Hydrolysis and coagulation behavior of polyferric sulfate and ferric sulfate

The hydrolysis behaviors of polyferric sulfate (PFS) and ferric sulfate (FS) under conditions similar to raw wastewater were investigated and the coagulation of biologically pretreated molasses wastewater using PFS and FS was evaluated by studying coagulation efficiency, zeta potential and microscopic surface morphology of flocs. Experimental results show that the hydrolysis behavior of PFS is different from that of FS on the basis of ferron assay. In the case of FS, fast-reacting Fe(III) polymers were the dominant polynuclear species while large fraction of slow-reacting iron polymers is present in PFS. Despite slightly fewer dosages of PFS required as compared to FS, there is no marked difference in the coagulation of molasses effluent between PFS and FS, especially at the optimum dosages. Both coagulants destabilize organic compounds predominantly through charge neutralization-precipitation mechanism. Hydrolysis rate of PFS in synthetic solution is appreciably different from that in raw wastewater. This may due to the effect of sulfate anion introduced as counter-ion as well as depolymerization of larger polymeric Fe(III) species by the organic ligands present in molasses effluent.

Evaluation of the Uncertainties Caused by the Forward Scattering in Turbidity Measurement of the Coagulation Rate

The forward scattering light (FSL) received by the detector can cause uncertainties in turbidity measurement of the coagulation rate of colloidal dispersion, and this effect becomes more significant for large particles. In this study, the effect of FSL is investigated on the basis of calculations using the T-matrix method, an exact technique for the computation of nonspherical scattering. The theoretical formulation and relevant numerical implementation for predicting the contribution of FSL in the turbidity measurement is presented. To quantitatively estimate the degree of the influence of FSL, an influence ratio comparing the contribution of FSL to the pure transmitted light in the turbidity measurement is introduced. The influence ratios evaluated under various parametric conditions and the relevant analyses provide a guideline for properly choosing particle size, measuring wavelength to minimize the effect of FSL in turbidity measurement of coagulation rate.

Clay surface modification and its coagulation of red tide organisms

Surface modification of montmorillonite by means of Mg2+ insertion reaction has been studied and a positively charged montmorillonite has been prepared. The effects of preparation temperature and Mg2+ concentration on the positive charge property of the clay and on the clay coagulating Heterosigma akashiwo have been studied. The results showed that the modified clay enhanced the coagulation and the used amount decreased to 1/5-1/10 of the original. The removal rates of Heterosigma akashiwo were correlated positively with positive charge on the clay in accordance with theoretical model.

Towards an Understanding of the Influence of Sedimentation on Colloidal Aggregation by Peclet Number

The Peclet number is a useful index to estimate the importance of sedimentation as compared to the Brownian motion. However, how to choose the characteristic length scale for the Peclet number evaluation is rather critical because the diffusion length increases as the square root of the time whereas the drifting length is linearly related to time. Our Brownian dynamics simulation shows that the degree of sedimentation influence on the coagulation decreases when the dispersion volume fraction increases. Therefore using a fixed length, such as the diameter of particle, as the characteristic length scale for Peclet number evaluation is not a good choice when dealing with the influence of sedimentation on coagulation. The simulations demonstrated that environmental factors in the coagulation process, such as dispersion volume fraction and size distribution, should be taken into account for more reasonable evaluation of the sedimentation influence.

Toward an understanding of the turbidity measurement of fleterocoagulation rate constants of dispersions containing particles of different sizes

Our previous studies have shown that the determination of coagulation rate constants by turbidity measurement becomes impossible for a certain operating wavelength (that is, its blind point) because at this wavelength the change in the turbidity of a dispersion completely loses its response to the coagulation process. Therefore, performing the turbidity measurement in the wavelength range near the blind point should be avoided. In this article, we demonstrate that the turbidity measurement of the rate constant for coagulation of a binary dispersion containing particles of two different sizes (heterocoagulation) presents special difficulties because the blind point shifts with not only particle size but also with the component fraction. Some important aspects of the turbidity measurement for the heterocoagulation rate constant are discussed and experimentally tested. It is emphasized that the T-matrix method can be used to correctly evaluate extinction cross sections of doublets formed during the heterocoagulation process, which is the key data determining the rate constant from the turbidity measurement, and choosing the appropriate operating wavelength and component fraction are important to achieving a more accurate rate constant. Finally, a simple scheme in experimentally determining the sensitivity of the turbidity changes with coagulation over a wavelength range is proposed.

