Effect of carbonaceous materials on phosphorus removal in flow-through packed column systems

Phosphorus (P) overloading in aquatic environments has long-been recognized as the leading cause of water quality deterioration, harmful algal bloom, and eutrophication. This study investigated P removal performance by five cost-effective carbonaceous materials (CMs) in flow-through packed column systems. These CMs include biochars pyrolyzed from feedstocks of Eucalyptus (E-biochar) and Douglas fir (D-biochar), commercial biochar (C-biochar), iron oxide-coated biochar (Fe-biochar), and commercial activated carbon (AC). The physicochemical properties of CMs, such as specific surface area (SSA), pore volume, pore diameter, elemental composition, and surface charge, were characterized. The packed column experimental results showed that P removal performance followed the order: E-biochar < D-biochar < C-biochar < Fe-biochar < AC. Specifically, the sorption capacity of 1 mg/L of P in packed columns was 0.0036 mg P/g E-biochar, 0.0111 mg P/g D-biochar, 0.0369 mg P/g D-biochar, 0.077 mg P/g Fe-biochar, and 0.088 mg P/g AC, respectively. The largest SSA (1012 m²/g) and pore volume (0.57 cm³/g) of AC accounted for the most outstanding P removal efficiency mainly by physical sorption, while electrostatic interaction explained the high P removal by Fe-biochar (SSA as low as 32.4 m²/g). Our findings provide direct practical implications for effectively removing P in water by cost-effective CMs.