铁盐和铝盐混凝微滤工艺除As(V)的比较研究

选择FeCl₃和Al₂(SO₄)₃作混凝剂,采用小试规模的混凝微滤膜反应器比较了铁盐和铝盐混凝微滤工艺的除As(V)效果、相关性能指标及适用范围.结果发现,Fe³⁺投加量为4 mg/L、Al₂(SO₄)₃投加量为50 mg/L时,铁盐和铝盐工艺的除As(V)效果大致相当,均可使水中As(V)的浓度从100 μg/L左右降低到10 μg/L以下,最低为1.68 μg/L.出水浊度均小于0.1 NTU,出水中铁、铝和SO^2-₄浓度均符合饮用水标准.铁盐工艺出水pH值比原水大约高0.5,铝盐工艺处理前后水的pH值基本不变.反应器运行结束静沉24 h后,铁盐工艺浓缩比为1 791,是铝盐工艺的2.54倍,污泥中As(V)的含量也大大高于铝盐工艺,去除同等重量的As(V)所产生的污泥量较铝盐工艺少得多.因此,对于仅有砷超标的饮用水,应优先考虑铁盐工艺.按除氟所需混凝剂数量投加Al₂(SO₄)₃,铝盐工艺即可在去除As(V)的同时去除氟,铁盐工艺则不能去除氟.因此,对于砷和氟均超标的饮用水,可采用铝盐工艺同时去除砷和氟.     

负载型纳米铁吸附剂去除饮用水中As(Ⅲ)的研究

以活性炭为载体,利用液相还原方法制备了一种负载型纳米铁吸附剂,载入量(Fe/炭)为82.0 mg/g.纳米铁在活性炭孔内呈针状,其直径为30～500 nm,长度为1?000～3?000 nm.该吸附剂在pH 6.5,(25±2)℃,As(Ⅲ)初始浓度为2 mg/Ｌ,吸附剂用量为1.0 g/Ｌ时,As(Ⅲ)的去除率为99.86%,吸附剂的砷吸附容量为1.997 mg/g;吸附速率在前12 h较快,可达94.3%,72 h达到吸附平衡.吸附过程中As(Ⅲ)部分被吸附剂氧化.PO^３－₄、SiO^２－_３对As(Ⅲ)的去除抑制较大,而SO^２－₄、CO^２－_３、C₂Ｏ^２－₄等离子对砷的去除影响较小.吸附平衡后的吸附剂可以用0.1 mol/Ｌ NaOH溶液洗脱再生,再生效率较高.室内实验数据表明,该吸附剂在饮用水除砷领域具有较好的应用前景.     

铝盐混凝除砷影响因素及机制研究

铝盐混凝法被广泛应用于饮用水除砷工程.本研究选取三氯化铝(AlCl3)和富含Al13的聚合氯化铝(PACl)为絮凝剂,考察铝形态、pH值、腐殖酸(HA)以及共存阴离子对砷去除的影响与机制.结果表明,2种絮凝剂对As(Ⅲ)去除效能较低,对As(Ⅴ)去除率可达到近100%.pH影响混凝过程中铝形态分布,从而对铝盐混凝除砷效能产生重要影响.铝盐除砷效能与混凝过程中的Al13形态含量呈正相关关系.由于竞争吸附作用,HA和部分共存阴离子对砷的混凝去除产生负面影响.HA对混凝效能影响与絮凝剂投药量相关,投药量越低,则影响越大.PO34-和F-对混凝除砷效能影响显著,SiO23-、CO23-和SO24-对混凝除砷效能影响较小.本研究将对饮用水强化混凝去除原水中砷具有指导意义.     

