阳离子絮凝剂的进展

介绍了国内外有机高分子絮凝剂的发展概况,对非离子、阴离子和阳离子聚丙烯酰胺絮凝剂作了对比,得出阳离子聚丙烯酰胺絮凝剂在水处理和污泥脱水方面具有独特效果.重点论述了几种阳离子聚丙烯酰胺絮凝剂的制备,介绍了阳离子聚丙烯酰胺絮凝剂在水处理和污泥脱水方面的应用,并对阳离子聚丙烯酰胺聚合的前景作了展望.     

城市生活污水剩余污泥深度脱水研究

通过污泥沉降比和泥饼含水率及脱水率的测定,分析絮凝剂和助凝剂对城市生活污水剩余污泥深度脱水性能的影响。对三氯化铝、阳离子聚丙烯酰胺、壳聚糖以及壳聚糖-阳离子聚丙烯酰胺复合絮凝剂的絮凝效果进行比较。结果表明,30 mg/L壳聚糖-阳离子聚丙烯酰胺复合絮凝剂的污泥絮凝效果最好。同时,在壳聚糖-阳离子聚丙烯酰胺条件下,对石灰、粉煤灰、十二烷基苯磺酸钠和硅藻土的脱水效果进行比较研究,结果表明,30 mg/L壳聚糖-阳离子聚丙烯酰胺复合絮凝剂,15%石灰、10%粉煤灰、pH为3,污泥含水率降低至51.36%。     

阳离子絮凝剂PDA的合成与应用——对再生造纸废水的污泥脱水处理

研究了阳离子聚丙烯酰胺絮凝剂PDA对一种废纸再生造纸废水中的污泥的絮凝脱水处理过程，探讨了絮凝剂PDA的投加量，电荷密度，平均相对分子质量对絮凝脱水效果的影响，并比较了各种不同絮凝剂的处理效果，研究结果表明，絮凝剂PDA的电荷密度越大，相对分子质量越高，其絮凝脱水效果越好，在与无机絮凝剂PAC复配使用的相同条件下，实验室自制的絮凝剂PDA的絮凝脱水效果优于其他作对比的市售多种阳离子聚丙烯酰胺类絮凝剂。     

阳离子聚丙烯酰胺反相胶乳的制备及其絮凝性能

以丙烯酰胺和甲基丙烯酰氧乙基三甲基氯化铵为单体,通过反相乳液聚合法制备了絮凝性能优异的阳离子聚丙烯酰胺反相胶乳。考察了乳化剂浓度、引发剂浓度、单体浓度及阳离子度对聚合物分子量和粒子粒径的影响,并研究了污泥pH值、污泥温度和聚合物用量等条件对絮凝性能的影响。得到的较佳条件是:乳化剂质量分数7.3%,引发剂质量分数0.02%、单体质量分数45%、阳离子度25%,在上述较佳条件下所得聚合物的黏均分子量为339.2万,粒子粒径均低于70 nm;污泥pH值为5～6,聚合物用量为0.057%的条件下污泥的絮凝率达62.2%,脱水率达82%。     

壳聚糖絮凝剂的投加量对污泥脱水性能的影响

通过污泥比阻的测定,分析絮凝剂剂量对污泥脱水性能的影响。同时对三氯化铝、阳离子聚丙烯酰胺、壳聚糖以及复合絮凝剂的絮凝效果进行比较。结果表明,无论是无机絮凝剂和有机絮凝剂都存在最佳剂量,小于或大于最佳投加量,絮凝效果都不好。阳离子聚丙烯酰胺(CPAM)、壳聚糖、三氯化铝的最佳投加质量浓度分别为0．2g/L、10g/L、35g/L。与三氯化铝相比,阳离子聚丙烯酰胺的药剂消耗量要低得多。壳聚糖与CPAM相比,在达到相同的絮凝效果时,壳聚糖的用量大于CPAM的用量。将壳聚糖与氯化铝复合,用两段法应用于污泥调理,研究这种复合絮凝剂的脱水性能,实验表明壳聚糖和三氯化铝复合,能大大提高污泥的脱水性能。     

