TO DISCOVER how to use a waste material to clean up hazardous chemicals is a notable achievement. To do so while working in a war zone is doubly impressive. But that, with a little help from some foreign friends, is just what Abdulsamie Hanano of Syria’s Atomic Energy Commission, in Damascus, has done. Over the past four years Dr Hanano, who works in the commission’s molecular-biology department, and his colleagues have developed a way to use the stones (or pits) of dates, a waste product of the fruit-packing industry, to clean up dioxins, a particularly nasty and persistent type of organic pollutant that can lead to reproductive and developmental problems, damage the immune system, and even cause cancer. Dioxins are produced mainly as a by-product of industrial processes.
Dr Hanano lit on date stones for this task for three reasons. One was that they are rich in oils of a sort that have an affinity for dioxins. The second was that, though they are not unique in this oil-richness, unlike other oil-rich seeds (olives, rape, sesame and so on) they have no commercial value. The third was that, despite lacking commercial value, they are abundant.
To gather the droplets, Dr Hanano and his colleagues first softened up their date stones by soaking them in water for two weeks. That done, they ground them up and centrifuged the result. This process separated the droplets from the rest of the gunk as a creamy emulsion. It was then a question of testing the emulsion’s ability to extract dioxins from water. As the group report in Frontiers in Plant Science, it did this well. The droplets’ phospholipid membranes proved no barrier to the passage of dioxins, which accumulated satisfactorily in the oil. One of Dr Hanano’s collaborators, Denis Murphy of the University of South Wales, in Britain, describes the droplets as acting like little magnets for dioxins. “Within a minute,” he says, “virtually all the dioxins are sucked out of a solution. It is very fast.”
In particular, the droplets absorbed 2,3,7,8-tetrachlorodibenzo-p-dioxin, an extremely toxic herbicide that was one of the constituents of Agent Orange, used to destroy vegetation by American forces during the Vietnam war. And, once the dioxins are inside the droplets, their affinity for the oil is such that they never leave. Disposing of them is just a matter of scooping up the droplets (which will eventually rise to the top of any water containing them) and destroying them safely in, say, a furnace.
Dr Hanano’s first idea for a practical use for his creation is to clean up fish farms. Though dioxin pollution in most parts of the sea is fairly low level, it tends to be higher near the coast, where fish farms are located, because of run-off from the land. Moreover dioxins, like certain other marine pollutants such as mercury and cadmium, are never destroyed or excreted, so accumulate progressively in the flesh of fish and shellfish. Cartridges containing dioxin-absorbing droplets, through which the impounded water of a fish farm was cycled, would help to stop that happening.
Remediating polluted land might also, the researchers hope, be on the cards, although they have yet to work out how to recover the droplets once the emulsion has been sprayed on the affected ground. If they can do so, however, the group are likely to have plenty of customers. Substances like 2,3,7,8-tetrachlorodibenzo-p-dioxin are so long-lived that even today the Vietnamese are still trying to clean up the mess Agent Orange created.