Efficient removal of congo red dye using activated lychee peel biochar supported Ca-Cr layered double hydroxide

Cruz, Estevan D.; Missau, Juliano; Tanabe, Eduardo H.; Collinson, Simon R. and Bertuol, Daniel A. (2023). Efficient removal of congo red dye using activated lychee peel biochar supported Ca-Cr layered double hydroxide. Environmental Nanotechnology, Monitoring & Management

DOI: https://doi.org/10.1016/j.enmm.2023.100835

Abstract

Congo red is a known carcinogenic and mutagenic dye, so its presence in bodies of water is dangerous. The present work aims to synthesize and characterize a layered double hydroxide (LDH)-biochar composite and evaluate its application in the adsorption of Congo red dye (CR). CaCr/LDH was anchored over lychee activated biochar through coprecipitation. The composite was characterized using scanning electronic mapping (SEM), energy-dispersive spectrometer SEM (EDS-SEM), Fourier transform infrared (FT-IR), X-ray powder diffractometry (XRD) and Brunauer-Emmet-Teller (BET). The effect of pH, adsorption kinetics, isotherms, ionic strength, and thermodynamic parameters were evaluated. The pH results show a stable adsorption capacity in a useful range of pH (pH 4-9). Adsorption kinetics fitted the Elovich model, suggesting a heterogeneous system. The maximum adsorption capacity value (qe) calculated was achieved by applying the Sips model, with 631.1 mg g-1 at 50 °C. Ionic strength experiments show that the capacity increased with increasing NaCl concentration, which is desirable for real use as other ions are commonly present in dye wastewater. π-π interactions and hydrogen bonding seems to be involved in the adsorption mechanisms. CaCr-LDH/lychee biochar has better structure stability over several adsorption-desorption cycles with anionic exchange regeneration (in comparison with thermal regeneration), wide operational pH and high adsorption capacity. Therefore, this new composite presents a very good potential for the adsorption of dye from waste- or ground- water.

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