Data on the fluoride adsorption from aqueous solutions by metal-organic frameworks (ZIF-8 and Uio-66)

The variables examined were initial fluoride concentration, ZIF-8 and Uio-66 dosage, pH, and contact time. The residual concentration of fluoride was measured by a spectrophotometer. According to BET, the specific surface area of the ZIF-8 and Uio-66 was 1050 m2/g and 800 m2/g, respectively. Total pore volume and average pore diameter of the ZIF-8 and Uio-66 were 0.57 cm3/g, 0.45 cm3/g and 4.5 nm, 3.2 nm, respectively. The best pH for fluoride adsorption was neutral conditions. By increasing the ZIF-8 and Uio-66 dose, the fluoride uptake increased at first, but then decreased. Also, the maximum adsorption for ZIF-8 and Uio-66 was observed in adsorbent dose 0.2 and 0.6 g/L, respectively. The best model for describing kinetic and isotherms of fluoride adsorption were the pseudo-second-order model and Langmuir isotherm model, respectively. Based on the Langmuir model, the adsorption capacity of fluoride by ZIF-8 and Uio-66 was reported to be 25 mg/g and 20 mg/g, respectively.


Subject area
Water treatment More specific subject area Adsorption Type of data Figures and tables How data was acquired Spectrophotometer (UV-UVIS, 570 nm) Data format Analyzed Experimental factors The main variables examined were initial concentration of fluoride, ZIF-8 and Uio-66 dosage, pH, and contact time. At first, a stock solution of fluoride (NaF, 1000 mg/l) was made and stored under standard conditions. At the end of the experiments, the remaining adsorbents were separated using a centrifuge (3000 rpm, 5 min). After separation, the residual fluoride was measured by a spectrophotometer DR-5000. Value of the data • The dataset will be useful for the application of the metal-organic framework in the fluoride adsorption from aqueous solutions. • The data of this project can be used to improve drinking water quality by the authorities.
• Information from this data, including, kinetic and isotherm constants, will be informative for predicting and modelling the adsorption capacity and mechanism of fluoride uptake by ZIF-8 and Uio-66. • The characterization data of the ZIF-8 and Uio-66 are useful for the scientific community to complete the studies for emerging absorbers.

Data
The XRD and SEM results of synthesized ZIF-8 and Uio-66 are shown in Fig. 1. All adsorption experiments were performed in triplicate. Results of BET present in Table 1 Table 2. As illustrated in Table 2, the pseudo-second-order model for ZIF-8 and Uio-66 has the highest R 2 (coefficient of determination). As a result, the model was the most suitable model to express the kinetics of the fluoride adsorption onto ZIF-8 and Uio-66. Calculated parameters of isotherm models for the fluoride adsorption onto ZIF-8 and Uio-66 are given in Table 3. As illustrated in Table 3, the Langmuir isotherm model for ZIF-8 and Uio-66 has the highest R 2 . As a result, the model was the most suitable model to express the isotherm of the fluoride adsorption onto ZIF-8 and Uio-66.

Materials
Chemicals used were zinc nitrate hexahydrate, methanol, N, N-dimethylformamide, zirconium chloride, 2-methylimidazole, and terephthalic acid. All the above-mentioned materials are prepared with high purity. The Materials were purchased from MERK and Sigma-Aldrich companies.

Synthesis of ZIF-8 and Uio-66
ZIF-8 was first synthesized. This adsorbent was synthesized based on the procedure presented by two previous works [1,2]. In the second step, the absorbent of Uio-66 was synthesized. For the synthesis of this absorbent, previous studies were used [3,4]. After synthesizing adsorbents, the general characterization of the adsorbent was determined based on XRD, SEM, and BET.       . At the end, the used adsorbents were separated using a centrifuge (3000 rpm, 5 min). After separation, the final concentration of fluoride was measured by a spectrophotometer DR-5000 (UV-UVIS, 570 nm) [5][6][7][8]. Finally, fluoride adsorbed (q e , mg/g) and the removal efficiency (%) on the ZIF-8 and Uio-66 was computed based on Eqs. (1) and (2), respectively [9,10]: