*2.7. Adsorption Capacity of MO*

To study adsorption and desorption cycles, adsorption was performed under the best conditions (pH, time, and concentration) and desorption was performed using 40 mL of HCl (0.1 mol L<sup>−</sup>1) as eluent during 30 min of constant agitation at 200 rpm. Each adsorption and desorption was then centrifuged for 10 min at 9000 rpm in a centrifuge, measuring the concentration of the supernatant by a UV-visible spectrometer (model BK-UV1800, BIOBASE, Jinan, Shandong, China).
