A Box-Behnken design-based chemometric approach to optimize the removal of phosphate ions from water using Punica granatum shells

The present study was aimed at evaluating the adsorption of phosphate ions using Punica granatum shells (PGS) as an environmentally friendly and economical sorbent material. The PGS powder was characterized by several techniques including BET, ${pH}_{\mathrm{pzc}},$ SEM, and FTIR, as well as its adsorption capacity evaluated with the sorption of ${PO}_4^{3-}$ from water. To achieve adequate removal of ${PO}_4^{3-}$ from water, a chemometric method based on the Box–Behnken design was applied to optimize the influence of the main operating factors such as the PGS amount (0.10–1 g L⁻¹), medium pH (3–9), and ${PO}_4^{3-}$ initial concentration (10–100 mg L⁻¹) on the adsorption processes. Noteworthy, the best adsorption amount (29.31 mg g⁻¹) was obtained at a pollutant dose of 72.72 mg L⁻¹, an adsorbent quantity of 1 g L⁻¹ in medium acid pH 3 at 25 °C. The modeling study suggests that the process of ${PO}_4^{3-}$ uptake follows the pseudo-second-order model with a maximum adsorbent quantity of 32.25 mg g⁻¹.