Adsorptive removal of phosphate from water using corn straw derived biochar

Abstract Phosphorus in the water environment comes from some untreated industrial, agricultural, and domestic wastewater, posing a significant threat to human health and other biota due to its toxicity. Herein, modified corn straw biochar (LBC)/sodium alginate (SA) composite (LBS) adsorbents were prepared to eradicate phosphate from water (belonging to batch adsorption). The results showed that the best pyrolysis temperature for preparing LBS was 550°C, and the specific surface area and average pore diameter of the 550LBS (LBS at 550°C) 80.96 m 2 /g and 3.82 nm, respectively, indicating more adsorbability. The maximum adsorption amount was 61.4 mg/g (exceeding 36.44 mg/g) when pH was 2 and the mass ratio of 550LBC/SA was 0.3 g/0.3 g. The adsorption of phosphate by 550LBS was consistent with the Langmuir model and the pseudo‐first‐order model (R 2 > 0.95) and reached adsorption equilibrium at 20 min. The adsorption of 550LBS was due to the protonation between the surface hydroxyl group and H + , and the phosphate adsorption of 550LBS was dominated by ligand exchange and electrostatic attraction. Compared with the maximum adsorption capacity of 550LBS, the used 550LBS could be reused; the adsorption efficiency of adsorbents after three tests was still above 41% using deionized water as the desorption agent, showing good reusability and renewability of 550LBS and low‐cost adsorbents. It possessed suitable scientific results for researchers in the field of environmental sciences. The study presented a low‐cost, sustainable adsorbent for phosphate removal, addressing eutrophication and water pollution concerns. The use of LBC with SA is innovative, combining agricultural waste valorization with efficient adsorption.