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.

BER-BCO耦合工艺净化模拟微污染河水及除磷机理研究

针对传统生物膜法对微污染河水脱氮除磷效率不佳的问题,设计了电极生物膜耦合生物接触氧化(BER-BCO)装置,采用单因素敏感性分析方法评估了不同碳源、电流密度、水力停留时间、填料填充比对工艺脱氮除磷效果的影响,并通过红外光谱表征阳极附近沉淀物表面特征官能团,探究系统除磷机理。结果表明,在使用乙酸钠为碳源、电流密度为0.09 mA/cm^(2)、水力停留时间控制为24 h、填料比为40%的条件下,BER-BCO系统的脱氮除磷效能得到了显著优化;NH+4-N、TN、TP的去除率分别达到了83.10%、56.46%、97.93%;最终出水除TN外均优于《地表水环境质量标准》(GB 3838-2002)中Ⅳ类水质标准;红外光谱分析显示阳极附近形成的含磷沉淀物中含有Fe-O键、P-O键、Fe-OH键,表明铁阳极具有高效除磷的特性。

Removal of iron from ilmenite by KOH leaching-oxalate leaching method

Oxalic acid was used for the removal of iron from the intermediates of ilmenite leached by KOH liquor. Various parameters, such as pH, temperature, initial oxalate concentration, and illumination were investigated. Meanwhile, it was found that orthorhombic crystal Ti2O2（OH）2（C2O4）-H2O formed as the leaching proceeded. Scanning electronic microscope （SEM） images implied that the formation of Ti2O2（OH）2（C2O4）.H2O with good crystallinity proceeded through three stages. Calcining Ti2O2（OH）2（C2O4）·H2O, anatase （350℃） or mtile （550℃） type TiO2 was obtained, respectively. Element analysis found that the calcined product contained 94.9% TiO2 and 2.5% iron oxide, but only about 1600 ppm dissolvable iron oxide was left, which indicates that oxalic acid was comparatively effective on iron oxide removal from the intermediates. Finally, an improved route was proposed for the upgrading of ilmenite into mtile.

Removal of primary iron rich phase from aluminum-silicon melt by centrifugal separation

Recycling is a major consideration in continued aluminum use due to the enormous demand for high quality products. Some impurity elements gradually accumulate through the repetitive reuse of aluminum alloy scrap. Of them, the iron content should be suppressed under the allowed limit. In the present research, a novel separation method was introduced to remove primary iron-rich intermetallic compounds by centrifugation during solidification of AI-Si-Fe alloys. This method does not use the density difference between two phases as in other centrifugal methods, but uses the order of solidification in AI-Si-Fe alloys, because iron promotes the formation of intermetallic compounds with other alloying elements as a primary phase. Two AI-Si-Fe alloys which have different iron contents were chosen as the starting materials. The iron-rich phase could be efficiently removed by centrifuging under a centrifugal force of 40 g. Coarse intermetallic compounds were found in the sample inside the crucible, while rather fine intermetallic compounds were found in the sample outside the crucible. Primary intermetallic compounds were linked to each other via aluminum-rich matrix, and formed like a network. The highest iron removal fraction is 67% and the lowest one is 7% for AI-12Si-1.7Fe alloy. And they are 82% and 18% for AI-12Si-3.4Fe alloy, respectively.

Effect of calcium compounds on direct reduction and phosphorus removal of high-phosphorus iron ore

