University of Kentucky
A Method for Arsenic Removal Using a Chelatine Water Insoluble Thiol
Institution
University of Kentucky
Faculty Advisor/ Mentor
David Atwood
Abstract
Research at the University of Kentucky has revealed that a series of water-insoluble thiolates can be dispersed in a column containing either silica or activated carbon to remove both arsenite and arsenate under a variety of conditions. The system was tested with water containing 300 ppb arsenic and the resulting samples after filtration had less than 1ppb arsenic. The filtration system may be assembled using PVC tubing and plastic hoses and the actual arsenic binding media is created from inexpensive proprietary thiol compounds. An example of one such compound is benzenediethanethiol (BDT) for which a great deal of information is known. BDT is a University of Kentucky-patented class of compounds that has been shown to irreversibly bind Hg under a wide range of laboratory conditions1,3,4 as well is in the field for gold mining effluent (Matlock et al. (2002) acid mine drainage, and for soil-borne mercury. The BDT- Hg precipitates that result show no leaching under both basic and acidic conditions. Mercury and Arsenic are "soft" elements and form strong bonds to sulfur. In fact, the bonding of arsenic to sulfur (~370kJ/mol) greatly exceeds the bonding to mercury (~ 200kJ/mol). Thus, it was anticipated that BDT would bind arsenic in a manner similar to mercury as demonstrated in the previously cited publications. This was found to be the case; BDT binds arsenic and removes the element from water and with no subsequent leaching. It should be noted that the formation of As-S bonds is partially responsible for the toxicity of the element in living systems.
A Method for Arsenic Removal Using a Chelatine Water Insoluble Thiol
Research at the University of Kentucky has revealed that a series of water-insoluble thiolates can be dispersed in a column containing either silica or activated carbon to remove both arsenite and arsenate under a variety of conditions. The system was tested with water containing 300 ppb arsenic and the resulting samples after filtration had less than 1ppb arsenic. The filtration system may be assembled using PVC tubing and plastic hoses and the actual arsenic binding media is created from inexpensive proprietary thiol compounds. An example of one such compound is benzenediethanethiol (BDT) for which a great deal of information is known. BDT is a University of Kentucky-patented class of compounds that has been shown to irreversibly bind Hg under a wide range of laboratory conditions1,3,4 as well is in the field for gold mining effluent (Matlock et al. (2002) acid mine drainage, and for soil-borne mercury. The BDT- Hg precipitates that result show no leaching under both basic and acidic conditions. Mercury and Arsenic are "soft" elements and form strong bonds to sulfur. In fact, the bonding of arsenic to sulfur (~370kJ/mol) greatly exceeds the bonding to mercury (~ 200kJ/mol). Thus, it was anticipated that BDT would bind arsenic in a manner similar to mercury as demonstrated in the previously cited publications. This was found to be the case; BDT binds arsenic and removes the element from water and with no subsequent leaching. It should be noted that the formation of As-S bonds is partially responsible for the toxicity of the element in living systems.