Arsenic removal from groundwater of the Chaco-Pampean Plain (Argentina) using natural geological materials as adsorbents

Abstract

Use of natural geological materials for arsenic (As) removal is an emerging solution at a household level for poor people in remote rural settlements, especially when the materials are locally available and can be collected by the local population. Their low or zero cost makes these materials very attractive compared with synthetic or commercial materials. Sometimes, this may be the only option to provide safe water to very poor settlements. Their suitability for As removal from water is mainly due to adsorption, co-precipitation and ion exchange processes involving Fe- and Al-rich minerals and clay minerals present in the soils or sediments. In the present study, various clay-rich soils from the Santiago del Estero province (SDE, NW Argentina) and, for comparison, a laterite from the Misiones province have been tested as adsorbents for As in shallow naturally contaminated groundwaters of the Río Dulce alluvial aquifer in SDE. Batch adsorption experiments showed higher As(V) removal for the Misiones laterite sample (99 %) as compared with the soils from SDE (40–53 %), which can be related to lower contents of water-soluble and oxalate extractable Al and Fe in the last samples. These results suggest the application of the Misiones laterite soil as an alternative for As removal. However, high transportation costs from Misiones to SDE can be an economical restriction for the low-income population of SDE.

Keywords:

• Groundwater arsenic removal
• geogenic arsenic sorbents
• sequential extraction

Acknowledgments

This study was carried out as a part of the Linnaeus-Palme Academic Exchange Programme between the Universidad Nacional de Santiago del Estero (UNSE) and the Department of Land and Water Resources Engineering, Royal Institute of Technology (KTH) through the grant 466-2003 from the International Programs Office (IPK), Stockholm, Sweden. MFM and AEF thank the IPK (Sweden) and the International Office of the KTH for the fellowship as Palme Exchange students in Sweden. PB and JB/MIL greatly appreciate the financial support provided by the Foundation for Strategic Environmental Research (MISTRA) through the grant 2005-035-137) and by the CYTED Network IBEROARSEN (grant 406RT0282) for finalizing the manuscript. JB and JSJ thank the National Science Council of Taiwan for the financial support. MIL thanks CNEA, CONICET and ANPCyT agencies in Argentina for support during various phases of the study. We also thank the laboratory help provided by Carl-Magnus Mörth at the Department of Geology and Geochemistry, Stockholm University for the chemical analyses.