Sorption of triclosan onto sediments and its distribution behavior in sediment–water–rhamnolipid systems

Abstract

Triclosan has been commonly used as an antimicrobial and disinfectant agent. Distribution between water and sediment plays a key role in its occurrence, transfer, and fate in the aquatic environment. Sorption of triclosan onto sediments and the effect of the biosurfactant rhamnolipid on distribution were studied in the present work. Batch equilibrium experiments were performed on three different sediments, with a wide triclosan concentration range. S-shaped equations can be used to describe the sorption behavior when triclosan concentration is relative high (50-250 µg · g⁻¹). The Pearl River, China (PR), sediment, which has the largest cumulative volume of pores, appeared to have great capability for continuously capturing triclosan. In the lower concentration range (10-150 µg · g⁻¹) assays, linear and Freundlich equations fitted the sorption isotherm data well. The pH value of sediment appeared to have a significant influence on sorption of low triclosan concentrations. Formation of rhamnolipid micelle remarkably decreased the sediment-water distribution ratio, K(d)*. Evaluation of the distribution efficiency, E, suggested that pores of sediment might have played a role in triclosan distribution, whereas sediment organic matter bound triclosan and reduced solubilization of triclosan. Rhamnolipid appears to be a good sorbent for triclosan. The findings of the present study suggest that, to understand the sorption and distribution of triclosan fully, studies should be carried out over a relatively broad concentration range.

Partitioning and Degradation of Triclosan and Formation of Methyl-Triclosan in Water-Sediment Systems

“…TCS is a weak acid (pKa 8.1), and the degree of deprotonation increases as the pH of the solution increases. As a result, the electrostatic repulsion enhanced between the ionized TCS and the sediment surface (Lin et al 2011). Except pH values, other physicochemical properties of DQL and DL sediments were similar.…”

“…) (Lin et al 2011). Low pH and high ion strength of the liquid phase increased the adsorption of TCS onto activated carbon, kaolinite, and montmorillonite, while the effect of humic acid was found very complex (Behera et al 2010).…”

“…Previously, Lindström et al (2002) reported the detection of TCS and M-TCS in Swiss lakes and found that sunlight exposure can rapidly decompose TCS but not M-TCS. Lin et al (2011) studied the adsorption of TCS onto river sediments and investigate the effect of rhamnolipid but did not study its degradation. To better understand the fate and behavior of TCS in aquatic environment, the partitioning and degradation processes were studied in this work using simulated watersediment systems.…”

On the Need and Speed of Regulating Triclosan and Triclocarban in the United States

“…85 Antimicrobials arriving at U.S. WWTPs in substantial quantities (227 000–454 000 kg/y for TCC and 170 000–970 000 kg/yr for TCS) 8 are known to break through WWTPs and subsequently can harm algae in surface waters at ng/L concentrations. 86 Detected concentrations have been observed to exceed an acute-based predicted no-effect concentration (PNEC) of 4.7 ng/L in the River Elbe at 75% of monitoring locations, 36 and can accumulate in sediments to mg/kg levels, 14,71,87,88 where they may persist for several decades. 71 In the U.S., sewage sludge is either incinerated (∼15% of total volume) which can release more carcinogenic dioxins from TCS, 24,89 or deposited in landfills (∼30%) and on land (∼55%), from where antimicrobials and their carcinogenic transformation products may leach into adjacent surface water to impact the composition of microbial communities.…”

A Random Forest approach to predict the spatial distribution of sediment pollution in an estuarine system

“…TOC was included, because the sorption properties of TCS results in a strong positive relationship between TOC and TCS concentration [7,22]. Sediment composition served as a hydrodynamic proxy, because sediment deposition is a function of flow speed and direction in Narragansett Bay [37–39], and the sorption of TCS to sediments and subsequent distribution are related [40]. Bathymetry was also included as a potential proxy for hydrodynamics because of its effects on sediment deposition [41,42].…”