暴雨型湿地孔隙水中铁锰的时空变化特征

为了进一步探究湿地的净化机制和生物地球化学循环过程,2004～2006年通过连续3 a对武汉动物园暴雨型人工湿地进行原位定期监测,主要研究了湿地孔隙水中铁锰的时空分布特征及其对氧化还原电位(oxidation reduction potential,ORP)的影响.结果表明,暴雨型湿地水位出现周期性的波动,水位的变化范...     

铁氧化菌特性及其在环境污染治理中的应用

铁氧化细菌属于化能无机营养型,常见的有嘉氏铁细菌属,氧化亚铁硫杆菌。氧化亚铁以及各种还原性硫化物为铁氧化菌提供生命活动能量。其主要碳源是二氧化碳,氮源为NH4+。由于氧化亚铁硫杆菌在矿物的附着选择在硫化物相,这些点位的化学键弱,能量易被细菌利用,根据文献发现铁氧化菌的作用机理为直接和间接机理的复合作用。一般来说在水土环境中主要受pH,温度等的影响。目前主要用于城市用水净化、含有重金属离子的各种废水处理及脱硫中,并且已经取得良好的处理效果。     

微生物异化Fe(Ⅲ)还原及其作用机制研究

微生物异化Fe(Ⅲ)还原是一个重要的生物及地球化学过程.文章围绕异化Fe(Ⅲ)还原细菌系统介绍了其代谢机理,对微生物异化Fe(Ⅲ)还原在地球化学中元素迁移和有机污染治理等环境修复方面的作用进行评述和展望.     

Stabilization of Fe0 nanoparticles with silica fume for enhanced transport and remediation of hexavalent chromium in water and soil

Effective in situ remediation of Cr(VI) in groundwater requires the successful delivery of reactive iron particles to the subsurface. Fe0 nanoparticles (20–110 nm diameter) supported on silica fume were synthesized by borohydride reduction of an aqueous iron salt in the presence of a support material. The experimental result showed that attachment of Fe0 nanoparticles on the commercial available sub-micrometer silica fume prevented them from aggregation while maintaining the particle reactivity. When the Fe0 concentration was 0.4 g/L, 88.00% of 40 mg/L Cr(VI) was removed by silica fume-supported Fe0 nanoparticles (SF-Fe0) in 120 min, 22.55% higher than unsupported Fe0. Furthermore, transport experiments confirmed that almost all unsupported Fe0 was retained, whereas 51.50% and 38.29% of SF-Fe0 were eluted from the vertical and horizontal sand column, respectively. Additionally, the effect of solution ionic strength on the transport ability of SF-Fe0 was evaluated. The result showed that increase in the salt concentration led to a decrease in the mobility and also the divalent ion Ca2+ had a greater effect than that of monovalent ion Na+.     

Reduction behaviors of permanganate by microbial cells and concomitant accumulation of divalent cations of Mg2+, Zn2+, and Co2+

Permanganate treatment is widely used for disinfection of bacteria in surface-contaminated water. In this paper, the fate of the dissolved permanganate in aqueous solution after contact with cells of Pseudomonas fluorescens was studied. Concomitant accumulation of divalent cations of Mg~(2+), Zn~(2+), and Co~(2+) during precipitation of Mn oxides was also studied. The time course of the Mn concentration in solution showed an abrupt decrease after contact of Mn(VII) with microbial cells, followed by an increase after ～ 24 hr.XRD analysis of the precipitated Mn oxides, called biomass Mn oxides, showed the formation of low-crystalline birnessite. Visible spectroscopy and X-ray absorption near edge structure(XANES) analyses indicated that dissolved Mn(VII) was reduced to form biomass Mn oxides involving Mn(IV) and Mn(III), followed by reduction to soluble Mn(II).The numbers of electron transferred from microbial cells to permanganate and to biomass Mn oxides for 24 hr after the contact indicated that the numbers of electron transfer from microbial cell was approximately 50 times higher to dissolved permanganate than to the biomass Mn oxides in present experimental conditions. The 24 hr accumulation of divalent cations during formation of biomass Mn oxides was in the order of Co~(2+) Zn~(2+) Mg~(2+).XANES analysis of Co showed that oxidation of Co~(2+) to Co~(3+) resulted in higher accumulation of Co than Zn and Mg. Thus, treatment of surface water by KMnO_4 solution is effective not only for disinfection of microorganisms, but also for the elimination of metal cations from surface water.     

