Equilibrium, kinetic, and thermodynamic study of Direct Yellow 12 dye adsorption by biomass-derived porous graphitic activated carbon

Abstract

Abstract Competent treatment techniques were explored to curb the environmental pollution of dye-laden wastewater. In the current study, eucalyptus biomass contemplated as agricultural waste is translated into eucalyptus graphitic activated carbon (EPGAC) using ZnCl 2 at 600 °C in the N 2 atmosphere. The present investigation illustrated awareness about the nature of EPGAC’s dye elimination by employing Direct Yellow 12 dye (DY12) as a model dye. EPGAC was characterized using multiple characterization tools such as Fourier transform infrared spectroscopy (FTIR), Boehm titrations, pH zpc , X-ray diffraction (XRD), Raman, field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDX), high-resolution transmission electron microscopy (HRTEM), and Brunauer-Emmett-Teller (BET) surface area analysis techniques. Electron micrographs disclosed the availability of high pore density for the adsorption of DY12 dyes. BJH analysis reported the distribution of mesopores having a 3 nm diameter on the EPGAC surface. Further, the surface area available for adsorption per gram of the adsorbent is estimated as 178.35 m 2 employing BET analysis. XRD and Raman’s data revealed the graphitic nature of EPGAC. Influences of adsorbent parameters such as EPGAC mass, initial dye concentration, contact time, solution pH, and temperature on the eviction of DY12 by EPGAC were examined to achieve a deeper insight into the adsorption mechanism. The optimum EPGAC adsorbent dose was found to be 0.15 g. The equilibrium was attained at 120 min for DY12 dye. Pseudo-second-order kinetics entirely relates to the perfect fit associated with the investigational results. The aptness of the equilibrium data relevant to the Langmuir adsorption isotherm eventually recommends a maximum unilayer adsorption capacity of 42.01 mg/g for EPGAC. Thermodynamic studies further reveal the spontaneous, endothermic, and chemisorption nature of adsorption. Adsorbent viability was established through stability and recyclability studies carried out up to 5 run cycles with 0.15 g of EPGAC. Adsorption mechanisms were explained considering hydrogen bonding, π-π interactions, and electrostatic interactions, ultimately confirming the adsorption tendency displayed by EPGAC for the eviction of DY12 dye present in industrial wastewater.