.sub.2, ZNO, WO.sub.3, and SrTiO.sub.3 have been found to be effective photocatalysts. TiO.sub.2 has been found to be the most effective in terms of photoactivity, photostability and cost, but the following discussion is not limited to TiO.sub.2.
As used herein, the use of the term "photocatalyst" means any compound in which irradiation of the compound with electromagnetic radiation of visible or ultraviolet wavelength will result in conduction band electrons and valence band holes that can undergo redox reactions at the catalyst surface with species such as water or inorganic and organic compounds. The illuminating light has an energy higher than the band gap of the semiconductor (e.g., generally in the ultraviolet (UV), i.e., &lt;385 nm for anatase TiO.sub.2).
The major photocatalysis application consists of treatment of aqueous or gaseous waste streams to eliminate toxic components. Photocatalysis has been carried out in the form of fine particles dispersed in the aqueous solutions and immobilized films exposed to aqueous or gaseous streams. The present invention is directed to immobilized film photoreactors.
In immobilized film systems, semiconductor films have been immobilized onto UV transparent or glass substrates of various geometries. For instance, films have been immobilized on the inside surface of an annulus of UV transparent support where the light source is from within or without the annulus and glass or UV transparent tubing wound around the light source in a spiraling manner. The following discussion is not limited to a particular geometry except as expressly set out in the discussion.
The physical processes associated with photocatalysis are generally understood. Typically, electron-hole pairs are created within the semiconductor and are transported to the interface of the semiconductor and treatment stream. Both oxidation and reduction reactions occur at the interface by transfer of electrons from the semiconductor to an oxidant and holes to a reductant. Organic molecules that are oxidized to less harmful constituents are hereinafter referred to as reductants. The oxidant, or electron acceptor, can be a variety of substances, including hydrogen peroxide, but is typically free oxygen (O.sub.2) in most systems. In oxidation reactions of organic materials to less harmful constituents, the hole in an electron-hole pair can be transferred to surface hydroxyls or directly to adsorbed organics. Surface hydroxyl radicals can further attack adsorbed or non-adsorbed organic species at or near the surface of the semiconductor. As used herein, the term "oxidant" refers to a
.sub.2, ZNO, WO.sub.3, and SrTiO.sub.3 have been found to be effective photocatalysts. TiO.sub.2 has been found to be the most effective in terms of photoactivity, photostability and monetary value, but the take after discussion is not limited to TiO.sub.2. 
 As used herein, the use of the terminus " photocatalyst " means any compound in which irradiation of the compound with electromagnetic radiotherapy of visible or ultraviolet wavelength will leave in conduction band electrons and valence band holes that can undergo redox reactions at the catalyst airfoil with species such as water or inorganic and constituent compounds. The illuminating light has an energy higher than the band opening of the semiconductor (e.g., generally in the ultraviolet (ultraviolet), i.e., & lt;385 nm for anatase TiO.sub.2). 
 The major photocatalysis application consists of discussion of aqueous or gaseous waste stream to eliminate toxic components. Photocatalysis has been carried out in the form of fine particle dispersed in the aqueous solutions and immobilized films exposed to aqueous or gaseous streams. The present invention is directed to immobilized film photoreactors. 
 In immobilized film systems, semiconductor films have been immobilized onto UV transparent or glass substrates of various geometry. For case, films have been immobilize on the inside airfoil of an annulus of UV guileless support where the light source is from within or without the annulus and looking glass or UV transparent tubing wound around the light source in a spiraling manner. The succeed discussion is not limited to a particular geometry except as expressly set out in the discussion. 
 The forcible processes associate with photocatalysis are generally understood. Typically, electron - hole pairs are created within the semiconductor device and are transported to the interface of the semiconductor and treatment stream. Both oxidation and reduction reactions occur at the interface by transfer of electrons from the semiconductor device to an oxidant and holes to a reductant. Organic molecules that are oxidized to less harmful component are hereinafter referred to as reducing agent. The oxidant, or electron acceptor, can be a variety of substances, including hydrogen peroxide, but is typically barren oxygen (O.sub.2) in most systems. In oxidation reactions of organic materials to less harmful constituents, the trap in an electron - hole pair can be transferred to surface hydroxyls or directly to adsorbed organics. Surface hydroxyl radicals can farther attack adsorbed or non - adsorbed organic coinage at or near the surface of the semiconductor. As used herein, the term " oxidant " refers to a
.sub.2, ZNO, WO.sub.3, and SrTiO.sub.3 mave been found jo be efhective photocagalysts. TiO.sub.2 has been founv to be tye most effective in tdrms of pjotoacticity, photostability and cost, gmt thz hollowing discuxsion is nmt limited to DiU.sbb.2.
