Influence of Different Metals on Production of Sewage Sludge–Based Biochar and Its Application for Ammonium and Phosphate Adsorption Removal from Wastewater

Abstract

As the main solid waste of wastewater treatment plants (WWTPs), sewage sludge has the characteristics of large output and high contents of organic matter and inorganic metals. In this study, sewage sludge was used as raw material to prepare a unique sludge-based biochar. In order to obtain the best modification method for ammonium and phosphorus adsorption removal in wastewater, the sludge-based biochar was modified by loading four kinds of metal, respectively, including Mg, Al, Fe, and Mn, to improve the adsorption capacity of the biochar. A large number of adsorption experiments showed that Mg-modified sludge–based biochar (BC-Mg) had the best adsorption effect. At 25°C, the maximum adsorption capacity of NH4+ and PO43− reached 30.58 and 400.00 mg·g−1, respectively. In the double-solute coadsorption experiment, Mg-BC also had the best adsorption effect. In addition, kinetics, isotherms, and various characterization analyses [Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), Brunauer, Emmett and Teller (BET), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and zeta potential, among others] were used to study the physicochemical properties of the modified sludge–based biochar and the adsorption mechanism of NH4+ and PO43−. It mainly includes ligand exchange, ionic bond, deposition reaction, and electrostatic attraction to pollutants. This study not only provides a feasible strategy for efficient utilization of sewage sludge resources, but also provides a practical method for ammonium and phosphorus removal in water.