Activated carbon, zeolite, and ceramics immobilized TiO₂ photocatalysts for the enhanced sequential uptake of dyes and Cd²⁺ ions

Abstract

The post-reaction separation in heterogeneous catalysis always remained a point of concern for nanoparticle application in an aqueous medium. This study corroborates the immobilization of TiO₂ nanoparticles (NPs) on various solid supports such as activated carbon (AC), zeolite (Z), and ceramics (CCTO) materials. Economically viable and facile impregnation methods were employed to obtain a high mass yield (up to 95%) of immobilized TiO₂ NPs. The characterizations of tailored materials were performed by using XRD, BET, UV-Vis DRS, SEM, and pH of the point of zero charges (pHpzc) analyses. The immobilization of TiO₂ NPs significantly altered the physicochemical properties and ultimately enhanced the photocatalytic activities under ordinary compact fluorescent light (CFL). To investigate the photocatalytic performance of immobilized materials, model dyes e.g., Methyl Orange (MO) and Methylene Blue (MB) were considered in addition to the heavy metal ions i.e., Cd²⁺. The immobilization of TiO₂ on solid supports revealed better performance for all tshree systems; whereby the AC@TiO₂ exhibited higher efficiency as compared to the counterparts i.e., Z@TiO₂ and CCTO@TiO₂. In binary solutions (MB:Cd²⁺ and MO:Cd²⁺), the synergistic effect of the photo-generated positive hole scavenger (MB) and electron trapper (Cd²⁺) further enhances the removal efficiencies. The regeneration studies showed similar performance as that of the fresh samples, whereby the photocatalytic efficiencies were found to decrease for the consecutive cycles.

Graphical Abstract

The immobilization of titania NPs on various solid supports such as activated carbon, zeolite, and ceramics revealed the better photocatalytic performances of the immobilized materials. Moreover, the immobilization affected the bandgap energies for better photocatalytic performances under visible light.

Keywords:

• Photocatalysis
• TiO₂ immobilization
• activated carbon
• zeolite
• ceramic

Acknowledgments

The authors would like to acknowledge the grant RUI No. 1001/PKIMIA/815099 for the equipment and financial funding by Universiti Sains Malaysia (USM). Furthermore, N. S. is also grateful to TWAS (The World Academy of Sciences) & USM for granting TWAS–USM Fellowship to tail this study.