Mechanism of phosphorus removal in beneficiation of high phosphorous oolitic hematite by direct reduction roasting with dephosphorization agent

High phosphorous oolitic hematite ore is one of typical intractable iron ores in China, and the conventional beneficiation methods are found to be impracticable to , remove phosphorus from the ore effectively. Better beneficiation index were gotten by direct reduction roasting with dephosphorization agent followed by two stages of grinding and magnetic separation. P content decreases from 0.82% in the raw ore to 0.06% in the magnetic concentrate, and the total iron grade increases from 43.65% to 90.23%, the recovery of iron can reach 87%. Mechanisms of phosphorus removal in the beneficiation of high phosphorous oolitic hematite ore by direct reduction roasting with dephosphorization agent were studied using XRD, SEM and EPMA. The results showed that about 20% of the apatite in the raw ore transferred into phosphorus and volatilized with the gas in the process of reduction roasting, while the rest 80% apatite was not involved in the reaction of generation of phosphorus, and remained as apatite in the roasted products, which was removed to tailings by grinding and magnetic separation. A small amount of phosphorus existed in the magnetic concentrate as apatite. The oolitic texture of raw ore was partly changed during roasting, resulting in the formation of nepheline in the reaction between the dephosphorization agent, SiO2 and Al2O3 in the raw ore, which greatly improved the liberation degree of minerals in the roasted products, and it was beneficial to the subsequent grinding and magnetic separation.

Denitrifying phosphorous removal in anaerobic/anoxic SBR system with different startup operation mode

To achieve stable and efficient nitrogen and phosphorus removal and to investigate the characteristics of the A/A SBR enriched with denitrifying phosphorus removal bacteria(DPB),the whole course of startup was studied with two reactors operated in different mode.The reactor I was operated under anaerobic/settling/anoxic/settling mode,and the reactor II was operated under anaerobic/anoxic/settling mode.Differences between the two reactors in removal efficiency of COD,nitrogen and phosphorus were examined.The results indicated that efficient performance could be achieved in both reactors with different startup operation mode,while the phosphorus removal efficiency was improved sooner in reactor I than in reactor II,which suggested that reactor I would supply a more favorable condition for DPB proliferation.Meanwhile,it was observed that the amount of organic substrates consumption had a linear correlation to that of phosphorus release in anaerobic phase when DPB was accumulated in the A/A SBR denitrifying phosphorus removal system.

Characterization of Microcystis Aeruginosa immobilized in complex of PVA and sodium alginate and its application on phosphorous removal in wastewater

Based on ecological niche theory, Microcystis Aeruginosa(MA) immobilized in the complex of polyvinyl alcohol(PVA)and sodium alginate(SA) crosslinked by CaCl2, was treated as a new kind of special species, and its properties were investigated.Chlorophyll a was used to characterize the bioactivity of the immobilized MA. Results reveal that the gel beads have mechanical strength and chemical stability even under non-sterile harsh conditions, which may be attributed to the rarely seen structure(including three different layers: dense surface, tubular-shaped divergent structure and honeycomb crystal lattice layer) of the immobilized MA determined by scanning electron microscope(SEM). SEM also displays that more quantity of MA is attached to the inwall after cultivation, which demonstrates that the MA within beads maintains high bioactivity. Removal capacities on phosphorous(P) removal in wastewater in the presence and absence of the BG-11 medium were examined, and the removal ratios are 80.3% and76.7%, respectively, which indicates that the beads without providing ample nutrients still have high capacity of P removal. In addition, control experiment, utilizing polyvinyl alcohol and sodium alginate(PVA-SA) beads without immobilized MA,demonstrates that MA within beads plays the key role in absorbing P.

