Highly Porous Iron–Zirconium–Zinc Ternary Metal Oxide Scaffold: Facile Synthesis and Efficient Removal of Malachite Green from Water

Abstract

Designing water-stable and sustainable adsorbents for wastewater management has gained significant importance nowadays. This paper reports coprecipitation-induced rapid synthesis of a highly porous ternary metal oxide (TMO), its characterization, and efficient removal of malachite green (MG) from simulated water by a batch method. The material was characterized by the Brunauer–Emmett–Teller (BET) surface area, scanning electron microscopy (SEM), powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, point of zero charge (pHzpc), and chemical analysis. With a high surface area of 185.04 m2/g, TMO offers an excellent adsorption capacity of 133 mg/g under optimized conditions. pH-dependent adsorption was seen, and maximum adsorption was attained at the neutral condition, i.e., pH 7. Intraparticle diffusion (R2 = 0.998) and a combined Langmuir and Freundlich isotherm model (R2 = 0.987–0.998) best describe the adsorption pathway, suggesting that the process undergoes diffusive mass transfer and multilayer adsorption. The adsorption mechanism is proposed to be a combination of electrostatic interaction and hydrogen bonding. Thermodynamic parameters suggest a spontaneous (ΔG, −3.335 kJ/mol), feasible, and exothermic (ΔH, −8.436 kJ/mol) process. The low activation energy (3.459 kJ/mol) suggests a physisorption process. The material can be regenerated up to 83% by 0.1 M hydrochloric acid and reused for up to four cycles without significant loss of activity.