TiO2/Kaolin composite as low-cost adsorbent for procion red removal from aqueous solution: kinetics, equilibrium, and thermodynamic studies

ABSTRACT . Procion red is one of the most utilized textile dyes by numerous textile factories worldwide. Unfortunately, it has a detrimental effect on the ecosystem whenever it was released into the environment as textile wastewater. In this work, the removal of procion red from aqueous solution has been conducted by adsorption with modified natural kaolin as a low-cost adsorbent. Kaolin was systematically modified by thermal activation then followed by acid activation in different acid concentration. Activated kaolin sample was then mixed with TiO 2 to produce TiO 2 /Kaolin composite. Activated kaolin and TiO 2 /Kaolin composite were characterized using X-ray diffraction (XRD) and Fourier transform infrared (FT-IR). Various operational variables that affect the adsorption process were taken into consideration, including the effect of initial pH, contact time, initial dye concentration, and temperature. The adsorption parameters of kinetics, isotherm, and thermodynamics were also studied according to the most common model established. The results showed that the procion red adsorption was pH-dependent and reached equilibrium at 90 min. The kinetics study was revealed that the adsorption process was better demonstrated by the pseudo-first-order rather than the pseudo-second-order model. The adsorption isotherm investigation showed that the adsorption process was followed both Langmuir and Freundlich model with q e reached 158 mg/g, and the adsorption process was predicted in favorable condition. The thermodynamic study revealed that the adsorption process is spontaneous with endothermic nature. According to the results, it can be considered that the TiO 2 /Kaolin composite adsorbent has better adsorption capability to the procion red. KEY WORDS : Activated kaolin, TiO 2 , Composite, Adsorption, Procion red Bull. Chem. Soc. Ethiop. 2019 , 33(3), 437-450. DOI: https://dx.doi.org/10.4314/bcse.v33i3.5