Studies on the recovery of uranium from nuclear industrial effluent using nanoporous silica adsorbent

In this paper, the sorption of uranium onto nanoporous silica adsorbent in the presence of nitrate, sulfate, chloride, fluoride and phosphate was studied. The effect of contact time between the nanoporous sorbent and aqueous solution, pH and initial concentration of uranium was also investigated. Uranium sorption onto nanoporous silica adsorbent is a very fast process as sorption rate increases with pH increment. Optimum pH for uranium sorption was 4?C8. Experimental sorption isotherm is successfully described by Langmuir and Freundlich models. The results obtained by batch experiments showed that the presence of high concentration of nitrate, sulfate, chloride and phosphate anions alone had no interference with uranium recovery. However, the presence of fluoride ions (>250?mg/L) decreases uranium sorption by about 55?%. The results also showed that the presence of phosphate ions (about 300?mg/L) in solution could remove fluoride interference completely. Finally, the efficiency of the nanoporous silica adsorbent for uranium recovery from wastewater of the uranium conversion facility was investigated.     

新型饮用水除氟吸附剂研究进展

吸附法是目前饮用水除氟应用最广泛的方法,而吸附剂的特性是决定除氟成本和效果的重要因素。将工农业废弃物、天然矿物及生物制剂作为除氟吸附剂,可简化吸附剂加工环节,减少环境污染,降低除氟成本。基于对国内外新型除氟吸附剂研究现状的介绍,提出新型饮用水除氟吸附剂的后续研究应侧重预处理和使用后的处置方法,以及工业化应用理论基础研究,以寻求经济、高效的治理工艺,早日大规模应用于饮用水水处理中。     

Geochemical Characters of Water Coproduced with Coalbed Gas and Shallow Groundwater in Liulin Coalfield of China

To reveal the geochemical characters of water coproduced with coalbed gas and shallow groundwater,water samples were collected from 12 wells of coalbed methane and 7 wells of shallow groundwater.The pH,CODMn,fCO2,total dissolved solids （TDS）,total hardness,and concentrations of metasilicic acid,sodium and kalium,calcium ion,magnesium ion,ammonium iron,bicarbonate ion,carbonate,chloride,sulfate ion,nitrate ion,fluoride,lithium,zinc,nickel,manganese,iron,boron,barium,etc.of the samples were measured.Research results showed the following：（1） Concentrations of TDS,chloride,fluoride,sodium and kalium,ammonium,iron,and barium in the water coproduced with coalbed gas exceeded the national standards of China; however,physical,chemical,and biological properties of shallow groundwater could meet the national standard.（2） The water produced from coalbed contained mainly Na-Cl·HCO3,with average TDS of 4588.5 ppm,whereas shallow groundwater contained a mixture of chemicals including Na.Mg.Ca-HCO3·SO4 and Na.Mg-HCO3·SO4,with average TDS of 663.8 ppm.（3） In general,it was observed that bicarbonate and sodium accumulated in a reducing environment and deeper system,while depletion of hydrogen ions and dissolution of sulfate,calcium,and magnesium occurred in a redox environment and shallow system.（4） Sodium and kalium,ammonium,chloride,and bicarbonate ions were the main ions found in the study area.     

Fluoride pollution in soils and waters of Koohbanan region, southeastern Iran

Dental fluorosis occurs because of fluoride over-absorption during tooth calcification and maturation. We studied fluoride concentration in water and soil samples of the Koohbanan region in Kerman province of southeastern Iran and the effects of calcium chloride and gypsum treatments in decreasing the amount of fluoride in water samples of this region. The results indicate that the high amount of fluoride in the water samples of Koohbanan region is not in agreement with the recommended amount of fluoride concentration for drinking water by World Health Organization (that is 1–1/5 mg/l). Applying calcium chloride and gypsum treatments decreased the amount of fluoride in the water samples showing that utilizing calcium chloride (6 mg/l) or gypsum (12 mg/l) can lower the fluoride concentration in the water samples of Koohbanan, and thus solve the observed dental fluorosis problem.     

