Novel magnetic N-doped biochar derived from sugarcane bagasse and red mud for effective adsorption of tetracycline hydrochloride

In this work, with sugarcane bagasse (SB) and red mud (RM) as raw materials, magnetic nitrogen (N)-doped biochar (MNSB) was synthesized by a facile one-pot pyrolysis method and then applied as an efficient adsorbent to remove tetracycline hydrochloride (TC-HCl) from wastewater. The results of SEM, EDS, VSM, BET, FT-IR, and XPS demonstrated that the synthesized MNSB adsorbent had a large specific surface area, excellent superparamagnetic properties, and rich mesopore pore structures. The batch adsorption experiments revealed that the TC-HCl could be removed 96.3% with the optimal adsorption conditions: MNSB dosage of 0.25 g/L, initial pH of 6.58, TC-HCl initial concentration of 20 mg/L, and adsorption temperature of 30 oC. The analysis of adsorption kinetics and isotherms showed that the adsorption process was mainly controlled by chemisorption, and the theoretical maximum adsorption capacity of TC-HCl on MNSB was 143.9 mg/g. Mechanistic analysis revealed that the excellent adsorption process of MNSB for TC-HCl was mainly contributed by pore filling, π–π interaction, hydrogen bonding, and electrostatic attraction. The recycling and settlement experiments demonstrated that MNSB had good stability and settleability. This study successfully opened new prospects that utilizing RM and SB to prepare a low-cost adsorbent to remove TC-HCl from water.