阳离子型聚丙烯酰胺/十二烷基硫酸钠体系的研究

通过测量阳离子型聚丙烯酰胺/十二烷基硫酸钠(SDS)体系的动态表面张力、平衡表面张力及电导率,研究了聚丙烯酰胺的阳离子度的作用。聚电解质的阳离子度越大,溶液表面张力达到平衡所需的时间越短,平衡表面张力也越小。对于所研究的SDS浓度范围(<0.02mol·L-1),当聚丙烯酰胺浓度小于产生沉淀现象的浓度时,我们发现阳离子型聚丙烯酰胺/SDS溶液的电导率均比相应纯SDS水溶液的电导率大,且电导率随聚电解质离子度的增大而增加。结果表明,阳离子度即聚电解质链上的电荷数是降低SDS的表面张力、引起溶液电导率增大的主要因素。     

紫外光敏引发合成的P(AM-DAC)污泥脱水絮凝应用研究

采用紫外光敏引发聚合方式合成的较高相对分子质量和阳离子度的阳离子聚丙烯酰胺[P(AM-DAC)]产品作絮凝剂,进行污水处理实验。与紫外光敏引发合成的非离子型PAM和市售阳离子型聚丙烯酰胺对污泥水的絮凝效果进行了比较,探讨了絮凝剂相对分子质量、阳离子度、用量以及种类对污泥水絮凝效果的影响,最终确立了1.1×107相对分子质量、30%阳离子度、4 mg/L絮凝剂、搅拌次数15次为最佳实验条件。     

炼油废水生化污泥絮凝处理试验

针对炼油废水生化污泥含水率高、脱水困难等问题,进行了污泥絮凝处理试验研究。试验结果表明阳离子聚丙烯酰胺(CPAM)是炼油废水生化污泥处理的理想絮凝剂。生化污泥经絮凝处理后,污泥具有良好的沉降性能和脱水性能,过滤脱水后,污泥的含水率可从94%~99.8%降低到70%~85%,降低了污泥的含水率和体积,便于运输和最终处置。     

两性聚电解质在黄河高浊度水中的应用

本文合成了一系列不同阴、阳离子度的强碱弱酸型的两性聚电解质[丙烯酰胺(AM)-二甲基二烯丙基氯化铵(DMDAAC)-丙烯酸(AA)共聚物]。研究了阴、阳离子单体的配比对两性聚电解质分子量的影响;以及两性聚电解质阴、阳离子度对絮凝效果的影响。并将所合成的两性聚电解质作为絮凝剂,首次应用到黄河高浊度水的处理中。填补了国内两性聚电解质高分子絮凝剂应用于上水的空白。研究结果表明:在等电点范围内的两性聚电解质对黄河高浊度水的絮凝效果明显优于传统的非离子型、阳离子型及阴离子型絮凝剂。     

电化学与高分子复合絮凝剂联用对污泥的调理研究

在污泥处置过程中,污泥脱水已成为一个非常重要的环节,含水率是影响污泥处置效果与成本的重要因素。以污泥离心脱水率、毛细吸水时间(CST)、污泥上清液中的总溶解物、蛋白质、多糖、DNA含量、Zeta电势等为指标,研究了电化学与高分子复合絮凝剂——聚丙烯酰胺和壳聚糖联合作用对污泥脱水性的影响。结果表明,电化学与聚丙烯酰胺和壳聚糖联合调理污泥,电解15min,当聚丙烯酰胺与壳聚糖投加量分别为150和300mg/L时,污泥的毛细吸水时间降至19.6s,污泥离心后含水率为68.4%。电化学与高分子复合絮凝剂联合处理能有效破坏污泥絮体结构,污泥胞外聚合物(EPS)被分解,增加上清液的总溶解物、蛋白质、多糖、脱氧核糖核酸(DNA)含量。     

Sludge Dewatering and Aggregate Formation Effects through Taylor Vortex Assisted Flocculation

Abstract

For polymer induced flocculation processes, the effects of flow patterns in a gap of a conical stirrer on aggregate formation and subsequent sludge dewatering efficiency were analysed. Different flow regimes were identified by lab scale investigations with model substances and summarized in a Ta and Re number plane. An enhancement of sludge dewaterability for polymer induced flocculation processes was identified through post‐treatment of flocculated sludge aggregates by the specific flow pattern of stable and wavy Taylor vortices. Photo‐optical image analysis of flocculated aggregates shows a clear change of aggregate size distribution with less small particles during aggregate forming by Taylor vortices compared to classical flocculation procedure by stirrer. Results from technical scale dewatering analyses confirmed enhancement of sludge dewatering efficiency for six different dewatering machines using the identified wavy and stable Taylor vortex flow pattern regime.     

