Chromium removal from aqueous solution by the ferrite process.

Area of Science:

• Environmental Chemistry
• Materials Science
• Chemical Engineering

Background:

• Hexavalent chromium (Cr(VI)) is a toxic pollutant requiring effective removal from industrial effluents.
• Trivalent chromium (Cr(III)) is often present in wastewater after Cr(VI) reduction processes.
• Developing stable and environmentally benign methods for Cr(III) removal is crucial.

Purpose of the Study:

• To investigate the efficiency of the ferrite process for removing Cr(III) from solutions generated by two different Cr(VI) reduction methods.
• To determine optimal treatment conditions for Cr(III) removal using the ferrite process.
• To characterize the resulting sludges and assess their environmental stability and pollution potential.

Main Methods:

• Cr(VI) reduction using sodium sulphite and ferrous sulphate.
• Ferrite treatment of Cr(III) solutions under varying conditions (pH, temperature, Fe2+/Cr3+ ratio).
• Sludge characterization using X-ray Diffraction (XRD) analysis and physical tests.
• Dissolution studies with various acids and EDTA.
• Toxicity Characteristic Leaching Procedure (TCLP) testing.

Main Results:

• Achieved approximately 100% Cr(III) removal under optimized conditions (pH 9, 50°C, 60 min) with specific Fe2+/Cr3+ ratios (16 for sodium sulphite process, 17.9 for ferrous sulphate process).
• Identified the spinel chromium-iron compounds formed as chromite (Cr2FeO4).
• Dissolution experiments and TCLP tests confirmed chromium concentrations in leached solutions were below the USEPA limit of 5 mg/L.

Conclusions:

• The ferrite process is highly effective for removing Cr(III) from industrial wastewater.
• The generated chromium-iron hydroxide sludges are environmentally stable, non-voluminous, and easily separable.
• This method offers a sustainable approach to managing chromium-containing effluents.