Efficient removal of sulfamethoxazole by biomass phosphorus-derived Cu3P/biochar catalyst combined with persulfate

Abstract

Sulfamethoxazole (SMX) is ubiquitous in environments with concentrations ranging from nano-gram per liter to milli-gram per liter in practice, especially in water matrices (surface water and wastewater), posing a grave threat to ecosystems for its antibacterial and persistent characteristics. Efficient SMX removal is critical for water purification. Herein, the nano and micron Cu3P particles are synthesized on biochar utilizing phytic acid (PA) doped rice brans. PA facilitates the transformation of Cu-containing precursors to Cu3P on biochar, promoting catalytic performance. Under the conditions of 0.15 g/L catalyst (6PA-Cu11), 3.0 mM persulfate (PS), and pH 7.00, sulfamethoxazole (SMX) at a concentration of 0.25, 0.50, 1.00, and 10.00 mg/L can be completely removed within 30, 60, and 180 min, respectively. Moreover, the combination of Cu3P/biochar and persulfate exhibits preferable catalytic performances for SMX removal in sodium humate solution and surface water matrices, demonstrating the broad applicability of such a catalytic system for water purification. Sulfate radical (SO4−•) and hydroxy radical (•OH) play vital roles in the oxidation of SMX, with 1O2 assisting in. Except for cuprous ion (≡Cu+), partially charged copper ions (≡Cuδ+) and phosphorus ions (≡Pγ−) in Cu3P, owning the electron-donating ability, are found to participate in the activation of PS or the reduction of high-valent copper ions depending on density functional theory (DFT) calculations. Biochar carrier enhances the catalytic role of copper ions in Cu3P and facilitates the recovery of active sites by improving the desorption of the activation product (SO42−) from the Cu3P surface. This research promotes the practicability of the Cu3P/biochar catalyst in the advanced oxidation process for refractory organic pollutant removal and deepens the perception of its catalytic mechanisms.