The increasing demand for iron ore in the world causes the continuous exhaustion of magnetite resources.The utilization of high-phosphorus iron ore becomes the focus.With calcium carbonate(CaCO_(3)),calcium chloride(CaCl_(2)),or calcium sulfate(CaSO_(4))as additive,the process of direct reduction and phosphorus removal of high-phosphorus iron ore(phosphorus mainly occurred in the form of Fe_(3)PO_(7) and apatite)was studied by using the technique of direct reductiongrinding-magnetic separation.The mechanism of calcium compounds to reduce phosphorus was investigated from thermodynamics,iron metallization degree,mineral composition and microstructure.Results showed that Fe_(3)PO_(7) was reduced to elemental phosphorus without calcium compounds.The iron-phosphorus alloy was generated by react of metallic iron and phosphorus,resulting in high phosphorus in reduced iron products.CaCO_(3) promoted the reduction of hematite and magnetite,and improved iron metallization degree,but inhibited the growth of metallic iron particles.CaCl_(2) strengthened the growth of iron particles.However,the recovery of iron was reduced due to the formation of volatile FeCl_(2).CaSO_(4) promoted the growth of iron particles,but the recovery of iron was drastically reduced due to the formation of non-magnetic FeS.CaCO_(3),CaCl_(2) or CaSO_(4) could react with Fe_(3)PO_(7) to form calcium phosphate(Ca_(3)(PO_(4))_(2)).With the addition of CaCO_(3),Ca_(3)(PO_(4))_(2) was closely combined with fine iron particles.It is difficult to separate iron and phosphorus by grinding and magnetic separation,resulting in the reduced iron product phosphorus content of 0.18%.In the presence of CaCl_(2) or CaSO_(4),the boundary between the generated Ca_(3)(PO_(4))_(2) and the metallic iron particles was obvious.Phosphorus was removed by grinding and magnetic separation,and the phosphorus content in the reduced iron product was less than 0.10%.

Removing Iron by Magnetic Separation from a Potash Feldspar Ore

A new permanent magnetic separator was introduced to treat the ores with the characteristics of weak magnetic iron minerals and in a fine size range. The new machine was applied to the iron removal from potash feldspar. The effects of the magnetic field intensity, pulp density and grinding fineness on the iron removal were investigated. The optimized operation parameters were achieved and listed as follows： the -0.074 mm content is 85%, the pulp density is 45% and the magnetic field strength is 2T. A close test of middles regrinding was also carried out to improve concentrate yield. The data show that the grade of TFe（total iron） in potash feldspar product decreased from 1.31% to 0.21% and the concentrate yield reached 85.32%. All the results indicated that the traditonal high-intensity electromagnetic separators can be betterly substituted by the new permanent magnetic separator. This study may provide the theoretical evidence for iron removal from potash feldspar.

基于海绵铁-斜发沸石组合系统的模拟农村黑臭水体脱氮除磷研究

农村水体黑臭污染现象仍不容忽视。研究以海绵铁及斜发沸石为基质,分别按0/1、1/10、1/5及1/1的填充体积配比构建了四组柱反应器(Device-Ⅰ~Device-Ⅳ),考察了各反应器在连续流及潮汐流进水方式下对低C/N模拟农村黑臭水体中氮磷等污染物的脱除表现,并对作用前后的填料进行表征,分析了反应器内微生物的自然生长情况。结果表明,海绵铁可强化系统NO_(3)^(-)-N及TP的去除效果,并在潮汐流下利于COD的去除。潮汐进水方式下,具海绵铁反应器的NO_(3)^(-)-N及TP去除率均可分别超过98%及95%,Device-Ⅱ平均NO_(3)^(-)-N及TP去除率分别可达99.66%及99.36%,COD最高去除率可达93.38%。系统NH_(4)^(+)-N的脱除依赖于斜发沸石的作用,潮汐进水促进了沸石系统的生物再生,可弥补连续流下氧缺乏及微生物作用低下对系统NH4+-N脱除的限制。

Iron-Modification of Pyroclastic Material from PCCVC Eruption (Chile): Characterization and Application to Remove Arsenic from Groundwater

