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Extraction of arsenic from soils contaminated with wood preservation chemicals PDF Print E-mail
Three chromated zinc arsenate (CZA)/chromated copper arsenate (CCA) contaminated soils were investigated in a laboratory scale to study As mobilisation and to identify a chemical agent that could be used in soil washing to extract arsenic. Arsenic is strongly bound to CZA/CCA soils; only ~50% of the tot-As was removed from water washed soils.

High Fe or Al mobilisation is not necessarily indicative of high As removal from CZA/CCA soils. A high Cu/As-ratio and a large amount of soluble Ca in the soil hampered As extraction. The high ratio can be an indication of stable Cu-arsenates in soil. Calcium can react with the extraction agent or with As during extraction. Besides high As extraction, the cost, occupational health issues and technical aspects were considered when selecting the chemical. Sodium hydroxide, dithionite with citrate (and oxalate) (dithionite solutions) and oxalate with citrate were the most efficient chemicals for removing As from the soils. The disadvantages of using these strong chemicals are: a high cost (oxalate with citrate); damage to equipment (dithionite solutions); an adverse impact on occupational health (dithionite solutions); or a deterioration in soil quality after extraction (NaOH and dithionite solutons). Phosphate, solutions based on NH2OH•HCl or citrate were not efficient in mobilising As from the soils.  Authors: Lea Rastas Amofah1,*, Christian Maurice1 and Prosun Bhattacharya2 1 Div. of Architecture and Infrastructure, Dept. of Civil, Mining and Environmental Engineering, Luleå University of Technology, 971 87 Luleå, Sweden 2 KTH-International Groundwater Arsenic Research Group, Department of Land and Water Resources Engineering, Royal Institute of Technology (KTH), SE-100 44 Stockholm, Sweden. Published in: Soil and Sediment Contamination, 19:142-159, 2010