超声波振荡对活性氧化铝除氟性能的影响

在超声波振荡搅拌下,实验研究了活性氧化铝对氟离子的吸附性能,分析了活性氧化铝颗粒大小、超声波振荡时间、pH、活性氧化铝加入量及原水氟浓度对吸附性能的影响。研究结果表明：活性氧化铝结晶不完整及晶格的无序使得它具有更大的比表面积;使用超声波振荡时,其除氟速率比机械搅拌快得多,除氟前期其平均除氟速率达0.93 mg/min,是机械搅拌除氟速率的5.8倍。同时,采用超声波振荡达到平衡的时间是机械搅拌的1/7,其饱和吸附容量也有所提高;pH在5～7时,活性氧化铝的吸附容量大、除氟速率高;另外,活性氧化铝的加入量及原水氟浓度对除氟速率和吸附容量也有重要影响。     

陶瓷膜短流程工艺处理重金属废水

针对电镀行业重金属废水常规处理方法存在的药剂投加量大、污泥产量多、水质波动影响大等不足,本文提出了一种新工艺-陶瓷膜短流程处理工艺,即废水通过调节pH值使重金属离子形成相应的氢氧化物絮体后,直接进入陶瓷膜组件过滤,同时辅以曝气缓解膜污染。通过实验室小试研究了pH值、重金属质量浓度和曝气量等因素对重金属(Cu²⁺、Cr³⁺和Ni²⁺)去除效果以及陶瓷膜跨膜压差的影响,并进行现场中试验证。试验结果表明:pH=10时,Cu²⁺、Cr³⁺和Ni²⁺的去除率分别达到99.8%、99.7%和99.9%,耐冲击负荷强,原水重金属离子质量浓度为500mg/L时出水也能满足要求。气水体积比值为15时,能在保证出水水质的前提下显著缓解膜污染。该工艺中陶瓷膜的污染主要为可逆污染,可以通过水力反冲洗去除。在pH=10、气水体积比值为15和膜通量为80L/(m²·h)时,现场中试工艺出水中Cu²⁺、Cr³⁺和Ni²⁺的质量浓度分别低于0.15mg/L、0.3mg/L和0.1mg/L,而且跨膜压差保持稳定。     

不同国产纳滤膜对饮用水中氟离子的去除影响研究

选用两种国产纳滤膜NF1和VNF2进行除氟的实验研究,考察了不同的原水pH、操作压力、进水F-浓度、温度以及腐殖酸的浓度对纳滤除氟截留率以及膜通量的影响。实验结果表明:VNF2膜的截留率高于NF1膜,而膜通量则低于NF1;同时两种膜的最佳操作条件为pH在6.5~7.0,温度在18~23℃,操作压力为0.4 MPa,进水氟离子浓度为4 mg/L;而腐殖酸主要通过静电斥力和氢键影响纳滤膜的截留率和膜通量,同时出水F-浓度满足生活饮用水卫生标准(GB5749-2006)。     

粉末活性炭-超滤膜组合工艺处理微污染原水试验研究

采用粉末活性炭和超滤膜联用技术对微污染原水进行试验,考察该工艺对溶解性有机物的去除效果、粉末炭改善膜通量以及防止膜污染的效果.结果表明,随着反应器内活性炭浓度升高,工艺处理效果有极大改善,膜通量明显提高,反应器最佳活性炭投加量为0.5 g·L-1,工艺运行1110min,出水TOC、UV254去除率保持稳定,平均去除率分别为44.8%、48.9%,膜通量降低缓慢,1110 min后通量为初始通量的70%.反冲洗对膜通量有所恢复,多次反冲后效果不明显,且反冲后破坏膜表面的滤饼层使出水水质稍有降低.     

电凝聚-膜滤组合工艺除氟试验研究

针对部队勤务特点,以除氟为对象,设计并运行了电凝聚一膜滤组合工艺除氟试验.结果表明,电流密度越大,出水F~-质量浓度越低;随着运行时间的延长,出水F~-质量浓度、电极组电阻和出水pH逐渐增大,跨膜压力达到临界值所经历的时间逐渐缩短.当原水F~-质量浓度为5 mg·L~(-1),HRT为10min,电流密度为51.02 A·m~(-2)时,电凝聚-膜滤组合工艺除氟出水F~-质量浓度能达到国家饮用水标准.利用pH为12的NaOH溶液浸泡受污染的膜组件,膜的运行周期明显延长.     

