Study on adsorption properties and mechanism of Pb²⁺ with different carbon based adsorbents

Different activated carbon materials are prepared from a series of solid wastes (sawdust, acrylic fabric, tire powder and rice husk) by combination of the KOH activation method and steam activation method. The influences of several parameters such as pH, contact time, adsorbent dosage and temperature on adsorption performance of Pb²⁺ with those different carbon adsorbents are investigated. The results demonstrate that C_{rice husk} performance well in the adsorption process. In the following, the C_{rice husk} is used to explain the adsorption mechanism of Pb²⁺ by SEM-EDS, FT-IR and XPS. The results illustrate that the surface oxygen-containing functional groups such as carboxyl, lactone group, phenolic hydroxyl and other alkaline metal ions like Na⁺ and K⁺ have significant effect on the adsorption process. A reasonable mechanism of Pb²⁺ adsorption is proposed that the ion exchange play key roles in the adsorption process. In addition, the effects of Cu²⁺, Zn²⁺ on the Pb²⁺ adsorption capacity with the four carbon adsorbents are also studied and the results demonstrate that other heavy metals play positive effects on the adsorption of Pb²⁺.