含沙高浊水最佳絮凝条件的确定

在含沙量为85kg／m^2的悬浊液中投加阳离子高分子聚合物,研究不同絮凝条件下絮体的自由沉速、结构密实程度、浑液面沉速与上清液余浊等的变化规律。利用“分维”作为定量控制参数研究含沙高浊水絮凝效果迭最佳时的絮凝条件（如搅拌速率、搅拌时间、高分子浓度等）,探讨了最佳絮凝条件下不同原始泥沙浓度对絮体分形结构的影响规律。实验得出85kg／m^2泥沙絮体结构密实性达最佳时的水力剪切强度Ct值存在两个临界值：快速絮凝阶段C1t1=2350,慢速絮凝阶段G2t2=12420。     

絮体性能及其工艺调控的研究与进展

絮体结构和强度特征是絮凝过程的重要参数。在简要回顾絮体分形结构研究的基础上，对絮体结构与强度的测定方法、絮体结构形成的影响因素及其工艺调控的研究进展进行了概括性介绍。结合部分实验研究，着重讨论了水力条件对于絮体性能的影响和絮体重组、历史的演化机理，结果表明，     

基于分形学的絮凝理论研究进展

絮凝过程中形成的絮体具有自相似性和标度不变性等特点,是一个典型的分形体。但传统的絮凝理论并未考虑絮体的分形结构,因而存在一定的缺陷。本文主要介绍了引入分形理论后,絮凝形态学和絮凝动力学的发展状况,重点阐述了絮体分形结构与其粒径、强度、密度、沉降速度等之间的关系,以及分形理论对Smoluchowski方程、传统絮体生长模式理论的改进。此外,本文同时指出分形学与絮凝理论的结合在很多方面尚未总结出系统的普适规律,尤其是非线性絮凝动力学仍需进一步完善。     

絮体性能及其工艺调控的研究与进展

絮体结构和强度特征是絮凝过程的重要参数。在简要回顾絮体分形结构研究的基础上,对絮体结构与强度的测定方法、絮体结构形成的影响因素及其工艺调控的研究进展进行了概括性介绍。结合部分实验研究,着重讨论了水力条件对于絮体性能的影响和絮体重组、历史的演化机理,结果表明,逐步增强的水力剪切条件有助于改善絮体的结构和强度：     

纳米SiO2与聚合铝PAC对含有机微污染物低浊水的絮凝形态学特性

在含有水溶性有机微污染物.十二烷基硫酸钠(SDS)的6NTU高岭土悬浊液中,投加纳米SiO2稳定分散液与聚合铝PAC进行动态混凝试验与静沉试验,借助图像分析技术与分形理论,探讨了纳米SiO2与PAC对含水溶性污染物低浊水的絮凝形态学特性.结果表明:絮体结构及其形成过程具有分形特征.参数"分维D"可用于定量表征分形絮凝体的形态学特性与分形结构的动态演变规律;絮凝体生长模式从开放的分枝状DLCA结构逐步向密实的RLCA构型演变.分形结构的不断演变引起絮体内部渗透性变化,絮体沉降性能逐步改善,分维值升高;SDS的存在对絮凝初PAC的混凝起阻碍作用,纳米SiO2能使颗粒生长的速度加快.纳米SiO2有助于有机物的去除,但对无机杂质的去除效果不如PAC;以纳米SiO2为助凝剂,能促使PAC絮体有效质量密度增加,使PAC对SDS的去除率提高,分维值增加.     

高分子聚合物在絮凝过程中作用及机理探讨

研究了高分子聚合物作为絮弟剂的使用特性以及高分子聚合物分子量,电荷密度,投加量的关系及对的影响。结果表明,电荷密度是阳离子型高分子聚合物对胶体颗粒絮凝作用的主要影响因素,阳离子型高分子聚合物的分子量大小在絮凝过程中起主要作用。另外。子量大的高分子聚合在絮凝过程中容易获得大且稳定的絮凝体。混合时间对絮体的表以及絮体尺寸大小,絮体稳定性也起着生作用。     