Evaluation of influence of multiple scattering effect in light-scattering-based applications

The extinction cross sections of a system containing two particles are calculated by the T-matrix method, and the results are compared with those of two single particles with single-scattering approximation. The necessity of the correction of the refractive indices of water and polystyrene for different incident wavelengths is particularly addressed in the calculation. By this means, the volume fractions allowed for certain accuracy requirements of single-scattering approximation in the light scattering experiment can be evaluated. The volume fractions calculated with corrected refractive indices are compared with those obtained with fixed refractive indices which have been rather commonly used, showing that fixed refractive indices may cause significant error in evaluating multiple scattering effect. The results also give a simple criterion for selecting the incident wavelength and particle size to avoid the 'blind zone' in the turbidity measurement, where the turbidity change is insensitive to aggregation of two particles.

重力对溶液悬浮粒子聚集过程影响的布朗动力学模拟

采用布朗动力学的计算机模拟方法,研究重力因素对于稀溶液中悬浮粒子聚集过程的影响.通过在计算机模拟程序中加入和排除重力因素的影响,对不同重力条件下的粒子团数量随时间的变化曲线进行对比研究,得到了重力对溶液中的粒子团总数和不同大小的粒子团数量随时间变化的影响规律,可以总结为:在聚集阶段初期,重力不影响粒子的聚集,而在聚集阶段后期,重力加快了粒子的聚集.同时,从动力学分析的角度出发,对重力如何影响悬浮溶液中粒子聚集过程的机制也进行了更加深入的探讨. 

流体动力学作用对粒子聚集影响的布朗动力学模拟

采用布朗动力学模拟方法,研究了流体动力学作用对稀溶液中悬浮粒子聚集过程的影响.模拟中忽略了一个粒子同时与多个粒子碰撞聚集的可能,引入了前人有关两粒子间流体动力学作用影响的研究成果.模拟结果证实了流体动力学的作用在比较大的幅度上减缓了粒子的聚集过程,是导致粒子聚集速率的实验值低于Smoluchowski理论值的重要原因之一.另外,在分别加入和排除重力作用,以及考虑和忽略粒子间流体动力学作用在内的各种条件下模拟了粒子的聚集过程,得到了两种因素相互耦合作用时各因素对粒子聚集过程影响的结果,并从动力学的角度对这些因素的影响机制进行了相应的讨论.

Characterization of a fibrinogen-clotting enzyme from Trimeresurus stejnegeri venom, and comparative study with other venom proteases

Trimeresurus stejnegeri venom, which contains TSV-PA (a specific plasminogen activator sharing 60-70% sequence homology with venom fibrinogen-clotting enzymes), also possesses fibrinogen-clotting activity in vitro. A fibrinogen-clotting enzyme (stejnobin) has been purified to homogeneity by gel filtration and ion-exchange chromatography on a Mono-Q column. It is a single-chain glycoprotein with a mol. wt of 44,000. The NH2-terminal amino acid sequence of stejnobin shows great homology with venom fibrinogen-clotting enzymes and TSV-PA. Like TSV-PA, stejnobin was able to hydrolyse several chromogenic substrates. Comparative study of substrate specificities of stejnobin and other venom proteases purified in our laboratory was carried out on five chromogenic substrates. Stejnobin clotted human fibrinogen with a specific activity of 122 NIH thrombin-equivalent units/mg protein. However, stejnobin did not act on other blood coagulation factors, such as factor X, prothrombin and plasminogen. Diisopropyl fluorophosphate and phenylmethanesulfonyl fluoride inhibited its activity, whereas ethylenediamine tetracetic acid had no effect on it, indicating that it is a serine protease. Although stejnobin showed strong immunological cross-reaction with polyclonal antibodies raised against TSV-PA, it was interesting to observe that, unlike the case of TSV-PA, these antibodies did not inhibit the amidolytic and fibrinogen-clotting activities of stejnobin. (C) 1998 Elsevier Science Ltd. All rights reserved.

