Photocatalytic Degradation Of Some Typical Organic Pollutants In Drinking Water --a Study On Affected Factors And Degradation Mechanism

The trace organic pollutants in drinking water are one of the most importantfactors for affecting water quality. Photocatalytic oxidation has a good effects to getrid of organic pollutants in water, it can be turned into inorganic matter after persistentreaction and dont have second times pollutants. The photocatalytic degradation ofhexachlorobenzene,phenanthrene. trichloromethane,Aroclor1260,trichlorphonand humic acid in TiO₂ powder suspensions by some factors had been studied. Thesefactors were pH, Al³⁺,Fe³⁺,Fe²⁺,Mn²⁺,H₂O₂,dosage of TiO₂ and loading silver,initial concentration of reaction solution. The products of photocatalytic degradationwere identified with GC/MS and measured, so as to discuss the mechanism ofphotocatalytic degradation. The main conclusion as follows:(1) Quantitative analysis of trace polycyclic aromatic hydrocarbons in drinkingwater with C₁₈-solid-phase extraction-GC/MS was established for the first time.(2) Catalysts dose have an optimum value for different compounds and reactivesystem. The optimum value for hexachlorobenzene,phenanthrene,trichlorphon,trichloromethane and Aroclor1260 were 5g/L,3g/L,4g/L,3g/Land 4g/L respectivelyon the experimenis.(3) With the amount of loading silver increasing, the rate of photocatalyticdegradation of organic matter increased too. Loading silver isnt in proportion tocatalytic activity of TiO₂ by further research. with the loading silver increasing, theenhancement degree of catalytic activity of TiO₂ decreased.(4) Both Al³⁺ and Fe³⁺ could enhance the rate of photocatalytic degradation, butthe amount of casting isn't in proportion to enhancement of photocataiytic degradationrate. Al³⁺ could enhance the rate of photocatalytic degradation ofhexachlorobenzene,phenanthrene,trichloromethane and Aroclor1260 more than Fe³⁺did, which was conducted for the first time.(5) Low concentration of Fe²⁺ al1d Mn²⁺ could enhance photocatalytic degradationof trichloromethane, Aroclorl260 and l1UI11ic acid. but when the conceniration of Fe2+and Mn2' was high, it couId prevent photocataIytic degradation.(6) Humic acid. trichloromethane. pl1el1anthrene and Aroclorl260 were easilydegraded on acid condition, pII value didl1 t greatly affect photocatalytic degradationof hexachlorobenzene and trichlorphon.(z) The innuence of H,o, fOr photocataIytic degradation depended on castingdose.A little amount of H,O, couId enhance the rate of photocatalytic degradation, buta little more could prevent the rate ofphotocatalytic degradation.(8) The course of phOtOcataIytic degradation was different fOr differeni organicpollutants. The experiment o11 photocatalytic degI.adation of trichlorphon was done forthe first time. First, trichlorPl1on was turned int() dimethylpl1osphonic acid ester. thenturned into inorganic phosphorus (PO."). 1'he first cotIrse was fast, the second coursewas sIow; phenanthrene was turl1ed into 4-I1ydro- I,2-benzenedicarboxylic acid, at last,it was turned into CO, and H,O: trichIoIDmetl1ane' Aroclorl260 andhexachlorobenzene were gradually dechlorinated and turned into chlorine ion underthe photocatalytic degradation.The results enrich the theory of photocatalytic techllique, furthermore, it lay afoundation fOr the technique appIying to drinking water deep treatment.