Synthesis Of MIL-53(Fe)/SnS And Its Photocatalytic Reduction Of Hexavalent Chromium In Water

Water is the source of life.70%of the earth surface is covered by water,but fresh water that can be directly used to production life is less than 3%,and freshwater resources are often poisoned with pollution.At present,the problem of water pollution has brought about the widespread attention.Many types of pollutants can cause water pollution,such as inorganic substances,aerobic substances,heavy metals,pathogenic microorganisms,etc.As some substances entering the water,they are transformed into more harmful pollutants through physicochemical reactions and biological effect.Furthermore,they are stable,difficult to degrade,endangering the water quality and aquatic biomes.The chromium???produced by leather tanning,smelting and other industrial production has a great impact on the health of organisms including humans.In addition,the high migration of chromium???in water can pose a significant threat to water supply sources such as surface water and groundwater.Therefore,chromium???is chosen as the target pollutant to test the feasibility of photocatalytic technology for its removal.Photocatalysis is a technique for photochemical reactions on the surface of catalysts,which shows attractive application prospects in water pollution control.The electron-hole pairs excited by light will combine with water to generate free radicals to degrade environmental pollutants.As an important metal sulfide semiconductor,SnS-based materials have attracted extensive attention in photocatalytic degradation of environmental pollutants.However,the photocatalytic efficiency of pristine SnS is not high.In this paper,MIL-53?Fe?as an iron-based metal organic framework,was combined with SnS to improve its photocatalytic activity.The enhanced photocatalytic performance is due to the introduction of MIL-53?Fe?which resulted in the strengthened adsorption in the visible region,larger specific surface area and higher electron-hole separation rate.The experimental results show that this method greatly improved the photocatalytic activity of SnS.In this paper,a simple one-step deposition method was used to synthesize MIL-53?Fe?/SnS composites,and a series of characterizations were carried out to obtain the morphology and structure information.The photocatalytic reduction activity of Cr???on the composite was further investigated and the effect of loading dosage of MIL-53?Fe?on the photocatalytic performance was also discussed.In addition,Photocatalytic removal mechanism of Cr???was explored.The results show that when the loading amount of MIL-53?Fe?in the composite is 15 mg,the reduction rate of chromium???is 71.3%after an hour of light,which is higher than that of pure MIL-53?Fe??16.1%?and pure SnS?26.5%?under the same conditions.Free radical trapping experiment and ESR spin-trap test shows that superoxide radicals?·O₂^-?,photogenerated electrons?e^-?and holes?h⁺?are the main active species toward chromium???reduction.Finally,five-cycle experiments and XRD test after the illumination shows that the reduction rate of chromium???has dropped from 71.3%to 69.5%and the crystal surface of remains unchanged after photocatalysis,which demonstrates MIL-53?Fe?/SnS composites has good recyclability.In summary,MIL-53?Fe?/SnS composites can be used as a highly efficient photocatalyst on the reduction of chromium???in wastewater,and the synthesis method of the composite is simple.Modified semiconductors with metal organic framework provide new design ideas for the improvement of photocatalysts.SnS-based nanocomposites will have great potential in the treatment of environment heavy metal contaminants.