Simultaneous adsorption of malachite green, methyl orange, and rhodamine B with TiO 2 /macadamia nutshells-derived activated carbon composite

Abstract

Abstract In this study, TiO2/activated carbon (TiO2/MAC) composite was synthesized from activated carbon prepared from macadamia nutshells and a water-soluble titanium complex, and it was used to simultaneously adsorb malachite green (MG), methyl orange (MO), and rhodamine B (RhB) from aqueous solutions. The kinetic studies show that the adsorption experimental data are best described by the pseudo-second-order kinetic model. The equilibrium data of the trinary-component system were analysed via the models that combine the three single-component isotherms (Langmuir, Freundlich, Sips) into the ideal adsorption solution theory (IAST) and the Langmuir and P-factor-Langmuir extended models. The results obtained from the AICs (Akaike Information Criterion) indicate that IAST incorporating the Langmuir model is the most suitable to describe the removal of the dyes in the trinary component solution. The high maximum adsorption capacities, qe, in the single/trinary solution for MG, RhB, and MO are 0.318/0.241, 0.212/0.314, and 0.291/0.145 mM·g–1, respectively. The thermodynamic analysis reveals that the adsorption is spontaneous and endothermic. The results of material regeneration through photocatalytic self-cleaning show that TiO2/MAC can be utilized as a sustainable alternative for the simultaneous elimination of textile dyes from effluents.