Scientists in the UK have used neutron scattering studies to develop a new way of separating silica nanoparticles from wastewater — which could prevent millions of tonnes of nanoparticles entering waterways every year.
Just a few tens of nanometres in diameter, such spheres of silica are being used in an increasing number of consumer products including cosmetics, medicines, cleaners and even food. As a result, sewage treatment plants have become a major gateway for nanoparticles entering the environment as treated effluent, sludge or both. Although there is no evidence that such nanoparticles pose an environmental threat, their ultimate fate is a mystery, because monitoring their presence in sewage has so far been impossible.
Now, scientists from the Centre for Ecology & Hydrology (CEH) and the ISIS neutron source have overcome this obstacle using small angle neutron scattering (SANS) — a technique that has been used to study a wide range of nanometre-sized structures. SANS involves firing a beam of low–energy neutrons through a sample and measuring the intensity of neutrons at small deviations from the transmitted beam.