Determination of Heavy Metals in Waste Resin Powder by Wayeal Atomic Absorption Spectrophotometer

1.2 Reagents and Instruments

1.2.1 Lead Standard Solution(1000μg/ml)

1.2.2 Cadmium Standard Solution(1000μg/ml)

1.2.3 Chromium Standard Solution(1000μg/ml)

1.2.4 Ammonium Chloride: AR

1.2.5 Nitric Acid: GR

1.2.6 Hydrochloric Acid: GR

1.2.7 Hydrofluoric Acid: GR

1.2.8 Perchloric Acid: GR

1.2.9 30% Hydrogen Peroxide: GR

1.2.10 One in ten thousand analytical balances

1.2.11 Digital display electric hot plate

1.3 Pre-processing

1.3.1 Pre-processing of Lead and Cadmium Samples

Take 0.2g of sample (accurate to 0.1mg) into a 50ml PTFE crucible. After wetting with water, 5ml of hydrochloric acid was added and the sample was heated on a hot plate in a fume hood at about 120 ℃ to initially disintegrate the sample, and then removed and cooled slightly after evaporation until about 3m remained. Add 8ml of nitric acid, 8ml of hydrofluoric acid and 4ml of perchloric acid, cover and heat at about 160 ℃ on a hot plate for 3h. Open the lid, the electric heating plate temperature control at 180 ℃ to continue heating, and often shake the crucible. When heated to a thick white smoke, cover to fully decompose the black organic carbons. After the black organic matter on the crucible wall disappears, open the lid, drive away the white smoke and steam until the contents are viscous. Take down the crucible, slightly cold, add 0.2mL nitric acid to dissolve the soluble residue, after cooling, transfer the whole amount to 50ml volumetric flask, rinse the crucible lid and inner wall with appropriate amount of experimental water, the washing solution was incorporated into 50ml volumetric flask, and the fix the volume with experimental water, shaken well, and then left to be measure. If there are undissolved particles in the digested solution, filtering and centrifugation or natural precipitation are required. (Note: Do not allow a lot of bubbles to come out when heating, otherwise it will cause loss of the sample.)

1.3.2 Pre-processing of Chromium Sample

Take 0.2g (accurate to 0.0001g) of sample into a 50ml PTFE crucible. After wetting with water, 10ml of concentrated hydrochloric acid was added and the sample was heated on a hot plate in a fume hood at 50°C to initially decompose the sample. When evaporated to about 3ml, add 5ml of concentrated nitric acid, 5ml of hydrofluoric acid, cover and heat on the hot plate at about 120~130 ℃ for 0.5~1h, then open the lid, drive away the white smoke and steam until the contents are in the form of liquid beads in a non-flowing state (observe while hot). Depending on the condition of digestion, add 3ml of concentrated nitric acid, 3ml of hydrofluoric acid, 1ml of hydrogen peroxide, and repeat the above digestion process. Take down the crucible, slightly cold, add 0.2mL nitric acid to dissolve the soluble residue, transfer all the test solutions to a 50ml volumetric flask, add 5ml of 110% ammonium chloride solution, and fix the volume with experimental water, left to be measured. (Note: the total amount of 30% hydrogen peroxide added shall not exceed 10ml.)

2. Results and Discussion

Lead