Effect of inorganic salt ions on the adsorption of quinoline using coal powder

Abstract

Abstract In this study, coal powder was used as the adsorbent for quinoline. The effect of inorganic salt ions on the adsorption was explored, and the results suggest that the addition of inorganic salt ions can enhance both the removal rate and the amount of quinoline adsorbed. The removal rate and adsorbed amount of quinoline were 83.87% and 1.26 mg/g without inorganic salt ions. Under the same adsorption conditions, the removal rate and adsorbed amount of quinoline could reach 90.21% and 1.35 mg/g when Na+ was present in the solution, and 94.47% and 1.42 mg/g with the presence of Ca2+. In addition, the adsorption of quinoline using coal fitted the Freundlich isothermal adsorption model. Changes in the Gibbs free energy, entropy and heat of adsorption were all negative, indicating that the adsorption was spontaneous and exothermic. The changes in the absolute value of Gibbs free energy under both Na+ and Ca2+ were higher than that in the blank(without inorganic salt ions). The pseudo-second-order kinetic model was found to fit the adsorption kinetic data well, and the activation energy of adsorption under Na+ and Ca2+ were lower than that in the blank. These indicate that the addition of inorganic salt ions was beneficial to the adsorption process.