Preparation of high concentration polyaluminum chloride with high content of Alb or Alc

A novel membrane distillation concentration method was used to prepare high concentration polyaluminum chloride (PACl) with high content of Alb or Alc. 2.52 mol/L PACl1 with 88% Alb and 2.38 mol/L PACl2 with 61% Alc were successfully prepared. Three coagulants, AlCl3, PACl1 and PACl2 were investigated on their hydrolysis behavior and speciation under di erent conditions. The e ects of pH and dilution ratio on Al species distribution were investigated by ferron assay. Experimental result showed that pH had a significant e ect on Al species distribution for the three coagulants. Dilution ratio had little e ects on Alb and Alc distribution in whole dilution process except the beginning for PACl1 and PACl2. The results indicated that transformation of Al depends largely on their original composition. AlCl3 was the most unstable coagulant among these three coagulants during hydrolysis process. PACl1 and PACl2 with significant amounts of highly charged and stable polynuclear aluminum hydrolysis products were less a ected by the hydrolysis conditions and could maintain high speciation stability under various conditions.     

Application of a green coagulant with PACl in efficient purification of turbid water and its mechanism study

The applications of natural polymeric flocculants due to their green feature has been recently received much more attention. In this work, the combined usages of a cationic starch-based coagulant and polyaluminum chloride (PACl) were extensively evaluated for various addition sequences in the coagulation of both raw (surface water from the Jiuxiang River) and synthetic turbid water (two kaolin suspensions with different initial turbidities). Two typical cationic starch-based coagulants with different structures (St-G and St-E) were tried. In comparison to St-G, St-E and PACl used individually as well as St-G and St-E dosed after PACl, the combination of the starch-based coagulants fed before PACl showed higher turbidity removal efficiency, which featured not only less optimal doses of both inorganic and organic coagulants but also lower residual turbidity. On the basis of a detailed analysis of the particle size and its distribution in solution supernatants before and after coagulation by two starch-based coagulants and PACl, polymeric coagulants preferentially coagulate the small-sized colloids due to their distinct long-chain structures, but PACl preferentially coagulates the medium-sized ones. Thus, the medium-sized particles that were previously formed by the starch-based coagulants would be collectively and effectively removed by the subsequent addition of PACl. The addition sequence of the inorganic and organic coagulants in their combined usage is an important factor for improvement of the turbidity removal efficiency in practice.     

Hydrolysis of polyaluminum chloride prior to coagulation: Effects on coagulation behavior and implications for improving coagulation performance

The effects of polyaluminum chloride (PACl) hydrolysis prior to coagulation on both the coagulation zone and coagulation performance of a kaolin suspension were investigated by a novel jar test named the “reversed coagulation test”. The tests showed that PACl hydrolysis prior to coagulation decreased the performance of charge neutralization coagulation in the case of short-time slow mixing (10 min; G = 15 sec ?1 ) and increased the optimal dosage for charge neutralization and sweep coagulation. Moreover, the hydrolysis time had insignificant effects on the size and zeta potential of PACl precipitates and the residual turbidity of the raw water. However, PACl hydrolysis prior to coagulation and the size of PACl precipitates had a negligible effect on the performance of sweep coagulation.The results imply that, in practice, preparing a PACl solution with deionized water, rather than tap water or the outlet water from a wastewater treatment unit, can significantly save PACl consumption and improve the performance of charge neutralization coagulation,while preparing the PACl solution with tap or outlet water would not affect the performance of sweep coagulation. In addition, the optimal rapid mixing intensity appears to be deter-mined by a balance between the degree of coagulant hydrolysis before contacting the primary particles and the average size of flocs in the rapid mixing period. These results provide new insights into the role of PACl hydrolysis and will be useful for improving coagulation efficiency.     

