Feasibility of sugarcane bagasse/polydopamine as sustainable adsorbents for Cr(VI) with reusability in cement composition
Mário A. B. S. Nunes, Dairon Pérez Fuentes, José Augusto Ferreira Sales de Mesquita, Roberto Romano, Rafael Giuliano Pileggi, Pedro V. Oliveira, Denise Freitas Siqueira Petri
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.