A Study on the Structure and Behavior of Sinter-free Material for Phosphorous Removal from Waste Water

Oyster shell and cement were taken as the major raw materials to fabricate hollow, tubular and recoverable material for phosphorous removal （P removal） from waste water without sintering. In this paper, the effects of different affecting factors on the sample P removal ratio were discussed to select optimal P removal process conditions. SEM and XRD were used to characterize the microscopic structures and composition of samples, and molybdenum blue spectrophotometry was applied to determine the P content in waste water. Results showed that at 30 ℃ for 2 d, the P removal ratio reached 93.3% when the cement content was 10 wt% and oyster shell powder was 90 wt%. SEM analysis revealed a flaky structure consisting of phosphorus-containing compound in the samples after P removal, and it piled on and maintained the porous structure. In addition, the results also suggested that raising the ambient temperature was benefit to the P removal. The P removal ratio of the material was optimal under neutral and alkali conditions.

Advanced sludge reduction and phosphorous removal process

An advanced sludge reduction process, i.e. sludge reduction and phosphorous removal process, was developed. The results show that excellent sludge reduction and biological phosphorous removal can be achieved perfectly in this system. When chemical oxygen demand ρ（COD） is 332 - 420 mg/L, concentration of ammonia p（NH3-N） is 30 - 40 mg/L and concentration of total phosphorous p（TP） is 6.0 -9.0 mg/L in influent, the system still ensures ρ（COD）〈23 mg/L, ρ（NH3-N）〈3.2 mg/L and ρ（TP）〈0. 72 mg/L in effluent. Besides, when the concentration of dissolved oxygen ρ（DO） is around 1.0 mg/L, sludge production is less than 0. 140 g with the consumption of 1 g COD, and the phosphorous removal exceeds 91 %. Also, 48.4% of total nitrogen is removed by simultaneous nitrification and denitrification.

Arsenic removal from contaminated soil using phosphoric acid and phosphate

Laboratory batch experiments were conducted to study arsenic （As） removal from a naturally contaminated soil using phosphoric acid （H3PO4） and potassium dihydrogen phosphate （KHEPO4）. Both H3PO4 and KHEPO4 proved to reduce toxicity of the soil in terms of soil As content, attaining more than 20% As removal at a concentration of 200 mmol/L. At the same time, acidification of soil and dissolution of soil components （Ca, Mg, and Si） resulted from using these two extractants, especially H3PO4. The effectiveness of these two extractants could be attributed to the replacement of As by phosphate ions （PO4^3-）. The function of H3PO4 as an acid to dissolve soil components had little effects on As removal. KH2PO4 almost removed as much As as H3PO4, but it did not result in serious damage to soils, indicating that it was a more promising extractant. The results of a kinetic study showed that As removal reached equilibrium after incubation for 360 rain, but dissolution of soil components, especially Mg and Ca, was very rapid. Therefore dissolution of soil components would be inevitable if As was further removed. Elovich model best described the kinetic data of As removal among the four models used in the kinetic study.

Effect of Ferric Chloride on the Properties of Biological Sludge in Co-precipitation Phosphorus Removal Process

This paper studied the effect of ferric chloride on waste sludge digestion,dewatering and sedimentation under the optimized doses in co-precipitation phosphorus removal process.The experimental results showed that the concentration of mixed liquid suspended solid(MLSS) was 2436 mg.L-1 and 2385 mg.L-1 in co-precipitation phosphorus removal process(CPR) and biological phosphorous removal process(BPR),respectively.The sludge reduction ratio for each process was 22.6% and 24.6% in aerobic digestion,and 27.6% and 29.9% in anaerobic digestion,respectively.Due to the addition of chemical to the end of aeration tank,the sludge content of CPR was slightly higher than that of BPR,but the sludge reduction rate for both processes had no distinct difference.The sludge volume index(SVI) and sludge specific resistance of BPR were 126 ml.g-1 and 11.7×1012 m.kg-1,respectively,while those of CPR were only 98 ml.g-1 and 7.1×1012 m.kg-1,indicating that CPR chemical could improve sludge settling and dewatering.

