Distinct roles of pH and organic ligands in the dissolution of goethite by cysteine

Electron shuttles such cysteine play an important role in Fe cycle and its availability in soils,while the roles of pH and organic ligands in this process are poorly understood.Herein,the reductive dissolution process of goethite by cysteine were explored in the presence of organic ligands.Our results showed that cysteine exhibited a strong reactivity towards goethite-a typical iron minerals in paddy soils with a rate constant ranging from 0.01 to0.1 hr-1.However,a large portion of Fe(Ⅱ) appeare...     

基于情景分析的钢铁工业物质流与价值流协调性研究

本文基于情景分析理论和方法,建立了钢铁工业物质流与价值流协调度模型,对未来一段时期钢铁工业的协调发展状况进行研究.在维持现有发展模式的基准情景下,我国钢铁工业协调发展度将持续下降,2020年将下降到0.73.在环境恶化和经济效益相对脱钩的情景下,直到2020年我国钢铁工业协调发展度将维持在0.85的水平.而在经济与环境出现绝对脱钩的情景下,我国钢铁工业协调发展度将持续上升,2020年将达到0.95的高水平.因此,近期我国钢铁工业应遵循“基准相对脱钩绝对脱钩”的发展路径,降低总物质投入和污染物排放总量,提升经济产出效益,可持续发展才有可能实现.     

生物过滤法对水中铁去除的试验研究

随着生物技术在水处理工业中的推广应用,人们逐渐认识到生物除铁是将来替代接触氧化法除铁的新一代除铁方法。本文在国内外生物除铁研究的基础上,通过较低pH值条件培养铁细菌,最终检测不同实验条件下的过滤效果,以达到研究不同粒径滤料、pH值、溶解氧等条件对生物除铁的影响。实验结果表明：小粒径滤料有利于过滤过程的进行;生物除铁的效果不明显,尤其在高pH值和溶解氧条件下几乎没有差别;随着pH值和溶解氧浓度的增加,亚铁的氧化效果加强了,但是生物除铁的效果却减弱了。     

A barrier to metal movement: Synchrotron study of iron plaque on roots of wetland plants

正A wetland with attractive plants hosting birds and other wildlife is an esthetically pleasing prospect that is gaining popularity as a way of stabilizing or remediating metalcontaminated soils and sediment(Weber and Gagnon,2014;     

某钢铁企业厂区与附近城区空气质量现状对比与防治对策

对2020年10月份某钢铁企业厂区和附近城区环境空气质量自动监测站的数据进行了收集整理,对比分析正常时段厂区和附近城区的空气质量指数(AQI)与SO₂、PM₁₀等6个空气质量分指数(IAQI)的差异性和相关性。结果表明:在分析收集数据范围内,附近城区环境空气质量优良率高于某钢铁公司厂区7.1%,附近城区的首要主要污染物为NO₂和PM_2.5,而某钢铁公司厂区的主要污染物为PM₁₀、PM_2.5和O₃,说明某钢铁公司污染物排放对附近城区的空气质量不存在高度的线性关系。根据研究结果,提出源头调整产业结构、强化过程控制和实施末端全面超低排放对策建议。     

The control of red water occurrence and opportunistic pathogens risks in drinking water distribution systems: A review

Many problems in drinking water distribution systems (DWDSs) are caused by microbe, such as biofilm formation, biocorrosion and opportunistic pathogens growth. More iron release from corrosion scales may induce red water. Biofilm played great roles on the corrosion. The iron-oxidizing bacteria (IOB) promoted corrosion. However, when iron-reducing bacteria (IRB) and nitrate-reducing bacteria (NRB) became the main bacteria in biofilm, they could induce iron redox cycling in corrosion process. This process enhanced the precipitation of iron oxides and formation of more Fe₃O₄ in corrosion scales, which inhibited corrosion effectively. Therefore, the IRB and NRB in the biofilm can reduce iron release and red water occurrence. Moreover, there are many opportunistic pathogens in biofilm of DWDSs. The opportunistic pathogens growth in DWDSs related to the bacterial community changes due to the effects of micropollutants. Micropollutants increased the number of bacteria with antibiotic resistance genes (ARGs). Furthermore, extracellular polymeric substances (EPS) production was increased by the antibiotic resistant bacteria, leading to greater bacterial aggregation and adsorption, increasing the chlorine-resistance capability, which was responsible for the enhancement of the particle-associated opportunistic pathogens in DWDSs. Moreover, O₃-biological activated carbon filtration-UV-Cl₂ treatment could be used to control the iron release, red water occurrence and opportunistic pathogens growth in DWDSs.     

Photocatalytic degradation of phenol by visible light-responsive iron-doped TiO2 and spontaneous sedimentation of the TiO2 particles

Fe-doped TiO₂ was prepared by the calcination of Fe_xTiS₂ (x = 0, 0.002, 0.005, 0.008, 0.01) and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV–visible diffuse reflectance spectra. All the Fe-doped TiO₂ were composed of an anatase crystal form and showed red shifts to a longer wavelength. The activity of the Fe-doped TiO₂ for the degradation of phenol was investigated by varying the iron content during UV (365 nm) and visible light (405 nm and 436 nm) irradiation. The degradation rate depended on the Fe content and the Fe-doped TiO₂ was responsive to the visible light as well as the elevated activity toward UV light. The molar ratio of 0.005 was the optimum for both the UV and visible light irradiations. The result was discussed on the basis of the balance of the excited electron–hole trap by the doped Fe³⁺ and their charge recombination on the doped Fe³⁺ level. The Fe-doped TiO₂ (x = 0.005) was more active than P25 TiO₂ under solar light irradiation. The suspended Fe-doped TiO₂ spontaneously precipitated once the stirring of the reaction mixture was terminated.     

