Simultaneous removal of Cr(Ⅵ), Cd, and Pb from aqueous solution by iron sulfide nanoparticles: Influencing factors and interactions of metals

Cadmium(Cd),lead(Pb),and hexavalent chromium(Cr(Ⅵ)) are often found in soils and water affected by metal smelting,chemical manufacturing,and electroplating.In this study,synthetic iron sulfide nanoparticles(FeS NPs) were stabilized with carboxymethyl cellulose(CMC) and utilized to remove Cr(Ⅵ),Cd,and Pb from an aqueous solution.Batch experiments,a Visual MINTEQ model,scanning electron microscopy(SEM),X-ray diffraction(XRD),and X-ray photoelectron spectrometer(XPS) analysis were used to determine the removal efficiencies,influencing factors,and mechanisms.The FeS NP suspension simultaneously removed Cr(Ⅵ),Cd,and Pb from an aqueous solution.The concentrations of Cr(Ⅵ),Cd,and Pb decreased from 50,10,and 50 mg·L^(-1) to 2.5,0.1,and 0.1 mg·L^(-1),respectively.The removal capacities were up to 418,96,and 585 mg per gram of stabilized FeS NPs,respectively.The acidic conditions significantly favored the removal of aqueous Cr(Ⅵ) while the alkaline conditions favored the removal of Cd and Pb.Oxygen slightly inhibited the removal of Cr(Ⅵ),but it had no significant influence on the removal of Cd and Pb.A potential mechanism was proposed for the simultaneous removal of Cr(Ⅵ),Cd,and Pb using FeS NPs.The interactions of the three heavy metals involved a cationic bridging effect on Cr(Ⅵ) by Cd,an enhanced adsorption effect on Cd by [Cr,Fe](OH)_3,precipitation of PbCrO_4,and transformation of PbCrO_4 to PbS.Therefore,FeS NPs have a high potential for use in the simultaneous removal of Cr(Ⅵ),Cd,and Pb from contaminated aqueous solutions.

Simultaneous Determination of Iron and Manganese in Water Using Artificial Neural Network Catalytic Spectrophotometric Method

A new analytical method using Back-Propagation (BP) artificial neural network and kinetic spectrophotometry for simultaneous determination of iron and magnesium in tap water, the Yellow River water and seawater is established. By conditional experiments, the optimum analytical conditions and parameters are obtained. Levenberg-Marquart (L-M) algorithm is used for calculation in BP neural network. The topological structure of three-layer BP ANN network architecture is chosen as 15-16-2 (nodes). The initial value of gradient coefficient μ is fixed at 0.001 and the increase factor and reduction factor of μ take the default values of the system. The data are processed by computers with our own programs written in MATLAB 7.0. The relative standard deviation of the calculated results for iron and manganese is 2.30% and 2.67% respectively. The results of standard addition method show that for the tap water, the recoveries of iron and manganese are in the ranges of 98.0%-104.3% and 96.5%-104.5%, and the RSD is in the range of 0.23%-0.98%; for the Yellow River water (Lijin district of Shandong Province), the recoveries of iron and manganese are in the ranges of 96.0%-101.0% and 98.7%-104.2%, and the RSD is in the range of 0.13%-2.52%; for the seawater in Qingdao offshore, the recoveries of iron and manganese are in the ranges of 95.3%-104.8% and 95.3%-104.7%, and the RSD is in the range of 0.14%-2.66%. It is found that 21 common cations and anions do not interfere with the determination of iron and manganese under the optimum experimental conditions. This method exhibits good reproducibility and high accuracy in the determination of iron and manganese and can be used for the simultaneous determination of iron and manganese in tap water and natural water. By using the established ANN- catalytic spectrophotometric method, the iron and manganese concentrations of the surface seawater at 11 sites in Qingdao offshore are determined and the level distribution maps of iron and manganese are drawn.

Science Letters:Simultaneous removal of nitrate and heavy metals by iron metal

Great attention should be paid now to simultaneously removing common pollutants, especially inorganic pollutants such as nitrate and heavy metals, as individual removal has been investigated extensively. Removing common pollutants simul- taneously by iron metal is a very effective alternative method. Near neutral pH, heavy metals, such as copper and nickel, can be removed rapidly by iron metal, while nitrate removal very much slower than that of copper and nickel, and copper can accelerate nitrate removal when both are removed simultaneously. Even a little amount of copper can enhance nitrate removal efficiently. Different mechanisms of these contaminants removal by iron metal were also discussed.

