有机高分子絮凝剂在污泥脱水中的应用

随着污泥成分的复杂化，与无机絮凝剂相比有机高分子絮凝剂展示出优异的脱水性能。文中阐述了近年来用于污泥脱水的各类有机高分子絮凝剂及其在污泥脱水中的最新应用研究、污泥脱水方法和影响污泥脱水性能的因素。对絮凝剂的选择和污泥处理方法进行总结，得出：(1)选择阳离子性基团总数大于阴离子性基团总数的一种或多种絮凝剂；(2)采用先加入含有阳离子(或阳离子性)基团的无机(或有机)絮凝剂，然后加入分子量较高的有机高分子絮凝剂(两性型、阳离子型、非离子型或阴离子型)的污泥脱水方法。     

Study on the Sedimentation Capability of Bauxite Flotation Concentrate

Fine bauxite flotation concentrate precipitated slowly, which significantly limited the capacity of the concentration plant. An effective disposal method was the addition of the flocculants to enhance the sedimentation capability of the concentrate. The sedimentation behaviors of bauxite flotation concentrates were investigated at different pH value and flocculate dosage. The effects of three types of flocculants (cationic, anionic and non-ionic polyacrylamide flocculants) as well as the molecular weight of anionic flocculants on the sedimentation of concentrate were studied. It is shown from the experimental results that at the pH 7.0, best sedimentation capability was reached when anionic polyacrylamide flocculant (molecular weight 14 million) was added; the optimal dosage was 30 g/t.     

A model of flocculation

The phenomenon of flocculation in liquid suspensions has a variety of applications, including mineral processing, treatment of industrial effluents, and municipal sewage sludge purification. Obtaining metals from ores would not be possible without the slurry processing route. Flocculants play here a double role: limiting environmental contamination and also slowing down depletion of raw materials — including potable, industrial and agricultural water. Development of better flocculants requires improved understanding of the mechanism of their action. We propose a model of flocculation based on the assumption that effective flocculants pervade large volumes of liquids in the suspensions. Since many flocculants are polymers, good flocculants according to the model should have large radii of gyration R_G. We therefore assume a connection between R_G and settling velocities y of particles out of suspension. Four different types of aqueous suspensions are studied, containing in turn silica, coal, Mn ore and Fe ore. A unique relationship is demonstrated between R_G and y for several polymeric flocculants in each type of slurry. For each suspension type the corresponding equation has the form y = aR_G^b, where the two parameters characterize the suspended particles and the liquid medium. While polysaccharides from natural sources are used as flocculants, we show how their cationization enhances the flocculation efficiency in all media we have studied. Large effects are achieved for the flocculating agent concentrations in the range of 6-9 ppm.     

Stability of Suspensions in the Presence of Nonionic Water Soluble Cellulose Polymers

Abstract

The effect of three groups of nonionic water soluble cellulose polymers, hydroxyethylcellulose, hydroxypropylcellulose and hydroxypropylmethylcellulose, on the stability or polystyrene latex suspensions and suspensions of the ibuprofen has been investigated.

Results of sedimentation volume, redispersibility and suspension appearance indicated that at low cellulose polymer concentrations suspensions were flocculated whereas at high concentrations suspensions were deflocculated. For hydroxyethyl-cellulose-ibuprofen suspensions flocculation was also observed at high concentrations. Flocculated suspensions obtained were not correlated with the energy diagrams. This was attributed to the flocculation energy involved in the interaction.     

Preparation and flocculation properties of cationic starch/chitosan crosslinking-copolymer

A novel flocculant (CATCS) based on corn starch and chitosan was prepared and its flocculation behaviors were studied. The synthesis conditions of CATCS were discussed and the production obtained was characterized using Fourier infrared spectra and scanning electron microscopy. Flocculation properties of the products were evaluated in terms of transmittance, removal of organic contaminant and solid suspending substances. Influences of temperature, pH and flocculant dosage on flocculation efficiency of CATCS were examined. CATCS had better flocculation performance at lower temperature for the wastewater investigated. CATCS showed better flocculation performance than cationic starch and chitosan in 5 g/L kaolin suspension trended to performance well in acidic and alkaline solution. The comparison of the flocculation performance between CATCS, Fe₂ (SO₄)₃ and polyacrylamide showed CATCS had much efficient flocculation performance. In addition, cationic starch was prepared from corn starch using microwave-assisted method.     

