Development of gold plasmonic nanoparticles for detection of polydiallyldimethylammonium chloride at Umgeni water treatment plants: An optimised study and case application.

BACKGROUND

Polydiallyldimethylammonium chloride (poly-(DADMAC) is used in many drinking water treatment plants in most parts of the world as a flocculant to remove suspended solids from raw water. However, it is very important that residual poly-(DADMAC) is monitored because it disintegrates into a carcinogenic compound known as N-nitrosodimethylamine (NDMA) during the treatment of drinking water.

METHODS

In this work, the gold nanoparticle method is optimised for the detection of poly-(DADMAC), where the gold nanoparticles were stabilised with trisodium citrate and then used in quantifying poly-(DADMAC) by Ultraviolet-Visible-Near Infrared spectrophotometry. The optimised method was able to measure poly-(DADMAC) at low concentrations of 1.000 μg L in drinking water with limits of detection and limits of quantification of 0.3302 and 1.101 μg L, respectively.

SIGNIFICANT RESULTS

The method was applied to two different water treatment plants and the concentration of poly-(DADMAC) found during stages of the water treatment process ranged from 1.013 to 33.63 μg L. The average poly-(DADMAC) concentrate concentration that is dosed for coagulation in Umgeni Water plant A was 7.889 μg L while in plant B was 19.28 μg L. Residual poly-(DADMAC) concentration in drinking water was within the accepted limit of 50.00 μg L, regulated by the World Health Organisation (WHO).