The Preliminary Study Of A Combination Of Photocatalytic Technology And Bio-trickling Filter Process On Degradation Of Chlorobenzene

A combination of photocatalytic technology and biological trickling filter treatment process is an emerging and efficient technology in processing VOCs, particularly in refractory organics. It is paid more and more people’s attention.This paper shows that a study on degradation of chlorobenzene by photocatalytic technology, as well as the combination of this technology and biological trickling filter treatment process. In the separate photocatalytic apparatus, a certain concentration of chlorobenzene gas was piped in different levels of TiO2catalyst respectively, and meanwhile photocatalytic oxidation chlorobenzene of a ultraviolet(abbreviation-"UV") lamp opened was in progress. The results showed that the optimum efficiency of the catalytic oxidation reached94%which the concentration of TiO2catalyst was15%. An experiment with two different kinds of reaction medium, air and nitrogen, showed that using air as a reaction medium the photocatalytic process got the chlorobenzene degradation rate of58%to95%, but the nitrogen reaction medium42%～60%under the same conditions of retention time(RT), light intensity and temperature. It turned out that a reaction medium which had stronger oxidizing power and higher photocatalytic activity were conducive to photocatalytic process to produce more free radicals made the photocatalytic oxidation’effect better. It was also known that using air as the reaction medium when the concentration of chlorobenzene gas passed into photocatalytic apparatus were not higher than7.1mg/L, the apparatus could maintain high-efficiency removal of chlorobenzene. However, when the chlorobenzene concentration increased to12.2mg/L the removal rate rapidly decreased from80%to52%.In terms of removing chlorobenzene gas it is known that a combination of photocatalytic technology and bio-trickling filter process shows a high-efficiency processing power. Many factors can affect the efficiency of the combined system to remove chlorobenzene. Experiments by immobilized PVA-SA beads and traditional ceramic pellets as a bio-trickling filter packing respectively, suggested that the bio-trickling filter which used PVA-SA beads as packing would achieve stable effect of chlorobenzene degradation after domesticating and culturing biofilm in24days. And the other one which used ceramic pellets would take approximately27days to reach steady degradation efficiency. After domesticating and culturing bio film successfully the chlorobenzene gas flow rate of4L/min flew through two combination system, in other words, their total retention time were both about116s.By adjusting for different inlet chlorobenzene load and comparison of removal chlorobenzene load of two combination, the result showed that when the inlet chlorobenzene load was not greater than9.0mg/(L· min) the removal load of two combination systems were very close to the inlet load, and both degradation rate of chlorobenzene were more than90%.When the inlet load increased12.2mg/(L·min) the removal chlorobenzene load of a combination which used PVA-SA beads packings was in equilibrium at11.3mg/(L· min), and the removal load of the other combination which used ceramic packings was in equilibrium at9.5mg/(L· min).It indicated that the two combination systems were both close to their limit remove loads. Meanwhile, under the conditions of different retention time, It was researched that the two combined system’removal rate of different concentrations of chlorobenzene gas and founded the retention time had an important impact on the degradation of high concentrations of gas.