Gallic acid-conjugated iron oxide nanocomposite: An efficient, separable, and reusable adsorbent for remediation of Al (III)-contaminated tannery wastewater

Although persistently neglected, aluminum (Al (III)) contamination in tannery wastewater remains a significant environmental problem. In the present work, gallic acid, a naturally-occurring polyphenol compound capable of coordination with Al (III), was conjugated onto the surface of engineered iron oxide nanoparticle, with the aim of designing a separable and reusable nanoadsorbent applicable for remediating Al (III)-contaminated tannery wastewater. The synthesized nanocomposite (Fe3O4/TEOS/AMEO/GA) was characterized by multiple techniques. The results showed that the conjugation of gallic acid was successful, and the nanocomposite had a high specific surface area as well as a saturated magnetization value strong enough for them to be fast separated by an external magnetic field. Furthermore, adsorption experiments showed that Al (III) adsorption on Fe3O4/TEOS/AMEO/GA was pH-, adsorbent dose-, initial Al (III) concentration-, and coexisting substances- dependent. In addition, kinetics and equilibrium study were conducted to reveal the mechanism by which Al (III) was adsorbed. By chemical desorption, the nanoadsorbent could be regenerated and reused for five consecutive cycles without significantly compromising its adsorption capability. Finally, it was found that Al (III) removal percentage from real tannery wastewater averaged 93.3 ± 1.2%, and the exhausted nanoadsorbent could be separated rapidly from the wastewater via a simple magnetic process.