复合混凝剂用于夏季太湖水混凝脱浊研究

用特征粘度系列化的聚二甲基二烯丙基氯化铵(PDM)与聚合氯化铝(PAC)复合得到稳定的复合混凝剂,用于夏季高藻太湖水强化混凝脱浊处理.通过混凝烧杯实验.考察了无机/有机复合比例、PDM特征粘度对脱浊效果及絮团沉淀性能的影响.结果表明,对浊度为30-33 NTU,温度为28～30℃,藻含量为2.6×107个儿的太湖水,在与某市水厂混凝强度相近的搅拌强度下.当达到该水厂2NTU沉淀池出水的余浊标准时,PAC需7.00 mg/L的投加量.质量复合比例为5:1、10:1、20:1的PAC(以Al2O3计)/PDM复合混凝剂所需PAC投加量随PDM特征粘度0.52、1.53、2.46 dL/g的增加分别为3.00-2.83 ms/L、3.50-3.49ms/L、5.37-4.67 mg/L,相对于PAC减少投加量57.14%-59.57%、50%-50.14%、23.29%-33.29%;作为深度处理的技术准备.当沉淀出水浊度要求提高至1NTU的情况下,复合药剂依然可发挥好的作用,PAC需10 mg/L的投加量,PAC(以Al2O3计)与PDM质量复合配比为20:1、10:1、5:1的复合混凝剂需8.33-3.91 mg/L的投加量,能比PAC减少投加量16.7%～60.9%.可见,PDM明显提高了PAC的混凝脱浊效果与沉淀性能,且PAC/PDM质量复合配比越低,PDM特征粘度越高,脱浊效果与沉淀性能越好.     

Al13形态在混凝中的作用机制

从铝的水解形态转化角度考察了铝盐在高碱度和高有机物浓度水体中的混凝行为.结果表明,铝盐的混凝效能是与混凝过程中的Al₁₃含量成正比.高投药量时氯化铝(AlCl₃)既可以有效调节水体pH值又能在混凝过程中原位水解产生较多的Al₁₃形态,因而混凝效能要高于聚合氯化铝(PACl).在铝盐混凝中,调节pH值到6～7之间可以控制铝形态分布从而达到提高混凝效能和减少残留铝的目的.在调节pH值强化混凝的方法中使用传统铝盐的效果要好于无机高分子絮凝剂.     

三种常见混凝机理为主导条件下絮体特性研究

以模拟低浊微污染水为原水,硫酸铝[Al2 (SO4)3]为混凝剂,考察了3种常见混凝机理(电性中和、吸附架桥和网捕卷扫)为主导条件下絮体的成长过程、二维边界分形维数(Dpf)和比表面积及其与混凝效果的相关性.结果表明:吸附架桥为主导机理下絮体最大增长速率S (0.951)最快,达到稳定后絮凝指数FI最大(3.7%),二维边界分形维数Dpf最大(1.587),絮体呈块状且絮体间出现孔状间隙,比表面积介于网捕卷扫和电性中和之间[网捕卷扫(83.646m2/g)>吸附架桥(98.808m2/g)>电性中和(116.046m2/g)];FI值、S及Dpf变化与浊度去除率相关性较好,其相关系数分别达0.979、0.982和0.963,同时比表面积大的絮体吸附容量大,有机物的去除率高.     

无机-有机复合混凝剂处理夏季引黄水库水的对比研究

合成了具有不同Fe(Al)/聚二甲基二烯丙基氯化铵(PDMDAAC)质量比的无机-有机复合混凝剂PFC-PDMDAAC和PAC-PDMDAAC,并对夏季引黄水库水进行混凝处理.考察了复合比例、投药量、pH值和投加方式对浊度、有机物和叶绿素-a的去除效果;并通过混凝过程中形成絮体的Zeta电位的变化分析了2种混凝剂的混凝机理.结果表明,无机-有机复合混凝剂处理夏季引黄水库水的效果好于2种单独成分的复配使用;复合比例对PFC-PDMDAAC和PAC-PDMDAAC处理夏季引黄水库水的效果影响较大,Fe(Al)/PDMDAAC质量比为4:1,投药量为4mg/L时混凝效果最好;与无机混凝剂相比,复合混凝剂的最佳pH值范围较广,可在5.0~8.0的pH值范围内取得良好的混凝效果;2种混凝剂相比,PAC-PDMDAAC对浊度和叶绿素-a的去除效果较好,而PFC-PDMDAAC对有机物的去除效果更佳.     

Nano-TiO2回收过程中SO42-对不同混凝剂混凝过程的影响

为了降低纳米TiO₂使用成本,采用不同混凝剂对纳米TiO₂悬浊液进行固液分离.通过考察浊度去除率、出水pH值的变化情况,并结合X射线光电子能谱（XPS）、傅里叶红外光谱（FTIR）、固体核磁（NMR）、扫描电镜（SEM）及能谱分析（EDS）表征,探究了纳米TiO₂回收过程中SO₄^2-对不同混凝剂混凝过程的影响.结果表明,当使用AlCl₃作混凝剂时（0.1mmol/L）,SO₄^2-浓度从0.0mmol/L增加到20.0mmol/L,浊度去除率降低了0.80%,絮体粒径从450μm下降到215 μm,而强度因子无明显变化.低聚合态的Al_a不与SO₄^2-结合,混凝过程中通过吸附架桥和网捕卷扫的作用形成大量无定形的Al （OH）₃.当使用Al₁₃作混凝剂时,再生长后絮体的粒径随着SO₄^2-浓度的增加而下降,S-O峰的红移证明有新的含S聚合物产生,Al 2p的峰均向较高的结合能移动证明生成的絮体不是Al （OH）₃.     

