Ternary metal oxide embedded carbon derived from metal organic frameworks for adsorption of methylene blue and acid red 73

Abstract

Organic dyes can enter water bodies through industrial wastes and may pose a threat to the health of aquatic organisms and human. Metal organic framework derived carbon materials (CMOFs) have shown excellent performance for aqueous dye adsorption. However, few have studied multimetallic CMOFs for dye removal. Herein, a ternary metal oxide embedded carbon derived from amino-modified metal organic framework (CMOF(Fe/Al/Ni 8/7/5)-NH2) has been developed as an efficient adsorbent to remove aqueous methylene blue (MB) and acid red 73 (AR-73). CMOF(Fe/Al/Ni 8/7/5)-NH2 reached adsorption equilibrium for both MB and AR-73 within 30 min at neutral pH condition. It also achieved 18 and 24 times higher adsorption than commercial activated carbon (AC) in 10 min for MB and AR-73, respectively. Compared to other CMOFs-NH2, CMOF(Fe/Al/Ni 8/7/5)-NH2 had the highest adsorption capacity for both cationic MB and anionic AR-73. In addition, CMOF(Fe/Al/Ni 8/7/5)-NH2 had < 0.15% metal leaching in 90 min in the pH range of 4–10, and it also maintained 89% and 95% adsorption capacity for MB and AR-73 in five consecutive adsorption batches, respectively. Electrostatic interaction was identified as the primary interaction between CMOFs-NH2 and the dyes, and the embedded crystalline metal oxides with different points of zero charge (PZCs) were identified to be the key adsorption sites. A uniformly distributed surface charge model was proposed to explain the exceptional adsorption capacity of CMOF(Fe/Al/Ni 8/7/5)-NH2. With fast kinetics, high adsorption capacity, wide applicability and good stability, CMOF(Fe/Al/Ni 8/7/5)-NH2 may be an effective adsorbent for many other ionic organic pollutants.