Adsorption of Congo red azo dye on nanosized SnO2 derived from sol-gel method

The nanoparticles tin oxide (SnO2) has been successfully synthesized via a sol-gel method. The as-prepared SnO2 was characterized using thermogravimetric analysis coupled with mass spectroscopy, X-ray diffraction and scanning electron microscope. Batch experiments were carried out to study the adsorption kinetics of Congo red azo dye on SnO2. The effect of varying parameters such as contact time, initial dye concentration and adsorbent dose on the adsorption process was investigated. The results showed that the SnO2 catalysts has high crystallinity with tetragonal rutile structure and average particle size about 13-23 nm. The untreated sample SnO2-80 exhibited high efficiency (84.41 %) after 60 min of exposure time, which was 2 times as much as that of SnO2-450 sample. The adsorption process was found to be highly dye concentration and adsorbent dose dependent. Pseudo-second-order kinetic model gave the best fit, with highest correlation coefficients (R-2 >= 0.99). Regarding the adsorption equilibrium, the experimental results suggest that the Langmuir model was applicable. The formation of hydrogen bond and the electrostatic interaction between the Sn2+ center and the electron rich nitrogen atoms of CR moiety were believed to be the main adsorption mechanism. These findings should be valuable for designing effectively adsorbent material and practical interest in terms of ecology and sustainable development.