Adsorbent for Arsenic(V) Removal Synthesized by Radiation-Induced Graft Polymerization onto Nonwoven Cotton Fabric

A fibrous adsorbent for arsenic (As) removal was synthesized with nonwoven cotton fabric as a trunk polymer. 2-hydroxyethyl methacrylate phosphoric acid monomer which composed of phosphoric acid mono (50%) and di (50%) ethyl methacrylate ester was introduced with radiation-induced graft polymerization onto nonwoven cotton fabric. The degree of grafting of 130% was obtained at irradiation dose of 20 kGy with 5% of monomer solution for 2 hours reaction time at 40?C reaction temperature. After the grafted material was contacted with 10 mmol/L of zirconium (Zr) solution at pH 1, 0.38 mmol/g of Zr was loaded on phosphoric units as a functional group for As(V) removal. The resulting adsorbent was evaluated by column mode adsorption with 1 mg/L of As(V) solution at various pH with space velocity 200 h–1. The maximum capacity of As(V) adsorption was 0.1 mmol/g at pH 2.

湿法磷酸脱氟工艺的研究现状与发展方向

阐述了氟对湿法磷酸生产工艺的影响,综述了针对湿法磷酸的主要脱氟工艺的原理、应用现状及优缺点。指出了目前湿法磷酸脱氟工艺存在的问题,并分析了未来的研究发展方向,以期为我国湿法磷酸中氟资源的综合利用提供参考。

红土镍矿硝酸加压浸出渣制备电池级磷酸铁

近年来,在我国“碳达峰”和“碳中和”目标的引领下,新能源行业发展迅速,新能源汽车的推广与使用促进了锂离子电池行业的蓬勃发展。作为三元锂电池的关键原材料,镍的需求量不断增加。但由于硫化镍矿日益枯竭,红土镍矿逐渐成为了主要的提镍原料,在镍产量中占比超过70%。褐铁型红土镍矿在红土镍矿中占比超过60%,经硝酸加压浸出(NAPL)提取镍钴后产生的浸出渣中含有丰富的有价金属资源(铁含量>60%),浸出渣的综合利用对资源回收和环境保护具有重要意义。以褐铁型红土镍矿硝酸加压浸出渣为原料,在磷酸单一介质中制备电池级磷酸铁材料。以磷酸为介质,通过预浸、溶解实现浸出渣中铁的高效提取。预浸时磷酸溶液浓度较低,可以使含铁相初步转型为FePO_(4)·2H_(2)O,同时除去浸出渣中Cr、Mg、Al等杂质元素。然后采用高浓度磷酸溶液溶解处理预浸渣,实现Fe的完全溶解。最后稀释调节pH值直接沉淀制备磷酸铁,得到FePO_(4)·2H_(2)O产品,该产品不含杂质元素Mg、Si,Cr、Al的含量为0.019%、0.016%。通过XRD、SEM、EDS等技术手段对预浸渣和磷酸铁产品的物相组成和微观形貌进行了研究,明确了预浸过程可实现铁由Fe_(2)O_(3)向FePO_(4)·2H_(2)O的转变,最终产品的晶体结构与标准磷酸铁相匹配。由磷酸铁合成的磷酸铁锂材料也表现出优异的电化学性能。该研究有望实现对褐铁型红土镍矿硝酸加压浸出渣中宏量组元铁的高值化利用,从而优化磷酸铁制备工艺。

化学除磷方式对城镇污水处理厂生物除磷影响研究

基于污水厂生物段活性污泥厌氧释磷模拟试验及全流程PO43--P迁移转化分析,对采用同步化学除磷和后置化学除磷的城镇污水处理厂进行生物除磷功能研究。结果表明:同步化学除磷会在一定程度削弱系统生物除磷功能,且化学药剂投加量越多,影响越大,甚至会使生物除磷功能完全丧失;后置化学除磷对生物除磷功能完全没有影响,可节省药剂使用量;具有生物除磷能力的活性污泥系统更有利于缺氧段反硝化除磷的工程实现和降低建设、运行成本。

