A new research performed at the University of Greenwich, London, is expected to bring in a solution for the reuse of waste glass bottles. The solution suggested by the research is anticipated to assist in the cleanup of the much polluted waterways by performing the role of an ion-exchange sieve to remove cadmium, lead and other types of toxic metals.
The research details will be published in the impending issue of Environment and Waste Management, an International publication.
World over only a small part of the waste glass jars and bottles are recycled because most of the glass products are colored in green or brown colors and the recycle market can accommodate only a part of the total wastes. As a result of these limitations,most of the waste products from all over Europe are sent to China or other parts of the world to grind them and use it as filling up substances in road construction projects.
The processing method developed by Nichola Coleman from the University of Greenwich, London, changes the waste glass container or cullet into tobermorite also known as hydrated calcium silicate, a material that can be easily retrieved from glass. The mineral retrieved in the phase-pure 11-angstrom form can be deployed as an ion-exchange material to remove cadmium ions and toxic lead from industrial discharges, contaminated ground water or waste water streams.
For the purpose of producing the tobermorite, Coleman heated the mix of caustic soda, lime and the ground cullet to 100° C level in a sealed container made of Teflon. The earlier tests revealed a slow process in the uptake of cadmium and lead from the solution and Coleman proposes the use of the synthetic mineral at the present stage of development in the in situ redress of ground water instead of the ex situ industrial waste filtration process. The concept is being tried to produce other categories of ion exchange filter.
To make the tobermorite, Coleman heated a mixture of ground cullet, lime (as a calcium source) and caustic soda (sodium hydroxide solution) to 100° C in a sealed Teflon container. Initial tests show that uptake of lead and cadmium from the solution are sluggish, so Coleman suggests that, at this developmental phase the artificial mineral can be used for in situ remediation of ground water rather than in industrial ex-situ waste matter filtration processes and this technique is extended to produce other classes of ion exchange filter from low-quality waste glass that cannot be recycled.