聚硅酸改性对活性氧化铝除氟性能的影响

采用聚硅酸对活性氧化铝进行改性,研究了SiO2百分含量、聚硅酸浸泡时间、焙烧温度及焙烧时间对改性活性氧化铝除氟性能的影响。结果表明,改性活性氧化铝能将水中的氟离子浓度从9.5 mg/L降低到0.89 mg/L,吸附容量提高了30%。因此,聚硅酸改性能有效提高活性氧化铝的除氟性能。     

深度除氟工艺处理煤化工尾水的研究

采用混凝沉淀、活性氧化铝吸附、树脂吸附等三种深度除氟技术对煤化工尾水处理。结果表明,混凝沉淀法最佳混凝剂为聚合氯化铝,最佳条件为初始pH为6～8,投加量为600 mg/L;活性氧化铝吸附最佳进水流量为4 BV/h,工作吸附容量为0.816 mg/mL,再生时间为90 min,再生率为96.1%;树脂吸附法最佳进水流量为8 BV/h,工作吸附容量为1.958 mg/mL,再生时间为120 min,再生率为97.7%。在最佳反应条件下,三种深度除氟技术处理煤化工尾水F~-均能达到1 mg/L的出水要求。并从除氟效果、投资、处理成本、有无二次污染等方面对这三种深度除氟工艺进行比较,确定出活性氧化铝吸附为最适宜的工艺。     

连续进水模式下电容去离子技术除氟研究

采用连续进水模式电容去离子技术(CDI)进行除氟研究,探讨了原水质量浓度、电压、流速、pH、共存离子、离子交换膜对除氟的影响,通过动力学分析探讨了其去除机理,并考察了电极的再生性能。结果表明,在原水质量浓度为50 mg/L、电压为1.5 V、流速为7 mL/min的条件下,电极吸附量可以达到3.17 mg/g。原水质量浓度越高、电压越大,电极的吸附量就越高。撤去电压电极即可高效再生,5次循环后,电极吸附能力可保持86%。离子交换膜可有效减弱pH波动,提高电极再生性能,但吸附量降低。连续进水模式下CDI除氟过程遵循准一级动力学模型,吸附速率与剩余电容成正比。     

水中天然有机物对超滤膜污染研究

对超滤膜受天然有机物污染的特性进行研究,同时考查无机矿物质成分对污染的协同影响。采用PES平板膜进行膜污染试验,模拟地表水研究腐殖酸以及钙离子的影响并进行了化学清洗试验。研究结果表明,在pH值为7.8,腐殖酸质量浓度为15 mg/L,操作压力0.1 MPa下,当钙离子浓度为4 mmol/L时,膜污染最为严重,10 min后膜通量降到起始膜通量的60%以下。先用0.1 mol/L的NaOH,再用0.5%的盐酸清洗后,膜通量可恢复至起始膜通量的98%。     

纳滤法处理含氟废水工艺条件的研究

采用Dow FilmTec公司的NF-90纳滤膜处理模拟含氟废水,主要考察了压力、pH、流量、温度、氟离子初始浓度等对膜渗透通量和氟离子截留率的影响。结果表明:压力升高,膜渗透通量增大,氟离子截留率先增大后减小;pH对膜渗透通量无明显影响,氟离子截留率随pH的升高而增大;流量升高膜渗透通量和氟离子截留率略有增大;温度升高,膜渗透通量增大,氟离子截留率降低;氟离子初始浓度增大,膜渗透通量减小,氟离子截留率降低。在压力1.0 MPa、pH 10.01、流量30 L/h、温度20℃的条件下NF-90膜截留率可达到95%;当处理氟浓度小于100 mg/L,出水氟浓度可达到国家工业一级排放标准。     

Use of membrane technology for potable water production

Excess fluoride in drinking water is harmful for human health, so it is necessary to be removed. In this study thepotential of a reverse osmosis (RO)membrane for defluoridation of underground water samples at different solute concentrations was studied. Because of the variation in feed water composition, its chemical properties, pH and operating conditions, effect of these parameters on the membrane separation process was studied. The results showed that pH, feed water composition, flow rate and pressure affect the membrane efficiency, and thus proper control of these factors is essential for successful operation, Optimum membrane properties and proper rejection were determined percentage for the RO system to minimize the overall cost of water treatment. The samples were collected from three villages in the Gurgaon district and treated at optimized conditions. The results indicate that RO membranes can be successfully used for the treatment of underground water to the desired purity level, as they remove up to 95% of fluoride present in water and also take care of other ions present in water.     

