Abstract
Sorptive landfill liners can prevent the migration of the leachate pollutants. However, their sorption ability will decrease over time. A method should be developed to maintain the sorption ability of landfill liners. In this study, we combined cetyltrimethylammonium bromide-bentonite (CTMAB-bentonite) and zero-valent iron (ZVI) to develop a self-cleaning liner that can retain its sorption ability for a long period. Batch experiments and calculation simulations were employed to analyse the sorption ability of this liner material and the ecological risk of halogenated hydrocarbons. The results showed that CTMAB-bentonite could sorb halogenated hydrocarbons well, with saturated sorption capacities (Qm) of 10.2, 14.5, 6.69, 18.5, 29.4, and 49.7 mg·g-1 for dichloroethane (DCA), trichloroethane (TCA), dichloroethene (DCE), trichloroethylene (TCE), tetrachloroethylene (PCE), and 1,3- dichloropropene (1,3-DCP), respectively. Using the mixture of 0.5 g iron and 0.5 g CTMAB-bentonite could dramatically increase the removal efficiency of DCE, TCE, and PCE. The reaction with ZVI did not change the structure of CTMAB-bentonite and its sorption ability remained consistent. Calculation results suggested that the self-cleaning landfill liner would dramatically decrease the hazard index (HI) of the eluate. However, the humic acid and salt in leachate would cause a reduction in the removal of halogenated hydrocarbons.
Highlights
Landfill leachate, containing various pollutants[1], is the second largest pollution source in a landfill
Iron has a redox potential of −0.44 V23, which is much lower than that of most halogenated hydrocarbons[24], making it an effective reductant under anoxic conditions
We examined the degradation of three halogenated hydrocarbons by the addition of zero-valent iron (ZVI)
Summary
Landfill leachate, containing various pollutants[1], is the second largest pollution source in a landfill. To prevent the migration of pollutants in leachate to groundwater, a sorptive landfill liner was developed in the present study[4]. The applied sorbents include active carbon[5,6], natural zeolite[7], organically modified kaolin[8], and hexadecyltrimethyl ammonium bromide (HDTMA)-bentonite[9] Among these sorptive materials, organobentonite was reported to be an excellent sorbent to sorb various organic pollutants from the aqueous phase[10,11,12,13,14,15]. The addition of ZVI to the landfill liner would allow the sorbed halogenated hydrocarbons to be degraded. This study aimed to develop a self-cleaning landfill liner to control the risk of halogenated hydrocarbons in leachate. The results of this work could provide essential data for building a self-cleaning landfill liner
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