Synthesis of biochar-supported zinc oxide and graphene oxide/zinc oxide nanocomposites to remediate tartrazine dye from aqueous solution using fixed-bed column reactor

The treatment of wastewater is a worldwide concern due its large impact on the environment and human health. Among different types of pollutants, textile effluents (dyes) are increasingly of emerging concern, as they are generally resistant to the conventional treatment methods and harmful to the environment. Herein, biochar-caged zinc oxide (BC-ZnO) and graphene oxide/zinc oxide (BC-GO/ZnO) nanocomposites (NCs) were fabricated and employed in current research for the sorption of tartrazine dye from wastewater. To examine the adsorption ability of BC-ZnO NCs and BC-GO/ZnO NCs, the dynamic fixed-bed column mode sorption experiments were executed under the influence of varied experimental factors, viz. flow rate, initial concentration and bed depth. The column performance was determined as breakthrough curves. Maximum adsorptive removal of tartrazine dye onto BC-ZnO and BC-GO/ZnO NCs was 78.85 ± 0.063 and 88.8 ± 0.31 mg/g, respectively, at optimum conditions, i.e. 1.8 mL/min flow rate, 100 mg/L inlet concentration and 5 cm bed height. Breakthrough curves were analyzed via mathematical models, i.e. Bed Depth Service Time (BDST) and Thomas. Thomas model exhibited good agreement to experimental data with R2 = 0.9981 ± 0.008 indicating validity of the model for the column for BC-GO/ZnO NCs. BC-GO/ZnO NCs was regenerated in five consecutive experiments without a significant loss in process efficiency.