Novel chitosan-magnetite-silica ternary capsules for highly efficient sequestration of reactive dyes from aqueous...

The main goal of this study was to synthesize novel Chitosan Magnetite Silica (CMS) adsorbent capsules and apply them for effective sequestration of anionic dyes Remazol brilliant blue 19 (RB-19) and Remazol golden yellow G -17 (RY-17) dye. The CMS capsules were synthesized and applied for batch study and evaluated using statistical modelling. Various analytical techniques, such as Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Thermogravimetry-Differential Thermal Analysis (TG-DTA), Brunauer-Emmett-Teller (BET) surface area analysis, UV-Vis Spectrophotometry, and Vibrating Sample Magnetometry (VSM), were employed to validate the formation of the CMS. Rough surface as shown by SEM analysis, presence of various functional groups as shown by FT-IR spectrum and presence Fe atoms in EDX spectrum are indication of formation of complete composite. The surface area of CMS recorded by BJH method was 39.05 m² g^-1 with pore capacity 0.259 cm³ g^-1. According to IUPAC classification, class IV isotherm was observed for nitrogen adsorption-desorption curves. The specific magnetization of CMS was 4.28 emu g^-1 indicating fare degree of magnetism making it easily separable using external magnet. Batch trails as well as screening experiments were conducted for the sequestration of RB and RY dyes. Dose 50 mg, interface time 60 min and solution pH of 3.0 depicted maximum removal efficacy of more than 95 % in both dyes even at high initial concentration of 200 mg L^-1. The adsorption capacities for RB-19 dye and RY-17 dye were found to be 455.86 and 344.06 mg g^-1 respectively in accordance with pseudo second order kinetics (R² = 0.997 and 0.962 respectively) and Langmuir adsorption isotherm (R² = 0.972 and 0.992 respectively) models. Six adsorption-desorption cycles were conducted for regeneration potential of CMS showcasing repeated usability after regeneration in alkaline medium. E-factor value of 0.04 depicted CMS capsules was sustainable in and eco-friendly with low waste generation.