Investigations of photochemical transformations of aqueous mercury: Implications for water effluent treatment technologies

Photochemical transformations of mercury were studied to determine its potential as a treatment mechanism to reduce mercury laden waters to trace concentrations. In this study, aqueous solutions of mercury nitrate in deionized water were exposed to UV irradiation and a gas purge. The impacts of purge gas (including rate and bubble size), UV irradiation wavelength, initial mercury concentration and time on mercury removal have been studied. Nitrogen purge with 254 nm UV irradiation resulted in the greatest net production of elemental mercury for all initial concentrations. These conditions followed pseudo first order kinetics and achieved the highest rate constant of 0.18 s^-1. As oxygen was introduced into the solution, the quantity of elemental mercury volatilized decreased but still resulted in significant mercury losses through volatilization up to 90% in 60 min. Overriding, the loss of elemental mercury from the solution is dependent upon the gas purge rate and bubble size.