Activated carbons for the removal of organic micropollutants from groundwater

According to US-EPA (United States-Environmental Protection Agency) adsorption on Granular Activated Carbons (GAC) constitute the best available Technology for the removal of Volatile Organic Compounds (VOC), Natural Organic Matter (NOM) and pesticides from drinking water. In this presentation, we compare the adsorption capacity of two commercially available GACs: a coal-based carbon (GAC-M; Cecarbon Gac 1240, Arkema) and a coconut-shell carbon (GAC-V; Acticarbone NCL 1240, Arkema). The study was conducted on real samples from the Integrated Water System of the City of Milano. Considering the variability of the groundwater contamination, a preliminarily statistical analysis of the monitoring data was carried out to identify water-treatment plants that are characterized by a specific contamination profile and that can be considered as representative of Milano groundwater pollution as a whole. Five water treatment plants were identified and thus studied. A standard methodology for the determination of adsorption capacity of the activated carbons by a micro-isotherm technique for adsorbates at ppb concentrations was used (ASTM D5919-96). 5 carbon concentrations were studied: 1, 8, 12, 20 and 30 mg/L for GAC-M and 1, 3, 5, 8 and 12 mg/L for GAC-V. Isotherm data were collected from experimental samples. 53 analytes were determined using EPA Methods for VOCs (524.3 version 1.0, 2009; 5030C version 3.0, 2003) and APAT-IRSA method for pesticides (5060, 2003). In addition, chemico-physical characterization of the two GC types were performed, to correlate specific surface and porosity volume to adsorption properties. The coconut-shell carbon presents better adsorption performances towards all the tested pollutants and adsorption capacity that is greater even in adverse conditions. For these reasons it can be considered the most suitable adsorbent.