Evaluation of a novel Carberry type photoreactor for the degradation of organic pollutants in water

The major drawback of slurry-type photoreactors is the final particle–fluid separation for the catalyst recycling. If a catalyst (e.g. TiO2 for oxidative mineralisation of pollutants) is immobilized on a rigid support as a thin film, such problem is avoided. Unfortunately, as the reaction occurs at the liquid–solid interface, the overall rate is much lower in thin-film reactors than in the corresponding slurry systems. Our goal was to design a laboratory-scale batch photoreactor, which would combine the advantages of slurry and immobilized photocatalytic systems: (i) high ratio of illuminated immobilized catalyst surface to the volume of reaction liquid inside the reactor; (ii) high degree of mixing; (iii) possibility of installing the reactor into the compound parabolic collectors that utilize solar energy. The glass tube with the spinning basket inside (up to 12 glass slides of immobilized catalyst are positioned radially around the central axis) meets these criteria. Degussa P25 TiO2 or sol–gel produced TiO2 was immobilized on sodium glass support and the disappearance of 4-chlorophenol in water was monitored by HPLC analysis. Low-pressure mercury fluorescent lamps with broad maximum at 355 nm were used as a UVA radiation source. The optimal catalyst concentration in the photocatalytic experiments was 800 mg L−1 (regardless of the slurry or immobilized system). It was also estimated that the configuration of a novel Carberry type photoreactor with 12 fastened TiO2 slides shows nearly 4 times (3.8 times) higher photocatalytic activity compared to the configuration with two TiO2 slides (with the comparable surface density of immobilized TiO2), serving as an approximation of a classic plain thin-film fixed-bed reactor. On the other hand, the activity of our novel thin-film based reactor is still almost twice (1.8 times) lower than the activity of a slurry reactor (Degussa P-25 catalyst in both cases), which is still a very promising result.