阴离子疏水单体改性的P(AM-co-DMC)的合成及絮凝性能

在少量阴离子疏水单体4-(ω-丙烯酰氧乙氧基)苯甲酸(PEBA)的参与下,合成了丙烯酰胺(AM)-丙烯酰氧乙基三甲基氯化铵(DMC)共聚物。通过表观黏度及芘探针发射谱测定了疏水改性P(AM-co-DMC)溶液的临界缔合浓度(CAC)。透射电镜观察表明:在水溶液中,当疏水改性P(AM-co-DMC)浓度高于CAC时,因静电及疏水作用可形成微球状缔合体。对高岭土悬浮液的絮凝表明,与普通P(AM-co-DMC)共聚物相比,疏水改性P(AM-co-DMC)具有较好的絮凝能力及较宽的窗体用量。pH对絮凝效果的影响表明,除疏水作用外,高分子链间的静电作用是提高絮凝效果的另一原因。     

Synthesis of cationic polyacrylamide via inverse emulsion polymerization method for the application in water treatment

In order to improve the flocculent efficiency of wastewater treatment, a cationic flocculant poly (acrylamide-[2-(methacryloyloxy) ethyl] trimethyl ammonium chloride) (P (AM-DMC)) (CPAM) has been synthesized successfully via an inverse emulsion polymerization. Acrylamide (AM) and [2-(methacryloyloxy) ethyl] trimethyl ammonium chloride (DMC) were served as monomers. The molecular structure of CPAM was characterized by Fourier transform infrared spectra (FT-IR) and ¹H nuclear magnetic resonance spectrum (¹H-NMR). The morphology of CPAM particles has been investigated by transmission electron microscope (TEM). Results showed that CPAM was the copolymer of AM and DMC and the particles of CPAM were uniform spheres (the size was about 200?nm). The synthetic conditions of CPAM have been studied and optimized by single-factor experiments. An optimized product was obtained at an intrinsic viscosity of 560?mL/g with a total monomer concentration of 25% and initiator concentration V50 of 0.2% (based on the total monomer mass). The amount of emulsion was 6% and the HLB (Hydrophile-Lipophile-Balance) of emulsion was 7.3. In addition, the flocculation property of CPAM was evaluated with kaolin suspension using jar test, and the result demonstrated that the flocculation property of CPAM performed better than kaolin flocculation.     

新一族疏水缔合聚丙烯酰胺NaAMC14S/AM与Gemini表面活性剂之间的相互作用

在水溶液中进行了表面活性单体丙烯酰胺基十四烷基磺酸钠(NaAMC14S)与丙烯酰胺(AM)的均相共聚合, 制备了具有微嵌段结构的疏水缔合聚丙烯酰胺NaAMC14S/AM, 合成了阳离子型Gemini表面活性剂二溴化-N,N′-二(二甲基十二烷基)己二铵(C12C6C12Br2), 采用表观粘度法和荧光探针法研究了共聚物NaAMC14S/AM与Gemini表面活性剂C12C6C12Br2的相互作用. 研究结果表明, 疏水缔合聚丙烯酰胺NaAMC14S/AM与Gemini表面活性剂C12C6C12Br2之间存在着很强的相互作用, 既存在静电相互作用, 又存在强烈的疏水相互作用, 表现在以下几方面: C12C6C12Br2的加入, 使共聚物NaAMC14S/AM在浓度小于其临界缔合浓度(cac)时即发生分子间的缔合; C12C6C12Br2在低于其临界胶束浓度时, 就与共聚物NaAMC14S/AM形成混合胶束; 当共聚物的浓度为0.30%(w)时, 随着C12C6C12Br2加入量的增多, 共聚物水溶液的粘度会发生大幅度的增加, 在最大值处粘度竟提高了3个数量级. 研究还发现, 共聚物NaAMC14S/AM与C12C6C12Br2之间的相互作用还与共聚物分子链中的疏水微嵌段含量有关, 疏水微嵌段含量越多, NaAMC14S/AM与C12C6C12Br2之间的相互作用越强, 溶液粘度增加的程度越大.     

