Adsorption characteristics of chitooligosaccharides onto activated charcoal in aqueous solutions

To investigate the adsorption characteristics of chitooligosaccharides in solution onto activated charcoal, we studied the optimal adsorption conditions and the adsorption mechanisms of the chitooligosaccharides onto activated charcoal, which will greatly promote the application of activated charcoal in the chitooligosaccharides separation and purification. We studied the effects of particle size of activated charcoal, pH of solution, contact time, temperature, and initial concentration of chitooligosaccharides on the adsorption behavior in batch mode experiments. Activated charcoal in fine particle size showed a high uptake of chitooligosaccharides. Weak alkaline solution (pH 8-9) was the most favorable to the adsorption. The adsorption equilibrium after 60 min was established, which followed a pseudo-second-order kinetic model. The adsorption capacity (Q(max)) reached 0.195 g/g (chitooligosaccharides/activated charcoal) at 298 K. The adsorption was temperature-insensitive, and the adsorption isotherms could be best described by the Langmuir equation. Chitooligosaccharides adsorbed on activated charcoal could be desorbed in 50% ethanol solution in combination with an acidic condition (pH 2), reaching desorption efficiency of 96.0%. These findings are of great significance for the production and purification of amino oligosaccharides including chitooligosaccharides using activated charcoal.