RETRACTED ARTICLE: Adsorption kinetics and thermodynamics of Ni (II) by Pisha sandstone

The red Pisha sandstone was taken as absorbents to investigate the effects of the solution pH, the adsorption time and temperature adsorption onto Ni (II) absorption by the Pisha sandstone, and used dynamics and thermodynamic absorption models, coupled with microcalorimetry and infrared spectroscopic (FTIR) analysis, and scanning electron microscope-energy dispersive spectrometer (SEM-EDS); it aimed to determine the mechanism of thermodynamics and kinetics for Pisha sandstone absorbing Ni (II). The results indicated that the adsorption was performed at 293 K, pH 7, and the equilibrium was reached at 30 min, and the adsorption capacity of Ni (II) was 23.688 mg/g; the adsorption process of Ni (II) onto Pisha sandstone could be described with the Lagrangian pseudo-second-order kinetic model, the Freundlich model, and Dubinin-Radushkevich (D-R) model which all could well simulate the isothermal properties, indicating that the adsorption process was mainly monolayer with heterogeneous surface. According to the microthermal process and thermodynamic analysis, the thermodynamic parameters of Gibbs free energy change (ΔG), enthalpy change (ΔH), and entropy change (ΔS) were less than zero, showing that the adsorption of Ni (II) onto Pisha sandstone was exothermic, spontaneous, and entropy increasing. The absorptive models, FTIR analysis, and SEM-EDS demonstrated that the Pisha sandstones absorbing Ni (II) were mainly ion exchange and chemical adsorption meanwhile chemical precipitation little partly worked in the processes.