Comparison of the photocatalytic efficiencies of continuous stirred tank reactor (CSTR) and batch systems using a dispersed micron sized photocatalyst

Abstract

Photocatalysis is an advanced oxidation process which can be used for water purification. Studies on Plug Flow Reactor (PFR) and Continuous Stirred Tank Reactor (CSTR) systems are imperative if photocatalysis is to be used in large-scale applications. Between them, the CSTR system is an obvious choice for studies, because a series of CSTRs is equivalent to a PFR. However, a CSTR often imposes the use of fixed-bed reactors, which dramatically reduces the efficiency of the process. In this work, a dispersed photocatalyst system was combined with CSTR in order to develop an efficient system for continuous operation. We have overcome the problems of filter blockage, the need for premixing and catalyst retrieval at the end of the reaction using micron-sized photocatalyst powder and short sonication time carried out every 30 minutes. Two model pollutants (metanil yellow and rhodamine B) were used for the degradation studies. Variables such as flow-rate, pollutant, and catalyst concentration were also investigated to evaluate the CSTR performance. The results showed that the CSTR system could lead to an increase in degradation of up to 110%, compared to a batch system, and to a continuous operation longer than 42 h without filter blockage or deactivation of the catalyst.