Fixed-bed column studies for the removal of anionic dye from aqueous solution using TiO2@glucose carbon composites and bed regeneration study

Abstract

Glucose carbon with uniform diameter was successfully anchored by TiO2 nanoparticles via a facile low-temperature hydrothermal process independent of surfactants or external forces. The resultant TiO2@glucose carbon composite (TiO2@GCs) was characterized by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The elimination of direct deep blue (DDB) from aqueous solution by adsorption onto TiO2@GCs was investigated in the up-flow fixed-bed columns. The effects of the influent concentration (10–30 mg L−1), flow rate (3–5 mL min−1), bed depth (1.0–2.0 cm) and pH (1.0–9.0) were investigated. Breakthrough time and adsorption capacity of the fixed-bed increased with increasing bed depth, whereas decreased with the increase in initial concentration, bed depth and solution pH values. The experimental data was in good agreement with both Thomas model and Yoon-Nelson model. The employed bed saturated with DDB was readily regenerated through a simple regeneration process with UV irradiation for 1 h. Furthermore, the adsorption–regeneration process was conducted for six cycles and no major decrease of regeneration efficiency was observed for the first three cycles. One possible mechanism for regenerating dye-loaded TiO2@GCs was proposed. The verifying experiment found that hydroxyl radicals and superoxide ions significantly affected the regeneration of employed TiO2@GCs bed.