One dimensional-ZnO nanostructures: Synthesis,properties and environmental applications

One-dimensional (1D) zinc oxide (ZnO) nanostructures such as rods, wires, belts and tubes have attracted much attention due to their unique physical, chemical, optical, and electrochemical properties enabling remarkable performance in photonics, sensors, photocatalysis, optics and photovoltaic devices. This paper presents a review of recent research in 1D ZnO nanostructures with emphasis on ZnO-based nanowires (NWs or NRs) used as photocatalysts for the degradation of environmental pollutants, particularly textile and industrial dyes, under appropriate light irradiation. Compared to other ZnO nanostructures, the higher aspect ratio (large surface to volume ratio) of 1D ZnO NWs offers highly desirable photocatalytic applications that depend on surface reactions or other phenomena that occur at interface surfaces, and eliminate the cost and requirement for post treatment. In addition, a review of several syntheses, fabrication methods and characterization studies of several types of ZnO NWs is presented. Finally, the photocatalytic degradation of selected dyes is highlighted.     

海泡石和菌根修复重金属污染土壤研究

通过盆栽试验,研究了向重金属Pb、Zn、Cd复合污染的土壤中单一或联合添加海泡石和菌根Glomus mosseae、Glomus intraradices对玉米生长及玉米体内重金属浓度的影响。结果表明：联合使用海泡石和菌根Glomus intraradices可显著增加玉米地上部和根部的生物量;与单一处理相比,联合使用海泡石和两种菌根可使菌根对玉米的侵染率提高44.53%~58.80%。海泡石可有效阻隔土壤中的重金属向植株迁移,从而显著降低玉米体内Pb、Cd、Zn的浓度;而另一方面,两种菌根会促进植株体内Pb、Cd、Zn的富集,因此,可利用这两种菌根和一些非经济性作物来去除土壤中的Pb、Cd、Zn。     

Heavy metal stabilization in contaminated road-derived sediments

There is increasing interest in the stabilization of heavy metals in road-derived sediments (RDS), to enable environmentally responsible reuse applications and circumvent the need for costly landfill disposal. To reduce the mobility of heavy metals (i.e. Cu, Pb and Zn) the effectiveness of amendments using phosphate, compost and fly ash addition were investigated using batch leaching experiments. In general, phosphate amendments of RDS were found to be ineffective at stabilizing heavy metals, despite being used successfully in soils. Phosphate amendment resulted in enhanced concentrations of dissolved organic carbon (DOC), which increased the solubilisation of heavy metals via complexation. Amendment with humified organic matter (compost) successfully stabilized Cu and Pb in high DOC leaching RDS with an optimum loading of 15-20% (w/w). Compost, however, was ineffective at stabilizing Zn. Increasing the pH by amending RDS/compost blends with 2.5-15% (w/w) coal fly ash resulted in the stabilization of Zn, Cu and Pb. However, above a pH of ∼ 7.5 and 8 enhanced leaching of organic matter resulted in an increase in leached Cu and Pb, respectively. Accordingly, the optimum level of fly ash amendment for the RDS/compost blends was estimated to be ca. 10%. Boosted regression trees analysis (BRT) of the data revealed that DOC accounted for 56% and 65% of the Cu and Pb leaching, respectively, whereas pH only accounted for ca. 18% of Cu and Pb leaching. RDS sample characteristics (i.e. metal concentrations, size fractionation and organic matter content) were more important at reconciling the leaching concentrations of copper Cu (27%) than Pb (16%). The most important parameter explaining Zn leaching was pH. Overall, the choice of a suitable stabilization agent/s depends on the composition of RDS with respect to the amount of organic matter present, and the sorption chemistry of the heavy metal of interest.     

