Cotton Bleaching Process Cuts Energy, Wastewater

Researchers from the University of Georgia and China’s Donghua University and Dymatic Chemicals have developed a method that can reduce the amount of energy needed for — and the amount of wastewater produced in — the cotton bleaching process, while improving the quality of the end product.

The technique is described in A Novel Low Temperature Approach for Simultaneous Scouring and Bleaching of Knitted Cotton Fabric at 60°C. The article has been published in the journal Industrial & Engineering Chemistry Research.

The cotton industry’s current whitening techniques require bleaching the natural fiber at very high temperatures with hydrogen peroxide. Although this method results in the bright white material consumers have grown so fond of, it also lowers the quality of the material and takes a lot of energy to carry out. The team targeted its efforts toward lowering the bleaching technique’s high temperatures.

The team developed a compound that, when used with hydrogen peroxide, drops the bleaching temperature down to 140 degrees Fahrenheit from 200 degrees. The authors estimate that 60-degree difference would result in a process requiring less than half the energy as the commercial technique.

It also produced less wastewater, improved the weight of the material by removing less cotton substance during the process and performed its original function — whitening the cotton. While the report contains no figures for the wastewater reduction, it describes the difference as “significant.” The removal of less substance from cotton also resulted in a lower chemical oxygen demand in the wastewater, providing additional environmental benefits.

Since many materials destined to become clothing eventually take on various hues, the scientists also tested dyes and found the cotton bleached at the lower temperature could be made just as vibrant as its high-heat counterpart. They successfully showed the treatment’s effectiveness on knitted cotton fabric in commercial scale trials.

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