纳滤膜脱除磷酸中金属离子的实验研究

湿法磷酸中含有大量多价金属离子,需要通过低成本、低污染的途径去除。纳滤膜已经在水处理中得到广泛应用,但对于酸性体系尤其是磷酸体系中金属离子脱除的研究还很少。通过对5种纳滤膜在磷酸中的分离性能进行研究,结果表明:随着磷酸浓度和温度的升高,纳滤膜对金属离子的截留率有不同程度的下降;选择分离层材质对纳滤膜在磷酸中的分离性能有很大的影响;纳滤膜的分离效果受到空间位阻、介电排斥、Donnan排斥多重机制相互作用的影响。在研究的商业膜中,NF4的分离性能受磷酸浓度和温度变化影响最小,且具有良好的酸稳定性。在30℃条件下,NF4对P_(2)O_5质量分数为20%的磷酸溶液中的Fe^(3+)、Al^(3+)、Mg^(2+)平均截留率均大于84.83%,对磷酸的截留率小于5%,在磷酸净化中有很好的应用前景。

萃取法脱除湿法磷酸金属阳离子新工艺开发

针对云南云天化集团生产的湿法磷酸中金属阳离子含量较高的问题,研发了一种溶剂萃取法脱除金属阳离子净化湿法磷酸的新工艺,并完成了1000 t/a(以五氧化二磷计)萃取法脱除湿法磷酸金属阳离子的中试实验。考察了萃取时间、萃取温度、搅拌转速和相比对萃取效果的影响,确定了较优工艺条件:反应时间为20 min、反应温度为60℃、搅拌转速为400 r/min、相比(萃取剂与磷酸的体积比)为3。中试实验结果表明,净化后的湿法磷酸MER(湿法磷酸中的杂质系数)值可从0.114降到0.06以下,三氧化二铁、氧化铝、氧化镁的脱除率可分别达到88.37%、48.93%、45.33%。经过洗涤五氧化二磷总收率可达到98.46%。净化1 t湿法磷酸(以五氧化二磷计)所消耗的物料成本为222.5元。中试实验结果证明,这种脱除湿法磷酸中金属阳离子的净化新工艺是可以进行工业化应用的。实验结果可为工业放大提供可靠的依据。

改性膨润土对水中磷和藻类的同步去除

为快速去除富营养化水体中的磷和藻类,制备了絮凝剂-镧复合改性膨润土(聚合氯化铝铁-镧复合改性膨润土(PAFC-La)、聚合硫酸铝-镧复合改性膨润土(PAS-La)、聚合硫酸铁-镧复合改性膨润土(PFS-La)、聚合氯化铝-镧复合改性膨润土(PAC-La)),对材料进行表征,通过吸附动力学和等温吸附模型比较4种复合改性膨润土的除磷性能,并探究投药量和pH对复合改性膨润土除磷除藻的影响。结果表明,4种材料吸附磷的过程均能由准二级动力学模型和Langmuir等温吸附模型描述。其中,PAC-La的磷吸附容量最大(44.677 mg/g);投药量为300 mg/L时,总磷(TP)去除率最高的是PAC-La(94.1%),叶绿素a(Chla)去除率最高的是PFS-La(78.2%);在pH为5~10时,PAC-La除磷除藻效果受pH影响最小。实验结果表明,采用絮凝剂-镧复合改性膨润土能够同步去除富营养化水体中的磷和藻类,尤其是采用PAC-La性能最优。

河道底泥和植物制备生物炭吸附磷的影响研究

为探究富营养化水体联合修复技术,协同解决河道底泥污染、植物垃圾和水体中磷过量的问题,采用河道底泥和植物垃圾共热解制备改性生物炭吸附水体中的磷,研究生物炭原料配比、热解时间和温度、改性剂及其配比等制备条件对生物炭吸附磷的影响,探究溶液pH和共存离子等条件对Fe改性生物炭吸附磷的影响。结果表明:Fe改性生物炭20:10:3-ZNBC450-3Fe对低质量浓度磷(1 mg/L)吸附量为2.76 mg/g,去除率为68.96%。中性条件下Fe改性生物炭吸附磷的效果较好,Na^(+)、K^(+)和Cl^(−)对生物炭吸附磷有明显的促进作用,Al^(3+)、CO_(3)^(2−)和SO_(4)^(2−)却有明显的抑制作用。Fe改性生物炭吸附磷符合准二级动力学和Freundlich吸附等温线模型。SEM-EDS检测证明了Fe改性生物炭吸附磷的有效性。河道底泥和植物垃圾共热解制备生物炭吸附水体磷,是一种联合物理、化学和生物手段全面修复景观水生态系统的技术,具有良好的应用前景。