Removal of Tannic Acid by Chitosan and N-Hydroxypropyl Trimethyl Ammonium Chloride Chitosan: Flocculation Mechanism and Performance

The cationic organic flocculant chitosan and its derivative, N-hydroxypropyl trimethyl ammonium chloride chitosan (HTCC), were used in the flocculation of tannic acid, the impurity widespread in Chinese medicine water extractions. This study aimed at investigating the flocculation performance and mechanism of chitosan and HTCC on the tannic acid colloidal particles. The results showed that chitosan and HTCC effectively flocculated the tannic acid solution and the mechanism was mainly for the adsorption bridging and charge neutralization by hydrogen bonding, electrostatic interaction, and hydrophobic interaction. Meanwhile, the charge neutralization of HTCC was stronger than that of chitosan. The optimal flocculation conditions of chitosan and HTCC on tannic acid were achieved.     

Flocculation Performance and Mechanism of Removing Pectin by N-hydroxypropyl Trimethyl Ammonium Chloride Chitosan

The cationic organic flocculant N-hydroxypropyl trimethyl ammonium chloride chitosan (HTCC) was used for flocculation of pectin, which was an impurity widespread in Chinese medicine water extractions, and the effects of the flocculant dosage, the pectin concentration, pH value, and the solution temperature on the flocculation efficiency were studied. FTIR spectra of pectin and its flocs were analyzed to determine the flocculation mechanism. The results showed that HTCC effectively flocculated the high-methoxyl pectin (HMP) and low-methoxyl pectin (LMP). The removal rate of HMP and LMP were above 85% and 90%, respectively. The flocculant dosage and pH value were the key influential factors. The pectin flocculation mechanism was mainly adsorption bridging and charge neutralization by hydrogen bonding, electrostatic adsorption, and hydrophobic interaction. The optimal flocculation conditions of HMP and LMP by HTCC were achieved.     

Influence of humic acid on the flocculation of clay

The aim of this study was to improve the flocculation of wastewater from gravel pits, especially the separation of the finely dispersed inorganic particles and the removing of humic acid. Clay was used as a model to investigate the influence of humic acid on the flocculation with two different types of polycation. The dependence of the sedimentation behaviour on time was investigated as well as the turbidity of the supernatant and the light absorption as a measure for humic acid removal. Bridging of particles remained the dominant mechanism of particle destabilisation by treating the clay in water with cationic polyacrylamides of very high molecular mass (CPAM). Poly(diallyldimethylammonium chloride) (PDADMAC) of lower molar mass (35 000 g/mol) was found to act by charge neutralisation. In this case the so-called flocculation window was very small. This behaviour is the same for systems containing humic acid. However, the need for cationic flocculant increases because humic acid as a weak polyanion can interact with the polycation. By using CPAMs with low charge this interaction does not play a significant role. The optimum flocculation concentration is relatively high. The flocs are larger and the velocity of sedimentation is higher than for the short-chain and highly charged polycation PDADMAC. However, because the latter is more effective in removal of humic acid at the point of optimum flocculation it is more advantageous to combine the highly charged polycation with a high molecular weight polyanion (dual system).     

A physico-chemical investigation of poly(ethylene oxide)-block-poly(L-lysine) copolymer adsorption onto silica nanoparticles

The adsorption behavior of poly(ethylene oxide)-b-poly(L-lysine) (PEO(113)-b-PLL(10)) copolymer onto silica nanoparticles was investigated in phosphate buffer at pH 7.4 by means of dynamic light scattering, zeta potential, adsorption isotherms and microcalorimetry measurements. Both blocks have an affinity for the silica surface through hydrogen bonding (PEO and PLL) or electrostatic interactions (PLL). Competitive adsorption experiments from a mixture of PEO and PLL homopolymers evidenced greater interactions of PLL with silica while displacement experiments even revealed that free PLL chains could desorb PEO chains from the particle surface. This allowed us to better understand the adsorption mechanism of PEO-b-PLL copolymer at the silica surface. At low surface coverage, both blocks adsorbed in flat conformation leading to the flocculation of the particles as neither steric nor electrostatic forces could take place at the silica surface. The addition of a large excess of copolymer favoured the dispersion of flocs according to a presumed mechanism where PLL blocks of incoming copolymer chains preferentially adsorbed to the surface by displacing already adsorbed PEO blocks. The gradual addition of silica particles to an excess of PEO-b-PLL copolymer solution was the preferred method for particle coating as it favoured equilibrium conditions where the copolymer formed an anchor-buoy (PLL-PEO) structure with stabilizing properties at the silica-water interface.     

