分散式饮水中三价砷的去除

在利用硫酸铁去除五价砷 [As(V) ]的基础上研究了三价砷 [As(III) ]的氧化及去除 ,以寻求适合于分散式饮水中 As(III)的氧化方法。结果显示 :水中 As(III)的自然氧化过程相当缓慢 ,曝气 2 4h亦难以加速其氧化 ;通入臭氧 6 0 s,或按 7.5 m l/ L 投加双氧水 ,按投氯量加 2 .5 m g/ L 次氯酸钠或 15 m g/ L 的漂白粉等 ,均可有效氧化 1.0 m g/ L As(III) ,使砷去除率近似于 As(V)的去除率 ;选取次氯酸钠作为氧化剂 ,进一步研究发现其氧化效果不受水质 p H值、硬度、As(III)初浓度、As(III) / As(V)的配比等的影响 ,而且 1.2 5 m g/L 投加量可有效氧化≤ 0 .8mg/ L 的 As(III) ,现场实验亦证实了其氧化效果。本研究结果表明 ,次氯酸钠是一种效果可靠、经济技术可行的分散式饮水三价砷的氧化剂。     

Geosorption of As(III) from Aqueous Solution by Red Clays: Kinetic Studies

The geosorption of As(III) on red clays from aqueous solution under different environmental conditions (i.e. initial concentration, pH and temperature) was studied. This process reached its equilibrium quickly (<120 min). A decrease of the percentage of adsorption was caused when the initial concentration was increased (0.1–10 mg As(III) L^?1), in all the experimental pH levels (4–10). The optimal pH value for adsorption on red clays at 0.1 mg As(III) L^?1 was 10, while for 10 mg As(III) L^?1 was 4. There wasn’t a significant effect of temperature on the As(III) adsorption. The kinetic pseudo-second order and the isothermal Langmuir were the models that best described the experimental data, suggesting an adsorption process in multistep. Likewise, there are not interactions between neighbor active sites on the red clay surface.     

Arsenic Remediation from Drinking Water Using Fenton’s Reagent with Slow Sand Filter

This paper describes the development of a remediation approach based on the pre-oxidation using Fenton’s reagent and the subsequent removal of arsenic (As) through sand filtration from drinking water. The efficiency of the process was carried out including As(III) and As(V) with various concentration ratios up to 3,000 ppb. Efficient removal of As was observed within WHO guideline value of 10 ppb. The recoveries of samples were found to be 98 % ± 2.5 %. The process was applied to field samples, where results show considerable reduction in As concentrations. This process is cost effective for treatment of drinking water with high concentration of As.     

Adsorption of arsenic on flyash

Studies on removal of AS(III) by adsorption on flyash and activated carbon powder have been carried out at room temperature (30 +/- 1 degrees C). The adsorption isotherm of AS(III) on flyash and activated carbon powder was obtained in a batch reactor. Various parameters such as pH, initial concentraction of adsorbate and absorbent dose were studied. The experimental adsorption data fitted reasonably well to the Langmuir and Freunlich isotherms for both the adsorbents. Activated carbon has been observed to have greater adsorptive capacity than flyash.     

对混凝沉淀法分散式饮水除砷的研究

采用混凝沉淀法进行分散式饮水除砷试验。结果表明,当水样中五价砷［Ａｓ（Ⅴ）］含量为１．０ｍ ｇ／Ｌ时,不调节ｐＨ值（ｐＨ７．８２）,直接投加５０ｍ ｇ／Ｌ硫酸铁,室温下沉淀静置１２ｈ,可使倾析液残留砷含量低于０．０５ｍ ｇ／Ｌ。如沉淀反应后静置３０～４０ ｍ ｉｎ 即过滤,则只需投加３０ｍ ｇ／Ｌ的硫酸铁或４０ｍ ｇ／Ｌ的硫酸铝即可达到同样的除砷效果。随着投加量的增加,２种混凝剂对砷的去除率均升高,当水样Ａｓ（Ⅴ）≤１．０ｍ ｇ／Ｌ和≤０．５ｍ ｇ／Ｌ时,分别投加３０ｍ ｇ／Ｌ 硫酸铁和硫酸铝,过滤后可使残留砷含量达到现行饮水卫生标准（＜０．０５ｍ ｇ／Ｌ）。在水样处于不同ｐＨ 值、水温、浊度、硬度等条件下硫酸铁的除砷性能较硫酸铝稳定。一般情况下,沉渣中的砷不会再次进入水中     