Clay mineralogy affects the efficiency of sewage sludge in reducing lead retention of soils

Recent studies have shown the feasibility of using of sewage sludge for the remediation of heavy metal-contaminated soils. However, there are no researches to check the influence of clay mineralogy on the efficiency of the sewage sludge to remediation of contaminated soils with heavy metals. For this purpose, we use two contrasting soils:Oxisol rich in hematite and gibbsite and Inceptisol rich in kaolinite. Thermal-treated sludge was applied to Pb-contaminated soil samples and incubated for 40 days. The soil samples were submitted to seven sequential extractions: soluble-Pb, exchangeable-Pb,precipitated-Pb, organic matter-Pb, Fe and Mn oxide-Pb, gibbsite and kaolinite-Pb, and residual-Pb. The reduction of soluble Pb forms by thermal sludge application was more pronounced in the Oxisol than in the Inceptisol because of the conversion of soluble-Pb into more stable forms, such as precipitated-Pb and oxides-Pb. For Inceptisol was necessary to apply high rates of thermal sludge to reach a significant reduction in soluble-Pb contents. The addition of humic fractions in the form of thermal sludge increased the concentration of organic matter-Pb. In confined area, the use of sewage sludge to reduce the heavy metals levels in soils must be better considered, mainly in more weathered soils.     

Preparation and characterization of Pd/Fe bimetallic nanoparticles immobilized on Al2O3/PVDF membrane: Parameter optimization and dechlorination of dichloroacetic acid

Using a liquid–solid phase inversion method, a hybrid matrix poly(vinylidene fluoride)(PVDF) membrane was prepared with alumina(Al2O3) nanoparticle addition. Pd/Fe nanoparticles(NPs) were successfully immobilized on the Al2O3/PVDF membrane, which was characterized by Scanning Electron Microscopy(SEM) and Transmission Electron Microscopy(TEM). The micrographs showed that the Pd/Fe NPs were dispersed homogeneously. Several important experimental parameters were optimized, including the mechanical properties, contact angle and surface area of Al2O3/PVDF composite membranes with different Al2O3 contents. At the same time, the ferrous ion concentration and the effect of hydrophilization were studied. The results showed that the modified Al2O3/PVDF membrane functioned well as a support. The Al2O3/PVDF membrane with immobilized Pd/Fe NPs exhibited high efficiency in terms of dichloroacetic acid(DCAA) dechlorination. Additionally, a reaction pathway for DCAA dechlorination by Pd/Fe NPs immobilized on the Al2O3/PVDF membrane system was proposed.     

Pretreatment of cyanided tailings by catalytic ozonation with Mn2+/O3

The increasing amount of cyanided tailings produced as a by-product has gained significant attention in recent years because of the rapid development of the gold industry and extensive exploitation of gold mineral resources. The effective use of these secondary resources is becoming an important and urgent problem for all environmental protection staff. Manganese-catalyzed ozonation for the pre-oxidation of cyanided tailings was studied and the effects of Mn2+dosage, initial sulfuric acid concentration, ozone volume flow, temperature and agitation speed on pretreatment were examined. The optimum reaction conditions were observed to be: ore pulp density 2.5%, agitation speed 700 r/min,temperature 60°C, Mn2+dosage 40 g/L, ozone volume flow 80 L/hr, initial sulfuric acid concentration 1 mol/L, and reaction time 6 hr. Under these conditions, the leaching rate of Fe and weight loss could reach 94.85% and 48.89% respectively. The leaching process of cyanided tailings by Mn2+/O3 was analyzed, and it was found that the leaching of pyrite depends on synergetic oxidation by high-valent manganese and O3, in which the former played an important part.     

Recyclable Fe3O4@Polydopamine (PDA) nanofluids for highly efficient solar evaporation

Volumetric solar evaporations by using light-absorbing nanoparticles suspended in liquids (nanofluids) as solar absorbers have been widely regarded as one of the promising solutions for clean water production because of its high efficiency and low capital cost compared to traditional solar distillation systems. Nevertheless, previous solar evaporation systems usually required highly concentrated solar irradiation and high capital cost, limiting the practical application on a large scale. Herein, for the first time in this work, polydopamine (PDA)-capped nano Fe3O4 (Fe3O4@PDA) nanofluids were used as solar absorbers in a volumetric system for solar evaporation. The introduction of organic PDA to nano Fe3O4 highly contributed to the high light-absorbing capacity of over 85％in wide ranges of 200–2400 nm because of the existence of numerous carbon bonds and pi (π) bonds in PDA. As a result, high evaporation efficiency of 69.93％under low irradiation of 1.0 kW m-2 was achieved. Compared to other nanofluids, Fe3O4@PDA nanofluids also provided an advantage in high unit evaporation rates. Moreover, Fe3O4@PDA nanofluids showed excellent reusability and recyclability owing to the preassembled nano Fe3O4, which significantly reduced the material consumptions. These results demonstrated that the Fe3O4@PDA nanofluids held great promising application in highly efficient solar evapo-ration.