NH2-MIL-125 (Ti)/biochar fibers for enhanced direct dyes adsorption

Abstract A novel adsorbent composite was synthesized by combining amino-functionalized MIL-125 (Ti) with carbonized wormwood (CW), and used to remove six direct dyes. The effect of carbon matrix type on the properties of the composites was investigated. The samples were characterized by chemical, morphological, thermal behavior, specific surface area, and pore diameter analysis. NH2-MIL-125 (Ti)/CW exhibits good crystallinity, high specific surface area, multi-pore size distribution, thermal stability and more active groups compared with carbonized cotton fiber and activated carbon as the matrix. Under optimal conditions, the adsorption process of NH2-MIL-125 (Ti)/CW on Direct Yellow R and Direct Dark Green NB is consistent with the Freundlich model and pseudo-second-order kinetic model. The adsorption capacity of NH2-MIL-125 (Ti)/CW is 255.0 and 296.7 mg/g, which is superior to 140.4 and 220.3 mg/g of NH2-MIL-125 (Ti), 58.9 and 97.8 mg/g of CW and other composite adsorption materials in a distilled water system. It is worth mentioning that NH2-MIL-125 (Ti)/CW can even achieve adsorption removal effects of 470.8 and 500.0 mg/g at pH= 2. This work may provide a theoretical reference for the application of biochar and metal-organic frameworks in the field of wastewater treatment.