Sorption of methylene blue by carboxymethyl cellulose and reuse process in a secondary sorption

The sorption behaviors of carboxymethyl cellulose (CMC) for methylene blue (MB) were investigated in this work. The experimental results indicated that the sorption capacity increased from 50 mg g−1 for unmodified cellulose (UmC) to more than 300 mg g−1 for CMC. The most favorable sorption of MB was observed at an alkaline condition. The sorption isotherms closely followed the Langmuir mode, and the sorption kinetics was in agreement with the pseudo-second order equation. The results from the batch experiments illuminated that the sorption mechanism was ion-exchange controlled process. In fixed-bed tests, CMC also exhibited high efficiency for removal for MB, in which sorption behaviors followed Thomas model. Desorption of the dye from the MB-sorbed CMC (MBsCMC) indicated that MBsCMC was stable, and MB was seldom released at neutral and alkaline conditions. Furthermore, a more efficient method for reuse of the disused sorbents was tried. MBsCMC was employed for removal of methyl orange (MO) in a secondary sorption at neutral or alkaline conditions. The maximal MO uptake of MBsCMC was over 100 mg g−1, which was much higher than those of CMC and UmC. It was indicated that MBsCMC was efficient in sorption of MO for the electrostatic interaction between MO and MBsCMC, and secondary sorption was an appropriate way for reuse of this kind of disused sorbents.