Bimetallic oxide nanocomposite hydrochar for phosphate capture from aqueous environments
Kehinde Shola Obayomi, Alice Muhorakeye, Roy Bernstein, Amit Gross
Abstract
A recyclable activated sludge-derived hydrochar, carbonized at 210 or 240 °C, was synthesized via an in situ hydrothermal method and incorporated with Fe@Mg nanoparticles for phosphate removal from aqueous systems. Incorporation of the bimetallic oxide increased the surface potential of the activated hydrochar (AHC), offering more sites for phosphate adsorption, with BET surface areas of 72 and 62 m 2 /g and maximum phosphate adsorption capacities of 139.5 and 100.9 mg/g for AHC 210 and AHC 240 , respectively. Adsorption kinetics and isotherms revealed that the phosphate adsorption process was best described by the Elovich and Temkin models, indicating the predominance of chemisorption on heterogeneous surfaces. In the presence of competing ions and model organic matter, AHC retained a strong selectivity for phosphate, with over 78 % adsorption after four regeneration cycles. It also demonstrated excellent selectivity and high performance for phosphate removal from complex AnMBR wastewater, underscoring its potential for broad wastewater treatment applications. The binding of phosphate to AHC surfaces involved hydrogen bonding, electrostatic interactions, surface precipitation, and complexation reactions. Density functional theory calculations confirmed that oxygen-containing functional groups played a key role in phosphate adsorption via complexation. This study presents a new approach for the development of environmentally friendly, bimetallically modified hydrochar from sewage sludge, with effective adsorptive performance for purifying phosphate-laden wastewater.