Assessment of polybrominated diphenyl ether contamination and associated human exposure risk at municipal waste dumping sites

Polybrominated diphenyl ethers and their alternatives in soil cores from a typical flame-retardant production park: Vertical distribution and potential influencing factors

With the prohibition on the production and use of polybrominated diphenyl ethers (PBDEs), decabromodiphenyl ethane (DBDPE) and organophosphate flame retardants (OPFRs) have emerged as their alternatives. However, the vertical transport and associated influencing factors of these chemicals into soil are not clearly understood. To clarify the vertical distribution of the pollutants and related influencing factors, surface soil and soil core samples were collected at a depth in the range of 0.10-5.00 m in a typical 20-year-old flame-retardant production park and surrounding area. PBDEs and DBDPE show a clear point source distribution around the production park with their central concentrations up to 2.88 × 104 and 8.46 × 104 ng/g, respectively. OPFRs are mainly found in residential areas. The production conversion of PBDEs to DBDPE has obvious environmental characteristics. The vertical distribution revealed that most of the pollutants have penetrated into the soil 5.00 m or even deeper. The median concentrations of deca-BDE and DBDPE reached 50.9 and 9.85 × 103 ng/g, respectively, even at a depth of 5.00 m. Soil organic matter plays a crucial role in determining the vertical distribution, while soil clay particles have a greater impact on the high molecular weight and/or highly brominated compounds.

Insight into the application of magnetic molecularly imprinted polymers in soil-washing effluent: Selective removal of 4,4'-dibromodiphenyl ether, high adaptivity of material and efficient recovery of eluent

Soil washing techniques can effectively remove soil polybrominated diphenyl ethers (PBDEs), but further removal of PBDEs from washing effluent is disrupted by environmental factors and coexisting organic matter. Hence, this work prepared novel magnetic molecularly imprinted polymers (MMIPs) to selectively remove PBDEs in soil washing effluent and recycling surfactants, with Fe₃O₄ nanoparticles as the magnetic core, methacrylic acid (MAA) as the functional monomer, and ethylene glycol dimethacrylate (EGDMA) as the cross-linker. Later, the prepared MMIPs were applied to adsorb 4,4'-dibromodiphenyl ether (BDE-15) in Triton X-100 soil-washing effluent and characterized by scanning electron microscopy (SEM), infrared spectrometry (FT-IR), nitrogen adsorption and desorption experiments. According to our observations, BDE-15 equilibrium adsorptions on dummy-template magnetic molecularly imprinted adsorbent (D-MMIP, 4-bromo-4'-hydroxyl biphenyl as template) and part-template magnetic molecularly imprinted adsorbent (P-MMIP, toluene as template) were reached within 40 min, and their equilibrium adsorption capacities were 164.54 μmol/g and 145.55 μmol/g, respectively, with imprinted factor α > 2.03, selectivity factor β > 2.14, and selectivity S > 18.05. MMIPs exhibited good adaptability to pH, temperature, and cosolvent. Our Triton X-100 recovery rate reached as high as 99.9%, and MMIPs maintained a more than 95% adsorption capacity after being recycled five times. Our results offer a novel approach to selectively remove PBDEs in soil-washing effluent, with efficient recovery of surfactants and adsorbents in soil-washing effluent.

Treatment of PBDEs from Soil-Washing Effluent by Granular-Activated Carbon: Adsorption Behavior, Influencing Factors and Density Functional Theory Calculation

Soil-washing is a potential technology for the disposal of soil contaminated by e-waste; however, the produced soil-washing effluent will contain polybrominated diphenyl ethers (PBDEs) and a large number of surfactants, which are harmful to the environment, so the treatment of PBDEs and the recycling of surfactants are the key to the application of soil-washing technology. In this study, coconut shell granular-activated carbon (GAC) was applied to remove PBDEs from Triton X-100 (TX-100) surfactant which simulates soil-washing effluent. The adsorption results show that, GAC can simultaneously achieve effective removal of 4,4′-dibromodiphenyl ether (BDE-15) and efficient recovery of TX-100. Under optimal conditions, the maximum adsorption capacity of BDE-15 could reach 623.19 μmol/g, and the recovery rate of TX-100 was always higher than 83%. The adsorption process of 4,4′-dibromodiphenyl ether (BDE-15) by GAC could best be described using the pseudo-second-order kinetic model and Freundlich isothermal adsorption model. The coexistence ions had almost no effect on the removal of BDE-15 and the recovery rate of TX-100, and the solution pH had little effect on the recovery rate of TX-100; BDE-15 had the best removal effect under the condition of weak acid to weak base, indicating that GAC has good environmental adaptability. After adsorption, GAC could be regenerated with methanol and the adsorption effect of BDE-15 could still reach more than 81%. Density functional theory (DFT) calculation and characterization results showed that, Van der Waals interaction and π–π interaction are dominant between BDE-15 and GAC, and hydrogen bond interactions also exist. The existence of oxygen-containing functional groups is conducive to the adsorption of BDE-15, and the carboxyl group (-COOH) has the strongest promoting effect. The study proved the feasibility of GAC to effectively remove PBDEs and recover surfactants from the soil-washing effluent, and revealed the interaction mechanism between PBDEs and GAC, which can provide reference for the application of soil-washing technology.