Investigation and evaluation of organic acid on metal recovery from waste printed circuit of lap top computer

The samples, consisting of used laptop computers, were sourced from selected schools and offices in Emene, Enugu State, Nigeria. Metal components were removed from the printed circuit boards using a hot air gun. The detached metals were then reduced to small sizes using sharp-edged pliers and a hammer.

After size reduction, the metals were washed with distilled water and allowed to drain. They were subsequently dried at 30°C in a laboratory hot air oven. The detached metal parts were then immersed and stirred in 1 M sodium hydroxide solution with mild agitation (100 rpm) at 60°C for 4 hours.

The samples (metal parts) were washed properly with distilled water and dried at 30°C in a laboratory hot air oven. They were then crushed to a powdered form with a particle size of 75 µm using a laboratory jaw crusher.

The dried sample was characterized using SEM-EDX and XRD. Metal ions present in significant concentrations were selected for further extraction and recovery.

Leaching experiments were carried out in a 250 mL Erlenmeyer glass reactor equipped with a thermometer to control the temperature. The reactor was placed on a hot plate stirrer to heat the solution. A measured amount of the sample (1 g) and 10 mL of the leaching reagent solution were added to the reactor vessel. The mixture was allowed to reach thermal equilibrium, with agitation provided by a magnetic stirrer at 500 rpm for the entire duration of the leaching time.

During the leaching experiments, citric acid and malic acid solutions with known concentrations (1 M, 2 M, 3 M, 4 M, and 5 M) were prepared. A 10 mL aliquot of each solution was measured into an Erlenmeyer glass reactor. The leaching time (2 h, 3 h, 4 h, 5 h, and 6 h) and temperature (30°C, 40°C, 50°C, 60°C, and 70°C) were varied.

A constant pulp density of 25 g/L was used. The leaching operation conditions were standardized to facilitate a comparison of the leaching efficiency of each leaching reagent.

After the leaching process, the leach liquor was analyzed using Atomic Absorption Spectroscopy (AAS) to determine the total amount of metals present.