Removal of Pb(II) and Zn(II) from Aqueous Solution by Waste Petroleum Deposit and Application of Different Isotherm Models

Waste petroleum deposits (WPD), collected from the heat exchanger of naphtha hydrotreater unit were shown to be an effective, low-cost sorbent for the removal of Pb2+ and Zn2+ ions from aqueous solution. WPD were characterized by CHN, IR and ICP - Elemental analysis. Batch experiments were conducted to known the influence of various parameters of adsorption on the removal of Pb2+ and Zn2+, including adsorbent dose, pH, contact time as well as the metal concentration were separately investigated. Based on the obtained results, it has been found that the % of adsorption increase with an increase in pH to reach 95.3 and 97.9 % for Pb2+ and Zn2+ ions at pHs 4.6 and 6.1 respectively. The adsorption data was described by Langmuir, Freundlich, and BET adsorption isotherm model. The q(max) obtained from the three models for Pb2+ were 41.2, 21.6 and 339.96 mg/g respectively. While q(max) values for Zn2+ were 9.83, 2.8 and 3.35 mg/g by Langmuir, Freundlich and BET isotherm respectively. The regression coefficient (R-2) was 0.99 by Langmuir and BET isotherm in the case of Pb2+. While was 0.98 and 0.97 for Zn2+ respectively, which specifies that the type of adsorption of metal ions on WPD was chemo-sorption characterized by strong attractiveness. The test results indicate that WPD could be used as a low -cost adsorbent for the removal of Pb2+ and Zn2+ from aqueous solution.