天然沸石活化处理研究

讨论了天然沸石用于除氟的可行性，通过静态实验优选出一种最佳的活化处理工艺，确定了最佳参数，对各种影响因素进行了研究。用实地含氟水样检验沸石除氟的可靠性。     

Defluoridation of drinking water using chemically modified bentonite clay

Adsorption potential of metal oxide (lanthanum, magnesium and manganese) incorporated bentonite clay was investigated for defluoridation of drinking water using batch equilibrium experiments to gain insight of adsorption behavior, kinetics and mechanisms of adsorption of fluoride ion. The effect of various physico-chemical parameters such as pH, adsorbent dose, initial fluoride concentration and the presence of interfering co-ions on adsorption of fluoride has been investigated. The 10%La-bentonite shows higher fluoride uptake capacity for defluoridation of drinking water as compared to Mg-bentonite, Mn-bentonite and bare bentonite clay. The uptake of fluoride in acidic pH was higher as compared to alkaline pH. The equilibrium adsorption data fitted reasonably well in both Langmuir and Freundlich isotherm models. It was also observed that in the presence of certain co-existing ions can have positive effect on removal of fluoride, while carbonate and bicarbonate anions show deleterious effect. The rate of adsorption was reasonably rapid and maximum fluoride uptake was attained within 30 min. The modified adsorbent material shows better fluoride removal properties for actual field water, which could be due to the positive effect of other co-ions present in the field water.     

Defluoridation of drinking water using a ceramic filter decorated with iron oxide-biochar composites

While effective defluoridation methods have been developed, most of them are expensive and difficult to apply at a household level. One safe, low-cost, decentralized water treatment method which is attracting research attention is the use of ceramic filters (CFs). Few studies have explored the use of biochar composites in CFs for defluoridation of water, with the bulk of them being based on batch and column experiments. The aim of this work was to develop, and evaluate a laboratory-scale, low-cost CF using clay, sawdust, and iron oxide-biochar (FBC) for fluoride removal in synthetic and real water samples. Three CFs were fabricated with varying FBC content (0%, 5%, and 10%). Water absorption, apparent porosity, and flow rate decreased with decreasing FBC content, while the impact strength increased with decreasing FBC content. The CFs reduced the fluoride concentration of both the ground water, and synthetic water to below the WHO recommended limit (1.5 mg/L). While further studies are required to optimize the CF, the results demonstrate that a CF decorated with FBC composites is effective for defluoridation of drinking water.     

Hybrid sorbent-ultrafiltration systems for fluoride removal from water

Fluoride contaminated water sources are found in many parts of the world and the consumption of such water is causing dental and skeletal fluorosis in humans, especially in developing countries. Hybrid sorbent-ultrafiltration (UF) systems are proposed for the removal of fluoride from water for the first time in this study. Laterite and bone char were selected as they are low cost, accessible sorbents in developing countries. The performances of the laterite-UF and bone char-UF systems were compared in terms of fluoride removal and membrane permeability under varying fluoride concentration, solution pH, and sorbent load. For equilibrium fluoride concentration of 1.5 mg/L, the World Health Organization guideline for safe drinking water, the sorption capacity of bone char (1.1 mg/g) was larger than that of laterite (0.40 mg/g) and this was attributed to the larger surface area of bone char. For the laterite-UF system, increase in fluoride concentration resulted in a decline in UF permeability whereas for the bone char-UF system there was no influence of fluoride concentration on membrane permeability. The optimal solution pH at which the systems are operated at maximum sorption capacity while avoiding membrane fouling was determined as pH 5-6 for the laterite-UF and pH 7 for the bone char-UF system. For both systems, the permeability declined in a similar manner as the sorbent load increased. Although both systems require further optimization, they showed to be viable defluoridation technologies.     

Preparation and characterization of red mud sintered porous materials for water defluoridation

This research was undertaken to characterize a porous material prepared from red mud and to investigate the capacity of zirconium hydroxide-modified red mud porous materials (Zr-modified RMPMs) for the removal of fluoride from aqueous solutions. An organic foam template was used for the preparation. After sintering, the RMPM had a porosity up to 80 % with the pore size controlled between 50 and 100 μm. Batch experiments were performed to study the defluoridation of water using Zr-modified RMPM under various experimental conditions. Kinetic data revealed that the equilibrium for fluoride removal was achieved within 60 min. The fluoride sorption process was well fitted to the pseudo-second-order rate kinetics and pore diffusion models. The optimum fluoride removal was observed between pH range 3 and 4 and the adsorption capacity for fluoride by Zr-modified RMPM was 0.6 mg/g. Results from this study demonstrated potential use of Zr-modified RMPM in defluoridation of drinking water.     

