Comparison of Three Methods of Digestion for Trace Metal Analysis in Surface Dust Collected from an EwasteRecycling Site

The recycling of e-waste materials potentially contaminates the environment with heavy metals. Analysing the exact contents of heavy metal in e-waste products is germane for the routine monitoring, risk assessment and regulation of the environment. Therefore, the efficiency of three methods of digestion was evaluated for Cd, Fe, Pb, Cr and Zn by AAS in surface dust from an e-waste recycling site and to recommend the most efficient digestion method. The digestion methods were aqua regia, dry ashing followed by aqua regia and nitric acid digestion followed by extraction with HCl. Analysis of variance, Student’s t-test and F-test were performed separately for the indoor, outdoor and control dust samples analytical result. Analytical results indicated that the nitric acid digestion followed by extraction with HCl was the most efficient in recovering Pb and Fe based on recovery efficiency. Aqua regia was found to be an alternative method for recovering Pb and Fe based on cost and time effectiveness. Aqua regia was the most efficient in recovering Zn while aqua regia and nitric acid digestion followed by extraction with HCl were satisfactory for the recovery of Cd. Dry ashing followed by aqua regia was found unsuitable for the analysis of these metals in the samples because it recovers relatively little heavy metals and more analysis time.