Leaching of toxic metals from face mask samples was conducted as per EPA Method 1311 (Usepa, 1995 ). Briefly, a mixture comprising diluted nitric acid (HNO3) (ratio of water: HNO3 = 9:1 (v/v) (pH 4), sodium hydroxide (NaOH) (pH 10), and deionized water were added to the Erlenmeyer flasks containing the face masks and made up to a final volume of 250 mL. The pH of the mixture was adjusted using a pH meter pH 700 of Eutech Instruments (United Kingdom). The samples were magnetically stirred at room temperature for one day before the leachate was collected.
Another sample was prepared by replacing the face mask with only the nose metal wire. The metal wires were extracted from the face masks using scissors and cutters. Then, a diluted HNO3 (0.1 N) and NaOH were prepared in a 50 mL volumetric flask for the leaching solution. Then, leaching solutions at pH 4 and pH 10 were prepared by the dropwise addition of 0.1 N diluted HNO3 and NaOH into the deionized water (DW; 450 mL), and the pH was adjusted using a pH meter. An aliquot of each leaching solution (20 mL) and the sample was transferred into 100 mL Erlenmeyer flasks containing acidic (pH 4.0), neutral (pH 7.0) and alkaline (pH 10) solutions, respectively. The samples were left to magnetically stir at room temperature for one day.
Another sample was prepared by replacing the face mask with only the nose metal wire. The metal wires were extracted from the face masks using scissors and cutters. Then, a diluted HNO3 (0.1 N) and NaOH were prepared in a 50 mL volumetric flask for the leaching solution. Then, leaching solutions at pH 4 and pH 10 were prepared by the dropwise addition of 0.1 N diluted HNO3 and NaOH into the deionized water (DW; 450 mL), and the pH was adjusted using a pH meter. An aliquot of each leaching solution (20 mL) and the sample was transferred into 100 mL Erlenmeyer flasks containing acidic (pH 4.0), neutral (pH 7.0) and alkaline (pH 10) solutions, respectively. The samples were left to magnetically stir at room temperature for one day.