活性氧化铝滤层吸附法饮水除砷现场半生产性试验研究

本文研究了现场饮水除砷及再生废水处理的工艺。用稀酸将原水pH降至6.0～6.5,再通过一个充填粒径为0.35～1.20mm、厚度为750mm的活性氧化铝滤罐。进水平均砷浓度为0.34～0.53mg/L,出水的平均砷浓度为0.014～0.028mg/L,平均除砷效率为94.7～95.9％。周期单位产水量≥4360m~3水/T·Al_2O_3。每立方米水的处理费用(包括化学品、滤料补充、废水处理)仅0.076元,低于饮水除氟的费用。强碱性含砷废水经中和及氯化铁混凝沉淀3天后,上清液中砷浓度降至0.009mg/L(远远低于0.5mg/L的排放标准),完全可以排放。     

纳米二氧化钛吸附分离-原子荧光光谱法进行水中无机砷的形态分析

目的:建立新颖、准确、可靠的水中无机砷的形态分析方法。方法:利用纳米二氧化钛在不同pH值溶液中对As(Ⅲ)、As(V)吸附能力的差异,调节溶液pH值,可实现As(Ⅲ)、As(V)的分离测定。结果:As(Ⅲ)在pH1-pH12范围内可被纳米二氧化钛完全吸附,As(V)在pH12的溶液中完全不吸附,用浓NaOH溶液调节溶液pH值为12,被纳米二氧化钛吸附的As(Ⅲ)在40 g/L NaOH溶液的洗脱下完全解吸附,可完成As(Ⅲ)的测定。总砷与As(Ⅲ)的差值即为As(V)含量。结论:纳米二氧化钛吸附分离结合原子荧光光谱法进行水中无机砷的形态分析,可得到满意的结果。     

Urinary arsenic species, toenail arsenic, and arsenic intake estimates in a Michigan population with low levels of arsenic in drinking water

The large disparity between arsenic concentrations in drinking water and urine remains unexplained. This study aims to evaluate predictors of urinary arsenic in a population exposed to low concentrations (≤50?μg/l) of arsenic in drinking water. Urine and drinking water samples were collected from a subsample (n=343) of a population enrolled in a bladder cancer case-control study in southeastern Michigan. Total arsenic in water and arsenic species in urine were determined using ICP-MS: arsenobetaine (AsB), arsenite (As[III]), arsenate (As[V]), methylarsenic acid (MMA[V]), and dimethylarsenic acid (DMA[V]). The sum of As[III], As[V], MMA[V], and DMA[V] was denoted as SumAs. Dietary information was obtained through a self-reported food intake questionnaire. Log(10)-transformed drinking water arsenic concentration at home was a significant (P<0.0001) predictor of SumAs (R(2)=0.18). Associations improved (R(2)=0.29, P<0.0001) when individuals with less than 1?μg/l of arsenic in drinking water were removed and further improved when analyses were applied to individuals who consumed amounts of home drinking water above the median volume (R(2)=0.40, P<0.0001). A separate analysis indicated that AsB and DMA[V] were significantly correlated with fish and shellfish consumption, which may suggest that seafood intake influences DMA[V] excretion. The Spearman correlation between arsenic concentration in toenails and SumAs was 0.36 and between arsenic concentration in toenails and arsenic concentration in water was 0.42. Results show that arsenic exposure from drinking water consumption is an important determinant of urinary arsenic concentrations, even in a population exposed to relatively low levels of arsenic in drinking water, and suggest that seafood intake may influence urinary DMA[V] concentrations.     

