具有氧化性能混凝剂的研发及对有机物的去除效果

通过将零价纳米铁(nZVI)与Al_(13)进行复配,研发了兼具原位氧化功能的高电荷聚合态混凝剂nZVI@Al_(13),考察了nZVI、Al_(13)不同配比和pH值等因素对有机物去除效果、分子质量分布及结构组成的影响。结果表明,混凝剂复配后,Al_(13)中高聚合态铝含量增加,提高了混凝剂的混凝效率。中性条件下,腐殖酸(HA)去除率随Al_(13)投量的增加先增大后趋于平缓,Al_(13)的最佳投量为0. 03 mmol/L,此时HA去除率约为70%;单独nZVI对HA的最大吸附去除率仅为10%; nZVI和Al_(13)复配后对HA的去除效果好于单独两种方式的加和,nZVI对Al_(13)的强化混凝起到协同作用。当pH值 7. 0时,过多的OH~-使得Al_(13)解聚,影响混凝效果,nZVI和Al_(13)对HA的去除效果均有所下降。当pH值7. 0时,复配混凝剂对HA的去除率均优于单独Al_(13),最大去除率达到84%。复配混凝剂对分子质量2 000 u的有机物的去除效果较单独Al_(13)提高了约8%。     

聚硅酸的数学模型及聚铁混凝剂的品质与性能

针对聚硅酸(PS)的成冻时间(t)与聚合pH值、初始SiO2含量及聚合温度(T)的关系进行数学建模,并研究了pH对具有一定聚合度PS形态的影响情况,最后对比研究了聚硅酸铁(PSF,自制)、聚合硫酸铁(PFS)及复合铝铁(PFA)对低温、低浊水的混凝性能及其微观品质(微观形态、Zeta电位及粒径).结果表明,对PS制备过程进行多项式分段数学建模是工业制备优质PSF的基础条件,t-pH模型的拟合效果最好,而t-T拟合的精度相对较差.将具有一定聚合度的PS的pH值调低后,部分PS解聚,解聚后的状态完全不同于初始同样低pH值的状态.PSF独特的微观特征正是其具有优异混凝性能的根本原因,低温、低浊水的混凝机理是以电中和/脱稳为前提条件,以架桥为必要条件.     

聚硅铁混凝去除腐殖酸的研究

考察了聚硅铁(PSF)对腐殖酸(HA)的去除效果及影响因素,并与聚合硫酸铁(PFS)、硫酸铁[Fe_2(SO_4)_3]进行了比较.结果表明,当5相似文献   

聚硅酸铁的自然老化研究

采用共聚工艺制备不同Si/Fe值的聚硅酸铁(PSF)混凝剂,使其分别在封闭及敞开条件下自然老化,并采用透射电镜及搅拌试验考察PSF的微观形态及混凝性能的变化,同时对比分析了液体PSF自然老化与固化的成本。结果表明,老化前PSF具有分形维数很大的枝状结构,老化后PSF的枝化度降低,但其形态尺寸明显增大;老化方式对不同Si/Fe值的PSF混凝性能的影响基本一致,延长沉淀时间或增加投药量均可消除由于PSF老化而导致的混凝性能的微小降低;自然老化可以降低药剂使用成本、简化工艺过程,具有很好的市场推广价值。     

天然粉末二氧化锰处理染料废水的试验研究

分别以罗丹明B和甲基橙为目标化合物配制染料废水，研究了粉末态二氧化锰（PMN）的脱色性能，考察了pH值和接触时间对其脱色效果的影响。结果表明，pH值是影响脱色效果的关键因素，较低的pH值和适宜的接触时间有利于废水脱色。pH值为1．2时，PMN对甲基橙的脱色率为92．8％，对罗丹明B的脱色率为81．9％；pH值为1．5时，达到最大脱色率所需的时间为15min。酸性条件下，PMN对染料的去除为吸附和氧化综合作用的结果。     