Efficiency and Mechanism of Phosphorus Removal by Coagulation of Iron-manganese Composited Oxide

Iron-manganese composited oxide（FeMnO） was prepared with potassium permanganate and ferrous salt. Interface performance, charge property and structure topography of the FeMnO were investigated. Coagulation efficiency and pollution removal mechanism of the FeMnO were approached. Results show that the main compositions of the FeMnO are δ-manganese dioxide and ferric hydroxide. The specific surface area is about 146.22 m^2/g. The FeMnO contains rich hydroxyl with extremely strong adsorption action and chemical adsorption activity. The zero charge point of the oxide in pure water is about 8.0 of pH value. Under neutral pH value conditions, the FeMnO particle surface carried positive charges. The FeMnO particles are quasi-spherical micro-particles with irregular sizes adjoined each other to form net construction. Phosphorus removal efficiency of the FeMnO is remarkable, the total dissoluble phosphorus of settled water can be reduced below detecting level（0.3 μtg/L） at a FeMnO dosage of 6 mg/L, and total phosphorus below detecting level at a FeMnO dosage of 10 mg/L, for water samples containing total phos- phorus of 1281.70 μg/L and total dissoluble phosphorus of 1187.91 μtg/L. The mechanism of effective coagulation for phosphorus removal is combined results of multiple actions of adsorption, charge neutralization, adsorption/bridging and so on.

Study on the Removal of Iron,Manganese and Nitrate in Groundwater by Biological Ribbon Technology

The pollution of iron,manganese and nitrate in groundwater is a huge threat to human beings.In this study,column experiments of ceramic,manganese sand,ceramic sand,volcanic rock,quartz sand were conducted.Iron and manganese contents of influent were 3.3 mg/L and 2.1 mg/L.When the biofilm became mature,the highest iron and manganese removal rate achieved by manganese sand as a filter material.Quartz did a little worse than manganese sand,but other three filter material could not reach

The Application of Biological Removal Technology Used on the Treatment of Groundwater with Low-Iron and High-Manganese

The characteristic of groundwater belongs to low iron but high manganese in Shenyang Hunnan New Developed Area.The first stage engineering of The WTP of Shenyang Hunnan industry Area were designed according the technology of aerated-contact oxidation,and the water quality couldn’t reach to the standard after the WTP putted into production,1996.

Removing Iron and Manganese Simultaneously from Ground Water Using One-stage Biological Filter

A novel process for removing iron and manganese simultaneously in ground water,which consisted of simple aeration and one-stage filtration,was developed in this research. It was found that the biological process had much higher manganese removal efficiency than chemical contact oxidation process. At the same time,the optimal operation parameters of aeration and biological filtration such as DO concentration and pH after aeration,filtration rate before and after startup,filtration operation cycle and backwashing rate,etc.,were also obtained by experiments. By analyzing water quality in different positions of filter bed,it was found that the oxidation of Fe2+ in biological filter bed adapted to first-order reaction,whereas the oxidation of Mn2+ conformed to zero-order reaction,which could be explained by Michaelis-Menten enzyme reaction equation when substrate concentration was far more than bacteria amount.

Thermodynamic analysis of Na−S−Fe−H_(2)O system for Bayer process

Thermodynamic diagrams of Na−S−Fe−H_(2)O system were constructed to analyze the behavior of sulfur and iron in the Bayer process.After digestion,iron mainly exists as Fe_(3)O_(4) and Fe_(2)O_(3) in red mud,and partial iron transfers into solution as Fe(OH)_(3)^(−),HFeO_(2)^(−),Fe(OH)_(4)^(−)and Fe(OH)_(4)^(2−).The dominant species of sulfur is S^(2−),followed by SO_(4)^(2−),and then SO_(3)^(2−)and S_(2)O_(3)^(2−).The thermodynamic analysis is consistent with the iron and sulfur species distribution in the solution obtained by experiments.When the temperature decreases,sulfur and iron can combine and precipitate.Controlling low potential and reducing temperature are beneficial to removing them from the solution.XRD patterns show that NaFeS_(2)·2H_(2)O,FeS and FeS_(2) widely appear in red mud and precipitates of pyrite and high-sulfur bauxite digestion solution.Thermodynamic analysis can be utilized to guide the simultaneous removal of sulfur and iron in the Bayer process.