Cationic-modified cyclodextrin nanosphere/anionic polymer as flocculation/sorption systems

Simultaneous removal of dissolved and colloidal substances has been a challenging task. The cationic-modified beta-cyclodextrin nanospheres synthesized in this work, in conjunction with a water-soluble polyacrylamide-based anionic polymer, potentially provide a novel approach to address the problem. The cyclodextrin was rendered cationic using (2,3-epoxypropyl)trimethylammonium chloride as a reagent. The cationicity of the modified cyclodextrin and the reaction between cyclodextrin and the reagent were characterized by electrophoresis measurement, polyelectrolyte titration, and NMR. As a dual-component flocculation system, the cationic cyclodextrin/anionic polymer significantly induced clay flocculation, lowering the relative turbidity of the clay suspension over a wide pH range. Meanwhile, as a nanospherical absorbent, the modified cyclodextrins exhibited strong affinity toward aromatic compounds via inclusion complex formation in the hydrophobic cavities, which was monitored by UV spectroscopy. These systems facilitated the simultaneous removal of dissolved and colloidal substances, which was unachievable previously. In addition, the interaction between anionic polymers and the clay particles pretreated with cationic cyclodextrin was investigated in order to reveal the flocculation mechanism.     

Improved dewatering behavior of clay minerals dispersions via interfacial chemistry and particle interactions optimization

Orthokinetic flocculation of clay dispersions at pH 7.5 and 22 degrees C has been investigated to determine the influence of interfacial chemistry and shear on dewatering and particle interactions behavior. Modification of pulp chemistry and behavior was achieved by using kaolinite and Na-exchanged (swelling) smectite clay minerals, divalent metal ions (Ca(II), Mn(II)) as coagulants and anionic polyacrylamide copolymer (PAM A) and non-ionic polyacrylamide homopolymer (PAM N) as flocculants. The pivotal role of shear, provided by a two-blade paddle impeller, was probed as a function of agitation rate (100-500 rpm) and time (15/60 s). Particle zeta potential and adsorption isotherms were measured to quantify the interfacial chemistry, whilst rheology and cryogenic SEM were used to investigate particle interactions and floc structure and aggregate network, respectively. Osmotic swelling, accompanied by the formation of "honeycomb" particle network structure and high yield stress, was produced by the Na-exchanged smectite, but not kaolinite, dispersions. Dispersion of the clay particles in 0.05 M Ca(II) or Mn(II) solution led to a marked reduction in particle zeta potential, complete suppression of swelling, honeycomb network structure collapse and a concomitant reduction in shear yield stress of smectite pulps. Optimum conditions for improved, orthokinetic flocculation performance of negatively charged clay particles, reflecting faster settling flocs comprised (i) coagulation, (ii) moderate agitation rate, (iii) shorter agitation time, and (iv) anionic rather than non-ionic PAM. The optimum dewatering rates were significantly higher than those produced by standard, manual-mixing flocculation techniques (plunging and cylinder inversion) commonly used in industry for flocculant trials. The optimum flocculation conditions did not, however, have a significant impact on the final sediment solid content of 20-22 wt%. Further application of shear to pre-sedimented pulps improved consolidation by 5-7 wt% solid. Higher shear yield stresses and greater settling rates were displayed by PAM A based than PAM N based pulps and this is attributed to the former's more expanded interfacial conformation and greater clay particles bridging ability. It appears that the intrinsic clay particles' physico-chemical properties and interactions limit compact pulp consolidation.     