臭氧氧化分解饮用水中嗅味物质2-甲基异莰醇

比较了几种常见氧化剂对饮用水中嗅味物质2-甲基异莰醇(2-methylisoborneol,MIB)的氧化去除效果.结果表明,KMnO₄、NaClO、H₂O₂等氧化剂的氧化作用对水中MIB的去除效果均较差,而臭氧却能有效地将其氧化;考察了pH对臭氧化去除MIB的影响规律,发现pH在7.0～10.0条件下,随着pH值增加MIB去除率增加,但当pH达到10.0左右时,MIB的去除率反而下降;MIB的臭氧化去除效果随着自由基捕获剂(重碳酸盐和叔丁醇)的浓度增加而明显地降低,说明臭氧化去除水中MIB主要遵循自由基作用机理;以松花江江水为本底进行试验和与蒸馏水进行试验的结果相差不大,原因可能是由于松花江水体中碳酸盐浓度较低(小于50 mg/L),对自由基捕获能力较小,同时江水中的部分腐殖质(NOM)对臭氧去除MIB的过程起到了促进作用.     

纳米TiO2协助下As(Ⅲ)在可变电荷土壤中的光催化氧化和吸附

环境中As(Ⅲ)的毒性和活动性均大于As(Ⅴ),将As(Ⅲ)转化为As(Ⅴ)有利于砷的固定.为此使用自制的光催化装置,采用一次平衡法研究了纳米TiO₂协助下As(Ⅲ)在土壤悬液体系中的光催化氧化及土壤对氧化产物的吸附.结果表明,As(Ⅲ)的光催化氧化量随TiO₂的加入量和光照时间的增加而增加,当TiO₂的加入量为1.0 g·L^-1,光照时间为90 min时As(Ⅲ)可以达到很好的转化效果.As(Ⅲ)在土壤中的光催化氧化及土壤对氧化产物的吸附增加了水体中砷的去除量,在Fe/Al氧化物与TiO₂体系中也观察到类似的效应.实验结果还表明γ-Al₂O₃也可诱导As(Ⅲ)的光催化氧化.     

锰氧化物负载施氏矿物去除酸性矿山废水中As(III)的性能及机理

施氏矿物是天然的砷吸附剂,但其存在酸性条件下对As(III)吸附性能较弱且无法对As(III)氧化降毒的缺陷. 采用液相沉淀法成功制备出锰氧化物负载施氏矿物(MnO_x@Sch),研究锰负载量、初始pH值和共存离子对MnO_x@Sch去除As(III)的影响,并采用吸附动力学结合XPS、FTIR及TEM等表征探究该过程的机理. 结果表明:在初始pH=3、投加量为0.5 g·L^-1、As(III)初始浓度为1 mg·L^-1的条件下,As(III)与MnO_x@Sch反应后的剩余浓度仅为2.42~3.38 μg·L^-1.MnO_x@Sch去除As(III)受初始pH影响较小,H₂PO₄^-共存时As(III)去除存在明显的抑制作用. MnO_x@Sch 去除As(III)的过程符合准二级动力学方程和颗粒内扩散方程. 液相化学组分和固相产物表征分析显示MnO_x@Sch对As(III)的去除机理可概括为As(III)氧化、静电吸附和络合配位及配体交换. 研究结果可为施氏矿物及其改性材料应用于酸性矿山废水砷污染治理提供理论依据.     

聚合氯化钛铁盐混凝除砷性能研究

采用微量滴碱法制备聚合氯化钛铁混凝剂(PTFC),并对其混凝除砷性能进行了初步探究。对聚合氯化钛/铁混凝剂粉末SEM图进行分析,并考察不同Ti/Fe比例、曝气氧化、碱化度、碱化剂、混凝剂投加量、pH值、共存离子等对除砷率的影响。结果显示:pH值为7.5时,As(Ⅲ)去除率随PTFC投加量的增加而增大;PTFC在弱酸性条件下对As(Ⅲ)的去除效果最佳。曝气氧化对PTFC除As(Ⅲ)有显著促进作用,Ti/Fe物质的量比为5/5时制备的碱化度为0.6的PTFC混凝后经曝气20 min,对As(Ⅲ)的去除率从55.3%提高到93.1%。碱化剂对PTFC混凝除砷的影响不大。共存阴离子SiO_3~(2-)对As(Ⅲ)的去除有明显抑制作用,但PO_4~(3-)对PTFC混凝去除As(Ⅲ)的影响相比较于单一金属盐较小,共存阳离子Ca~(2+)对PTFC去除As(Ⅲ)有促进作用。     

