Recent bioreduction of hexavalent chromium in wastewater treatment: A review

Abstract

Hexavalent chromium (Cr(VI)) in water is a proven carcinogen to different internal and external organs of the living organisms. There are different human activities incorporated to the anthropogenic sources in the environment enriching Cr(VI) of high concentration in the water system above the regulatory level. The physical, chemical and biological properties of chromium favour the dissolution in the water environment. This concerns the environmental researcher to tackle and mitigate. Chemical or biological techniques or a combination of the two have been used to remove Cr(VI) from polluted waters. Biological techniques include integrated bioremediation, such as the primary processes of direct bioreduction and biosorption, and secondary processes of microbial fuel cell, biostimulation, surface modified dry biomass and biochar adsorption, and engineered biofilm and cell free reductase. These techniques are used by a wide range of living organisms including bacteria, fungi, plants, plant leaves, plant nuts and algae. This group of living organisms transform and remove Cr(VI) from water during the cellular metabolisms, extracellular activities, physical and chemical adsorptions on the cell surface, and photosynthesis. Variation of different physical, chemical and environmental parameters affecting the efficiency of the bioremediation process have impacted on the design of bioreactors. There has been a recent development of a microbial fuel cell which use the proximity of Cr(VI) reduction as a cathode half cell for the generation of renewable energy and simulation of its' removal from water.

Adsorption of Hexavalent Chromium Using Banana Pseudostem Biochar and Its Mechanism

“…Chromium, a toxic heavy metal, is widely discharged into the aquatic environment from various industries [1,2], causing serious harm to human health directly or indirectly [3][4][5]. Usually, chromium exists in hexavalent and trivalent forms in polluted water.…”

“…Usually, chromium exists in hexavalent and trivalent forms in polluted water. Hexavalent Cr is highly toxic, carcinogenic and allergenic, while trivalent Cr is an essential trace element for mammals and less toxic [2,[6][7][8]. Many treatment methods have been developed for removal of hexavalent chromium from water in the past decades, such as chemical precipitation [9], sedimentation [10], flocculation [11], adsorption [12], ultrafiltration [13], ion exchange [14], chemical coagulation [15], and so on.…”

Critical review on microbial fuel cells for concomitant reduction of hexavalent chromium and bioelectricity generation

“…Biocathode MFCs are a budding technology in the field of Cr(VI) bioremediation, which use electrochemically active microorganisms as catalytic centers at both the anode and cathode . Cr(VI) reduction could be enhanced by using metal‐reducing bacteria, which shunt electrons from the cathode to the electron acceptor . Inexpensive mode of operation, self‐regeneration of catalysts and sustainable power supply are the advantages of this design over abiotic cathodes .…”

“…20 Cr(VI) reduction could be enhanced by using metal-reducing bacteria, wileyonlinelibrary.com/jctb which shunt electrons from the cathode to the electron acceptor. 49 Inexpensive mode of operation, self-regeneration of catalysts and sustainable power supply are the advantages of this design over abiotic cathodes. 50 The first attempt to biologically reduce Cr(VI) by means of a biocathode MFC was reported by Tandukar et al 12 This study used a conventional H-type MFC with its cathode chamber inoculated with a mixture of denitrifying and anaerobic cultures enriched in the presence of Cr(VI).…”

Simultaneous Treatment of Agro-Industrial and Industrial Wastewaters: Case Studies of Cr(VI)/Second Cheese Whey and Cr(VI)/Winery Effluents

“…Nowadays, the removal of inorganic (heavy metals, such as Cr, Pb, and Cd) and organic pollutants (proteins, carbohydrates, fats, and nucleic acids) from industrial/agro-industrial wastewaters remains a huge challenge, leading to an important problem in the field of wastewater purification [1].…”