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In this work, a new cationic flocculant, CMCTS‐g‐CPAM was synthesized by acrylamide (AM), methacryloyloxyethyltrimethylammonium chloride (DMC) and carboxymethyl chitosan (CMCTS) through UV initiated graft polymerization techniques. The structure of CMCTS‐g‐CPAM was analysed by infrared spectroscopy (IR), nuclear magnetic resonance spectroscopy (1H NMR) and X‐ray diffraction (XRD) techniques which indicates that AM and DMC are grafted successfully onto CMCTS to obtain CMCTS‐g‐CPAM. The potential of CMCTS‐g‐CPAM for the sludge dewatering was investigated. The effects of cationic degree, intrinsic viscosity, dosage and pH on the sludge dewatering performance were studied. The results indicate that the optimal dewatering performance with minimum supernatant turbidity of 5.40 NTU, the moisture content of the filter cake of 79.28% and the specific resistance of the sludge of 1.96 × 1013 m/kg was obtained at 30 mg/L CMCTS‐g‐CPAM at pH 9–10. Finally, from the microscopic and electron micrographs investigation, it was confirmed that the particle size of the CMCTS‐g‐CPAM treated sludge was significantly large to enhance hydrophobicity and improve dewatering performance. [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]

• The β-cyclodextrin grafted flocculants were synthesized by ultrasound-assisted method. • The synthesized conditions of CADs were optimized. • CADs showed excellent flocculation performance in treating HA-kaolin wastewater. • The interaction effect between β-CD and HA could improve flocculation performance. In this work, the novel β-cyclodextrin based polymeric flocculants (CADs) were synthesized and applied on the treatment of humic acid (HA)-kaolin wastewater. Acrylamide (AM) and acryloyloxyethyltrimethyl ammonium chloride (DAC) were grafted onto β-cyclodextrin (β-CD) by ultrasound assisted initiation using ceric ammonium nitrate as initiator. The synthesized conditions were optimized by evaluating the intrinsic viscosity and grafting efficiency of CADs. Furthermore, the characterization methods including Fourier transform infrared spectroscopy (FTIR), 1H nuclear magnetic resonance spectroscopy (1H NMR), thermogravimetric/differential scanning calorimetry (TG/DSC) and scanning electron microscopy (SEM) were used to evaluate and analyze the molecular structure and surface morphology of graft copolymers. In flocculation experiments, the effects of dosage, flocculant types, solution pH and flocs properties on flocculation performance were investigate in detail. CADs exhibited more satisfactory turbidity and HA removal performance than the synthetic cationic flocculants (PAD) and the non-ionic graft polymers (CAM). At the optimum dosage 4 mg/L, the maximum turbidity and HA removal rate of CAD 1# was 97.5% and 68.3%, respectively. Furthermore, CAD 1# exhibited a good flocculation performance and wide flocculation window in the pH range of 2.0–8.0. Lastly, the flocculation mechanism of CAD was detailed discussed by the investigation of zeta potential, surface tension, flocs FTIR and XPS spectra. Results indicated the unique hydrophobic internal structure of β-CD played an important role in improving the removal rate HA of CAD. [ABSTRACT FROM AUTHOR]

• Organic flocculant was used to treat metalworking wastewater for the first time. • Hydrophobic modified flocculant was polymerized through UVC initiation polymerization. • UVC initiation showed great advantage in polymerization to traditional UV initiation. • Hydrophobic block in flocculant facilitated the adsorption of nonpolar oil/colloids. In this work, a hydrophobically modified cationic polyacrylamide (CPAC) flocculant was polymerized by short-wave ultraviolet (UVC) initiation with acrylamide, acryloyloxyethyl trimethylammonium chloride, and coconut diethanolamide (CDEA) as monomers to enhance the destabilization and separation efficiency of emulsified oil and particles/colloids from metalworking fluids wastewater (MWFs). The parameters for flocculant polymerization were optimized, and the features of UVC-initiated polymerization were studied. Moreover, the structural and morphological characteristics of the polymers were explored, and the flocculation performance of CPAC in MWFs treatment was evaluated. The characterization results suggested that flocculants with a multilayer, loose-sheet morphology and intrinsic viscosity of 11.32 dL g−1 could be successfully polymerized by UVC-initiated polymerization. Compared with traditional UV, UVC irradiation initiation promoted the copolymerization of flocculants with a high monomer conversion rate and intrinsic viscosity. We observed the low dosage requirement and acid resistance of the flocculant synthesized by UVC-initiated polymerization, which produced the lowest residual turbidity, highest chemical oxygen demand, and most efficient oil removal during MWFs treatment among the samples studied. Besides charge neutralization and bridging effects, the adsorption effect between hydrophobic CDEA blocks and nonpolar oil/colloids facilitated the formation of microflocs and improved the flocculation efficiency of the flocculant. [ABSTRACT FROM AUTHOR]

[Display omitted] • Amphoteric starch-based flocculants were synthesized by low-pressure UV initiation. • Amphoteric starch-based flocculants show high flocculation performance. • Amphoteric starch-based flocculants exhibit low salts sensitivity. • Flocculation mechanism includes charge neutralization, patching and bridging. Surface charges of the suspended colloidal particles in real water can be either negative or positive. Flocculation is one of the most widely used technologies in water treatment. A series of amphoteric starch-based flocculants (denoted as ASBFs) with the same chemically modified functional groups but different charge degrees and intrinsic viscosities were successfully via low-pressure ultraviolet initiation and used for the removal of different charged contaminants from water. The characterization results confirmed the successful grafting acrylamide (AM) and 2-methacryloyloxyethyl) trimethyl ammonium chloride (DMC) onto carboxymethyl starch. Different influencing factors, including flocculant dosage, contaminants concentration, pH of solution, stirring speed, sedimentation time and various salts, were investigated systematically. ASBFs with eco-friendliness exhibited high flocculation property, low optimal dosage and low salts sensitivity, for not only kaolin, but also hematite suspensions. The zeta potential (ZP) measurement suggested that the removal mechanism mainly includes charge neutralization, patching and bridging. [ABSTRACT FROM AUTHOR]

• Novel functionalized chitosan flocculants are successfully synthesized. • 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. • Flocculation-chelation capacity profile indicated multiple potential applications. In order to effectively remove the dissolved heavy metals and the heavy metals on the colloidal particles during the flocculation process, a novel dual-functional chitosan flocculant CMCTS-g-P(AM-CA) is prepared by ultraviolet light-initiated graft polymerization using CMCTS, AM, and ammonium dithiocarbamate. The main influencing factors of monomer concentration, monomer ratio, pH value, photoinitiator concentration, and illumination time are investigated on the basis of intrinsic viscosity, grafting rate, and grafting efficiency of CMCTS-g-P(AM-CA). Characterization results provided empirical evidence for existence of chelating groups. In addition, CMCTS-g-P(AM-CA) was applied to treat the simulated heavy metals and electroplating wastewater. The effect of CMCTS-g-P(AM-CA) dosage, pH value, and reaction G value on flocculation efficiency was also explored. After the two-stage flocculation, the residual concentration of Ni(II), COD, and turbidity of actual electroplating wastewater decreased to 0.96 mg/L, 93.00 mg/L, and 1.71 NTU after flocculation tests at optimal condition, respectively. Finally, the "3E" triangular evaluation model is established and applied to evaluate the flocculation performance of CMCTS-g-P(AM-CA) on the actual heavy metal wastewater further, thereby proving its excellent chelation flocculation performance. [ABSTRACT FROM AUTHOR]