Reductive degradation of carbon tetrachloride with guava leaf extract

Abstract

Guava leaves contain polyphenols, which exhibit antioxidant activities and act as electron suppliers. It was postulated that guava leaf extract (GLE) may have the potential to be used as a natural reducing agent for in situ chemical reduction of chlorinated solvents, such as carbon tetrachloride (CT). Extraction of GLE was conducted by boiling guava leaves, and filtering the liquid to produce GLE-Filtrate. GLE-Powder was produced by drying the GLE-Filtrate at 50 °C. Characterization analysis showed a yield of 16.6 g GLE-Powder/100 g of leaves, with a total polyphenolic content of 300 mg g−1, and with gallocatechin as a major constituent. Both GLE-Powder and GLE-Filtrate exhibited the capability to degrade CT in aqueous phase. The CT degradation rate increased with increasing alkaline conditions, at pH higher than the pKa of polyphenols. GLE-Filtrate reductive degradation of CT can be enhanced with the presence of iron salts, and various minerals, or soils containing iron, at pH 10. The specific surface area rate constant (kSA) of CT degradation for the GLE-Filtrate/Fe2O3 aqueous system was as high as 5.52 × 10−3 L d−1 m−2. The analysis of byproducts formation found trichloromethane to be a major intermediate, which was further mineralized to generate Cl−.