Enhanced electrokinetic remediation of cadmium-contaminated natural clay using organophosphonates in comparison with EDTA

Soil contamination by metals is a worldwide environmental problem. Electrokinetic extraction is a promising technology for in-situ remediation of contaminated soils of low hydraulic permeability. However, the extraction of metals is usually hindered by the high buffer capacity of natural soils. Organophosphonates are strong metal chelates as ethylenediaminetetraacetic acid(EDTA) which has been widely studied in the enhancement of electrokinetic remediation. In this study, batch desorption experiments and bench-scale electrokinetic extraction experiments were carried out to study the effect of two organophosphonates, i.e.,(nitrilotrimethylene)triphosphonate(NTMP) (ethylenedinitrilo)-tetramethylenephosphonate(EDTMP), on the extraction of cadmium from a natural clay in comparison with EDTA. Results of the batch desorption experiments showed that more than 75% of the sorbed cadmium could be dissolved into solution using 0.1 mol·L~(-1) organophosphonates or EDTA in the wide p H range of 1–11. Results of the electrokinetic extraction experiments showed that the cadmium spiked in the specimen migrated towards the anode with the enhancement of NTMP,EDTMP, and EDTA under a constant voltage gradient of approximately 1.0 V·cm-1. Although cadmium mobilization enhanced by EDTA was more efficient than that by the organophosphonates, accumulation of cadmium was observed in the vicinity of the anode. The average removal efficiencies of cadmium from the soil after approximately 5 days of electrokinetic extraction enhanced by 0.1 mol·L-1 NTMP(22.8%) and EDTMP(22.4%) were higher than that by 0.1 mol·L~(-1) EDTA(15.1%).     

Biochar-mediated regulation of greenhouse gas emission and toxicity reduction in bioremediation of organophosphorus pesticide-contaminated soils

Organophosphorus pesticides (OPPs) are a set of toxic persistent organic pollutants (POPs) present in the environment. Recently, biochar-mediated bioremediation has exhibited many advantages over conventional methods for the remediation of pesticide-contaminated soil. In the present study, biochar and nitrogen fertilizer (NH₄NO₃) were employed to remediate OPP-contaminated soil and the greenhouse gas (GHG) emission during 90 days of incubation was investigated. After thermal desorption treatment, the content of organophosphorus pesticides reduced from 175.61 μg·kg^-1 to 62.68 μg·kg^-1. The addition of NH₄NO₃ in the following bioremediation led to larger reduction (34.35%) of the pesticide concentration than that of biochar (31.90%) for the contaminated soils with thermal desorption treatment, while the simultaneous addition of biochar and NH₄NO₃ led to the largest reduction of pesticide concentration (11.07%) for the soil without thermal desorption treatment. The addition of biochar and NH₄NO₃ only slightly increased the emission rate of GHGs from the soil without thermal treatment, but remarkably increased the emission rate of GHGs from the soil after thermal treatment. In most cases, the addition of NH₄NO₃ is more effective than biochar to promote the degradation of pesticide, but also exhibited higher GHG emission. The microbial community analysis suggests that the enhanced degradation of pesticide is mainly owing to the increased activity of microorganism.     

Soil flushing by surfactant solution: pilot-scale demonstration of complete technology

This paper mainly relates to the real polychlorinated biphenyl (PCB)-contaminated soil flushing process, in which an aqueous solution of anionic surfactant was passed through sandy soil having an average concentration 34.3 mg/kg of dry matter. The goal of the treatment was to decrease the PCB concentration in the soil to less than 10 mg/kg, which is a limiting value if the soil is to be used in the field of civil engineering. The laboratory part was focused on the demonstration of the suggested method for estimating the CMC value of the surfactant used for leaching the PCBs from the soil to the solution. The estimate was based on a set of batch experiments carried out with the same soil as the soil used for the pilot-scale experiments. Theoretically, all effects affecting the CMC should be considered in an estimated value. The experimental facility used for the pilot-scale demonstration consisted of a steel column (3 m in length, 1.5 m in diameter) containing 1.7 m(3) of polluted soil and a liquid circulation system, by which an aqueous solution of a surfactant was supplied to the soil. Spolapon AOS 146 (anionic surfactant) solution (40 g/L) was passing through the soil column for 2.5 months. The concentration of the surfactant and PCBs in the aqueous soil extract was monitored during this time period. The final PCB concentration profile in the soil was determined after stopping the liquid flow. After passing through the soil, the PCBs containing the aqueous extract was pumped out from the steel column bottom to a treatment unit, where it was processed by coagulation. The final PCB concentration profile in the soil was compared with the results of the theoretical model, which is also described in the paper. The time necessary to reach the limit demanded was estimated to move within the range from 6 to 12 months.     

