Aqueous complexation of cadmium, lead, and copper by 2,4,6-trichlorophenolate and pentachlorophenolate

Abstract

The subsurface mobility of metals and polychlorinated phenols occurring together in contaminated groundwaters may be significantly affected by the extent of aqueous complexation between them. However, no previous experimental studies have examined these interactions. In light of this, the aqueous complexation of Cd, Pb, and Cu by both 2,4,6-trichlorophenolate (TCP −) and pentachlorophenolate (PCP −) has been studied at 25°C. Experimental data gathered by ion selective electrode potentiometry and ultraviolet spectrophotometry indicate that metal-chlorophenol complexation occurs, and we interpret the experimental data in terms of a single 1:1 complex in each system. The log stability constants for the complexes, with 2σ errors, are calculated to be: Cd(TCP) +, 2.5 ± 0.3; Pb(TCP) +, 3.0 ± 0.5; Cu(TCP) +, 4.9 ± 0.4; Cd(PCP) +, 2.9 ± 0.3; Pb(PCP) +, 2.8 ± 0.5; and Cu(PCP) +; 4.2 ± 0.4. Based on these values, a simple correlation technique has been applied to estimate stability constants involving other metals and chlorophenols. Calculations using these stability constants suggest that metal-chlorophenolate complexation can drastically alter metal and/or chlorophenol mobilities in contaminated groundwaters.