Hybrid reactor based on hydrodynamic cavitation, ozonation, and persulfate oxidation for oxalic acid decomposition during rare-earth extraction processes

Jongbok Choi; Mingcan Cui; Yonghyeon Lee; Junjun Ma; Jeonggwan Kim; Younggyu Son; Jeehyeong Khim

doi:10.1016/j.ultsonch.2018.12.004

Hybrid reactor based on hydrodynamic cavitation, ozonation, and persulfate oxidation for oxalic acid decomposition during rare-earth extraction processes

Ultrason Sonochem. 2019 Apr:52:326-335. doi: 10.1016/j.ultsonch.2018.12.004. Epub 2018 Dec 4.

Authors

Jongbok Choi¹, Mingcan Cui¹, Yonghyeon Lee¹, Junjun Ma², Jeonggwan Kim³, Younggyu Son⁴, Jeehyeong Khim⁵

Affiliations

¹ School of Civil, Environmental, and Architectural Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea.
² Nanjing Green-Water Environment Engineering Limited by Share Ltd, 211500, People's Republic of China.
³ Korea Environmental Industry and Technology, Seoul 03367, Republic of Korea.
⁴ Department of Environmental Engineering, Kumoh National Institute of Technology, 61 Daehak-ro Gumi, Gyeongsangbuk-do 39177, Republic of Korea.
⁵ School of Civil, Environmental, and Architectural Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea. Electronic address: hyeong@korea.ac.kr.

PMID: 30660376
DOI: 10.1016/j.ultsonch.2018.12.004

Abstract

A cost-effective method for treating oxalic acid (OA) during rare-earth extraction was developed using hydrodynamic cavitation (HC), ozone (O₃), and persulfate (PS) (HC@PS@O₃ process). The results showed that the optimal inlet pressure during HC was 5.10 kg cm^-2 with an orifice plate diameter of 2 mm. Moreover, HC was shown to activate PS, providing an alternative activation method to base or heat as an ultrasound activation method for chemical oxidation. O₃ was also shown to activate PS. For OA oxidation using the HC@PS@O₃ process, the optimum pH was 3 and the reaction rate increased with increasing temperature. Further, the activation energy was 36.69 kJ mol^-1. The mechanisms unveiled in this study will allow optimization of the HC@PS@O₃ process as a chemical oxidation technology. The kinetic investigation and economic evaluation of the HC@PS@O₃ process can be used as the basis for real wastewater treatment processes in the future.

Keywords: Hydrodynamic cavitation@persulfate@ozone process; Hydroxyl radical; Ozone; Persulfate; Rare-earth extraction wastewater; Sulfate radical.