Alginate-coated perlite beads for the efficient removal of methylene blue, malachite green, and methyl violet from aqueous solutions: kinetic, thermodynamic, and equilibrium studies

Abstract

Environmental pollution has been increasing recently due to industrialization. Many industries use dyestuffs to color their products. This work investigates the adsorption of methylene blue (MB), malachite green (MG), and methyl violet (MV) on alginate-coated perlite beads (AP). AP was prepared by a sol-gel process. The removal of MB, MG, and MV from aqueous solutions by AP as an adsorbent was tested by using a batch-type model. In order to prove the effectiveness of the study, it has been tried to obtain optimum efficiency at optimum level by working depending on mixing time (minutes), initial dye concentration (ppm), adsorbent dose (mg/L), pH, and temperature (°C). The results showed that the MB, MG, and MV adsorption process reached equilibrium within a 60-min period for AP. It has been found that the amount of adsorbed dyestuff increases with the initial dye concentration, the pH of the solution. Thermodynamic activation parameters were calculated from experimental data at different temperatures. The AP was characterized by Fourier Transform Infrared Spectroscopy (FT-IR) before and after MB, MG, and MV adsorption. The equilibrium adsorption data were described by Langmuir, Freundlich, Scatchard, Temkin and D-R isotherms. The modified Langmuir isotherm was applied to explain the experimental adsorption, and the greatest MB, MG, and MV adsorption capacity of the AP reached to 104.1, 74.6, and 149.2 mg/g, respectively. The pseudo-first and pseudo-second-order equations were used to evaluate the kinetic data, and the constants are determined. The best correlation coefficients were well described using the pseudo-second-order kinetic model. As a result, AP has claimed the possibility as an adsorbent for MB, MG, and MV removal from dilute aqueous solutions.