ADSORPTION CHARACTERISTICS OF ARSENIC(III) AND ARSENIC(V) ON IRON(III)-LOADED CHELATING RESIN HAVING LYSINE-N-ALPHA,N-ALPHA-DIACETIC ACID MOIETY

An iron(III)-loaded chelating resin (Fe-LDA) with lysine-N-alpha,N-alp ha-diacetic acid functional groups has been prepared and its adsorptio n characteristics for arsenic(III) and arsenic(V) have been examined. Arsenic(V) was strongly adsorbed to the resin in the pH ranee from 2 t o 4, while arsenic(III) was moderately adsorbed between pH 8 and 10. T he isotherm data for arsenic(V) at pH 3.5 fitted well to a Langmuir eq uation with a very large binding constant of 7.2 x 10(4) dm(3) mol(-1) and a capacity constant of 0.74 mmol g(-1). The data for arsenic(III) at pH 9 also fitted to a Langmuir equation, with a binding constant o f 190 dm(3) mol(-1) and a capacity constant of 0.84 mmol g-(1). Regene ration of the resin was successfully carried out with 0.1 mol dm(-3) s odium hydroxide solution. Both arsenic compounds can be almost quantit atively recovered from the resin under these conditions. Only a small amount of ferric ions (less than 0.1%) was observed to come off the re sin during the regeneration with alkaline solutions. Since the Fe-LDA resin showed little affinity for arsenic(III) in acidic media, the pre sent adsorption system can provide satisfactory separation of arsenic( V) from arsenic(III). Arsenic(V) was successfully concentrated in the column packed with Fe-LDA resin from its dilute solution.