Undiminished performance in simultaneous phosphorus and dye recovery via ring-opening Mg-assembled carbonitride

Abstract

The multiple effects of eutrophication and refractory organic dye may pose serious environmental risks, whereas conventional adsorbents mostly suffer from the disadvantage of performance degradation in complex environments. Herein, we designed Mg-assembled carbonitride (MAC) that allowed for phosphorus (P) and selective dye recovery (methylene blue (MB) as model pollutants) simultaneously, and then successfully separated the two pollutants in a simple way to obtain pure dyes and phosphorus-containing compounds. The triazine ring conjugation framework and abundant functional groups of carbonitride facilitated the doping of Mg sites. The adsorption capacity of MAC for P (211.6 ± 2 vs 207.4 mg P·g−1) and MB (116.5 ± 3 vs 117.8 mg MB·g−1) in the binary-polluted system exhibited little difference from the individual, implying synchronous and undiminished adsorption on MAC. This was attributed to the ring-opening reaction triggered by NaOH etching and thermal decomposition, generating the two new active sites, where cyano groups (C N) interacted with P and Mg–N bonds responded with both target pollutants. Moreover, the favorable selective adsorption ability of MAC for different dyes was attributed to electrostatic attraction, surface complexation, hydrogen bonds and π-π interactions. This study provides a good reference for exploiting performance-stable multifunctional adsorbents for applications in wastewater resource recovery.