DEWATERING OF WASTE ACTIVATED SLUDGE VIA CENTRIFUGAL FIELD

While conducting centrifugal dewatering tests on waste activated sludge, this work considered how the rotational speed and the application of cationic polyelectrolyte flocculation affected the sludge. Increased rotational speed and/or conditioning the sludge to a charge neutralization point could enhance dewatering efficiency. A model was proposed to estimate the disruption energy exerted on the sludge body using centrifugation. Experimental results indicate that the disruption energy level provided by the centrifuge increases with rotational speed and decreasing water content in the filter cake. Moreover, polyelectrolyte flocculation may significantly reduce the disruption energy level of the water from sludge particles and the residual water contents at the end of the test.     

DEWATERING OF WASTE ACTIVATED SLUDGE VIA CENTRIFUGAL FIELD

ABSTRACT

While conducting centrifugal dewatering tests on waste activated sludge, this work considered how the rotational speed and the application of cationic polyelectrolyte flocculation affected the sludge. Increased rotational speed and/or conditioning the sludge to a charge neutralization point could enhance dewatering efficiency. A model was proposed to estimate the disruption energy exerted on the sludge body using centrifugation. Experimental results indicate that the disruption energy level provided by the centrifuge increases with rotational speed and decreasing water content in the filter cake. Moreover, polyelectrolyte flocculation may significantly reduce the disruption energy level of the water from sludge particles and the residual water contents at the end of the test.     

Comparison of initiation methods in the structure of CPAM and sludge flocs properties

Cationic polyacrylamides (CPAMs) synthesized by thermal, ultrasonic, microwave, and UV initiation were characterized through magnetic resonance hydrogen spectroscopy (¹H NMR), Fourier transform infrared spectra, scanning electron microscopy, and thermal gravimetric analysis. The CPAMs for flocculation and dewatering of alum sludge produced through drinking water treatment were evaluated based on the residual turbidity of the supernatant, dry solid content, mean volume diameter and floc size distribution, fractal dimension of the flocs, and zeta potential as a function of flocculant dosage. Comparisons of the characteristics and performance of CPAMs synthesized through different initiation methods were systematically conducted. Flocculation and dewatering test results demonstrated that CPAMs synthesized through microwave and UV initiation had better flocculation performance and dewatering capability than those synthesized through thermal and ultrasonic initiation. All four CPAMs exhibited a similar final floc size distribution but different mean volume diameters and floc structures. The fractal dimension of the flocs and the zeta potential were in the following order: CPAM3 (microwave initiation) > CPAM4 (UV initiation) > CPAM1 (thermal initiation) > CPAM2 (ultrasonic initiation). Discussions on fractal dimension and zeta potential indicated that the electrostatic patches model and adsorption/bridging effect mechanisms played the main role in the formation of sludge flocs. Lastly, microwave and UV initiation were found to be alternative and recommendable initiation methods for the synthesis of CPAMs with improved flocculation performance and sludge dewatering capability. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44071.     

Comparison of two cationic polymeric flocculant architectures on the destabilization of negatively charged latex suspensions

Flocculation studies between cationic polymers and oppositely charged colloidal particles are reported in which both flocculation kinetics and floc structures are systematically investigated. The flocculation rate constant, stability ratio and kinetics laws are experimentally determined using particle counting for two polymer architectures; a cationic linear polymer and a two-branched polymer. Comparisons are also made using NaCl at different ionic concentrations for the destabilization of the colloidal particles. Detailed measurements of electrophoretic mobility and kinetics rate constants on varying the polymer dosage are reported. Results suggest that the polymer architecture plays important roles on the polymer dosage for the rapid destabilization of the colloidal suspension. The branched polymer at optimal dosage exhibits the highest flocculation rate constant, whereas on the other hand, the linear polymer concentration range of flocculation is larger. In both cases, polymer flocculation is more efficient by a factor of 5-6 than charge screening effects due to the presence of salt. Analysis of the stability ratio indicates that tele-bridging flocculation and electrostatic forces dictate the stability of the charged latex particle suspension. It is shown that the fractal concepts which are valid for aggregation processes are also applicable here and branched polymers as well as linear polymers yield to the formation of compact flocs in comparison to those obtained with salt.     

