Terbium metal–organic frameworks for the efficient removal of tartrazine food dye from aquatic systems: Thermodynamics, kinetics, isotherm, and box-behnken design optimization

Abstract

The elimination and removal of the yellow food coloring tartrazine dye E-102 (TZ) from aqueous solutions was conducted using stacked nanorods made of Terbium metal–organic frameworks (Tb-MOF). The adsorbent was assessed using various methods including FTIR, BET, XRD, XPS, SEM, and TEM. The results showed that the surface area decreased from 1123.07 to 762.8 m².g⁻¹, the pore volume reduced from 4.02 to 2.6 cc/g, and the pore size decreased from 7.8 to 3.2 nm after adsorption. The reduction in surface area, pore volume, and pore size post-TZ dye adsorption indicates that some of the adsorption mechanisms took place through the pores of the adsorbent. Examined the impact of temperature, pH, initial dye concentration, and contact time on the removal of TZ dye. The adsorption of TZ was found to conform to the Langmuir isotherm and pseudo-second-order kinetic model. The maximum adsorption capacity for TZ was determined to be 817.63 mg/g. The resulting pH_zpc value of 5.36 indicates that adsorption of anionic dyes, such as TZ dye, is advantageous at pH levels below 5.36. Moreover, the adsorption process exhibited an adsorption energy of 23.78 kJ/mol, suggesting the presence of a chemisorption mechanism. The thermodynamic parameters calculated indicate that the adsorption processes are both spontaneous and endothermic. It is advisable to utilize the Tb-MOF adsorbent for a total of five cycles, as the adsorbent’s ability to regenerate suggests that treating industrial wastewater can be achieved easily and efficiently. The efficiency of the adsorption process was enhanced through optimization using the Box-Behnken Design (BBD).