强化混凝与超滤组合工艺净化湘江水——采用不同混凝剂的比较

采用强化混凝-超滤组合工艺对湘江水进行了净化研究,通过加入不同的混凝剂[Al₂(SO₄)3·18H2O、FeCl₃]以及粉末活性炭(PAC),比较了三者对于湘江水的处理效果和对膜过滤性能的影响.结果表明,混凝剂的选择与用量对水中污染物质的去除和膜过滤性能有很大的影响.经过组合工艺处理后,系统出水的浊度小于0.1NTU,TOC小于2mg/L,铁、锰的含量低于0.1mg/L.     

Preferential binding between intracellular organic matters and Al13 polymer to enhance coagulation performance

Coagulation is the best available method for removing intracellular organic matter (IOM), which is released from algae cells and is an important precursor to disinfection by-products in drinking water treatment. To gain insight into the best strategy to optimize IOM removal, the coagulation performance of two Al salts, i.e., aluminum chloride (AlCl₃) and polyaluminum chloride (PACl, containing 81.2% Al₁₃), was investigated to illuminate the effect of Al species distribution on IOM removal. PACl showed better removal efficiency than AlCl₃ with regard to the removal of turbidity and dissolved organic carbon (DOC), owing to the higher charge neutralization effect and greater stability of pre-formed Al₁₃ species. High pressure size exclusion chromatography analysis indicated that the superiority of PACl in DOC removal could be ascribed to the higher binding affinity between Al₁₃ polymer and the low and medium molecular weight (MW) fractions of IOM. The results of differential log-transformed absorbance at 254 and 350?nm indicated more significant formation of complexes between AlCl₃ and IOM, which benefits the removal of tryptophan-like proteins thereafter. Additionally, PACl showed more significant superiority compared to AlCl₃ in the removal of < 5?kDa and hydrophilic fractions, which are widely viewed as the most difficult to remove by coagulation. This study provides insight into the interactions between Al species and IOM, and advances the optimization of coagulation for the removal of IOM in eutrophic water.     

Synchronous removal of CuO nanoparticles and Cu2+ by polyaluminum chloride-Enteromorpha polysaccharides: Effect of Al species and pH

Copper oxide nanomaterials have been extensively applied and can have serious impacts when discharged into the aquatic environment, especially when complexed with humic acid (HA) to form composite contaminants. As an innovative recycled coagulant aid, Enteromorpha polysaccharides (Ep) were associated with polyaluminum chloride (PACl) (denoted as PACl-Ep) to simultaneously remove CuO nanoparticles, Cu²⁺ and HA in this study. The influence of different Al species coagulants (AlCl₃, PACl_b and PACl_c) and water pH on coagulation performance, floc properties and reaction mechanisms was investigated in detail. Results showed that in the three PACl-Ep systems, PACl_b-Ep gave the highest removal efficiencies for turbidity and Cu²⁺, and the best UV₂₅₄ removal effect was reached by using PACl_c-Ep. Higher contents of Al_b and Al_c contributed to great coagulation performance because of their stronger bridging and sweeping effects. For all the Al species coagulants, alkalescent conditions were more conducive to removing Cu and HA compared to acidic conditions. Additionally, smaller and more agminated flocs with great recovery ability were formed by PACl_b-Ep and PACl_c-Ep systems (bridging and enmeshment effects cooperated with the chelated reticular structure formed by the Ep and Al species). Similarly, due to the increased hydrolysis and hydroxide precipitates, flocs formed under the condition of alkalescence were smaller, denser and stronger compared with weakly acidic conditions.     

