Synthesis and characterization of poly (itaconic acid-co-stearyl methacrylate-co-acrylamide) hydrojels and applications of the hydrogels in methylene blue and crystal violet adsorption

In this study, hydrogels containing different ratios of acrylamide, itaconic acid, stearyl methacrylate and crosslinker were prepared and the swelling behavior of these hydrogels was determined. Hydrogels were synthesized by free radical polymerization technique using ammonium persulfate initiator and methylene bisacrylamide as crosslinker. The swelling behavior of the hydrogels was investigated in different temperature and pH environments. Studies investigating the effect of temperature on swelling behavior and capacity were carried out in the range of 25-70°C. For the pH effect, buffer solutions in the pH=2-12 range were used. It was determined that the swelling rate increased as the temperature increased. It was observed that the swelling capacity increased up to a certain temperature and then decreased. It was determined that swelling rate and capacity increased in direct proportion to pH. The adsorption behavior of methylene blue (MB) and crystal violet (CV) dyes of the synthesized hydrogels was studied. The effects of temperature, pH and particle size on adsorption were investigated. It was determined that as the temperature and pH increased, the MB adsorption capacity increased, but the CV adsorption capacity decreased. The MB and CV adsorption capacities of the hydrogels were found to be 624 and 783 mg/g, respectively, in pure water at 25°C. The highest adsorption capacity for MB is 1247 mg/g in water at 60℃; The highest adsorption capacity for CV was determined as 1981 mg/g at 25°C and pH=12. The compatibility of adsorption with Freundlich and Langmuir isotherms was investigated for both MB and CV. As a result of the studies, it was determined that the adsorption process conformed to both isotherms and was multilayered and physical adsorption. When the kinetics of adsorption was investigated, it was found that it was suitable for pseudo-second-order kinetics.