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1.
The effect of shear on floc properties was observed through population balance to comprehend the mechanisms of flocculation, in particular the role of restructuring. Little fundamental attention has been given before to the shear influence responsible for creating compact aggregates, while the floc characteristics might differ in other conditions. It is crucial to understand how aggregates evolve to steady state, if their properties are to be ‘tailored’ to suit subsequent solid-liquid separation. From a previous experimental study (Langmuir 18(6) (2002) 1974), restructuring was observed to occur extensively in the flocculation of latex particles in couette-flow, and was proposed to be responsible for the decrease in floc size on their transition to equilibrium. On the other hand, flocs of larger primary particles were more susceptible to breakage, with densification occurring as a result of fragmentation and re-aggregation. Denser flocs were found when structural deformation dominated, particularly in the initial stage of the process, while comparatively tenuous ones were observed when formation and breakage kinetics were the governing mechanisms. The distinct manners in which aggregates of different primary particle sizes evolved with time, were replicated with a population balance that incorporated the floc structural variation; verifying that restructuring indeed played a crucial role under certain flocculation conditions. 相似文献
2.
Effects of a strong polyelectrolyte on the rheological properties of concentrated cementitious suspensions 总被引:1,自引:0,他引:1
Strong polyelectrolytes, referred to as superplasticizers, are known to improve the initial fluidity of concentrated cement suspensions. To quantify how the polyelectrolytes affect the fluidity, we have studied the effect of a strong anionic polyelectrolyte, melamine formaldehyde sulfonate (MFS), on the zeta potential of cement particles and on the steady-shear and low-amplitude rheological properties of cement suspensions. Adsorption of low concentrations of MFS onto the cement particles leads to an inversion in the sign of the surface potential, causing the electrostatically flocculated particles to become electrostatically dispersed and giving rise to a corresponding decrease in the steady-shear viscosity and storage modulus. At an intermediate MFS concentration, the steady-shear viscosity and the storage modulus each display a minimum. This concentration corresponds to that at which the zeta potential becomes constant. Larger concentrations of MFS result in an increase in the viscosity and storage modulus, which is attributed to depletion flocculation. These results thus relate the interaction between particles to the suspension fluidity through the analysis on the surface potential of particles and microstructure of suspension. 相似文献
3.
李旭 《江汉石油职工大学学报》2014,(1):42-44,56
胶凝酸主要由盐酸和胶凝剂配制而成,在低渗透碳酸盐岩地层压裂时,盐酸溶蚀地层,沟通缝隙。胶凝酸与地层岩石的化学反应在2小时内完成,返排液中的残酸用以NaOH为主的碱中和剂处理,通过中和、沉降、过滤、杀菌等一系列处理后回注地层。 相似文献
4.
Conditioning of either wastewater biosolids or water treatment residuals conventionally utilizes a single polymer to improve subsequent dewatering. The sequential addition of two polymers has been reported to enhance biosolids dewaterability, but comparable benefits have not been demonstrated for water treatment residuals. This paper evaluated the use of cationic and nonionic polymers, singly and in combination (dual), to investigate whether dual polymer conditioning of residuals offers any advantages, and to determine whether the results could be accommodated by current mechanistic understandings. For this purpose, lab-scale tests used capillary suction time (CST), supernatant viscosity, zeta potential, streaming current, turbidity, floc size, and rheometric analyses. Comparisons of CST and viscosity results for single and dual polymer additions indicated that dual polymer use gave moderately improved dewaterability, possibly due to the increased mixing utilized for dual polymer addition. Using a cationic polymer produced a less turbid supernatant. Zeta potential and streaming current were not good indicators of conditioning efficacy when a nonionic polymer was used. Rheometric analyses were only meaningful in one selected method for treatment of the data: the area under the rheogram up to a shear rate of 30?inverse?s. Overall, implementation of dual polymer use does not appear warranted. 相似文献
5.
A mathematical model was developed to estimate the efficacy of coagulation–flocculation treatment for removing neutral hydrophobic organic chemicals from raw drinking water. The model assumed that the only significant removal mechanism was the destabilization and settling of organic matter containing sorbed anthropogenic organic compounds. The model was validated with standard jar tests using compounds with a range of hydrophobicities (log?Kow = 1.89?to?5.48), including contaminant candidate list chemicals, pesticides, pharmaceuticals, and endocrine disrupting chemicals. Final concentrations of test compounds after coagulation and flocculation were in good agreement with model estimations for synthetic waters composed of Aldrich (Milwaukee, WI) humic acid solutions. The final compound concentrations in coagulated natural waters from two drinking water reservoirs were about 80% lower than those estimated with the model. Overestimations of treated water concentrations by the model were attributed to an increase in sorption by natural organic matter when coiled in aluminum hydroxide flocs, compared to sorption to dispersed natural organic matter in untreated water. 相似文献
6.