Fenton-Like Oxidation of Polycyclic Aromatic Hydrocarbons in Soils Using Electrokinetics

An integrated electrochemical oxidation process that utilizes electrokinetics (EK) to deliver the oxidant (5–10% hydrogen peroxide, H2O2) and chelant [40 mM of ethylenediaminetetraacetic acid (EDTA) or diethylenetriaminepentaacetic acid (DTPA)] or iron chelate (1.4 mM Fe-EDTA or Fe-DTPA) to oxidize polycyclic aromatic hydrocarbons (PAHs) in soils was investigated. Batch and bench-scale EK experiments were conducted using: (a) kaolin, a low permeability clayey soil, spiked with phenanthrene at 500 mg/kg, and (b) former manufactured gas plant (MGP) soil, a high buffering silty soil, contaminated by a variety of PAHs (1493 mg/kg). Batch experiments showed that chelant solutions dissolve native iron minerals to form soluble Fe-chelates that remain available even at higher pH conditions of soil for the Fenton-like oxidation of the PAHs. In EK experiments, a 5–10% H2O2 solution was delivered from the anode and a chelant solution or iron-chelate was delivered from the cathode. Preflushing of soil with 5% ethanol and ferrous sulfate (1.4 mM) prior to oxidant delivery was also investigated. An electric potential of 2 VDC/cm was applied in all tests to induce electroosmotic flow for 5–8 days for kaolin and 25 days for the MGP field soil. In the absence of any chelating agent, phenanthrene oxidation was catalyzed by native iron present in kaolin soil, and 49.8–82.3% of phenanthrene was oxidized by increasing H2O2 concentration from 5–10%. At 5% H2O2 concentration, phenanthrene oxidation was not increased by using 40 mM EDTA, 40 mM DTPA or 1.4 mM Fe-DTPA, but it increased to 70% using 1.4 mM Fe-EDTA. Maximum phenanthrene oxidation (90.5%) was observed by 5% ethanol preflushing and then treating with 5% H2O2 at the anode and 1.4 mM Fe-EDTA at the cathode. However, preflushing with 1.4 mM ferrous sulfate did not improve phenanthrene oxidation. The results with the MGP field soil indicated that delivery of 5% H2O2 alone resulted in oxidation of 39.8% of total PAHs (especially 2- and 3-ring PAHs). The use of EDTA and Fe-EDTA did not increase PAHs oxidation in this soil. Overall, the results reveal that an optimized in situ combined technology of EK and Fenton-like process has the potential to oxidize PAHs in low permeability and/or high buffering soils.     

我国西南某铀矿水冶尾矿库的退役治理

介绍了我国西南某铀矿尾矿库的污染状况和治理措施,重点介绍了降低氡的析出覆盖层的组成和处理酸性渗出水的渗透反应墙（permeable reactive barriers）技术以及施工。治理后,²²²Rn析出率平均值降为0.68 Bq/(m2·s),γ环境辐射剂量率降低到（28~176）×10^-8 Gy/h ,渗出水pH值为8.3,金属铀浓度0.03mg/L,SO^2-₄为180mg/L,并对存在问题进行分析与讨论。     

美国放射性污染场址整治中土壤的清洁水平

简要介绍了美国污染场址整治中确定土壤清洁水平的开发过程,给出了某些场址的清洁水平,并对其进行了比较.由于多种因素影响,不同场址的清洁水平是不同的,即使是同一场址,不同评价方法导出的清洁水平也不同.因此,一个场址的清洁水平不能简单地用于其它场址.