巯基棉富集—大口径毛细管气相色谱法测定水样中痕量烷基汞

介绍了巯基棉富集-大口径毛细管柱气相色谱法测定环境水中痕量烷基汞的分析方法,并与玻璃填充柱色谱分离烷基汞进行了对比。取1000ml环境水样时,本法的检出限为:甲基汞(MMC)0.5pg;乙基汞(EMC)0.7pg。     

Preliminary investigations on the defluoridation of water using fired clay chips

The adsorption of fluoride ions on ground fired clay pot has been investigated. The maximum efficiency of the adsorbent for defluoridating 1–2 litres of water was found to be 200 mg fluoride kg⁻¹ adsorbent. The investigation showed that 5–20 mg l⁻¹ fluoride, from 1 litre of water, could be reduced to less than 1.5 mg l⁻¹ using 120–240 g of the adsorbing medium. The effects of the dose of the medium, the pH, the contact time and the initial fluoride content were studied in relation to defluoridation efficiency. Comparison of fluoride removal capacity of the adsorbent was also made with those of fired brick, clay soil and red ash. The latter exhibited practically no adsorption. A packed column of the same ground clay pot was saturated with 285 mg fluoride kg⁻¹ of adsorbent when 20 litres of water containing 10 mg l⁻¹ F was allowed to pass through it. This column defluoridated 6 litres of tap water containing 10 ppm F⁻ to below 1.5 mg l⁻¹.     

Geochemical characteristics of fluoride in groundwater of Gimcheon, Korea: lithogenic and agricultural origins

The occurrence of fluoride in groundwaters can be influenced by many factors. In Korea, the fluoride-rich groundwaters are normally associated with rock types, especially granite and gneiss. In Gimcheon, high-fluoride groundwaters (up to a maximum of 2.15 mg/L) were observed with bimodal distribution of concentrations. The groundwater in this area showed relatively high concentrations of anthropogenic chemicals such as nitrate, chloride, and sulfate. Statistical analysis showed that fluoride is positively correlated with pH, alkalinity, sodium, and lithium, indicating that the interaction with granite is the main cause enriching its concentration. In Gimcheon, δ¹⁸O data of groundwater showed a negative correlation with nitrate and can be used as an indicator of groundwater age. The four samples of fluoride-rich groundwater were plotted in the light δD and δ¹⁸O region, showing that they were the result of long water–rock reaction. However, other groundwater with a low-fluoride concentration was evenly distributed throughout all δD and δ¹⁸O ranges and did not show a statistically significant correlation with nitrate, indicating possible mixing with another source of fluoride. Considering the influence from the surface on the geochemical characteristics of groundwater in this area, anthropogenic sources including phosphate fertilizer containing fluoride and pesticides may also have partly contributed to the concentrations of fluoride in the low-fluoride groundwater. The scattered distribution of fluoride-rich groundwater and the significant correlation with lithium suggest that pegmatite is the main rock type increasing fluoride concentration in this area.     

Health risk assessment of fluoride with other parameters in ground water of Sikar city (India)

Geochemical processes are identified as controlling factors of groundwater chemistry, including chemical leaching and fluoride contaminations. These geochemical processes are identified using characterization of the major physico-chemical parameters of ground water from northern part of Sikar city. For this purpose, 15 ground water samples have collected and analyzed for different water quality parameters, such as pH, EC, TDS, TH, TA, DO, calcium, magnesium, sodium, potassium, carbonate, bicarbonate, chloride, nitrate, sulfate and fluoride with the help of standard methods recommended by American Public Health Association. The analysis indicated that fluoride concentrations in four samples are at alarming state as compared to the World Health Organization standards for drinking purposes, thereby suggesting the need for treatment and precautionary measures for use of the particular ground water. The increased fluoride level in the ground water of Sikar city is due to the some geological process such as dissolution of fluoride rich mineral (fluorspar) in the favorable environment. To classify the ground water ability for different purposes various graphical plots like Piper tri-linear, Durov, Schoeller, Bar, Scatter diagrams have been drawn. On the basis of physico-chemical, graphical and statistical analysis (Spearman’s Rank correlations), various dimension of improving water quality for drinking purposes have also been suggested.     