改性沸石去除地下水中铁锰的研究进展

根据沸石的结构特征并利用沸石进行除铁锰的动力学机理总结了影响其除铁锰性能的材料自身的因素,综述了对沸石进行改性的方法以及改性前后的对比,其中包括在合成过程中在保证沸石基本框架的前提下,对影响沸石合成的因素,即硅铝比、杂质去除、碱度、结晶温度、晶化时间、导向剂的人为控制调节,以及进行微波、高温、涂层、化学药剂浸泡的预处理改性。为改性沸石后续研究提出参考和建议。

接触氧化除铁除锰工艺中微生物的协同作用

以辽宁农村地区二个典型接触氧化除铁除锰水厂为研究对象,采用16S rRNA高通量测序技术对工艺各单元的微生物群落结构进行分析.结果发现,接触氧化除铁除锰工艺各处理单元中的微生物群落结构显著不同,Proteobacteria(43.86%)是接触氧化除铁除锰工艺中的优势菌门,Gallionella和Flavobacterium是主要的除铁锰功能菌属.相关性分析结果表明,Rhodoferax(0.71%)和Sulfurospirillum(0.75%)等菌属与菌落总数,铁和锰浓度之间呈显著正相关关系,说明尽管其相对丰度较低,但仍在系统中发挥着不可或缺的作用.通过分子生态网络与拓扑特性的深入分析以及COGs功能预测,揭示了Gallionella,Flavobacterium,Pseudomonas和Rhodoferax等菌属间的协同作用关系.不同处理单元对微生物群落结构产生了显著影响,但对这些微生物的代谢影响较小,表明形成的微生物共存系统相对稳定,对水中铁锰离子的高效稳定去除有着重要作用.

锰改性人工矿质纤维载体同时硝化反硝化性能研究

填料的性能对于生物膜工艺脱氮除磷效果起着关键作用。通过MnO_(2)浸渍、MnCl_(2)氧化还原、MnO_(2)甲醇扩散和KMnO4氧化还原四种方法改性人工矿质纤维(ARW),并利用扫描电镜(SEM)和能量色散光谱(EDS)对改性前后的ARW进行形貌和元素分析。再通过实验研究改性前后的ARW在DO质量浓度为0.5 mg/L的环境中微生物群落及脱氮除磷效果。结果表明:1)改性后的ARW上成功负载了锰氧化物;2)负载锰氧化物的ARW系统脱氮除磷效果均优于原始ARW系统,其中MnO_(2)甲醇扩散改性ARW系统的脱氮除磷效果最佳,其稳定后对COD、NH_(4)^(+)-N、NO_(3)^(-)-N和TN的去除率相较于原始ARW系统分别提高了7.51%、17.02%、2.15%和11.19%;3)微生物的纲水平分析显示,MnO_(2)甲醇扩散改性ARW系统中γ-变形菌纲和α-变形菌纲分别占33.32%和13.07%,为原始ARW系统的1.18倍和1.19倍,其为水处理中脱氮除磷的优势菌纲。研究表明锰改性ARW可作为优良的水处理填料。

铁锰复合材料吸附工业废水中铊的机理研究

铊(Thallium,Tl)是一种高毒性金属,其致死剂量仅为10—15 mg·kg^(-1)。由于锰氧化物具有优良的吸附性,因此在铊污染防治中展现出很好的应用前景。然而,锰氧化物在吸附铊的过程中会溶出锰,因而对环境造成二次污染。为解决该问题,引入铁元素制备铁锰复合材料,降低吸附过程中锰的溶出。结果表明:铁元素的引入能大幅地减少吸附过程中锰的溶出,当初始Tl0浓度为10 mg·L^(-1)时,1 mg·L^(-1)的铁锰复合材料对铊的去除率超过99%,同时锰的溶出浓度控制在国家排放标准以内(0.3 mg·L^(-1)),达到了0.11mg·L^(-1);等温吸附曲线表明,当吸附温度为308 K时,铁锰复合材料的吸附符合Freundlich吸附曲线(R^(2)=0.94),吸附最大容量为539.4 mg·g^(-1)。说明,铁锰复合材料在有效降低锰溶出的同时,也能够高效地去除铊。