PAFS-PDM混凝剂处理油田钻井废水实验

文章以硫酸铝、硫酸铁与聚二甲基二烯丙基氯化铵（PDM）为原料,制备PAFS-PDM复合混凝剂 并表征其结构形态,同时考察了pH值、混凝剂投加量对油田钻井废水中COD的去除率以及溶液中Zeta电位的影响,为复合混凝剂的开发及使用提供一定的参考。研究结果表明：当PAFS-PDM复合混凝剂的投加量为8000mg/L、pH值为5时对塔里木油田钻井废水中COD的去除率达93.05％,此时溶液中Zeta电位较低。XRD衍射及SEM表征结果显示,制备的PAFS-PDM复合混凝剂中存在铝铁—羟基聚合物,微观形态下复合混凝剂将聚合形成的扇形片状结构再相互连接成发散立体结构,从而增大了比表面积,提高了混凝剂的吸附架桥能力,结合Zeta电位分析得出PAFS-PDM复合混凝剂为阳离子型混凝剂,而且具有较强的电中和能力。     

酸化剂对聚硅铁混凝性能的影响研究

采用盐酸、硫酸、磷酸和乙酸等4种不同的酸化剂制备了具有相同Fe／Si（物质的量之比）的聚硅铁（PSF）混凝剂,考察了四种混凝剂的稳定性、形态及其混凝效果。试验结果表明,在酸性条件下,由乙酸制备的聚硅酸的胶凝时间较其他三种无机酸的长,相应制备的药剂以PSF乙酸的混凝性能最佳（投药量在6mgFe／L时,除浊率达95％左右,对UV254的去除率达80％左右）,PSF盐酸和PSF硫酸次之,PSF磷酸的最差（投药量〉2mgFe／L时会增大水样的浊度,投药量为8mgFe／L时对UV254的去除率达到55％的最高值）。这表明乙酸作为弱酸,与硅酸的聚合速度较为缓慢,有利于提高聚硅酸的稳定性,并能改善聚硅铁的混凝效果。     

膨润土对重金属离子Pb2+,Zn2+, Cr(Ⅵ),Cd2+的吸附性能

试验研究了pH值、吸附时间和吸附剂用量对膨润土吸附重金属离子Pb^2＋，Zn^2＋，Cr（VI）和Cd^2＋的影响．结果表明，在本试验的pH值、吸附时间及吸附剂用量条件下，膨润土对Pb^2＋，Zn ^2＋，Cd ^2＋的吸附效果均优于其对Cr（Ⅵ）的吸附效果；pH值是影响上述吸附的重要因素，离子交换和表面络合是上述吸附的主要形式．     

聚合硅酸铁处理低温低浊水的效果研究

用自制的聚合硅酸铁(PSF)作混凝剂进行低温低浊水的烧杯搅拌实验,考察其混凝性能。并与聚合氯化铝(PAC)相比较。结果表明:在处理低温低浊水时,聚合硅酸铁(PSF)和聚合氯化铝(PAC)在达到相同处理效果时,聚合硅酸铁(PSF)用量少。聚合硅酸铁(PSF)处理过程中产生的矾花更大,沉降时间更短且出水符合饮用水水质标准。     

二氧化氯/混凝剂工艺处理含铁水的试验研究

通过向含铁水中投加二氧化氯和混凝剂,考察了二氧化氯对水中铁的去除效果及其影响因素。结果表明,二氧化氯投加量、原水pH、预氧化时间和混凝剂投加量对铁的去除效果均有较大的影响。当原水Fe2+浓度为5 mg/L时,二氧化氯最佳投加量为5 mg/L,最佳氧化时间为10 min,混凝剂的最佳投加量为1 mg/L,最佳pH值为7～9,对铁离子的去除率可达到94.0%。     

A study of coagulation mechanisms of polyferric sulfate reacting with humic acid using a fluorescence-quenching method

