Optimized Ca-Al-La modified biochar with rapid and efficient phosphate removal performance and excellent pH stability

Abstract

Biochar-based adsorbents for phosphate removal from wastewater has gained increasing attention and achieved significant progress. However, there is still much room for the enhancement on adsorption performance in terms of removal rate, adsorption capacity and pH application range. Herein, novel Ca-Al-La modified biochar adsorbents in this study were synthesized for enhancing phosphate adsorption in wastewater. The synthesis parameters of adsorbents were optimized by using the response surface methodology (RSM). The Ca-Al-La modified biochar adsorbent synthesized under the optimal conditions (CAL-MBC) exhibited superior adsorption capability towards phosphate. Specifically, CAL-MBC achieved a rapid removal rate to reach the adsorption equilibrium within 1 h, a maximum phosphate adsorption capacity of 152.9 mg/g, and excellent pH stability within a broad pH range of 3.0–11.0. The adsorption mechanisms involving electrostatic interaction, precipitation and inner-sphere complexation via ligand exchange were responsible for the excellent adsorption performance of phosphate on CAL-MBC. This study verifies CAL-MBC as a promising metal modified biochar adsorbent to enhance phosphate removal from wastewater.