Effects of Humic Acids, Freeze–Thaw and Oxidative Aging on the Adsorption of Cd(II) by the Derived Cuttlebones: Performance and Mechanism

Currently, few studies have revealed the comprehensive effects of environmental organic matter, freeze–thaw and oxidative aging on the adsorption performance of cadmium (Cd(II)), which is essential for the sustainable stability evaluation of the adsorbent. Herein, we observed that humic acids (HAs) extracted from different soils inhibited the adsorption performance of Cd(II) onto the cuttlebone-derived samples by occupying the different major adsorption active sites of the adsorbent, and the lower cadmium-complexation ability of HAs would increase the occupation of adsorption sites. The freeze–thaw process increased the pore size and volume of the cuttlebone-derived samples, while oxidative aging enhanced the specific surface area and introduced additional C–O/C=O groups. These changes promoted the adsorption performance of Cd(II) in the cuttlebone-derived samples after freeze–thaw or oxidative aging. Additionally, the resistances of cuttlebone-based adsorbents to HAs, freeze–thaw, and oxidative aging were elucidated and optimized by simple alkali boiling or carbonization treatment. Furthermore, the adsorption capacities of Cd(II) by samples in the natural cadmium-contaminated river ranged from 548.99 mg g−1 to 571.55 mg g−1, which are higher values than those of most reported adsorbents. Therefore, this work provides an important experimental basis for the practical application and sustainable design of adsorbents under real environmental conditions.