Preparation Of Heterogeneous Functional Materials Of Visible-light-driven Silver Series For The Removal Of Triphenylmethane Dye From Water

The production of organic dyes is increasing year by year,because human beings constantly pursue color.According to the survey,about 10%-15%of dye in the process of its production and use is discharged into the environment along with the wastewater,which inevitably causes water pollution,thereby poses potential threat to human and ecological health.With the increasingly serious water pollution,it is imperative that some effective measures need be taken to remove dyes from printing and dyeing wastewater as well as natural waters.Traditional techniques of dye removal from wastewater in depth degradation,cost control and harmless processing are still far from satisfactory.Thus,it is an urgent need to develop an efficient and environment-friendly technique to treat dye wastewater.The aim of this work is to eliminate triphenylmethane dye from aqueous solution,which is the third largest dye species of usage amount.We chose three typical triphenylmethane dye such as mixed dye of basic fuchsin and basic red 9(BFR),malachite green(MG)and crystal violet(CV)as the target pollutants,and presented efficient technologies to respectively remove this three dyes from aqueous solution via visible-light catalytic technique based on AgBr-Ag3PO4/MWCNTs and Ag3VO4/g-C3N4,as well as adsorption and visible-light catalytic technique based on Ag3VO4/BiOI.These approaches based on heterogeneous functional materials of silver series are affordable,easy-operated and efficient.The AgBr-Ag3PO4/MWCNTs composite was successfully synthesized by AgBr-Ag3PO4 loading on MWCNTs using precipitation method.It was applied to remove BFR from aqueous solution.The BFR solution(20 mg/L)was completely faded with 1 g/L of AgBr-Ag3PO4/MWCNTs under visible-light irradiation for 10 min.TOC analysis showed that BFR was deep oxidized besides being decolorized.The 47%mineralization of BFR was achieved after 10 min irradiation of visible light.Ten recycling runs of AgBr-Ag3PO4/MWCNTs for BFR degradation displayed that it possessed good visible-light catalytic stability.The studies demonstrated that high visible-light photoactivity of AgBr-Ag3PO4/MWCNTs originated from outstanding conductivity of MWCNTs,matching potentials of conduction band-edge and valence band-edge between AgBr and Ag3PO4,as well as the plasma resonance effect of Ag generated during the photocatalytic process.Some intermediates such as 4,4’-diamino-3-methyl-benzophenone,4,4’-diamino-benzophenone,2-methyl-benzoquinone,4-aminobenzaldehyde,4-iminobenzoquinone and quinone were detected during the photocatalytic degradation of BFR.These were generated through electrophilic addition of hydroxyl radicals and further oxidation of h+ leading to double bond cleavage of the central carbon of BF and BR9.The heterogeneous visible-light materials of Ag3VO4/g-C3N4 were successfully fabricated via combining pyrolysis and precipitation method.They were used to eliminate BFR,MG and CV from aqueous solution.Among the heterogeneous materials,40 wt%g-C3N4/Ag3VO4 exhibited the optimal visible-light photoactivity for degradation of BFR.For 20 mg/L BFR solution,about 95%of BFR was decomposed over 40 wt%g-C3N4/Ag3VO4(1 g/L)with 2.5 h of visible-light irradiation.In addition,the heterogeneous material also displayed exceptional visible-light photoactivity for degradation of MG and CV,respectively.About 97%of MG(20 mg/L)was degraded using 1 g/L of 40 wt%g-C3N4/Ag3VO4 under visible-light irradiation for 1 h.After 2.5 h of visible-light irradiation,approximately 75%of CV(20 mg/L)was eliminated over 40 wt%g-C3N4/Ag3VO4(1 g/L).TOC analysis illustrated that this three dyes were deep mineralized over 40 wt%g-C3N4/Ag3VO4 by h+,·O2-1 and ·OH besides being faded.The mineralization rate of BFR,MG and CV is about 45%,53%and 34%under visible-light irradiation for 2.5 h,respectively.The 40 wt%g-C3N4/Ag3VO4 exhibited excellent stability for visible-light catalytic degradation of BFR,MG and CV by four recycling runs.The calculated results of band-edge potential indicated that the exceptional visible-light photoactivity of g-C3N4/Ag3VO4 was ascribed to matching potentials of conduction band-edge and valence band-edge between g-C3N4 and Ag3VO4.In addition,the plasma resonance effect of Ag generated under visible-light irradiation could maintain high photoactivity of 40 wt%g-C3N4/Ag3VO4.The bifunctional heterogeneous materials of BiOI/Ag3VO4 with adsorption and visible-light photoactivity were successfully prepared using a facile solvothermal method followed by the chemical precipitation.They were applied to remove BFR,MG and CV from aqueous solution.Among the heterogeneous materials,the 30 wt%BiOI/Ag3VO4 exhibited the optimal performance of adsorption and visible-light photoactivity.The removal of 25 mg/L of BFR,MG and CV over 30 wt%BiOI/Ag3VO4(1 g/L)was about 97%,92%and 85%,respectively,after the adsorption for 1 h and then visible-light degradation for 2 h.The 30 wt%BiOI/Ag3VO4 displayed good stability of adsorption and visible-light photoactivity for BFR,MG and CV removal by three recycling runs,respectively.The fitting results of adsorption kinetics and adsorption isotherm showed that the adsorption process of BFR,MG and CV on 30 wt%BiOI/Ag3VO4 followed the pseudo-second-order kinetic model and the Freundlich adsorption isotherm,respectively.The excellent performance of adsorption and visible-light photoactivity of BiOI/Ag3VO4 was attributed to larger BET specific surface area,mesoporous structure and work function of Ag<Ag3VO4<BiOI,as well as matching potentials of conduction band-edge and valence band-edge between BiOI and Ag3VO4-Under visible-light irradiation,Ag photogenerated electrons could transfer to Ag3VO4 and then to BiOI,which resulted in the composite photocatalyst with significantly enhanced reaction activity of visible light.