Abstract
The reported ability of cysteine and cystine to bind typical arsenic oxy-ions in water is used as a basis for a study of the potential for using a surfactant with a cysteine head-group for selective arsenic binding and removal in an ion flotation process. Several different head-group attachment methods are studied with cysteine and cystine and with single- and double-chain surfactants. A comparison of the properties of these surfactants with some other surface-active compounds, with groups like those on cysteine, suggest that few compounds have suitable characteristics for the efficient removal of low levels of arsenic from drinking water. An amino-acid-based single-chain surfactant is synthesized by reacting cysteine with octanoyl chloride to obtain octanoyl cysteine, which is then used in a study of selective ion flotation for the removal of low levels of arsenic from drinking water. This compound has high water solubility and causes extensive foaming in a typical flotation chamber and removed 99.4-99.9% of the 5 mg L-1 arsenic present in the contaminated water in a simple, single-stage ion flotation process, using either air or nitrogen gas. These laboratory results indicate that these surfactants can be useful in the large-scale treatment of low-level arsenic-contaminated water.