不同性质天然有机物对水中颗粒稳定性影响的机理研究

以不同来源天然有机物(NOM)及其各分离组份和模型颗粒Al(OH)₃为研究对象,考察了pH值、二价金属离子Ca²⁺以及NOM的特性等因素对Al(OH)₃颗粒稳定性的影响,并通过研究几种NOM吸附性能和吸附前后的特性变化,进一步探讨了NOM对颗粒稳定性的影响机理.结果表明,Al(OH)₃颗粒的等电点pH_iep出现在pH5～6之间,吸附态有机物是造成颗粒稳定性提高的主要原因,溶液中自由态Ca²⁺离子能够起到压缩双电层的作用,降低吸附态NOM之间的静电斥力,减小表面负电性,增加pH_iep;吸附络合态Ca²⁺离子对颗粒表面负电性影响较小,但能够强化NOM在颗粒表面的吸附.NOM作为聚合态阴离子,在颗粒表面的吸附行为不符合Langmuir吸附模型,最大吸附发生在pH 4左右,吸附作用能够去除几种NOM中分子量较大的部分,并减小其羧基官能团的相对含量,NOM中大分子量、芳香性高的成分是造成水中颗粒稳定性提高的主要原因.     

原位形成生物铁锰氧化物对砷(Ⅲ/V)的去除效果与机制

通过改变砷的初始浓度、砷价态、细菌接种比、铁锰浓度等因素来研究不同条件下Pseudomonas putida strain MnB1原位诱导形成生物铁锰氧化物（Biogenic Fe-Mn oxides,BFMO）对As（Ⅲ）和As（V）的去除效果与机制.结果表明：①当As（Ⅲ）和As（V）初始浓度为0.5~5 mg·L^-1时,原位形成的BFMO对As（Ⅲ）和As（V）有良好的去除效率,均在62%以上;②当细菌接种比为0.1%~0.5%时,As（Ⅲ）和As（V）的去除效率与细菌接种比成正比,当细菌接种比大于0.5%时,As（Ⅲ）和As（V）的去除效率基本维持在85%以上,未发生明显变化;③当MnCO₃浓度为0.2~0.8 g·L^-1或Fe（Ⅱ）浓度为2.5~25 mg·L^-1时,原位诱导产生的BFMO对As（Ⅲ）和As（V）的去除率随MnCO₃浓度或Fe（Ⅱ）浓度的增加而增大;当MnCO₃或Fe（Ⅱ）浓度再升高时,As（Ⅲ）和As（V）的去除效率基本保持不变.微观特征分析结果表明,原位形成的BFMO与As（Ⅲ）和As（V）反应后主要产物为As（V）,其去除主要以吸附为主,还存在共沉淀作用.总体而言,原位形成的BFMO适用于砷污染水环境的修复.     

水源水中典型化学品突发污染的应急处理

针对被典型化学品双酚A(BPA)与邻苯二甲酸二乙酯(DEP)污染原水的应急处理工艺进行了研究.结果表明,活性炭吸附可有效去除双酚A和DEP.拟二级动力学模型和Elovich模型较好地描述粉末活性炭对原水中BPA和DEP的吸附过程.中试条件下,50 mg/L的粉末活性炭可分别将原水中浓度约为500 μg/L的双酚A和3.3 mg/L的DEP处理达标.炭砂滤柱对2种化学品的动态吸附表明,BPA和DEP的去除率受它们初始浓度的影响较小,在滤速为5.1～15.3 m/h的范围内BPA和DEP的去除率基本不受滤速的影响.当同时采用粉末活性炭和炭砂滤柱工艺时, PAC的吸附过程是去除污染的主要阶段,炭砂滤柱可以作为粉末活性炭的有效补充保证一定的安全系数.KMnO₄和Cl₂均不能氧化DEP,3 mg/L的KMnO₄和1.5 mg/L的Cl₂可几乎完全氧化水中浓度为850　μg/L的BPA,BPA的氯化产物和KMnO₄的氧化产物及其毒性有待于进一步研究.　1.5 mg/L高锰酸钾和PAC联用对去除DEP无协同作用,对去除BPA有促进作用.     

