In situ fabrication of dynamic nano zero-valent iron/activated carbon nanotubes membranes for tellurium separation

Recovery of valuable elements from (industrial process) photovoltaic wastes would be beneficial for both economical and sustainability reasons. In this work, nano zero-valent iron/activated carbon nanotubes (NZVI/ACNTs) hybrid membranes were fabricated by using NZVI as dynamic layer and CNTs as substrate for deep tellurium extraction, where the NZVI particles were formed by in situ reduction. Batch experiments were conducted to investigate the adsorption properties of NZVI/ACNTs hybrid membranes under different solution conditions such as pH, temperature, sorbent dosage, and competitive ions. Energy dispersive X-ray and X-ray photoelectron spectroscopy results confirmed good adsorption capacity of tellurium by NZVI/ACNTs through redox reactions. The tellurium adsorption capacities decreased in the presence of competitive ions and as the concentration of NO3 significantly increased, the adsorption quantity dropped from 331.6 to 286.5 mg/g. Extraction of tellurium under weakly acidic conditions had a positive effect and reached a maximum adsorption capacity about 800 mg/g at pH 4.7. Kinetic models and equilibrium isotherms fitted well to the adsorption experimental data indicating that chemical adsorption dominate during the adsorption process of NZVI/ACNTs-Te. As a reusable and high-efficient adsorbent, NZVI/ACNTs membrane has tremendous potential to handle and recycle toxic tellurium containing compounds. (C) 2019 Elsevier Ltd. All rights reserved.