Aggregate structures formed via a bridging flocculation mechanism

A high molecular weight cationic polyelectrolyte has been used to flocculate a colloidal dispersion of anionic polystyrene latex particles. The polymer used had a high charge density and the flocculation occurred at a solution pH where both the polymer and the particles were fully charged. Under these conditions, flocculation is expected to occur through a bridging flocculation mechanism. Low angle laser light scattering has been used to follow the flocculation process as a function of time; parameters of interest were the aggregate sizes, size distributions, and aggregate mass fractal dimensions. The light scattering measurements showed that the flocs formed had a mass fractal character. All the systems examined here were overdosed with respect to the optimum flocculation concentration of polymer. Under these conditions, decreasing the polymer concentration was seen to result in an increased flocculation efficiency. A secondary growth process was also observed whereby initially formed fractal aggregates can subsequently aggregate again. These larger aggregates are also expected to be mass fractals although this cannot be determined from the light scattering measurements due to the superposition of Fraunhofer diffraction effects. This type of fractal-in-fractal character is unusual.     

高分子絮凝剂特性对污泥调理和脱水效果的影响及在线絮凝检测技术应用研究

高分子絮凝剂品种及特性对污泥调理及脱水效果有很大影响,试验结果表明絮凝剂的相对分子质量是决定性因素,电荷特性影响较小。利用一种在线絮凝检测技术可连续检测污泥调理工艺中污泥颗粒絮凝过程,从而形成了一种全新的污泥絮凝检测方法,为污泥调理和脱水工艺的过程控制提供了可能性。     

A population balance model for flocculation of colloidal suspensions by polymer bridging

A detailed population balance model for flocculation of colloidal suspensions by polymer bridging under quiescent flow conditions is presented. The collision efficiency factor is estimated as a function of interaction forces between polymer coated particles. The total interaction energy is computed as a sum of van der Waals attraction, electrical double layer repulsion and bridging attraction or steric repulsion due to adsorbed polymer. The scaling theory is used to compute the forces due to adsorbed polymer and the van der Waals attraction is modified to account for presence of polymer layer around a particle. The irregular structure of flocs is taken into account by incorporating the mass fractal dimension of flocs. When tested with experimental floc size distribution data published in the literature, the model predicts the experimental behavior adequately. This is the first attempt towards incorporating theories of polymer-induced surface forces into a flocculation model, and as such the model presented here is more general than those proposed previously.     

Microelectrophoresis and electron-microscope studies with polymeric flocculants

Mechanisms for the stabilization and flocculation of colloids have been indicated by microelectrophoresis measurements and electron-microscope observations with model colloids and polymeric flocculants. Zeta-potential (ζ) changes and details of floc structure were observed with silica and polystyrene latex colloids. Bridging fibers of polyamine-type flocculants appear to extend radially from the colloidal particles and vary in thickness from 20 to 300 Å. Charge neutralization and bridging may function simultaneously. Incremental additions of cationic flocculants produce gradual reduction in the negative ζ, and maximum flocculation is observed near zero ζ. Subsequent addition of flocculant reverses the potential and finally effects redispersion of the colloid. If incipient charge reversal is produced with a relatively low molecular weight cationic polymer, large flocs may then be formed on the addition of a high molecular weight anionic flocculant. Direct addition of an anionic polymeric flocculant to a negatively charged colloid may raise the negative ζ to a surprisingly high value and may thus effect stabilization instead of flocculation of the colloid.     

Stability of pigment and resin dispersions in waterborne paint

The stability of a colloidal dispersion in a waterborne paint system, which consists of dispersed pigment and polymeric particles (dispersion or emulsion) along with a water-soluble acrylic polymer, was investigated. It was found that adsorption of appropriate ultrafine particles to the relevant particles could stabilize these particles against flocculation, leading to lower viscosity and yield value. The gloss and smoothness of the resultant films are notably improved. As the stability of the colloidal particles in an aqueous system is strongly dependent on the electrostatic effect, the effect was evaluated by measuring the ζ-potentials of the relevant colloidal particles. The ζ-potential is the electric potential on the outside of the surface layer, which includes the counterions around the particle. The ζ-potentials of a series of pigments in a solution of a water-soluble polymer were determined. By arranging the pigments according to their ζ-potentials, an order of basicity-acidity was established for pigments in a waterborne system, and the order was found to be different from that of solventborne systems, thought to be due to adsorbed counterions. After dispersing the pigment sufficiently with an appropriate polymer dispersant, ultrafine particles (of size under 0.05 μm) of lower refractive indexes were adsorbed to the surface of the pigments and polymeric particles. The adsorption layer of ultrafine particles can modulate the ζ-potentials of various colloidal particles to bring them into a certain range, so that the co-flocculation tendency between different colloids is remarkably diminished providing quite stable paint compositions by both electrostatic and steric hindrance effects.