Magnetic composite Ca(OH)2/Fe3O4 for highly efficient flocculation in papermaking black liquor without pH neutralization

Industrially, lignin in pulp liquor not only obstructed the realization of value-added products, but also threatened the aquatic ecosystem. A magnetic composite Ca(OH)₂/Fe₃O₄, combining the eco-friendliness of Ca-based flocculants with the convenience of magnetic flocculation, was simply compounded to efficiently flocculate lignin from papermaking black liquor. Morphologic and structural features of the flocculant before and after flocculation were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM) and X-ray photoelectron spectroscopy (XPS). The flocculant Ca(OH)₂/Fe₃O₄ presented mesoporous and core-shell structure, which acted directly in the sodium lignin aqueous solution without pH neutralization, maintaining high lignin removal between 91% and 95%. Ca(OH)₂/Fe₃O₄ showed a wider salts (0–1 mol/L NaCl) and pH (9–12.5) tolerance. In actual pulp black liquor, Ca(OH)₂/Fe₃O₄ exhibited high removal of 90.16% and 85.93% for lignin and chemical oxygen demand (COD), respectively. The flocculation performance of Ca(OH)₂/Fe₃O₄ outdistanced that of the traditional flocculant polyacrylamide (PAM). It displayed magnetically separable with a good reusability. The removal of lignin could attain 90.54% even after 6 cycles. Charge neutralization, micro-bridging, destabilization and sedimentation were involved in the process of lignin flocculation. Consequently, Ca(OH)₂/Fe₃O₄ presented huge potential in papermaking black liquor treatment.     

Stability of Suspensions in the Presence of Nonionic Water Soluble Cellulose Polymers

The effect of three groups of nonionic water soluble cellulose polymers, hydroxyethylcellulose, hydroxypropylcellulose and hydroxypropylmethylcellulose, on the stability or polystyrene latex suspensions and suspensions of the ibuprofen has been investigated.

Results of sedimentation volume, redispersibility and suspension appearance indicated that at low cellulose polymer concentrations suspensions were flocculated whereas at high concentrations suspensions were deflocculated. For hydroxyethyl-cellulose-ibuprofen suspensions flocculation was also observed at high concentrations. Flocculated suspensions obtained were not correlated with the energy diagrams. This was attributed to the flocculation energy involved in the interaction.     

An Interpretation of the Sedimentation Behavior of Pharmaceutical Kaolin and Other Kaolin Preparations in Aqueous Environments

Abstract

The effect of flocculant materials on kaolin-water suspensions is reported using two kaolins. One of these is a pharmaceutical-grade kaolin and the other an industrial kaolin. These two systems serve as a model in a broader investigation which will systematically study the ancillary ingredients of pharmaceutical kaolin-based suspensions. These studies are based on concentrated suspensions where fall of particles is hindered and characterized by sedimentation “en bloc” with a sludge line serving as interface between the supernatent liquid and the settling suspension. It is shown that there is an optimum concentration of macromolecular flocculant which causes maximum flocculation. At higher concentrations of flocculant the system is stabilized. Two approaches are used to explain the results. The first represents the phenomenon as a modification of Stokes Law results. A correlation is found between the parameter A used as a characterization constant in Steinour's empirical relationship and the Richardson and Zaki exponent n. A theoretical justification of this relationship is provided. A permeability relationship is used in the second approach based on the application of permeability equations put forward by Kozeny-Carmen. The variable k in the resultant equation is shown in theory and in practice to have a minimum at some value of porosity determined by the nature of the concentrated suspension. This treatment is applied here to flocculated systems. The systems are found in general to show very high hindrance     

Effect of sodium dodecyl sulfate on flow and electrokinetic properties of Na-activated bentonite dispersions

The present study reports the effect of anionic surfactant sodium dodecyl sulfate (SDS, C₁₂H₂₅ OSO₃Na) upon the electrokinetic (electrophoretic mobility, zeta potential) and rheological (viscosity, yield value) properties of the Ca-bentonitic clay found in Turkey and its Na- activated form. The SDS dispersant was added in different concentrations in the range of 1 × 10⁻⁵−5 × 10⁻² mol/l. The results show that the viscosity and zeta potential values of bentonite dispersion are affected by the addition of anionic surfactant. The obtained data are analysed by considering the kind of exchangeable cations. Thixotropic property effect was observed in bentonite dispersions.     

