An iron rotating disk for the elimination of hexavalent chromium ion from industrial wastewaters: putting it to work

• Published in: Desalination and water treatment 2022-09, Vol.270, p.83-91
• Main Authors: El-Ali Al-Waqfi, Mohammed S., Al-Qodah, Zakaria
• Format: Article
• Language: English
• Subjects: Chromium removal; Cr(VI) reduction; Industrial wastewater treatment; Rotating disk
• ISSN: 1944-3986
• DOI: 10.5004/dwt.2022.28760

This work aimed to predict the optimal operational limits for reducing Cr(VI) to Cr (III) ions using an iron rotating disk. Therefore, the kinetics of Cr (VI) reduction utilizing an iron rotating disk were studied under various experimental conditions of contact time, rotation rate, Cr (VI) initial concentration, and disk surface area. All the experiments were conducted at room temperature with a starting pH of 1.5. It was revealed that the reduction of Cr (VI) to Cr (III) could be modeled with a first-order reaction rate. It was found that the reduction rate constant first increased steadily (i.e., mass transfer-controlled) with the square root of the disk’s rotation speed but then fell as the flow transitioned to turbulence until it became relatively unchanged (i.e., kinetics-controlled). Furthermore, the rate constant inversely varied with initial concentration up to 300 mg/L, but then remained unaffected as the concentration increased. The disk radius also influenced the time required to completely remove Cr (VI). It decreased as the radius of the disk increased. As a result, achieving high removals of Cr (VI) in a short contact time requires operating the disk in laminar and transitional flows (Re no. maximum 150,000), as well as optimum Cr (VI) initial concentration, rotation speed, and disk area. Because it can be used in batch or integrated into a continuous treatment system, the rotating disk may offer a potentially practical and unique technique for treating wastewaters with high and low concentrations of Cr (VI) ions.