Preparation of low-cost sludge-based highly porous biochar for efficient removal of refractory pollutants from agrochemical and pharmaceutical wastewater.

ABSTRACT

Producing a high-performance sludge biochar through a feasible method is a great challenge and is crucial for practicability. Herein, we reported a highly porous sludge biochar synthesized from agrochemical-pharmaceutical and municipal sludge blends through a novel pyrolysis-acid treatment-post pyrolysis method. The optimized biochar named ASMS91 obtained interconnected pores with a total pore volume of 0.894 cm3/g and a surface area of 691.4 m2/g through extended acid wash and subsequent post-pyrolysis, which is superior to non-activated sludge biochar. ASMS91 removed 45.3 % of wastewater COD (156 mg/L) in 24 h, which was rapid and higher performance than commercial activated carbon (1000 iodine number). This outstanding performance is due to its high adsorption ability of long-chain aliphatic compounds (e.g., 2,4-Di-tert-butylphenol, neophytadiene and eicosane) into mesopores, which accounts for 71.8 % of pore filling. ASMS91 was highly recyclable, and adsorption was reduced by only 5.3 % after the 4th cycle. It also outperformed other sludge biochar in literature in removing perfluorooctanoic acid (PFOA), 62 fluorotelomer sulfonate (62 FTS), sulfamethoxazole, methylene blue, and methylene orange. Finally, the feasibility of our proposed method was validated by a brief techno-economic analysis. This feasible approach may support future research regarding sludge valorization and low-cost chemical wastewater treatment.