Effect of the Synergetic Interplay between the Electrostatic Interactions, Size of the Dye Molecules, and Adsorption Sites of MIL-101(Cr) on the Adsorption of Organic Dyes from Aqueous Solutions

Abstract

Herein, we report that the surface charge status and size of the metal–organic framework (MOF) MIL-101­(Cr) can be tailored by varying the concentration of tetramethylammonium hydroxide. The adsorption capacity of MIL-101­(Cr)-2 toward the anionic dye Congo red (CR) was found to be significantly higher than that of other MIL-101­(Cr) adsorbents, although MIL-101­(Cr)-3 microcrystals exhibited the highest adsorption capacity toward the anionic dye methyl orange (MO) due to the different adsorption mechanisms involved. This is the first demonstration of the synergetic interplay between the electrostatic and π–π interactions, adsorption spaces and sites, and size of the dye molecules, in terms of the uptake capacity of an adsorbent. In addition, the obtained results shed new light on the adsorption mechanism toward organic dyes over MOFs. Moreover, the MIL-101­(Cr) microparticles exhibited excellent adsorption capabilities toward CR, achieving a maximum capacity of 1367.1 mg g–1, which is higher than the majority of reported values for other materials. Therefore, these results indicate that the MIL-101­(Cr) nanostructure exhibits potential for application in the treatment of anionic dye-containing wastewater.

Surface Modification of Magnesium Ferrite Nanoparticles for Selective and Sustainable Remediation of Congo Red

“…The removal efficiencies for IC (∼95%) and CR (∼98%) in the MO-based binary solutions are high (see Figure 3d) and similar to those in the single-component systems (see Figure 1). Higher removal efficiencies for IC and CR than that for MO are due to stronger electrostatic 25,29,31 and hydrogen-bonding 28,31,35 interactions, as mentioned in Section 3.1.1.…”

“…16 The behavior of the dye contaminant can be influenced by several factors such as charges, the number of binding sites, and so on. 25 In the set of cationic dyes, low removal efficiencies for MB (∼8%) and RhB (∼2%) are obtained at pH values ranging from ∼3 to ∼7 (see Figure 1). Within this pH range, the MgFe 2 O 4 −NH 2 surface exists as positively charged (pH < 8.4), which leads to strong electrostatic repulsion between the positively charged surface of the adsorbent and the positive charges on the MB and RhB molecules (see the structures in Table 1).…”

“…IC and CR contain a greater negative charge than MO, leading to stronger binding to the positively charged MgFe 2 O 4 −NH 2 nanoadsorbent surface. 25,29,31 Additionally, hydrogen bonding plays an important role in IC and CR removal since IC and CR contain primary and secondary amines that offer greater opportunity to form hydrogen bonding with the nanoadsorbent. 28,31,35 Consequently, the MgFe 2 O 4 −NH 2 nanoadsorbent efficiently removes anionic dyes, particularly IC and In the set of the anionic/neutral binary solution, the color of the IC/NR mixture faded from purple to light yellow (see Figure 2c).…”

Low-Temperature and Additive-Free Synthesis of Spherical MIL-101(Cr) with Enhanced Dye Adsorption Performance

“…For instance, MIL-101(Cr) showed high adsorption efficiency toward MO in an aqueous solution [61]. Yang et al reported that MIL-101(Cr) can be used as an adsorbent for the removal of Congo red (CR) [62]. Chen et al found that MIL-101(Cr) exhibited high uptake toward xylenol orange (XO) [63].…”

Adsorption of Dibenzothiophene in Gasoline by Si-MCM-41/Sodium Alginate Porous Hybrid Membrane

“…is the highest. It may be that when the content of Si-MCM-41 is lower than 8 wt%, the pore size of Si-MCM-41 become the main factor affecting the adsorption effect [28][29]. With the increase of Si-MCM-41 content, agglomeration began to occur, which reduce the number of active sites contacting with DBT and limite the increase of adsorption capacity.…”