Efficient sono-sorption removal of malachite green by nano-TiO2/CuO: a multivariate study

Abstract

In this research study, TiO₂/CuO nanocomposite adsorbents were successfully synthesized by employing a bottom-up approach for efficient removal of Malachite Green (MG) dye in an ultrasonic-assisted adsorption process. Morphological, structural, and chemical studies were performed using SEM, EDX, and FTIR spectroscopy. Central composite design with five (05) factors was employed to design the adsorption experiment, while response surface methodology was used to evaluate the optimum operating parameters (OOPs). The OOPs for 99.4% removal of MG were observed as a pH of 6.9, an adsorbent usage of 23.0 mg and a time duration of 7.6 min, respectively. In the kinetics study, the model dye followed pseudo-second order kinetics and the Freundlich isotherm model was found to be the best fitted model. In addition, a desorption study was performed in different solvents to regenerate the spent adsorbent, which was successfully employed for six (06) cycles. Finally, thermodynamic studies were performed to assess the feasibility of the adsorption process, and the negative ΔG^o and positive ΔS^o values illustrate the spontaneous nature of the dye adsorption process.