水处理剂高铁酸盐的改性研究

高铁酸盐作为一种优良的水处理剂,由于其有自催化现象、不稳定性、不能长期保存等特点,限制了它的大规模应用.为了寻找稳定高铁酸盐的方法并提高其产品的利用率,采用了饱和水溶液法,以β-环糊精为包合材料,制成了复合高铁酸盐包合物.通过正交试验筛选出最佳包合工艺,得到的复合高铁酸盐在一定时间内能缓慢释放,以达到缓释消毒的条件.并对包合物进行理化鉴别,分析复合高铁酸盐在应用β-环糊精包合前后的成分变化和包合效果.试验结果表明,改性后的复合高铁酸盐具有较高的高铁酸盐溶出浓度与持续时间,具有较好的稳定性.这一结果为高铁酸盐应用于实际水处理提供了依据.     

电解法制备高铁酸盐的研究进展

综述了电解法制备高铁酸盐的研究现状,简要介绍其制备的原理,重点探讨了高铁酸盐制备过程中影响电流效率和高铁酸盐浓度的各种因素,分析总结了提高电解过程电流效率和提高高铁酸盐浓度的方法,为高铁酸盐的工业化应用提供理论依据。未来需要努力的方向,包括电极改进、稳定剂、超声波混合使用以及高铁酸盐制备工艺的优化,在低能耗下获得高浓度的高铁酸盐工业产品。     

高铁酸盐在水处理中的研究进展

高铁酸盐是一种集氧化、絮凝、杀菌多种功能为一体的新型高效多功能水处理剂，高铁酸盐水处理剂兼有较强的氧化性和优良的絮凝功能且在杀菌方面依旧表现优异，且相较于物理吸附法更不易产生二次污染，相较于传统氧化剂，高铁酸盐更为安全，在水处理领域有广阔的应用前景。与使用传统方法合成高铁酸盐相比，本文讨论了高铁酸盐的原位生成方法的优势及其在工业应用方面的价值；对于制约高铁酸盐工业应用发展的稳定性问题，文中分析了影响高铁酸盐稳定存在的温度，pH，溶液中所含有的各种离子浓度等各种因素，综述了提高固态和液态两种形式的高铁酸盐稳定性的方法；最后总结了高铁酸盐在水处理方面的应用进展，对于高铁酸盐工业推广应用中存在的问题进行了探讨。     

高铁酸盐的合成及其性质与应用

综述了高铁酸盐的制备原理、方法、应用以及其今后的发展方向.高铁酸盐作为水处理剂以及电池的阴极材料有着独特的优越性,具有广阔的发展前景.     

高铁酸盐制备方法研究进展

高铁酸盐是一种环境友好的强氧化剂,在水处理、有机合成和超铁电池等方面具有重要的潜在应用价值.综述了近20 a高铁酸盐主要合成方法的研究进展及其特点,包括:熔融法、次氯酸盐氧化法和电化学氧化法,其中电化学氧化法又包括液态高铁酸盐电合成法和固态高铁酸盐直接电合成法.指出:高铁酸钾直接电合成法以其操作简单、原材料消耗少、成本低、可循环生产、工艺绿色环保等优点而成为最有可能工业化应用的合成方法,同时指出了其发展方向.     

流动注射—化学发光法用于高铁酸盐稳定性的研究

基于高铁酸盐可以氧化鲁米诺发光的特性,建立了一种新型、快速、环境友好的在线监测高铁酸盐稳定性的方法———流动注射—化学发光分析法。研究了温度、溶液pH值、添加剂对高铁酸盐稳定性的影响,结果表明,低温和高碱度是保持高铁酸盐溶液稳定的关键因素,硅酸钠作为添加剂有助于提高高铁酸盐的产率和稳定性。     

水处理剂高铁酸钠的制备

本实验在分析各种制备高铁酸盐方法的基础上,采用无机化学次氯酸盐氧化法制备高铁酸钠,并着重分析了各种不同因素Fe（NO3）3·9H2O的用量、碱的用量、原料的添加顺序）对产率的影响,并分析了高铁酸盐在水处理方面的应用。     