Pyroclastic material from the PCCVC eruption (Chile) was modified with iron (III) solutions leading to the formation of ferrihydrite surface deposits. The aim of the chemical treatment was to prepare an adsorbent to remove arsenic from water by using low-cost mineral wastes. Physicochemical characterization of original and modified materials was carried out by XRD, BET-N2 adsorption, SEM-EDS microscopy and ICP-AES chemical analysis. The modified ash revealed that the increase of bulk iron content was close to 5% (expressed as Fe2O3) whereas surface values were 20.6% Fe2O3. Surface properties showed an increase of BET specific surface with prevalence of mesopores and an increase of total pore volume attributed to presence of nanoscopic iron phase. Kinetic and equilibrium studies were directed to optimize the operative conditions related to the material adsorptive capacity for removing arsenate species. Hence, the adsorbent dose, contact time, pH, stirring and sedimentation were evaluated in batch process. The optimal adsorption dose was 40 g ·L-1 and the solid-liquid contact time was stirring (1 h) and sedimentation (23 h), enough to ensure an adequate turbidity value valid for a pH range between 3.77 and 8.95. The analysis of the isotherm equilibrium by using the Langmuir linear method showed a R2 = 0.995 value. The performance of the treatment to remove arsenic by using a cost-effective adsorbent prepared from volcanic material is a promising technology to apply in the environmental field.

Nitrogen removal efficiency of iron-carbon micro-electrolysis system treating high nitrate nitrogen organic pharmaceutical wastewater

The nitrate nitrogen removal efficiency of iron-carbon micro-electrolysis system was discussed in treating pharmaceutical wastewater with high nitrogen and refractory organic concentration. The results show that the granularity of fillings,pH,volume ratios of iron-carbon and gas-water,and HRT. have significant effects on the nitrogen removal efficiency of iron-carbon micro-electrolysis system. The iron-carbon micro-electrolysis system has a good removal efficiency of pharmaceutical wastewater with high nitrogen and refractory organic concentration when the influent TN,NH4+-N,NO3--N and BOD5/CODCr are 823 mg/L,30 mg/L,793 mg/L and 0.1,respectively,at the granularity of iron and carbon 0.425 mm,pH 3,iron-carbon ratio 3,gas-water ratio 5,HRT 1.5 h,and the removal rates of TN,NH4+-N and NO3--N achieve 51.5%,70% and 50.94%,respectively.

Separation of Kaolinite from Ion-Adsorption Rare Earth Tailings in Southern China and Iron Removal Treatment

Several hundred million tons of ion-adsorption rare earth tailings exist in Ganzhou, Southern China, which is a severe environmental hazard. To reduce and reutilize the tailing, kaolinite has been separated from the tailings by mechanical separation in laboratory scale and pilot scale. The results show that the tailing is mainly composed of fine kaolinite and coarse quart. Quartz and kaolinite can be separated by sieves, shaker, spiral chute or hydrocyclone, which has the similar results in laboratory scale and pilot scale. 30.2% of the tailings can be re-sourced and applied in ceramic industries. 41.7% of kaolinite can be obtained after sorting and iron removal by magnetic separator in pilot scale, which can be applied in ceramic industries according to the Chinese national standard (TC-3). The results give a progressive solution to re-source the tailings economically.

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.

黄铁矿-硫自养反硝化生物滤池同步脱氮除磷

基于黄铁矿的自养反硝化(PAD)工艺具有成本低,产泥量少等优点,是一种具有前景的低C、N比废水脱氮除磷技术。然而,与其他硫基自养反硝化(SAD)工艺相比,PAD的动力学较慢,限制了其工程应用。为此,构建了黄铁矿、硫单质为填料的自养反硝化生物滤池(PSAD-BF)和黄铁矿为填料的硫化钠驱动的自养反硝化生物滤池(SAD-BF),PSAD-BF的硝酸盐去除负荷和去除率均高于SAD-BF,FeS_(2)和S^(0)之间的相互作用加速了反硝化过程并维持了酸碱平衡,减少了硫酸盐的产生,同时通过生成FePO_(4)和Fe_(3)(PO_(4))_(2)(OH)_(2)去除磷酸盐。长期运行结果表明:在HRT为3~12 h时,PSAD-BF对总氮和磷酸盐的去除率达到90%~100%,最高反硝化速率可达600 mg/(L·d)。PSAD-BF是一种很有前途的实现铁硫耦合自养反硝化除磷的工艺。

Characterization and Iron Removal Treatment of Ion-Adsorption Rare Earth Tailings in Southern China

