Adsorption/desorption performance of Pb2+ and Cd2+ with super adsorption capacity of PASP/CMS hydrogel

Super-absorbent polyaspartic acid/carboxymethyl salix psammophila powder (PASP/CMS) hydrogel was prepared by aqueous solution polymerization. PASP/CMS hydrogel was characterized by FT-IR, XRD, SEM and XPS. The results show that PASP/CMS hydrogel is prepared by graft copolymerization of the -COOH of polyaspartic acid (PASP) and the -CH2OH of carboxymethyl salix psammophila powder (CMS). The surface of that hydrogel becomes dense from loose porosity, and Pb2+ and Cd2+ are adsorbed onto the surface of hydrogel. The crystallinity of CMS is destroyed by the addition of PASP. The initial concentration of Pb2+ and Cd2+, pH, adsorption time and adsorption temperature on the adsorption effect were studied through experiments. And results showed that hydrogel has a good removal effect on Pb(II) and Cd(II) ions. Pseudo-second-order kinetic and Langmuir isotherm models are represented in the process, which are spontaneous, exothermic and decrease of randomness, and it's a single layer chemical adsorption. At the same time, the effect of desorption experimental parameters (HNO3 initial concentration, desorption time, and desorption temperature) on the experiment was studied and optimized.

Research of a novel double cross-linking fracturing fluid

A kind of JDL-1 thickener for betaine hydrophobic association polymer was prepared by aqueous solution polymerization of mixed micelles, AM, AA, AMPS and DM16 were used as raw materials, which was synthesized by redox initiator system. Friction tester and high-temperature rheometer were used to evaluate the resistance reduction and temperature and shear resistance of the thickener. The results show that the viscosity average molecular weight of the polymer prepared with AM, AA, AMPS and DM16 mass ratio of 70∶20∶5∶5 was higher than 12 million, and the dissolution time of the polymer was less than 3 min. When the surfactant is used for physical cross-linking, the apparent viscosity of the cross-linked fracturing fluid is larger than that of 60 mPa·s at 90 °C, 170 s-1 sheared 1 h; when metal cross-linking agent is used for coordination cross-linking, the apparent viscosity is larger than that of 80 mPa·s at 120 °C, 170 s-1 sheared 1 h. The drag reduction rate was 73%, the anti-swelling rate was higher than70%, and the damage rate was less than10%. The field trial was successful and confirmed the multifunctional effect of betaine-type hydrophobic associating polymer.

Synthesis of polyampholytic diblock copolymers via RAFT aqueous solution polymerization

Two new classes of polyampholytic diblock copolymers are prepared via RAFT aqueous solution polymerization and their aqueous solution behaviour is assessed using 1H NMR spectroscopy, dynamic light scattering and aqueous electrophoresis measurements.

Superabsorbent polymer composites derived from polyacrylic acid: Design and synthesis, characterization, and swelling capacities

Superabsorbent polymers (SAPs) were synthesized by aqueous solution polymerization of carboxymethyl cellulose (CMC)/acrylic acid (AAc) and polyvinyl alcohol (PVA)/AAc blend using benzoyl peroxide as an initiator. SAPs were synthesized by a facile method under mild conditions. A comparative study was done between CMC/AAc as a biodegradable superabsorbent and PVA/AAc copolymer. The effects of cross-linking, reaction time, temperature, and initiator molar ratio on water absorbency were studied herein. The highest swelling capacity was obtained for CMC/AAc biodegradable superabsorbent composite. The water absorption capacity of SAPs increased with increases in benzoyl peroxide content, immersion time, and reaction temperature of polymerization. The gel fraction of SAPs decreased with increases in the amounts of N, N′-methylenebisacrylamide as a cross-linker. Fourier-transform infrared spectroscopy was used to examine the molecular interactions. The morphology and structure of superabsorbent composites were investigated by scanning electron microscopy.

N,N-DIMETHYLACRYLAMIDE HYDROGELS FOR CONTROLLED DRUG DELIVERY. INFLUENCE OF NETWORK STRUCTURE AND DRUG SOLUBILITY ON THE LOAD AND RELEASE MECHANISMS

The aim of the present work was to synthesize sustained-release hydrogels based on N,N-dimethylacrylamide (DMA) to study the effect of the polymer matrix structure and the solubility of drugs on the load and release mechanisms. A series of crosslinked DMA hydrogels were synthesized with different monomer concentration and crosslinker to monomer ratio by free radical aqueous solution polymerization at 37ºC using N,N-methylen-bis-acrylamide as crosslinking agent. The effect of total monomer concentration and degree of crosslinking on the water absorption, glass transition temperature values, mechanical properties, and load/release of different drugs was studied. Main results showed that: a) the structure of the network, obtained by varying the monomer and crosslinking agent concentration, is a factor that governs the chemical and physical properties of the hydrogel (water absorption, glass transition temperature, storage and loss moduli, network parameters), b) the rate and amount of drug released from swellable hydrogels depend on both the degree of hydrogel crosslinking and the water solubility of the drug. In all cases, as the concentration of the crosslinker agent increased, the swelling capacity of the hydrogels was reduced and drugs with high solubility in water were more easily released, probably due to their greater affinity for the medium.

Optimizing the preparation conditions of amphoteric polyacrylamide as a strength additive for recycled paper

Acrylamide, itaconic acid and methacryloyloxyethyl trimethylammonium chloride were used to synthesize a series of amphoteric polyacrylamides (AmPAM) by aqueous solution polymerization through varying the pH, the reaction time, the temperature and the composition. The polymers were characterized by molecular weight and added in a recycled pulp furnish to make sheets. Paper strength was highest with the polymer made at pH 7 and 70 °C for 6 h with a monomer ratio of 2:0.3:0.3 (AM:IA:DMC) with 0.6 % initiator (based on the total mass of monomers). The optimized polymer was characterized by thermal gravity analysis, Fourier transform infrared spectroscopy and was then added at various pH and dosage level to the pulp alone or in combination with PAC, to determine the optimum addition conditions. Strength increased significantly with AmPAM addition level and PAC dosage but pH had little effect. The treated fibers were characterized by Zeta potential and drainage measurements. SEM showed the presence of a polymer film that is believed to reinforce inter-fiber bonds in the paper.

Preparation and evaluation of polyampholyte inhibitor DAM

In this study, polyampholyte inhibitor DAM was synthesized from three monomers, namely, diallyl dimethyl ammonium chloride, methyl allyl alcohol and 2-acrylamido-2-methyl propane sulfonic acid, by aqueous solution polymerization.