Adsorptive separation of Pb(II) and Cu(II) from aqueous solutions using as-prepared carboxymethylated waste Lyocell fiber

Adsorptive separation of Pb(II) and Cu(II) using modified waste Lyocell fiber adsorbent was investigated in this research. The waste Lyocell fiber was functionalized through carboxymethylation of the hydroxyl moieties using sodium chloroacetate as modifying agent and was crosslinked with epichlorohydrin to provide water stability. The maximum equilibrium batch uptake in single metal system was 353.45 mg/g for Pb(II) and 98.33 mg/g for Cu(II), according to the Langmuir isotherm model. The adsorption rates were very fast and reached equilibrium within 3 and 5?10 min for Cu(II) and Pb(II), respectively. In competitive binary metal system, the uptake of Cu(II) largely decreased to 38.40 mg/g, and Pb(II) selectivity was observed. Elemental and functional characterization suggested that the adsorption proceeded by ion exchange between the adsorbent and metal ions. In a flow-through column system, adsorption followed by desorption aided in effectively eluting ~260 mg of Pb(II) (out of ~300 mg total adsorbed) from the Pb(II)–Cu(II) binary solution. Finally, the adsorbent was very effective in four successive adsorption–desorption cycles with over 99 % uptake and 94 % desorption efficiencies. The present study may provide an alternative option for waste fiber recycling and could be useful in recovering heavy metal ions from aqueous sources to complement their depleting reserves.     

Removal of textile dyes from aqueous solution by conducting polymer modified clinoptilolite

In this work, clinoptilolite was modified with conducting polyaniline polymer and then the nanocomposite was used as an adsorbent for methyl orange (MO) as a model dye. Cations located in clinoptilolite structure like Na⁺, K⁺, Mg²⁺, Ca²⁺ were exchanged with anilinium cations and then the polymerization of anilinium cations in and outside of the clinoptilolite channels resulted in the formation of polyaniline/clinoptilolite nanocomposite. The resulted nanocomposite was used for the removal of MO from aqueous solution. The effect of various factors like contact time, concentration of dye as well as the amount of adsorbent on the removal efficiency of dye was investigated. The adsorption isotherms were investigated. It was found that the equilibrium adsorption data were well described by the Langmuir isotherm model. The kinetic studies indicated that the adsorption process was controlled by pseudo-second-order equation. High adsorption capacity and low contact time as well as the low cost of modified clinoptilolite proved that it is an efficient adsorbent for the removal of MO from aqueous solutions.     

Empirical and mechanistic evaluation of sodium exchange isotherms on natural mineral and organic adsorbents and organically functionalized nanoparticles

This study was conducted to evaluate the efficiency of low-cost adsorbents including bentonite, kaolinite and zeolite saturated with calcium and potassium, potato and wheat residues, and three metal oxide nanoparticles functionalized with an acidic extract of potato residues in improving the quality of sodic waters. The optimization of factors such as pH, contact time, and adsorbent dosage was investigated using a solution containing sodium, calcium, magnesium, and potassium. The optimal pH and contact time were 7.0 and 24 h, respectively. The optimal dosage for using functionalized nanoparticles was 0.1 g and for using other adsorbents was 1.0 g. The sodium exchange isotherms were conducted in binary sodium–calcium and sodium–potassium and quaternary sodium–calcium–magnesium–potassium systems. Zeolite saturated with potassium was the most effective adsorbent in removing sodium from aqueous solutions with an average removal efficiency of 69.2 and 66.5 % in binary and quaternary systems, respectively. Freundlich and Langmuir equations fitted well to experimental data in both binary and quaternary systems. Cation selectivity coefficients calculated based on the Gaines–Thomas convention varied with changing pH and adsorbent dosage. Graphical and statistical evaluations confirmed that the mechanistic cation exchange model using average Gaines–Thomas selectivity coefficients in geochemical PHREEQC program was able to successfully simulate the sodium exchange on different adsorbents in both systems. The Gaines–Thomas selectivity coefficient values greater than unity and as a consequence, the negative values of the Gibbs free energy change of adsorption indicated that sodium exchange reactions in the presence of different adsorbents used is this study were exergonic and spontaneous.     