排水量气法测定高铁酸盐

为弥补传统测定方法的不足,利用改进的排水量气法建立了高铁酸盐的定量分析方法,探讨了该方法的准确度、精密度、干扰离子影响及体系稳定性。研究表明,高铁酸盐与稀盐酸反应放出O2,通过测定反应生成的氧气体积,可计算高铁酸盐纯度。本测量方法简单快速,准确度和精密度高,稳定性良好,该法对所有高铁酸盐的纯度测定具有普适性,特别适用于定量检测难溶性高铁酸盐。     

高铁酸钾制备和不同添加剂对高铁电池放电性能的影响

高铁酸盐作为电池的阴极具有许多独特的优点.综述高铁酸钾的最新合成方法,并添加钛、NiOOH、Li2CO3等添加剂,对其改善高铁电池的放电性能进行了讨论与分析.实验结果表明这几种添加剂对高铁电池放电效率有很大的提高.     

高铁酸盐在工业废水中的应用

分析了高铁酸盐在工业废水中杀菌除藻、去除无机物及有机物等方面的研究现状;探究了其氧化絮凝特性在反应过程中的作用机理及最佳反应条件;总结了高铁酸盐现阶段的联用新技术。为促进高铁酸盐的发展,就其对环境的毒理性进行了评价。提出了高铁酸盐今后的研究方向,以期为后续实际应用提供参考。     

Advances in electrochemical Fe(VI) synthesis and analysis

Hexavalent iron species (Fe(VI)) have been known for over a century, and have long-time been investigated as the oxidant for water purification, as the catalysts in organic synthesis and more recently as cathodic charge storage materials. Conventional Fe(VI) syntheses include solution phase oxidation (by hyphchlorite) of Fe(III), and the synthesis of less soluble super-irons by dissolution of FeO₄ ²⁻, and precipitation with alternate cations. This paper reviews a new electrochemical Fe(VI) synthesis route including both in situ and ex situ syntheses of Fe(VI) salts. The optimized electrolysis conditions for electrochemical Fe(VI) synthesis are summarized. Direct electrochemical synthesis of Fe(VI) compounds has several advantages of shorter synthesis time, simplicity, reduced costs (no chemical oxidant is required) and providing a possible pathway towards more electro-active and thermal stable Fe(VI) compounds. Fe(VI) analytical methodologies summarized in this paper are a range of electrochemical techniques. Fe(VI) compounds have been explored as energy storage cathode materials in both aqueous and non-aqueous phase in “super-iron” battery configurations. In this paper, electrochemical synthesis of reversible Fe(VI/III) thin film towards a rechargeable super-iron cathode is also summarized.     

Chemical and electrochemical considerations on the removal process of hexavalent chromium from aqueous media

Two methods were used to remove Cr(VI) from industrial wastewater. Although both are based in the same general reaction: 3Fe(II)_(aq) + Cr(VI)_(aq) ; 3Fe(III)_(aq) + Cr(III)_(aq) the way in which the required amount of Fe(II) is added to the wastewater is different for each method. In the chemical method, Fe(II)_(aq) is supplied by dissolving FeSO₄ · 7(H₂O)_(s) into the wastewater, while in the electrochemical process Fe(II)_(aq) ions are formed directly in solution by anodic dissolution of an steel electrode. After this reduction process, the resulting Cr(III)_(aq) and Fe(III)_(aq) ions are precipitated as insoluble hydroxide species, in both cases, changing the pH (i.e., adding Ca(OH)_2(s)). Based on the chemical and thermodynamic characteristics of the systems Cr(VI)–Cr(III)–H₂O–e^– and Fe(III)–Fe(II)–H₂O–e^– both processes were optimized. However we show that the electrochemical option, apart from providing a better form of control, generates significantly less sludge as compared with the chemical process. Furthermore, it is also shown that sludge ageing promotes the formation of soluble polynuclear species of Cr(III). Therefore, it is recommended to separate the chromium and iron-bearing phases once they are formed. We propose the optimum hydraulic conditions for the continuous reduction of Cr(VI) present in the aqueous media treated in a plug-flow reactor.     

