STUDY ON PHOTOCATALYSIS-ULTRAFILTRATION REACTOR BY NANOPARTICLE TIO2 FOR DYES DEGRADATION
Jianfeng, F., Min, J., Luonan, J.
The College of Environmental Science and Engineering, Tianjin University
(free)
Dyes are organic compounds used in textile industries and their abatement represents one of the main problems in the treatment processes because they are very stable toxic compounds. In this work, acid blue 7 in aqueous solutions were degraded in a photocatalysis-ultrafiltration reactor by using special nanoparticle TiO2 as the photocatalyst. In this hybrid reactor, photocatalytic oxidation took place in an annular suspended photoreactor whereas the photocatalyst particles were separated from the wastewater by a cross-flow ultrafiltration unit. Air or industrial pure oxygen was continuously at a rate of 1 L/min supplied to provide O2 for the photocatalytical reaction and to mix the solution through an gas flow controller. In this paper, a kind of nanoparticle TiO2 photocatalyst was used instead of conventional Degussa P25 powder. This is because particle TiO2 can automatically settle by gravity without particle agglomeration so it can be easily separated by ultrafiltration membrane. What’s more, it is efficient to maintain high flux of membranes after gas backwashing and permeate backwashing.
The influence of operational parameters on the photocatalytic oxidation rate of acid blue 7 was investigated. The operational parameters included: cross-flow velocity, initial concentration, TiO2 dose, pH, dissolved oxygen. The experimental results showed a satisfactory degradation efficiency of the photocatalysis-ultrafiltration system. Results obtained from these studies indicated that photocatalytic oxidation rate of Acid Blue 7 can be expressed by the L-H kinetic model. The rate will increase from 0.0708 min-1 to 0.1515 min-1 with increasing cross-flow velocity ranging from 0.45 to 1.06 m/s. The optimum TiO2 dosing is 0.5g/L. Increase in the initial dye concentration from 5 to 25mg/l can decrease the degradation rate constant from 0.1625 to 0.053 min-1. Bubbled with industrial grade oxygen in the experiment has reached the best TOC removal results. The pH values have substantial effect on the degradation of Acid Blue 7, particularly at low pH value.
KEY WORDS Acid blue 7, nanoparticle TiO2, Photocatalytic degradation, Semiconductor Photocatalysis, Ultrafiltration, UV radiation
