Selective and efficient removal of phosphate from aqueous solution using activated carbon‐supported Mg–Fe layered double oxide nanocomposites

Abstract

In the face of the continuous development of novel adsorbents, developing robust adsorbents with high efficiency, strong phosphate selectivity, high regenerability, and cost effectiveness is a scientific challenge. In the present study, an activated carbon‐supported MgFe2O4‐layered double hydroxide (AC@ MgFe2O4‐LDH) derived Mg–Fe layered double oxide (AC@ MgFe2O4‐LDO) nanocomposite was synthesized at various temperatures and its potential application for phosphate adsorption was investigated. The nanocomposite exhibited a hierarchical mesoporous structure with a Brunauer–Emmett–Teller (BET) specific surface area of 193 m2/g and a narrow per‐size distribution of ~2 nm. AC@MgFe2O4‐LDO exhibited a high point of zero charge (pHpzc) value of 9.8 and robust phosphate adsorption potential over a wide pH range of 4–9 due to its high pH buffering capacity. The effects of adsorbent dose, layered double hydroxides (LDH) calcination temperature, initial phosphate concentration, contact time, and temperature on the phosphate adsorption capacity of the adsorbent were investigated. In the present study, up to 99.0% removal of phosphate was achieved at a 4 g/L adsorbent dosage in 4 h at pH 7 and 30°C. An adsorption kinetics study revealed that the adsorption of phosphate by AC@MgFe2O4‐LDO reached equilibrium within 240 min, with the kinetic experimental data fitting well with pseudo‐first‐order kinetics (r2 >0.99). The Langmuir adsorption isotherm model fit the experimental data well, with a maximum adsorption capacity of 25.81 mg/g. The adsorbent displayed strong phosphate selectivity in the presence of competing anions, and the study demonstrated that AC@MgFe2O4‐LDO has promising potential for efficient phosphate adsorption over a wide pH range.