Study Of The Synthesis, Characterization Of FeS And Fe/FeS Particles And Application For Aqueous Cr(?) Removal

Ferrous sulfide is widespread in nature, with good adsorption capacity and reduction property, which plays an important role in environmental remediation, especially showing an unique effect on heavy metals and chlorinated pollutants treatment. Synthetized by traditional method, FeS particles are prone to aggregating, which greatly reduces the specific surface area, pollutant reduction activity and dispersal ability. Some studies find that the multicomponent Fe/FeS particle is a kind of effective treating agent with unique physical and chemical properties, which greatly enhance reduction performance compared with monocomponent nZ?. It has important significance for environmental remediation to explore new synthesis methods to obtain environmental remediation materials with a better dispersibility, a larger surface area and a stronger reducing activity.This study has successfully synthetized FeS and Fe/FeS particles by two different methods based on literature research of synthetic methods and the preliminary experiment results. The morphology, element composition, phase structure and specific surface area of as-prepared samples were characterized by SEM-EDS?Scanning Electron microscope-energy dispersive spectrometer?, XRD?X-ray diffraction? and BET?Specific surface area test method?, respectively. This study also investigated the reduction abilities of FeS and Fe/FeS for Cr??? and the remediation tests for Cr??? contaminated groundwater by FeS and Fe/FeS also conducted. Conclusions as follow:Various micro-structural mackinawite?FeS? have been prepared by L-cysteine-assisted solvothermal method, which possessed high purity. The solvent ethylenediamine?EN? could contribute to the dispersion of crystalline FeS. The uniform micro-structure was observed at 200?, and when the temperature was lower than 200?, crystal structure of FeS formed irregularly since incomplete decomposition of L-cysteine. As reaction time increased, the structure of FeS changed due to reconstruction in the process of crystal growth. When sulfur content increasing, the micro-structure of FeS changed from sheets to bars, which accelerated the reaction rate between FeS and Cr???.The main component of Fe/FeS synthesized by reductant NaBH4 was Fe0, which mainly presented multicomponent nanoparticles with average particle size of 100 nm. Synthesized FeS used three different sulfur sources showed remarkable difference on microstructure and Cr??? removal ability. When using Na₂S2O₄ or Na2S2O3 as the sulfur source, Cr??? removal efficiency increased firstly and then decreased with molar ratio of Fe/S decreasing. However, increasing the content of Na2 S would continuously improve the reactivity of Fe/FeS. A small amount of CMC addition, with optimal CMC concentration of 0.01%, could effectively control the particle size of Fe/FeS and significantly improve the removal efficiency of Cr???.Synthesized FeS and Fe/FeS particles were used for Cr??? contaminated groundwater remediation tests, which showed that increasing dosage of FeS and Fe/FeS and rising temperature promoted removal ability of Cr??? by FeS and Fe/FeS. Both alkaline environment and the presence of humic acid went against Cr??? reduction. The removal capacity of FeS was increased with increasing initial Cr??? concentration, with the maximum removal capacity of 99.36 mg/g when initial concentration of Cr??? was 50 mg/L. However, with the initial concentration of Cr??? increasing, removal capacity of Fe/FeS increased firstly and then decreased, which achieved the maximum removal capacity of 227.49 mg/g when initial concentration of Cr??? was 50 mg/L. The presence of dissolved oxygen would restrain Cr??? reduction by FeS while enhance the Cr??? removal efficiency by Fe/FeS.