Functional colloidal particles stabilized by layered silicate with hydrophilic face and hydrophobic polymer brushes

In this study, we describe a new strategy for producing narrowly dispersed functional colloidal particles stabilized by a nanocomposite with hydrophilic clay faces and hydrophobic polystyrene (PS) brushes on the edges. This method involves preparation of polymer brushes on the edges of clay layers and Pickering suspension polymerization of styrene in the presence of the nanocomposites. PS brushes on the edges of clay layers were prepared by atom transfer radical polymerization. X‐ray diffraction and thermogravimetric analysis results indicated that PS chains were grafted to the edges of clay platelets. Transmission electron microscope results showed that different morphologies of clay‐PS particles could be obtained in different solvents. In water, clay‐PS particles aggregated together, in which PS chains collapsed forming nanosized hydrophobic domains and hydrophilic clay faces stayed in aqueous phase. In toluene, clay‐PS particles formed face‐to‐face structure. Narrowly dispersed PS colloidal particles stabilized by clay‐PS were prepared by suspension polymerization. Because of the negatively charged clay particles on the surface, the zeta potential of the PS colloidal particles was negative. Positively charged poly(2‐vinyl pyridine) (P2VP) chains were adsorbed to the surface of PS colloidal particles in aqueous solution at a low pH value, and gold nanoparticles were prepared in P2VP brushes. Such colloidal particles may find important applications in a variety of fields including waterborne adhesives, paints, catalysis of chemical reactions, and protein separation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1535–1543, 2009     

Preparation of modified alginate nanoflocculant and adsorbing properties for Pb2+ in wastewater

A novel nano flocculant was prepared through the modification of sodium alginate. In the preparation partially oxidised sodium alginate reacted with triethylenetetramine (TETA) and then reacted with carbon disulfide. The structure of the flocculants was confirmed by elemental analysis, Fourier transform infrared and UV spectrophotometry. The flocculant showed nanoparticle sizes with diameters of 300–350 nm in aqueous solution, and became precipitates after flocculation with Pb²⁺ ions. The flocculant was employed to adsorb Pb²⁺ in wastewater, and the influence of flocculant concentration, flocculation temperature, pH, and time on the adsorption properties were investigated. The results showed that adsorption capacity of the flocculant for Pb²⁺ could reach up to 3.43 mmol g^–1, and the removal rate for Pb²⁺ was over 97%. The adsorption processes corresponded to pseudo second order kinetics and Langmuir isotherm model. The adsorption mechanism involved electrostatic attraction, chemical chelation, netting and sweeping actions.

     

Synthesis and flocculation performance of graft copolymer of <Emphasis Type="Italic">N</Emphasis> -vinylformamide and poly(dimethylaminoethyl methacrylate) methyl chloride macromonomer

 A comb-structured polymeric flocculant was synthesized by the aqueous copolymerization of N-vinylformamide (NVF) with poly(dimethylaminoethyl methacrylate) quats (methyl chloride) macromonomer. The effects of temperature and macromonomer concentration on the copolymerization kinetics were determined experimentally. The copolymerization reactivity ratio was measured to be 3.82 and 6.39 for NVF and macromonomers with 50 and 100 repeating units when copolymerized with NVF. The copolymer samples were also subjected to a flocculation performance test and were found to be more effective than linear random cationic copolymers in terms of cationic content, flocculation rate, final turbidity levels, and floc strength. Received: 11 June 2001 Accepted: 9 August 2001     

Kinetics of adsorption of high molecular weight anionic polyacrylamide onto kaolinite: the flocculation process

The adsorption kinetics of anionic polyacrylamide flocculant onto kaolinite clay are examined as a function of flocculant dosage and pH. Special attention has been given to the flocculation effect during the adsorption process and the resulting inhibition of further adsorption. At pH 8.5 the adsorption capacity of anionic polyacrylamide on kaolinite is low while at pH 4.5, the adsorption capacity increases. Flocculant adsorption has been shown to be related to the amount of available surface area, pH, flocculant dosage, and the resulting floc strength, which controls the rate of new surface area exposure and hence the continuation of further adsorption. At both pH 4.5 and pH 8.5, complete adsorption is achieved at low flocculant dosages and adsorption equilibrium is achieved at high flocculant dosages after 1 day. In contrast, at intermediate flocculant dosages adsorption equilibrium is not reached over a 7-day period, due to a continuously increasing surface area.     

