Facile preparation of floatable carboxymethyl cellulose-based composite hydrogel for efficient removal of organic dyes

Hydrogels have become efficient adsorbents in treatment of organic dyes from wastewater. However, the drawback of difficulty in separation and collection limited their applications. Herein, a series of floatable polyacrylamide/carboxymethyl cellulose‑copper sulfide (PAM/CMC-CuS) hydrogels were designed. The PAM/CMC-CuS hydrogel could not only be easily collected from the wastewater, but also selectively adsorb cationic dyes (Rhodamine B (RhB) and Neutral red (NR)) from the mixed solutions with different oppositely charged dyes. PAM/CMC-CuS hydrogel exhibited faster adsorption rate and higher adsorption capacity than that of PAM/CMC hydrogel. And the adsorption kinetic data were well described by pseudo-second-order model and adsorption isotherm data fitted well with Langmuir equation. Besides, PAM/CMC-CuS hydrogel exhibited excellent reusability and stability that no apparent decrease in removal efficiency was observed after five cycles. Altogether, the good adsorption capacity, floatability, selectivity and reusability will promote the PAM/CMC-CuS hydrogel to be a superior adsorbent in removal cationic dye from wastewater.