Ecotoxicity study of reduced-Cr(III) generated by Cr(VI) biosorption

Area of Science:

• Environmental Science
• Environmental Chemistry
• Biotechnology

Background:

• Hexavalent chromium (Cr(VI)) is a known carcinogen.
• Biosorption is a key Cr(VI) removal method, often involving redox reactions.
• The properties and toxicity of reduced chromium (Cr(III)) post-biosorption are understudied.

Purpose of the Study:

• To assess the mobility and toxicity of Cr(III) generated during Cr(VI) biosorption.
• To evaluate pine bark as a low-cost biomass for Cr(VI) removal and detoxification.
• To characterize the reduced Cr(III) using advanced spectroscopic and environmental testing methods.

Main Methods:

• Utilized pine bark for Cr(VI) biosorption from aqueous solutions.
• Employed X-ray Absorption Near Edge Structure (XANES) spectroscopy for structural analysis of reduced Cr(III).
• Assessed Cr(III) mobility via precipitation, adsorption, and soil column tests, and toxicity using radish sprouts and water fleas.

Main Results:

• XANES analysis revealed an unsymmetrical structure for the reduced Cr(III).
• Reduced Cr(III) demonstrated low mobility in environmental simulations.
• The reduced Cr(III) was found to be virtually non-toxic and even beneficial for plant growth.

Conclusions:

• Cr(VI) biosorption using pine bark effectively detoxifies Cr(VI) by reducing it to a less harmful Cr(III) form.
• Pine bark is a viable, low-cost biosorbent for Cr(VI) removal.
• The study confirms the safety and potential benefits of Cr(III) generated through this biosorption process, offering a groundbreaking detoxification technology.