The ion-adsorption rare earth tailings have become a serious environmental pollution in Southern China, yet the potential of their economical value has not been fully exploited. In this work, the chemical and mineral compositions of the ion-adsorption rare earth tailings were characterized by Mineral Liberation Analyze (MLA) and XRF. The results show that 91.98 wt% of the tailings are composed of kaolinite and quartz, latter of which was removed by the sieving method. The other minor minerals contain feldspar, biotite, muscovite, titanomagnetite and limonite. Amongst these, the iron-bearing minerals are mostly found in the titanomagnetite and limonite which can be mostly removed by using a periodic high-gradient magnetic separator with a magnetic induction of 0.6 Tesla. The Fe2O3 content of the tailings changed from 2.11 wt% to 1.06 wt% after the sorting process, which met the Chinese national standard of TC-3 grade raw materials for ceramic industry applications. The Fe2O3 content in kaolinite was further decreased after Na2S2O4 treatment.

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.

铁-碳微电解法处理铜冶炼含砷废水的实验研究

采用铁-碳微电解法处理铜冶炼含砷废水,考察了进水pH值、空气鼓入量、接触时间、振动频率、固液比(铁-碳微电解材料质量∶每分钟进水质量)等工艺参数对除砷效率的影响。结果表明,铁-碳微电解材料处理铜冶炼含砷废水时,生成的FeAsO4、Fe2O3、Fe3O4等氧化物沉积在铁-碳微电解材料表面,使铁-碳微电解材料钝化失效,导致除砷效率差,采用振动的方法可有效解决铁-碳微电解材料钝化失效问题;在进水pH值2.0、空气鼓入量5 L/min、接触时间2 min、固液比2.5∶1、振动频率每4 h振动2 min条件下,铁-碳微电解材料连续稳定处理废水90 d,除砷率达99.99%,水中砷含量降至0.033~0.036 mg/L,除砷效果理想且稳定。采用铁-碳微电解法除砷,为处理铜冶炼含砷废水提供了新思路。

高砷铜精矿硫化钠-氢氧化钠碱浸除砷

云南某高砷铜精矿铜品位为13.46%,含砷质量分数为5.17%,主要矿物为黄铜矿、黄铁矿、毒砂、含砷黄锡矿、锡石和镁铝硅酸盐。在硫化钠-氢氧化钠碱性体系下浸出高砷铜精矿的砷,系统研究工艺参数条件如氢氧化钠浓度、硫化钠用量、浸出温度、转速、液固比、浸出时间等对砷脱除率的影响。结果表明,上述工艺参数条件均对砷的碱浸脱除率影响较大,最佳浸出工艺条件为:氢氧化钠浓度5 mol/L、硫化钠浓度为50 g/L、浸出温度90℃、转速为1000 r/min、液固比为10∶1、浸出时间为3 h,在此最佳条件下可最终获得砷去除率为60.55%的技术指标。采用EMPA-EDS对碱浸渣进一步分析发现,采用硫化钠-氢氧化钠碱性体系浸出可完全溶解高砷铜精矿中的毒砂,浸出渣中主要含砷矿物为含锌硫砷铜矿和砷黝铜矿;浸出过程形成的氢氧化铁以及脱水后生成的氧化铁覆盖在含砷矿物表面,阻碍了碱性浸出剂与矿物的充分接触,影响了浸出过程传质效果。

基于六偏磷酸钠-Fe^(2+)的铁盐脱氮反应器运行性能及微生物学特征研究

以实验室高效反硝化反应器中的反硝化污泥作为接种污泥,启动自养型六偏磷酸钠-Fe^(2+)脱氮反应器,试验采用模拟废水通过88 d的不间断运行,研究了铁盐脱氮工艺的脱氮效能及其微生物学特性。结果表明,当反应器硝态氮容积负荷为0.42 kg/(m^(3)·d)时,最高稳定氮去除负荷为0.41 kg/(m^(3)·d);当Fe^(2+)容积负荷为4.92 kg/(m^(3)·d)时,最大铁去除负荷为2.77 kg/(m^(3)·d)。反应器稳定运行时硝态氮、Fe^(2+)的去除率分别达94.6%、52.6%,最佳效能可维持28 d。反应器运行到第82天时,颗粒污泥由黄色变为灰褐色,颗粒解体,污泥比活性逐渐升高,比反硝化活性由0.71 mg[N]/(g[VSS]·h)升高到2.3 mg[N]/(g[VSS]·h),同比上升224%;比铁氧化活性由7.3 mg[Fe]/(g[VSS]·h)升高到15 mg[Fe]/(g[VSS]·h),同比上升105%。六偏磷酸钠-Fe^(2+)脱氮作为一种新型自养反硝化技术,不仅增强了活细菌的生物活性和反硝化活性,还延长了铁盐脱氮污泥反硝化的高效期。

