Biosorption of Congo Red dye from aqueous solutions using pristine biochar and ZnO biochar from green pea peels

Abstract

To minimize the catastrophic influence of contaminated water, smart technology-based wastewater treatment processes are mandatory for safe water and sanitation. Nanometric metal oxides supported with biochar are green choices for futuristic adsorbents for water decontamination with versatility, simplicity, high surface reactivity, and efficacy. In this study, reactive Congo Red (CR) from an aqueous solution was decontaminated using prepared innovative green pea peels biochar (GPBC), and zinc oxide green pea peels biochar nanocomposite (ZnO/GPBC). The characterizations of GPBC and ZnO/GPBC were performed by EDX, TEM, XRD, BET, FTIR, and point of zero charge. The role of experimental conditions of initial concentration (50–250 mg/l), GPBC and ZnO/GPBC dosage pH (2−12), temperature (20–60 oC) and interaction time (0–90 min) were examined. The results revealed that ZnO/GPBC demonstrated better performance for anionic CR dye removal that recorded as 98% compared to 90% using GPPBC under optimized environment conditions. The examination of adsorption equilibrium isotherm displayed the validity of Freundlich and Langmuir model for description the dye decolorization onto ZnO/GPBC and GPBC, respectively, as best fitted models. Moreover, the kinetics studies disclosed pseudo-second-order (PSO) for both studied materials. The monolayer sorption capacities were 114.94 mg/g for ZnO/GPBC and 62.11 mg/g for GPBC, both exhibiting competitive performances with other carbon-based adsorbents available in the literature. The thermodynamic studies disclosed favorable, spontaneous, and endothermic processes. The synthesized ZnO/GPBC and GPBC are excellent adsorbents recommended for large-scale production in the removal of anionic dyes from wastewaters.