Selective removal of iron(III), lead(II) and copper(II) ions by polar crude phytochemicals recovered from ten South African plants: identification of plant phytochemicals

Abstract

This work consists of gathering the leaves of ten different South African plants from the local reserve. Black and green tea were sourced commercially. The plants were air dried and polar crude material extracted using deionized water. These crude phytochemicals were used as green chelators to remove metal ions from an aqueous solution. Iron(III), lead(II) and copper(II) ions were competitively removed from an eight metal ion solution with iron(III) being removed at more than 80% followed by lead(II) with greater than 40% removal and copper(II) with removal values of more than 20%. Metal ion removal was shown to be affected by change in pH of the solution, indicating that removal took place via the pH-swing mechanism. As the pH is increased, iron(III) is first removed followed by lead(II) and then copper(II). Iron(III) and lead(II) were selectively removed even at a 10-fold dilution level compared to the other metal ions present. Loading tests showed that iron(III) removal does not change, but for lead(II) and copper(II) there is a noticeable increase in removal with an increase in the amount of crude. The phytochemicals in the crude were identified using Liquid chromatography-tandem mass spectrometry (LC-MS/MS). Some crudes had similar phytochemicals (quercetin) while others had unique compounds.

Statement of novelty It is the first time that crude polar phytochemicals from South African plants are used as green chelators. These green chelators selectively remove iron(III), lead(II) and copper(II) from a mix of eight different base metal ions. Iron(III) can be selectively removed at pH as low as 3.00 and, when iron(III) and lead(II) are 10 times more dilute compared to the other metal ions, iron(III) and lead(II) are still selectively removed. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is used to identify some of the phytochemicals present in these plants.

Keywords:

• Copper(II)
• flavonoids
• green chelators
• iron(III)
• lead(II)
• phenolics

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

We thank the NRF of South Africa, grant number [111701] and Stellenbosch University for financial support of this work.