Correlation between Iron Reducibility in Natural and Iron-Modified Clays and Its Adsorptive Capability for Arsenic Removal

The study reports aspects that allowed to correlate structural and redox properties of iron species deposited on clay minerals with the capacity of geomaterials for arsenic removal. Natural ferruginous clays as well as an iron-poor clay chemically modified with Fe(III) salt (ferrihydrite species) were investigated as adsorbents of the arsenate(V) in water. The study, carried out from minerals from abundant Argentinean deposits, was conducted with the aid of different techniques such as X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM-EDS), Raman Spectroscopy, ICP-AES (Inductively Coupled Plasma) chemical analysis and Temperature Programmed Reduction (TPR). This last technique allowed to detect availability of iron species in oxidic environment with different structural complexity and to determine active sites, accessible for arsenate(V) adsorption. The effect was observed through temperature dependence of the first Fe(III) reduction step (below 570°C) of iron-oxide species. The sequence of reducibility: ferrihydrite > hydrous oxide (goethite) > anhydrous oxide (hematite) > structural iron in clay was in agreement with the availability of iron active sites for the reducing process as well as for the arsenate adsorption. The important role of very high iron content in original samples was also observed. The chemical activation of iron-poor clay by a simple and feasible modification with Fe(III) solutions promoted the deposition of the ferrihydrite active phase with an increase of 2.81% (expressed as Fe2O3) respect to the original content of 1.07%, constituting an accessible and eco-friendly technological alternative to solve the environmental problem of water containing arsenic.

Alcohothermal synthesis of sulfidated zero-valent iron for enhanced Cr(Ⅵ)removal

Sulfidation of zero-valent iron(ZVI)has attracted broad attention in recent years for improving the sequestration of contaminants from water.However,sulfidated ZVI(S-ZVI)is mostly synthesized in the aqueous phase,which usually causes the formation of a thick iron oxide layer on the ZVI surface and hinders the efficient electron transfer to the contaminants.In this study,an alcohothermal strategy was employed for S-ZVI synthesis by the one-step reaction of iron powder with elemental sulfur.It is found that ferrous sulfide(FeS)with high purity and fine crystallization was formed on the ZVI surface,which is extremely favorable for electron transfer.Cr(Ⅵ)removal experiments confirm that the rate constant of SZVI synthesized by the alcohothermal method was 267.1-and 5.4-fold higher than those of un-sulfidated ZVI and aqueous-phase synthesized S-ZVI,respectively.Systematic characterizations proved that Cr(Ⅵ)was reduced and co-precipitated on S-ZVI in the form of a Fe(Ⅲ)/Cr(Ⅲ)/Cr(Ⅵ)composite,suggesting its environmental benignancy.

Kinetics of iron removal from metallurgical grade silicon with pressure leaching

In this paper, the kinetics of pressure leaching for purification of metallurgical grade silicon with hydrochloric acid was investigated. The effects of particle size, temperature, total pressure, and concentration of hydrochloric acid on the kinetics and mechanism of iron removal were studied. It was found that the reaction kinetic model followed the shrinking core model, and the apparent activation energy of the leaching reaction was 46.908 kJ/mol. And the apparent reaction order of iron removal with pressure leaching was 0.899. The kinetic equation was obtained and the mathematical model of iron removal from metallurgical grade silicon （MG-Si） was given as follows：The values calculated from the equation were consistent with the experimental results.