Ion flotation removal of a range of contaminant ions from drinking water

Abstract

The effect of a natural, biodegradable surfactant obtained using a novel and efficient chemical reaction between cysteine (a thiol-based amino acid) and an octanoyl (C8) compound, was investigated for its application to the ion flotation removal of low levels of different contaminant ions from aqueous solution. The synthesised amino acid-based single-chain surfactant shows a high water solubility and exhibits extensive foaming in a typical flotation chamber over a wide pH range. In a batch ion flotation process, this surfactant was able to remove 97–99% of the 5ppm of strontium, lanthanum, arsenic and different heavy metal ion levels present in contaminated water, in a simple, single-stage physiochemical process; while this surfactant showed significantly lower efficiency for the removal of iron, selenium and gold ions. In a solution mixed with heavy-metal ions, including arsenic, copper, cadmium, magnesium, lanthanum, chromium, lead and iron, the surfactant shows high affinity to bind with arsenic, copper and chromium compared with the others. Moreover, the effectiveness of this surfactant for removal of gold ions from aqueous binary mixtures in the presence of iron and mercury ions has been explored. This new surfactant is highly efficient compared with commercial surfactants (e.g., SDS and CTAB) for ion flotation. Importantly it is an environmentally acceptable compound. It can be decomposed into cysteine (amino acid) and octanoic acid (caprylic acid, which is taken as a dietary supplement). The surfactant has the potential for wide usage in ion flotation and in froth flotation. Show more