Synthesis of a novel perovskite-carbon aerogel hybrid adsorbent with multiple metal-Lewis active sites for the removal of dyes from water: experimental and DFT studies

Mixed perovskites have vast industrial potential, but some challenges (i.e., aggregation and chemical instability) limit their applications. Herein, a novel environment-friendly carbon aerogel (CAg) synthesized from sodium alginate (SA) was used as a precursor to create a double-B-site perovskite/carbon aerogel hybrid adsorbent ((Sr0.7Mn0.3Co0.5Fe0.5O3−δ)/CAg) (DB-perovskite/CAg hybrid). The adsorbent was extensively characterized via different techniques, including X-ray photoelectron spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The removal efficiency for crystal violet (CV) and acid yellow 17 (AY17) was conducted over various pH, adsorbent/adsorbate dosages, and reaction times in an aqueous system. The maximum adsorbed concentration (Qmax) recorded by 206 mg g−1 and 113 mg g−1 for CV and AY17, respectively, and compared to the performance of only DB-perovskite (114 mg g−1 and 59 mg g−1), respectively. The adsorption site energy distribution was studied by applying the density functional theory (DFT). The adsorption on the DB-perovskite/CAg hybrid was significantly regulated by pH change. The cooperative metal active/Lewis acid sites of the DB-perovskite/CAg adsorbent led to a faster and higher adsorption capacity toward CV and AY 17. The doping of Mn indicated a synergistic effect in improving the adsorption of either dye through the introduction of abundant active sites and strengthening of metal-functional groups (–C–O–C, –COOH, and C–OH/O–H)–π aromatic bonding, confirmed by DFT calculations.