Removal Of Heavy Metals And Dyes By Biological Iron-Based Minerals In Coordination With Organic Acids

The pollution of heavy metals and dyes in water bodies is an environmental pollution problem that needs to be solved urgently.Hexavalent chromium（Cr（Ⅵ））,trivalent arsenic（As（Ⅲ））and methylene blue（MB）,as typical representatives,seriously endanger the ecological environment and human health.For many chemical reagents and remediation agents,there are problems such as expensive,secondary pollution to the environment and long remediation time,etc.In this study,a wide range of sources,low cost,green environmental protection biosynthetic modified schwertmannite,natural bagasse and siderite and organic acids were used to repair the environment.A series of characterization tools were used to characterize the synthesized biological Iron-based minerals.Batch experiments were designed to screen out the materials with the most suitable complex ratio,and the removal mechanism of heavy metals and dyes was analyzed.The relevant conclusions are as follows.（1）A modified Sch-GO mineral（Sch-GO）was synthesized by the addition of graphene oxide during the biooxidation of Fe²⁺by Acidithiobacillus ferrooxidans,which has a higher photocurrent response signal and faster electron transfer rate than a single graphene oxide and Sch-GO mineral.Therefore,Sch-GO-1.0g with citric acid had more efficient photocatalytic activity to remove both Cr（Ⅵ）and As（Ⅲ）under light conditions within 30 min.（2）The synthesis of biogenic carbon encapsulated iron oxides（C-2.0-Sch-PVA）effectively enhanced the reduction of Cr（Ⅵ）in the presence of OA through two steps of biological oxidation and pyrolysis of Acidithiobacillus ferrooxidans.Electrochemical,XPS and free radical assay results indicate that oxygen-containing groups on the material surface are a prerequisite for triggering Cr（Ⅵ）reduction,and that electron transfer from the inner iron oxide to the conjugated structure of the outer carbon shell promotes the reduction of Cr（Ⅵ）.（3）The Fe@BC=1:2 was synthesized between natural rhodochrosite and biomass（sugarcane bagasse）at a ratio of 1:2 and a pyrolysis temperature of 700°C.Because of its higher specific surface area,more oxygen-containing groups and good electrical conductivity,the mediated oxalic acid showed the best Cr（Ⅵ）and MB removal efficiency within 90min.The mechanism of Cr（Ⅵ）reduction is mainly Fe@BC=1:2mediated electron transfer from oxalic acid to conjugated structures,while the removal of MB is dominated by adsorption.The screening obtained from the chromium salt plant resulted in better synergistic removal of Cr（Ⅵ）with Fe@BC=1:2 than with a single flora and material.