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In this study, the ultrasonic (US)-initiated template copolymerization was employed to synthesize a novel cationic polyacrylamide (CPAM) characterized by a microblock structure using dimethyldiallylammonium chloride (DMDAAC) and acrylamide (AM) as monomers, and sodium polyacrylate (NaPAA) as template. The polymers structure property was analyzed by Fourier transform infrared spectroscopy (FT-IR), 1 H nuclear magnetic resonance spectroscopy ( 1 H NMR) and thermogravimetric analysis (TGA). The results showed that a novel cationic microblock structure was successfully synthesized in the template copolymer of DMDAAC and AM (TPADM). Meanwhile, the analysis result of association constant (M K ) provided powerful support for a I Zip-up (ZIP) template polymerization mechanism and the formation of the microblock structure. The factors affecting the polymerization were investigated, including ultrasonic power, ultrasonic time, monomer concentration, initiator concentration, m AM :m DMDAAC and n NaPAA :n DMDAAC . The sludge dewatering performance of the polymers was evaluated in terms of specific resistance to filtration (SRF), filter cake moisture content (FCMC), floc size (d 50 ) and fractal dimension (D f ). Flocculation mechanism was also analyzed and discussed. The sludge dewatering results revealed that the polymer with the novel microblock structure showed a more excellent flocculation performance than those with randomly distributed cationic units. A desirable flocculation performance with a SRF of 4.5 × 10 12  m kg -1 , FCMC of 73.1%, d 50 of 439.156 µm and D f of 1.490 were obtained at pH of 7.0, dosage of 40 mg L -1 and the molecular weight of 5.0 × 10 6  Da. The cationic microblock extremely enhanced the polymer charge neutralization and bridging ability, thus obtaining the excellent sludge dewatering performance., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Flocculation is one of the commonly used sludge conditioning methods in water supply plants, which can improve the sludge dewatering performance by reducing the specific resistance of sludge (SRF), decreasing the amount of sludge, and finally lowering the transportation cost and subsequent disposal cost of sludge. Therefore, it is particularly important to develop new and efficient flocculants. In this paper, the template copolymer of acryloxy trimethylammonium chloride (DAC) and acrylamide (AM) was successfully synthesized by microwave-template copolymerization (MV-TP) using sodium polyacrylate (NaPAA) as template. The template copolymer was analyzed by infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance hydrogen spectroscopy (1H NMR), and scanning electron microscopy (SEM). It was found that this template copolymer had obvious cationic microblock structure. In addition, the test results of association constant (KM) and polymerization kinetics showed that the MW-TP was assigned to free radical initiated polymerization and the polymerization mechanism was I Zip-up (ZIP). It confirmed the formation of cation fragment structure again. Due to its dense positive charges in this new cationic microblock structure, it greatly improved the functions of electric neutralization, electrical patching, and adsorption bridging. The cationic fragment structure in the template copolymer could help to generate large and dense floc structure and form stable drainage channels. Under external pressure, these large and compact floc structures had greater compressive resistance, which avoided deformation and blockage of drainage channels and voids. It was beneficial to reduce SRF and evidently enhanced sludge dewatering performance. [ABSTRACT FROM AUTHOR]

Novel adsorbents, poly([2-(methacryloxy)ethyl]trimethylammonium chloride) modified magnetic chitosan particles (DMCPs), were synthesized via free radical polymerization and applied to adsorb Cr(VI) from aqueous solution. The effects of pH (2–11), Cr(VI) concentration (10–200 mg/L) and contact time (0–420 min) on the adsorption performance were evaluated. The results showed that the adsorption capacity of DMCPs was much larger than that of magnetic chitosan particles (MCPs) in the examined pH range and decreased with Cl − concentration increasing, indicating that electrostatic interaction and ion exchange are the governing mechanisms of Cr(VI) adsorption by DMCPs. The Langmuir isotherm model and pseudo-second-order kinetic model fitted the experimental data well. The maximum adsorption capacity of DMCPs is 153.85 mg/g. Besides, Cr(VI)-loaded DMCPs could be easily separated and efficiently regenerated. Therefore, DMCPs are promising candidates for Cr(VI) adsorption owing to their excellent performance in a wide pH range, easy separation and good reusability. [ABSTRACT FROM AUTHOR]