Emulsifying properties of two partially purified legumin and vicilin (PL and PV) and protein isolate (PPI) from dry pea seeds at various pH values (3.0, 5.0, 7.0 and 9.0) were investigated. The tested emulsion characteristics included droplet size, flocculation and coalescence indices (FI and CI), creaming index, as well as interfacial protein adsorption. Some physicochemical properties of these proteins, e.g., free sulfhydryl and disulfide bond contents, protein solubility (PS), surface hydrophobicity (Ho) and thermal stability (and denaturation), were also characterized. The results indicated that emulsifying ability and emulsion stability of various pea proteins considerably varied with the preparation process, protein composition and pH. Overall, all the pea proteins exhibited least emulsifying ability at pH 5.0 (around isoelectric point), and concomitantly, the resultant emulsions were most unstable against coalescence and creaming. The emulsifying ability of these proteins at pH 3.0 was generally better than that at neutral or alkali pH values, and among all the three proteins, PL exhibited highest emulsifying ability at this pH. The flocculated state and size of droplets in fresh emulsions did not directly affect stability of these emulsions against flocculation and coalescence (upon 24 h of storage), and even creaming (up to 7 days). Interestingly, the PL and PV exhibited much better creaming stability than PPI, at pH deviating from the pI. The emulsifying properties of these proteins were not only related to their PS and Ho, but also associated with the protein adsorption and nature (e.g., viscoelasticity) of interfacial protein films. These results can greatly extend the knowledge for understanding the emulsifying properties of pea proteins, especially the pH dependence of emulsion characteristics. 相似文献
7.
Mengyang Wang Shichao Bi Jianhui Pang Zhongzheng Zhou Di Qin Honglei Wang Xiaojie Cheng Xiguang Chen 《材料科学技术学报》2021,70(11):224-232
In the present research,nutrient broth(NB)medium was identified to be able to neutralize the antibac-terial activity of chitosan and its derivatives.Therefore,an improved test method independent of NB medium was proposed to precisely quantify the antibacterial effectiveness and efficiency of chitosan.The minimum bactericidal concentration(MBC)of chitosan was 60 μg mL-1 against S.aureus and E.coli,and 0.01%(w/v)chitosan could kill 100%of bacteria within 3 min.From another point of view,the neutralizing efficiency of NB could be tripled by adding 25 g L-1 of sodium chloride.Then the neutraliz-ing mechanism of NB medium was ascribed to flocculation between chitosan and protein.Adding extra sodium chloride could significantly reduce the size of floccules,and smaller floccules would lose the ability of binding with bacteria directly,showing higher neutralizing rate on the macro scale. 相似文献
8.
In this study, the extracellular polymeric substance of Scenedesmus quadricauda called EPS-S.q and its bioflocculatoin mechanism were investigated. Results showed EPS-S.q was successfully used as bioflocculating agent for S. quadricauda biomass harvesting and flocculation efficiency of up to 86.7% to S. quadricauda cells could be achieved in presence of Zn2+. EPS-S.q was the flocculating agent for self-flocculating microalga S. quadricauda and bioflocculation mechanism was polymer bridging. The sugar and protein mass fraction of dry EPS-S.q was sugar 56.7% and protein 41%. The infrared spectrum further indicated the presence of hydroxyl, carboxyl and amino groups. Moreover, pH decrease induced the flocculation of S. quadricauda and 78.4% of flocculation efficiency was the highest at pH 3. In addition, chemical flocculant FeCl3 was efficiently used for S. quadricauda harvesting and up to 96.8% of flocculation efficiency could be achieved for S. quadricauda culture with biomass concentration 0.21–0.39 g L−1 at pH 7. 相似文献
9.
用赤铁矿制备聚硅酸铁絮凝剂及应用研究 总被引:1,自引:0,他引:1
采用酸浸-催化氧化-水解-聚合工艺,进行了以低品位赤铁矿、废硫酸和硅酸钠为原料制备聚硅酸铁(PSF)絮凝剂的试验研究,结果表明,适宜的工艺条件为硫酸浓度5~6 mol/L,液固比4∶1,酸浸温度90 ℃,酸浸时间2~3 h,氧流量40 cm3/(min·L),Fe/Si摩尔比=2,硅酸活化pH值=3,硅酸活化时间25 min,陈化时间2 h。用所制备的PSF处理印染废水,并与聚合硫酸铁(PFS)和聚合氯化铝(PAC)进行比较,结果表明,在90 mg/L用量下,PSF可使废水中浊度、色度、SS和CODCr的去除率分别达到91.5%、87.8%、92.2%和78.5%,比相同用量下的PFS和PAC均分别高出10、24、14、18个百分点以上。 相似文献
10.