Quick Dips

Knopping Off Heavy Wool

Scientists at the Wool Research Organisation of New Zealand (WRONZ) are getting into heavy metal, with a project that aims to use soft wool knops -- pea-sized spheres of crossbred wool fibres -- as a filter for removing heavy metals from effluent. The knops have previously proven useful in oil-spill containment and cleanup, and the researchers see the new application as providing another potentially valuable use for wool.

The new filter application capitalises on wool's complex chemical composition which enables it to absorb industrial contaminants, such as mercury, chromium and copper. The metals become bound into the fibre, enabling it to be removed from the environment and disposed of safely. This work will provide industries with a cost-effective means of reducing pollution in their effluent. The approach has potential for international development, as no other good methods of handling large volumes of effluent containing heavy metals have yet been developed.

Soft knops were originally developed and patented by WRONZ as a loose fill for bedding. During the research and trialling of soft knops, their lofty, hollow structure showed the ability to absorb and contain surprisingly large quantities of oil -- up to 40 times their weight. This discovery, combined with the wool fibre's ability to repel water from its surface and its biodegradability led WRONZ to develop Woolspill as a natural oil sorbent, which they patented in 1989.

Woolspill is now being used by local authorities to deal with oil spills. Other successful uses include oil spill protection and clean-up on industrial sites, soaking up leaking machinery oil, and freeing bilges of oil on ships. It has also been used in filtration systems to reduce oil contamination in water. This system is being used to remove petrol and oil from water washing off service station forecourts into stormwater drains, as well as cleaning up contaminated mixtures so that they can be discharged safely to trade waste systems.

Wool fibres are coated in a natural oil, lanolin, which repels moisture and so keeps the sheep warm and dry. Rolling the fibres into balls, in effect, encourages them to attract and absorb individual droplets of oils which become trapped within the knop structure, while water simply passes through.