Low-cost technologies based on heterogeneous photocatalysis and zerovalent iron for arsenic removal in the Chacopampean plain, Argentina

MARÍA E. MORGADA DE BOGGIO; IVANA K. LEVY; MIGUEL MATEU; J.M. MEICHTRY; GERARDO D. LÓPEZ; D. BAHNEMANN; R. DILLERT; P. BHATTACHARYA; J. BUNDSCHUH; MARTA I. LITTER

Hannover, Alemania

Simposio; - International Symposium Coupling Sustainable Sanitation & Groundwater Protection; 2008

         The Chacopampean Plain in Argentina constitutes one of the most extended areas in the world with very high arsenic concentrations in groundwater, amply surpassing the standard requirements for drinking water (Argentine and WHO limit 10 µg L-1). The situation is more serious in rural areas, where low water quality, poverty and malnutrition cause a high incidence of HACRE (Chronic Endemic Regional Hydroarsenicism, Hidroarsenicismo Crónico Regional Endémico in Spanish). In this work, results of application of simple and low-cost technologies based on heterogeneous photocatalysis (HP) and zerovalent ion (ZVI) to remove As (III, V or both) from groundwater are presented. HP is an advanced oxidation technology that uses semiconductors such as TiO2 for water detoxification. Under UV irradiation (e.g. solar light), active oxidizing species are formed, able to transform organic and inorganic pollutants in less harmful compounds. For HP tests, PET bottles covered internally with a TiO2 layer were exposed to solar or artificial UV light. Arsenic-containing synthetic waters (around 1 mg L-1), irradiated 6 h under artificial light, followed by the addition of iron packing wire, yielded 86% of As removal. Real well waters with As concentrations from 900 to 1800 mg L-1 (Santiago del Estero, NW Argentina) under solar light irradiation, with further addition of a ferric salt, yielded 95% As removal. The zerovalent iron technology (ZVI) has been extensively applied to remediation of contaminants, especially toxic metallic pollutants. The primary advantages of ZVI include low cost, simplicity in handling and scalability. Different iron materials such as packing wire, iron powder and iron nanoparticles have been tested. Arsenic removal using iron nanoparticles was found to be much more efficient than the other materials, due to the higher contact area between phases. For ZVI tests, water was introduced in plastic bottles with iron packing wire, iron wool or iron nanoparticles (NanoFe®) and were kept in the dark or irradiated under artificial UV or solar light. An enhancement of As removal was observed under UV light in synthetic samples, especially at low Fe concentrations. This enhancement was even higher in samples containing humic acids and in real well waters of the Tucumán Province (NW Argentina).