Effect of pH Value on the aqueous precipitation copolymerization of acrylonitrile and vinyl acetate

A microblock structure type of anionic flocculant for hematite wastewater treatment: template copolymerization mechanism and enhanced flocculation effect

In this study, a novel anionic template polymer (TPAS) with microblock structure was prepared by ultraviolet light (UV)-assisted template copolymerization (UV-TP). Acrylamide (AM) and sodium styrene sulfonate (SSS) were selected as monomers and polypropylene ammonium chloride (PAAC) was chosen as the template. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), nuclear magnetic resonance hydrogen spectroscopy (¹H NMR), and thermogravimetry/differential scanning calorimetry (TG/DSC) were used to characterize the polymer chemical structure. The results showed that the attractive anionic microblock structure was formed in TPAS. Besides, the association constant (K_M) and template reaction kinetics analysis results indicated that the polymerization reaction followed I (ZIP) template copolymerization mechanism. It proved the microblock structure formation again. The anionic microblock structure in TPAM could greatly improve the ability of charge neutralization, electrical patching, and bridging. After the hematite wastewater was conditioned by TPAS with this novel anionic microblock structure, the generated hematite flocs had larger particle size and denser structure. It was favorable for the reduction of turbidity, and the turbidity removal rate could reach 97.8%. TPAS showed excellent flocculation performance for hematite wastewater and had a broad market application prospect.

Investigation of the effect of some variables on terpolymerization process of vinyl monomers in CSTR by design of experimental method

Aqueous slurry free radical terpolymerization of acrylonitrile (AN) with vinyl acetate (VAc) and a constant amount of 2-acrylamido-2-methylpropane sulfunic acid (AMPS) using K2S2O8/NaHSO3 redox initiator was carried out in a 15-l continuous stirred tank reactor at constant temperature (60°C) and atmospheric pressure. A three-level response surface method based on central composite design was applied to investigate the effect of VAc concentration (wt%) in monomer mixture, bisulfite- to-persulfate ratio in redox initiator system $\left( {\frac{{{\text{[HSO}}_3^ - ]}}{{[{{\text{S}}_2}{\text{O}}_8^{ - 2}]}}} \right)$ and bisulfite-to-monomer mixture ratio $\left( {\frac{{[{\text{HSO}}_3^ - ]}}{{{\text{AN}} + {\text{VAc}}}}} \right)$ on the monomer conversion percentage to polymer, intrinsic viscosity [(η)] and sulfur end groups (SEG) index of the prepared polymers. Experimental results showed that the optimum conditions for synthesis of AN-VAc-AMPS system can be addressed as VAc=9 wt%, $\left( {\frac{{[{\text{HSO}}_3^ - ]}}{{[{{\text{S}}_2}{\text{O}}_8^{ - 2}]}}} \right) = 9.6$ and $\left( {\frac{{[{\text{HSO}}_3^ - ]}}{{{\text{AN}} + {\text{VAc}}}}} \right) = 0.027.$ Monomer conversion percentage to polymer, intrinsic viscosity and SEG index under optimum conditions were 75%, 1.38 dl/g and 190, respectively. The synthesized polymer under these optimum conditions can satisfy the requirements for acrylic fiber production in which its characterization was confirmed with Fourier transform infrared spectroscopy, nuclear magnetic resonance, elemental analysis, X-ray diffraction, differential scanning calorimetry and scanning electron microscope.