Adsorptive Removal of Hazardous Eriochrome Black T and Its Metal Complexes from Aqueous Media Using Spent Coffee Grounds

Abstract An adsorbent was prepared from the spent coffee grounds (SCG) waste by simple washing and tested for its effective use as a low-cost adsorbent for removing eriochrome black T, an azo dye from wastewater, and its metal ion complexes that might be present in industrial water. Various factors were assessed, such as contact time, pH, adsorbent dose, initial dye concentration, and temperature using a batch method and fixed bed column adsorption. Fourier-transformed infrared (FTIR) spectroscopy, (SEM) scanning electron microscope, and BET techniques were employed for characterization. The adsorption capacity of EBT at an equilibrium time was 4.95 mg/g and for [EBT-Zn+ 2], [EBT-Pb+ 2], and [EBT-Cu+ 2] complexes were 4.53, 4.72, and 4.70 mg/g, respectively. In the column study, the adsorption capacity increase for EBT and [EBT-Zn+ 2] at a flow rate of 3 ml/min to be 143.8 and 138.4 mg/g. The removal of EBT and its complexes were illustrated by the kinetic data in a good fit with the models of pseudo-second-order and Freundlich isotherm. The calculated thermodynamic parameters such as ΔG°, ΔH°, and ΔS° showed that the adsorption of EBT and EBT-M was feasible, spontaneous, and exothermic at a temperature range of 298–333 K. The results from this study confirmed the effectiveness of inexpensive and eco-friendly waste as an option for the adsorption and remediation of polluted water.