Adsorbents from sustainable precursors are highly desirable for practical applications. In this study, carboxymethyl cellulose (CMC) and humic acid (HA) were adopted to fabricate a composite immobilized on precipitates of calcium hydroxide (PCH) and ferric hydroxide (PFH). The as-obtained adsorbent, denoted as HA-CMC/PMH (PCH and PFH were referred to as PMH), was analyzed by infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and thermo gravimetric analysis. When applying for a typical organic pollutant of methylene blue (MB) removal from aqueous solution, a high adsorption capacity of 666.67 mg/g was achieved over HA-CMC/PMH. The adsorption mechanisms of MB involved ion exchanging and π-π interactions, this adsorption process mainly occurred on both anionic and aromatic groups. Adsorption behavior analysis indicated that Langmuir isotherm model and pseudo-second order kinetic model fitted experimental data well, suggesting a mono-layer adsorption of MB onto the adsorbent. Further thermodynamic analysis proved that the adsorption of MB onto HA-CMC/PMH was an exothermal spontaneous process. The developed adsorbent is also reusable with 79.93% of adsorption capacity remaining in the fifth recycle runs. Therefore, the adsorbent of HA-CMC/PMH is suggested to be a promising candidate for adsorption applications.
Keywords: Adsorption; Carboxymethyl cellulose; Humic acid.
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