Influence of film stability and aging of plasma polymerized allylamine coated quartz particles on humic acid removal.

Plasma polymerized allylamine (ppAA) films have been successfully deposited on to the surface of quartz particles via a rotating barrel plasma reactor for humic acid removal. The films were deposited at a power of 25 W, allylamine flow rate of 4.4 sccm and polymerization times of 5 to 60 min. X-ray photoelectron spectroscopy was used to investigate the influence of short-term stirring in water and film age on surface chemistry. Stirring results in a reduction in the nitrogen concentration, which was greatest for shorter polymerization times. Film aging of up to 52 weeks appeared to result in a reduction in the concentration of C-N species. The influence of batch, recycling, and film age on humic acid removal was investigated. Humic acid removal appeared to be reproducible across three separate batches for polymerization times of 20 min or more, which was attributed to film thickness. Recycling of the ppAA films was most successful at pH 11 for up to 4 humic acid removal/regeneration cycles. Successful regeneration at pH 11 was attributed to electrostatic repulsion of the adsorbed humic acid molecules. Decreasing the pH of the regeneration solution reduced the number of successful regeneration cycles due to greater retention of adsorbed humic acid via electrostatic attraction. Film age appears to have minimal effect on humic acid removal where freshly deposited and 52-week-old films removed similar masses of humic acid. Successful production and development of ppAA coated quartz particles has resulted in a functional material that can be incorporated into a water treatment system to improve water quality.