Synthesis and Application of Titania Nanotubes and Hydrous Manganese Oxide in Heavy Metal Removal from Aqueous Solution: Characterization, Comparative Study, and Adsorption Kinetics

Abstract

Titania nanotube (TNT) and hydrous manganese oxide (HMO) nanoparticles were synthesized via hydrothermal synthesis and chemical coprecipitation methods, respectively, to investigate their performance in separation of Cd2+ and Cu2+. Furthermore, field emission scanning electron microscope, X-ray diffraction, and Fourier transform infrared spectroscopy analysis were used to examine the structural morphology, crystallinity, and composition of synthesized adsorbents and the calculated mean particle sizes of TNT and HMO nanoparticles were 26 and 7 nm, respectively, using the Scherrer equation. The applications of fabricated nanomaterials as an adsorbent for Cd2+ and Cu2+ decontamination were described via batch adsorption technique. The kinetic study of the adsorption process was performed at different initial concentrations of ions by two kinetic models: pseudo-first-order and pseudo-second-order models. Kinetic studies of the adsorption process revealed that the adsorption of Cd2+ and Cu2+ onto TNTs and HMOs is well described by pseudo-second-order kinetic model. According to the obtained equilibrium data for Cd2+ and Cu2+, the adsorption of metal ions was increased by increasing the initial concentrations of metal ions. It was further found that TNTs exhibited higher adsorption capacity for Cd2+ and Cu2+ than HMO nanoparticles so that at 200 mg/L of metal ion concentration, the maximum adsorption capacities of Cd2+ and Cu2+ were found as 49 and 47 mg/g, respectively, for sample TNT572 and 37 and 34 mg/g, respectively, for sample HMO1. However, the observed fast kinetics of adsorption revealed a high affinity between the heavy metal ions and the prepared nanostructured materials.