高锰酸钾预氧化强化处理受污染的水库水

考察了高锰酸钾强化常规工艺处理受污染水库水效能．进行生产性试验对比了投加高锰酸钾前后处理水浊度、颗粒物、CODMn及藻类的去除效果,并对高锰酸钾强化除污染的可能作用机制进行了探讨。结果表明：投加高锰酸钾使得澄清池平均出水浊度由4．490NTU降低至3．995NTU;出厂水平均浊度由0．670NTU降低至0．463NTU;颗粒物去除率由71．72％提高至83．86％;澄清池出水平均CODM。由3．21mg／L降低至2．86mg／L;出厂水平均CODM。由2．99mg／L降低至2．62mg／L;藻类总数去除率由36．49％提高至71．27％．且藻类种属也相应减少。高锰酸钾能有效地强化受污染水库水中不同污染物的去除效能,显著地提高出水水质。     

溴离子和溴酸盐活性炭竞争吸附及溴酸盐生成影响

采用3种活性炭对水体中溴离子和溴酸盐的吸附去除规律进行了考察.结果表明,单吸附条件下溴离子和溴酸盐的吸附去除效率分别达到69%和88%以上,双吸附质条件时溴离子去除率减少到10%.溴酸盐去除率为60%以上;有机物与溴酸盐之间存在竞争吸附关系,AC-400的孔径分布条件更适合于有机物的吸附过程.而不利于溴酸盐的吸附,在低浓度平衡溶液条件下(ce＜72 mg·L-1),AC-100对有机物的吸附能力较高,在溶液平衡浓度72mg·L-1＜ce＜211 mg·L-1条件时,AC-150对有机物的吸附能力较强,影响程度取决于活性炭比表面积和粒度分布等因素;溴酸盐的去除效率同时受到水体中氨含量和pH的影响,氨含量超过200μg/L以上溴酸盐减少量变化不显著,较低pH值溴酸盐生成量较少.     

Application of permanganate in the oxidation of micropollutants: a mini review

As a green oxidant, permanganate has received considerable attention for the removal of micropollutants in drinking water treatment. To provide a better understanding of the oxidation of organic micropollutants with permanganate, the oxidation kinetics of 32 micropollutants were compiled. The pollutants include algal toxins, endocrine disrupting chemicals (EDCs), and pharmaceuticals. The oxidation kinetics of micropollutants by permanganate were found to be first order with respect to both contaminant and permanganate concentrations from which second-order rate constants (k″) were obtained. Permanganate oxidized the heterocyclic aromatics with vinyl moiety (i.e., microcystins, carbamazepine, and dichlorvos) by the addition of double bonds. For the polycyclic aromatic hydrocarbons (PAHs) with alkyl groups, permanganate attacked the benzylic C-H through abstraction of hydrogen. The mechanism for the oxidation of phenolic EDCs by permanganate was a single electron transfer and aromatic ring cleavage. The presence of background matrices could enhance the oxidation of some phenolic EDCs by permanganate, including phenol, chlorinated phenols, bisphenol A, and trichlosan. The toxicity of dichlorvos solution increased after permanganate oxidation, and the estrogenic activity of bisphnol A/estrone increased significantly at the beginning of permanganate oxidation. Therefore, the toxicity of degradation products or intermediates should be determined in the permanganate oxidation processes to better evaluate the applicability of permanganate. The influence of background ions on the permanganate oxidation process is far from clear and should be elucidated in the future studies to better predict the performance of permanganate oxidation of micropollutants. Moreover, methods should be employed to catalyze the permanganate oxidation process to achieve better removal of micropollutants.     

