Highly colored industrial waste water is a serious environmental problem as it seriously discolors waterways as well as blocking sunlight for photosynthesizing plant species in the water. Now, researchers in Algeria have discovered that nothing more sophisticated than orange peel could be used to remove acidic dyes from industrial effluent. They describe their findings in a forthcoming issue of the International Journal of Environment and Pollution.
"Synthetic dyes are extensively used by industries including dye houses, paper printers, textile dyers, color photography and as additives in petroleum products," explains Benaïssa Houcine of the Laboratory of Sorbent Materials and Water Treatment, Department of Chemistry-Faculty of Sciences, at University of Tlemcen, in Algeria. "The effluents of these industries are highly colored, and disposal of these wastes into the environment can be extremely deleterious. Their presence in watercourses is aesthetically unacceptable and may be visible at concentration as low as 1 ppm (part per million).
In searching for an alternative to chemical treatment of waste water, Benaïssa has considered a common agricultural and food industry byproduct, orange peel. He has now tested waste orange peel as an absorbent for the removal of four acid dyes from simulated samples of polluted water.
The research demonstrates that absorption time depends on the initial concentration of the dyes as well as the chemical structures of the particular dyes being tested, but absorption can occur at just 25 Celsius rather than elevated temperatures. However, strong dyes including Nylosane Blue, Erionyl Yellow, Nylomine Red, and Erionyl Red were absorbed at between 40 and 70 milligrams per gram of orange peel from the samples.
"In laboratory-scale studies, the data show that orange peel has a considerable potential for the removal of dyes from aqueous solutions over a wide range of concentrations," Benaïssa says. "Orange peel may be used as a low-cost, natural and abundant source for the removal of dyes, and it may be an alternative to more costly materials. It may also be effective in removing other harmful or undesirable species present in the waste effluents."
Additional research is now needed in order to optimize and scale-up the process for the real-world clean-up of dye effluent. This will involve identifying the biochemical sites within the orange peel to which the dye molecules stick during absorption.