Poly(lactic acid) has been extensively investigated in the biomedical field because of its good biocompatibility and biodegradability. As an important method of poly(lactic acid) synthesis, metal complex-catalyzed ring-opening polymerization (ROP) of lactide can achieve a controllable lactide polymerization through the selection of appropriate ligands and metals. In this study, a novel metal (LTi–O)2 complex was synthesized and structurally characterized. (LTi–O)2 showed a relatively high catalytic activity and controllability of Poly(D, L-lactide) (PDLLA) molecular weights (polydispersity index of 1.02–1.22) in the ROP of D,L-lactide. The kinetic equation of D,L-LA ROP catalyzed by (LTi–O)2 could be expressed as–d[M]/dt = k[M]2[(LTi–O)2]1, and the reaction activation energy was 95.67 kJ·mol−1. Physical/chemical properties and biocompatibility evaluation results showed that PDLLA obtained through the (LTi–O)2-catalyzed ROP of D,L- lactide exhibited a good degradation performance and excellent biocompatibility. [ABSTRACT FROM AUTHOR]

Weak interaction between flocculants and oil is a main bottleneck in the treatment of oil-containing wastewater. To solve this problem, a novel flocculant PAB with cationic micro-block structure and hydrophobic groups of benzene rings was synthesized by ultrasound initiated polymerization technique and applied to remove turbidity and oil from water. To avoid unnecessary addition of reagents in traditional template and micellar copolymerization, surface-active monomer benzyl(methacryloyloxyethyl)dimethylammonium chloride (BMDAC) with self-assembly ability in aqueous solution was employed to synthesize flocculants. The critical association concentration of BMDAC measured by conductivity and surface tension methods was 0.014 mol·L −1 . The results of reactivity ratio, statistical analysis of sequence-length distribution and 1 H NMR provided evidence for the synthesis of copolymer with cationic micro-block. In addition, the apparent viscosity measurement indicated that PAB had an obvious hydrophobic association property. Finally, flocculation tests demonstrated that flocculation performance was greatly improved by adding PAB and the removal rate of oil and turbidity both reached the maximum (87.5% and 92%) at dosage of 40 mg·L −1 and pH of 7.0. Flocculation mechanism investigation demonstrated that the cooperation of charge neutralization, adsorption bridging, and hydrophobic association effect played an important role. The formed flocs by PAB was large, compact, difficult to break, and easy to regrow because of the enhanced interaction between flocculants and oil. In summary, this study can provide important reference in the design of organic flocculants in oily wastewater treatment applications. [ABSTRACT FROM AUTHOR]

P(AM-DMDAAC) (PDA) was synthesized by ultrasound assisted polymerization with dimethyl diallyl ammonium chloride (DMDAAC) and acrylamide (AM) as the monomers. The reaction conditions of polymerization were investigated by single factor approach and L 16 (4 5 ) orthogonal array. Results showed that the intrinsic viscosity of PDA could reach 14.6 dL/g with the optimum polymerization conditions as following: monomer concentration of 30%, temperature of 30 °C, ultrasound time of 1 h, monomer mass ratio (m (DMDAAC) :m (AM) ) of 2:8, initiator concentration of 0.4‰, sodium benzoate concentration of 0.5‰, ethylene diamine tetraacetic acid (EDTA) concentration of 0.5‰, solution pH value of 6 and urea concentration of 0.3‰. The self-made PDA was characterized by several instruments. The results of FTIR and 1 HNMR indicated that PDA was successfully polymerized by AM and DMDAAC. DTA-TGA showed that PDA was very stable at room temperature. And SEM proved the porous and mushroom shaped structure of PDA. For PDA used as flocculant in sludge dewatering experiment, the results showed that the filter cake moisture content and the supernatant turbidity could be reduced to 66.3% and 24.1 NTU, respectively. Comparing with other four cationic polyacrylamides, the filter cake moisture content could be reduced by 2.0-7.4% and the supernatant turbidity could be reduced by 18.3-32.1% via using self-made PDA, that was to say, the dewatering efficiency of self-made PDA was the best. Besides, the optimal dosage of self-made PDA was the least, and the cost analysis showed that it was also favorable, a 14.6-39.3% cost could be saved by using self-made PDA. [ABSTRACT FROM AUTHOR]

