LAUSR

Abstract Sludge and leaf are two kinds of typical solid wastes with huge production. How to effectively treat sludge/leaf thus becomes a hot issue and needs to be solved at present. This study aims to develop the resource recycling technology in converting waste sludge/leaf to biochar material for diclofenac (DFC) removal. Through the orthogonal test design, the effects of pyrolysis temperature, sludge/leaf ratio, and pyrolysis time were systematically investigated. Under the conditions of pyrolysis temperature 200 °C, sludge/leaf ratio 1:3, and pyrolysis time 1 h, the optimized biochar was simply produced where the key indicators iodine value and biochar yield reached 287.81 mg/g and 85.15%, respectively. Adsorption results revealed that DFC was rapidly and efficiently adsorbed by the recycled sludge/leaf biochar at the conditions of 25 °C, initial DFC concentration of 10 mg/L, solution volume of 8 mL, and biochar dosage of 0.005 g. With the maximum adsorption capacity of 877 mg/g, the DFC adsorption process was described well by pseudo-second order kinetics and Temkin isotherm model. Furthermore, after activation by 9% HCl solution, the specific surface area of the biochar increased from 3.30 to 4.17 m2/g, indicating that activated biochar had more sites for DFC adsorption. That was also confirmed by SEM images which showed more porous and rough characteristics on the surface structure of biochar. The data displayed a green environmental technique in converting waste sludge/leaf to useful biochar adsorbent for rapid and efficient DFC removal.