In this work, a hydrogel system was produced via radical polymerization of N,N-dimethylacrylamide and 2-acrylamido-2-methylpropanesulfonic acid in the presence of N,N-methylene-bis-acrylamide as a crosslinker and ammonium persulfate as an initiator. Parameters that impact the conversion of copolymerization (such as initial concentration of monomers, temperature, initiator dose, and time) were studied. The swelling degree of the hydrogel was investigated with the addition of a crosslinker and initiator at different pH levels. A hydrogel with high conversion and high swelling degree was selected to investigate their ability for adsorption of Pb(II) ions from solutions. Adsorption behavior of Pb(II) ions in a hydrogel was examined as a function of reaction time and concentration of lead ions from a solution of Pb(II) ions.
The kinetics of copolymerization is one of the key factors for optimization the process in large scale of production. Copolymerization of N, N‐dimethyl‐N,N‐diallyammonium chloride (DMDAAC) with N,N‐dimethyl acrylamide (DMAA) was studied by a dilatometer technique using ammonium persulfate ([NH4]2S2O8) as an initiator. The effect of the parameters (including molar ratio of DMDAAC to DMAA, concentrations of monomers [M] and initiator [I], and the temperature) on the polymerization rate was analyzed. From these analyses it was found that the polymerization rate (Rp) with the above variables can be represented as the following relationship: Rp∝ [M]2.63; Rp∝ [I]0.40 andRp∝[MDMDAAC:MDMAA]‐0,86.The negative order found in the relationship of the reaction rate and the monomer composition indicated that the DMDAAC concentration in the monomers composition conversely affected the polymerization rate. The overall activation energy for the polymerization rate was 39.56 kJ/mol in the temperature range between 40°C and 60°C. Based on the experimental results, the mechanism of polymerization is discussed in detail. Different thermal properties for DMDAAC and DMDAAC‐DMAA were observed by differential scanning calorimetry (DSC), and thermogravimetry (TG) analysis. Addition of DMAA to DMDAAC lowered the thermal stability relative to the home polymer of DMDAAC.
The lifetime of water solution foams of sodium dodecylsulfate (DDS, low molecular weight surfactant) and sodium carboxymethylcellulose (SCMC, polyelectrolyte) and their binary mixtures was experimentally investigated. The effects of ionic strength and acidity on the foam life were also determined. In binary solutions, a synergic effect of DDS and SCMC on the surface tension reduction, most likely resulting from the interaction of the surfactant with polymer, was found. The addition of NaCl into solution or increasing the ionic strength was found to decrease the surface tension and reduce interfacial mobility, hence increased foam lifetime. The relatively low lifetime of binary solution foams in acidic medium was attributed to the reaction between SCMC and acid, which resulted in relatively small reductions in the viscosity and consequently lowered the solution viscosity. C 2006 Springer Science + Business Media, Inc.
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