Synthetic zeolite from coal bottom ash and its application in cadmium and nickel removal from acidic wastewater

Abstract

The adsorption properties of synthetic zeolite from coal bottom ash (CBA) were investigated for Cd and Ni removal from simulated acidic wastewater. The results showed that alkaline fusion synthetic zeolite significantly increased the specific surface area, pore volume, and cation exchange capacity (CEC) compared with CBA. The effects of various experimental parameters such as coexisting ion competition, pH, contact time, and temperature on the adsorption capacity and adsorption mechanism were investigated. Compared with single-metal ion adsorption, the adsorption capacity for Cd or Ni decreased in multiple-metal ions adsorption due to the competition effect of coexisting ion. Adsorption efficiency increased with increasing pH and the equilibrium was achieved at around 5.5 (>pHpzc 4.5). The adsorption equilibrium was achieved within 4 h and followed the pseudo-second-order kinetic model. The result concluded that ion exchange was the primary adsorption mechanism. Moreover, zeolite exhibited strong neutralizing capacity, which could be attractive for acidic wastewater treatment.