Fibrous adsorbent derived from sulfonation of cotton waste: application for removal of cadmium sulfide nanoparticles from aquatic media

Abstract

In the present research, the performance of the cellulose sulfate microfibers (CSMFs) was investigated for the removal of cadmium sulfide nanoparticles (CdS NPs). At first, cotton waste was sulfonated by chlorosulfonic acid. The high sulfur content of the CSMFs (6.54%) and the absorbance bands appeared at 610 cm−1 (symmetric stretching vibrations) and 1205 and 1180 cm−1 (asymmetric stretching vibrations) in the FT-IR spectrum of CSMFs confirmed the successful modification of cotton microfibers. Optimizing the adsorption process was achieved using the response surface methodology. The impacts of the initial concentration of CdS NPs, contact time, total dissolved solids (TDS), and adsorbent concentration on the removal efficiency were assessed. The highest removal efficiency (about 100%) was obtained under optimum conditions. By increasing the TDS, the removal efficiency decreased slightly. University of Tehran, Radke–Prausnitz, and Redlich–Peterson models exhibited low error values. The high maximum adsorption capacity of 5533 mg g−1 was due to the high content of anionic surface groups. The kinetics data were consistent with the Elovich, intraparticle diffusion, and pseudo-second-order models. The rate constant of the pseudo-second-order model decreased by decreasing the concentration of CdS NPs. The adsorbent recovery decreased about 10% after four cycles of regeneration.