Characteristics and Applications of Sewage Sludge Biochar Modified by Ferrous Sulfate for Remediating Cr(VI)‐Contaminated Soils

Abstract

Background. Soil contamination by hexavalent chromium is becoming a main environmental concern in China. This study developed a sewage sludge biochar modified by FeSO4 (CHBC) as a new reductant for Cr(VI)-contaminated soil. The effectiveness of CHBC-stabilized Cr(VI)-contaminated soil was investigated. Methods. Typical industrial Cr(VI)-contaminated soil in China was chosen as the medium. The total and Cr(VI) contents of the contaminated soil were 1014.6 and 973.5 mg/kg, respectively. The effectiveness of the Cr(VI)-contaminated soil stabilized by CHBC was investigated by the leaching test (US EPA method 1312), the simplified bioaccessibility extraction test (US EPA 2007 protocol and British Geological Survey), alkaline digestion (US EPA method 3060A), sequential extraction (BCR sequential extraction procedure), X-ray diffraction, and the risk assessment code test. Results. Results show that CHBC substantially reduced the leachability and Cr(VI) content of the contaminated soil. The leachability and content of Cr(VI) were lower than the thresholds of the Environmental Quality Standards of Soil in China for civil reuse and the China Environmental Quality Standards of surface water for civil use when the soil was stabilized with 10% dosage of CHBC. Conclusion. CHBC is highly efficient in stabilizing Cr(VI) and can effectively reduce the leachability and bioavailability of Cr in contaminated soil and thus feasible for stabilizing Cr(VI)-contaminated soil and shows potential for application in the field.

Pros and Cons of Biochar to Soil Potentially Toxic Element Mobilization and Phytoavailability: Environmental Implications

“…Sulfurization of a 700 °C-Eichhornia crassipes BC using sulfide Fe 3 O 4 coating triggered As(III) redox conversion through the generation of dissolved O 2 and Fe 2+ ions (Wang et al 2022). On the other hand, utilization of sewage sludge BC supported the action of ferrous sulfate as a green reductant for a Cr(VI)-contaminated soil, where passivation was considered from a mechanistic point of view (Li et al 2020). Alterations in leachability/bioaccessibility of Cr(VI) in the soil matrix could be mainly attributed to its reduction into less soluble and toxic Cr(III) with the help of active functional groups of BC (OH, C=O, C-H and C-O), as well as the concurrent oxidation of grafted Fe 2+ ions to their trivalent species.…”

Investigation of Cr (VI) adsorption from aqueous media by using synthetic chitosan-allophane nanocomposite adsorbent: characteristics, kinetic and isotherm

“…2,3 . The conventional methods such as chemical precipitation 4 , membrane ltration 5 , biological methods 6 , electrochemical methods and ion exchange 7 have been widely employed for chromium removal. Despite the progress made in Cr (VI) removal methods, these methods often have limitations such as including cost-effectiveness, scalability, and environmental impact.…”

Removal of Hexavalent Chromium from Aqueous Solutions Using Natural Zeolite Coated with Magnetic Nanoparticles: Optimization, Kinetics, and Equilibrium Studies

“…Different treatment techniques such as chemical precipitation, electrodialysis, solvent extraction, reduction, coagulation-flocculation, ion exchange, adsorption, oxidation, membrane filtration, constructed wetland, biological treatment, electrochemical deposition, and chemical immobilization have been used to remove heavy metals from industrial effluents [16, 17]. However, most of these techniques have been found to be inefficient and not cost-effective, energy intensive, generate highly toxic sludge, and require expensive equipment [4, 9].…”