大学化学实验用氟离子选择电极的再生处理研究

本文介绍了氟离子选择电极使用性能的判断方法,对报废氟离子选择电极的敏感膜、内参比溶液和内参比电极进行更换或再生处理,再生处理后的电极性能接近正常电极的测定性能,可以满足实验测定需要,成功实现了报废氟离子选择电极的再生。     

电吸附法去除地下水中离子的试验研究

基于双电层理论的电吸附方法是近年来发展起来的一种新型的去除水中离子的方法。采用新型电吸附设备处理清华大学地下水的试验结果表明，电吸附方法可以有效去除水中的离子，去除效果取决于电压、流量、电极对数等参数。当电压为1．55V、流量为40L／h、采用100对电极时，出水电导率为30～50μS／cm，硬度可由278．3mg／L(以CaCO3计)降低到20．3mg／L，再生时间与运行时间之比为1：3．6。     

改性沸石脱氟剂去除水中氟离子的实验研究

研究了用三氯化铁改性的沸石在水中的除氟性能 ,对使用条件及除氟机理进行了研究。并对洗脱、再生后的吸附剂进行了再吸附实验。结果表明 ,该吸附剂对含氟水中的氟具有吸附容量高、速度快、选择性高、易洗脱再生的特性。多次洗脱再生后的吸附剂可重复使用 ,吸附剂性能稳定 ,机械强度高。该 F-吸附剂的静态饱和吸附容量可达 2 6.5 7mg/g。     

氟离子选择性电极测定水泥及其原料中的总氟量

介绍用氟离子选择性电极测定水泥及其原料中的总氟量的具体方法和注意事项。     

预处理/树脂吸附/电极氧化工艺处理氟苯生产废水

采用混凝沉淀/电聚浮除(EPN)/树脂吸附/电极氧化工艺处理江苏省某化工厂的氟苯生产废水,经过3个多月的试运行,树脂吸附速度控制在2 BV/h,用8%-10%的氢氧化钠溶液脱附,脱附速度控制在0.5 BV/h,树脂脱附率>99%.工程验收监测结果表明,系统出水水质达到<江苏省化学工业主要水污染物排放标准>(DB 32/939-2006)的二级标准和<污水综合排放标准>(GB 8978-1996)的二级标准.     

载铁硅胶去除水中氟的吸附性能与机理

报道了载铁硅胶的制备及其在含氟水中的吸附除氟性能 ,提出了一种新的配体交换固液分离、深度除氟材料。实验研究了该种分离材料在高氟水中的除氟效率和条件 ,结果表明 ,在含氟30～ 40 mg/L左右的水中 ,除氟率高达 99.5 0 %以上 ,可使水中氟含量降至 0 .0 1 mg/L以下。经测定 ,载铁硅胶对氟的静态饱和吸附容量可达 7.99mg/g。水中常见共存离子对氟的吸附率无影响 ,表现出该种材料对氟吸附的高度选择性。得到了一种对含氟地下水和工业氟污染水的效果显著的除氟方法。     

氟离子选择性电极测定水泥及其原料中的总氟量

本文详细介绍了用氟离子选择性电极测定水泥及其原料中总氟量的具体方法和注意事项。     

锌铝电极电絮凝法处理高氟饮用水的研究

在双铝极板电絮凝法的基础上引入锌电极,考察锌铝电极电絮凝法对高氟饮用水的除氟效果.静态试验结果表明,采用锌铝电极可以有效降低水中的氟离子浓度,对CODMn和浊度的去除效果优于双铝电极;当原水的氟离子浓度为6 mg/L时,最佳处理条件:锌、铝极板比为1:3、电解电压为18 V、反应pH值为6、反应时间为25～30 min.动态试验结果表明,当进水流量和氟离子浓度分别高达42 mL/min、8 ms/L时,调节进水pH值为6可使其出水中的氟离子浓度达标.     

改进离子色谱法测定水中氟含量

离子色谱法测定水中氟离子含量,由于水中负峰的干扰,会存在较大偏差,通过在样品中添加淋洗液,可消除水的负峰,使测定结果更准确可靠。     

氟化钙及氟离子测定方法

分析掌握氟化钙及氟离子测定方法的必要性。介绍萤石中氟化钙测定方法,水泥生、熟料中氟离子的测定方法。     

改性沸石处理含氟水的试验研究

用氧化铝改性沸石制备了一种除氟材料,其最佳制备工艺参数为:在200℃下焙烧1.5 h对沸石进行预处理的基础上,用pH=9的Al(OH)3悬浮液对沸石进行覆盖沉淀改性,并在400 ℃下焙烧1 h涂层,最后用质量分数为4%的Al2(SO4)3溶液浸渍12 h.改性后的沸石对氟离子的吸附量可达0.84 mg/g.改性前后除氟性能的对比试验结果表明,活性氧化铝成分与氟离子的络合作用对氟的去除起主要作用.     

