Algerian researchers have discovered that orange peel could be used to remove acidic dyes from industrial effluent.

'Synthetic dyes are extensively used by industries including dye houses, paper printers, textile dyers, colour photography and as additives in petroleum products,' explained Benaïssa Houcine of the Laboratory of Sorbent Materials and Water Treatment, University of Tlemcen, Algeria.

'The effluents of these industries are highly coloured, 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 one part per million (PPM).

In searching for an alternative to chemical treatment of waste water, Benaïssa 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 degrees Celsius rather than elevated temperatures.

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, according to an Inderscience publication release.

'In lab-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 said.

'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 required to optimise 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.

These findings have been described in a forthcoming issue of the International Journal of Environment and Pollution.