Ultra-High-Capacity Adsorption of Rhodamine B in a Carboxyl-Functionalized Metal–Organic Framework via Surface Adsorption

Abstract

The adsorption of rhodamine B (RhB) from aqueous solution on a functionalized metal–organic framework UiO-66-(COOH)2 was studied systematically in view of the adsorption isotherm, kinetics, thermodynamics, effect of pH and co-existing salts, and regeneration of the material. The adsorption behavior of RhB on UiO-66-(COOH)2 followed the Langmuir isotherm model and pseudo-second-order model. The thermodynamics study indicates that the adsorption of RhB is mainly controlled by the entropy effect rather than the enthalpy change. The strong electrostatic interaction as well as H-bond interaction contributes to the capture of RhB on the nanoscale UiO-66-(COOH)2 via the surface adsorption manner. UiO-66-(COOH)2 exhibited an ultra-high adsorption capacity of 2200 mg g–1 and excellent continuous removal ability. The high adsorption capacity, strong anti-interference ability, and easy regeneration make UiO-66-(COOH)2 as an ideal adsorbent for RhB removal from aqueous solution.

Rationally Tailoring Pore and Surface Properties of Metal–Organic Frameworks for Boosting Adsorption of Dy3+

“…Sodium benzoate was found to commonly improve the pore volume and BET specific surface area, attributed to the formation of defects. Among these materials, UiO-66-(COOH) 2 -B40 exhibits the highest BET specific surface area of 610.9 m 2 g –1 , superior to all of the reported values of UiO-66-(COOH) 2 . ,,, Meanwhile, it was also found that the specific surface areas of the micropore and mesopore can be boosted simultaneously along with increasing the amount of BCNa. The pore size distributions of the samples were collected based on the DFT method (Figure S4).…”

Recent Improvement Strategies on Metal-Organic Frameworks as Adsorbent, Catalyst, and Membrane for Wastewater Treatment

“…In most cases, MOFs adsorb organic pollutants through π‒π interactions. Thus, modifying MOFs by adding additional organic groups such as ‒NH 2 , ‒COOH, or ‒SO 3 H as functionalization could improve their adsorption capacity by providing an additional interaction through electrostatic attraction or hydrogen bonding [ 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 ]. Furthermore, ligand functionalization of MOFs could also enhance their pollutant adsorption selectivity, stability, and reusability.…”

“…An incredible improvement adsorption capacity of the MOFs against cationic pollutants could be attained by carboxyl functionalization. Gao et al presented that the carboxyl functionalized UiO-66, UiO-66-(COOH) 2 , could achieve ultra-high adsorption of rhodamine B (RhB) with the maximum adsorption capacity of 2200 mg/g at high RhB concentration, which is 11 times higher than its pristine form (200.4 mg/g) [ 72 ]. Carboxyl functionalization increased the RhB adsorption of UiO-66 by altering the surface charge of the MOF.…”

Ion-Exchange Resins for Efficient Removal of Colorants in Bis(hydroxyethyl) Terephthalate

“…Hence, a strong electrostatic force occurred between the colorant and D201 . When pH > pH pzc , the resin was occupied by excess OH – ions and in a negative charge state; hence, the electrostatic repulsive force was observed between the resin and colorant, and the adsorption attraction was very week . An increase in the equilibrium capacity at a lower pH implied that decoloration was probably due to electrostatic force along with ion exchange.…”