Elimination Of Pollutants From Water And Mechanism Under PMS/Visible Light With Modified Loofah Composite

In recent years,photocatalysis has been considered as a promising wastewater treatment method.However,the difficulty of recycling the usual powder photocatalyst seriously hinders its practical application.In this study,polydopamine（PDA）modified loofah（LF）was used as a catalyst carrier to activate the visible light/peroxy-monosulfate（PMS）synergistic system to remove the model pollutants tetracycline（TC）and acid orange II（AOII）in simulated wastewater.Two kinds of photocatalysts LF@PDA/Bi VO₄and LF@PDA/Mn O₂were prepared by solvothermal method.The performance and mechanism of these two kinds of catalysts modified by loofah complex under visible light activated PMS catalytic degradation of pollutants in water were studied.（1）Firstly,dopamine hydrochloride was self-polymerized at room temperature to form polydopamine attached to the surface of loofah fiber to obtain LF@PDA,and then the prepared Bi VO₄particles were loaded onto LF@PDA by PEG assisted assembly to prepare LF@PDA/Bi VO₄composite photocatalyst.The composition,morphology and photoelectrochemical properties of the samples were characterized by FT-IR,XRD,SEM,XPS,BET,DRS,PL and photoelectron chemistry.The performance and mechanism of LF@PDA/Bi VO₄/PMS/vis system were studied by simulating visible light with xenon lamp light source and using 10ppm tetracycline and 20ppm AOII as pollutant models.The experimental results showed that LF@PDA/Bi VO₄/PMS/vis system could degrade 90%of TC within 60 min and AOII could be completely degraded within 30 min.In the range of p H 3.1-10.4,LF@PDA/Bi VO₄showed good photo-assisted degradation effect on TC.Different concentrations of HCO₃^-and HA had little effect on the degradation of TC and AOII by LF@PDA/Bi VO₄/PMS/vis system.The photo-assisted degradation effect of LF@PDA/Bi VO₄on TC and AOII was still good after 4 cycles,and the XRD diffraction profiles showed that the crystal structure did not change after cycling,indicating that the catalyst had good stability and could be recycled many times.Radical capture experiments and EPR spectroscopy showed that ¹O₂,·O₂^-,·OH and SO₄^●-were the main active species of LF@PDA/Bi VO₄/PMS/vis system.This study provides a new way to design environmentally friendly and recyclable monolithic photocatalysts for efficient removal of pollutants in wastewater.（2）LF@PDA/Mn O₂was prepared by hydrothermal and in-situ reduction method,and the samples were analyzed by FT-IR,XRD,SEM,XPS,BET,DRS,PL and ESR The performance and mechanism of LF@PDA/Mn O₂/PMS/vis system were studied by using xenon lamp light source to simulate visible light and 10 ppm tetracycline and20 ppm AOII as pollutant models.The experimental results showed that 85%TC can be degraded within 60 min and AOII can be completely degraded within 30 min when the mass ratio of LF@PDA and Mn O₂was 2:1.The degradation of TC showed good photocatalytic performance in the range of p H 2.5-11.5,while different concentrations of HCO₃^-,HA and various anions and cations had little effect on the degradation of TC and AOII by LF@PDA/Mn O₂/PMS/vis system.After 4 cycles of experiments,LF@PDA/Mn O₂still had good degradation effect on TC and AOII.The XRD diffractions of LF@PDA/Mn O₂after cycling showed that the crystal structure did not change,indicating that the catalyst had good stability.Free radical capture experiments and EPR spectroscopy showed that ¹O₂,·O₂^-,·OH and SO₄^●-were the main active species of LF@PDA/Mn O₂/PMS/vis system.The improved photocatalytic performance of LF@PDA/Mn O₂/PMS/vis system is attributed to that PMS acted as a photogenerated electron acceptor and PDA acted as the electron transfer mediator.The synergistic effect in the PMS/vis system with natural loofah as carrier to effectively degrade antibiotics（TC）and dyes（AOII）provides a new strategy for activating PMS to effectively remove organic pollutants.