A fluorescence-quenching method is developed to assess the effect of pH on the coagulation mechanism of humic acids (HA) reacting with metal ions. A polyferric sulfate (PFS) synthesized in our laboratory is adopted as the coagulant to simplify the hydrolysis process and increase the experimental precision. The following results are discovered. When the concentration of PFS increases from 2 to 10 mg/L, the effective pH range of HA removal changes from 4.0-5.0 to 4.0-7.5. At increased coagulation pH, the ferric ions may still react with HA but unable to neutralize the surface charge completely. The residual concentrations of HA measured by fluorescence spectrophotometer are lower than those by TOC, as a consequence of the fluorescence-quenching effect. This demonstrates that the coagulation of HA by PFS at low pH is mainly due to charge-neutralization. The adsorption of the HA on the pre-formed iron hydroxide flocs is accompanied by the dissociation of Fe ions from the floc structure until the equilibrium has been reached, which is evidenced by the presence of the Fe-HA complexes in the solution during adsorption experiment. This is quite different from the characteristics of flocs formed by PFS associated with HA in the coagulation. Within the pH range investigated, the complex-formation and the hydrolysis are the two competitive reactions happened between the hydroxide ions in solution and the functional groups of HA. Therefore, the removal of HA is not caused by adsorbing onto the iron hydroxide resulted from PFS hydrolysis, but through the complex-formation between the PFS and the HA.     

Adsorption of p-chlorophenol by biofilm components

Through batch equilibrium experiments under the conditions of temperature 25 degrees C, pH values of 2.7, 5.3 and 6.1, the p-chlorophenol (4-cp) adsorption to biofilm components was investigated in this study. The contributions of biofilm components to 4-cp adsorption were discussed by comparing four adsorption systems, i.e. 4-cp adsorbed by model suspended particulate matter (kaolin) with biofilm coating, bacteria, bacterial exopolysaccharide (EPS) and kaolin, respectively. Langmuir and Freundlich isotherm equations were used to evaluate the experiment data. All the four adsorptions fitted for the two equations. Equilibrium isotherms were obtained for 4-cp adsorption on different adsorbents. The kinetic characteristics of 4-cp adsorption by biofilm components and the effect of pH on the kinetic process were investigated. The time to reach the highest adsorption amount and near equilibrium state in the four systems was different. The 4-cp adsorption by kaolin with biofilm coating reached near equilibrium at 60 min at pH 6.1. The 4-cp adsorption by EPS and kaolin reached near equilibrium at 150 and 180 min, respectively. But the 4-cp adsorption by bacteria showed no evident near equilibrium during 3 h in the experiment. The impact of pH value on the adsorption was also examined. The adsorption amount slightly increased with increasing pH from 2.7 to 6.1 for the adsorption systems of bacterial EPS and kaolin, but it slightly decreased in the systems of kaolin with biofilm coating and bacteria.     

Electrocoagulation versus chemical coagulation: coagulation/flocculation mechanisms and resulting floc characteristics

Electrocoagulation (EC) and chemical coagulation (CC) are employed in water treatment for particle removal. Although both are used for similar purposes, they differ in their dosing method - in EC the coagulant is added by electrolytic oxidation of an appropriate anode material, while in CC dissolution of a chemical coagulant is used. These different methods in fact induce different chemical environments, which should impact coagulation/flocculation mechanisms and subsequent floc formation. Hence, the process implications when choosing which to apply should be significant. This study elucidates differences in coagulation/flocculation mechanisms in EC versus CC and their subsequent effect on floc growth kinetics and structural evolution. A buffered kaolin suspension served as a representative solution that underwent EC and CC by applying aluminum via additive dosing regime in batch mode. In EC an aluminum anode generated the active species while in CC, commercial alum was used. Aluminum equivalent doses were applied, at initial pH values of 5, 6.5 and 8, while samples were taken over pre-determined time intervals, and analyzed for pH, particle size distribution, ζ potential, and structural properties. EC generated fragile flocs, compared to CC, over a wider pH range, at a substantially higher growth rate, that were prone to restructuring and compaction. The results suggest that the flocculation mechanism governing EC in sweep floc conditions is of Diffusion Limited Cluster Aggregation (DCLA) nature, versus a Reaction Limited Cluster Aggregation (RLCA) type in CC. The implications of these differences are discussed.     