Preparation and evaluation of Zr-β-FeOOH for efficient arsenic removal

A Zr-β-FeOOH adsorbent for both As(V) and As(III) removal was prepared by a chemical co-precipitation method.Compared with β-FeOOH,the addition of Zr enhanced the adsorption capacities for As(V) and As(III),especially As(III).The maximum adsorption capacities for As(III) and As(V) were 120 and 60mg/g respectively at pH 7.0,much higher than for many reported adsorbents.The adsorption data accorded with Freundlich isotherms.At neutral pH,for As(V),adsorption equilibrium was approached after 3 hr,while for As(III),adsorption equilibrium was approached after 5 hr.Kinetic data fitted well to the pseudo second-order reaction model.As(V) elimination was favored at acidic pH,whereas the adsorption of As(III) by Zr-β-FeOOH was found to be effective over a wide pH range of 4-10.Competitive anions hindered the adsorption according to the sequence:phosphate > silicate > bicarbonate > sulfate > nitrate,while Ca2+ and Mg2+ increased the removal of As(III) and As(V) slightly.The high adsorption capability and good performance in other aspects make Zr-β-FeOOH a potentially attractive adsorbent for the removal of both As(III) and As(V) from water.     

铁屑内电解法处理EDTA溶液中络合铜离子

采用批式试验和现代仪器分析研究了铁屑内电解法处理EDTA溶液中络合铜离子,考察了溶液浓度、溶液pH、温度和铁屑粒径等因素对铜离子去除过程的影响.结果表明,铜离子去除过程符合表观一级动力学方程.在pH 2.0～11.0范围内,pH值越低越利于铜离子去除;在酸性条件下溶液pH随内电解进行升高,在碱性条件下溶液pH随内电解进...     

多功能高铁酸盐去除饮用水中砷的研究

利用高铁酸盐的氧化絮凝双重水处理功能,取代氧化铁盐法,对其氧化除砷效果进行了评价.考察了高铁酸盐除砷的适宜pH值范围、氧化时间和絮凝时间,定性和定量分析了盐度、硬度等因素对高铁酸盐除砷效果的影响.结果表明,高铁酸盐与砷浓度比为15∶1,最佳pH为5.5～7.5,适宜的氧化时间为10min,絮凝时间为30min,处理后的水样中砷残留量可达到国家饮用水标准;盐度和硬度不干扰除砷过程.与传统的铁盐法和氧化铁盐法对比,此方法简便,高效,无二次污染,更有利于饮用水的清洁化除砷.     

Ru(III) catalyzed permanganate oxidation of aniline at environmentally relevant pH

Ru（Ⅲ） was employed as catalyst for aniline oxidation by permanganate at environmentally relevant pH for the first time. Ru（Ⅲ） could significantly improve the oxidation rate of aniline by 5-24 times with its concentration increasing from 2.5 to 15 μmol/L. The reaction of Ru（Ⅲ） catalyzed permanganate oxidation of aniline was first-order with respect to aniline, permanganate and Ru（Ⅲ）, respectively. Thus the oxidation kinetics can be described by a third-order rate law. Aniline degradation by Ru（Ⅲ） catalyzed permanganate oxidation was markedly influenced by pH, and the second-order rate constant （ktapp） decreased from 643.20 to 2.67 （mol/L）^-1 sec^-1 with increasing pH from 4.0 to 9.0, which was possibly due to the decrease of permanganate oxidation potential with increasing pH. In both the uncatalytic and catalytic permanganate oxidation, six byproducts of aniline were identified in UPLC-MS/MS analysis. Ru（Ⅲ）, as an electron shuttle, was oxidized by permanganate to Ru（Ⅵ） and Ru（Ⅶ）, which acted the co-oxidants for decomposition of aniline. Although Ru（Ⅲ） could catalyze permanganate oxidation of aniline effectively, dosing homogeneous Ru（Ⅲ） into water would lead to a second pollution. Therefore, efforts would be made to investigate the catalytic performance of supported Ru（Ⅲ） toward permanganate oxidation in our future study.     

