Decolorization of tea industry wastewater utilizing tea waste bio-adsorbent in fixed-bed adsorption column: breakthrough curves analysis and modeling

The proper disposal of wastewater with colored discharge from tea industries is of major significance to the environment and aquatic life. In this study, colored effluent wastewater from the tea industry was treated using an efficient acid-modified bio-adsorbent in a fixed-bed adsorption column. The adsorbent is made from tea waste and is characterized using sophisticated techniques, such as FESEM-EDX, FTIR, and XPS. At a constant input flow rate of 4 mL/min, the adsorption column's performance was examined at three different influent color concentrations of 545.8 mg/L, 615.5 mg/L, and 916.8 mg/L and bed heights of 17.5 cm, 19 cm, and 22 cm. At a bed depth of 22 cm, a maximum color removal of 87.71%, breakthrough time of 840.0 min, exhaustion time of 1440 min, and adsorption capacity of 385.97 mg/g were achieved with an initial concentration of 916.8 mg/L. It was shown that a breakthrough occurred more quickly when inflow concentration was higher while a breakthrough occurred more slowly when bed depth was higher. The adsorption experimental data was fitted with the models of Thomas, Yoon–Nelson, Adams–Bohart, and Yan. The Yan model is found to be the best-fitting (R² > 0.9) model. The wastewater has significantly changed the various physicochemical parameters after adsorption, such as total dissolved solids (TDS) from 279 to 93 mg/L, electrical conductivity (EC) from 570 to 887 (µs/cm), dissolved oxygen (DO) from 1.4 to 7.4 mg/L, biochemical oxygen demand (BOD) from 210.4 to 12.81 mg/L, chemical oxygen demand (COD) from 1052 to 64.29 mg/L, and color (L^*: 25.72–97.23; a^*: 35.93–2.47; b^*: 57.34–4.24) after adsorption. The bio-adsorbent made from tea waste offers great potential for treating wastewater from the tea industry at a reasonable cost on an industrial scale.