Graphite to remove arsenic from water
doi:10.1038/nindia.2016.76 Published online 13 June 2016
A highly efficient arsenic adsorbent has been made by modifying commercially available synthetic graphite with nanoparticles1. This adsorbent is potentially useful for removing arsenic from contaminated drinking water.
Current techniques for removing arsenic are expensive and time consuming. To devise a low-cost, simple method, the researchers synthesized the adsorbent by modifying the surface of synthetic graphite with zinc peroxide nanoparticles and mercaptopropionic acid.
They tested the arsenic removal efficiency of the adsorbent by separately adding arsenic solutions to an adsorbent-containing solution at room temperature. The adsorbent bound maximum arsenic at pH between 7.5 and 8.
This efficiency of the adsorbent is considered to be due to the presence of the surface nanoparticles that bind arsenic through forming a zinc arsenate complex. In addition, the positively charged surface of the graphite attracted negatively charged arsenic species through electrostatic interactions.
The adsorbent’s ability to remove arsenic increased with increasing adsorbent dose up to 0.05 grams.
Arsenic exists in contaminated water in two ionic forms: trivalent and pentavalent arsenic. The adsorbent completely removed trivalent and pentavalent arsenic after 110 and 75 minutes, respectively. The adsorbent also removed both forms of arsenic from tap water, suggesting that it could be used in remote resource-poor areas, where people cannot use costly systems like reverse osmosis, the researchers say.
1. Uppal, H. et al. Zinc peroxide functionalized synthetic graphite: an economical and efficient adsorbent for adsorption of arsenic (III) and (V). J. Chem. Environ. Eng. (2016) doi: 10.1016/j.jece.2016.05.038