Speciation of As(III) and As(V) in some Ghanaian gold tailings by a simple distillation method

Abstract

As(III) and As(V) in goldtailings and river-bed sediments from Obuasi were determined by distillation of arsenic as AsCl3. Results yielded 3750±426 mg kg-1 (45.2%) for As(V) and 3050±66 mg kg-1 (36.7%) for As(III) in the tailings. In the river-bed sediments, one spot yielded: As(III) 0 mg kg-1 (0%) and As(V) 1447±51 mg kg-1 (100%), whilst a second spot yielded: As(III) 0 mg kg-1 (0%) and As(V) 2976±51 mg kg-1 (100%). Using arsenic oxide standards, the recovery of As(III) and As(V) in the trioxide were 94.8 and 0.6% respectively. In a mixture of the two oxides, the recovery of As(III) was 87.6% with practically no interference from As(V). Total As content of the tailings was determined by neutron activation analysis (NAA) to be 8305±75 mg kg-1.As(III) and As(V) in gold tailings and river-bed sediments from Obuasi were determined by distillation of arsenic as AsCl3. Results yielded 3750±426 mg kg-1 (45.2%) for As(V) and 3050±66 mg kg-1 (36.7%) for As(III) in the tailings. In the river-bed sediments, one spot yielded: As(III) 0 mg kg-1 (0%) and As(V) 1447±51 mg kg-1 (100%), whilst a second spot yielded: As(III) 0 mg kg-1 (0%) and As(V) 2976±51 mg kg-1 (100%). Using arsenic oxide standards, the recovery of As(III) and As(V) in the trioxide were 94.8 and 0.6% respectively. In a mixture of the two oxides, the recovery of As(III) was 87.6% with practically no interference from As(V). Total As content of the tailings was determined by neutron activation analysis (NAA) to be 8305±75 mg kg-1.A simple distillation method based on the volatility of AsCl3 was used to examine the speciation of trivalent and pentavalent arsenic in mine tailings and river sediments at Obuasi, Ghana. Results showed that the sum of As(III) and As(V) concentrations in the tailings differed by 1495 mg/kg from the total As concentration of 8305 mg/kg. No As(III) was found in river-bed sediments because all As(III) had been converted to As(V).