饮用水除氟技术的现状及进展

基于近年来除氟方法的研究进展，综述了近年来国内饮用水除氟方法，如混凝沉降法、吸附法、电凝聚法、电渗析法、反渗透法、离子交换法等，同时讨论了各种除氟方法的机理及进展，以促进饮用水除氟技术的发展。     

除氟磷改性沸石活化条件研究

考察了沸石的预处理、浸泡时间、固液比及改性沸石的干燥温度等活化条件对氟化物处理效果的影响,得到改性沸石的最佳制备情况：在600℃下充分焙烧2h,沸石和磷酸的反应时间为12h,磷酸和沸石的液固比为10：1,磷改性沸石制得后自然风干,可制得除氟率86％的磷改性沸石。     

Electrochemical removal of fluoride from water by PAOA-modified carbon felt electrodes in a continuous flow reactor

A novel poly(aniline-co-o-aminophenol) (PAOA) modified carbon felt electrode reactor was designed and investigated for fluoride removal from aqueous solutions. This reactor design is innovative because it operates under a wider pH range because of coating with a copolymer PAOA ion exchange film. In addition, contaminant mass transfer from bulk solution to the electrode surface is enhanced by the porous carbon felt as an electron-conducting carrier material compared to other reactors. The electrically controlled anion exchange mechanism was investigated by X-ray photoelectron spectroscopy and cyclic voltammetry. The applicability of the reactor in the field was tested through a series of continuous flow experiments. When the flow rate and initial fluoride concentration were increased, the breakthrough curve became sharper, which lead to a decrease in the breakthrough time and the defluoridation capacity of the reactor. The terminal potential values largely influenced fluoride removal by the reactor and the optimal defluoridation efficiency was observed at around 1.2 V. The breakthrough capacities were all >10 mg/g over a wide pH range (pH 5-9) with an initial fluoride concentration of 10 mg/L. Consecutive treatment-regeneration studies over a week (once each day) revealed that the PAOA-modified carbon felt electrode could be effectively regenerated for reuse. The PAOA-modified carbon felt electrode reactor is a promising system that could be made commercially available for fluoride removal from aqueous solutions in field applications.     

Determining the optimal fluoride concentration in drinking water for fluoride endemic regions in South India

Fluoride ion in drinking water is known for both beneficial and detrimental effects on health. The prevalence of fluorosis is mainly due to the intake of large quantities of fluoride through drinking water owing to more than 90% bioavailability. The objective of this study is to predict optimal fluoride level in drinking water for fluoride endemic regions by comprising the levels of fluoride and other water quality parameters in drinking water, prevalence of fluorosis, fluoride intake through water, food and beverages such as tea and coffee and also considering the progressive accumulation of fluoride in animal bones, by comparing with non fluoride endemic areas comprise of the same geological features with the aid of regression analysis. Result of this study shows that increase of fluoride level above 1.33 mg/l in drinking water increases the community fluorosis index (CFI) value more than 0.6, an optimum index value above which fluorosis is considered to be a public health problem. Regression plot between water fluoride and bone fluoride levels indicates that, every increase of 0.5 mg/l unit of water fluoride level increases the bone fluoride level of 52 mg/kg unit within 2 to 3 years. Furthermore, the consumption of drinking water containing more than 0.65 mg/l of fluoride can raise the total fluoride intake per day more than 4 mg, which is the optimum fluoride dose level recommended for adults by the Agency for Toxic Substances and Disease Registry. From the result, the people in fluoride endemic areas in South India are advised to consume drinking water with fluoride level within the limit of 0.5 to 0.65 mg/l to avoid further fluorosis risk.     

