Characteristics and Mechanisms of Phosphorous Adsorption by Peanut Shell-Derived Biochar Modified with Magnesium Chloride by Ultrasonic-Assisted Impregnation

[Image: see text] Recovery of phosphate (P) from sludge, domestic wastewater, and industrial wastewater is beneficial for overcoming the problem of shortage of P rock resources. In this study, Mg-functionalized peanut shell-derived biochar was prepared by ultrasound-assisted impregnation. The obtained Mg-laden biochar had a higher content of Mg, a larger specific surface area, and more porosity. The prepared Mg-modified biochar exhibited excellent adsorption properties of phosphorus. Modified biochar has a higher amount of adsorbed P than raw biochar. The capacity of P adsorption by modified biochar was 30.48–114.24% higher than that by raw biochar. Moreover, the Mg-laden biochar can be applied in a wide working environment (pH: 2–10; temperature range: 15–40 °C). This study not only develops a new strategy for the preparation of high-capacity P adsorbents but also provides a new green use for agricultural peanut shells.