Study On Removal Of Pollutants In Drinking Water By Solar Photocatalysis With Immobilized Catalyst

A novel pilot-scale solar photocatalytic reactor with immobilized catalyst wasdeveloped, where low concentrating compound parabolic concentrator was applied assolar collecting component, and immobilized TiO₂ membrane supported on glassfiber mesh with sol-gel method used as catalyst and cold cathode low-pressuremercury lamps used as assisting artificial UV source.The photonic collection efficiency factorφ_ef was estimated to be about 0.759 bypotassium ferrioxalate actinometries. And apparent quantum yield of phenoldegradation can reach up to 1/2 of that of slurry system. The photocatalyst supportedon glass fiber net can be reused in a rather long time. The new reactor, which treatedphenol and formic acid with high efficiency, can make all-weather stable operationwith good compatibility to different weathers.Phenol was used as model pollutant to evaluating the device performance. Thelimitation of mass transfer was diminished when the circular flux exceeded 5L/min.When initial concentration ranged from 1.8 to 7.5mg/L, the solar photocatalyticreaction followed apparent first-order kinetics, and the apparent kinetic constantsdecreased with the increase of initial concentration. The linear dependence betweenapparent reaction rate and radiation density flux was also found from 12.4 to 25.9W/m². Phenol removal under artificial UV radiation was the combined effects ofphotocatalysis as well as photolytic degradation.Inactivation characteristics of Escherichia coli were also studied by the newsolar photocatalytic reactor. Photocatalytic deactivation of Escherichia coli was aconsequence of the synergistic effect of the oxidant species generated by supportedTiO₂ and solar UV irradiation, and the disinfection efficiency of photocatalysis washigher than sunlight deactivation. Increasing flow rate and light intensity had positiveeffects on disinfection rate. ESEM examination indicated that bacteria cell waslethally destroyed by solar photocatalysis. No significant recovery or multiplicationwas observed during 8 hatter solar photocatalysis treatment. Photocatalytic degradation characteristics of bisphenol A (BPA) were explored.And experiment results indicated that BPA degradation was influenced significantlyby different light sources. BPA underwent insignificant photolysis under solarirradiation. At low initial concentrations, the apparent reaction kinetics was first orderwith respect to the concentration and the apparent kinetic constants decreased withthe increase of initial concentrations. Linear dependence between apparent reactionrate and radiation density flux was also found from 5.7 to 23.5 W/m². While underUV254, BPA underwent significant photolysis and the first-order kinetic constantsincreased with the increase of initial concentration. Solar photocatalysis couldmineralize BPA well, but the mineralization process differs greatly from that undershort wavelength UV. Several intermediates were detected by GC/MS analysis afterBSTFA-derivatization of intermediate samples.Semi-volatile organic pollutants in tap water could be purified well by the newphotocatalytic reactor under different irradiation. Under solar photocatalysiscondition, 18 trace semi-volatile organics among those 23 ones which were identifiedby GC/MS analysis were removed more than 50ï¼…, and 16 of them were evenlowered below detection limits. Common pollutants such as chloroform, phenol andBPA could also be removed well. Furthermore, bacteria in tap water were inactivatedsuccessfully while organic pollutants were removed. Solar photocatalysis techniquewith immobilized catalyst is promising in tap water purification.