Surfactant-promoted enhancement in bioremediation of hexavalent chromium to trivalent chromium by naturally occurring wall algae

• Published in: Research on chemical intermediates 2017-03, Vol.43 (3), p.1619-1634
• Main Authors: Nandi, Rumki, Laskar, Subrata, Saha, Bidyut
• Format: Article
• Language: English
• Subjects: Algae; Biological activity; Biological effects; Bioremediation; Catalysis; Chemical reactions; Chemistry; Chemistry and Materials Science; Cyanobacteria; Diphenylcarbazide; Efficiency; Fluorescence; Hexavalent chromium; Inorganic Chemistry; Oxidation; Physical Chemistry; Ponds; Seawater; Sodium dodecyl sulfate; Spectrophotometry; Surfactants; Tanning industry; Trivalent chromium
• ISSN: 0922-6168; 1568-5675
• DOI: 10.1007/s11164-016-2719-0

The discharge of hexavalent chromium [Cr(VI)] has resulted in significant pollution because of the presence of Cr(VI) oxyanions. They are highly water-soluble, cell-permeable and transportable in water sources. To eliminate the toxic effects, various chemical and biological methods have been developed. Bioremediation can be used as an effective tool over conventional chemical processes for the removal of toxic hexavalent chromium species. Blue-green algae-mediated bioremediation is gaining more interest due to its availability and efficiency. In this method, [Cr(VI)] is reduced to relatively less toxic [Cr(III)] as a consequence of oxidation of organic components present in the water extract of wall algae. The percent removal of Cr(VI) is increased by the addition of the anionic surfactant sodium dodecyl sulfate (SDS) and the neutral surfactant Triton-X-100 (TX-100). It was found that the percent removal efficiency of unanalyzed, TX-100 and SDS catalyzed (3 × 10 −2  M) systems are approximately 47, 54 and 80 %, respectively, in 8 days. The efficiency of these systems increases with the increase in the equivalent amount of added surfactant (3 × 10 −1  M). The reaction proceeds to almost completion (96 %) with the increase in the added surfactant (3 × 10 −1  M). The optimum pH of the reaction was found to be 2 and the temperature 40 °C. The amount of Cr(III) formed was measured by the fluorescence technique with a known dye selective to Cr(III), and the presence of soluble Cr(VI) in the mixture was estimated by a diphenylcarbazide kit. This method was further used to determine the removal efficiency of the SDS-catalyzed system in collected [Cr(VI)]-contaminated water sources, i.e. a pond beside the Sukinda valley in Cuttack, India, and pond water from the local area, sea water from Cuttack and Digha, W.B., India, as well as from the tanning industry. All the observations were recorded using UV–Vis, fluorescence and FTIR spectrophotometry.