Enhanced removal of organics by permanganate preoxidation using tannic acid as a model compound – Role of in situ formed manganese dioxide

The effect of permanganate preoxidation on organic matter removal during the coagulation with aluminum chloride was investigated using tannic acid as a model compound. Results showed that a small amount of KMnO4 (0.75 mg/L) increased the removal efficiency of tannic acid up to 20%, as compared to the process of coagulation by aluminum chloride alone. The key factor enhancing the removal efficiency of tannic acid in preoxidation process was the in situ formation of a reductant manganese dioxide. The complexation model was used to describe the reaction between MnO2 and tannic acid. Under weak pH condition, tannic acid was difficult to be adsorbed by MnO2 due to the static electrical repulsive forces. The presence of Ca2+ served as a bridge to hold the negative charged MnO2 and tannic acid together, which could be a crucial factor influencing tannic acid adsorption by in-situ manganese dioxide.     

Arsenic removal from groundwater by acclimated sludge under autohydrogenotrophic conditions

Arsenic in the environment is attracting increasing attention due to its chronic health effects. Although arsenite(As(III)) is generally more mobile and more toxic than arsenate(As(V)), reducing As(V) to As(III) may still be a means for decontamination, because As(III) can be removed from solution by precipitation with sulfide or by adsorption or complexation with other metal sulfides. The performance of As(V) bio-reduction under autohydrogenotrophic conditions was investigated with batch experiments. The results showed that As(V) reduction was a biochemical process while both acclimated sludge and hydrogen were essential. Most of the reduced arsenic remained in a soluble form, although 20% was removed with no addition of sulfate, while 82% was removed when sulfate was reduced to sulfide. The results demonstrated that the reduced arsenic was re-sequestered in the precipitates, probably as arsenic sulfides. Kinetic analysis showed that pseudo first-order kinetics described the bio-reduction process better than pseudo second-order. In particular, the influences of pH and temperature on As(V) reduction by acclimated sludge under autohydrogenotrophic conditions and total soluble As removal were examined. The reduction process was highly sensitive to both pH and temperature, with the optimum ranges of pH 6.5–7.0 and 30–40°C respectively. Furthermore, Arrhenius modeling results for the temperature effect indicated that the As(V) reduction trend was systematic. Total soluble As removal was consistent with the trend of As(V) reduction.     

高锰酸盐复合剂强化混凝对水中天然有机物的去除机制研究

利用流动电流、絮凝脉动颗粒检测技术、分子量分布及XAD树脂分类技术对高锰酸盐复合剂强化混凝去除水中天然有机物的机制进行了研究.结果表明,高锰酸盐复合剂提高了硫酸铝的混凝效果,投加0.75 mg/L高锰酸盐复合剂后,较单独投加硫酸铝对天然有机物的去除率可提高13个百分点.流动电流(SC)检测结果表明,高锰酸盐复合剂使有机物表面所带的负电性减弱,稳定性降低.如单独投加60 mg/L硫酸铝时SC值为55.2,而投加0.50、 0.75和1.0 mg/L的高锰酸盐复合剂预氧化处理后,SC值分别升高至61.4、 69.6和87.0.投加高锰酸盐复合剂后,絮凝指数增加,表明高锰酸盐复合剂及反应过程中生成的新生态水合二氧化锰对混凝起到了强化作用.分子质量分布及XAD树脂分类结果表明,高锰酸盐复合剂提高了混凝过程对小分子质量和亲水性有机物的去除能力,如硫酸铝混凝后亲水性有机物的含量为1.90 mg/L,而投加高锰酸盐复合剂后,可使其含量降至1.32 mg/L.