Preparation Of MXene Matrix Composites And Their Pollutant Removal Performance From Water

The rapid development of modern industry has improved people’s material living standards,but also caused serious damage and pollution to the environment.Among them,water pollution has seriously threatened human health and social stability.Heavy metals and bromate are typical pollutants of water bodies.The removal of heavy metals and bromate by catalytic reduction with catalysts has attracted much attention because of its advantages of low energy consumption,non-toxicity,high selectivity and fast and efficient.Catalyst is the key factor affecting the performance of catalytic reduction system.Therefore,it is of great theoretical significance and application value to develop the catalysts with high efficiency and low secondary pollution.The two-dimensional material MXene has the advantages of large specific surface area,good electrical conductivity,and excellent light absorption properties,showing great potential in energy storage,electromagnetic shielding,supercapacitor,and water treatment.In this thesis,to address the drawbacks of high energy consumption,poor stability and low selectivity of traditional methods for the removal of water pollutants,two MXene based composite catalysts were designed and prepared by using the synergistic effect between different materials.The obtained MXene based composite catalysts were used to construct high-performance photothermal-photocatalytic membrane and cathode electrode.The specific conclusions are as follows:（1）A simple and scalable method has been developed to prepare mo-Ti₃C₂@BF membranes for photocatalytic-photothermal synergistic removal and reuse of heavy metal ions,as well as recovery of clean water.Specifically,the mo-Ti₃C₂-2.4@BF membrane in Co（NO₃）₂solution can achieve an excellent evaporation rate of 4.6 kg·m^-2·h^-1 and a high solar-vapor efficiency of up to 97.5%with simultaneous removal and reuse of heavy metal ions from simulated wastewater under the light intensity of 2.44 k W·m^-2.After 90 min of reaction,no heavy metal ions are detected in any of the condensed water,and the Co²⁺removal rate in the concentrated Co（NO₃）₂ solution is up to 80.4%,which was higher than the removal rates of other heavy metal ions(Pb²⁺,Zn²⁺,Mn²⁺and Cu²⁺).The high photothermal conversion efficiency and good heavy metal removal performance were attributed to the comprehensive optimization and synergistic effects of the multifunctional membranes:the mo-Ti₃C₂heterojunction formed by the in situ oxidation of Ti₃C₂ enhanced the photocatalytic reduction of heavy metal ions;the high photothermal conversion efficiency and good electrical conductivity of Ti₃C₂ nanosheets and photoinduced reduced nanoparticles realized the rapid evaporation of water and photoinduced charge separation;the strong capillary force of superhydrophilic BF membrane realizes the continuous transport of heavy metal solution.This synergistic photocatalytic-photothermal approach has great potential for the practical removal and reuse of heavy metal ions.（2）Nb₂C MXene-supported highly dispersed bimetallic catalysts were developed by a one-step high-temperature molten salt method,and successfully applied to the electrocatalytic reduction of bromate.The effects of metal type and loading,ratio of metal to MXene,cathode potential,solution p H and bromate concentration on the performance of electrocatalytic reduction of bromate based on Nb₂C MXene supported highly dispersed bimetallic catalyst were investigated,and the mechanism of electrocatalytic reduction of bromate was revealed.The Cu_0.2/Fe_0.1/Nb₂C electrode exhibited the highest electrocatalytic reduction BrO₃^-efficiency of 94.2%at-1.0 V potential,which was 1.93,1.34 and 1.20 times higher than that of Nb₂C,Fe_0.1/Nb₂C and Cu_0.2/Nb₂C electrodes,respectively.The synergistic effect of Cu single atoms and Fe₂O₃ nanoparticles in Cu_0.2/Fe_0.1/Nb₂C electrodes contributes to the formation of atomic H^*,and MXene with high conductivity promotes fast charge transfer,thereby improving the efficiency of indirectly atomic H^*reduction of BrO₃^-to Br^-.The Cu_0.2/Fe_0.1/Nb₂C electrode can efficiently reduce BrO₃^-to Br^-in water,and has good cycle stability,showing promising application prospects in the removal of BrO₃^-pollutants in actual water.