Effect of viscosity, basicity and organic content of composite flocculant on the decolorization performance and mechanism for reactive dyeing wastewater

A coagulation/flocculation process using the composite flocculant polyaluminum chloride-epichlorohydrin dimethylamine (PAC-EPI-DMA) was employed for the treatment of an anionic azo dye (Reactive Brilliant Red K-2BP dye). The effect of viscosity (ηup), basicity (B = [OH]/[Al]) and organic content (W_P) on the flocculation performance as well as the mechanism of PAC-EPI-DMA flocculant were investigated. The ηup was the key factor affecting the dye removal efficiency of PAC-EPI-DMA. PAC-EPI-DMA with an intermediate ηup (2400 mPa.sec) gave higher decolorization efficiency by adsorption bridging and charge neutralization due to the co-effect of PAC and EPI-DMA polymers. The W_P of the composite flocculant was a minor important factor for the flocculation. The adsorption bridging of PAC-EPI-DMA with ηup of 300 or 4300 mPa.sec played an important role with the increase of W_P, whereas the charge neutralization of them was weaker with the increase of W_P. There was interaction between W_P and B on the removal of reactive dye. The composite flocculant with intermediate viscosity and organic content was effective for the treatment of reactive dyeing wastewater, which could achieve high reactive dye removal efficiency with low organic dosage.     

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.     

聚合铝与有机高分子复合絮凝剂的絮凝性能及其吸附特性

为探讨聚合铝与有机高分子在复合絮凝作用过程中的相互作用,选取４种典型有机高分子絮凝剂,研究聚合铝与阳离子型有机高分子和阴离子型有机高分子复合后的凝聚絮凝特征及其吸附特性．结果表明,聚合铝与阳离子型有机高分子复合能够使其絮凝效能相互促进,而聚合铝与阴离子型有机高分子的复合只有在药剂投加量达到一定值时才能对絮凝效能起促进作用．阳离子型有机高分子引入聚合铝后,使聚合铝的吸附量降低,而阴离子型有机高分子的引入使聚合铝的吸附能力大大增强,吸附量显著提高     

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.     

不同交联剂制备的环氧氯丙烷-二甲胺聚合物的结构及脱色性能

以环氧氯丙烷和二甲胺为原料,加入不同的胺类交联剂(乙二胺、二乙烯三胺和三乙烯四胺)合成出一系列环氧氯丙烷-二甲胺聚合物(EPI-DMA).研究了交联剂及用量对产品特性的影响;利用红外光谱(IR)和电子透射电镜(TEM)等现代分析仪器研究了EPI-DMA的结构及在水中的聚集形态;并通过烧杯实验研究了EPI-DMA对染料模拟废水和实际印染废水的处理效果.结果表明,交联剂的加入使EPI-DMA的粘度和阳离子度发生变化;不同交联剂制备的EPI-DMA的IR谱图相差不大,但在水溶液中的结构形貌不相同;EPI-DMA处理模拟活性艳红废水时以电中和和吸附架桥为作用机理,在处理还原大红废水时以电中和作用为主;在用EPI-DMA处理实际废水时脱色率和COD的去除率分别可达80%和60%.     

Removal of total cyanide in coking wastewater during a coagulation process：Significance of organic polymers

Whether a cationic organic polymer can remove more total cyanide （TCN） than a non-ionic organic polymer during the same flocculation system has not been reported previously. In this study, the effects of organic polymers with different charge density on the removal mechanisms of TCN in coking wastewater are investigated by polyferric sulfate （PFS） with a cationic organic polymer （PFS-C） or a non-ionic polymer （PFS-N）. The coagulation experiments results show that residual concentrations of TCN （Fe（CN）6^3-） after PFS-C flocculation （TCN 〈 0.2 mg/L） are much lower than that after PFS-N precipitation. This can be attributed to the different TCN removal mechanisms of the individual organic polymers. To investigate the roles of organic polymers, physical and structural characteristics of the floes are analyzed by FT-IR, XPS, TEM and XRD. Owing to the presence of N＋ in PFS-C, Fe（CN）3- and negative flocs （Fe（CN）63- adsorbed on ferric hydroxides） can be removed via charge neutralization and electrostatic patch flocculation by the cationic organic polymer. However, non-ionic N in PFS-N barely reacts with cyanides through sweeping or bridging, which indicates that the non-ionic polymer has little influence on TCN removal.     

