Preparation of porous biochar based on pharmaceutical sludge activated by NaOH and its application in the adsorption of tetracycline

Abstract In this study, two different kinds of pharmaceutical sludge activated by NaOH were used to prepare biochar. The characteristics of biochar prepared by impregnation method and dry mixing method were analyzed, including N2 adsorption–desorption isotherms, surface functional group analysis and micromorphological observation. The results showed that the biochar prepared by impregnation method had more micropores, while that prepared by dry mixing activation method had more mesopores. The adsorption reaction of tetracycline on the two different kind of biochar was investigated. Several important factors such as solution initial pH, tetracycline concentration and reaction time on adsorption reaction were investigated. The results show that both kinds of biochar have high tetracycline adsorption efficiency and excellent pH adaptability. The biochar manufactured by dry mixing activation method had better adsorption performance (379.78 mg/g, 25 °C). Regeneration experiments showed that the adsorbent had stable performance in absorbing tetracycline. Direct dry mixing activation method is a simple and effective method used to prepare porous biochar, which can be used for the resourceful utilization of pharmaceutical sludge. This work provides extensive information on the use of biochar derived from pharmaceutical sludge for the removal of TC from hospital and pharmaceutical production wastewater.