Cu-impregnated zeolite Y as highly active and stable heterogeneous Fenton-like catalyst for degradation of Congo red dye

Abstract

Abstract Several Cu/zeolite Y catalysts were prepared by wet impregnation method and tested for the decolorization, degradation and mineralization of recalcitrant diazo dye (Congo red) in heterogeneous Fenton-like process. The synthesized catalysts were characterized using XRD, N 2 sorption, FESEM, FTIR, UV-DRS and XPS techniques in order to study the influence of copper loading on structure, texture and electronic states of copper. Particularly at Cu loading of 7.5 wt%, zeolite Y exhibited the highest surface area, hierarchical porosity and the highest amount of well-dispersed Cu 1+/2+ species. The partial auto-reduction of Cu 2+ to Cu 1+ species was observed for all the samples; however, CuO crystallized out majorly for 10 wt% copper loading. The effects of major parameters, such as copper loading, initial pH, H 2 O 2 concentration, catalyst dose and temperature were studied on the activity as well as copper leaching from catalyst. The maximum degradation, decolorization and mineralization of 93.58%, 95.34% and 79.52% were exhibited by Cu 7.5 wt% after optimum times of 2.5, 2 and 4 h, respectively. It was also observed that H 2 O 2 had almost negligible effect on copper leaching. However, a strong influence of pH was noticed with maximum copper leaching of 13.85 mg L −1 at pH = 5. The kinetic studies revealed that the degradation and decolorization profiles are well fitted by the first-order kinetic model. Catalyst with 7.5 wt% copper loading showed reproducible activity up to 3rd cycle. The XRD patterns, textural properties and FTIR spectra of the used catalysts were compared with fresh catalyst to demonstrate the framework stability.