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Highlights • A self-assembly anionic polyacrylamide was prepared via template polymerization and ultrasonic initiation. • Microblock structure in TPAS-U improved its charge neutralization and bridging in flocculation. • Microblock structure strengthened the recombination of flocs after fragmentation. • TPAS-U performed better in the treatment of hematite wastewater comparing with other APAM. Abstract Self-assembly is able to control molecular structure of flocculants and improves their flocculation efficiency. In this study, template polymerization and ultrasonic initiation system attributed to the self-assembly of anionic polyacrylamide (TPAS-U) with a microblock structure using acrylamide (AM) and sodium p-styrene sulfonate (SSS) as monomers and poly (allylammonium chloride) (PAAC) as template. The functional groups and ordered microblock structure in TPAS-U were discovered via characterization analysis. Association constant (K M) manifested the self-assembly mechanism. And the role of ultrasonic in the synthesis was discussed as well. TPAS-U with well-organized/special structure had excellent flocculation performance in the treatment of hematite wastewater over other anionic flocculants. The flocs formed by TPAS-U possessed the big size, the compact structure and the strong recover ability after breakage. The uniform and regular microblock structure in TPAS-U attributed to the high utilization efficiency of negative charges, which improved neutralization, adsorption and bridging in the treatment. Graphical abstract Image, graphical abstract [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]

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]

Modified natural polymer flocculants has been the focus of research in environmental engineering field. Natural large molecular compound, chitosan (CTS) with many functional amino and hydroxyl groups can be easily modified to enhance its original functions. This work presents an environmentally friendly chitosan-based cationic polyacrylamide flocculants (CTS-g-PAMA) with enhanced function of sterilization and flocculation. CTS-g-PAMA was synthesized through Ultraviolet (UV)-initiated copolymerization. Structure characterization of FTIR, 1 H NMR, XRD and UV spectrum confirmed the successful grafting of AM and MAPTAC. Scanning electron microscopy (SEM) analysis results showed that CTS-g-PAMA exhibited a porous structure with a prodigious surface area. CTS-g-PAMA was then applied to treat a series of simulated waste water containing kaolin or Escherichia coli . Flocculation tests indicated that CTS-g-PAMA not only showed excellent flocculation effect but also showed high sterilization capability. A series of ONP concentration measurement tests through UV spectra analysis and 3D EEM analysis of suspension before and after flocculation were conducted to study sterilization mechanism, and results revealed the sterilization effect of CTS-g-PAMA was essentially bactericidal, not just antibacterial. [ABSTRACT FROM AUTHOR]

• Amphiphilic CPAM was fabricated through ultrasonic initiated template polymerization. • Comparative characterizations confirmed the microblock structure and amphiphilicity. • Template copolymerization met bimolecular termination of free radical polymerization. • The effect of NaPAA followed template polymerization I (ZIP) mechanism. • Cationic microblocks produced stronger flocs to form more permeable filter cakes. Flocculation is an important pretreatment technique for sludge dewatering, the performance of employed flocculants is the key factor determine the flocculation efficiency. Herein, an amphiphilic cationic polyacrylamide (CPAM) with microblock structure was synthesized through template copolymerization initiated by ultrasonic. The chemical components and cationic microblock structure of copolymers were confirmed through comparative characterization by Fourier Transform Infrared (FTIR) and Nuclear Magnetic Resonance (1H NMR) spectrum. The copolymerization mechanism was investigated through kinetics study and association coefficient (K M) determination. The results indicated that the reaction followed free radical copolymerization and terminated mainly through bimolecular termination. The pre-adsorption between acryloyloxyethyltrimethylammonium chloride (DAC) and sodium polyacrylate (NaPAA) before reaction confirmed the template polymerization met the type I (ZIP) mechanism. Cationic microblocks and hydrophobic association together contributed to the optimal dewaterability (FCMC=67.2 %, SRF=3.84×1012 m·kg−1) using TP(AM-DAC-LA). Hydrophobic association enhanced bridging and sweeping effect to promote the floc size growth. Cationic microblocks produced compacter flocs with stronger mechanical strength through enhanced charge neutralization and patching effects, which acted as skeletons to make filter cakes less compressible and more permeable in mechanical dewatering. This work developed a highly effective flocculant for sludge dewatering, the synthesis and working mechanism of which were also given. [ABSTRACT FROM AUTHOR]

In this study, maleyl chitosan- graft -polyacrylamide (MHCS-g-PAM), a novel chitosan-based flocculant, was prepared through UV irradiation, and maleyl chitosan (MHCS) was designed and prepared with maleic anhydride and acrylamide (AM) through maleyl acylation reaction. The effects of monomer concentration, MHCS-to-AM ratio, illumination time, initiator concentration, pH on viscosity, and grafting efficiency were investigated to optimize the synthesis of these substances. MHCS-g-PAM was characterized through Fourier transform infrared spectroscopy, nuclear magnetic resonance hydrogen spectroscopy, scanning electron microscopy, and thermal gravimetric analysis. Flocculation mechanisms in alga-containing wastewater at various pH levels and dosages were examined in detail on the basis of zeta potential measurements. Zeta potential experiments indicated that the adsorption-bridging and charge neutralization mechanisms played an important role in algal removal. Flocculation tests on algal removal demonstrated that the flocculation performance of MHCS-g-PAM was more effective than that of cationic polyacrylamide, polyferric sulfate, and polymeric aluminium. The optimal Chl- a and COD removal rate obtained by MHCS-g-PAM was 98.6% and 94.9% at pH 7 and 4 mg·L − 1 , respectively. [ABSTRACT FROM AUTHOR]