Removal of dyes by an integrated process coupling adsorption and photocatalysis in batch mode

Abstract

This work deals with an integrated process, coupling adsorption with photocatalysis for removal of two basic dyes, basic yellow 28 (BY28) and basic blue 41 (BB41). In a first step, adsorption of the two dyes by activated carbon prepared from wild olive stones (AC-WOS) prepared from wild olive stones was investigated in batch mode for single and binary systems. The effects of pH, amount of adsorbent, temperature, and initial concentration on adsorption kinetics and equilibrium, for both single and binary mixtures, were investigated. A first-order derivative spectrophotometric method was used to analyze BB41 and BY28 in binary solutions. The mono and multi-component Langmuir and Freundlich isotherm models were applied to the experimental data and the corresponding constants were calculated. The maximum adsorption capacities of BB41 and BY28 were, respectively, 286.532 and 118.203 mg g−1 for single systems and 380.228 and 82.101 mg g−1 for binary systems. The rate of adsorption follows pseudo-second order kinetics. The thermodynamics constants ΔH ads, ΔS ads, and ΔG ads were evaluated. The results showed that adsorption from a single solution is endothermic and spontaneous. AC-WOS was used as post-treatment and adsorption was coupled with light-driven catalysis over the hetero-system CuFeO2–ZnO. Significant degradation of BB41 and BY28 in single solutions was achieved after ~2 h under optimum conditions.