The impact of ferrous ion reduction of chlorite ion on drinking water process performance

The use of chlorine dioxide (ClO₂) as a primary disinfectant and pre-oxidant in drinking water treatment is being explored as an alternative to chlorine for reducing disinfection by-product formation and to assure compliance with United States Environmental Protection Agency's Stage 1 Disinfection/Disinfection By-Products Rule. However, the ClO₂ by-product chlorite ion (ClO₂⁻) is also regulated by the same regulation. Ferrous iron (Fe(II)) has been shown to effectively reduce chlorite ion to chloride ion (Cl⁻) and this study was conducted to evaluate the impact on overall treatment process performance due to the ferric hydroxide solids that form from the reaction. Ferrous iron application was explored at three different points in a pilot-scale water treatment system: pre-rapid mix, pre-settling and pre-filter. Chlorite ion concentrations were effectively reduced from 2 mg/L to less than 0.3 mg/L using an Fe(II) dose of approximately 6 mg/L for all trials. Fe(II) addition at the rapid mix caused no adverse effects and, in fact, allowed for reduction of the alum dose due to the newly formed ferric hydroxide acting as a supplemental coagulant. An increase of 241 and 247% of total suspended solids influent to the filter process was observed when Fe(II) was applied at the pre-settling and pre-filter locations. Pilot-scale filter runs during these trials were less than 2 h and never obtained true steady state conditions. Jar testing was performed to better understand the nature of the ferric hydroxide solids that are formed when Fe(II) was oxidized to Fe(III) and to explore the effectiveness of Fe(II) addition at intermediate stages in the flocculation process.     

Performance of granular zirconium-iron oxide in the removal of fluoride from drinking water

In this study, a granular zirconium-iron oxide (GZI) was successfully prepared using the extrusion method, and its defluoridation performance was systematically evaluated. The GZI was composed of amorphous and nano-scale oxide particles. The Zr and Fe were evenly distributed on its surface, with a Zr/Fe molar ratio of ∼2.3. The granular adsorbent was porous with high permeability potential. Moreover, it had excellent mechanical stability and high crushing strength, which ensured less material breakage and mass loss in practical use. In batch tests, the GZI showed a high adsorption capacity of 9.80 mg/g under an equilibrium concentration of 10 mg/L at pH 7.0, which outperformed many other reported granular adsorbents. The GZI performed well over a wide pH range, of 3.5-8.0, and especially well at pH 6.0-8.0, which was the preferred range for actual application. Fluoride adsorption on GZI followed pseudo-second-order kinetics and could be well described by the Freundlich equilibrium model. With the exception of HCO₃⁻, other co-existing anions and HA did not evidently inhibit fluoride removal by GZI when considering their real concentrations in natural groundwater, which showed that GZI had a high selectivity for fluoride. In column tests using real groundwater as influent, about 370, 239 and 128 bed volumes (BVs) of groundwater were treated before breakthrough was reached under space velocities (SVs) of 0.5, 1 and 3 h⁻¹, respectively. Additionally, the toxicity characteristic leaching procedure (TCLP) results suggested that the spent GZI was inert and could be safely disposed of in landfill. In conclusion, this granular adsorbent showed high potential for fluoride removal from real groundwater, due to its high performance and physical-chemical properties.     

氟化物在我国饮用水水源和饮用水中的分布调查及健康影响

综述了氟化物和人体健康的关系，以及世界各国和地区饮用水中氟化物浓度标准限值的规定，分析了我国不同类型、不同地区、不同流域的水源水和出厂水中的氟化物浓度的分布、超标、超检（检出并超过标准值的50％）和检出情况，并针对这些分析结果提出了关于标准限值的修订及今后进一步研究的方向。     

Effects of water chemistry on arsenic removal from drinking water by electrocoagulation

Exposure to arsenic through drinking water poses a threat to human health. Electrocoagulation is a water treatment technology that involves electrolytic oxidation of anode materials and in-situ generation of coagulant. The electrochemical generation of coagulant is an alternative to using chemical coagulants, and the process can also oxidize As(III) to As(V). Batch electrocoagulation experiments were performed in the laboratory using iron electrodes. The experiments quantified the effects of pH, initial arsenic concentration and oxidation state, and concentrations of dissolved phosphate, silica and sulfate on the rate and extent of arsenic removal. The iron generated during electrocoagulation precipitated as lepidocrocite (γ-FeOOH), except when dissolved silica was present, and arsenic was removed by adsorption to the lepidocrocite. Arsenic removal was slower at higher pH. When solutions initially contained As(III), a portion of the As(III) was oxidized to As(V) during electrocoagulation. As(V) removal was faster than As(III) removal. The presence of 1 and 4 mg/L phosphate inhibited arsenic removal, while the presence of 5 and 20 mg/L silica or 10 and 50 mg/L sulfate had no significant effect on arsenic removal. For most conditions examined in this study, over 99.9% arsenic removal efficiency was achieved. Electrocoagulation was also highly effective at removing arsenic from drinking water in field trials conducted in a village in Eastern India. By using operation times long enough to produce sufficient iron oxide for removal of both phosphate and arsenate, the performance of the systems in field trials was not inhibited by high phosphate concentrations.