Papers by Keyword: Polyacrylamide

Abstract: Hydrogels are very compliant materials suitable for tissue engineering in various areas of biological and clinical research. Appropriate and effective application of hydrogels for specific cellular regeneration often requires precise knowledge of their mechanical properties. The present work focuses on measurements of mechanical deformation and creep properties of polyacrylamide hydrogels using a novel indentation system. Four concentrations of polyacrylamide gel were tested under four different loading rates to study the mechanical response of the material to various loading rates. A spherical indenter with large radius was used in the experiments and all indentations were done with the sample completely immersed in water. The results show that higher acrylamide concentration in the gel leads to higher elastic modulus and decrease of creep. Similarly, faster loading rates lead to higher elastic modulus and larger creep during the hold period. The data were analyzed using both Hertzian fit to the loading part and Oliver-Pharr approach to the unloading part. The discrepancy between these two approaches and significant creep behavior are related to the viscoelasticity of the tested materials. This work contributes to understanding the results of instrumented indentation of extremely compliant materials with respect to their viscoelastic properties.

Abstract: In this investigation, nanoparticles of ferroferric oxide were synthesized and used as the photo initiator in the polymerization of acrylamide. The influences of different factors, including reaction time, light intensity, the content of ferroferric oxide nanoparticles, and the concentration of acrylamide monomer on the synthesis of polyacrylamide were discussed. The possible mechanisms of the photopolymerization irritated by Fe₃O₄ nanoparticles, and the photoinitiation stage with the participantion of the acrylamide radicals were also proposed. The results show that the ferroferric oxide nanoparticles could be successfully applied in the photopolymerization. The optimum conditions of the photopolymerization of acrylamide, which include acrylamide monomer content of 30wt%, reaction time of 30 mins, the Fe₃O₄ nanoparticles concentrations of 1.2 mmol/l, and the light intensity of 8.0 mW/cm².

Abstract: A polyacrylamide-grafted starch (St-g-PAM) flocculant for the coal slurry wastewater, was prepared by using corn starch and acrylamide (AM) as monomers through solution polymerization. The structure of the synthesized St-g-PAM was characterized by FT-IR and TG. The effects of initiator concentration, reaction temperature, and monomer concentration on percentage of grafting and the grafting efficiency were investigated. The results show that the optimal conditions of the polymerization are as follows: the monomer to substrate ratio of 2.5, potassium persulfate of 0.08 g/mL, reaction time of 3h, the reaction temperature of 65°C. The additional dosage of St-g-PAM is varying between 35 and 45 mg/L to obtain good flocculation capability, better flocculation capability with the addition of 30mg/L of FeCl3.

Abstract: Polyacrylamide is of concern in oil recovery wastewater treatment because of its persistence and environment effects. A concept is proposed to synthesize γ-Fe₂O₃ particles with magnetic functionalization for polyacrylamide removal from aqueous media. Magnetic particles were synthesized by the sol-gel method, using NH₄HCO₃ and FeSO₄·7H₂O. These magnetic particles show high adsorption capacity for polyacrylamide. Because of the useful magnetic property, large specific surface area and fast magnetic separation, the synthesized materials will provide a convenient and highly efficient means to remove polyacrylamide from oil recovery wastewater.

Abstract: By means of grafting polymerization, cross-linked starch-g-polyacrylamide (starch-g-PAM) was prepared and used to adsorb methylene blue (MB). Adsorption isotherm and kinetic of the sorption process were studied. The experimental results demonstrated that the prepared starch-g-PAM was an effective adsorbent for removal of MB from aqueous solution. The adsorption of MB by starch-g-PAM was Freundlich type, and the adsorption equation was caculated to be . Furthermore, the adsorption kinetics analysis demonstrated that the adsorption process followed the pseudo-second-order model.

Abstract: Abstract：There are many methods to measure the concentration of HPAM. In this paper, the starch-cadmium iodine method was used to measure the concentration of HPAM that existed in the extraction liquid of oil field. The optimum testing condition that measures the concentration of HPAM in the produced water of oilfield is investigated by using the starch-cadmium iodine method , and the testing upper limit and lower limit of this method are affirmed. The features of this method are the wide linear range，simplicity and high accuracy.

Abstract: Polyacrylamide has been widely used in tertiary oil recovery. Oilfield produced water in a large scale contain polyacrylamide, leading to oilfield environment pollution. In this paper, the nested loops biofilm airlift suspension reactor was used in polyacrylamide wastewater treatment. In the reactor, wastewater can alternately flow through the hypoxic environment fixed light carriers and aerobic environment suspended walnut shell biological carriers, achieving simultaneous removal of organic matter and nitrogen. The influencing factors on the organic compound degradation and denitrification performance were studied. Biological and hydrodynamic model of nitrogen and carbon removal was established. Also, the biological phase structure of the carrier biofilm was observed. The results show that polyacrylamide degradation and ammonia nitrogen removal rate are around 30% and 95%, respectively when the experimental hydraulic retention time is 24h. Due to poor denitrification efficiency; nitrate removal rate is only 20%. The carrier biofilm thickness is appropriate, and filamentous bacteria occupy the dominant position.

Abstract: Raw micro-polluted water was sampled from a water treatment plant in Gaomi, a town in north China. The treatment with diatomite-enhanced coagulation was investigated, including the effect of dose and the dosing point of diatomite on enhanced coagulation. The results showed that the removal efficiencies of turbidity, color, UV₂₅₄ and COD_Mn could reach 78.99 %, 76.19 %, 29.63 % and 22.77 %, respectively, when 15 mg/L diatomite was added at 30 minutes before coagulation. It was found that the optimum pH of diatomite-enhanced coagulation was approximately 6~7.

Abstract: A polyacrylamide-grafted starch (St-g-AM-DMC-AMPS) flocculant for the coal slurry wastewater was prepared by using corn starch (St), acrylamide (AM), methyl acryloyloxyethy trimethyl ammonium chloride (DMC) as cationic monomer, 2-acrylamido-2-methyl acrylate sulfonic acid (AMPS) as anionic monomer through solution polymerization. The structure of the synthesized St-g-AM-DMC-AMPS was characterized by FT-IR and TG. The effects of initiator concentration, reaction temperature and monomer concentration on percentage of grafting and the grafting efficiency were investigated. The results showed that the optimal conditions of the polymerization are that the ratio of substrate and monomer is 3:7, the radio of ammonium persulfate is 0.15%, reaction time is 4h and reaction temperature is 50°C. The additional dosage of St-g-AM-DMC-AMPS is varying between 12mg/L and 20 mg/L to obtain better flocculation capability than PAM.

Abstract: A serial of micro-scale cationic particles was synthesized by inverse suspension polymerization. These particles formed flocs with hydrolyzed polyacrylamide through electrostatic attraction. The structure of these flocs evolved from a bulk state to insulated microspheres at a critical salt concentration, which increased with increasingly cationic degree of particles, corresponding to the change of Zeta potential. Moreover, the adsorbance of HPAM on the cationic particles attained a maximum about 409 mg/g at 500mg/L HPAM in salt-free water and 237 mg/g at 800mg/L HPAM in 2wt% NaCl solution at 20°C according to a semi-quantitative method implemented by viscosity contrast experiment. This adsorbance difference accounts for that the electrostatic shielding effect of salt stimulates the desorption rate of HPAM.