Reductive degradation of carbon tetrachloride using tree leaf polyphenol–iron complexes for groundwater remediation†

Plant polyphenols, natural antioxidants, form complexes with iron minerals that enhance contaminant degradation via reductive processes. This study investigated the degradation of carbon tetrachloride (CT) using polyphenol–iron complexes synthesized from tree leaf extracts. Polyphenols were extracted from waste tree leaves, including Ficus microcarpa, Terminalia neotaliala, Haematoxylon campechianum, Ficus septica, Mangifera indica, and Ficus religiosa, with gallic acid identified as the predominant constituent. Among them, Terminalia neotaliala exhibited superior antioxidant capacity, reducing power, metal-chelating ability, and total phenolic content, making it the optimal choice for CT degradation experiments. Using the Taguchi method, optimal conditions for CT degradation were determined as pH 10, a leaf extract dose of 10 g L⁻¹, and an Fe²⁺ concentration of 15 mM, with pH as the most influential factor. Under these conditions, CT degradation reached 99% in aqueous solution and 89% in field groundwater within 24 h. Detected intermediates included trichloromethane, dichloromethane, and chloromethane, with chloride ions as the final mineralization product. This study underscores the potential of tree leaf polyphenols, in combination with Fe²⁺, as a sustainable approach for groundwater remediation.