Feasibility of sugarcane bagasse/polydopamine as sustainable adsorbents for Cr(VI) with reusability in cement composition

Abstract

The removal of pollutants from water should be followed by a proper treatment of the spent adsorbents. In this study, sugarcane bagasse/polydopamine (SB/PDA) adsorbents were applied in batch and column adsorption studies towards Cr(VI) ions. Adsorbents prepared with higher concentration of dopamine (4 g.L−1) led to more efficient adsorbents (SB/PDA4) and maximum adsorption capacity (qmax) of 138 mg.g−1. X-ray photoelectron spectroscopy (XPS) analyses revealed that the adsorption mechanism involved ion-dipole and electrostatic interactions between Cr(VI) and the PDA functional groups. The spontaneous (ΔGads - 9 kJ mol−1) adsorption process was driven by an entropic gain related to the release of counter-ions and water molecules. Under optimized operational conditions, the maximum adsorption capacity in the fixed-bed column achieved the adsorption capacity of 141.7 mg.g−1. Considering the circular economy principles, the contaminated adsorbents were incorporated to cement pastes. No leaching of Cr(VI) from the cement/adsorbent samples could be detected over 64 days, and their mechanical behavior was comparable to the reference cement samples. The efficient removal of Cr(VI) from wastewater by SB/PDA adsorbents and the successful incorporation of spent adsorbents to cement demonstrated a sustainable management of liquid and solid wastes.