Defluoridation of Water Using Zirconium Impregnated Coconut Fiber Carbon

Abstract

In this study the applicability of Zirconium ion impregnated coconut fiber carbon (ZICFC) as an adsorbent for fluoride removal from water was investigated. The dependence of fluoride adsorption on the physicochemical properties includes pH, agitation time, adsorbent dosage, temperature, and the initial concentration of the adsorbate. Maximum defluoridation was obtained at an original pH value of 4.0 with a rapid 93% adsorption being achieved within 10 min of contact with ZICFC. Adsorption data for fluoride onto ZICFC were better correlated to the Langmuir isotherm and pseudo-second order chemical reaction provided the best fit for the experimental data as obtained from kinetic studies. A combination of chemisorption and physisorption processes in hand with intraparticle diffusion, account for the high defluoridation ability of ZICFC, with the thermodynamic parameters indicating an endothermic phenomenon. The fluoride adsorption capacity of ZICFC when compared with those of other commonly used fluoride adsorbents highlights the substantial improvement in fluoride adsorption capacity of coconut fiber carbon on zirconium impregnation.     

磁性羟基磷灰石的制备及其除氟性能研究

氟离子在饮用水中浓度超过1.0mg/L,将对人体健康造成极大危害.通过原位共沉淀法将具有磁性的四氧化三铁掺入羟基磷灰石(HAP)中制备磁性HAP.磁性HAP可通过普通磁体将其吸附并分离回收.实验结果表明,最佳的制备条件为反应温度和时间为60℃和1h,陈化温度和陈化时间为25℃和12h,四氧化三铁用量为0.08g.比较了HAP和磁性HAP对水溶液中氟离子的去除效果.Langmuir模型更适合于该体系,拟合得到最大吸附容量为13.70mg/g,说明磁性HAP对氟离子的吸附属于单层吸附.ΔG0<0和ΔH0>0表明该吸附过程为自发的吸热过程.吸附过程符合拟二级动力学.磁性HAP循环再生使用4次以上,仍能保持85％以上的除氟效率.高吸附容量和优异的循环使用性能表明磁性HAP是一种有效的、可重复使用的除氟吸附剂.     

Effect of cation doping on the structure of hydroxyapatite and the mechanism of defluoridation

The structure of three cation-doped hydroxyapatite filter materials with different cation radii and valence states, aluminum-doped hydroxyapatite (Al-HA), magnesium-doped hydroxyapatite (Mg-HA) and lanthanum-doped hydroxyapatite (La-HA), were studied to explore the performance and possible mechanism of defluoridation by means of Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscope (SEM)/Energy-dispersive X-ray spectroscopy (EDS), BET and Zeta potential analysis. The results demonstrated that cation doping with different radii could weaken lattice structure of hydroxyapatite, increase content of hydroxyl group and improve exchange ability with fluoride ions. However, the decisive factor affecting the capacity of fluoride removal was valence state of doped ion, because defluoridation capacity of Al-HA and La-HA with trivalent cations were larger than Mg-HA with bivalent cation. In addition, other studies related to the process of defluorination were carried out. The mechanism of defluoridation mainly included physical adsorption and chemical adsorption. First, F^- was deposited on the surface of the filter material by physical adsorption. After F^- diffused into the voids of the filter interval, and underwent ion exchange and complexation with -OH functional group in the lattice. Cation-doped hydroxyapatite structure and mechanism of fluoride removal were of great significance in the field of environmental governance.     

Enhanced and selective fluoride sorption on Ce(III) encapsulated chitosan polymeric matrix

Chitosan beads (CB) possesses low defluoridation capacity (DC) have been suitably modified by carboxylation followed by chelation with Ce(III) to enhance its DC. The carboxylated chitosan beads (CCB), which has a desirable DC of 1385 mgF^?/kg, has been further chemically modified by incorporating Ce³⁺ ion into CCB (Ce‐CCB) and its DC was found to be 4798 mgF^?/kg, whereas raw chitosan beads (CB) possesses 52 mgF^?/kg only. The maximum DC of Ce‐CCB was observed at pH 7 and showed selectivity toward fluoride in presence of other coanions. The sorbent was characterized using FTIR and SEM with EDAX analysis. The sorption data was fitted with Freundlich and Langmuir isotherms and kinetic models. The calculated thermodynamic parameters, viz., ΔG°, ΔH° and ΔS° indicate the nature of fluoride sorption. A field trial was carried out with fluoride water collected from a nearby fluoride‐endemic village to test the suitability of Ce‐CCB at field conditions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009