Advanced lignin-acrylamide water treatment agent by pulp and paper industrial sludge：Synthesis, properties and application

A novel flocculant LA （lignin-acrylamide polymer）, which was used as aid for aluminum sulfate and polyaluminum chloride in this study, was prepared by grafting acrylamide onto lignin that deriving from pulp and papermaking sludge. Physicochemical properties of LA were measured by X-ray photoelectron spectroscopy and scanning electron microscopy. The experimental outcome indicated acrylamide was grafted onto the lignin backbone successfully. The effects of LA addition were evaluated on coagulation performance and floc characteristics as a function of aluminum （Al） dosage, such as floc size, growth rate, strength and recoverability. Effects of different dosing sequences, Al dosed first and LA dosed first, were also investigated. LA used as coagulant aid markedly enhanced the removal efficiency of turbidity and dissolved organic carbon, especially at low Al dosages. The dissolved organic carbon removal efficiencies of aluminum sulfate and polyaluminum chloride at the Al dosage range selected in this study were improved more than 30% and 5% by LA, respectively. LA dramatically enlarged floc size and it was in the order： Al dosed first 〉 LA dosed first 〉 Al. Floc strength and recoverability were also improved by LA. LA played a significant role in charge neutralization, adsorption and bridging in floc formation.     

四种絮凝剂对印染废水生化出水强化混凝处理的比较研究

印染废水污染严重,通常经生化处理后出水依然难以达标,还需进行深度处理。采用4种絮凝剂(无机多元聚硅酸盐、双氰胺-甲醛缩合剂、硫酸铝及这三种絮凝剂的复合剂)对某印染厂废水的生化出水进行深度处理,并且利用气相色谱质谱仪(GC-MS),分子荧光光谱仪(EEM)对出水前后水样中的有机污染物进行了检测,并利用MTS法对四种絮凝剂去除印染废水生化出水的细胞毒活性进行絮凝剂安全评估。结果表明:处理后的水质指标均达到国家Ⅰ级排放标准,且复合剂对印染废水生化出水的处理效果最好(COD去除率37.5%、TOC去除率71.6%、色度由40降至25)。EEM结果表明,复合剂不仅对蛋白质和腐殖酸类物质的去除能力显著高于其他三种絮凝剂,而且能够去除的难降解类有机物种类也属最多(包括去除三甘醇,磷酸三丁酯等5种主要污染物)。其产生良好效果的原因在于无机絮凝剂电中和能力和有机高分子絮凝剂吸附架桥性能的协同作用。此外,细胞毒活性实验表明,在本实验条件下添加硫酸铝使印染废水生化出水细胞毒活性增加10.5%,其他三种絮凝剂则都在不同程度上使细胞毒活性减小。     

城市景观水体混凝除藻过程对氮元素协同去除特性初探

以城市景观水体净化为目标,考察混凝除藻同时去除氮元素的特性和影响因素. 结果发现,水体内较高的DOC(溶解性有机质)含量会阻碍藻浊度的去除. 聚合氯化铝(PACl)以及PACl与硫酸铝(Alum)的复合剂(PACl+Alum)对藻浊度的去除效果均相对单独使用PACl或Alum较好,其中PACl+Alum对其他物质(如氮、DOC等)的去除效果也相对单独使用PACl或Alum更佳;在同样的最佳投药量时,低pH条件能获得更好的藻浊度去除率;对氮元素去除的进一步研究发现,DON(溶解性有机氮)的去除特征和过程与TN(总氮)非常一致,表明该水体TN的去除主体上是通过DON的去除实现的;低pH条件同样有利于氮和DOC的去除;但DOC与DON去除的不同步性,说明DOC中的DON成分和性质是非均一性的,是未来可进一步深入研究的重要方向.      

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.     

Experimental evaluation of eco-friendly flocculants prepared from date palm rachis

Sodium carboxymethylcellulose (CMCNa) is an anionic water soluble polyelectrolyte widely used in many industrial sectors including food, textiles, papers, adhesives, paints, pharmaceuticals, cosmetics and mineral processing. CMCNa was produced by chemical modification of cellulose, and represents many advantages: natural, renewable, non-toxic and biodegradable. In this study, di erent kinds of CMCNa, prepared from an agricultural waste date palm rachis, were tested as eco-friendly flocculants for drinking water treatment and their performances as flocculants in turbidity removal enhancement were assessed. The prepared materials were characterized by the degree of substitution (DS) and polymerisation (DP). The study of the e ect of some experimental parameters on the coagulation-flocculation performance, using the prepared materials combined with aluminium sulphate (as coagulant), showed that the best conditions for turbidity treatment were given for pH 8, coagulant dose 20 mg/L, flocculant concentration of 100 mg/L and stirring velocity (during the flocculation step) of 30 r/min. Under the optimum conditions, the turbidity removal using CMCNa, prepared from raw material, was about 95%. A comparison study between the flocculation performance of a commercial anionic flocculant (A100PWG: polyacrylamide) and that of the prepared CMCNa showed that the performance of the waste-based flocculant with a DS of 1.17 and a DP of 480 was 10% better than that achieved by the commercial one.     