负载金属饮水除砷材料的研究

目的　研究负载金属多孔材料对饮水中砷的去除效果。方法　以活性炭、活性氧化铝、硅胶、大孔树脂等多孔材料为载体 ,以铁盐、锆盐等为活化试剂制备负载金属除砷材料 ,考察材料制备条件及材料的静态和动态除砷作用。结果　选择以活性炭为载体材料、硝酸铁为活化试剂制备饮水复合除砷材料。按现行规范砷限值为 0 0 5mg L计算 ,试验的载铁活性炭材料对于三价砷浓度为 0 2 84mg L和五价砷浓度为0 2 5 4mg L模拟饮水 ,除砷容量分别可达 2 94mg g和 2 5 6mg g。结论　以活性炭和硝酸铁制备的载铁活性炭材料具有较好的饮水除砷性能     

农村饮水降氟设备运行效果研究

目的探讨农村饮水降氟设备降氟水的水质特性以及降氟效果.方法2002-2004年,选择应用电渗析和反渗透技术进行饮水降氟的天津市农村为调查地区.选择某县运行2～3 a的4座电渗析除氟站和6座反渗透除氟站开展调查.同时在其他县选择3座活性氧化铝除氟站和2座纳滤除氟站进行了调查.水质指标包括:pH值、浊度、溶解性总固体(TDS)、总硬度、氟化物、硫酸盐、铝.水质分析和评价依据<生活饮用水卫生规范>(2001).结果反渗透降氟设备和电渗析降氟设备均可以使水氟浓度降低至1.0 mg/L以下,去除率分别为90.01%和75.32%,总硬度、TDS也有不同程度下降,去除率为75.83%～93.48%.纳滤降氟设备也可以使水氟降低至1.0mg/L以下,去除率为75.16%,总硬度、TDS也有不同程度下降,去除率为77.22%和64.90%.结论该次调查的电渗析、反渗透和纳滤设备效果可靠,在技术上适用于不同TDS含量的农村饮水降氟.但反渗透降氟水在降氟的同时,去除水中大部分人体必需微量元素,长期饮用的健康效应有待进一步开展研究.     

Adsorption removal of benzalkonium chloride by granular activated carbon for medical waste water treatment.

The adsorption removal of benzalkonium chloride disinfectant by granular activated carbon is discussed. The adsorption isotherm of benzalkonium chloride was expressed by the Freundlich equation. A significant correlation was found between the amount of benzalkonium chloride adsorbed in less than 1000 ppm of equilibrium concentration and the micropore volume of activated carbon. As for the adsorption rate, a change in intraparticle diffusiveness was found with increasing adsorption ratio. No significant correlation between the values of intraparticle diffusiveness and the properties of activated carbon was found. It was concluded that the micropore volume of activated carbon was the dominant factor in the adsorption removal of benzalkonium chloride by granular activated carbon.     

强化饮水除砷剂的研制

长期饮用高砷水有害人体健康 ,而改饮低砷水可以缓解已发病者的症状。研究经济、高效、简便的饮水除砷剂是十分必要的。本课题研制的强化除砷剂具有除砷容量高 ,出水的含砷量低于 0 0 5mg L ;除砷功能专一 ,即只除去水中的砷而不改变水中其它元素的组成和含量 ;操作管理简单 ,进水、出水均无需调节pH ;除砷成本低 ,每吨成本仅为活性氧化铝或颗粒活性炭的 1 5 ,氧化催化剂可重复使用。有望广泛用于高砷水地区集中式和分散式供水的除砷系统。     

