Effect of non-solvent additives on the morphology, pore structure, and direct contact membrane distillation performance of PVDF-CTFE hydrophobic membranes

Four common types of additives for polymer membrane preparation including organic macromolecule and micromolecule additives, inorganic salts and acids, and the strong non-solvent H2 O were used to prepare poly(vinylidene fluoride-co-chlorotrifluoroethylene)(PVDF-CTFE) hydrophobic flat-sheet membranes. Membrane properties including morphology, porosity, hydrophobicity, pore size and pore distribution were investigated, and the permeability was evaluated via direct contact membrane distillation(DCMD) of 3.5 g/L Na Cl solution in a DCMD configuration. Both inorganic and organic micromolecule additives were found to slightly influence membrane hydrophobicity. Polyethylene glycol(PEG),organic acids, Li Cl, Mg Cl2, and Li Cl/H2 O mixtures were proved to be effective additives to PVDF-CTFE membranes due to their pore-controlling effects and the capacity to improve the properties and performance of the resultant membranes. The occurrence of a pre-gelation process showed that when organic and inorganic micromolecules were added to PVDF-CTFE solution, the resultant membranes presented a high interconnectivity structure. The membrane prepared with dibutyl phthalate(DBP) showed a nonporous surface and symmetrical cross-section. When H2 O and Li Cl/H2 O mixtures were also used as additives, they were beneficial for solid–liquid demixing, especially when Li Cl/H2 O mixed additives were used. The membrane prepared with 5% Li Cl + 2% H2 O achieved a flux of24.53 kg/(m2·hr) with 99.98% salt rejection. This study is expected to offer a reference not only for PVDF-CTFE membrane preparation but also for other polymer membranes.     

垃圾焚烧中吸附剂对Cd、Pb迁移分布的影响

利用管式炉和模拟垃圾,研究了焚烧过程中SiO₂、Al₂O₃、CaO等吸附剂对重金属Cd、Pb迁移分布的影响规律,考察了不同吸附剂添加量、管式炉反应温度和停留时间的影响.结果表明,在各反应温度下,SiO₂、Al₂O₃、CaO均有利于Cd停留在底渣中;对于Pb,SiO₂、Al₂O₃亦使其易于停留在底渣中,而CaO在高温时表现为使Pb更易于向飞灰迁移.上述影响的程度均随着吸附剂添加量的增加而增加.当反应炉温度为850℃时,各吸附剂对于Cd的吸附效果顺序为CaO>Al₂O₃>SiO₂,对Pb的顺序为Al₂O₃>SiO₂>CaO.反应炉温度和停留时间的增加,也都易于使Cd、Pb向飞灰迁移.     

Concentrations and distribution of novel brominated flame retardants in the atmosphere and soil of Ny-Ålesund and London Island, Svalbard, Arctic

Novel brominated flame retardants (NBFRs) were investigated in Arctic air and soil samples collected from Ny-Ålesund and London Island, Svalbard, during Chinese scientific research expeditions to the Arctic during 2014–2015. The concentrations of Σ₉NBFRs in the Arctic air and soil were 4.9–8.7 pg/m³ (average 6.8 pg/m³) and 101–201 pg/g dw (average 150 pg/g dw), respectively. The atmospheric concentration of hexabromobenzene (HBB) was significantly correlated with that of pentabromotoluene (PBT) and pentabromobenzene (PBBz), suggesting similar source and environmental fate in the Arctic air. No significant spatial difference was observed among the different sampling sites, both for air and soil samples, indicating that the effects of the scientific research stations on the occurrence of NBFRs in the Arctic were minor. The fugacities from soil to air of pentabromoethylbenzene (PBEB), 2,3-dibromopropyl 2,4,6-tribromophenyl ether (DPTE), and decabromodiphenylethane 1,2-bis (pentabromophenyl) ethane (DBDPE) were lower than the equilibrium value, indicating a nonequilibrium state of these compounds between air and soil, the dominant impact of deposition and the net transport from air to soil. The correlation analysis between the measured and predicted soil-atmosphere coefficients based on the absorption model showed that the impact of the soil organic matter on the distribution of NBFRs in the Arctic region was minor. To the best of our knowledge, this work is one of the limited reports on atmospheric NBFRs in the Arctic and the first study to investigate the occurrence and fate of NBFRs in the Arctic soil.     

