Phosphorus recovery from aqueous solutions by a Mg/Al-modified biochar from date palm wastes in column mode: adsorption characteristics and scale-up design parameters assessment

Abstract

In the current work, a Mg/Al-modified biochar from date palm wastes (Mg/Al-DPF-B) was synthesized, characterized, and applied for phosphorus (P) recovery from aqueous solutions in column mode. The P recovery was assessed for various P initial concentrations (25–100 mg L−1), feeding flow rates (9–27 mL min−1), and biochar masses (3–8 g). Biochar characterization shows that the structural, textural, and surface chemistry properties of the biochar were significantly enhanced due to the high-deposition loads of magnesium oxides (MgO), magnesium hydroxides (Mg(OH)2), and aluminum oxides (Al2O3) nanoparticles on its surface. The column experiment results indicate that the P breakthrough curve shape (BTCs) and performance are highly influenced by the biochar mass and the highest adsorbed amount (7.0 mg g−1) corresponds to a mass of 8 g. Moreover, the experimental BTCs align well with predictions by Thomas and Yoon-Nielson models. The P recovery process involves a combination of surface complexation and precipitation as magnesium and/or aluminum phosphates. The scale-up design considerations indicate that a large-scale column having a diameter and a height of 211 and 50 cm, respectively, can effectively treat 116 m3 of real wastewater achieving a P recovery rate of more than 0.5 kg P day−1.