Use of oak acorns adsorbent and response surface methodology for removal of crystal violet from aqueous solution

Abstract

This study investigates the potential use of oak acorn pericarp powder as an effective adsorbent for removing crystal violet from aqueous solutions under citric acid activation. Various analytical techniques, including FTIR, EDS, and SEM, were used to examine the characteristics of the adsorbent obtained. Throughout the experiments, parameters such as adsorbent quantity, solution pH, and initial dye concentration were meticulously taken into account. To optimise this removal process, a customised experimental approach based on response surface methodology (RSM) was adopted, involving the performance of 20 series of experiments to assess the influence of key variables, including adsorbent dose (A), pH (B), and initial dye concentration (C), as well as their interactions. Statistical analysis reveals the high significance of the elimination model, supported by an extremely low probability value (p < 0.0001). Notably, increasing adsorbent mass and solution pH leads to higher rates of crystal violet removal. Conversely, as the initial dye concentration increases, the removal rate decreases. Furthermore, the interaction between these variables does not appear to have a significant influence. Under optimal conditions, a remarkable elimination rate of 99.96% was achieved. This involved a solution with an initial pH of 10.82, an adsorbent dose of 28.5 mg, and an initial dye concentration of 17.8 mg/L. The kinetics of crystal violet adsorption onto the adsorbent were effectively described by a pseudo-second-order equation. Additionally, the optimal multilayer uptake capacity of OA@CA for CV dye was determined to be 135.9 mg.g−1, and the Freundlich model demonstrated a significantly better fit to the experimental results when compared to the Langmuir model.