西北地区地下水质量评价

本文以地下水调查的水质分析资料和动态监测资料为基础,参照我国地下水质量标准和生活饮用水卫生标准,对西北地区地下水质量状况进行综合评价。结果表明西北地区地下水质量状况为全国较差的地区,不可直接利用的地下水多分布于该区内陆盆地中心地带;地下水污染多发生在主要城市、工矿企业及其周边地区,水污染主要呈点状、线状分布,主要超标项目为溶解性总固体、总硬度、硝酸盐、亚硝酸盐、硫酸盐、氯化物和氟化物等。     

Stability of earth dam contaminated by chemical transport

When chemicals are introduced into the oil, they affect soil properties such as hydraulic conductivity and stress–strain behavior. In this study, several chloride concentrations are varied from 0 to 20 per cent to analyse the effect of chemicals on soil properties. A series of laboratory triaxial tests are performed on the cylindrical specimens of sand–bentonite mixture with different sodium chloride contents (5, 10, 15 per cent) by Nannapaneni. Deformation (elastic modulus, E) and strength (cohesion, c′, and angle of friction, ϕ′) parameters are obtained from the triaxial tests as functions of confining pressure and sodium chloride concentrations, and variations of parameters are incorporated into stability analysis. The stress–strain–strength behaviour based on the above strength parameters is introduced in a finite element procedure with a modified residual flow procedure (RFP). By integrating a slope stability procedure in the finite element method, the stability with time of earth dam contaminated by sodium chloride is examined. It is found that increasing sodium chloride concentration for the soil considered increases stability. However, the procedure is general and can allow stability analysis under the influence of other chemical which may lead to decrease in stability. Copyright © 1999 John Wiley & Sons, Ltd.     

地下水和土壤中不同形态碘的分离测定

实验选用717强碱型阴离子树脂吸附溶液中的碘离子和碘酸根,用30g/L氯化钠溶液和2.0mol/L硝酸钠溶液先后从树脂上洗脱碘酸根和碘离子,达到不同形态碘分离的目的。洗脱液用碘-淀粉比色法测定碘的含量。方法已用于我国高碘地区地下水和土壤样品中不同形态碘的分析。     

Evaluating the effectiveness of a hybrid sorbent resin in removing fluoride from water

In some regions of the world, the concentration of fluoride in groundwater is high. To reduce the amount of fluoride to acceptable drinking water standard, it is highly recommended to treat the water. Fluoride adsorption in aqueous solution by a hybrid resin was studied in this research because of its functional groups likeness with goethite. Kinetic data showed that F adsorption was rapid in the beginning and maximum uptake occurred in within 10 min and equilibrium reached within 100 min. The experimental results showed that fluoride adsorption was influenced by pH of solution and optimum operating pH was in the range of 3 to 5.5. Langmuir model was applicable to the present study and F ions were exchanged with hydroxide ions in nano-scaled structure on the surface of sorbent. This adsorbent with 61 % efficiency is suitable for the regions where F concentration is less than 4 mg/L.     

不同茶园茶叶氟含量及土壤氟的形态分布

通过对我国中西南产茶区12个茶园土壤样品和茶叶样品的采集,探讨了不同茶园茶叶氟含量和茶园土壤氟的形态分布规律。老叶和嫩叶氟含量分别为221～1 504 mg/kg和49.0～602 mg/kg,老叶氟含量是嫩叶的2.5～8.1倍。各形态氟含量随土壤层次加深没有统一变化规律,但各层土壤不同形态氟含量均为残渣态铁锰氧化物态＞有机结合态＞水溶态＞交换态。土壤pH值、有机质含量和阳离子交换量对茶园土壤氟的形态分布有不同程度的影响。老叶和嫩叶氟含量随水溶态氟含量的增加均呈显著增加趋势,但与其他形态氟含量没有显著的相关关系。     

An occurrence of marsh gas in deccan traps (Basalt) in central India

During the course of groundwater exploration in the upper catchment of Betwa River basin in Madhya Pradesh, Central India, marsh gas at a depth of 171.33 m below ground level (bgl) has been observed bubbling out of the flowing water. The results of gas analysis reveal the presence of 88% methane and 2.08% helium. Water is of sodium chloride type and possesses a high concentration of fluoride and low concentrations of nitrate and sulphate. Tritium analysis of deep groundwater indicates a value of 2.8 T.U., indicating pre-1953 storage with possible traces of modern contamination, which may have been introduced during well construction. It is believed that an occurrence of marsh gas in Deccan Traps has not been reported earlier.     

