Preparation of super high concentration cationic polyacrylamide emulsion and its flocculation with cationic polymers

Optimization Conditions to Obtain Cationic Polyacrylamide Emulsion Copolymers with Desired Cationic Degree for Different Wastewater Treatments

The synthesis of cationic polyacrylamides (CPAMs) with the desired cationic degree and molecular weight is essential for various industries, including wastewater treatment, mining, paper, cosmetic chemistry, and others. Previous studies have already demonstrated methods to optimize synthesis conditions to obtain high-molecular-weight CPAM emulsions and the effects of cationic degrees on flocculation processes. However, the optimization of input parameters to obtain CPAMs with the desired cationic degrees has not been discussed. Traditional optimization methods are time-consuming and costly when it comes to on-site CPAM production because the input parameters of CPAM synthesis are optimized using single-factor experiments. In this study, we utilized the response surface methodology to optimize the synthesis conditions, specifically the monomer concentration, the content of the cationic monomer, and the content of the initiator, to obtain CPAMs with the desired cationic degrees. This approach overcomes the drawbacks of traditional optimization methods. We successfully synthesized three CPAM emulsions with a wide range of cationic degrees: low (21.85%), medium (40.25%), and high (71.17%) levels of cationic degree. The optimized conditions for these CPAMs were as follows: monomer concentration of 25%, content of monomer cation of 22.5%, 44.41%, and 77.61%, respectively, and initiator content of 0.475%, 0.48%, and 0.59%, respectively. The developed models can be utilized to quickly optimize conditions for synthesizing CPAM emulsions with different cationic degrees to meet the demands of wastewater treatment applications. The synthesized CPAM products performed effectively in wastewater treatment, with the treated wastewater meeting the technical regulation parameters. ¹H-NMR, FTIR, SEM, BET, dynamic light scattering, and gel permeation chromatography were employed to confirm the structure and surface of the polymers.

Chitosan-based dual network composite hydrogel for efficient adsorption of methylene blue dye

With the rapid development of the textile industry, a large amount of dyeing wastewater discharge has caused great harm to the ecological environment. In this work, a dual-network, composite hydrogel adsorbent with excellent mechanical properties, good reusability, and large adsorption capacity was prepared by introducing chitosan cross-linked polyvinylamine into the N,N'-methylenebisacrylamide cross-linked polyacrylic acid network. The dual cross-linking network gave the hydrogel excellent mechanical properties with maximum tensile stress and strain up to 1.9 MPa and 920 %. The adsorption capacity of methylene blue on hydrogel was up to 596.14 mg/g. In addition, the prepared hydrogel exhibited good reusability, and their adsorption efficiency remained above 85 % in five consecutive cycles. The adsorption behavior was well fitted by Pseudo-second-order kinetics and the Langmuir equation, indicating that the hydrogel was chemisorbed to the dye as a monolayer. The adsorption mechanism analysis showed that the electrostatic interactions and hydrogen bonding between the functional groups of the hydrogels and methylene blue molecules contributed to the good adsorption capacity. Overall, the synthesized composite hydrogels could be used as an efficient adsorbent for the removal of methylene blue dye, particularly from textile industry wastewater.

Research Progress on Typical Quaternary Ammonium Salt Polymers

Quaternary ammonium salt polymers, a kind of polyelectrolyte with a quaternary ammonium group, are widely used in traditional and emerging industries due to their good water-solubility, adjustable cationicity and molecular weight, high efficiency and nontoxicity. In this paper, firstly, the properties and several synthesis methods of typical quaternary ammonium salt monomers were introduced. Secondly, the research progress on the synthesis of polymers was summarized from the perspective of obtaining products with high molecular weight, narrow molecular weight distribution and high monomer conversion, and special functional polymers. Thirdly, the relationships between the structures and properties of the polymer were analyzed from the perspectives of molecular weight, charge density, structural stability, and microstructural regulation of the polymer chain unit. Fourthly, typical examples of quaternary ammonium salt polymers in the application fields of water treatment, daily chemicals, petroleum exploitation, papermaking, and textile printing and dyeing were listed. Finally, constructive suggestions were put forward on developing quaternary ammonium salt polymers with high molecular weights, strengthening the research on the relationships between the structures and their properties and pinpointing relevant application fields.