Study on the Adsorption Characteristics of Calcareous Sand for Pb(II), Cu(II) and Cd(II) in Aqueous Solution

Abstract

The adsorption characteristics of calcareous sand for heavy metals Pb(II), Cu(II) and Cd(II) have been studied by batch testing in this study. The influence of the solid–liquid ratio, initial pH0 value, ionic strength, reaction time, temperature and initial concentration on adsorption has been investigated. Test results indicate that the initial pH and the solid–liquid ratio have a significant influence on the removal efficiency. At T = 30 °C, r = 1.0 g/L, and C0 = 1000 mg/L and for 12 h of reaction, the removal efficiencies of Pb(II), Cu(II) and Cd(II) are 97.6%, 88.15% and 65.72%, respectively. The adsorption quantity is more than 80% of the maximum adsorption quantity within 60 min, and the equilibrium adsorption can be reached within 120 min. The pseudo-second-order kinetic model is suitable to simulate the dynamic adsorption process of calcareous sand, and the isothermal process is found to obey the Langmuir model. Calcareous sand has a very high adsorption capacity for Pb(II), Cu(II) and Cd(II), with a maximum adsorption quantity Qm reached 1052.95 mg/g, 1329.84 mg/g and 1050.56 mg/g, respectively. Thermodynamic test results indicate that the adsorption process is spontaneously exothermic and that low temperature is favorable to the adsorption reaction.