利用高铝粉煤灰制备氢氧化铝的实验

以无水碳酸钠为助剂,分解高铝粉煤灰中的莫来石和铝硅酸盐玻璃相。经中温烧结、酸浸使硅铝分离,调节pH值为5～6纯化含铝滤液,通入CO₂气体酸化等工序,可制备氢氧化铝粉体。采用X射线粉末衍射、扫描电镜、化学分析方法对制品进行表征,结果表明：制备的氢氧化铝为球形颗粒,其粒径为200 nm左右,性能达到GB/T4294-1997的三级标准。实验所采用的工艺路线是高铝粉煤灰资源化高效利用的有效途径之一。     

Assessment of groundwater quality with special emphasis on fluoride contamination in crystalline bed rock aquifers of Mettur region, Tamilnadu, India

Groundwater samples were collected from Mettur taluk of Salem district, Tamilnadu, India for two different seasons (pre-monsoon and post-monsoon) and analyzed for fluoride ion along with other chemical parameters. The major litho units of the study area are Charnockites, peninsular gneiss, and calc gneiss of meta-sedimentary group. The fluoride concentration ranges from 0.1 to 2.8?mg/L and 0.4 to 4.0?mg/L during pre-monsoon (PRM) and post-monsoon (POM) seasons, respectively. Results showed that collected water samples were contaminated by the presence of fluoride ion. During PRM and POM, 21% and 56% of samples recorded higher fluoride when compared with Indian Drinking Water Standard (1?mg/L) and (9% and 35%) of samples recorded higher fluoride when compared with World Health Organization tolerance limit (1.5?mg/L). The ratio of Na/Ca indicates high sodium content in groundwater enhances the dissolution of fluoride at higher pH. Hydrogeochemical facies indicates water-rock interaction as main source for high fluoride in groundwater. A positive correlation between pH, Mg, and F indicates high alkaline nature of water promotes fluoride leaching from source rocks into ground water. Factor analysis indicates hydro-geochemical processes like weathering, ion exchange, and anthropogenic contributes to groundwater chemistry. The saturation index indicates dissolution and precipitation contributes fluoride dissolution along with mixing.     

复方化学消毒剂中苯扎氯铵的高效液相色谱测定

建立了一种测定复方化学消毒剂中苯扎氯铵成分十二烷基二甲基苄基氯化铵、十四烷基二甲基苄基氯化铵和十六烷基二甲基苄基氯化铵的反相离子对高效液相色谱法。色谱柱为Platisil ODS(5μm,250 mm×4.6mm),流动相为甲醇-0.2 mol/L己烷磺酸钠(含1%三乙胺,V/V,用高氯酸调节至pH=6.0,体积比85∶15),紫外220 nm检测。用己烷磺酸钠作为离子对试剂,增强了苯扎氯铵成分的保留,三乙胺作为扫尾剂,通过抑制固定相表面残存的硅羟基对苯扎氯铵成分的吸附,减少了色谱峰拖尾。3种苯扎氯铵成分分离良好,标准曲线的线性范围分别为0.002～5 mg/mL、0.005～10 mg/mL和0.005～10 mg/mL,检测限分别为0.0005 mg/mL、0.001mg/mL和0.001 mg/mL。方法具有良好的准确度和精密度,在测定低浓度样品时优势明显。实际用于测定苯扎氯铵消毒液和医用消毒纸巾中3种苯扎氯铵成分的含量,回收率为99.3%～104.1%,日内和日间测定相对标准偏差(RSD)均小于2.0%。