Pentaazatetraethylene supported polyacrylamide (PAA-N5) as a novel adsorbent for the efficient removal of industrial dyes from aqueous solutions: adsorption isotherms and kinetics

Abstract

Modified cross-linked polyacrylamide (PAA) with pentaazatetraethylene group (N5) was used as a chelating agent for the removal of Congo red (CR) and Calmagite (CG) as industrial dyes from aqueous solutions. The proposed adsorbent, PAA-N5, was prepared by transamidation reaction in aqueous and non-aqueous media by Hofmann reaction. All experimental conditions including adsorbent dosage, contact time, pH value, and initial dye concentration were optimized to get efficient removal of dyes. The removal of CR and CG is pH dependent and the optimum pH values for the maximum removal efficiencies were found to be 7.0. The experimental isotherm data were analyzed using Langmuir, Freundlich, and Temkin isotherm models. The results showed that the adsorption behavior of CR and CG on PAA-N5 was well fitted with the Langmuir model at 25 °C and the maximum adsorption capacities were obtained for CR and CG to be 396.07 and 1980.1 mg/g, respectively. The kinetic adsorption rates were modeled using the pseudo-first order, pseudo-second order, and intra-particle models. It was found that the intra-particle and pseudo-second order model were well fitted for CR and CG adsorption with highest correlation coefficients, respectively.