Chemodynamics of heavy metals in long-term contaminated soils：Metal speciation in soil solution

The concentration and speciation of heavy metals in soil solution isolated from long-term contaminated soils were investigated. The soil solution was extracted at 70% maximum water holding capacity (MWHC) after equilibration for 24 h. The free metal concentrations (Cd2+, Cu2+, Pb2+, and Zn2+) in soil solution were determined using the Donnan membrane technique (DMT). Initially the DMT was validated using artificial solutions where the percentage of free metal ions were significantly correlated with the percentages predicted using MINTEQA2. However, there was a significant difference between the absolute free ion concentrations predicted by MINTEQA2 and the values determined by the DMT. This was due to the significant metal adsorption onto the cation exchange membrane used in the DMT with 20%, 28%, 44%, and 8% mass loss of the initial total concentration of Cd, Cu, Pb, and Zn in solution, respectively. This could result in a significant error in the determination of free metal ions when using DMT if no allowance for membrane cation adsorption was made. Relative to the total soluble metal concentrations the amounts of free Cd2+ (3%–52%) and Zn2+ (11%–72%) in soil solutions were generally higher than those of Cu2+ (0.2%–30%) and Pb2+ (0.6%–10%). Among the key soil solution properties, dissolved heavy metal concentrations were the most significant factor governing free metal ion concentrations. Soil solution pH showed only a weak relationship with free metal ion partitioning coefficients (Kp) and dissolved organic carbon did not show any significant influence on Kp.     

固相萃取-气相色谱质谱联用法测定地表水中藻致嗅味物质

选用HLB固相萃取小柱进行富集,用二氯甲烷进行洗脱,优化了固相萃取过程,建立了固相萃取-气相色谱质谱法测定地表水中7种藻致嗅味物质的方法,浓度在0.004~0.1 mg/L范围内线性关系良好,具有较高的灵敏度和精密度,方法检出限为1×10-6~2×10-6mg/L,加标回收率为85.9%~108.6%,适用于地表水中嗅味物质的检测。     

Phase separation and regrowth of aerosol matter collected after size fractionation in an impactor

Aerosol matter in the size range <2 μm was collected in a Berner impactor and subsequently analysed by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectrometry. Owing to the low electron beam energy of 5 keV (occasionally 10 keV), analysis was restricted to elements with atomic numbers 20 (Ca). Sub-micrometer aerosol matter was found to contain mostly S, O, and C as well as some K and Ca. Nitrogen appeared to escape detection, probably due to bombardment-induced sublimation of NO₃ and NH₄. During sampling at low to moderate relative humidity (<60%) the sulphur-rich fraction of the aerosol matter (most likely sulphates) regrew in the form of microcrystals with sizes up to 10 times larger than the mean aerodynamic diameter of the respective impactor stage. By contrast, when sampling during periods in course of which the relative humidity exceeded 70%, the aerosol matter regrew in the form of extended amorphous agglomerates. The aerosol deposits also contained large numbers of carbon nanoparticles, well separated from the regrown sulphate-rich matter. The nanoparticles were similar in size (20–40 nm), much smaller than the equivalent aerodynamic diameter of the impacting particles (63 nm–2 μm). Presumably, the carbon nanoparticles constituted the core of larger air-borne particles covered with sulphates (as well as with nitrates and organic carbon). The regrown microcrystals disappeared rapidly under electron bombardment at high current density, an observation that indicates high volatility at elevated temperatures. Aerosol matter collected in the size range between 1 and 2 μm contained large fractions of particles made of O, Si, P, K, and Ca (oxides). These particles were highly resistant to electron bombardment (hard) and showed little or no evidence for agglomeration or regrowth. After removing the soluble (acidic) material from the collected aerosol matter, only carbon nanoparticles and hard coarse particles were left behind. The observation of agglomerated or crystallized “soft” aerosol matter in combination with phase separation of carbon nanoparticles lends further support to the assertion that it is not possible to collect useful quantities of fine and ultrafine aerosol particles with as-suspended morphology. Some implications for health-related research are discussed.     