生物絮凝剂用于给水混凝处理中浊度去除的研究

利用高岭土悬浊液和松花江原水作为研究对象,以混凝试验为基础考察了生物絮凝剂(BFs)对浊度的去除效果.结果表明,单独使用生物絮凝剂进行混凝处理在投药量5～19mg/L的范围内能够使高岭土溶液浊度去除84%,低于Al2(SO4)3(93%)和Fe2(SO4)3(94%). Zeta电位和混凝pH变化结果表明,生物絮凝剂的混凝效果主要受吸附架桥机理支配.向生物絮凝剂中投加少量的Al盐和Fe盐能够明显强化混凝效果,且在相同的混凝效果时Fe盐投加量小于Al盐投加量.这种强化作用主要是因为无机盐和生物絮凝剂的复合加强了电性中和与吸附架桥作用. Fe盐和生物絮凝剂复合使用可以在低投药量和中性pH条件下有效去除原水的浊度(94.6%).生物絮凝剂能够在较大的投药量范围内有效去除水源水中的颗粒物,形成的剩余污泥能够被自然降解;同时,由于不使用金属盐,大大降低了由于铝的积累而导致的致病风险,是一种环境友好的绿色絮凝剂.     

Effect of in-situ formed Al hydrates through long-term aging on enhanced particle destabilization by PACl coagulation

Aging of polyaluminum chloride (PACl) coagulants could significantly influence hydrolyzed Al speciation ruling coagulation performance. The goal of this study was to investigate Al species transformation through long-term aging and its impact on coagulation performance. Two kinds of commercial coagulants (PACl-1 and PACl-2) were stored for in-situ aging tests in six months to evaluate Al species variation with time and the performance of coagulation with natural turbid waters. The results showed that CaSO₄ precipitation easily occur in a commercial PACl coagulant with time as it contains SO₄^2? and Ca²⁺. It also activates the precipitation of gibbsite Al(OH)₃ in PACl with aging. Through 180 days aging, both monomeric Al (Al_a) and polymeric Al (Al_b) substantially transform into colloidal Al (Al_c) and precipitated for both PACl coagulants. At low turbidity (10 NTU), PACl-1 has a superior turbidity reduction rate than PACl-2, while PACl-2 performs a little better turbidity reduction at high turbidity (1000 NTU) regardless of aging time. With aging time, an obvious decrease in turbidity reduction for PACl-1 coagulation is observed at low turbidity of 10 NTU, while the improvement in turbidity reduction for PACl-2 coagulation by enhanced sweep flocculation can be achieved as Al_b mostly transform into Al_c after 150 days aging. It is concluded that dominant in-situ formed Al_c after a long time hydrolysis can improve PACl coagulation efficiency in turbidity reduction by enhanced sweep flocculation, especially for low turbidity water, but the increase in preformed Al_c in PACl would worsen particle destabilization after aging.     

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.     

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.     

不同铝聚合形态对聚合铝混凝效果的影响

通过氯化铝(铝单体或初聚物形态Ala)、高Alb含量聚合铝(中等聚合形态Alb)、高Alc含量聚合铝(铝溶胶等高聚合形态Alc)和工业PACl(不同聚合度铝的混合形态Alabc)对某水厂沉后水实际水样进行烧杯混凝实验,依据絮体生长状况、浊度、UV254、颗粒数和过滤指数等参数综合评价不同铝形态的混凝作用效果,从而得出铝的最佳混凝形态.结果表明,高Alb含量聚合铝对浊度去除较好;而高Alc含量聚合铝对于颗粒物和UV254的去除效果较佳.     

利用小角度激光光散射研究阳离子有机高分子絮凝剂的絮体粒径和絮体结构

利用小角度激光光散射在线监测技术研究了不同阳离子有机高分子絮凝剂对带负电荷的高岭土颗粒体系的絮凝动力学和絮体结构.对于高电荷密度的聚二甲基二烯丙基氯化铵(PDADMAC),由于分子量低其初始絮凝反应速度较慢,最终形成的絮体也较小.絮凝过程中,其絮体结构发生重组和排列,分形维数从1.83升高到2.09,所形成的絮体密实.对于低电荷密度的2种阳离子聚丙烯酰胺(CPAM),因其分子量大投药量高,絮凝反应速度较快;但其絮体的分形维数较小且在絮凝反应中基本保持不变,形成的絮体结构开放和松散.基于有机高分子对高岭土体系浊度和zeta电位的影响,结合絮凝动力学和絮体结构分析,结果表明,PDADMAC絮凝机理是电中和作用,而随着分子量的增加和电荷密度的降低,CPAM则主要通过吸附架桥作用产生絮凝.     

