Adsorption Characteristics of Heavy Metals Pb2+ and Zn2+ by Magnetic Biochar Obtained from Modified AMD Sludge

Abstract

Acid mine drainage (AMD) sludge can be used to prepare adsorbent materials for the removal of heavy metals in water, which is an effective means for its resource utilization. Magnetic modified biochar (MMB), which can be recovered by magnetic separation, was prepared from sludge generated from the carbonate rock neutralization treatment of AMD and rice straw agricultural waste. Unmodified biochar (UMB) was obtained from rice straw and chemically modified and treated by ultraviolet radiation to produce MMB. The Pb2+ and Zn2+ adsorption capacities of UMB and MMB were investigated. Simultaneously, the materials were characterized by SEM, FTIR, BET, and ZETA. The results showed that the specific surface area (130.89 m2·g−1) and pore volume (0.22 m2·g−1) of MMB were significantly increased compared to those of UMB (9.10 m2·g−1 and 0.05 m2·g−1, respectively). FTIR images showed that MMB was successfully loaded with Fe3O4. The adsorption process of Pb2+ and Zn2+ onto MMB was consistent with the Langmuir adsorption isotherm and second-order kinetic models, with maximum adsorption capacities of 329.65 mg·g−1 and 103.67 mg·g−1, respectively. In a binary system of Pb2+ and Zn2+, MMB preferentially binds Pb2+. The adsorption efficiencies of MMB reached >80% for Pb2+ and Zn2+.

Modulatory Role of Biochar Properties and Environmental Risk of Heavy Metals by Co-Pyrolysis of Fenton Sludge and Biochemical Sludge

“…Studies have demonstrated the effectiveness of sludge pyrolysis in reducing sludge volume and using organic matter to produce sludge biochar at minimal cost [ 14 ]. Concurrently, pyrolysis of sludge has been shown to efficiently immobilize HMs [ 15 ], thereby lowering their bioavailability in sludge [ 16 ] and facilitating the reuse of sludge products [ 17 ]. Since the co-pyrolysis process of sludge produces catalytic and synergistic effects, the resulting co-pyrolysis biochar has found diverse applications in environmental treatments, including soil improvement [ 18 , 19 ], pollutant adsorption [ 20 ], and catalytic reactions [ 21 ].…”