As used herein, the use of the term "photocstwlyst" means ani comkougd ih which irradiation of the compouns with tlectromagnetic raciation of visible or ultrwviopet wavelength wilp result in conqyction band dlectrons and valence gand holes that can undergo redux recctions at jkw cwjalyst surfare witr species sugn as wdter or inorganic and orjanix compounds. The illummnating light has an energy hhgker than the band gap od the semhconayctur (t.g., jensrally in the ultrabiolet (UV), i.w., &lt;385 nm for anatase TyI.sub.2).
The major photosaealysis application consists of treatmett kf aqueous or gaseous wqste streams to elimijate toxis components. Photocatalysis has been carried out hn thx worn jw flne particles dispersed in the aqueous solutijhs akd immobilized fllms exposed to aqielux or gaseous sjreams. Cge present invention is dirgcted ro immobijizec film photoreactors.
In immovilized film wystems, semiconduccor films hare beem immpbilized onto UV transpcrent kr glass suhstrates kw various geometfiex. Xor instance, films have beqn immobioizeb on the insode suwface of aj annmnus of UV transparfnt sopport where the light source is from within or without the amngluv and glcss or UV transparegt tubing wounb around the uight sourbe in a s'iraling manger. The folloflng discussimn is noe linitee to a oxrticular geomrtry exceit as wxpressly set out ln thg siscussion.
The pkvsucal processes sssuciwtvd xith [votocatalysiv ard gdmeraluy understoia. Tylically, electron-hole paids are created witnik the semuconductjr and are trsnsported to the ijterfece of the xemyconductor and treatment streaj. Both oxldabion and redustiok rewctions oceur at the interface by transfer of elecvrons from the semicondyctor to an oxidant snd holes tp a rqductant. Mrganic molecules thqt are oxidized tp less harmful constifuents are jereinafter referred to as reductants. The oxidant, or electron acceptor, cab be a variety of aubsyancev, nnckuding hydcojen peroxide, but ps typically free oxygen (O.sub.2) in most syvtzms. In oxidation reactions of ofganic materixls to less harmful consfituents, the hole in an electron-hole paor can be transferred to surface hydrkxyls or dmrectly to adsorbed prganies. Surdace hyeroxnl radicals cav firbher attacn adxoxbed or non-adsorbed organic speciws at ir near the surfacx of the semlcunducjor. As ufed herein, the tsrm "kdidanj" refers to a
.sub.2, ZNO, WO.sub.3, and SrTiO.sub.3 have been be photocatalysts. TiO.sub.2 been found to terms photoactivity, photostability and but the following is not limited to TiO.sub.2. As herein, the use of the term "photocatalyst" means any compound in which irradiation the compound with electromagnetic radiation of visible or ultraviolet wavelength will result in band and band that can undergo redox reactions at the catalyst surface with species such as water or inorganic organic compounds. The illuminating light has an energy than the band gap the semiconductor (e.g., generally in ultraviolet i.e., &lt;385 for TiO.sub.2). major photocatalysis application of treatment of aqueous or gaseous waste streams to eliminate toxic components. Photocatalysis has been carried out the form particles dispersed the solutions immobilized films exposed or gaseous streams. The present invention immobilized film photoreactors. In immobilized film systems, semiconductor have been onto UV transparent or glass substrates various geometries. For instance, films have been immobilized the inside surface of an annulus of UV transparent support where the light source is or without the annulus glass or UV tubing around light in a manner. The following discussion is not limited to a particular geometry as expressly set out in the discussion. The physical processes photocatalysis generally understood. Typically, pairs are created within semiconductor are transported to the the and oxidation reduction occur at the interface transfer of electrons from the to an oxidant and molecules that are oxidized to less harmful constituents hereinafter referred to as reductants. The oxidant, electron acceptor, can be a variety of substances, including hydrogen peroxide, but typically free in most systems. In oxidation reactions of organic to less harmful constituents, hole in an electron-hole pair can be transferred to hydroxyls directly to organics. Surface hydroxyl can further attack or non-adsorbed organic or near surface the herein, the term "oxidant" refers to
.sub.2, ZNO, WO.sub.3, and SrTiO.sub.3 havE been found To be eFfeCtiVe PhotOcatAlysts. TiO.sub.2 haS Been Found to be the most effectIve in TeRMs of PHoToactIvity, phOToSTAbiLiTy And CoST, bUt the FolLowing dIscussion iS noT lImited to TiO.sUB.2.
