A review of solar and visible light active TiO2 photocatalysis for treating bacteria, cyanotoxins and contaminants of emerging concern

Abstract

Researchintothedevelopmentofsolarandvisiblelightactivephotocatalystshasbeensignificantlyincreased inrecentyearsduetoitswiderangeofapplicationsintreatingcontaminantsofemergingconcern(CECs), endocrine disruptingcompounds(EDCs), bacteriaandcyanotoxins.Solarphotocatalysisisfoundtobehighly effectiveintreatingawiderangeofCECsfromsourcessuchaspharmaceuticals,steroids,antibiotics,phthalates, disinfectants,pesticides,fragrances(musk),preservativesandadditives.Similarly,anumberofEDCsincluding polycyclicaromatichydrocarbons(PAHs),alkylphenols(APs),bisphenolA(BPA),organotins(OTs),volatileor- ganic compounds(VOCs),naturalandsyntheticestrogenicandandrogenicchemicals,pesticides,andheavy metalscanberemovedfromcontaminatedwaterbyusingsolarphotocatalysis.Photocatalysiswasalsofound effectiveintreatingawiderangeofbacteriasuchas Staphylococcusaureus,Bacillussubtilis,Escherichiacoli, Salmonellatyphi and Micrococcuslylae. Thecurrentreviewalsocomparestheeffectivenessofvariousvisible lightactivatedTiO2 photocatalystsfortreatingthesepollutants. Dopingorco-dopingofTiO2 usingnitrogen, nitrogen–silver,sulphur,carbon,copperandalsoincorporation ofgraphenenano-sheetsarediscussed.Theuse of immobilisedTiO2 for improvingthephotocatalyticactivityisalso presented.Decoratingtitaniaphotocatalyst withgrapheneoxide(GO)isofparticularinterestduetoGO'sabilitytoincreasethephotocatalyticactivityof TiO2. TheuseGOtoincreasethephotocatalyticactivityofTiO2 againstmicrocystin-LR(MC-LR)underUV-Aand solarirciationisdiscussed.TheenhancedphotocatalyticactivityofGO–TiO2 comparedtothecontrolmaterialis attributedtotheeffectiveinhibitionoftheelectron–holerecombinationbycontrollingtheinterfacialcharge transferprocess.Itisconcludedthatthereisacriticalneedforfurtherimprovementoftheefficiencyofthese materialsiftheyaretobeconsideredforbulkindustrialuse.