X‐ray photoelectron spectroscopy investigation of the interaction of U(VI) and Fe(III) with natural humic acid in aqueous solutions

Complexes of U(VI) and Fe(III) with natural humic acid (NHA) were studied by X‐ray photoelectron spectroscopy (XPS). It follows from the analysis of the uranium and iron concentrations at the surface and in the bulk of the humates that the reaction in solution is heterogeneous. The NHA reacts as a particle. In solutions containing either U(VI) or Fe(III), NHA reacts similar with Fe(III) and U(VI). However, in a mixed solution of Fe(III) and U(VI), NHA reacts predominantly with iron. In comparison to Fe(III) complexes, the complexes with U(VI) are formed mostly in the inner of the NHA particle. Therefore, the concentration ratio U/Fe as measured by XPS increases by powdering of the particles. Salts of Fe(III) can be used to inhibit the uranium migration in form of its soluble humates.     

Oxidation of caffeine by acid‐activated ferrate(VI): Effect of ions and natural organic matter

Caffeine (CAF) is the most commonly consumed stimulant and frequently detected emerging pollutant in influents and effluents of wastewater treatment plants (WWTP) and surface waters. Acid‐activated ferrate(VI) (Fe^VI , Fe(VI)) oxidizes CAF in water in seconds to minutes at three times lower molar ratio of Fe(VI) to CAF than oxidative transformation observed in hours by nonactivated Fe(VI) (8.0 vs. 25.0). CAF oxidation by acid‐activated Fe(VI) is not affected by ionic constituents of water. Organic components of natural organic matter (NOM) and secondary effluent wastewater (SE) decrease efficiency of CAF transformation. However, acid‐activated Fe(VI) could mineralize other organics present in both NOM and SE as indicated by the dissolved organic carbon (DOC) removal. Comparatively, no mineralization was seen without activation of Fe(VI). Four oxidized products of CAF were identified by a liquid chromatography high resolution mass spectrometry technique. The reaction pathways of the oxidation of CAF by activated Fe(VI) have been proposed. © 2017 American Institute of Chemical Engineers AIChE J, 2017     

Kinetics and mechanism of methylene blue removal by electrosynthesized ferrate(VI)

The oxidation of methylene blue (MB) by electrosynthesized ferrate(VI) in a semi-batch reactor is investigated. The effects of pH, Fe(VI) dose and initial MB concentration on the efficiency of the degradation process were studied. The original pH of MB solution was found more effective on the degradation and colour removal as 96.82% MB removal and 40.36% colour removal were gained. Initial MB solution and Fe(VI) dose affected the removal efficiencies. Degradation of MB by Fe(VI) was the second-order reaction kinetics. The density functional theory (DFT) analysis confirmed that density is intended mostly on the phenyl rings and least of all on the bonding orbitals of the middle heterocycle of МВ.     

Photo-enhancement of Cr(VI) reduction by fungal biomass of Neurospora crassa

Various organisms such as fungus are capable of reducing Cr(VI) to less toxic Cr(III). However, light-induced Cr(VI) reduction by fungus is less reported and needs to be explored since anthropogenic or natural activities may bring these two reactants into a sunlit environment. In this study, the interactions and reaction mechanisms of Cr(VI) on a model fungus, Neurospora crassa, were evaluated in the presence or absence of light. The influence of ferric ion, a widely distributed metal, on Cr(VI) reduction by the fungus was also investigated under illumination. The results show that 20–54% of added Cr(VI) (96.2 μM) was removed by 1 g of dead fungal biomass (i.e., 1–2.7 mg Cr(VI) reduction by 1 g biomass) at pH 1–3, after 6 h reaction in the dark. However, 96.2 μM Cr(VI) disappeared completely (i.e., 5 mg Cr(VI) reduction by 1 g biomass) under the same reaction time and experimental conditions when light was present. The rapid disappearance of Cr(VI) in solution was due to the reduction of Cr(VI) by the excited biomass upon light absorption, and the rates of redox reactions increased with a decrease at pH. Cr(VI) reduction could be further increased with the addition of 89.5 μM Fe(III) because the formation of Fe(II) from the photolysis of Fe–organic complexes enhanced Cr(VI) reduction. Spectroscopic studies indicated that the amide, NH, and carboxyl groups of N. c.-biomass may be responsible for initiating Cr(VI) reduction; comparatively, the cyclo-carbons of chitin, glucan, and their derivatives were more persistent to the oxidation by Cr(VI). Accordingly, fungi containing high amount of carboxyl, amide, and NH groups may be preferable as efficient reductants for scavenging Cr(VI) from environment. Upon the absorption of a renewable light source, Cr(VI) could be converted rapidly by the biomaterials to the less toxic Cr(III).     