Influence of cationic flocculant properties on the flocculation of yeast suspensions

In this study four different cationic polyelectrolytes of different molecular weight and charge densities were used to flocculate yeast suspensions to determine the effect of flocculant dose, molecular weight and charge density on the resulting floc size, morphology and charge. The zeta potential of the negatively charged yeast flocs was observed to increase with flocculant dose. As the flocculant dose was increased the charge of the floc was observed to reverse; the actual dose at which charge reversal occurs being dependent on the flocculant charge density and molecular weight. Floc size and morphology, measured with a video camera, showed that higher molecular weight flocculants produced larger flocs for the same dose. The results obtained here suggest that that flocculants may be screened by determining the charge, size and morphology of the resulting floc particles which is less time-consuming.     

In-line flocculation monitoring in a Hatschek machine for fibre–cement manufacture

The aim of this study is to obtain real-time information of flocculation processes in the fibre–cement manufacture through a soft sensor. This paper presents three different applied trials, carried out in different Hatschek machines, representing the main two industrial processes (air curing and autoclaving), in order to monitor the flocculant dosage changes, flocculant changes and the relationship between final product properties and flocculation. Three different anionic poly-acrylamides of low charge with different molecular weights were used as flocculants. The obtained results demonstrate that focused beam reflectance measurement (FBRM) is a valuable in-line sensor as well as a control and predictive process tool to monitor the flocculation processes in fibre–cement manufacture. Furthermore, a correlation between the sensor data (counts/s of particles between 50 and 86 μm) and the final product properties (density) was established, thus minimising the production of fibre–cement outside the intended specifications to achieve a better control on the final product quality.     

Dispersion of aqueous nano-sized alumina suspensions using cationic polyelectrolyte

In this paper, we investigate and report the effects of a cationic polyelectrolyte, polydiallydimethylammonium chloride (PDADMAC), on the stability of nano-sized alumina (α-Al₂O₃) suspension. Due to the static electrical repulsion interactions, PDADMAC show significant adsorption on α-Al₂O₃ only at alkaline pH. Considerable amount of non-adsorbed free PDADMAC exist in α-Al₂O₃ suspensions dispersed by PDADMAC at acidic and neutral pH. At 1.0 wt.% PDADMAC addition, α-Al₂O₃ became highly positively charged (>50 mV) in the entire pH range contrast with that the stability of α-Al₂O₃ suspension is enhanced only over the basic pH range in the presence of anionic polyelectrolyte. Free PDADMAC electrolyte in suspension results in increasing viscosity of α-Al₂O₃ suspensions dispersed with PDADMAC at alkaline and neutral pH. However, non-adsorbed free PDADMAC in suspension do not contribute to viscosity increase in acidic α-Al₂O₃ suspensions and α-Al₂O₃ suspensions dispersed with PDADMAC show the best flow behavior at acidic pH.     

Improvement of paint effluents coagulation using natural and synthetic coagulant aids

The coagulant iron chloride and the flocculants Polysep 3000 (PO), Superfloc A-1820 (SU) and Praestol 2515 TR (PR) have been used in this study to show the efficiency of coagulation flocculation process in the chemical precipitation method for the removal of organic and colouring matters from the paint industry wastewater. This study also includes the amount of produced sludge. The results indicate that FeCl(3) is efficient at pH range 8-9 and at optimal dose of 650 mgl(-1). Iron chloride allows the removal of 82% of chemical oxygen demand (COD) and 94% of colour. However, sequential addition of coagulant and polymeric additives enhance clearly pollutant removal and produces less decanted sludge compared to the results obtained when the coagulant is used alone. The removal efficiency of COD reaches 91% and that of colour 99%. Coagulation-biflocculation process is more effective than the coagulation-monoflocculation one. The sequential addition of iron chloride, Polysep 3000 (cationic flocculant) and Praestol 2515 TR (anionic flocculant) seems to be the most suitable combination for the treatment of the paint industry wastewaters.     

