Characterization and coagulation performance of polymeric phosphate ferric sulfate on eutrophic water

Polymeric phosphate ferric sulfate (PPFS),a new improved coagulation reagent,was prepared by polymeric ferric sulfate (PFS),Na2HPO4 and NaOH. The degree of iron polymerisation (Fepol) of PPFS was determined by means of the ferron-timed spectroscopy method. Furthermore,the effect of n(P)/n(Fe),alkalization degree,pH value,and PPFS dosage on the removal rate of eutrophic water turbidity and chl-a and ζ-potential of products were also investigated. The experimental results show that the best n(P)/n(Fe) of flocculation effect in stable product of PFFS is 0.3; the best alkalization degree of flocculation effect is 0.2,while the n(P)/n(Fe) is 0.3. Under the neutral and subalkalic (pH value is 7-8) conditions,PPFS achieves the best processing efficiency. PPFS has more excellent turbidity and higher chlorophyl removal rate by studying treatment eutrophic water in comparison with PFS.

Adsorption of Superplasticizers in Fly Ash Blended Cement Pastes and Its Rheological Effects

The adsorption of superplasticizers in fly ash blended cement paste and its rheological effects were investigated.It is shown that the absorption of superplasticizer on portland cement particles is very different from that on fly ash particles.The fly ash particles have smooth surfaces and are negatively charged,so its adsorption capacity is weaker than the portland cement particles.The amount of adsorbed SP in the fly ash blended cement paste depends highly on the replacement proportion of portland cement with fly ash,and to a much less extent on the nature of the fly ash.However,the amount of adsorbed superplasticizer does not correspond well the ζ-potential of the solid particles,due the strong adsorbing capacities of the Portland cement particles.When fly ash replaces portland cement in the paste,the rheological behavior is radically changed,which is closely related to the fineness and density of the ash.The packing and agglomeration of the solid particles are the controlling factors on the rheological parameters of the fresh paste,instead of the amount and type of adsorbed superplasticizer.

Application of Waste Liquids Containing Lignin from Pulp-producing Industry to CWM Preparation

Three kinds of craft waste liquids, which are by-products in the pulp industry and contain much lignin, were used as dispersing additives for preparing Horonai coal CWM(coal water mixture). The experiments showed that the CWM exhibited the lowest viscosity when it was diluted with an appropriate amount of water with the waste eiquids added. The experiments also indicated that the maximum coal concentration in the practically applicable CWMs whose apparent viscosity has to be below 1000 mPa·s increased from 56.5% to 62.5%(mass fraction), and 56.5% is the maximum coal mass fraction of the CWM prepared without additives. These data show the effectiveness of the waste liquids as the additives for preparing CWMs. The zeta potential of coal particles in the CWMs changed with the addition of lignin. From the change, the steric repulsion effect of the lignin adsorbed on the coal particles is concluded to be mainly responsible for the CWM dispersion. The waste liquids contain less sulfur than PSSNa(polystyrene sulfonate sodium salt), a typical dispersant which is currently used for preparing the commercial CWM, when the sulfur content in the unit mass of the solid matters within the waste liquids is compared with that in unit mass of PSSNa. This fact suggests that the waste liquids are more advantageous than PSSNa as far as air pollutants are concerned.

Chemical Structures and Adsorptive Behaviors of Superplasticizers on β-C_2S

The chemical structures of four types of superplasticizers （SPs） and their adsorptive behaviors on β-C2S were investigated. The adsorption properties of SPs on β-C2S were measured and the relationship between the adsorption quantity and the specific surface of β-C2S was analyzed. The experimental results show that the adsorption quantity increases with the surface area increase of β-C2S, but the adsorption quantity per surface area is similar, which means that the main adsorbent is β-C2S itself. Polycarboxylic ester （PCE） showed the highest adsorption amount on β-C2S, followed by β-naphthalene sulfonates （NSF） and formaldehyde-acetone condensates sulfonates （FAS）, amino sulphonate （AS） showed the least adsorption amount on β-C2S. PCE affected the surface potential of β-C2S particles in water differently in comparison with other types of SPs. The adsorption capacity of SPs on β-C2S is determined by factors such as molecular structure, functional groups and molecular weight of SPs.

Effect of Competitive Adsorption between Sodium Tripolyphosphate and Naphthalene Superplasticizer on Fluidity of Cement Paste

The adsorption amount, ξ-potential of cement particles and fluidity of cement paste were tested to research the competitive adsorption between naphthalene superplasticizer （FDN） and STPP. The experimental results showed that the presence of STPP could significantly improve the fluidity of cement paste and reduce the fluidity loss with FDN. There existed a competitive adsorption between STPP and FDN. STPP and calcium ions formed complexes; they preferentially adsorbed onto surface of cement particles and preempt adsorption points of FDN; and it reduced adsorption amount of FDN. In the absence of STPP, saturation adsorption amount of FDN was 5.93 mg/g; but when the dosage of STPP was 0.1%, it reduced to 4.3 mg/g （about 72.5%）. The adsorption amount of FDN was reduced by STPP, but ξ-potential of cement particles enhanced and fluidity of cement paste increased because of strong negative charge effect of the complexes. Adsorption of the complexes would delay Ca^2＋ into liquid and inhibit formation of active adsorption points. Then, content of FDN in liquid increased with the addition of STPP and ξ-potential of cement particles became stable. In this way, fluidity loss of cement paste reduced.