Heterogeneous photocatalytic reduction of Fe(VI) in UV-irradiated titania suspensions: effect of ammonia

Results of the heterogeneous photocatalytic reduction of Fe(VI) in UV-irradiated TiO₂ suspensions in the presence of ammonia are presented. The initial rate of Fe(VI) reduction, R, may be expressed as R = k _Fe(VI)[Fe(VI)]^1.25 where k _Fe(VI) = a[Ammonia]+b), a = 6.0 × 10³ μm ^0.25 s and b = 4.1 × 10⁶ μm ^−1.25s⁻¹. The rate constant, k _Fe(VI), increases with the ammonia concentration. The photocatalytic oxidation of ammonia is enhanced in the presence of Fe(VI). A mechanism involving Fe(V) as a reactive intermediate is presented which explains the faster photocatalytic oxidation of ammonia in the presence of Fe(VI).     

Dual sorption of metal-ions on a crosslinked resin of 2-acrylamidoglycolic acid and 4-vinylpyridine

Summary A resin containing 4-vinylpyridine and 2-acrylamidoglycolic acid was synthesized by radical polymerization with subsequent crosslinking by N,N-methylene-bis-acrylamide. The resin was characterized by elemental analyses and FT-IR spectroscopy. The ability of this resin as well as both crosslinked homopolymers to bind Cu(II), Fe(II), Fe(III) and U(VI) was studied at different pHs depending on the metal ion. From pH=2 U(VI) was sorbed above 96% from an aqueous solution of 1.0 g/L. A dual sorption mechanism to U(VI) depending on the pH is suggested. The elution of the metal ions from the loaded resins was assayed with H₂SO₄ and Na₂CO₃.     

铬污染地下水的PRB修复试验

以铬污染地下水为研究对象,分别用活性炭、零价铁、活性炭+零价铁作为反应介质,设计了渗透反应隔栅(PRB),对PRB治理六价铬污染地下水的可行性和有效性进行了试验研究,试验结果表明,活性炭对Cr(VI)有一定的吸附作用,零价铁对Cr(VI)有较强的还原作用,零价铁与活性炭配合作用时,二者的配比影响Cr(VI)的去除,零价铁所占质量分数越大,去除效果越好。零价铁、活性炭和石英砂质量分数分别为40%,4%和2%时,可以使Cr(VI)的质量浓度从100mg/L降低到0.05mg/L以下,达到《饮用净水水质标准》。采用PRB技术治理Cr(VI)污染地下水是可行的。     

黄腐酸和湖泊孔隙水对Fe(Ⅱ)还原Cr(Ⅵ)为Cr(Ⅲ)的影响

考查了缺氧条件下Fe(Ⅱ)-有机质(DOM)的络合物将Cr(Ⅵ)还原为Cr(Ⅲ)的还原能力。研究发现在没有或有萨旺尼河黄腐酸(SRFA)和波尼湖黄腐酸(PLFA)存在的情况下,Fe(Ⅱ)都能够将Cr(Ⅵ)快速地还原(几分钟)。Fe(Ⅱ)-DOM溶液不一定比仅含有Fe(Ⅱ)单一的体系具有更强的还原力。DOM的组成也影响了Cr(Ⅲ)的还原机制,湿地(俄亥俄州老妇人河河口区)沉积物进行缺氧萃取得到的沉积物孔隙水能够将Cr(Ⅵ)更快地还原。这些研究数据表明自然界中富含Fe(Ⅱ)和DOM的缺氧孔隙水对Cr(Ⅵ)的非生物还原反应速率远大于生物还原反应速率,并且这一非生物还原反应是自然环境中Cr(Ⅵ)被还原的主要途径。