Migration and leaching risk of extraneous antimony in three representative soils of China: Lysimeter and batch experiments

Antimony (Sb) distribution, solubility and mobility onto natural soils of China were studied in lysimeter and batch experiments as a function of physicochemical properties of the soil. An outdoor lysimeter experiment investigated the leaching and migration of Sb in the soils with Sb-polluted topsoil and unpolluted subsoil over a 5 month period. Soil solutions were collected by suction cups installed at different depth of lysimeters, and leachates were regularly collected and analyzed for Sb concentrations. The majority of the added Sb was retained in the topsoil layers, but small portions were moved to the sub-layers. Sb concentrations in the soil solutions and leachates ranged from 0–755.5 (6.38 ± 54 on average) μg l⁻¹ and 0–0.45 (smaller than the detection limit) μg l⁻¹ respectively, indicating the low solubility of Sb in the soils. Batch experiments were performed in order to determine the sorption capacity and the partition coefficient (K_d). Freundlich isotherm described properly the equilibrium experimental data and results show that the K_d values for Primosol, Isohumosol, Ferrosol equal to 22.5, 87.8, 704 L kg⁻¹, respectively. These results showed the strong capacity of the soils to retain Sb, and prevent it being leached down the profile. The mobilizable Sb was in the order: Primosol > Isohumosol > Ferrosol. Sb migration in the soils was mainly associated with the exchangeable, carbonate-bound, and metal–organic complex-bound fractions. Health risk assessment indicates that Sb leaching from Ferrosol will not harm to human health through groundwater under the test conditions, while it has certain health risks from the Isohumosol and Primosol.     

Sorption of apolar and polar organic contaminants by waste tire rubber and its chars in single- and bi-solute systems

Single- and bi-solute sorption of organic compounds [1,3-dichlorbenzene (DCB), 1,3-dinitrobenzene (DNB) and 2,4-dichlorophenol (DCP)] on ground tire rubber and its chars was studied. The chars were prepared by pyrolyzing tire rubber at different temperatures (200-800 °C). Their surface area, aromaticity and hydrophobicity increase greatly with pyrolytic temperature, and the polymeric phase is partly converted into a condensed phase. The sorption of DNB and DCP increases with pyrolytic temperature and is characterized by a transition from a partition dominant to an adsorption dominant process. However, the sorption of DCB linearly decreases with the pyrolytic temperature. The enhanced adsorption of DNB and DCP on carbonized phase is primarily attributed to nonhydrophobic interactions such as π-π electron-donor-acceptor interactions and/or H bonding. The higher partition of DCB to polymeric phase is attributed to its high hydrophobicity. Competitive sorption between DCB and DCP on the tire chars is highly dependent on dissociation of the latter.     

Investigation of partitioning mechanism for volatile organic compounds in a multiphase system

Laboratory experiments were performed to investigate the partitioning behavior of a set of diverse volatile organic compounds (VOCs). After equilibration at a temperature of 25 °C, the VOC concentrations were measured by headspace method in combination with gas chromatography/mass spectrometry (GC/MS). The obtained data were used to determine the partition coefficients (K_P) of VOCs in a gas-liguid-solid system. The results have shown that the presence and nature of solid materials in the working solution control the air-water partitioning of dissolved VOCs. The air/solution partitioning of BTEX and C₉-C₁₀ aldehydes was most affected in the presence of diesel soot. K_P values decreased by a factor ranging from 1.5 for toluene to 3.0 for ethylbenzene. The addition of mineral dust in the working solution exhibited greater influence on the partitioning of short aldehydes. K_P values decreased by a factor of 1.8. The experimental partition coefficients were used to develop a predictive model for partitioning of BTEX and n-aldehydes between air, water and solid phases.     

Sorptive domains of pine chars as probed by benzene and nitrobenzene

Chars were generated by pyrolyzing pine wood at temperatures between 300 °C and 700 °C for 6 h and at 500 °C for 10-300 min. Their organic content and surface acidity decreased, and BET surface area increased, with increasing pyrolytic temperature and time. The uptake of benzene and nitrobenzene increased with increasing pyrolytic temperature and time with isotherms characterized by a transition from less to more concave-downward. The isotherms with low-temperature and short-time chars were fitted to the dual Langmuir-partition model, whereas those with high-temperature chars to the dual-Langmuir model. Calculations suggest that the organic phases of chars functioned as partition media and the uptake of benzene and nitrobenzene on carbonized chars occurred first in micropores via pore-filling and later in larger pores through capillary condensation and adsorption. It is concluded that chars may be considered to consist of the partition domain, the high-energy micropores domain and the low-energy large pores domain.     

1,2,4,5-四氯苯 C 18 Empore TM 膜/水分配系数的研究

研究了1,2,4,5-四氯苯在C18膜／水相之间的分配规律。1,2,4,5-四氯苯在：25℃,80r／min条件下恒温震荡96h可达分配平衡,温度和盐度对1,2,4,5-四氯苯C18膜／水的分配过程影响很小,1,2,4,5-四氯苯C18膜／水分配平衡时间受溶液体积和容器容积的影响,但不受溶液中C18膜膜量的影响,推测脂溶性小于或接近1,2,4,5-四氯苯的有机污染物在恒温震荡条件下C18膜与水之间的分配96h可达到平衡。