*3.6. Consecutive Cycles of Adsorption*

With regard to a circular economy and sustainable application, the great performance of the proposed adsorbent was shown upon performing consecutive cycles of adsorption. By selecting 120 min as the contact time, a 1 <sup>×</sup> <sup>10</sup>−<sup>5</sup> M Kp solution at pH 5 was placed in contact with the adsorbent (150 mg) and, after almost complete adsorption (80% of Kp), the same film was used again to adsorb Kp from another solution at the same concentration. The Kp adsorption percentages reported in Table 3 were obtained. The results indicated that, after eight cycles of adsorption, the NSAID removal was still high, suggesting the possibility of using the same film several times for the removal of the NSAID, thus extending the adsorbent's lifetime.

**Table 3.** Consecutive cycles of adsorption referring to experiments of adsorption in which the Kp concentration was maintained at 1 <sup>×</sup> <sup>10</sup>−<sup>5</sup> M, pH 5, and the amount of chitosan was 150 mg.

