Search

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]

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]