阳离子聚电解质聚二甲基二烯丙基氯化铵的絮凝机理初探

以聚二甲基二烯丙基氯化铵PDADMAC(特性粘度分别为2.7,1.4,0.7)为絮凝剂,对比PAC和PFC,通过残余浊度、Zeta电位、FI絮凝指数的测定,研究了PDADMAC对高岭土悬浊体系(浊度分别为6000,1000,200和10 NTU)的絮凝特性,并对其絮凝作用机理进行了探讨.结果表明,PDADMAC的吸附构型决定其絮凝机理在较低初始悬浊物浓度下(200 NTU)为单个颗粒物表面吸附覆盖及其"吸附电中和"絮凝模型;在高浊条件下(＞1000 NTU)为单颗粒表面(Monomer)部分吸附覆盖及其"吸附架桥"絮凝模型.     

不同条件的底泥回流对强化絮凝的影响

为探究不同条件的回流底泥对絮凝强化的影响,采用智能光谱散射分析仪（IPDA）对絮凝过程进行连续监测。通过分析出水浊度和絮体生长曲线,考察了底泥投加量、存放时间和底泥pH对底泥强化作用的影响。结果表明:底泥投加量对于絮体生长FI值（絮凝指数）影响不大,回流单倍底泥时,出水浊度降至1.3 NTU,较常规絮凝下降38%;底泥存放时间越长,絮体生长FI值越小,存放时间<3 d的底泥可保证出水浊度维持在2.0以下;底泥pH为3.0时,出水浊度低至1.2 NTU,酸处理后的底泥,其絮体生长变化曲线不稳定,FI值呈明显震荡波动趋势。回流单倍底泥时,底泥能够强化絮凝的去浊能力,絮体颗粒保持较大尺寸。底泥形成24 h内回流,絮体颗粒之间产生的相互作用力最大,能保持底泥的最大活性。过高或过低的底泥pH导致絮凝效果变差,最适宜的底泥pH为3.0左右。     

Preparation and characterization of organic polymer modified composite polyaluminum chloride

Compared with traditional aluminum salts, polyaluminum chloride （PACI） has better coagulation-flocculation performance in turbidity removal. However, it is still inferior to organic polymers in terms of bridging function. In order to improve the aggregating property of PACl, different composite PACl flocculants were prepared with various organic polymers. The effect of organic polymer on the distribution or Al（Ⅲ） species in composite flocculants was studied using ^27TAl NMR and Al-ferron complexation methods. The charge neutralization and surface adsorption characteristics of composite flocculants were also investigated. Jar tests were conducted to evaluate the turbidity removal efficacy of organic polymer modified composite flocculants. The study shows that cationic polymer and anionic polymer have significant influences on the coagulation-flocculation behaviors of PACl. Both cationic and anionic polymers can improve the turbidity removal performancc of PACl but the mechanisms arc much different： cationic organic polymer mainly increases the charge neutralization ability, but anionic polymer mainly enhances the bridging function.     

Al(Ⅲ) speciation distribution and transformation in high concentration PACl solutions

Effects of Al(Ⅲ) concentration and pH on the speciation of Al(Ⅲ) in polyaluminum chloride (PACl) solutions especially on the Al13 fraction were investigated. A series of PACl samples were prepared over the range of Al(Ⅲ) concentration from 0.01 to 2.0 mol/L with the B (OH/Al ratio) value from 1.0 to 2.5 by forced hydrolysis of AlCl3. The samples were characterized by ferron assay,pH and 27Al NMR. It was shown that the Al(Ⅲ) concentration had a dramatic effect on the hydrolysis processes and the species distribution of PACl was in relate to the decrease of pH. The fraction of Al species, Alb (or Al13) decreased and Alc increased with increase of total Al(Ⅲ) concentration. Under the condition of Al(Ⅲ) 2.0 mol/L, B = 2.5, the pH value was 2.73 and no Al13 could be detected. During diluting and aging, the species distribution evolved. The Al13 could then be detected again and the amounts increased with time. If the diluted samples were concentrated by freeze dry at -35℃ or heating at 80℃, the pH value and Al13 content would decrease with the increased concentration. It demonstrated that the key factor for formation of Al13 in concentrated PACl was pH value.     

