Characterizing the Suitability of Granular Fe⁰ for the Water Treatment Industry

• Main Authors: Rui Hu, Xuesong Cui, Minhui Xiao, Pengxiang Qiu, Mesia Lufingo, Willis Gwenzi, Chicgoua Noubactep
• Format: Article
• Language: English
• Published: MDPI AG 2019-09-01
• Series: Processes
• Subjects: 1,10-phenanthroline; ethylenediaminetetraacetic acid; intrinsic reactivity; material selection; quality control; zero-valent iron
• Online Access: https://www.mdpi.com/2227-9717/7/10/652

There is a burgeoning interest in reliably characterizing the intrinsic reactivity of metallic iron materials (Fe⁰) or zero-valent iron materials (ZVI) used in the water treatment industry. The present work is a contribution to a science-based selection of Fe⁰ for water treatment. A total of eight (8) granular ZVI materials (ZVI1 to ZVI8) were tested. Fe⁰ dissolution in ethylenediaminetetraacetic acid (EDTA test) and 1,10-Phenanthroline (Phen test) is characterized in parallel experiments for up to 250 h (10 days). 50 mL of each solution and 0.1 g of each Fe⁰ material are equilibrated in quiescent batch experiments using 2 mM EDTA or Phen. Results indicated a far higher extent of iron dissolution in EDTA than in Phen under the experimental conditions. The tested materials could be grouped into three reactivity classes: (i) low (ZVI4, ZVI6, ZVI7, and ZVI8), (ii) moderate (ZVI1 and ZVI5) and (iii) high (ZVI2 and ZVI3). The order of reactivity was the same for both tests: ZVI2 ≅ ZVI3 > ZVI1 ≅ ZVI5 > ZVI4 ≅ ZVI6 ≅ ZVI7 ≅ ZVI8. Phen results revealed for the first time the time-dependent variation of the kinetics of iron corrosion (corrosion rate) in short-term batch experiments. Overall, the results demonstrated the superiority of the Phen test for evaluating the initial stage of Fe⁰ dissolution. Long-term column experiments are recommended to deepen the acquired knowledge.