Carboxymethyl cellulose sodium/bentonite composite adsorbent for Cd(II) adsorption from wastewater

Severely polluting wastewater containing heavy metal ions has become a pressing issue. To address the current shortcomings of natural bentonite (Bent) and carboxymethyl cellulose sodium (CMC) for Cd(II) adsorption, this study developed a cellulose/bentonite composite adsorbent (CMCMW-Bent) via microwave-assisted synthesis using acrylic acid (AA)-modified CMC and pretreated bentonite (Bent), and the adsorbent was used to remove Cd(II) from wastewater. The results show that the strong interaction between AA and CMC, which successfully entered the bentonite layer, and the bentonite provided excellent structural stability and abundant adsorption sites for the adsorption process. Meanwhile, microwave-assisted heating enhanced this unique structure compared to traditional heating with the aqueous solution. The best adsorption effect occurred at pH = 6–7, with a maximum adsorption capacity of 44.76 mg/g for Cd(II). The isothermal adsorption and kinetic models demonstrate that the adsorption process followed the Langmuir adsorption fitting and pseudo-second-order kinetic equations. The thermodynamic study confirms that the adsorption process was a spontaneous endothermic process and a chemical adsorption process. This study provides a new approach for obtaining efficient adsorbents.