Removing Mercury (II) from Wastewater By Polymer-Enhanced Ultrafiltration

Mercury (II) is one of the most strictly regulated contaminants released from various anthropogenic emission sources to the aquatic environment. When transformed to an organic form of methylmercury, it will be the most toxic, persistent and bioaccumulative form of mercury in nature. This study deals with removal of mercury (II) from wastewater by polymer-enhanced ultrafiltration (PEUF) using polyvinylamine as the mercury-binding polymer. A mercury removal rate as high as 99% was obtained, which was otherwise impossible to achieve with conventional ultrafiltration. Over the feed mercury concentration range tested (0 - 50 ppm), the PVAm dosage used did not affect the mercury rejection significantly, while water flux was reduced at a higher dosage of PVAm. A flux vs pressure relationship typical of ultrafiltration of macromolecular solutes was observed because of the presence of the amine polymer in the system, and the limiting flux appeared to follow the gel layer formation model. The fouled membrane surface was cleaned periodically with dilute chloric acid to recover the membrane permeability. Mercury removal with the PEUF was also tested with a simulated chlor-alkali wastewater that contained mercury and other chemicals (i.e., sodium chloride and sulphate), and the accompanying compounds in the feed solution was shown to influence the performance of PEUF for mercury removal.