Enhanced Removal of Eriochrome Black T Using Graphene/NiMgAl-Layered Hydroxides: Isotherm, Kinetic, and Thermodynamic Studies

In this study, graphene (G) was used as a substrate for NiMgAl ternary-layered hydroxide using coprecipitation technique. The pristine NiMgAl (NMA), graphene-NiMgAl (G/NMA) and their respective calcined products NMA-C and G/NMA-C were investigated as adsorbents for the removal of hazardous eriochrome black T (EBT) dye from an aqueous phase. Characterization results revealed that the incorporation of graphene nanoparticles with NMA with subsequent calcination leads to a significant improvement in surface functionalities, thermal stability, and specific surface area. This resulted in high and fast uptake of EBT molecules from the water phase. The equilibrium time for NMA, NMA-C, G/NMA, and G/NMA-C was achieved at 240 min, 180 min, 90 min, and 60 min, respectively, with optimum pH 4 and dosage of 10 mg. The Langmuir isotherm model describes the adsorption process more appropriately with maximum achievable adsorption capacities of 156.25, 263.16, 238.14, and 384.62 mg/g for NMA, G/NMA, NMA-C, and G/NMA-C, respectively. The kinetic study indicates the adequacy and fitness of the pseudo-second-order model to the experimental data for all four adsorbents. The thermodynamic evaluation substantiates the exothermic nature of the adsorption processes. The mechanism of EBT-G/NMA-C adsorption system involved surface adsorption, electrostatic, strong chemical, and ion exchange interactions along with surface reconstruction. Integration of graphene with subsequent calcination substantially improved the surface and structure characteristics of NMA which facilitated enhanced adsorption performance with sorption rate and excellent reusability performance, confirming it as a highly promising adsorbent for the efficient remediation of dye-contaminated wastewater.