Fast and Considerable Adsorption of Methylene Blue Dye onto Graphene Oxide

The quite efficient adsorption of methylene blue dye from an aqueous solution by graphene oxide was studied. The favorable electrostatic attraction is the main interaction between methylene blue and graphene oxide. As graphene oxide has the special nanostructural properties and negatively charged surface, the positively charged methylene blue molecules can be easily adsorbed on it. In the aqueous solution of methylene blue at 293 K, the adsorption data could be fitted by the Langmuir equation with a maximum adsorption amount of 1.939 mg/mg and a Langmuir adsorption equilibrium constant of 18.486 mL/mg. The adsorption amount increased with the increase of the solution pH (3–11), was not affected significantly by KCl under the examined condition and the adsorption process was exothermic in nature. The fast and considerable adsorption of graphene oxide could be regarded as a potential adsorbent for cationic dye removal in wastewater treatment process.     

Comparative evaluation of conventional and alternative methods for the removal of arsenic from contaminated groundwaters

The present paper intends to summarize the recent findings regarding the development of alternative treatment methods applicable to small municipal drinking water systems. Small systems are frequently affected by the new permissible arsenic concentration rules, as imposed by several international organizations-World Health Organization, European Commission, United States Environmental Protection Agency. The innovate treatment methods reviewed are (a) adsorptive filtration, using iron oxide coated sand or polymeric materials; (b) zero-valent iron; (c) solar disinfection, solar oxidation and removal of arsenic (SORAS); (d) iron-based adsorbents, such as granular ferric hydroxide (GFH); (e) biological oxidation and removal of arsenic, accomplished simultaneously with the biological iron oxidation. In addition, other more conventional methods for arsenic removal are also discussed, such as iron or alum coagulation, lime softening, ion exchange, activated alumina and membrane separation processes. The aforementioned methods have been comparatively evaluated and the relevant conclusions have been drawn with respect to the applicability of arsenic treatment methods, depending on certain parameters, such as locally varying water quality characteristics, sustainability, and economic feasibility.     

Treatment of chrome plating wastewater (Cr+6) using activated alumina

Suitability of activated alumina for removal of hexavalent chromium from electroplating wastewater has been investigated. Activated alumina exhibited good sorption capacity for hexavalent chromium and pH has no pronounced effect on the sorption capacity. Both batch and column adsorption studies have been carried out and an adsorption column design indicated reasonable depth of column for practical application.     

High Efficiency Adsorption Removal of Arsenilic Acid and Arsenate(V) by Iron-Modified Corncob Biochar

It is crucial that a highly effective adsorbent can be used to simultaneously remove the composite pollution including both inorganic and organic arsenic from wastewater. In this work, the iron modified corncob biochar (MCCB), prepared via the co-precipitation of ferric chloride hexahydrate (FeCl₃?6H₂O) with sodium hydroxide (NaOH) on corncob biochar, was studied for the high efficiency removal of arsenilic acid (ASA) and arsenate [As(V)] in wastewater. X-ray diffraction, scanning electron microscopy, and fourier transform infrared spectroscopy were carried out to characterize the MCCB. At pH of 4.0–5.0, initial concentration of 10 mg/L ASA and 1 mg/L As(V), adsorbent dose of 0.4 g/L, the maximum adsorption capacities of ASA and As(V) were 49.20 and 4.89 mg/g, respectively. The adsorption performance of MCCB for ASA and As(V) was fitted well to the pseudo-second-order kinetic model. Results from this study indicate the promise of MCCB as an efficient, low-cost and environmentally friendly adsorbent for composite arsenic pollution.