混凝-吸附处理黄河水及对氯消毒中氯衰减的影响

选用2种无机高分子混凝剂聚合氯化铁(PFC)和聚合氯化铝(PAC)处理黄河水,考察了混凝剂的投加量对浊度、UV254、DOC和高锰酸盐指数的去除效果,并结合混凝出水的Zeta电位分析其混凝机制.选择粉末活性炭与混凝联用,研究了混凝剂和吸附剂投加量以及二者的投加顺序对有机物去除效果的影响,并对混凝吸附后出水进行加氯消毒,考察水中残余氯随时间的变化.结果表明,2种混凝剂均有较高的浊度去除率(﹥90%).PAC对UV254、高锰酸盐指数和DOC的去除率分别为29.2%、26.1%和27.9%;PFC对三者的去除率分别为32.3%、23.3%和32.9%.PAC在混凝过程中,电中和作用占主导地位;PFC在混凝过程中,吸附架桥和电中和同时发挥作用.混凝-吸附联用处理黄河水样时,有机物的去除率随混凝剂和吸附剂投加量的增加而升高.先混凝后吸附工艺对UV254和DOC的去除效果优于先吸附后混凝工艺.先使用PAC混凝后吸附对UV254和DOC的去除率分别为95.2%和99.9%;对于PFC,先混凝后吸附对UV254和DOC的去除率分别为90.1%和99.9%.但是先投加粉末活性炭能提高矾花的沉降性能,且处理出水在保持持续消毒效果方面优于前者.     

聚合铝混凝过程研究:不同形态硅酸的影响作用

研究了不同形态硅酸对聚合铝混凝过程的影响作用 .实验结果表明经预制形成的具有不同形态分布组成的硅酸与聚合铝 ,在投加后相互间发生了十分复杂的物理化学作用 ,并受溶液pH值的影响 ,从而最终决定了混凝效果 .反应过程中所生成的形态产物及其物化特征 ,很大程度上取决于聚合铝碱化度以及所投加的Si Al比 .其中碱化度越高 ,最终产物所带电荷越高 .而不同硅酸所起影响作用分别取决于聚合程度 ,在与聚合铝反应过程中表现出一定的规律性 .单体硅酸与单体铝迅速发生较强的络合作用 ,抑制了多聚水解铝阳离子的形成 .聚合硅酸则倾向于与聚合铝形态相互作用形成一定的胶状化合物 ,从而在溶液中稳定存在 .对于胶体硅酸 ,在聚合铝作用下迅速凝聚形成更大的聚集体 ,在颗粒物间架桥形成粗大的絮体 .所得结果对混凝机理的解释与复合混凝剂的发展提供了一定的参考作用     

咪唑类季铵盐阳离子絮凝剂的制备及其在炼油厂废水中的应用

为提高环氧氯丙烷胺类絮凝剂的絮凝性能,以2-甲基咪唑为交联剂,以环氧氯丙烷、二甲胺为原料,制备了新型季铵盐阳离子絮凝剂——MZO,并对其进行红外、核磁表征. 采用MZO对抚顺炼油厂废水进行絮凝除浊试验,并与其他6种改性絮凝剂〔交联剂分别为HMTA(六次甲基四胺)、DET(二乙烯三胺)、TER(三乙烯四胺)、ED(乙二胺)、TE(三乙胺)、DAA(二烯丙基胺)〕进行了对比. 通过单因素试验研究MZO投加量、絮凝温度及其与PFC(聚合氯化铁)复配使用等因素对絮凝性能的影响,通过正交试验确定了其最佳使用条件. 结果表明:①MZO的阳离子度为41.1%,并非最高,但MZO对炼油废水的除浊率能达到98.8%,比其他6种改性絮凝剂提高了1.2%~20.0%不等;②单因素试验确定MZO的最佳絮凝温度为60 ℃,最佳投加量为30 mg/L,MZO与PFC的最佳复配比(质量比)为1∶40;③结合正交试验结果、生产及经济因素确定其最佳使用条件:絮凝温度为55 ℃,投加量为25 mg/L,复配比(质量比)为1∶20,在此条件下,复配后絮凝剂的除浊率达到98.2%.