Investigation into the thermodynamics and kinetics of the binding of Cu2+ and Pb2+ to TiS2 nanoparticles synthesized using a solvothermal process

Abstract

In the present study, titanium (IV) sulfide (TiS₂) was synthesized and investigated for the removal of Cu²⁺ and Pb²⁺ ions from aqueous solutions. TiS₂ nanoparticles synthesized through a solvothermal synthesis were characterized using x-ray diffraction (XRD) and scanning electron microscopy (SEM). The average particle size for the TiS₂ material was determined to be 8.03 ± 0.98 nm from the diffraction pattern. Studies were performed to examine the effects of pH, temperature, time, and interfering ions on the binding of Cu²⁺ and Pb²⁺ to the TiS₂. As well isotherm studies were performed to determine the binding capacity of TiS₂ for both Cu²⁺ and Pb²⁺ ions. The pH profile studies showed optimal binding occurred at pH 2 for the sorption of both Cu²⁺ and Pb²⁺ to the TiS₂. The isotherm studies showed the adsorption capacities at temperatures of 4, 22, and 45°C for Cu²⁺ were 243, 222, and 153 mg/g, respectively. An opposite trend in the adsorption was observed for Pb²⁺ binding to the TiS₂. The observed binding capacities for Pb²⁺ were 32, 166, and 357 mg/g, at temperatures of 4, 22, and 45°C, respectively. The thermodynamic parameters for binding showed a non-spontaneous process for the sorption of Cu²⁺ whereas a spontaneous binding process was observed for the sorption of Pb²⁺. Additionally, the binding of Cu²⁺ on TiS₂ in the presence of interfering ions (Na⁺, K⁺, Mg²⁺, and/or Ca²⁺) was observed to decrease at high concentrations; however, the binding of Pb²⁺ was unaffected by the presence of the same cations.

Keywords: Copper sorption; Isotherms; Kinetics; Lead sorption; TiS2.