Chromium is a common heavy metal contaminant of water supplies, largely arising from the textile, leather and wood production industries. Levels of chromium in drinking water have been controlled in the past by expensive, often toxic chemical-based cleansing procedures.
Xuesong Wang and co-workers at Huaihai Institute of Technology in Lianyungang1 have shown that walnut shells could provide a natural, cheap and easily available alternative to chemical cleaning.
Walnut shells have previously been used to successfully remove hydrocarbons such as benzene and toluene from water. In the new study, nutshells sourced locally in China were dried, ground up and tested as adsorbents of chromium VI, a known carcinogen, under various experimental conditions.
The nutshells were found to be capable of removing up to 97% of the chromium from water. They performed particularly well in acidic solutions and at high temperatures, but were adversely affected by high salt content — a potential drawback for practical use because industrial wastewater often contains large amounts of salt. Nonetheless, the walnut shells are among the best substances for adsorbing chromium VI when compared with previous studies, which have tested the adsorbent capacity of a range of other natural substances, including wool, coal and cacti.
The authors of this work are from:
Department of Chemical Engineering, Huaihai Institute of Technology, Lianyungang, China.
Thanks to Clive for this post!
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