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.
Highlights
Chromium (Cr) is a common soil contaminant, and nearly 1.1% of China’s land is contaminated by Cr according to Chinese officials [1,2,3]
Is study developed a sewage sludge biochar modified by FeSO4 (CHBC) as a new reductant for Cr(VI)-contaminated soil. e effectiveness of the CHBC-stabilized Cr(VI)-contaminated soil was investigated by the leaching test (SPLP), the simplified bioaccessibility extraction test (SBET), alkaline digestion, sequential extraction, X-ray diffraction (XRD), and the risk assessment code (RAC). is study can provide a new reductant for stabilized Cr(VI)-contaminated soil and is relatively valuable for sewage sludge resource reuse
Zhang et al studied the Cr(VI) content of a contaminated soil stabilized by FeSO4 and CaS5. e Cr(VI) content of the stabilized soil decreased from 168 to 94 mg/kg to 21 and 4.2 mg/kg when the reductant dosage increased from 1% to 5%, respectively [31]. ese results indicate that CHBC is more advantageous than FeSO4 and CaS5 in stabilized Cr(VI) soil
Summary
Chromium (Cr) is a common soil contaminant, and nearly 1.1% of China’s land is contaminated by Cr according to Chinese officials [1,2,3]. Ferric salts and sulfides have adverse effects due to the acidity or high-sulfur content they impart to the soil [6, 7]. Zhou et al [12] used biochar and acidified manure treated with Cr(VI)-contaminated soil and Advances in Civil Engineering observed their high capacity to adsorb Cr(VI) (34.1 mg/g). Li et al [14] compared the biochars from maize stalk and peanut shell for reduced Cr(VI) in soils. Is study developed a sewage sludge biochar modified by FeSO4 (CHBC) as a new reductant for Cr(VI)-contaminated soil. E effectiveness of CHBC-stabilized Cr(VI)-contaminated soil was investigated. Results show that CHBC substantially reduced the leachability and Cr(VI) content of the contaminated soil. CHBC is highly efficient in stabilizing Cr(VI) and can effectively reduce the leachability and bioavailability of Cr in contaminated soil and feasible for stabilizing Cr(VI)-contaminated soil and shows potential for application in the field
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