Synthesis of NaAlSiO4 Hollow Microspheres as Absorbents for the Removal of Heavy Metal ions in Environmental Remediation

Abstract

Abstract The harm of heavy metal ions to the environment has attracted increasing attention. Adsorption has been proven to be one of the best choices for controlling water pollution. Hollow microspheres with a high surface area and large internal space have been considered ideal adsorbents. In this work, NaAlSiO4 hollow microspheres were synthesized through a solvothermal method combined with calcination treatment. The removal ability of the hollow microspheres to heavy metal ions was evaluated using Ni(II) and Cd(II) as the models under different conditions, including different pH values, metal ion concentrations, and adsorption times. SEM and TEM images show that the average diameter of the hollow microspheres was approximately 2 ± 0.5 µm, and the average pore size was approximately 20 ~ 60 nm. The peak near 707°C in the DSC curve indicates the crystal transformation from an amorphous state to a well-crystallized state, and well-crystallized NaAlSiO4 microspheres can be obtained after calcination at 850℃. The maximum adsorption capacity of the hollow microspheres was 115.15 ± 1.68 mg·g− 1 for Ni(II) and 106.03 ± 0.97 mg·g− 1 for Cd(II). The adsorption of the NaAlSiO4 hollow microspheres depends on the surface area and content of CTAB for Ni(II) and Cd(II), respectively. The Ni(II) adsorption efficiency of the NaAlSiO4 hollow microspheres was still more than 95% after 4 cycles. This study provides an effective absorbent for removing heavy metal ions in wastewater treatment and environmental remediation.