黄铁矿与空气组合强化去除锰浸出液中铁离子

研究了黄铁矿和空气组合去除锰浸出液中铁离子的过程及机理。结果表明:在溶液pH值2.5、反应温度25℃、黄铁矿用量15 g/L、空气用量2.4 L/min和反应时间1 h条件下,除铁后浸出液中残余铁离子质量浓度小于0.01 g/L,锰回收率高于99%。黄铁矿作为还原物质与充入溶液的空气共同作用,使黄铁矿周围存在Fe^(3+)/Fe^(2+)与氧气共存的活性反应区域,有助于溶液中铁离子以针铁矿沉淀形式被去除。

铁屑/竹纤维质量比对竹基耦合体系氮磷同步去除效能的影响

利用铁屑与竹纤维构建竹基耦合体系强化低碳氮比(C/N)废水中氮磷同步去除。采用连续流装置,搭建5组具有不同铁屑/竹纤维质量比(Fe/B)的耦合体系,探究Fe/B对氮磷去除效能的影响。耦合体系在进水平均总氮(TN)为31.32 mg/L,平均C/N为1.16,平均总磷(TP)为2.02 mg/L下连续运行113 d,水力停留时间(HRT)从16 h降至8 h,结果显示Fe/B≤0.500时,耦合体系氮磷去除效果与Fe/B呈正相关;当Fe/B为0.500时,氮磷去除最高,出水TN、TP可达《地表水环境质量标准》(GB 3838—2002)的Ⅳ类标准;Fe/B>0.500时,氮磷去除略有降低;耦合体系出水总铁整体较低,当Fe/B为0.250时,出水总铁波动最大;Fe/B≤0.500时,铁屑可显著促进脱氮除磷功能菌的生长,包括反硝化除磷菌,当Fe/B>0.500时,脱氮除磷功能菌群相对丰度明显降低,菌群结构亦发生显著变化。

电解金属锰制液过程中的氧化锰除铁工艺优化

电解金属锰制液工艺中,常利用氧化锰粉将Fe^(2+)氧化成Fe^(3+),以便在后续中和过程中形成氢氧化铁胶体,实现铁的去除。针对低品位氧化锰粉在生产过程中存在除铁利用率低的问题,开展了氧化锰粉除铁工艺优化研究,结果表明:当除铁锰粉粒径≤125μm,初始酸的质量浓度为6.5 g/L,反应温度为60℃,反应时间为90 min时,除铁利用率达到98.4%,实现除铁氧化锰粉的高效利用。

河床浅层地下水水源净水厂工艺设计

潜山县皖水水厂设计总规模5.0万m^(3)/d,一期设计规模2.5万m^(3)/d。水源近期采用皖河浅层地下水,远期采用下浒山水库地表水。净水厂采用跌水曝气、混合、絮凝沉淀、过滤、消毒的处理工艺。论文对该工程水源选择、取水工程设计、处理工艺选择及主要处理构筑物设计参数进行了介绍,对该水厂的设计方案、工程特点及工程效益进行了分析、总结。

生物固锰除锰机理与生物除铁除锰技术

在pH中性条件下生物接触滤层中Mn2+的氧化是生物氧化,滤层中以除锰菌为核心的生物群系的平衡与稳定是除锰活性的基础。生物滤层不但可以同时氧化去除Fe2+、Mn2+,而且对进入滤层前已氧化成Fe3+的微细颗粒也有良好的截留作用。以此生物固锰除锰机制为基础开发了弱曝气、一级过滤的生物除铁除锰简缩流程,确定了相应的设计与运行参数并指导了沈阳市开发区生物除铁除锰水厂的设计与运行。投产一年多来出水水质良好,总铁为痕量,锰<0.05mg/L。

生物除铁除锰在地下水处理厂的应用

黑龙江省兰西镇地下水处理厂采用生物除铁除锰技术取得了满意的铁、锰去除效果。尽管原水含铁量为10～14mg/L、含锰量为0.65～1.1mg/L,出厂水水质仍然优于国家饮用水标准,总铁<0.05～0.1mg/L,总锰<0.05mg/L,彻底解决了兰西镇居民的生产和生活用水问题。

生物除铁、除锰滤层中铁、锰的氧化还原关系

为进一步掌握生物除铁、除锰滤层中铁、锰的氧化还原关系,以天然高铁高锰地下水为原水、成熟生物除锰滤料为试验材料,进行了一系列静态和动态试验。结果表明:高浓度的Fe2+能够还原高价态锰氧化物而溶出Mn2+,同时破坏滤层上部的生物除锰滤层结构,迫使高效生物除锰段下移,这一现象与微生物的存在与否无关,属于物理化学反应。