Modeling and optimization of the adsorptive removal of crystal violet dye by durian (Durio zibethinus) seeds powder: insight into kinetic, isotherm, thermodynamic, and adsorption mechanism

In this study, a renewable and effective bio-adsorbent was derived from Malaysian durian seeds (DSs) to act as a promising biosorbent for phytoremediation application towards removal of a hazardous cationic dye (crystal violet, CV) from aqueous environments. The physiochemical characteristics of DS were investigated by several analytical methods such as FTIR, TGA-DTG, BET, pH pzc , and SEM-EDX. Subsequently, a statistical optimization for CV removal by DS was carried out via Box-Behnken design (BBD) and numerical desirability function. In this regard, four operational factors that affect CV adsorption, i.e., DS dosage (0.02–0.1 g), initial pH (4–10), temperature (25–50 °C), and adsorption time (5–25 min) were optimized by BBD and numerical desirability function. Hence, the highest CV removal (93.91%) was recorded under the optimal conditions found through desirability function as follows: DS dosage of 0.081 g, solution pH = 9.9, working temperature = 34.6 °C, and contact time = 24.9 min. Furthermore, ANOVA test indicated the significant parametric interactions towards CV removal (%) can be observed between AB (DS dose vs . initial pH), AD (DS dose vs . time), and BC (initial pH vs . temperature) interactions. The adsorption kinetic process was well described by a pseudo-second-order model. Subsequently, the adsorption equilibrium isotherm was well presented by Freundlich and Temkin isotherm models with maximum adsorption capacity of 158 mg/g. Thus, the thermodynamic functions revealed that the adsorption process was spontaneous and endothermic in nature. The adsorption mechanism of CV on the DS surface can be ascribed to the electrostatic forces, n -π stacking, and H-bonding interactions. Thus, the output of the research work indicates the potential applicability of DS as a renewable and effective biosorbent for the removal of CV from aqueous environments.