The Power of Orange

October 27th, 2008 BY Hilary Feldman | No Comments

Many household cleaning products smell like fresh citrus fruit. Whether it’s lemon, lime, or orange, we associate those tangy scents with squeaky clean counters and floors. Invigorating, refreshing, and hygienic are words that spring to mind. Many shampoos and soaps also capitalize on this connection.

But what if there is more to the lowly orange peel? A new study in the International Journal of Environment and Pollution has examined the possibility of treating waste water with orange peel. In fact, industrial waste water is often an unappetizing shade – green, orange, blue, red – due to coloured compounds. Not just unsightly, the murky tinted water blocks sunlight, so that aquatic plants are prevented from photosynthesizing. Once plants are affected, the impact is felt along the entire food chain.

Coloured effluent is common from many industries, including those that use dyes – textile and paper mills – as well as photographic businesses, petroleum plants, and pharmaceutical manufacturers. It takes a surprisingly small amount of powerful dye to change water visibility. Colour changes may be visible at a mere one part per million.

Now how can these compounds be removed? One approach is to filter them out, using some substrate to absorb the dye molecules. Orange peel is one potential solution. It has been shown to remove different dyes, including Nylosane Blue, Nylomine Red, Erionyl Red, and Erionyl Yellow. Not only are the dyes absorbed, but orange peel is effective at normal temperatures (e.g. 25 degrees Celsius). Depending on the dye strength and structure, the process may take some time. But even strong dyes were bound at 40-70 milligrams per gram of peel. Another study found peel to be effective with Acid violet 17, another dye chemical.

If you live in a composting household, you may be familiar with the orange and its mysterious ways. It is one of the few fruits that is meant to decompose very slowly – so it should be chopped up into smaller bits or added sparingly. As a result, orange peel is a common waste product of both agriculture and food industries. Other possible uses have included as feed for livestock or for fermentation to produce methanol and ethanol. It is cheap, abundant, and a natural product – all positive features. Now that it is known to work in the lab, more applied tests are underway. In addition, the biochemical processes need to be described, so that other applications can be explored.

The entire issue of the journal is dedicated to biosorbents and wastewater treatment, with problems ranging from mine tailings to industry effluent. And potential agents are similarly varied, from yeast and other microorganisms to rice hulls and bark.

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