Pilot-scale valorization of hazardous aluminum dross into γ-Al2O3 nanoadsorbent for efficient removal of fluoride

In this study, secondary aluminum dross as an alumina-rich resource was valorized into the gamma-aluminum oxide (gamma-Al2O3) via a pilot-scale extraction system. The pilot scale process was designed for a total gamma-Al2O3 production of -5 kg/day. The extraction process included leaching, precipitation, hydroxide separation, aluminum hydroxide re precipitation, drying and high-temperature dihydroxylation The obtained gamma-Al2O3 was then characterized using XRD, XRF, BET, and FESEM. The XRD analysis disclosed the emergence of the gamma-crystalline phase with a crystallite size of 19.6 nm. The XRF revealed a purity of more than 99 wt%. The BET surface area, pore volume, and mean pore size were similar to 170 m(2)/g, 0.45 cm(3)/g, and 17.4 nm, respectively. The FESEM and TEM indicated that the as-synthesized gamma-Al2O3 was in the form of agglomerates, consisting of <20 nm particles. The gamma-Al2O3 was then used to adsorb aqueous fluoride with two different concentrations of 10 and 20 ppm. The adsorption results revealed that the amount of fluoride adsorbed by gamma-Al2O3 was 16.5 mg/g when adsorbent dosage, initial fluoride concentration, pH, and equilibrium time were 1 g/l, 20 ppm, 4, and 1 h, respectively. The maximum monolayer adsorption was obtained 35.6 mg/g by Langmuir model. Investigating the influence of the adsorbent dosage indicated that the adsorbent dosage of 4 g/l resulted in 98% fluoride removal. It was found that fluoride adsorption occurred through chemisorption, and carbonate and phosphate anions had the most interference with fluoride adsorption. The regeneration experiments showed that the regenerated gamma-Al2O3 can exhibit good fluoride adsorption performance, even after 8 times regeneration. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study focused on valorizing secondary aluminum dross into gamma-aluminum oxide (γ-Al2O3) through a pilot-scale extraction system. The obtained γ-Al2O3 exhibited good fluoride adsorption performance, even after multiple regenerations, indicating its potential for practical applications in fluoride removal from water.