چكيده لاتين
Dyes are among the common pollutants and, in some cases, are considered highly hazardous to the environment, and finding effective methods for their removal has always been an important challenge. In recent years, polymeric network adsorbents, either interpenetrating or semi-interpenetrating, have attracted attention due to their stable structure and high adsorption capacity. Among them, polyamic acid as a suitable precursor for producing polyimides and styrene as a widely used monomer in polymer network synthesis were selected in order to prepare a composite adsorbent with improved properties.
In this study, polyamic acid was synthesized from para-phenylenediamine and benzophenone tetracarboxylic dianhydride in NMP solvent. After precipitation in methanol and drying in a vacuum oven, in order to prepare a semi-interpenetrating network adsorbent, the polymerization reaction of styrene by the bulk method in the presence of the cross-linking agent divinylbenzene and the initiator benzoyl peroxide was carried out on linear polyamic acid, and the resulting powder adsorbent was obtained. By keeping all parameters affecting the adsorption process constant and considering only the type of adsorbent composition percentage as the variable factor, the adsorption amount was examined using an ultraviolet spectrophotometer. In this evaluation, the lowest adsorption value was selected as the optimum composition percentage, which corresponded to the ratio of 60% crosslinked polystyrene and 40% polyamic acid. After selecting the optimum composition percentage, with the help of a statistical method called Taguchi, the adsorption experiments were designed and the effect of four parameters including the initial concentration of methylene blue dye, the amount of adsorbent used, the contact time, and the pH were simultaneously investigated.
The synthesis steps of the adsorbent were performed using FT-IR and NMR techniques, and its performance in the removal of methylene blue dye was examined by ultraviolet spectrophotometry. The experimental conditions included pH equal to 9, initial dye concentration of 80 ppm, adsorbent amount of 1/0 g, and dye solution volume of 20 mL. The adsorption process reached equilibrium within 15 minutes, and the adsorption capacity was calculated to be about 14 mg/g. The recyclability test showed that the adsorption efficiency decreased from 86% in the first cycle to about 75% after five consecutive cycles. Data analysis demonstrated that the adsorption behavior was consistent with the Freundlich isotherm and the kinetics followed the pseudo-second-order model. These results indicate the high potential of the synthesized adsorbent for application in the removal of dye pollutants from aqueous environments.
