In this research
work, methylene blue (MB) was removed by an as-synthesized
graphene oxide-cellulose nanowhisker hydrogel (GO–CNW) nanocomposite
as an adsorbent. Adsorption experiments were conducted under different
MB concentrations, temperatures, shaking rates, ionic strengths, and
alkalinities. Maximum adsorption capacities (q
e,max) of the adsorbent at 308, 318, and 328 K were 34.5, 35.3,
and 34.8 mg·g–1, respectively. The structural
character of the adsorbent, analytical instrumental analyses, and
adsorption models and equations showed that there were two adsorption
sites on the surface of GO–CNW-adsorbed MB molecules. These
adsorption sites were carboxylate and phenoxide groups of the GO portion
of GO–CNW, which were named the CA and Ph adsorption sites,
respectively. An analysis of adsorption isotherms by the ARIAN model
showed that MB molecules were adsorbed at first on the CA and then
on the Ph sites. The interaction of MB molecules with CA sites was
stronger than that with Ph sites. On the other hand, the study of
kinetic curves by the KASRA model and the KASRA, intraparticle diffusion,
and the ISO equation showed that CA sites adsorbed MB molecules more
rapid than did Ph sites. Furthermore, the adsorption on both CA and
Ph sites was reaction-controlled. Finally, the used adsorbent samples
were recycled using acidic solutions.
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