     

Removal of Nitrite from Aqueous Solution Using Sugarcane Bagasse and Wheat Straw

Sugarcane bagasse and wheat straw were applied for the removal of nitrite ions from water samples. Batch experiments were conducted to establish optimum pH (5), initial nitrite concentration (5 mg/L), adsorbent dose (3 mg/L) and contact time (90 min). Under the optimized conditions, raw sugarcane bagasse was found to be a more effective (removal efficiency 90 %) adsorbent in removing nitrite ions than wheat straw (removal efficiency 63 %). Adsorption isotherms and kinetic parameters were also studied. The correlation coefficient values for Langmuir and Freundlich isotherm models were 0.9625 and 0.9590, respectively. The results showed that the adsorption of nitrite fairly fits both Langmuir and Freundlich adsorption isotherms for both adsorbents. The kinetics of the adsorption process follows the pseudo second-order kinetic model.     

新型氧化铝饮水除氟剂的研制与应用——Ⅲ.活性水铝石饮水除氟滤料的研制与应用

作者从七种天然物质中筛选了福建省漳浦县水铝石(gibbsite),制成新型氧化铝饮水除氟滤料。在现场设备中,装225kg该滤料,原水含氟量2.5mg/L,注入硫酸调进水pH至6.0～6.5,它通过滤床的停留时间为9.5min。三个运行周期平均处理供水535m~3,出水平均含氟量0.81mg/L,除氟容量3.64mg/g。滤料价格约为活性氧化铝的50％,它的处理水成本为0.1796元/t水。     

Comparative studies on adsorptive removal of phenol by three agro-based carbons: equilibrium and isotherm studies

The present study deals with the adsorption of phenol on carbon-rich black gram husk (BGH), green gram husk (GGH), and rice husk (RH). All these agro-wastes were collected from the local mills and physico-chemical treatments were carried out to improve their adsorption capacity. Batch studies were performed to evaluate the effect of various experimental parameters such as initial pH, contact time, adsorbent dosage, and initial phenol concentration (C(0)) of 100mg/l. Optimum conditions for phenol removal were found to be at pH 5.1 (in the range 2-12), an adsorbent dosage of 0.5 g/l of solution and for an equilibrium time of 6h. Equilibrium isotherms for the adsorption of phenol on BGH, GGH, and RH were analyzed by Freundlich, Langmuir, Temkin, Redlich-Peterson, and Dubinin-Radushkevich isotherm models. Redlich-Peterson isotherm was found to be the best representative for phenol-sorption on all the three adsorbents studied.     

Arsenic drinking water exposure and urinary excretion among adults in the Yaqui Valley, Sonora, Mexico

The objective of this study was to determine arsenic exposure via drinking water and to characterize urinary arsenic excretion among adults in the Yaqui Valley, Sonora, Mexico. A cross-sectional study was conducted from July 2001 to May 2002. Study subjects were from the Yaqui Valley, Sonora, Mexico, residents of four towns with different arsenic concentrations in their drinking water. Arsenic exposure was estimated through water intake over 24 h. Arsenic excretion was assessed in the first morning void urine. Total arsenic concentrations and their species arsenate (As V), arsenite (As III), monomethyl arsenic (MMA), and dimethyl arsenic (DMA) were determined by HPLC/ICP-MS. The town of Esperanza with the highest arsenic concentration in water had the highest daily mean intake of arsenic through drinking water, the mean value was 65.5 microg/day. Positive correlation between total arsenic intake by drinking water/day and the total arsenic concentration in urine (r = 0.50, P < 0.001) was found. Arsenic excreted in urine ranged from 18.9 to 93.8 microg/L. The people from Esperanza had the highest geometric mean value of arsenic in urine, 65.1 microg/L, and it was statistically significantly different from those of the other towns (P < 0.005). DMA was the major arsenic species in urine (47.7-67.1%), followed by inorganic arsenic (16.4-25.4%), and MMA (7.5-15%). In comparison with other reports the DMA and MMA distribution was low, 47.7-55.6% and 7.5-9.7%, respectively, in the urine from the Yaqui Valley population (except the town of Cocorit). The difference in the proportion of urinary arsenic metabolites in those towns may be due to genetic polymorphisms in the As methylating enzymes of these populations.