Experimental design for optimization of the photocatalytic degradation process of the remazol red dye by the TiO₂/expanded perlite composite

In this study, the photocatalytic decolorization of remazol red dye (RR) was evaluated using TiO₂ based composites supported on the expanded perlite (T-EP-10% and T-EP-30%). The characterization techniques used in this work were IR, XRD, XRF and particle size analysis. In order to optimize the RR discolouration process, a factorial planning was applied. The best experimental conditions are the RR initial concentration of 10 mg L^-1, composite T-EP-30% and both PHs showed positive results in the decolorization. The tests performed at pH 2.0 showed 100% removal of RR colour in 180 min and at pH 5.0 100% colour removal was obtained in 120 min. The decolorization process follows a pseudo first-order-kinetics, the k_app of 0.01191 min^-1 for the tests at pH 5.0 and 0.00812 min^-1 for the tests at pH 2.0. The results of energy cost shown that in both pH 2.0 and 5.0 tests were feasible in efficiency and economically. The energy consumption for the test at pH 2.0 was 0.297 kWhdm³ and final cost of R$ 0.163, while the energy consumption for the test at pH 5.0 was 0.198 kWhdm³ and a final cost of R$ 0.111.