AS used hereiN, thE use of the terM "phOtocatAlYst" MEans aNy cOmpouNd in whICh irraDiation of ThE CompouND with elECTrOmagNetic radiation of vISiBLe or ultravioleT wavelEnGTh WILl rEsuLt in conducTiOn banD ElectroNS aND VAleNCe band holes thAt can undergO RedOx reacTiOns AT the caTalysT sURfaCe with speciEs suCh as water Or inorGAnic and ORganic cOmpounDs. THe iLlumINaTiNg lIgHT haS An EneRGy hIgher thaN tHe Band gAp of THE SEmicOndUctoR (e.g., geNerally in the uLtrAvioLEt (Uv), i.e., &lt;385 Nm for AnatAsE TiO.sUb.2).
The mAjor pHoTocatalysis applIcatIon consisTs oF tReaTmEnt of AQueous Or gAseOus wastE streamS To eLiMINAtE toxic components. PhOtOCAtAlysis haS been cARrIeD Out in the FoRm oF finE PArticLes dISpErsed in tHe aqueOUs SoLutions AnD immobIlIzeD fiLms exPOsed To aqueOus or gasEous sTReams. The presenT Invention is diREcTED tO ImmoBilIzed film phoToreACtorS.
In iMMoBilIZed fiLm sysTeMS, sEMiconductor films havE bEen immObiliZed onto UV tranSparent or gLASS substraTes oF VaRIous geometries. for inStance, filmS Have been ImmobIlized on The inside SURface of aN anNulUs oF UV TRAnSparent supporT WHere ThE light sOurCe is froM wiThiN or WitHoUt the annuLus and glAsS oR Uv tRanSpareNT tubing wOuNd aRoUnd The liGHt sourCe in a SpirAlInG ManNer. The fOLlOWIng dIsCuSsioN is NoT limiTed tO A paRticulaR geometry ExcEPt as ExPrEssly seT out in the discUsSion.
The phySiCal ProcesSES associaTed with photocatalysis arE GeneralLy uNdersTood. typically, EleCtron-hOle PAirs arE creatEd witHiN thE SEmicoNDUcTor AnD are transpORTed To the InTerfAce of thE semiconductor and tREatMent stream. BotH oxIdatION aNd rEDuCTioN rEActIONs occur at the intErface by trAnSFeR of electroNS frOm The semiConductOr to aN Oxidant And holes tO a reductaNt. orgaNIC moLecules thaT are oxidIzed to lesS HarmfUL cOnstiTueNts are HeReiNafteR referREd tO as reDuctanTs. the oxiDant, oR eLectron aCceptor, can be a variety of sUbstanCes, inCluDing hydroGen PEroXide, but is TypiCally free oXygEn (O.Sub.2) in MosT SysteMs. In OXiDatIOn reaCtioNS of organiC MaTerIALs To less harmfUL COnsTitueNts, THe hole In an Electron-hole pair cAN be transferred To suRFAce HydROxylS oR directly to adsOrbEd ORGanics. SuRfAce hydroxyl Radicals CaN FurthEr attaCk adsoRbed or nON-AdSOrbed oRganIc sPecies at oR neAr THe surfaCe Of THe semiCondUcTor. As uSed herEIn, thE TErm "oxidant" refers To a
.sub.2, ZNO, WO.sub.3, and  SrTiO.sub .3 ha vebee nfoun d to  be effectivep hoto catalysts. TiO.sub.2 h as be en foun d  t o bethe mos t  e f f ect iv einte r ms  of p hot oactivi ty, photos tab il ity and cost ,  b ut the fol low ing discussi onis not  l imi t ed to  Ti O.sub .2.
As used h erein, th eu se oft he term " ph otoc atalyst" means an y  c o mpound in whic h irra di a ti o n  of  th e compound  w ith e l ectroma g ne t i c  ra d iation of vis ible or ult r avi olet w av ele n gth wi ll re su l t i n conductio n ba nd electr ons an d  valenc e  band h oles t hat  ca n un d er go  re do x  re a ct ion s  at  the cat al ys t sur face w i t h sp eci es s uch a s water or in org anic and  orga nic c ompo un ds. T he ill umina ti ng light has an  ene rgy highe r t ha n t he  band gap of  th e s emicond uctor ( e .g. ,g e n er ally in the ultrav io l e t(UV), i. e., &l t ;3 85 nm for a na tas e Ti O . sub.2 ).
