**4. Desorption conditions and Reuse**

Chitosan adsorbents present considerable advantages such as their high adsorption capaci‐ ty, selectivity and also the facility of regeneration. The regeneration of the adsorbent may be crucially important for keeping the process costs down and to open the possibility of recov‐ ering the pollutant extracted from the solution. For this purpose, it is desirable to desorb the adsorbed dyes and to regenerate the chitosan derivative for another cycle of application. Generally, the regeneration of saturated chitosan for non-covalent adsorption can be easily achieved by using an acid solution as the desorbing agent. Researchers proposed to desorb the dye from the beads by changing the pH of the solution [52,53] and they showed that the beads could be reused five times without any loss of mechanical or chemical efficacy. The optimum pH of desorption was determined to be the contrast of the optimum of adsorption [53]. Another study has shown the desorption capability of chitosan even at the same pH conditions as those of adsorption [3]. In the same study, 10 cycles were achieved with no significant loss of re-adsorption capacity (~5% loss between 1st and last cycle).
