Removal Of Cr(?) From Water By Stable Zero Valent Iron Sulfide And Its Removal Mechanism Research

Cr???pollution in the water environment is becoming more and more serious,which is very harmful to human body.In this study,a functional material?SZVI-SA?with the ability to efficiently remove hexavalent chromium Cr???was successfully prepared.This composite was based on micron zero-valent iron?ZVI?as the core.The ZVI was vulcanized modified and alginate?SA?loaded.Effects of the main parameters on the Cr???removal properties of the materials during preparation were investigated,and the physicochemical properties of the synthesized materials were fully characterized and analyzed.In order to provide theoretical basis and technical support for the application of SZVI-SA in practical process,the Cr?VI?removal efficiency of composite materials under different environmental factors was studied,and the adsorption model,kinetic model and characterization analysis were combined to explore the mechanism of Cr?VI?removal.At the same time,it also provides an economical,efficient and environmentally friendly composite material for Cr???removal.?1?Fe³⁺was selected as a sodium alginate chelating agent with a concentration of 7%,a ratio of sodium sulfide to ZVI of S/Fe=3.5,an aging time of 4h,and a drying temperature of 70°C as the material preparation conditions.The effects of various components on the removal of Cr???during the synthesis of materials were studied.The total chromium content and total iron content in the solution after the reaction were comprehensively analyzed,and it was found that SZVI-SA could remove Cr???better,and at the same time,it can also effectively remove Cr???and Fe???in the solution.?2?Materials prepared under ZVI and different S/Fe conditions were prepared and used for characterization analysis of SEM-EDS,TEM,BET,TG-DSC,XRD,and FTIR.The results showed that the materials prepared in this study had the following characteristics:The active ingredient is Fe S;the specific surface area is larger at97.83m²/g;the micropores are the main ones and there are more pores;the surface potential is lower,showing electronegativity.?3?The effects of dissolved oxygen concentration,dosage,initial concentration,temperature,p H value,organic matter content and coexisting ions on the removal efficiency of Cr???by SZVI-SA.The results show that the reduction of dissolved oxygen content,the increase of dosage and the increase of temperature can effectively improve the removal efficiency of Cr???;it has a certain tolerance in the range of p H2-9,and the removal efficiency of Cr???can reach more than 98%.Organic matter?<100mg/L?and coexisting anions and cations?0-5mmol/L?have no effect on the removal efficiency of Cr???except Mg²⁺.?4?The removal of Cr???by SZVI-SA composites conforms to the quasi-second-order kinetic model,indicating that the adsorption rate is mainly controlled by the chemical reaction rate between Cr???and the binding site of SZVI-SA;Langmuir-Freundlich and Redlich-Peterson isothermal adsorption model proves that the composite can act on Cr???by many mechanisms,mainly by chemisorption on heterogeneous surfaces.The saturated adsorption amount of Cr???is 79.68±4.81 mg/g?25??.The characterization results show that the reaction mechanism of SZVI-SA and Cr???is mainly redox reaction,and the main products after the reaction are Fe???and Cr???,Fe???and Cr???pass through adsorption and Co-precipitation is absorbed on the surface of the material.The final products are Fe?OH?₃,Cr?OH?₃ and Cr₂O₃,which can be separated from water.