Removal of methylene blue from synthetic aqueous solutions with novel phosphoric acid-doped pyrazole-g-poly(glycidyl methacrylate) particles: kinetic and equilibrium studies

Abstract

Fundamental investigations of the removal of methylene blue (MB) from aqueous solutions by synthesized orthophosphoric acid-doped pyrazole-g-poly glycidyl methacrylate (OPA-Py-g-PGMA) and poly (glycidyl methacrylate) (PGMA) particles of average size 71 and 40 μm, respectively, conducted under batch conditions. The kinetic and equilibrium results obtained for MB sorption with different initial MB concentrations onto synthesized OPA-Py-g-PGMA, and PGMA were analyzed. Kinetic modeling analysis with three different types of kinetic sorption models (pseudo-first-order, pseudo-second-order, simple Elovich, and intraparticle diffusion rate models) was applied to simulate the MB sorption data. The analysis of the kinetic data indicated that the sorption was a second-order process. An ion-exchange mechanism may have existed in the MB-sorption process with the synthesized OPA-Py-g-PGMA. The MB uptake by OPA-Py-g-PGMA and PGMA quantitatively evaluated with equilibrium sorption isotherms. To describe the isotherms mathematically, the experimental data of the removal equilibrium correlated with the Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich (D–R) isotherm models, and the applicability of these isotherm equations to the sorption systems compared by the correlation coefficients. The maximum sorption capacities, determined from the Langmuir isotherm, were 15.15 and 8.67 mg/g at 25°C for OPA-Py-g-PGMA and PGMA, respectively. Moreover, diffusion mechanism of MB was described by different adsorption diffusion models. The diffusion rate equations inside particulate of Dumwald–Wagner and intraparticle models were used to calculate the diffusion rate. The actual rate-controlling step involved in the MB sorption process was determined by further analysis of the sorption data by the kinetic expression given by Boyd.