Construction of flexible porous 3D biochar based on electrospun rice straw-derived cellulose acetate with excellent adsorption properties toward organic pollutants

Cellulose was extracted from rice straw waste by the intergrated technique of C₂H₅OH/H₂O, dilute alkali treatment and H₂O₂ bleaching process, and rice straw-derived cellulose acetate was obtained by the acetylation reaction of cellulose. Flexible porous 3D biochars were constructed by the electrospinning, NaBH₄ foaming and calcination process. Effects of calcination temperature, adsorption time, pH, pollutant concentration, interfering anions, and cycle times on the adsorption performance of 3D biochar were systematically investigated. 900 °C was the best calcination temperature for preparing 3D biochar, which possessed the largest specific surface area (524m²g⁻¹) and maximum adsorption capacity (149.266 mg/g) toward 10-60 mg/L MB. Its adsorption capacity in neutral (142.870 mg/g) and alkaline (131.075 mg/g) environments was bigger than that in acidic environments (69.867 mg/g). 3D-C900 biochar also has different adsorption capacity toward other dyes and antibiotics (MB 142.870, TC 107.200, RhB 70.110, MO 55.640 mg/g). The interfering anions had limited effect on its adsorption capacity and the removal efficiency of 3D-C900 biochar remained above 86.48 % after 5 cycles. The proposed 3D biochar realizes the high-value utilization of agriculture waste rice straw resources in the direction of water purification, which had potential applications in the fields of wastewater treatment, heavy metal ion adsorption and energy storage.