Studies on the effect of humic acids and phenol on adsorption-ultrafiltration process performance

Application of pressure-driven membrane processes, such as ultrafiltration (UF) and microfiltration (MF) for surface water treatment have become very popular during last decades. Membrane fouling by humic substances (HS) is one of the major limiting factors in these processes. In order to alleviate the unfavorable effects of the presence of HS in the feed on the process performance UF and MF are often combined with adsorption on powdered activated carbon (PAC). The main goal of the present study was to evaluate the effect of humic acid (HA) on membrane fouling during UF. Moreover, the effect of PAC addition to the feed on UF process, especially on flux decline was determined. The applicability of the adsorption-ultrafiltration (PAC/UF) system to purification of water containing low (phenol) and high molecular (HA) was also investigated. Three different polymer UF membranes, prepared from polysulfone (PSF), cellulose acetate (CA) or polyacrylonitrile (PAN) were applied. It was found that the membranes prepared from PSF and CA are very susceptible to fouling caused by HA. The permeate flux decreased for ca. 50% during UF of HA solution through the PSF membrane and for ca. 45%-through the CA membrane. In the case of the PAN membrane, a negligible effect of HA on the flux was observed. On the basis of the FTIR spectra it was found that the drop in the permeate flux through these membranes may result from interactions between the negatively charged functional groups present on the membrane surface, such as carboxyl groups (CA) and sulfone groups (PSF) with HA, which results in coating of the membrane surface with HA. When PAC was added to the feed containing HA, the permeate flux through the CA and PAN membranes was maintained on a practically unchanged level. However, in case of the PSF membrane, a 50% drop in the permeate flux in comparison with the flux value, when process was conducted without PAC addition was observed. That was supposed to be due to attractive forces among hydrophobic PAC particles, HA molecules and PSF membrane surface. The performed studies showed that the application of PAC/UF system was very effective in the removal of organic substances having both, low and high molecular weights. The role of PAC suspended in a feed in the PAC/UF system is the adsorption of low molecular organic compounds, which cannot be removed by UF alone.     

饮用水中溴化物的混凝去除及影响因素研究

在饮用水的消毒过程中，溴化物可与消毒剂反应生成具有“三致”效应的消毒副产物。为此，选择AlCl3作混凝剂，研究了混凝去除溴化物的效果及影响因素。结果表明，向模拟水样（溴化物初始浓度为0．2mg／L）中投加3-15mg／L的AlCl3，当无腐殖酸存在时对溴化物的去除率为93．3％-99．2％，当有腐殖酸存在时对溴化物的去除率为78．4％～98．4％；对于湘江原水。投加15mg／L的AlCl3时对溴化物的去除率为87．0％。在低混凝剂投量或高pH值条件下，腐殖酸的存在明显降低了对溴化物的去除率；在高混凝剂投量或低pH值条件下，腐殖酸对去除溴化物的影响较小。因此，可采用强化混凝去除饮用水中的溴化物。     

Reduction of chloroform formation potential of humic acid by sonolysis and ultraviolet irradiation

This study is concerned with the changes of chloroform formation potential during the reaction of humic acid (HA) and sodium hypochlorite caused by different oxidative pretreatments: ultraviolet (UV) irradiation, ultrasonic (US) irradiation or combined UV-US irradiations. The UV and US decomposition of a reagent HA in water was investigated. The characterization of the oxidized HA sample by UV absorptiometry, synchronous fluorescence spectroscopy and size exclusion chromatography points a synergetic effect of the combined process. The values of the chlorine demand and chloroform formation potential were conventionally determined after a 96 h reaction at neutral pH. It was found that all applied processes decreased the concentration of chloroform but the highest decrease was observed for the UV-US treatment.     