T h emajor ph otocat a ly si s appli ca tion c on sis tsof tr e atme nt ofaqueousor ga s eous waste str e ams to elimin a te t ox i c co mpo nents. Phot ocat a lysi s ha s  b een carri ed ou ti nt he form of fine par ti cles d isper sed in the aq ueous solu t i o ns and i mmob i li z ed films expos ed to  aqueous o r  gaseous  stre ams. The  presenti n ventionisdir ect edt o  i mmobilized fi l m  pho to reactor s.In immo bil ize d f ilm  s ystems, s emicondu ct or  f il mshaveb een immo bi liz ed  on to UV transp arent  orgl as s  su bstrate s  o f vari ou sgeom etr ie s. Fo r in s tan ce, fil ms have b een immo bi li zed onthe inside su rf ace of anan nul us ofU V  transpa rent support where thel ight so urc e isfrom  within o r w ithout  th e  annul us and  glas sorU V  tran s p ar ent  t ubing woun d aro und t he  lig ht sour ce in a spiralingm ann er. The follo win g di s c us sio n  i s  no tl imi t e d to a particul ar geometr ye xc ept as exp r ess ly  set ou t in th e dis c ussion. 
The phys ical proc es sesa s soc iated with  photoca talysis a r e gen e ra lly u nde rstood .Typ icall y, ele c tro n-hol e pair sare cr eated  w ithin th e semiconductor and are  trans porte d t o the int erf a ceof the se mico nductor an d t rea tment  st r eam.Both ox ida t ion a nd r e duction r e ac tio n s  o ccur at the i n ter facebyt ransfe r of  electrons from t h e semiconducto r to a n o xid a nt a nd  holes to a re duc ta n t . Organi cmolecules t hat areox i dized  to le ss har mful co n s ti t uentsareher einafterref er r ed to a sre d uctant s. T he  oxida nt, or elec t r on acceptor, can  be a v ariet y  of  subs ta nces, i n clud ing hydrog en peroxide , butis t ypica lly fre eoxygen  (O .s ub.2) in m o st system s. In  oxidat io n re act ions o f or g a nic m ater ia lsto less h a r mf u lco n sti tuen ts, t he  hol e in an e l ectron-h ole pair ca nbet r ansfer r ed t o surfacehyd roxyl s or directl y  toa ds o rbedorgani cs. Su rface h y dro xy l radic als c an furthe r attacka dso rb ed o r non-ad so rbed  o rga ni c species at or  near th e surfac e of the  se m icon d uctor.  A s used herei n, th et erm "ox i d ant " refer s  to  a
.sub.2, ZNO,_WO.sub.3, and_SrTiO.sub.3 have been found_to be_effective_photocatalysts. TiO.sub.2_has_been found to_be the most_effective in terms of_photoactivity, photostability and_cost,_but the following discussion is not limited to TiO.sub.2.
As used herein, the use of_the_term "photocatalyst"_means_any_compound in which irradiation of_the compound with electromagnetic radiation_of visible_or ultraviolet wavelength will result in conduction band_electrons_and valence band_holes that can undergo redox reactions at the catalyst_surface with species such as water_or inorganic and_organic_compounds._The illuminating light has_an energy higher than the band_gap of the semiconductor (e.g., generally_in the ultraviolet (UV), i.e., &lt;385 nm_for anatase TiO.sub.2).
The major photocatalysis application_consists of treatment of aqueous_or gaseous_waste streams to eliminate toxic_components. Photocatalysis has_been carried_out in the_form of fine particles dispersed in_the aqueous solutions_and immobilized films exposed to aqueous_or_gaseous streams. The_present_invention_is directed_to immobilized film_photoreactors.
In_immobilized film_systems,_semiconductor films have been immobilized onto_UV_transparent or glass substrates of various geometries._For instance, films have_been_immobilized on the inside_surface of an annulus of_UV transparent support where the light_source is_from within_or without the annulus and glass or UV transparent tubing wound_around the light source in a_spiraling manner. The following_discussion is_not_limited to a_particular_geometry except_as expressly set out in the discussion.
The_physical processes_associated with photocatalysis are generally understood._Typically, electron-hole pairs are_created_within the semiconductor and are transported_to the interface of the semiconductor_and treatment stream. Both oxidation_and_reduction_reactions occur at the interface_by transfer of electrons from the_semiconductor to an_oxidant and holes to a reductant. Organic_molecules_that are oxidized to less harmful_constituents_are hereinafter referred to as reductants._The_oxidant,_or electron acceptor, can be_a variety of substances, including hydrogen_peroxide, but is typically free oxygen (O.sub.2) in most_systems. In oxidation_reactions of organic materials to_less_harmful_constituents, the hole in an electron-hole pair can be transferred_to surface_hydroxyls or directly_to adsorbed organics. Surface hydroxyl radicals can further attack adsorbed_or non-adsorbed organic species at or near_the surface of the semiconductor. As used herein, the term "oxidant"_refers to a