improvement of Pb²⁺adsorption capacity of biochar.Comprehensive analysis shows that compared with the original magnetic biochar,bimetallic supported biochar has significantly higher adsorption capacity and adsorption rate,and its application in lead battery plant wastewater treatment is easy to separate,which is of great significance to water pollution control.