Investigation of gas production and entrapment in granular iron medium

A method for measuring gas entrapment in granular iron (Fe0) was developed and used to estimate the impact of gas production on porosity loss during the treatment of a high NO3- groundwater (up to approximately 10 mM). Over the 400-d study period the trapped gas in laboratory columns was small, with a maximum measured at 1.3% pore volume. Low levels of dissolved H2(g) were measured (up to 0.07+/-0.02 M). Free moving gas bubbles were not observed. Thus, porosity loss, which was determined by tracer tests to be 25-30%, is not accounted for by residual gas trapped in the iron. The removal of aqueous species (i.e., NO3-, Ca, and carbonate alkalinity) indicates that mineral precipitation contributed more significantly to porosity loss than did the trapped gases. Using the stoichiometric reactions between Fe0 and NO3-, an average corrosion rate of 1.7 mmol kg-1 d-1 was derived for the test granular iron. This rate is 10 times greater than Fe0 oxidation by H2O alone, based on H2 gas production. NO3- ion rather than H2O was the major oxidant in the groundwater in the absence of molecular O2. The N-mass balance [e.g., N2g and NH4+ and NO3-] suggests that abiotic reduction of NO3- dominated at the start of Fe0 treatment, whereas N2 production became more important once the microbial activity began. These laboratory results closely predict N2 gas production in a separated large column experiment that was operated for approximately 2 yr in the field, where a maximum of approximately 600 ml d-1 gas volumes was detected, of which 99.5% (v/v) was N2. We conclude that NO3- suppressed the production of H2(g) by competing with water for Fe0 oxidation, especially at the beginning of water treatment when Fe0 is highly reactive. Depends on the groundwater composition, gas venting may be necessary in maintaining PRB performance in the field.     

Effects of dissolved oxygen and iron aging on the reduction of trichloronitromethane, trichloracetonitrile, and trichloropropanone

Iron metal (Fe(0)) is a potent reductant capable of reducing a wide variety of halogenated organic compounds including disinfection byproducts (DBPs). These reduction reactions may play a role in DBP fate in iron water mains and potentially could be exploited to remove DBPs from drinking water or wastewater in a packed-bed configuration. Oxidants (i.e., dissolved oxygen (DO) and chlorine) present in the water, however, may decrease the DBP degradation rate by competing for reactive sites and rapidly aging or corroding the iron surface. Thus, batch experiments were performed to investigate the effect of DO on the degradation rates of selected DBPs by Fe(0). Experiments were performed under anaerobic conditions, in initially oxygen saturated buffer without DO control, and under controlled DO (approximately 4.0 or 8.0 mg l⁻¹) conditions. The effect of short-term (25–105 min) iron aging in DO-containing buffer on DBP degradation rate also was investigated in separate experiments. For fresh Fe(0), the degradation rates of trichloronitromethane (TCNM) and trichloroacetonitrile (TCAN) in initially oxygen saturated buffer were similar to their respective rates under anaerobic conditions. The degradation rate of 1,1,1-trichloropropanone (1,1,1-TCP), however, decreased significantly in the presence of DO and the effect was proportional to DO concentration in the controlled DO experiments. For a DO concentration of 4 mg l⁻¹, the degradation rate of the three DBPs was greater for longer aging times as compared to their respective rates after 25 min, suggesting the formation of a mineral phase that increased reactivity. For a DO concentration of 8 mg l⁻¹, the effects of increasing aging time were mixed. TCNM degradation rates were stable for all aging times and comparable to that under anaerobic conditions. The TCAN and 1,1,1-TCP degradation rates, however, tended to decrease with increasing aging time. These results suggest that the reduction of highly reactive DBPs by Fe(0) will not be affected by the presence of DO but that the reaction rates will be slowed by DO for DBPs with slower degradation kinetics.     

铁和铝离子对土壤水溶性氟化物检测的干扰研究

通过离子选择电极法测定Fe3+和Al3+不同含量的土壤样品中水溶性氟化物试验,研究Fe3+和Al3+对测定的干扰与消除方法,证实了在总离子强度调节缓冲溶液共存下,Fe3+和Al3+对土壤提取液中水溶性氟化物检测结果存在不同程度的负干扰。选择6种代表性土壤样品,在水溶性氟化物提取液中加入20 mg/L的Al3+和100 mg/L的Fe3+做干扰试验,比较了分取不同体积土壤提取液对氟化物检测结果的影响,结果表明,对水溶性ρ(Fe3+)和ρ(Al3+)高的土壤样品,可选择减少提取液取样体积来消除干扰。选取的5种标准样品测试结果与标准值相符,干扰消除方法具有良好的适用性。