Adsorption and Thermal Stabilization of Pb2+ and Cu2+ by Zeolite

In recent years, zeolite has been proven to be a cost-effective adsorbent for treating wastewater containing heavy metal ions. However, few studies have investigated the subsequent treatment of metal-laden zeolites after adsorption, which may become a source of secondary pollution if not properly dealt with. To fill the knowledge gap. the adsorption behavior of Pb2+ and Cu2+ on zeolite was examined in the present study. The adsorption process was fast and reached equilibrium within 60 min, with adsorption data fitted better with the Langmuir equation than the Freundlich equation. After thermal treatment for metal-adsorbed zeolites, X-ray diffraction results showed that Pb2+ and Cu2+ adsorbed on zeolites can be readily stabilized into PbAl2Si2O8 and CuAl2O4, and the best temperatures for formation of PbAl2Si2O8 and CuAl2O4 were 950 and 1000 degrees C, respectively. Finally, a prolonged leaching test (at pH 2.9 for 22 d) demonstrated that the Pb2+ and Cu2+ concentrations in the leachate of calcined samples were approximately 2 orders of magnitude lower than those of untreated samples, validating the high stability of treated zeolites. All these findings pointed to the potential for use of zeolites as a promising and sustainable strategy to treat and stabilize Pb2+ and Cu2+ in wastewater.