In Magnetic Sludge Biochar To Simulate Wastewater Cr(Ⅵ) And As(Ⅴ) Removal Mechanism Research

This research mainly adopts domestic sludge and zero-valent iron nanoparticles for biochar,raw material preparation of magnetic sludge used in simulated wastewater of Cr（Ⅵ）and As（Ⅴ）removal.Cr（Ⅵ）and As（Ⅴ）is a kind of typical toxic pollutants,water is of great harm to animals and plants.Therefore,how to effectively deal with containing Cr（Ⅵ）and As（Ⅴ）wastewater,and has become a hot topic nowadays.Because chromium and arsenic pollution in the water body is persistent,enrichment,strong toxicity and carcinogenicity.At present,dealing with Cr（Ⅵ）and As（Ⅴ）waste water there are a lot of ways,including oxidation reduction precipitation,ion exchange,biological method and adsorption method,etc.Adsorption method has simple operation,high efficiency,stable operation,the advantages of low cost,so this article uses the adsorption removal in simulated wastewater Cr（Ⅵ）and As（Ⅴ）.Through the initial pH value,the usage of biochar,the initial concentration of Cr（Ⅵ）,oscillation is studied in this time and the initial temperature,the results showed that five factors on the Cr（Ⅵ）and Cr_totalremove all have a significant impact,and Cr（Ⅵ）removal is superior to the Cr_total.This suggests that a large number of Cr（Ⅵ）by reduction of Cr（Ⅲ）first,and then be removed by adsorption.Langmuir model can better describe the removal of Cr（Ⅵ）,and Cr_totalremove more accord with the Freundlich model.Accurate dynamic model of secondary R²more than 0.99,the Cr（Ⅵ）and Cr_totalremoval and quasi level 2 dynamic model more accord with.In addition,Cr（Ⅵ）and Cr_totalremoval is spontaneous adsorption process,give priority to with chemical absorption.SEM,EDS,XRD,XPS and FT-IR characterization results show that the reduction of Cr（Ⅵ）electron donor may be formed in the Fe²⁺,Fe⁰and biochar organisms.Removal of Cr（Ⅵ）and Cr_totalrate control are respectively diffusion in the liquid film diffusion/chemical reaction.In addition,also studied the Cr（Ⅵ）reduction as possible chemical reactions.Through the multiple experiment,this paper discusses the magnetic sludge biological carbon removal mechanism of As（Ⅴ）,the results show that under appropriate conditions,the magnetic sludge biological adsorption of As（Ⅴ）has a strong force,when the pH=2,magnetic sludge biological carbon adsorption capacity is up to 4.229 mg/g removal rate can reach 84.57%.Through the magnetic sludge biochar As（Ⅴ）adsorption data quasi kinetics of primary and secondary fitting model.The fitting coefficients R²were all greater than 0.9,and the fitting theoretical adsorption values of quasi-first-order kinetics and quasi-second-order kinetics were4.717mg/g and 4.431mg/g,respectively.The fitting result of isotherm is in good agreement with Freundlich model.Thermodynamic data show that the gibbs free energy（ΔG）changes are negative,indicates that the reaction is spontaneous and endothermic reaction,the process of temperature rising is advantageous to the reaction.SEM-EDS,XPS,GC-MS,XRD and FT-IR characterization results show that the magnetic sludge of Fe²⁺,Fe⁰of organic matter in the process of removing and biochar participated in As（Ⅴ）reaction process.Are found through analyzing crystal solution which indicates that the As（Ⅴ）was first biochar adsorption and reduction of the As（Ⅲ）and the As-O,then biochar to adsorbed As（Ⅲ）and the As-O and first to be removed.Proposed the As（Ⅴ）to remove the two stages of mechanism analysis.