Recovery of Chromium(VI) Oxyanions from Aqueous Solution Using Cu(OH)2 and CuO Embedded Chitosan Adsorbents

Abstract

Owing to its availability, low cost and strong reducibility capacity, chitosan can be widely used for Cr(VI) recovery, in this study the removal of Cr(VI) from aqueous solution was investigated using composite adsorbents derived from chitosan (obtained from shrimp peels) and Cu(OH)2 or CuO (prepared by alkaline precipitation of Cu(II) ions) to manufacture ChiCu(OH)2 and ChiCuO, respectively. The adsorbents were characterized by using SEM, BET surface area and zeta potential measurements. Adsorption uptake was highly dependent on pH, temperature, Cr(VI) concentration and sorbent mass: The optimum pH for Cr(VI) removal being close to 4. The adsorption isotherm can be described by Langmuir adsorption isotherm while the uptake kinetics was highly fitted with the pseudo-second order rate equation. The effect of temperature was also evaluated, verifying the endothermic nature of the adsorption process. Chromium desorption was performed using alkaline saline solution (20 g L−1 NaCl with the pH set to 12 with NaOH). The recycling of the sorbent was tested, maintaining a removal efficiency and a metal recovery over 90% for three successive adsorption/desorption cycles. The results showed that, the fabricated nanocomposites are promising adsorbents for Cr(VI) from aqueous solution.