Properties and performance of Ni(II) doped magnetic Fe3O4@mesoporous SiO2/UiO-66 synthesized by an ultrasound assisted method for potential adsorbent of methyl orange: Kinetic, isotherm and thermodynamic studies

Abstract

Ni(II) doped magnetic Fe3O4@mesoporous SiO2/UiO-66 composite (FSUNi(x)) was synthesized by ultrasound methods for methyl orange (MO) adsorption. Ultrasound irradiation caused the in situ growth of Ni on Fe3O4 @mesoporous SiO2/UiO-66 composite. Ni enhanced the surface area and porosity of composites due to the substitution of Zr in UiO-66 with Ni, which generates defects. The SEM and TEM analysis exhibited the Fe3O4 @mesoporous SiO2 core of ∼324 nm diameter, coated with a Ni-UiO-66 shell of ∼ 23 nm thickness. At 10% nickel doping, FSUNi(10) composites showed high surface area, large pore diameter, excellent adsorption capacity, and high magnetic properties (8.16 emu/g) that achieved rapid recovery in 20 s. The influence of contact time (1–120 min), dye concentration (25–350 mg/L), pH of the initial solution (2−13), adsorption temperature (30–50 °C), and ionic strength (0–3 g/L) on the adsorption capacity were determined to understand the kinetic and thermodynamic of adsorption. The maximum adsorption capacity increased from 200.803 to 256.410 mg/g with increasing temperature from 30° to 50°C, and adsorption reached optimum capacity at pH 4. According to isothermal and kinetic analyses, adsorption follows the Langmuir isotherm model and the pseudo second order kinetic model. Based on the Langmuir isotherm model, the maximum adsorption capacities of UiO-66 and FSUNi(10) were determined at 182.815 and 200.803 mg/g, respectively. Thermodynamic analysis revealed the spontaneous and endothermic adsorption of MO dye on FSUNi(10). FSUNi(10) showed high adsorption capacity after three regeneration cycles, which can be a potential magnetic adsorbent for wastewater treatment.