An adsorbent based on humic acid and carboxymethyl cellulose for efficient dye removal from aqueous solution

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.