STUDIES OF WHOLE CRAWFISH SHELLS FOR THE REMOVAL OF CHROMIUM, LEAD, AND SELENIUM IONS IN SOLUTION

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Abstract
The objective of this work was to investigate the absorption characteristics, primarily with lead but also chromium and selenium ions in solution, of whole crawfish shells. An increase in the lead concentration in spiked water showed an increase in the lead absorption level. Lead absorbed by 0.5 g of whole crawfish shells was far less when compared to absorption by 0.5 g of ground crawfish shell powder due to particle size. Some of the lead is most likely being precipitated and collected along with the powder. With increase in the volume of lead spiked water, absorption of lead by whole crawfish shells also increased. Results obtained from the pH studies indicated that basic conditions (pH 9.5) are favorable for absorption of lead by both whole crawfish shells and chitin. Crawfish shells exhibited more absorption of lead compared to commercially available (shrimp) chitin at pH 9.5. Crawfish shells absorbed more lead, selenium, and chromium from analyte spiked water when compared to chitin. However, the amount of metal added was not always equal to the amount of metal dissolved. A higher amount of lead was absorbed when compared to chromium and selenium. If comparison was done in micrograms of analyte absorbed, then the absorption order can be given as lead>chromium>selenium. If comparison was done in micromoles of analyte absorbed, then the absorption order is as follows: chromium>lead>selenium. Results from the last experiment indicated that formation of lead precipitate increased proportionately with increase in the concentration of spiked water.

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