Synthesis, characterization and flocculation performance of zwitterionic copolymer of acrylamide and 4-vinylpyridine propylsulfobetaine

A novel zwitterionic polyacrylamide AMVPPS copolymer containing sulfobetaine groups was synthesized by copolymerizing acrylamide (AM) and 4-vinylpyridine propylsulfobetaine (4-VPPS) in 0.5 mol/L NaCl solution with potassium persulfate (K₂S₂O₈) and sodium bisulfite (NaHSO₃) as initiator. The structure and composition of AMVPPS copolymer were characterized by FT-IR spectroscopy, ¹H NMR and elemental analyses. Thermal stability and solution properties of AMVPPS copolymer were studied by thermogravimetry analysis (TGA) and viscometry. Anti-polyelectrolyte behavior was observed and was found to be enhanced with increasing 4-VPPS content in copolymer. The flocculation performance for 2.5 g/L kaolin suspension and 2.5 g/L hematite suspension was evaluated by transmittance measurement and phase contrast microscopy. The effects of 4-VPPS content in the copolymer, intrinsic viscosity and the added salt on the flocculation performance were investigated. It was found that AMVPPS copolymer was a good flocculant for both anionic kaolin and cationic hematite suspensions and the flocculation performance of copolymer was much better than that of pure polyacrylamide (PAM). A very wide range of the optimum flocculation concentration, named as “flocculation window”, was found for both suspensions. These flocculation characteristics were mainly dependent on the charge neutralization, the intragroup conformation transition from water to NaCl solution and then the interchain bridging of the zwitterionic AMVPPS copolymer.     

Organo-modified cationic silica nanoparticles/anionic polymer as flocculants

The synthesis of quaternized silica nanoparticles and its application to fine clay flocculation were investigated. N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride was used as a cationic reagent to introduce quaternary amine groups onto the surfaces of silica nanoparticles via the formation of covalent bonds between the methoxy groups of the cationic reagents and the silanol groups in the silica surface. The zeta potential, zeta, and charge density of the silica particles modified under various reaction conditions were determined. Dynamic clay flocculation experiments using a photometric dispersion analyzer (PDA) showed that the cationic silica alone contributed little to the flocculation. However, the cationic silica, in conjunction with an anionic polymer of high M(w) and low charge density, led to a significant improvement in the flocculation of fine clay particles. The mechanism of flocculation was explored by a systematic investigation of interaction between cationic silica and anionic polymers as well as of their adsorption behavior on clay surfaces. The influence of factors such as pH and electrolyte concentration on clay flocculation was also investigated.     

Polyacrylamide Grafted Carboxymethyl Tamarind (CMT-g-PAM): Development and Application of a Novel Polymeric Flocculant

Water is scarce commodity now. Recycling of municipal wastewater, industrial and mineral processing effluents require treatment with the inorganic or organic flocculants. Both synthetic and natural polymers are used as flocculants. Natural polymers are biodegradable and are effective at very large dosages but are very shear stable. The synthetic polymers are highly effective flocculants at very small dosages and have high tailorability, but have poor shear stability. In the authors' laboratory, a novel polymeric flocculant has been developed by grafting polyacrylamide onto the backbone of carboxymethyl tamarind (CMT-g-PAM). Various grades were developed to optimize the best flocculant. The grafted polymers were characterized by various characterization techniques such as intrinsic viscosity measurement, FTIR spectroscopy, ¹³C-NMR spectroscopy, elemental analysis etc. The flocculation studies were carried out using turbidity test as well as settling test. The optimized CMT-g-PAM was then compared with some of the commercial flocculants available in national and international markets in colloidal suspensions and it has been found that our synthesized flocculant surpasses most of the commercial flocculants in performance.     

疏水化水溶性两性纤维素接枝共聚物与粘土的相互作用

运用紫外光谱法研究了疏水化水溶性两性纤维素接枝共聚物(羧甲基纤维素接枝丙烯酰胺及N,N 二甲基辛基(2 甲基丙烯酰氧乙基)溴化铵的共聚物, CGAO)在粘土上的吸附,考察了聚合物浓度、无机盐浓度、温度、 pH、 表面活性剂和粘土浓度等因素对CGAO在粘土上吸附量的影响,以及通过X射线衍射分析了CGAO在粘土上的吸附位置.结果表明， CGAO在粘土上的吸附规律与一般聚合物有很大差别,而且CGAO未深入到粘土晶层间,只在其表面吸附. 粘土与CGAO作用前后的粒度分析表明CGAO对粘土粒子有很好的桥接聚集作用. 扫描电镜分析显示粘土与CGAO作用后,其颗粒形态发生了显著变化.     

