Development of novel nano-γ-Al2O3 adsorbent from waste aluminum foil for the removal of boron and bromide from aqueous solution

Abstract

The current study deals with the synthesis of nano-gamma-alumina (nano-γ-Al2O3) from waste aluminum foil and its application for the removal of boron and bromide from an aqueous solution. The physical characteristic of nano-γ-Al2O3 was analyzed using various analytical techniques, namely thermogravimetric analyzer (TGA), scanning electron microscope (SEM), energy dispersive X-ray (EDX), and Fourier-transform infrared spectroscopy (FTIR). Additionally, various important parameters that govern the adsorption process were examined, such as pH, solution temperature, and initial ions concentration. It was found that boron preferred a basic environment while bromide prefers a less acidic environment. The prepared adsorbent also demonstrated a very high removal efficiency; 88.35 % of boron and 87.65 % of bromide were achieved. Isotherm studies showed that the Langmuir model best explained the adsorption processes for both boron and bromide at 25 °C. The maximum boron and bromide adsorption capacities (Langmuir adsorption capacity) were 25.86 mg/g (at 35 °C) and 90.72 mg/g (at 25 °C), respectively. Moreover, the evaluated thermodynamic parameters revealed that boron followed an endothermic reaction while bromide followed an exothermic reaction. The ΔG° value for both ions indicated that adsorption was favorable. While the kinetic studies revealed that both, boron and bromide adsorption onto nano-γ-Al2O3 obeyed pseudo-second-order; indicating that electrostatic forces and electron sharing would be amongst the major forces involved in the adsorption process. The desorption experiments confirmed that the spent adsorbents can be regenerated and effectively reused. The prepared nano-γ-Al2O3 was also tested with a real groundwater sample, and it was found that 96.25 % of boron and 100 % of bromide were successfully adsorbed using nano-γ-Al2O3. Additionally, it was also found that 99 % of sulfate ions were removed. This showed that the prepared adsorbent has the tendency to adsorb multiple ions from the real groundwater sample.