Simultaneous adsorption of malachite green, methyl orange, and rhodamine B with TiO2/macadamia nutshells-derived activated carbon composite

Abstract

In this study, TiO _2 /activated carbon (TiO _2 /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 pseudo-second-order kinetic model describes the adsorption experimental data the best. The equilibrium data of the trinary system were analyzed via the ideal adsorption solution theory (IAST) and the Langmuir and P-factor-Langmuir extended models that combine the three single-component isotherms (Langmuir, Freundlich, and Sips). The AIC _s (Akaike Information Criterion) values indicate that IAST incorporating the Langmuir model is the most suitable to describe the removal of the dyes in the trinary solution. The TiO _2 /MAC composite exhibits a high dye adsorption capacity compared with those of the published adsorbents. The thermodynamic analysis reveals that the adsorption is spontaneous and endothermic. The high adsorption capacity and the recyclability through photocatalytic self-cleaning show that TiO _2 /MAC can be utilized as a sustainable alternative for the simultaneous elimination of textile dyes from effluents.

Keywords

• ideal adsorption solution theory
• photocatalytic activity
• dyestuffs
• wastewater