Trace mercury determination by trapping complexation: application in advanced oxidation technologies

G. CUSTO, M. I. LITTER, M. ORTIZ, D. RODRÍGUEZ, C. VÁZQUEZ

Budapest, Hungria

Conferencia; 11 th. Conference on Total Reflection X- Ray Fluorescence Analysis and Related Method (TXRF 2005); 2005

The extensive use of Hg compounds in agricultural applications as part of pesticides, herbicides, insecticides and bactericides determines its frequent presence in industrial wastewater.  It is well known that Hg species posses high noxious effects on the health of living organisms even at very low levels (5 mg/L). Nowadays, quantification of this element is an analytical challenge due to the peculiar physicochemical properties of all Hg species. The regulation of the maximal allowable Hg concentration led to the search of sensitive methods for its determination. Total Reflection X-Ray Fluorescence (TXRF) is a proved instrumental analytical tool for the determination of trace elements. In this work, use of TXRF for Hg determination is investigated. Because of volatilization of several mercury forms, a procedure to capture these volatile species in liquid samples by using different complexing agents is proposed.  Ammonium pyrrolidine-dithiocarbamate  (APDC), ethylenediaminetetracetic acid (EDTA) and oxalic acid were assayed for trapping the analyte into the solution during the preparation of the sample and onto the reflector during TXRF measurements. The proposed method was applied to evaluate Hg concentration during TiO2-heterogeneous photocatalysis, HP, one of the most known Advanced Oxidation Technologies (AOTs). AOTs are processes for the treatment of effluents in waters and air that involve the generation of very active oxidative and reductive species. In HP, Hg is transformed to several species under UV illumination in the presence of titanium dioxide. TXRF is a valuable tool to follow the extent of the HP reaction, by determining non-transformed Hg in the remaining solution.