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Chromium recovery from electroplating rinsing waters using a novel metal exchange technology

IWRA World Water Congress 2017 - Cancun Mexico
2. Water quality, wastewater and reuse

Keyword(s): Chromium, wastewater, electroplating


Chromium is a metal used in a variety of industries such as tanneries, metallurgy, and metal electroplating. Wastewaters, specially rinsing waters, coming from these industries contains high concentrations of Cr(VI), the most toxic state of chromium. Chemical reduction of Cr(VI) to Cr(III) followed by chemical precipitation, ion exchange, adsorption, membrane filtration, are the main techniques used for treating such wastewaters. However, these processes are complex, expensive and generate hazardous wastes to be disposed off often in landfills. We have developped a new approach for chromium recovery using a filter filled with recycled iron and cellulose fibers. Laboratory and pilot scale tests demonstrated that we can reduce Cr(VI) concentrations from 10-50 ppm to as low as 20 ppb. pH and contact time (flow rate) were the two main parameters governing the process. It has been demonstated that upon the fibers were in contact with the wastewater, pH increases from 2-3 to as high as 8. Hence, under these pH conditions, Cr(III) ions generated by the reduction reaction between Fe and Cr(VI), precipitates as chromium hydroxide. Since, the mixture of cellulose and iron fibers are compacted in such a way to have a controlled porosity, the chromium hydroxide fine particles are retained inside the filter. Laboratory and pilot scale tests were very satisfactory and the technology is now ready for commercialization. This new technology was patented.

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