Adsorptive Removal of Heavy Metals by Utilizing Activated Carbon Derived from Natural Bitumen

Heavy metals are recognized for their toxic properties, and their discharge into water resources poses significant harm to human health and the environment. This study aims to produce activated carbon from natural bitumen and evaluate its effectiveness in removing lead, chromium, cadmium, and copper ions from synthetic solutions. In this research, natural bitumen, found abundantly in the Kermanshah province and composed of inexpensive, accessible materials, was used as the raw material. Activated carbon was produced through chemical activation with phosphoric acid on these materials. Its specific surface area was determined using iodine number test, bulk hardness analysis, and BET analysis. The structural characteristics of the activated carbon were examined using Scanning Electron Microscopy equipped with EDS, FTIR, and XRD techniques. The effects of varying concentrations of lead (II), copper (II), cadmium (II), and chromium (III) ions (10 to 100 mg/L), pH (3 to 11), contact time (10 to 60 minutes), adsorbent dosage (0.1 to 0.5 gr), and temperature (25 to 60 ºC) on the adsorption process were investigated in a batch system. Metal concentrations were measured using Flame Atomic Absorption Spectroscopy. Results showed activated carbon samples with a specific surface area exceeding 303.55 m²/g and an iodine adsorption capacity of 707 mg/g were produced. The maximum metal ion removal efficiency was achieved under optimal conditions with a dosage of 0.4 g/L of adsorbent, a pH of 9, initial metal concentrations at 50 mg/L, and a contact time of 60 minutes. The order of adsorption capacity of activated carbon for the four heavy metal ions is Pb(II) > Cr(III) ~ Cu(II) > Cd(II). Additionally, desorption studies reveal that a 0.1 mol/L hydrochloric acid solution is the best washing solution for removing metal ions from activated carbon. Activated carbon can be reused multiple times in the adsorption-desorption process, demonstrating its potential as an efficient and economical adsorbent for heavy metal removal. Moreover, bitumen is a natural material that transforms activated carbon into a renewable source with excellent adsorption properties, thus making it highly effective in various applications.