Dynamic Sorptive Behavior of Tributyltin on Quartz Sand at Low Concentration Levels:  Effect of pH, Flow Rate, and Monovalent Cations

Abstract

The highly toxic organotin compounds which have been used as biocides in ship antifouling paints have been introduced into aquatic ecosystems. Among them, tributyltin (TBT) is the most important organotin compound which has been produced on the largest scale. Understanding its fate in the environment is therefore of primary importance to prevent its migration. TBT sorption from aqueous solutions was studied at much lower concentrations (10 nM to 2 μM) than those used in previous studies. Experiments were performed using column reactors filled with a quartz sand. The influence of physicochemical parameters on TBT partitioning, i.e. ionic strength, pH, and nature of electrolyte cation was investigated. Equilibrium times were short as TBT retention appeared to be independent of the mean pore velocity. TBT sorption was affected strongly by the pH and slightly by the ionic strength of the solution. Competitions with monovalent alkaline cations showed a small influence of Li+, Na+, K+, Rb+, with respect to Cs+ on TBT retardation. Moreover, the injection of two different TBT concentrations accounted for the nonlinearity of TBT sorption. The theory of nonlinear chromatography was used for the calculation of convex adsorption isotherms. Retardation factors and distribution coefficients were estimated.

Parameter estimation for reactive transport by a Monte‐Carlo approach

“…7 can be noted Eq. 8 ͓Td j ͔ ϭ fd j ͓͑T j ͔͒ and ͓Tf j ͔ ϭ ff j ͓͑T j ͔͒ for j ϭ 1 to Nx (8) where the total concentration T j is the sum of the mobile Td j , and nonmobile Tf j total concentration for each component. Sorption phenomena can be described easily by ion exchange or by surface complexation.…”

“…The reactive transport test-case we use has been given by Bueno et al 8,9 It is about transport of TBT through a natural quartz sand. These authors provide breakthrough curves of TBT at seven different pH.…”

“…These authors provide breakthrough curves of TBT at seven different pH. 8 This leads to seven different sets of Langmuir parameters. From Langmuir parameters obtained by these authors at pH ϭ 6.1, equilibrium constants and site concentration for the sorption of TBT onto the natural quartz sand can be calculated.…”

“…From Langmuir parameters obtained by these authors at pH ϭ 6.1, equilibrium constants and site concentration for the sorption of TBT onto the natural quartz sand can be calculated. Specific area of this sand is given by Bueno et al 8 All these parameters and the chemical reactions assumed in the system are summarized in Table 1. A measure of the point of zero charge (PZC) of the sand has been done.…”

“…A column experiment on sorption of tributyltin onto a natural quartz sand 8,9 at seven different pH is used as test case. We show the efficiency of the algorithm developed.…”