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Nutmeg seed shell biochar as an effective adsorbent for removal of remazol brilliant blue reactive dye: kinetic, isotherm, and thermodynamic study

ABSTRACT Biochar derived from agricultural wastes has emerged as an effective adsorbent for wastewater treatment. However, studies on nutmeg seed shell (NSS) utilization in textile wastewater treatment is limited. This study explores the possibility and efficacy of using a modified nutmeg seed shell as an adsorbent to remove remazol brilliant blue reactive dye (RBBR) from the aqueous wastewater. The adsorbent was characterized before and after adsorption using FTIR, FE-SEM, TGA, and XRD, respectively. Response surface methodology (RSM), based on Box–Behnken design (BBD), was utilized to optimize the effects of initial concentration (5–100 mg/L), pH (2–12), contact time (10–120 min), and adsorbent dosage (0.5–3 g/L) on the RBBR removal. The quadratic model generated by RSM describes the best relationship between the independent parameters and the dye removal efficiency. The optimum conditions for the RBBR dye removal were observed at an initial concentration of 100 mg/L, adsorbent dose of 2.85 g, pH of 10, and contact time of 110 min, which resulted in 93.41% removal efficiency. The adsorption model fits the pseudo-second-order and Langmuir isotherm models with correlation factors (R2 ) > 0.99. Langmuir adsorption isotherm gives an optimum adsorption capacity of 173.31 mg/g. The adsorption isotherm and kinetics study shows that the adsorption process is based on monolayer chemisorption. The thermodynamic studies suggest that adsorption is a spontaneous and endothermic process. The result indicates that modified NSS is an efficient adsorbent for removing reactive dye RBBR. Graphical abstract