KINETICS OF COPPER COMPLEXATION WITH DISSOLVED ORGANIC-MATTER USING STOPPED-FLOW FLUORESCENCE TECHNIQUE

This study provided direct observations on reaction kinetics of Cu and dissolved organic matter (DOM). Stopped-flow method and fluorescence technique were used to measure Cu(II)-DOM complexation over time. Suwannee River reference fulvic acid and water soluble soil organic matter were used as model DOM. Experimental conditions of pH 6, 5 x 10(-5) M Cu(II), and 5 mg C/L of DOM were used and the results were to simulate the relevant natural conditions. Both organic ligands reacted fairly rapidly with Cu(II). Reaction half-life of DOM was in the millisecond range. Two types of metal binding sites of organic ligands were identified. Fulvic acid yield forward rate constants: 1 x 10(6) M(-1) s(-1) and 5.15 x 10(3) M(-1) s(-1), based on second-order reaction rate model. Water soluble soil organic matter gave forward rate constants: 1.34 x 10(5) M(-1) s(-1) and 2.2 x 10(3) M(-1) s(-1). From comparison of kinetic natures, the fast-reacting ligands were comparable to nitrilotriacetic acid (NTA) and slow-reacting ligands were more like salcylic acid.