湿法磷酸中脱除重金属的工艺研究

介绍了一种H2S循环脱湿法磷酸重金属的新工艺,通过对比分析了H2S循环脱湿法磷酸重金属新工艺与传统Na2S溶液脱重金属工艺的脱除效率、工艺安全性、循环经济性以及技术经济性,结论如下:H2S循环脱湿法磷酸重金属新工艺可以实现脱As后折85%H3PO4中As指标降至0.5mg/kg;本工艺拥有较高的工艺安全性、循环经济性、技术经济性,可使原料Na2S和NaOH的消耗量优化倍数达到了117、5.8倍,S元素的总利用率为94.5%,H2S循环脱重金属新工艺的尾气量由传统工艺的10 400 m3/kg(以As计)减至4 800 m3/kg(以As计)。

稀土La改性污泥制备介孔陶粒及其除磷性能研究

随着我国城镇化的高速发展,污水处理产生的污泥量迅速增加,随之而来污泥的处理和处置也越来越突出。本研究以污水处理厂污泥为主要原料,通过稀土金属La改性污泥后,添加粉煤灰、蒙脱石为辅料制备得到一种介孔污泥陶粒(MSC),并探讨了其对模拟含磷废水的吸附性能。研究结果表明,当改性污泥:粉煤灰:蒙脱石质量配比为4:3:1制备得到的MSC具有丰富的孔隙结构,其比表面积为4.292m^(2)/g,单孔孔容为0.627cm^(3)/g;当pH为5.0的条件下,投加量为10g/L时,MSC对模拟废水(总磷浓度10mg/L)中磷酸盐吸附率达到98.5%。

精制磷酸脱砷技术研究

研究了以硫化钠作为脱砷剂脱除工业磷酸中砷的脱砷方法。重点分析了硫化钠加入量、反应温度、反应时间和陈化时间对工业磷酸脱砷效果的影响。结果表明:以硫化钠作为脱砷剂能有效脱除磷酸中的砷,脱砷率可达95.7%以上。

Preparation of Iron-Pillared Bentonite/Oyster Shell Composite and Phosphate Adsorption in Water

Iron-pillared bentonite(FB)was prepared by Fe(III)modified bentonite,and then the composites(FB-OS)were prepared by iron-pillared bentonite and oyster shell powder.The composites were characterized by FTIR,SEM,TGA,and EDS,and the phosphorus removal test was carried out.The results showed that FB-OS contained a large amount of CaO.Its structure was compact,but there were gaps in it.The maximum bending stress and compressive strength were 43.7 N and 0.927 MPa,respectively.The phosphorus removal test showed that the phosphorus removal rate of FB-OS was more than 90%,and measured the maximum adsorption capacity was 48.31 mg/g.A large amount of spherical products were produced on the surface and inside of FB-OS after phos-phorus removal,it was speculated that spherical products were amorphous calcium phosphate in the paper.Ana-lysis indicated that there was chemical adsorption during phosphorus removal.The kinetic equation of phosphorus adsorption by FB-OS was qt=10:193t/1+2:574t (R^(2)=0.995).The adsorption rate was mainly controlled by outerfilm diffusion and intraparticle diffusion.

二维材料及其复合物在除磷方面的研究现状

石墨烯的发现促使二维材料蓬勃发展。与传统材料相比,二维材料具有超高的比表面积,优异的光、电和机械性能,将在众多领域带来变革性的影响。在水处理方面,二维材料作为催化剂、吸附剂和膜材料进行了探索应用。磷是引发水体富营养化是主要因素之一,对磷的去除是水体修复的一大问题。本文综述了二维材料及其复合物在水体磷去除方面的研究与应用现状,罗列了二维材料的分子结构和性能特征,并总结了这些材料在磷去除过程中的作用机理。