Spin-Dependent Electron Tunneling in ZnSe/Zn_(1-x)Mn_xSe Heterostructures with Double δ-Potentials

Using the matrix method, spin-dependent tunneling properties such as barrier transparency, the degree of resonance polarization, and tunneling lifetime of electrons are examined in the non-magnetic/diluted magnetic semiconductor heterostructure. The effects of the double δ-potential and the magnetic field are discussed on the transport properties of the electrons. The introduction of double δ-potential shifts the resonance peak of polarization to the higher energy value. Both height and position of the δ-potential influence the degree of resonance polarization in the considered heterostructure. The increasing magnetic field enhances the spin-polarization.

Manipulation of a temporal electron-spin splitter via aδ-potential in an embedded magnetic-electric-barrier microstructure

We theoretically explore the manipulation of a temporal electron-spin splitter by aδ-potential in an embedded magnetic-elec tric-barrier micro structure(EMEBM),which is constructed by patterning a ferromagnetic stripe and a Schottky-metal stripe on the top and bottom of an InAs/Al_(x)In_(1-x)As heterostructure,respectively.Spin polarization of the dwell time remains,even though aδ-potential is inserted by atomic-layer doping.Both the magnitude and sign of the spinpolarized dwell time can be manipulated by changing the weight or position of the 6-potential.Thus,a structurally controllable temporal electron-spin splitter can be obtained for spintronics device applications.

Surface properties of bacteria from activated sludge in relation to bioflocculation

Two bacterial stains were isolated from the activated sludge and identified as Leucobacter sp. and Alcaligenesfaecalis by 16S rDNA sequencing. Pure cultures of these two strains, representing well or poorly settled bacteria, were used to investigate the mechanism of bioflocculation in activated sludge. Based on the analyses of the characteristics of cells hydrophobicity, ζ-potential, flocculation ability and extracellular polymeric substance （EPS） composition under different growth stages, it was found that the ratio of cell EPS protein had the highly influence on ζ-potential and hydrophobicity, which were important factors to bioflocculation. Cellulase and Proteinase K could destroy the extracellular biopolymer and resulted in a decrease in the hydrophobicity and ζ-potential. However, in our study, the flocculation characteristics exhibited differently in relation to cellulase and Proteinase K. Flocculation of cells treated with cellulase and Proteinase K decreased sharply, and then recovered quickly in cellulase treatment, while cells treated with Proteinase K showed no sign of recovery. This reveals that the presence of protein in extracellular biopolymer plays an important role to the bioflocculation of cells.

Effects of fluoride on the removal of cadmium and phosphate by aluminum coagulation

This study focuses on the effects of p H and fluoride at different molar ratios of fluoride to Al（R F：Al） on the removal of cadmium（Cd^（2＋）） and phosphate by Al coagulation. Fluoride at R F：Al≥ 3：1 inhibits the removal of Cd over wide Al dose ranges from 5 to 10 mg/L as Al. The removal of phosphate decreases significantly at high R F：Al of 10：1 whereas at lowered R F：Al（i.e., ≤ 6：1）, an adverse effect is observed only at insufficient Al doses below 2 mg/L. Fluoride shows inhibitive effects towards the removal of Cd at p H 7 and 8 and that of phosphate at p H 6. Fluoride decreases the ζ-potential in both systems, and the decreasing extent is positively correlated to the elevated R F：Al. The Al fluoride interactions include the formation of Al-F complexes and the adsorption of fluoride onto Al（OH）3 precipitates, i.e., the formation of Al（OH）n F m. Al-F complex formation inhibits Al hydrolysis and increases residual Al levels, and a more significant increase was observed at lower p H. Al-F complexes at high R F：Al complicate the coagulation behavior of Al towards both negative and positive ionic species. Moreover, fluoride at low R F：Al shows little effect on Al coagulation behavior towards Cd^2＋and phosphate, and the spent defluoridation adsorbent,i.e., aluminum（Al） hydro（oxide） with adsorbed fluoride at R F：Al of below 0.1：1, may be reclaimed as a coagulant after being dissolved.

RESEARCH ON THE MECHANISM OF DIFFUSION AND MIXING IN THE MICROCHANNEL FLOWAND MICROMIXER

The mechanism of diffusion and mixing in the micro-channel flow was studied numerically and experimentally in detail. Based on the theoretical and computational results, the micro-mixers with high efficiency were designed. The conclusions drawn from this thesis are helpful for the practical usage.

Influence of suspension stability on wet grinding for production of mineral nanoparticles

Grinding behavior of nanoparticles in an attritor mill and the minimum achievable particle size are strongly influenced by the suspension stability. In the present work, suspension stability （i.e. ξ-potential） of nanoparticles was studied by measuring pH as a function of grinding time in the wet milling process. It was found that after a certain time in an attritor mill, there is no further size reduction and the average product particle size increases monotonically. One of the reasons is that the production of submicron particles leads to more particle-particle interactions and consequently pH of the suspension decreases with grinding time. Usually pH value is related to suspension stability and it can be enhanced by addition of NaOH solution. The maximum negative ξ-potential of -51.2 mV was obtained at pH of 12 for silica. The higher the ξ-potential with the same polarity, higher will be the electrostatic repulsion between the particles. Hence, the maximum electrostatic repulsion force was maintained by the adjustment ofpH value in wet milling. The experiments were conducted at different pH conditions which were maintained constant throughout the experiments and nanosized particles were obtained consequently.