Cutting-edge in the green synthesis of MIL-101(Cr) MOF based on organic and inorganic waste recycling with extraordinary removal for anionic dye

MIL-101(Cr) MOF (MIL-Materials of Institute Lavoisier; Metal-organic framework) as an adsorbent has great application in water treatment because of its high stability against air, temperature, and chemicals. Herein, we develop a novel value-added, sustainable, and eco-friendly green method to prepare MIL-101(Cr) hydrothermally based on organic and inorganic waste recycling (G-MIL-101(Cr)@R) without hydrofluoric acid (HF) addition. Several characterization techniques suggest that G-MIL-101(Cr)@R was successfully synthesized. Then, it was used as an adsorbent for acid blue 92 dye (AB-92) as a model of anionic dyes. The adsorption parameters were studied, such as adsorbent dose, contact time, pH, dye concentration, temperature, salinity, and dye selectivity. The results showed that the adsorption of AB-92 is a monolayer according to the Langmuir isotherm with a qmax of 2176 mg/g. Adsorption kinetics follow the pseudo second-order model (R2 = 0.99), occurring in three steps according to the intra-particle diffusion kinetic model. The adsorption of AB-92 over G-MIL-101(Cr)@R is spontaneous and exothermic. The adsorption mechanism is mainly defined by electrostatic interactions. G-MIL101(Cr)@R can adsorb the anionic dyes more efficiently than cationic dyes. It could also be reused for up to five cycles with an uptake efficiency of not less than 80 % without any change in its structure. Finally, G-MIL-101(Cr) @R is considered a superior adsorbent for anionic dyes. So, it will pave the way for developing MIL-101(Cr), based on organic and inorganic waste recycling, as an efficient adsorbent for removing organic dyes from wastewater.