不同水处理工艺的混凝效果比较

该文以宁夏宁东地区黄河水为研究对象,考察了不同混凝条件（常规混凝沉淀池、微涡旋混凝沉淀池、反冲洗水回流沉淀池）下三种水处理工艺对混凝效能的影响。结果表明微涡旋改造有助于提高絮凝池的混凝效果,絮体的沉降性得到改善,“跑矾”现象得到缓解,絮体颗粒数目较折板絮凝池减少,沉淀池出水浊度明显降低;滤池反冲洗水回流技术可以有效地提高浊度的去除率以及改善絮体的沉降性能,且絮体颗粒数目较微涡旋絮凝池有明显减少,说明增加水体中颗粒数目可以有效地提高混凝效果;由分形维数的数据可以看出,微涡旋改造和反冲洗水回流可以明显提高絮体的分形维数,改善了絮体的沉降性。     

用分形理论评价超塑化剂对水泥絮凝结构影响

用光学显微镜对不同超塑化剂掺量情况下的水泥絮凝结构进行了研究,并结合分形理论对各絮凝形态进行定量评价.结果表明:絮凝颗粒为组成水泥浆体的基本单元;超塑化剂的加入可以有效破坏水泥絮凝结构;在最佳掺量范围内,随掺量增加,水泥絮凝结构的平面分形维数增大.     

无机悬浮颗粒的混凝特性和絮凝体形态学研究

研究了絮凝体的形成过程及其形态学特性.结果表明，无机悬浮颗粒体系的最佳混凝pH值在7～8之间，在低投药量时，压缩双电层和吸附电中和是主要的混凝机理，在高投药量条件下，则是卷扫絮凝起主导作用.絮凝体平均粒径和分形维数都随搅拌时间的延长而增大，并最终趋于稳定.在pH=7和以硫酸铝作为混凝剂的条件下，形成的絮凝体最大粒径为0.3mm，对应的分形维数在1.78左右.随着投药量的增大，絮凝体分形维数的变化较小，但絮凝体平均粒径显著增加;当投药量过高时，网扫絮凝作用下的絮体结构松散，抗剪切能力差，具有较小的平均粒径和分形维数.     

预臭氧氧化对聚硅酸铝铁絮凝效果及絮体形态影响研究

从絮体的分形结构、粒度、有效密度等微观特性出发,研究预臭氧氧化对聚硅酸铝铁絮凝效果和絮体形态的影响.结果表明,臭氧具有良好的助凝作用,并存在臭氧最佳投加量.一定浓度的臭氧能增大混凝过程中絮体的粒径,改变絮体的形态,使其更加规整,从而使分形维数发生变化.同时,适当的预臭氧氧化能增大絮体的有效密度,使絮体更加密实,提高沉降...     

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.     

磷矿酸解料浆与高分子絮凝剂形成的絮团特性研究

用光学连续摄像技术研究了不同絮凝条件下磷矿酸解渣与聚丙烯酰胺形成的絮团特性。实验结果表明酸解料浆与聚丙烯酰胺絮凝剂形成的絮团具有分形几何特征。应用分形理论得到絮团降落速度与絮团孔隙度和絮团密度的关系式。用激光粒度分布仪在线测定了流体力学条件对该体系团强度的影响。在湍流情况下絮团最大平均粒径取决于酸解渣原始平均粒径和体系的能量耗散。较大的絮团破坏主要以裂解为主,在最小的湍流漩涡区也存在相当程度的剥离破坏。试验发现絮团强度随聚合物分子量的增加而提高,对于获得最大平均粒径的稳定絮团存在最佳的絮凝剂加入量。．     

The Practical Application of Fractal Dimension in Water Treatment Practice–the Impact of Polymer Dosing

Abstract

The application of floc fractal dimension has been investigated in this work to determine if this parameter can have operational significance in water treatment. Natural organic matter suspensions were coagulated with aluminium sulphate and varying concentrations of a non‐ionic polymer. The fractal dimensions of the flocs formed were measured using light scattering and settling combined with image analysis. By using the correct methodology, optimum floc properties could be determined using the floc fractal dimension combined with the floc size and strength data.     