Blood cells as targets of snake toxins

Snake venoms are mixtures of enzymes and peptides which exert toxicological effects by targeting their substrates or receptors upon envenomation. Snake venom proteins widely affect vascular system including circulating blood cells, coagulation factors, an

An anticoagulant serine protease from the wasp venom of Vespa magnifica

Wasp is an important venomous animal that can induce human fatalities. Coagulopathy is a clinical symptom after massive wasp stings, but the reason leading to the envenomation manifestation is still not known. In this paper, a toxin protein is purified and characterized by Sephadex G-75 gel filtration, CM-Sephadex C-25 cationic exchange and fast protein liquid chromatography (FPLC) from the venom of the wasp, Vespa magnifica (Smith). This protein, named magnvesin. contains serine protease-like activity and inhibits blood coagulation. The cDNA encoding magnvesin is cloned from the venom sac cDNA library of the wasp. The deduced protein from the cDNA is composed of 305 amino acid residues. Magnvesin shares 52% identity with allergen serine protease from the wasp Polistes dominulus. Magnvesin exerted its anti-coagulant function by hydrolyzing coagulant factors TF, VII, VIII, IX and X. (c) 2008 Elsevier Ltd. All rights reserved.

Identification of novel semenogelin I-derived antimicrobial peptide from liquefied human seminal plasma

Semenogelin I (SgI) is one of the most abundant proteins in human seminal plasma. SgI plays a key role in sperm coagulation and spermatozoon immobilization. in addition, SgI and/or its proteolytic fragments are involved in regulating spermatozoon motility

CHARACTERIZATION OF OHS1, AN ARGININE/LYSINE AMIDASE FROM THE VENOM OF KING COBRA (OPHIOPHAGUS HANNAH)

In this paper, we present the results of purification and characterization of an arginine/lysine amidase from the venom of Ophiophagus hannah (OhS1). It was purified by Sephadex G-75 gel filtration and ion-exchange chromatography on DEAE-Sepharose CL-6B. It is a protein of about 43,000, consisting of a single polypeptide chain. It is a minor component in the venom. The purified enzyme was capable of hydrolysing several tripeptidyl-p-nitroanilide substrates having either arginine or lysine as the C-terminal residue. We studied the kinetic parameters of OhS1 on six these chromogenic substrates. OhS1 did not clot fibrinogen. Electrophoresis of fibrinogen degraded with OhS1 revealed the disappearance of the alpha- and beta-chains and the appearance of lower mel. wt fragments. OhS1 had no hemorrhagic activity. It did not hydrolyse casein, nor did it act on blood coagulation factor X, prothrombin and plasminogen. The activity of OhS1 was completely inhibited by NPGB, PMSF, DFP, benzamidine and soybean trypsin inhibitor, suggesting it is a serine protease. Metal chelator (EDTA) had no effect on it.

Polishing Treatment of Molasses Wastewater with Iron Salts: the Role of Counter-ions

The effect of counter-ions on the coagulation of biologically treated molasses wastewater using iron-based coagulants was investigated. Parameters such as removals of chemical oxygen demand (COD) and color, and residual turbidity, were measured to evaluate coagulation performance. Experimental results showed that ferric chloride and ferric nitrate were more effective than ferric sulfate at optimal dosages, achieving 89 to 90% and 98 to 99% of COD and color removals, respectively, with residual turbidity of less than 5 NTU. High-performance size exclusion chromatography (HPSEC) results revealed differences in the removal of the molecular weight fraction of organic compounds using iron salts. Scanning electron microscopy (SEM) showed randomly formed coagulated flocs characterized with irregular, sheet-like shapes. Nitrate and chloride counter-ions had similar effects on coagulation performance compared to sulfate. Both FeCl3 and Fe(NO3)(3) yielded better results than Fe(SO4)(2) under underdosed and optimum dosage conditions. Coagulation efficiency was less adversely affected in the overdosed regions, however, if sulfate rather than chloride or nitrate was present. Water Environ. Res., 81, 2293 (2009).