Adsorption Studies of Anionic and Cationic Dyes on MIL-100(Cr) Synthesized Using Facile and Green Mechanochemical Method.

The discharge of anionic and cationic synthetic dyes into the environment can cause significant health and environmental problems. Adsorption is promoted as one of the efficient methods to solve this issue. In this work, a metal-organic framework, namely Materials of Institut Lavoisier-100(Cr) denoted as MIL-100(Cr), was synthesized mechanochemically through manual grinding without adding HF as modulator and solvent with 15 h of crystallization time. The synthesized material was employed as an adsorbent for methyl orange (MO) and methyl violet (MV). The obtained material was characterized by X-ray diffraction and FTIR spectroscopy techniques. A few parameters affecting adsorption capacity were studied: including optimum pH, contact time, and initial dyes concentration. The results showed that SEM images revealed the synthesized MIL-100(Cr) has irregular polyhedron morphology, and it is thermally stable up to 375 °C based on TGA measurement. Nitrogen sorption isotherm confirmed that MIL-100(Cr) possesses high surface area and pore volume up to 1557 m2/g, and 0.76 cm3/g, respectively, and can be classified as microporous material with pore diameter of 1.82 nm. In addition, the adsorbed MO and MV were evidenced by the presence of new peaks in the FTIR spectra of MIL-100(Cr) after adsorption at 2930, 1587, 1177, 1118 cm−1 for MO adsorption and 1170, 2971 cm−1 for MV adsorption. Moreover, MIL-100 (Cr) has the maximum adsorption capacity toward MO and MV of 430.21 mg/g (MO: pH = 4, t = 60 min) and 120.48 mg/g (MV: pH = 9, t = 150 min), respectively. The MO and MV adsorption mechanism is dominated by physisorption via electrostatic interactions due to the porosity features of the adsorbent. Furthermore, it also may be followed by π–π stacking, ion-dipole interactions, and hydrogen bonds. MO and MV adsorption kinetics were described by pseudo-second-order. The nonlinearity of the intraparticle diffusion plot graph confirmed any contribution from the pore and surface of MIL-100(Cr). The MO and MV adsorption isotherm models were in good agreement with the Langmuir isotherm. [ABSTRACT FROM AUTHOR]