Utilization of cross-linked chitosan for cobalt adsorption and its reutilization as a photocatalyst for the photodegradation of methyl violet dye in aqueous medium

Removal of heavy metals and dyes from wastewater has received great attention due to scarcity of clean water worldwide. Herein an approach was introduced to attain this goal by employing a single material. Chitosan films were prepared, cross-linked it and utilized for the adsorption of cobalt from aqueous medium. The cobalt adsorbed chitosan was then reutilized as a photocatalyst for the photodegradation of methyl violet dyes. The prepared chitosan, cross-linked chitosan and cobalt adsorbed cross-linked chitosan were characterized through scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). SEM and EDX confirmed the adsorption of cobalt on the cross-linked chitosan. TGA analysis proved the increase in thermal stability with cross-linking while FTIR confirmed the cross-linking of chitosan. Maximum cobalt adsorption of 144 mg/g occurs at 600 ppm salt concentration. The photodegradation study shows that the fresh cobalt adsorbed cross-linked chitosan degraded about 97.78% methyl violet dye within 180 min under UV light, while the recovered degraded about 86.97% within the same time. Efficient degradation was observed at low initial dye concentration and at 30 ppm about 92.16% dye degraded.