Chitosan@Carboxymethylcellulose/CuO-Co2O3 Nanoadsorbent as a Super Catalyst for the Removal of Water Pollutants

In this work, an efficient nanocatalyst was developed based on nanoadsorbent beads. Herein, carboxymethyl cellulose-copper oxide-cobalt oxide nanocomposite beads (CMC/CuO-Co₂O₃) crosslinked by using AlCl₃ were successfully prepared. The beads were then coated with chitosan (Cs), Cs@CMC/CuO-Co₂O_3. The prepared beads, CMC/CuO-Co₂O₃ and Cs@CMC/CuO-Co₂O₃, were utilized as adsorbents for heavy metal ions (Ni, Fe, Ag and Zn). By using CMC/CuO-Co₂O₃ and Cs@CMC/CuO-Co₂O₃, the distribution coefficients (K_d) for Ni, Fe, Ag and Zn were (41.166 and 6173.6 mLg^-1), (136.3 and 1500 mLg^-1), (20,739.1 and 1941.1 mLg^-1) and (86.9 and 2333.3 mLg^-1), respectively. Thus, Ni was highly adsorbed by Cs@CMC/CuO-Co₂O₃ beads. The metal ion adsorbed on the beads were converted into nanoparticles by treating with reducing agent (NaBH₄) and named Ni/Cs@CMC/CuO-Co₂O₃. Further, the prepared nanoparticles-decorated beads (Ni/Cs@CMC/CuO-Co₂O₃) were utilized as nanocatalysts for the reduction of organic and inorganic pollutants (4-nitophenol, MO, EY dyes and potassium ferricyanide K₃[Fe(CN)₆]) in the presence of NaBH₄. Among all catalysts, Ni/Cs@CMC/CuO-Co₂O₃ had the highest catalytic activity toward MO, EY and K₃[Fe(CN)₆], removing up to 98% in 2.0 min, 90 % in 6.0 min and 91% in 6.0 min, respectively. The reduction rate constants of MO, EY, 4-NP and K₃[Fe(CN)₆] were 1.06 × 10^-1, 4.58 × 10^-3, 4.26 × 10^-3 and 5.1 × 10^-3 s^-1, respectively. Additionally, the catalytic activity of the Ni/Cs@CMC/CuO-Co₂O₃ beads was effectively optimized. The stability and recyclability of the beads were tested up to five times for the catalytic reduction of MO, EY and K₃[Fe(CN)₆]. It was confirmed that the designed nanocomposite beads are ecofriendly and efficient with high strength and stability as catalysts for the reduction of organic and inorganic pollutants.