Cationic polyacrylamide (CPAM) has been the focus of research in environmental engineering field, particularly in sludge dewatering. However, poor stability of the existing cationic polyacrylamide has limited its application. In the face of the current complex sewage/sludge environment, CPAM with high efficiency, good stability and economy is remarkably desired in this field. In this study, a CPAM (PAMA) with high acid and alkali resistance was synthesized through copolymerization of acrylamide (AM) and methacrylamido propyl trimethyl ammonium chloride (MAPTAC) under ultraviolet (UV) radiation. The structure, morphology as well as the thermal decomposition property were analyzed through instrumental analysis. Furthermore, influencing factors of the copolymerization reaction were investigated and discussed in detail. The dewatering performance of PAMA was also evaluated by measuring the supernatant residual turbidity (RT), moisture content of the filter cake (FCMC), and specific resistance to filtration of the sludge (SRF). The RT, FCMC, and SRF reached 4.70 NTU, 71%, and 3.94 (10 12 m Kg −1 ), respectively, at 40 mg L −1 of PAMA-25-15.1 and pH of 6.0. Furthermore, these indices did not increase with the pH changes of the original sludge, and which indicated a high acid and alkali resistance of PAMA. [ABSTRACT FROM AUTHOR]

ABSTRACT This study prepared TPDA, a high-intrinsic-viscosity cationic polyacrylamide, through ultraviolet (UV)-initiated template polymerization. Acrylamide (AM) and diallyldimethylammonium chloride (DMD) served as monomers, and poly sodium polyacrylate (PAAS) served as the template. The structure of TPDA was characterized by Fourier-transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, and thermogravimetric analysis. The synthetic conditions of TPDA were studied and optimized by single-factor experiments. An optimized product was obtained at an intrinsic viscosity of 11.3 dL g−1 and a conversion rate of 97.2% with a total monomer concentration of 20%, DMD concentration of 30%, initiator concentration of 0.045%, pH of 8, EDTA concentration of 0.3%, and UV irradiation of 90 min. Results showed that TPDA was the copolymer of AM and DMD with a micro-block structure at the molecular chain. Given its high intrinsic viscosity and cationic block structure, TPDA performed better in kaolin flocculation than that prepared without template addition. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41747. [ABSTRACT FROM AUTHOR]

Twocationic polyacrylamides, PAA and PAD, were synthesized for sludgedewatering. The advanced instruments such as 1H NMR, FTIR,and SEM were used to characterize the two copolymers. Their hydrophobicassociation properties in water were investigated by viscosimetryas well as the dewatering performance studied by the sludge dewateringexperiment. The results showed that the optimum conditions for preparationof PAA were that the initiator concentration, urea concentration,molar ratio of AODBAC to AM, and irradiation time were 0.3‰,1.0%, 10:90, and 60 min, respectively. Also, it was found that PAAhad a stronger hydrophobic interaction with a lower intrinsic viscosityand longer dissolution time as well as a better dewatering performance.Furthermore, the charge neutralization and bridging effects were foundto contribute much to the sludge dewatering by PAA in which the dewateringperformance was able to be enhanced further by the hydrophobic interaction. [ABSTRACT FROM AUTHOR]

Inthis study, a cationic block structure with a strong neutralizingability was formed through template polymerization. Acryloxyethyltrimethylammonium chloride (DAC) and acrylamide (AM) were used as monomers,and the ionic homopolymer sodium polyacrylate (NaPAA) was used asthe template. The product containing NaPAA after template polymerizationis denoted as NTP, whereas the copolymer obtained after removing theNaPAA is denoted as TP. The common polymer (denoted SP) of AM andDAC was copolymerized through solution polymerization. TP and SP werecharacterized and compared by Fourier transform infrared (FT-IR) spectroscopy,scanning electron microscopy (SEM), 1H nuclear magneticresonance (1H NMR) spectroscopy, and thermogravimetricanalysis (TGA). The results of 1H NMR spectroscopy andTGA showed that a cationic block structure was formed in TP. The mechanismof the cationic block polymer used in water treatment was extensivelystudied through a jar test in which turbidity, zeta potential, andaverage floc size were used to evaluate the flocculation performance.The results further supported the cationic block structure of TP.TP, with a different structure than SP, resulting in a stronger neutralizationability, showed a better performance in flocculating kaolin suspensions.The dominant mechanisms for TP flocculation behavior at pH 5, 7, and9 might be patching, charge neutralization, and bridging adsorption.The flocculation performance of NTP was not acceptable, whereas acidicNTP at pH < 2 showed a flocculation effect similar to that of TP. [ABSTRACT FROM AUTHOR]

