title: Removal of arsenic and cadmium with sequential soil washing techniques using Na2EDTA, oxalic and phosphoric acid: Optimization conditions, removal effectiveness and ecological risks.
abstract: Testing of sequential soil washing in triplicate using typical chelating agent (Na2EDTA), organic acid (oxalic acid) and inorganic weak acid (phosphoric acid) was conducted to remediate soil contaminated by heavy metals close to a mining area. The aim of the testing was to improve removal efficiency and reduce mobility of heavy metals. The sequential extraction procedure and further speciation analysis of heavy metals demonstrated that the primary components of arsenic and cadmium in the soil were residual As (O-As) and exchangeable fraction, which accounted for 60% and 70% of total arsenic and cadmium, respectively. It was determined that soil washing agents and their washing order were critical to removal efficiencies of metal fractions, metal bioavailability and potential mobility due to different levels of dissolution of residual fractions and inter-transformation of metal fractions. The optimal soil washing option for arsenic and cadmium was identified as phosphoric-oxalic acid-Na2EDTA sequence (POE) based on the high removal efficiency (41.9% for arsenic and 89.6% for cadmium) and the minimal harmful effects of the mobility and bioavailability of the remaining heavy metals.
authors.affiliation: Key Laboratory for Water and Sediment Sciences of Ministry of Education, School of Environment, Beijing Normal University, Beijing 100875, China.
authors.forename: Meng
authors.initials: M
authors.lastname: Wei
authors.affiliation: Key Laboratory for Water and Sediment Sciences of Ministry of Education, School of Environment, Beijing Normal University, Beijing 100875, China. Electronic address: jeffchen@bnu.edu.cn.
authors.forename: Jiajun
authors.initials: J
authors.lastname: Chen
authors.affiliation: Key Laboratory for Water and Sediment Sciences of Ministry of Education, School of Environment, Beijing Normal University, Beijing 100875, China.
authors.forename: Xingwei
authors.initials: X
authors.lastname: Wang
mesh_terms: D001151:Arsenic / Q000032:analysis / Q000302:isolation & purification*; D002104:Cadmium / Q000032:analysis / Q000302:isolation & purification*; D002614:Chelating Agents / Q000737:chemistry; D004463:Ecology; D004492:Edetic Acid / Q000737:chemistry*; D006801:Humans; D010070:Oxalates / Q000737:chemistry*; D010756:Phosphoric Acids / Q000737:chemistry*; D018570:Risk Assessment; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000032:analysis / Q000302:isolation & purification*
chemical_list: D002614:Chelating Agents; D010070:Oxalates; D010756:Phosphoric Acids; D012987:Soil; D012989:Soil Pollutants; D002104:Cadmium; D004492:Edetic Acid; C030242:phosphoric acid; D001151:Arsenic
keywords: Arsenic; Cadmium; Indices of metal bioavailability; Indices of metal mobility; Sequential soil washing