PANI grafted onto waste poros polyurethane for co-adsorption of multiple pollutants in industrial wastewater

Abstract

Simultaneously up-taking multiple pollutants from industrial wastewater is an urgent challenge in the field of adsorption technology. In this study, a polyaniline (PANI)-based adsorbent supported by waste polyurethane (PU) was designed, and its capability for simultaneous adsorption of various pollutants was investigated. The results revealed that in a simulated multi-pollutant wastewater, the adsorbent demonstrated synchronous removal efficiencies of 88% for acid red G (ARG), 40% for methylene blue (MB), 90% for Cr(VI), 58% for phosphorus (TP), 42% for NH4+-N, 30% for NO3−-N, and 63% for chemical oxygen demand (COD). The corresponding adsorption capacities were 255.81, 22.57, 105.32, 10.04, 7.98, 23.03 and 236.31 mg/gP/T, respectively. The continuous flow column adsorption lasted for 1800 min (144 columns) before reaching saturation, and no significant decrease in adsorption efficiency was observed even after 5 cycles of regeneration. X-ray photoelectron spectroscopy (XPS) and excitation-emission matrix spectroscopy (EEM) analysis revealed that ARG, Cr(VI), NO3−-N, and TP competed for the same adsorption sites, with ARG exhibiting the highest affinity, followed by Cr(VI), TP, and NO3−-N. During the adsorption process, redox reactions occurred between Cr(VI) and =N- in the PANI chain, resulting in the formation of Cr(III) and -NH+- species, which further enhanced the adsorption of anionic pollutants such as H2PO4−. The interaction between pollutants before adsorption directly affected the subsequent adsorption process. Overall, these findings demonstrate the feasibility and effectiveness of the PU-P/T adsorbent as a potential engineering adsorbent for co-adsorption of a variety of pollutants.