Manganese‐Based Na‐Rich Materials Boost Anionic Redox in High‐Performance Layered Cathodes for Sodium‐Ion Batteries

To improve the energy and power density of Na‐ion batteries, an increasing number of researchers have focused their attention on activation of the anionic redox process. Although several materials have been proposed, few studies have focused on the Na‐rich materials compared with Li‐rich materials. A key aspect is sufficient utilization of anionic species. Herein, a comprehensive study of Mn‐based Na_1.2Mn_0.4Ir_0.4O₂ (NMI) O3‐type Na‐rich materials is presented, which involves both cationic and anionic contributions during the redox process. The single‐cation redox step relies on the Mn³⁺/Mn⁴⁺, whereas Ir atoms build a strong covalent bond with O and effectively suppress the O₂ release. In situ Raman, ex situ X‐ray photoelectron spectroscopy, and soft‐X‐ray absorption spectroscopy are employed to unequivocally confirm the reversibility of O₂^2? species formation and suggest a high degree of anionic reaction in this NMI Na‐rich material. In operando X‐ray diffraction study discloses the asymmetric structure evolution between the initial and subsequent cycles, which also explains the effect of the charge compensation mechanism on the electrochemical performance. The research provides a novel insight on Na‐rich materials and a new perspective in materials design towards future applications.     

Chemically enhanced filtration and dewatering of narrow-sized coal particles

An experimental study of the filtration and dewatering of fine coal with and without additives was carried out. Filtration and dewatering behavior were determined using a vacuum filtration cell. The variables studied included the driving force, solids concentration, filter area, particle size and slurry pH. The effects of several flocculants, surfactants and hydrophobing additives (oils) on final moisture content of the filter cakes were determined. The investigations included determination of the rates of filtration and dewatering, assessment of the effects of additive type (anionic, cationic and nonionic), and establishment of optimum dosage of additives. Overall, it was found that the filtration and dewatering behavior were enhanced by increased driving force, higher initial slurry concentration, larger filtration area, larger particle size and lower slurry pH. Among surfactants and flocculating additives the anionic types were found to do the best job of filtration enhancement. At optimum dosages, the final cake moisture contents were reduced by 3.6% and 5.8% by weight using the appropriate surfactant and flocculant, respectively. However, the best filtration enhancements were achieved by addition of oils, which yielded cake moisture reductions of approximately 10% by weight.     

Effects of polyethyleneimine adsorption on rheology of bentonite suspensions

The influence of the cationic polymer, polyethyleneimine polymer (PEI) on the flow behaviour of bentonite suspensions (2%, w/w), was studied. XRD, zeta potential and adsorption studies were done together with rheological measurements. The addition of PEI at concentration ranges of 10^-5-4.5 g/l and their rheological properties and stability of bentonite suspensions were studied. The adsorption rates for the bentonite suspensions are very fast. The XRD results showed that the PEG molecules did not intercalate into the layers of the clay.     

Particle network re-structuring in highly-concentrated ceramic suspensions

In this study, the restructuring behavior of particle networks in highly-concentrated zirconia-wax suspensions as model suspensions is investigated in terms of temperature and solids concentration. The restructuring kinetics is analytically determined such that it can be formulated by a linear correlation between the relative viscosity (_r) of the suspensions and the logarithmic time (t) of isothermal annealing. Upon restructuring, a gelling point t _gel, defined as the time period of which the discrete particle networks in the pre-sheared suspensions are observed to start to form a continuous structure. Above t _gel, a sharp increase in suspension viscosity is commonly observed. The t _gel varies as a function of both temperature and solids concentration, The temperature effect provides valuable information for a better understanding of the restructuring behavior from an energy viewpoint. The influence of solids concentration, i.e., the t _gel decreased linearly with increasing solid concentration, suggests a stronger interparticle attraction that further accelerates flocculation.     

