Adsorption Of As(Ⅴ) And Sb(Ⅲ) By Lanthanum-doped Iron Oxides Supported On Biochar And Its Effect On Microbial Community Structure In Wastewater

With the rapid and healthy development of China’s national economy and the rise of industrial technology in recent years,the problem of heavy metal ions in sewage discharged into nature due to improper treatment is becoming more and more serious.The exposure of heavy metal ions poses a serious health threat to mankind.In order to remove As（Ⅴ）and Sb（Ⅲ）from wastewater and reduce their harm,biochar was prepared by hydrothermal method using cheap and easily available corn straw.Biochar was modified by ferric chloride hexahydrate and lanthanum nitrate hexahydrate to obtain lanthanum doped ferrite loaded on biochar,and its adsorption performance and mechanism for As（Ⅴ）and Sb（Ⅲ）were studied,The effect of lanthanum doped iron oxide loaded on biochar on the microbial community structure in actual antimony containing wastewater was studied.The conclusions are as follows:Fourier transform infrared spectroscopy（FT-IR）,scanning electron microscopy（SEM）,X-ray diffraction（XRD）,specific surface area and porosity analyzer（BET）were used to characterize biochar and lanthanum doped iron oxide loaded on biochar.The adsorption experiment were carried out to explore the adsorption performance of As（V）and Sb（III）from the aspects of pH value,dosage,ionic strength,adsorption time,adsorption kinetics and adsorption isotherm.Finally,Illumina high-throughput sequencing technology was used to study the effect of lanthanum doped iron oxide loaded on biochar on the microbial community structure in wastewater.Finally,Illumina high-throughput sequencing technology was used to study the effect of lanthanum doped iron oxide loaded on biochar on the microbial community structure in wastewater.The conclusions are as follows:（1）There are some differences in the appearance structure between corn straw biochar（CBC）and biochar loaded lanthanum doped iron oxide（Fe-La-CBC）.The surface of CBC is smoother,and the surface of Fe-La-CBC is rougher.CBC surface has less pore structure,Fe-La-CBC surface has more pore structure and spherical particles similar to Fe₃O₄are distributed on the surface.Both CBC and Fe-La-CBC have absorption peaks of O-H,C-O,and C=O functional groups.These three functional groups play an important role in the adsorption process,but these three functional groups have stronger peaks in Fe-La-CBC than in CBC.Through EDS analysis,Fe-La-CBC contained iron lanthanum,indicating that the biochar-supported lanthanum-doped iron oxide was successfully prepared.Both CBC and Fe-La-CBC have characteristic diffraction peaks corresponding to the{101}and{002}planes of cellulose crystals.After CBC modification,the specific surface area and pore size of Fe-La-CBC are larger than CBC.（2）In the adsorption experiment,the adsorption of As（Ⅴ）and Sb（Ⅲ）by Fe-La-CBC conforms to the pseudo second-order kinetic model,which shows that the adsorption process of As（Ⅴ）and Sb（Ⅲ）by Fe-La-CBC belongs to chemical adsorption process.The isothermal adsorption experiments of As（Ⅴ）and Sb（Ⅲ）by Fe-La-CBC accord with the Langmuir isothermal model,indicating that the adsorption process is monolayer adsorption.The adsorption process of Fe-La-CBC for As（Ⅴ）and Sb（Ⅲ）was not affected by three common anions(Cl^-,SO₄^2-,NO₃^-)and two cations(Ca²⁺,Mg²⁺).When pH=5,temperature is 318K,the dosage is 300 mg/20ml,and the adsorption time is 60 min,the maximum theoretical adsorption capacity of Fe-La-CBC for As（Ⅴ）is 4.87 mg g^-1.In the adsorption of Sb（Ⅲ）by Fe-La-CBC,when pH=2,temperature is 318K,the dosage of Fe-La-CBC is 50mg/20 ml,and the maximum theoretical adsorption capacity is 32.86 mg g^-1.After four times of desorption and regeneration,the removal rates of As（Ⅴ）and Sb（Ⅲ）by Fe-La-CBC are still 38.57%and 57.68%,indicating that Fe La CBC has a certain reuse value.（3）Adding Fe-La-CBC into the antimony wastewater affected the richness and diversity of the microbial community.The Chao1 index,Shannon index and Simpson index of sample A without Fe-La-CBC were higher than those of sample B with Fe-La-CBC.At the phylum level,the dominant phyla in samples A and B are Proteobacteria,but the relative abundance of Proteobacteria in sample B significantly increased,and the significantly different taxa in sample A in the LEf Se difference analysis for Firmicutes,the significantly different phylum B samples is Proteobacteria.At the genus level,the dominant genera of sample A were Tepidiphilus and Acinetobacter,and the dominant genera of sample B were Acinetobacter and Pseudomonas.In LEf Se difference analysis,the significantly different genera of sample A were Wolinella,Bacillus and other six groups,and the significantly different genera of sample B were Acinetobacter,Pseudobacterium Pseudomonas.In addition,the repeatability between the two groups of samples A and B was good.