Removal of antimony(V) and antimony(III) from drinking water by coagulation-flocculation-sedimentation (CFS)

Antimony occurs widely in the environment as a result of natural processes and human activity. Although antimony is similar to arsenic in chemical properties and toxicity, and a pollutant of priority interest to the USEPA and the EU, its environmental behaviors, control techniques, and even solution chemistry, are yet barely touched. In this study, antimony removal from drinking water with coagulation-flocculation-sedimentation (CFS) is comprehensively investigated with respect to the dependence of both Sb(III) and Sb(V) removal on the initial contaminant-loading level, coagulant type and dosage, pH and interfering ions. The optimum pH for Sb(V) removal with ferric chloride (FC) was observed at pH 4.5-5.5, and continuously reduced with further pH increase. Over a broad pH range from 4.0 to 10.0, effective Sb(III) removal with FC was obtained. Contrary to the effective Sb removal with FC, the degree of both Sb(III) and Sb(V) removal with aluminum sulfate (AS) was very low, indicating the impracticability of AS application for antimony removal. The presence of phosphate and humic acid (HA) markedly impeded Sb(V) removal, while exhibited insignificant effect on Sb(III) removal. The effects of coagulant type, Sb species and pH are more pronounced than the effects of coagulant dose and initial pollutant concentration. After preliminarily excluding the possibility of precipitation and the predominance of coprecipitation, the adsorption mechanism is used to rationalize and simulate Sb/FC coagulation with good result by incorporating diffuse-layer model (DLM).     

Adsorption des acides humiques sur charbon active en poudre. Influence du triphosphate de sodiumAdsorption of humic acids onto powdered activated carbon. The influence of sodium triphosphate

The use of activated carbon beds for the removal of natural humic and fulvic substances found in water supplies, has recently received considerable attention in water treatment operation (Lee et al., 1980; Le Cloirec et al., 1983). Moreover, the use of carbon adsorption for the reduction of haloform precursors (Anderson et al., 1981) and trihalomethanes produced by chlorination process, has contributed to a comprehensive investigation of adsorption characteristics of natural organic compounds (McCreary and Snoeyink, 1981). Many recent works showed the influence of adsorption system characteristics, such as pH, salt type, salt concentration and ionic heterogeneity in multicomponent adsorption systems, on the removal efficiency of humic and fulvic substances by activated carbon (McCreary and Snoeyink, 1980; Randtke and Jepsen, 1982; Weber et al., 1983). The purpose of this study is to examine the effect of a main component of domestic detergents, sodium triphosphate (STP), on the adsorptive capacities of powdered activated carbon (PAC) for commercially supplied humic acids, at different pH values in distilled water. Also, the effect of STP concentration and pH on the adsorption affinity of the PAC for humic acids, is discussed in relation with electrokinetic properties of carbon particles (zeta potential measurements).A first batch equilibrium study (Figs 1 and 2), showed an effective enhancement of adsorption capacity for humic acids as a function of STP concentration, in a non buffered media (pH of distilled water, close to 5.0). For example, visible absorption analysis of humic acids indicates an increase of 93% (500 mg l^?1 PAC) and 133% (1000 mg l^?1 PAC) in the carbon adsorption efficiency for a STP concentration from 0.2 to 1.0mM. A second batch equilibrium study (Figs 3 and 4) led to adsorption isotherms for humic acids in distilled water, as a function of STP concentration and initial pH value of the non buffered multicomponent system. Freundlich isotherms showed an increase in the adsorption capacity of the PAC for humic acids, with a decrease in pH and an increase in STP concentration. However, the adsorption capacity for humic acids is quite reduced at high pH values in presence of STP, in comparison with results obtained with distilled water.Electrokinetic measurements on PAC suspensions (Fig. 5) indicates that both humic acids and STP induce a negative variation of the zeta potential of carbon particles. In such a binary system, the zeta potential is a linear function of the pH; the negative surface charge of the carbon increasing with an elevation of pH (Fig. 6). Therefore, it appears that some adsorption of triphosphate polyanion from solution could occur, contributing then to the apparent negative surface charge of PAC particles.It has been previously showed that the type of anion in sodium salts, had little effect on the enhancement of adsorptive capacities of activated carbon for humic substances (Lafrance and Mazet, 1985), due to Na⁺ ions. However, adsorption of TP anions on the carbon surface may produce a source of repulsive charges, unfavourable to the co-adsorption of humic acids as the pH of the binary system reach more basic conditions. The influence of possible electrostatic interactions between adsorbates at the carbon surface, on the adsorption efficiency for humic acids, could then be studied by zeta potential measurements of PAC particles during the adsorption process.     