Cationic flocculants carrying hydrophobic functionalities: applications for solid/liquid separation

The flocculation behaviors of three series of polycations with narrow molecular weight distributions carrying hydrophobic substituents on their backbones [poly(N-vinylbenzyl-N,N,N-trimethylammonium chloride), poly(N-vinylbenzyl-N,N-dimethyl-N-butylammonium chloride), and poly(N-vinylbenzylpyridinium chloride)] were investigated in dispersions of monodisperse polystyrene latexes and kaolin. Apparently, the charge density of the polycations decreases with increasing substituent hydrophobicity and increasing molecular weight of the polyelectrolytes. The necessary amount of flocculant for phase separation in dispersions with high substrate surface charge densities increases with increasing hydrophobicity of the polyelectrolyte. Nevertheless, the introduction of hydrophobic functionalities is beneficial, resulting in a substantial broadening of the range between the minimum and maximum amounts of flocculant necessary for efficient flocculation (flocculation window). An increase in ionic strength supports this effect. When the substrate has a low charge density, the hydrophobic interactions play a much more significant role in the flocculation process. Here, the minimum efficient doses remained the same for all three polyelectrolytes investigated, but the width of the flocculation window increased as the polycation hydrophobicity and the molecular weight increased. The necessary amount of flocculant increased with an increase in particle size at constant solid content of the dispersion, as well as with a decreasing number of particles at a constant particle size.     

Study of pH-sensitive copolymer/phospholipid complexes using the langmuir balance technique: effect of anchoring sequence and copolymer molecular weight

The behavior of three copolymers of N-isopropylacrylamide (NIPAM), methacrylic acid (MAA), and hydrophobic moiety was studied at phospholipid monolayer/subphase interfaces. The hydrophobic moieties, N-terminal dioctadecylamine (DODA) and random octadecylacrylate (ODA), were used as anchoring groups. The interactions between a 1,2-distearoyl-sn-glycero-3-phosphatidylcholine (DSPC) monolayer and the copolymers were studied using the Langmuir balance technique. The effect of subphase pH, distribution of anchors along the copolymer chain, and copolymer molecular weight on the nature of the interactions between the copolymer chains and the DSPC monolayer were investigated. A first-order kinetics model was used to analyze the copolymers adsorption at the DSPC monolayer/subphase interface and allowed the interaction area between the copolymer chains and the DSPC monolayer, A(x), to be determined. The interaction area appears to depend on the subphase pH and the copolymer molecular weight. On decreasing pH, the interaction area of high molecular weight copolymers increases significantly; this is consistent with the copolymer chain phase transition from an extended coil to a collapsed globule while pH is lowered. In the latter conformation, strong hydrophobic attractive interactions between the copolymer chains and the hydrophobic part of the DSPC monolayer favor the copolymer intercalation, which could eventually provoke the phospholipidic layer destabilization or rupture.     

Flocculation of dilute titanium dioxide suspensions by graft cationic polyelectrolytes

The flocculation of a dilute titanium dioxide (TiO₂) suspension using homopolymers and graft copolymers of acrylamide (AM) and diallyldimethylammonium chloride (DADMAC) was investigated. The graft copolymers produced by γ-irradiating the mixtures of polyacrylamide (PAM) and polyDADMAC gave better flocculating performance than homopolymers, reflecting the higher fractions of large particles and bigger floc size. A kinetic delay in the onset of flocculation was observed after adding the copolymers in the dose range 5–30 [mg polymer]/ [g TiO₂]. Increasing dosage resulted in a longer delay period. No significant flocculation was observed when the dose was above 50 [mg polymer]/[g TiO₂]. This delay was interpreted in terms of the re-conformation of polymer chains driven by charge neutralization, between the positively charged polymer branches and the negative particle surface. Depending on the dosage used, the flocculation behavior of the graft copolymer has been suggested to be equilibrium and non-equilibrium flocculation. It was also observed that re-conformation is not affected by the ion strength of the media, but a strong shear force significantly reduces the chain reconformation time. Received: 9 April 1998 Accepted in revised form: 28 August 1998