Synthesis,characterization and flocculation activity of novel Fe(OH)3–polyacrylamide hybrid polymer

A novel Fe(OH)₃–polyacrylamide inorganic–organic hybrid polymer (FHPAM) was synthesized via free radical solution polymerization initiated by a redox initiation system ((NH₄)₂S₂O₈–NaHSO₃) in an aqueous medium. Reaction parameters influencing the intrinsic viscosity and the yield of the hybrid polymer, such as initiator concentration, monomer mass fraction, temperature and reaction time were investigated and optimized. The results show that the maximum intrinsic viscosity and up to 94% yields of the hybrid polymer can be achieved using initiator concentration of 0.3% with acrylamide monomer mass fraction of 20% under solution polymerization at 40 °C for 7 h. The physicochemical properties of this hybrid flocculant were characterized with TEM, FTIR spectra, TGA, and conductivity. It was found that a chemical bond exists between Fe(OH)₃ colloid and polyacrylamide chains in the FHPAM. The application of the hybrid polymer for the treatment of 2.5 g L⁻¹ kaolin suspension indicates that it had an excellent flocculation capacity and its flocculation efficiency was much better than that of commercial available polyacrylamide (PAM) and polymeric ferric sulfate (PFS). The optimal conditions for the flocculation treatment of kaolin suspension were the FHPAM dosage of 40 mg L⁻¹ at pH 7.0. The thermodynamic parameters for the flocculation process were calculated based on a statistical model. Interpretation of the results was given.     

Complexes of An(VI) with Cyclobutanecarboxylic Acid Anions and Outer-Sphere Alkali Metal Cations

New complexes of hexavalent actinides with cyclobutanecarboxylic acid (Hcbc) anions, Na₄[NpO₂· (cbc)₃]₄·H₂O (I), K[NpO₂(cbc)₃] (II), Cs[NpO₂(cbc)₃] (III), and Cs[PuO₂(cbc)₃] (IV), cbc = C₄H₇(COO)^–, were synthesized and studied by single crystal X-ray diffraction. The structures of I–IV are based on the anionic complexes [AnO₂(cbc)₃]^– surrounded by alkali metal cations. The AnO ₂ ²⁺ cation in the anionic complex is bonded with three chelating C₄H₇COO^– anions, and the coordination polyhedron (CP) of An is a hexagonal bipyramid with the O atoms of the AnO ₂ ²⁺ cations in apical positions. The coordination number (CN) of the alkali metal cations in the structures of II–IV is the same and equal to 6; the coordination surrounding of the K⁺ and Cs⁺ cations is constituted by the O atoms of six C₄H₇COO^– anions. The crystal structures of II–IV are examples of cubic 3-connected networks (10,3) built of alkali metal and actinide cations. In the structure of I, there are four kinds of crystallographically different NpO ₂ ²⁺ and Na⁺ cations. The coordination surrounding of the NpO ₂ ²⁺ cations differs only in the conformational characteristics of the C₄H₇COO^– ligands. Four independent Na⁺ cations differ from each other in the structure of the coordination surrounding. The CPs of the Na(1) and Na(4) atoms can be described as distorted octahedra (CN 6); that of Na(3), as a trigonal prism (CN 6); and that of Na(2), as a tetragonal pyramid (CN 5) with one of the basal vertices occupied by the Ow(1) atom of a water molecule. In the structure of I, the configuration of the network formed by the Na and Np cations differs from the cubic 3-connected network found in the structures of II–IV.     

阳离子有机高分子絮凝剂的研究进展

絮凝沉淀法是广泛使用的水处理技术之一,而絮凝剂是絮凝法水处理的核心技术.与无机絮凝剂相比,有机高分子絮凝剂具有用量少、成本低、毒性小等优点,因此它的开发应用越来越受关注.而阳离子有机高分子絮凝剂由于带有可离解的阳离子更适合于水处理应用.本文介绍了阳离子聚丙烯酰胺类、天然高分子改性类、烷基烯丙基卤化铵类和环氧氯丙烷与胺反...