借助于分形维数研究混凝过程及其重要结论

混凝剂的性质和流体的紊流动力作用是决定混凝效果好坏的两个主要因素,在假定颗粒之间进行有效碰撞的基础上,本文从分形维数的角度提出了该过程的物理模型,并指出颗粒的表面能决定有效碰撞后的絮体分形维数。在实验研究的基础上,进一步指出：在药剂加入的初始阶段,其流体剪切力方式极其重要,控制其流体剪切力方式,就能最大程度降低颗粒的表面能,得到较高分形维数的絮体。     

分形理论在超塑化剂作用效果评价中的应用

应用激光粒度分析仪分析了掺加超塑化剂前后,水泥絮凝粒度分布情况;同时结合分形理论,计算出各掺量下的分形维数.得出结论:掺加超塑化剂后水泥絮凝结构被有效破坏,分形维数越大,减水效果越好.     

The structure and strength of depletion force induced particle aggregates

Aggregating fine particulate matter is common practice in many industrial solid-liquid separation processes. Data obtained in this work on dilute aqueous dispersions of model colloidal polystyrene latex spheres indicate that depletion flocculation, which uses non-adsorbing polymer, can yield very compact aggregates. Flocculation of the negatively charged latex particles was induced by the addition of a poly(acrylic acid) at pH 10. The structural compactness of the latex flocs formed in the dilute dispersions was characterised using small-angle static light scattering in terms of mass fractal dimensions. Rheological measurements on the concentrated latex dispersions in the presence of the non-adsorbing polyacid showed Bingham yield stress behaviour. Both the compactness and strength of the latex flocs were found to be significantly dependent upon the level of the polyacid, as well as the concentration of the initial particles. In particular, as the level of the polyacid was raised the floc compactness decreased, whereas its strength increased. They were both seen to level off at high polymer concentrations. Atomic force microscopy measurements were made at varying concentrations of the polyacid to provide a qualitative explanation of the observed floc structural behaviour of the dilute dispersions. By combining the fractal dimension and the Bingham yield stress we were also able to estimate the energy required to separate the flocs into single units in the concentrated dispersions. It was concluded that the interparticle interaction energy is the key to understanding the dependence of both the floc structure and strength on the polymer concentration.     

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.     

Optimising the dewatering behaviour of clay tailings through interfacial chemistry, orthokinetic flocculation and controlled shear

The effect of shear on dewatering behaviour and particle interactions of Na-exchanged smectite and kaolinite clay dispersions has been investigated at pH 7.5, using hydrolysable Ca(II) and Mn(II) ions as coagulants and high molecular weight anionic and non-ionic polyacrylamide (PAM A and PAM N, respectively) and polyethylene oxide (PEO) flocculants. Metal ion addition enhanced the flocculation performance by dramatically reducing the magnitude of the particle zeta potential and, in the case of smectite pulp, suppressing osmotic swelling. Under optimum orthokinetic flocculation conditions of controlled agitation rate and duration, PAM A and PEO-based flocs settled faster than those of PAM N whilst kaolinite pulps produced higher sedimentation rates than smectite pulps. The settling rates are nearly an order of magnitude greater than those observed under standard flocculant-pulp mixing/flocculation methods of inversion and plunging. The difference in the flocculant behaviour is attributed to the more expanded conformation of PAM A and PEO polymer chains in contrast to PAM N, whilst the lower yield stresses, reflecting inter-particle bridging and floc network structure strength that are conducive to faster clarification, were displayed by kaolinite pulps. Following shear, similar consolidation enhancement of ≈ 5-7 wt.% solid for both pulps was achieved at an optimum agitation range of 100-200 rpm. This was accompanied by decreased yield stress in the case of PAM A-based pulps, indicating non-reversible disruption of polymer mediated particle and floc network structure. In contrast, the yield stresses of PAM N and PEO flocculated dispersions indicated similar and stronger particle interactions, respectively, upon consolidation following shear. The findings show clear links between effect of shear, interfacial chemistry and polymer structure on pulp particle interactions and dewaterability.