Investigation of indigo carmine removal with synthesized polymer

In this study, the removal of indigo carmine (IC), which is a highly toxic indigoid dyestuff, from wastewaters was investigated by using adsorption process. For this purpose, a new adsorbent was prepared by free radical copolymerization of 2-(dimethylamino) ethyl methacrylate (DMAEMA) and acrylonitrile (AN) using 2,2'-azobisisobutyronitrile (AIBN) as initiator. The synthesized adsorbent poly (2-(dimethylamino)ethyl methacrylate)-co-acrylonitrile) briefly poly(DMAEMA-co-AN); was characterized by Fourier transformed infrared spectrophotometer (FT-IR), proton NMR spectroscopy (1H-NMR) and scanning electron microscopy (SEM). The thermal properties of the adsorbent were determined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The effects of parameters such as pH (3-9), temperature (25-45 °C), adsorbent dosage (0.05-2.5 g/100 mL), initial IC concentration (25-100 mg /L) on adsorption were investigated. The highest removal efficiency was found as pH 7, 25 °C temperature and 0.1 g/100 mL adsorbent dosage and 99.50% for 25 mg/L initial IC concentration. Adsorption equilibrium was analyzed by using Freundlich and Langmuir isotherm models and adsorption was found to be better fitted with Langmuir isotherm (R2 = 0.99). The maximum adsorption capacity was found to be 188.67 mg/g. Mass transfer and kinetic models were applied to determine the potential steps that control the adsorption mechanism and reaction rate. Both the external mass transfer and the intra-particle diffusion played an important role on the adsorption mechanism of the IC and the adsorption kinetics followed the pseudo second-order kinetic model. Thermodynamic parameters (ΔH°, ΔG°, ΔS°) which showed the adsorption of IC occurred spontaneously and in the exothermic nature were determined. The results of this study showed that poly(DMAEMA-co-AN) synthesized in the laboratory can be used as an effective adsorbent for the removal of IC from aqueous solutions.