Synthesis of Stabilized Iron Nanoparticles from Acid Mine Drainage and Rooibos Tea for Application as a Fenton-like Catalyst

Abstract

Intensive mining activities generate toxic acid mine drainage (AMD) effluents containing a high concentration of metals, including iron. The chemical synthesis of iron nanoparticles from this waste could lead to further environmental concerns. Therefore, the green synthesis of nanoparticles using plants has gained significant interest because of several benefits, including being eco-friendly. The current study reports a novel approach involving the synthesis of stabilized iron nanoparticles from AMD using rooibos tea extract. An aqueous solution of rooibos tea was prepared and titrated with AMD to reduce Fe 2+ /Fe 3+ . The samples synthesized under optimum conditions were characterized by TEM, XRD, FTIR, UV–Vis, and EDS. The results revealed that the nanoparticles had an average particle size of 36 nm with a spherical shape. These particles showed promising application as a Fenton-like catalyst for the degradation of textile dye (orange II sodium salt) with a removal efficiency of 94% within 30 min. Thus, the stabilized iron nanoparticles synthesized here performed in higher ranges than the currently reported Fenton-like catalysts regarding dye removal efficiency and reaction time.

Useful nanoparticles from mining waste and acid mine drainage

“…Another recent study proposed preparation of stabilized iron NPs from AMD applying rooibos tea extract as reagent used to reduce Fe 2+ /Fe 3+ to zero-valent Fe [45]. Ambient temperature (∼25 • C), a rooibos tea extract dosage of 5 g L −1 , a pH of 6, and 6 h of reaction time are found as optimal conditions.…”

Iron nanoparticles prepared from South African acid mine drainage for the treatment of methylene blue in wastewater

“…Their effectiveness in removing pollutants from wastewater is due to their high surface area and small particle size. However, the synthesis of iron nanoparticles is expensive since it requires the use of a chemical reductant (such as sodium borohydride), which has stringent environmental restriction policies (Kimpiab et al 2022 ; Böke et al 2023 ). In this line of investigation, polyphenols derived from plant extracts provide an environmentally friendly, cheap, and effective reductant for the synthesis of iron nanoparticles (Fazlzadeh et al 2017 ; Abdelfatah et al 2021 ).…”