Phase transformation of Cr(VI)-adsorbed ferrihydrite in the presence of Mn(II): Fate of Mn(II) and Cr(VI)

Ferrihydrite is an important sink for the toxic heavy metal ions, such as Cr(VI). As ferrihydrite is thermodynamically unstable and gradually transforms into hematite and goethite, the stability of Cr(VI)-adsorbed ferrihydrite is environmentally significant. This study investigated the phase transformation of Cr(VI)-adsorbed ferrihydrite at different pH in the presence of aqueous Mn(II), as well as the fate of Mn(II) and Cr(VI) in the transformation process of ferrihydrite. Among the ferrihydrite transformation products, hematite was dominant, and goethite was minor. The pre-adsorbed Cr(VI) inhibited the conversion of ferrihydrite to goethite at initial pH 3.0, whereas little amount of adsorbed Mn(II) favored the formation of goethite at initial pH 7.0. After the aging process, Cr species in solid phase existed primarily as Cr(III) in the presence of Mn(II) at initial pH 7.0 and 11.0. The aqueous Mn concentration was predominantly unchanged at initial pH 3.0, whereas the aqueous Mn(II) was adsorbed onto ferrihydrite or form Mn(OH)₂ precipitates at initial pH 7.0 and 11.0, promoting the immobilization of Cr(VI). Moreover, the oxidation of Mn(II) occurred at initial pH 7.0 and 11.0, forming Mn(III/IV) (hydr)oxides.     

兰州市大气OPAHs污染特征及潜在来源分析

对兰州市冬季（2016-12-01~07）和夏季（2017-08-03~10）大气气相和颗粒相（PM_1.0、PM_2.5和PM₁₀）中含氧多环芳烃（OPAHs）进行观测,结果显示：Σ₈OPAHs （气相+颗粒相）的浓度范围为1.83~19.28ng/m³,平均浓度为（6.45±3.43） ng/m³.冬季是夏季的2.06倍.冬季颗粒相OPAHs在2.5~10和<1.0μm粒径段均具有较大占比,而夏季则主要赋存于PM_1.0中.9-芴酮（9-FLU）、9,10-蒽醌（9,10-ANT）和苯并蒽酮（BZA）为OPAHs中最主要的几种单体物质,其占比为51.8%~94.9%.气粒分配机制研究结果表明：OPAHs在气粒两相间的分配以吸收机制为主导.基于浓度权重轨迹分析法（CWT）对兰州市大气中OPAHs的潜在污染源区进行了分析,发现其潜在污染源区在冬季主要位于当地及其西北方向位于新疆和青海境内的部分地区,而夏季则主要位于该研究区域的东南方向（定西市、天水市等）和东北方向（宁夏回族自治区中卫市）.     

基于硅酮母粒的两相分配气升式生物反应器处理氯苯废气的研究

疏水性污染物的去除是废气生物净化的难点.以硅酮母粒为非水相介质构建两相分配体系处理氯苯废气,结果表明,硅酮母粒对氯苯具有较高的亲和性,无生物毒性和生物降解性,且吸附于硅酮母粒表面的菌体对其相间分配系数没有明显影响.采用气升式生物反应器连续净化氯苯废气,当进气浓度为1000 mg·m~(-3)时,单相体系的去除率为60%;而添加了硅酮母粒的两相体系去除率达到90%,且CO_2矿化率较高,抗冲击负荷能力更好,说明硅酮母粒能有效强化气升式生物反应器净化氯苯废气的效果.该系统的最适硅酮母粒比例和停留时间分别为10%和90 s.以最大传质速率(β~*_s)来衡量氯苯的传质效果,发现硅酮母粒的添加使得β~*_s提升20%以上.