Adsorption des acides humiques sur charbon active en poudre. Influence du triphosphate de sodium

The use of activated carbon beds for the removal of natural humic and fulvic substances found in water supplies, has recently received considerable attention in water treatment operation (Lee et al., 1980; Le Cloirec et al., 1983). Moreover, the use of carbon adsorption for the reduction of haloform precursors (Anderson et al., 1981) and trihalomethanes produced by chlorination process, has contributed to a comprehensive investigation of adsorption characteristics of natural organic compounds (McCreary and Snoeyink, 1981). Many recent works showed the influence of adsorption system characteristics, such as pH, salt type, salt concentration and ionic heterogeneity in multicomponent adsorption systems, on the removal efficiency of humic and fulvic substances by activated carbon (McCreary and Snoeyink, 1980; Randtke and Jepsen, 1982; Weber et al., 1983). The purpose of this study is to examine the effect of a main component of domestic detergents, sodium triphosphate (STP), on the adsorptive capacities of powdered activated carbon (PAC) for commercially supplied humic acids, at different pH values in distilled water. Also, the effect of STP concentration and pH on the adsorption affinity of the PAC for humic acids, is discussed in relation with electrokinetic properties of carbon particles (zeta potential measurements).A first batch equilibrium study (Figs 1 and 2), showed an effective enhancement of adsorption capacity for humic acids as a function of STP concentration, in a non buffered media (pH of distilled water, close to 5.0). For example, visible absorption analysis of humic acids indicates an increase of 93% (500 mg l⁻¹ PAC) and 133% (1000 mg l⁻¹ PAC) in the carbon adsorption efficiency for a STP concentration from 0.2 to 1.0mM. A second batch equilibrium study (Figs 3 and 4) led to adsorption isotherms for humic acids in distilled water, as a function of STP concentration and initial pH value of the non buffered multicomponent system. Freundlich isotherms showed an increase in the adsorption capacity of the PAC for humic acids, with a decrease in pH and an increase in STP concentration. However, the adsorption capacity for humic acids is quite reduced at high pH values in presence of STP, in comparison with results obtained with distilled water.Electrokinetic measurements on PAC suspensions (Fig. 5) indicates that both humic acids and STP induce a negative variation of the zeta potential of carbon particles. In such a binary system, the zeta potential is a linear function of the pH; the negative surface charge of the carbon increasing with an elevation of pH (Fig. 6). Therefore, it appears that some adsorption of triphosphate polyanion from solution could occur, contributing then to the apparent negative surface charge of PAC particles.It has been previously showed that the type of anion in sodium salts, had little effect on the enhancement of adsorptive capacities of activated carbon for humic substances (Lafrance and Mazet, 1985), due to Na⁺ ions. However, adsorption of TP anions on the carbon surface may produce a source of repulsive charges, unfavourable to the co-adsorption of humic acids as the pH of the binary system reach more basic conditions. The influence of possible electrostatic interactions between adsorbates at the carbon surface, on the adsorption efficiency for humic acids, could then be studied by zeta potential measurements of PAC particles during the adsorption process.