Abstract
The sorption of hexabromocyclododecanes (HBCDs) on sediment affects the fate and transport of HBCDs in rivers. The sorption of HBCDs on sediment from the Weihe River was investigated by performing batch equilibration experiments, and the effects of changing the pH ionic, strength, and humic acid concentration (HA) on sorption were evaluated. The obtained results indicated that fast rather than slow sorption was the dominant process. Nonlinear sorption isotherms were acquired, and the Freundlich (R2 0.94–0.98) and Langmuir (R2 0.95–0.99) models both described the sorption of HBCDs well. The adsorption capacity for α-HBCD, β-HBCD, and γ-HBCD were calculated using the Langmuir model, and were 443.56, 614.29 and 1146.37 mg/kg, respectively. Thermodynamic analysis shows that HBCDs sorption on sediment is a spontaneous exothermic process. HBCDs sorption was affected by the HA concentration and ionic strength. The amounts of HBCDs sorbed to the sediment decreased as the ionic strength increased, and first increased and then decreased as the HA concentration increased. Changes in pH did not clearly affect the sorption of HBCDs. Synchrotron radiation Fourier-transform infrared spectra (SR-FTIR) was used to characterize the adsorption mechanism, and the obtained result indicated that hydrophobic interactions dominated the mechanism involved in HBCDs sorption on sediment.
Highlights
Hexabromocyclododecanes (HBCDs) is a widely used brominated flame retardant
Synchrotron radiation Fourier-transform infrared spectra (SR-Fourier-transform infrared infrared (FTIR)) was used to characterize the adsorption mechanism, and the obtained result indicated that hydrophobic interactions dominated the mechanism involved in HBCDs sorption on sediment
These results indicated that adsorption of HBCD to sediment was favorable
Summary
Hexabromocyclododecanes (HBCDs) is a widely used brominated flame retardant. Γ-HBCD is the dominant diastereoisomer, and contributes 70–89% of the total HBCD mixture [4,5]. Despite the commercial benefits of using HBCD, HBCDs have been classed as persistent organic pollutants under the Stockholm Convention in 2013 [8]. Like many other persistent organic pollutants, HBCDs can be released to the environment during manufacture, use, or disposal and can accumulate in environmental media, because they are strongly hydrophobic and poorly biodegradable [1,3,9]. HBCDs have been detected in various environmental matrices, including biota, municipal wastewater, sewage sludge, soil, and stream sediment [10,11,12]. HBCDs in the environment can cause toxic effects (e.g., endocrine disruption, liver function disruption, and neurotoxic effects) in biota [13,14,15]
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