doi:10.1038/nindia.2013.56 Published online 26 April 2013
Researchers have devised an ecofriendly process for producing a new nanohybrid that can remove mercury from contaminated water1. This nanohybrid contains sulphur nanoparticles and reduced graphene oxide and is produced by treating graphene oxide and sodium thiosulphate with lemon juice and water under ambient conditions.
Even at low concentrations, mercury is harmful to living organisms. Current techniques for removing mercury use toxic chemicals and are time consuming. Natural chemicals and nanomaterials can be used in environmentally friendly processes for removing such toxic chemicals from contaminated water.
To find a novel ecofriendly way to make a mercury absorber, the researchers synthesized graphene oxide and then added it to sodium thiosulphate solution to which they added lemon juice. The organic acids in lemon juice helped make sulphur-nanoparticle-decorated reduced graphene oxide (SRGO). The researchers then evaluated the mercury-removal efficiency of SRGO.
About 90% of mercury ions were removed after 15 minutes at neutral pH under ambient conditions. SRGO almost completely removed mercury ions after 30 min. SRGO selectively adsorbed mercury ions in the presence of other metal ions such as zinc, cadmium and copper. During removal, mercury ions bound to sulphur nanoparticles.
The adsorption capacity of SRGO was observed to decrease only slightly with increasing reuse cycles. Its mercury-removal efficiency did not significantly decline even after three cycles, suggesting that SRGO is reusable.
"This nanohybrid can be used to remove only mercury ions in water purification," says Niranjan Karak, a co-author of the study.
The authors of this work are from: Advanced Polymer and Nanomaterial Laboratory, Department of Chemical Sciences, Tezpur University, and Defence Research Laboratory, Tezpur, India and Department of Material Science and Engineering, Yonsei University, Seoul, South Korea.