Al(Ⅲ) speciation distribution and transformation in high concentration PACl solutions

Effects of Al（Ⅲ） concentration and pH on the speciation of Al（Ⅲ） in polyaluminum chloride （PACl） solutions especially on the Al13 fraction were investigated. A series of PACl samples were prepared over the range of Al（Ⅲ） concentration from 0.01 to 2.0 mol/L with the B （OH/Al ratio） value from 1.0 to 2.5 by forced hydrolysis of AICl3. The samples were characterized by ferron assay, pH and 27^Al NMR. It was shown that the Al（Ⅲ） concentration had a dramatic effect on the hydrolysis processes and the species distribution of PACl was in relate to the decrease of pH. The fraction of Al species, Alb （or Al13） decreased and Al0 increased with increase of total Al（Ⅲ） concentration. Under the condition of Al（Ⅲ） 2.0 reel/L, B = 2.5, the pH value was 2.73 and no Al13 could be detected. During diluting and aging, the species distribution evoIved. The Al13 could then be detected again and the amounts increased with time. If the diluted samples were concentrated by freeze dry at -35℃ or heating at 80℃, the pH value and Al13 content would decrease with the increased concentration. It demonstrated that the key factor for formation of Al13 in concentrated PACl was pH value.     

阳离子絮凝剂HTCC与PAC复配对黄河兰州段水除浊性能研究

通过正交实验制备了阳离子絮凝剂壳聚糖季铵盐(HTCC),研究了壳聚糖季铵盐与聚合氯化铝(PAC)复配对黄河兰州段水的除浊效果,确定最佳复配比为m(HTCC)∶m(PAC)=1∶3。按该复配比,且在最佳投加量(1.25 mg/LHTCC+3.75 mg/L PAC)下,原浊为27.85～33.28 NTU的黄河水经处理后余浊<3 NTU。实验结果表明:pH对HTCC/PAC的除浊效果影响较大,当pH为7～9时,除浊效果均良好;而当pH为5～7时,投药范围内的最佳投药量提前,而除浊效率有所降低;沉降时间对HTCC/PAC的除浊效果无明显影响;HTCC/PAC以固-固方式复配的除浊效果比液-液方式复配的较差。     

强化混凝去除微污染湖泊水浊度及TOC的研究

通过烧杯混凝试验和动态连续混凝试验,就混凝剂种类、投药量、pH值、水温等因素,研究强化混凝对水中浊度和TOC去除效果的影响。试验结果表明:PAC最佳投量为30mg/L,浊度去除率为90.19%,TOC去除率为38.2%,水温高于20℃时,聚合氯化铝对浊度和TOC去除率分别高达84.95%、33.18%以上。虽然pH值是影响有机物去除的主要参数,动态连续混凝试验表明,不改变pH值,强化混凝工艺依然能极大地改善出水水质,滤后水质浊度为0.1NTU,TOC为6.23mg/L。     

强化混凝技术处理生活污水的试验研究

通过烧杯搅拌试验,以聚合氯化铝(PAC)和FeC13为混凝剂对华东交通大学排放口生活污水进行混凝处理研究,考察在不同混凝条件、混凝剂投加量、pH下浊度、COD、TP的去除率.研究表明:在最佳混凝条件下PAC投加量为105mg/L时浊度、COD、TP的去除率分别为96.2%、67.4%、94.8%;FeCl3最佳投加量为...     

Drinking water treatment using a submerged internal-circulation membrane coagulation reactor coupled with permanganate oxidation

A submerged internal circulating membrane coagulation reactor(MCR) was used to treat surface water to produce drinking water. Polyaluminum chloride(PACl) was used as coagulant,and a hydrophilic polyvinylidene fluoride(PVDF) submerged hollow fiber microfiltration membrane was employed. The influences of trans-membrane pressure(TMP), zeta potential(ZP) of the suspended particles in raw water, and KMnO_4 dosing on water flux and the removal of turbidity and organic matter were systematically investigated. Continuous bench-scale experiments showed that the permeate quality of the MCR satisfied the requirement for a centralized water supply, according to the Standards for Drinking Water Quality of China(GB 5749-2006), as evaluated by turbidity(1 NTU) and total organic carbon(TOC)(5 mg/L)measurements. Besides water flux, the removal of turbidity, TOC and dissolved organic carbon(DOC) in the raw water also increased with increasing TMP in the range of 0.01–0.05 MPa. High ZP induced by PACl, such as 5–9 mV, led to an increase in the number of fine and total particles in the MCR, and consequently caused serious membrane fouling and high permeate turbidity.However, the removal of TOC and DOC increased with increasing ZP. A slightly positive ZP, such as 1–2 mV, corresponding to charge neutralization coagulation, was favorable for membrane fouling control. Moreover, dosing with KMnO_4 could further improve the removal of turbidity and DOC, thereby mitigating membrane fouling. The results are helpful for the application of the MCR in producing drinking water and also beneficial to the research and application of other coagulation and membrane separation hybrid processes.