Highlights: [•] A novel cationic flocculant P(AM–DAC–BA) was synthesized and characterized. [•] P(AM–DAC–BA) was synthesized through ultraviolet (UV) initiation. [•] P(AM–DAC–BA) prepared in quartz reactor was porous structure. [•] Comparison between quartz reactor and glass reactor was well studied. [•] P(AM–DAC–BA) was efficient in the dewatering of the textile sewage sludge. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A functionalized chitosan-based flocculant (MHCS-g-P(AM-DAC)) is synthesized by UV initiation. • The concentration of algae decreased as the flocculants dosage increased. • The removal efficiency of MHCS-g-P(AM-DAC) was higher than that of commercially available coagulant. • MHCS-g-P(AM-DAC) has high efficiency in the removal of algae and turbidity from raw water. Abstract The graft copolymer flocculant of chitosan namely, maleoyl chitosan-graft-poly(acrylamide–acryloxyethyl trimethyl ammonium chloride) [MHCS-g-P(AM-DAC)], was prepared by UV initiation to improve the solubility and flocculation efficiency of chitosan. Flocculating properties for algae removal were studied systematically. The effects of parameters such as monomer concentration, MHCS content, illumination time, photoinitiator concentration, cationic degree, pH and grafting efficiency over synthesis process of MHCS-g-P(AM-DAC) were studied. The characterization of obtained MHCS-g-P(AM-DAC) were carried out through different analytic techniques. The influences of dosage, pH, and G value on the flocculating properties were also investigated to support that MHCS-g-P(AM-DAC) was more effective than organic flocculant (CPAM) and inorganic coagulant (PFS and PAC) on algae removal. The flocculation mechanisms of MHCS-g-P(AM-DAC) were determinate by obtained zeta values. [ABSTRACT FROM AUTHOR]

In this work, a highly efficient and environmentally friendly chitosan-based graft flocculant, namely, acrylamide- and dimethyl diallyl ammonium chloride-grafted chitosan [CS-g-P(AM-DMDAAC)], was prepared successfully through plasma initiation. FTIR results confirmed the successful polymerization of CS-g-P(AM-DMDAAC) and P(AM-DMDAAC). P(AM-DMDAAC) was the copolymer of acrylamide- and dimethyl diallyl ammonium chloride. SEM results revealed that a densely cross-linked network structure formed on the surface. XRD results verified that the ordered crystal structure of chitosan in CS-g-P(AM-DMDAAC) was changed into an amorphous structure after plasma-induced polymerization. The flocculation results of low-algal-turbidity water further showed the optimal flocculation efficiency of turbidity removal rate, COD removal rate, and Chl-a removal rate were 99.02%, 96.11%, and 92.20%, respectively. The flocculation efficiency of CS-g-P(AM-DMDAAC) were significantly higher than those obtained by cationic polyacrylamide (CPAM) and Polymeric aluminum and iron (PAFC). This work provided a valuable basis for the design of eco-friendly naturally modified polymeric flocculants to enhance the flocculation of low-algal-turbidity water. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel functionalized Starch bioflocculants are successfully synthesized. • Chelation properties of two different structural chelating groups are compared. • Flocculation conditions for reaching high removal efficiencies are optimized. • Characterization results provided empirical evidence for existence of chelating groups. • "3E" triangular model was used to evaluate its flocculation-chelation properties. Two bioflocculants of starch-graft-P[acrylamide-acrylic acid] (SAA) and starch-graft-P[acrylamide-2-acacrylamido-2-methyl-1-propanesulfonic acid] (SAS) are designed for the flocculation–chelation of heavy metals. The successful polymer synthesis is confirmed through physicochemical characterization. SAA and SAS are used to remove Cu(II), Zn(II), and Ni(II) from simulated wastewater and Ni(II) from actual electroplating wastewater. The removal efficiencies for Cu(II), Zn(II), and Ni(II) in the simulated wastewater by SAA and SAS are more than 80.00%, whereas those for Ni(II) are more than 90.0% in the Ni-containing electroplating wastewater at the optimal condition. Flocculation experiments reveal that the sulfonate structure of SAS is highly conducive to improve flocculation efficiency. SAA and SAS have high selectivities for Cu(II) in the simulated water sample with mixed heavy metal. Finally, the 3E (i.e., environmental impact, economic benefit, and energy consumption) triangular evaluation model is established to evaluate the flocculation experiments for the removal of heavy metal ions using SAA and SAS. [ABSTRACT FROM AUTHOR]