Application of microbial immobilization technology for remediation of Cr(VI) contamination: A review

Killing Two Birds with One Stone: Biomineralized Bacteria Tolerate Adverse Environments and Absorb Hexavalent Chromium

“…Chromium-containing chemicals are used in a wide range of industrial processes, such as leather tanning, mining operations, alloy, paint and pigments, glass industry, wood preservation, film, and photography. 1 − 3 Hexavalent chromium is an environmental pollutant and a recognized carcinogen. 1 , 4 Cr (VI) exhibits high toxicity and causes diarrhea, ulcers, eye and skin irritation, and, in severe cases, even renal insufficiency and lung cancer.…”

“… 2 , 14 − 16 However, the poor resistance of bacteria to contaminants is a bottleneck for biotechnology application. 3 , 13 Hexavalent chromium has good cell membrane permeability and readily enters bacteria, where it subsequently undergoes reduction reactions and generates free radicals (e.g., reactive oxygen species), leading to bacterial death. 2 , 4 Bacteria with resistance to hexavalent chromium are usually isolated from contaminated soil and water for further use in the biosorption.…”

“…Chromium-containing chemicals are used in a wide range of industrial processes, such as leather tanning, mining operations, alloy, paint and pigments, glass industry, wood preservation, film, and photography. − Hexavalent chromium is an environmental pollutant and a recognized carcinogen. , Cr (VI) exhibits high toxicity and causes diarrhea, ulcers, eye and skin irritation, and, in severe cases, even renal insufficiency and lung cancer. , Chromium-contaminated wastewater puts pressure on the environment, so various techniques have been employed to treat Cr­(VI)-contaminated water, such as physical adsorption, electrochemical precipitation, ion exchange, ultrafiltration, and reverse osmosis. However, there are many major drawbacks involved in the pre- and post-treatment of wastewater, including high cost, complex process, low removal efficiency, and even secondary contamination. − …”

“…Biosorption is a promising technology for the removal of hexavalent chromium from wastewater, which is economical, efficient, and environmentally friendly. ,− Organisms including bacteria, fungi, yeast, algae, and plants have shown the ability to remediate. ,− However, the poor resistance of bacteria to contaminants is a bottleneck for biotechnology application. , Hexavalent chromium has good cell membrane permeability and readily enters bacteria, where it subsequently undergoes reduction reactions and generates free radicals (e.g., reactive oxygen species), leading to bacterial death. , Bacteria with resistance to hexavalent chromium are usually isolated from contaminated soil and water for further use in the biosorption. , The isolation and culture of specific bacteria is complex and difficult. , Therefore, we hope that, by improving the tolerance of common bacteria to extreme environments, common bacteria can also be applied to biosorption. In recent years, researchers found that bacteria could be modified by inorganic nanoparticles, polymers, and metal–organic frameworks (MOFs) to enhance their resistance to harsh environments. − MOFs are synthesized by cross-linking metal ions/clusters with organic linkers.…”

Factors Affecting the Detection of Hexavalent Chromium in Cr-Contaminated Soil

“…At present, chemical reduction has become the most widely used remediation method for Cr(VI)-contaminated soil due to its high efficiency, strong adaptability and low cost [ 5 ]. Remedial agents include ferrous sulfate, calcium polysulfide, sodium metabisulfite and so on [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. However, in some remedial engineering projects, it is found that a relatively high concentration of Cr(VI) was detected in the soil treated with excessive reductants after being stored in the field for a period of time and the color of the treated soil turned yellow again, causing serious secondary pollution [ 14 ].…”