Abstract

Cr(VI) has become an urgent environmental concern due to its high toxicity. Adsorption is regarded as an effective technique for Cr(VI) removal, and high-performance adsorbents remain in great demand. In this study, waste-derived magnetic biochar (Fe0-Fe3O4 MB) was synthesized via synchronous pyrolysis combined with liquid-phase reduction, using Chinese medicinal residue as biomass feedstock and iron-based sludge as the sole iron source instead of traditional chemical agents. Mössbauer spectroscopy (MS) results confirmed the feasibility and high efficiency of synthesizing Fe0 using iron sludge as the iron source; meanwhile, in situ generated Fe3O4 and biochar effectively restrained particle aggregation and the surface passivation of Fe0. Cr(VI) adsorption fitted well with pseudo-second-order kinetics and Langmuir isotherm models, which suggests a predominant monolayer chemisorption process. The Fe0-Fe3O4 MB possessed excellent superparamagnetism, with a saturation magnetization of 66.74 emu/g. Rapid Cr(VI) adsorption was achieved within 30 min at pH 2 and 35 °C, with a maximum adsorption capacity of 128.36 mg/g. The main adsorption mechanisms may involve multiple pathways, including physical adsorption, electrostatic attraction, chemical reduction, and surface complexation. This study provides a feasible strategy for solid waste resource utilization and the fabrication of stabilized functional zero-valent iron materials, realizing the efficient adsorption treatment of Cr(VI)-containing wastewater.

IPC Classification

Keywords