Process optimization, isotherm, kinetics, and thermodynamic studies for removal of remazol brilliant blue-r dye from contaminated water using adsorption on guava leaf powder

The current batch system addresses the use of guava leaf powder as an economical adsorbent for adsorption of aromatic dye, Remazol brilliant blue-R (RBBR) from wastewater. The consequences of various experimental variables were optimized with response surface methodology (RSM) to achieve the utmost decolorization efficiency. The adsorbent was characterized by proper instrumental evalua-tion. Adsorption isotherms for the decolorization of RBBR were assessed by several adsorption mod-els. The experimental equilibrium data suited the Langmuir isotherm model, and also the maximum monolayer adsorption capability (q_max ) was 93.12 mg g^–1 . Thermodynamic studies were performed to evaluate change in Gibbs free energy (ΔG), change in enthalpy (ΔH), and change in entropy (ΔS) of the adsorption process. From the results, the adsorption was found to be endothermic in nature, and the process was chemisorption, spontaneous and favorable at higher temperature. Kinetic rate constants were calculated using distinct kinetic models. The dye adsorption rate followed pseudo-secondorder kinetic model. The adsorption mechanisms were clarified by pore diffusion, Bangham and Boyd plots. The general rate of adsorption is controlled by both film and pore diffusion of dye compounds. Desorption studies were conducted with various desorbing reagents. Most desorption efficiency was acquired by the solvent methanol.