1 Asian Review of Environmental and Earth Sciences Vol. 5, No. 1, 1-7, 2018 ISSN(E) 2313-8173/ ISSN(P) 2518-0134 DOI: 10.20448/journal.506.2018.51.1.7 Adsorptive Removal of a Pharmaceutical and Personal Care Product Oxybenzone from Water with Metal-Organic Frameworks Naz Fathma Tumpa1✍ Yeon-Koo Jeong2 (+ Corresponding Author) 1,2Department of Environmental Engineering, Waste management and Resource recycling Research lab, Kumoh National Institute of Technology, Gumi, Republic of Korea Abstract Oxybenzone, one of the most often detected pharmaceuticals and personal care products (PPCPS), from aqueous solutions and this PPCPs removal from water had been studied by using the highly porous metal-organic framework (MOF) ) MIL-101(Cr) and a modified MIL-101(Cr) called MIL- 101-OH. Adsorption results showed that MIL-101-OH which contains functional group such as – OH, which was very effective for oxybenzone adsorption. The adsorption performance of MIL- 101-OH over MIL-101-OH was found to be greater than that of MIL-101(Cr), which means the functionalization of primitive MOFs have a positive effect on adsorption. The kinetics of MIL- 101-OH also showed higher result compare to MIL-101(Cr). So along with a high adsorption capacity and repaid adsorption which is important for commercial applications. Keywords: Personal care product, Metal-organic frameworks, oxybenzone, adsorption, porous materials, aqueous solution Citation | Naz Fathma Tumpa; Yeon-Koo Jeong (2018). Adsorptive Removal of a Pharmaceutical and Personal Care Product oxybenzone from Water with Metal-Organic Frameworks. Asian Review of Environmental and Earth Sciences, 5(1): 1-7. History: Received: 3 November 2017 Revised: 20 December 2017 Accepted: 3 January 2018 Published: 8 January 2018 Licensed: This work is licensed under a Creative Commons Attribution 3.0 License Publisher: Asian Online Journal Publishing Group Contribution/Acknowledgement: Both authors contributed to the conception and design of the study. Funding: This research was supported by Kumoh National Institute of Technology (KIT), Gumi, Republic of Korea. Competing Interests: The authors declare that they have no conflict of interests. Transparency: The authors confirm that the manuscript is an honest, accurate, and transparent account of the study was reported; that no vital features of the study have been omitted; and that any discrepancies from the study as planned have been explained. Ethical: This study follows all ethical practices during writing. Contents 1. Introduction ........................................................................................................................................................................ 2 2. Experimental ...................................................................................................................................................................... 2 3. Results and Discussion .................................................................................................................................................... 3 4. Conclusion ........................................................................................................................................................................... 5 References ................................................................................................................................................................................ 5 http://crossmark.crossref.org/dialog/?doi=10.20448/journal.506.2018.51.1.7&domain=pdf&date_stamp=2017-01-14 http://creativecommons.org/licenses/by/3.0/ http://creativecommons.org/licenses/by/3.0/ https://orcid.org/0000-0003-0992-4122 https://orcid.org/0000-0002-1612-8194 https://orcid.org/0000-0003-0992-4122 https://orcid.org/0000-0002-1612-8194 https://orcid.org/0000-0003-0992-4122 https://orcid.org/0000-0002-1612-8194 https://orcid.org/0000-0003-0992-4122 https://orcid.org/0000-0002-1612-8194 Asian Review of Environmental and Earth Sciences, 2018, 5(1): 1-7 2 1. Introduction The use of pharmaceuticals and personal care products (PPCPS) is increasing day by day because of the increasing population all over the world, urbanization and living standards. For example the presence of PPCPs is already detectable in surface water, as in ground water [1-3] and bioaccumulation of these persistent PPCPs in the aquatic life will become a threat to the environment [4, 5]. PPCPs may often remain in the environment even after they have been consumed completely [3, 6-10] because PPCPs usually have long shelf lives to meet customer’s demands, and some PPCPs are inadvertently dumped into environment; therefore, PPCPs are typical examples of so-called emerging contaminants [9, 10]. Oxybenzone (the structure of which is shown in scheme 1) is a component of many sunscreen lotions, is regarded as typical emerging contaminants with high environmental risk. The chemical structure of oxybenzone has various functional groups such as phenol, ketone groups that can interact effectively with adsorbents such as modified / functionalized MOFs. (2-Hydroxy-4-methoxyphenyl)-phenylmthanone [C14H12O2] Scheme-1. Chemical structure of Oxybenzone Over last few decades, significant advancements have been achieved in the field of porous materials because of the development of new functional materials, including metal-organic frameworks (MOFs) [11-19]. MOFs are receiving much attentions because of their high porosity, with their pore size/shape being controllable over both microporous and mesoporous regions. The physiochemical properties of MOF materials can be turned with easy modifications or functionalization, which ultimately increases their usability in various applications, such as adsorption [20-22] separation [23] and catalysis [24] For example MOFs have recently been successfully used for fuel purification via adsorptive desulfurization [25-27] or denitrogenation [28-30]. MOFs have also been used for the aqueous-phase adsorption of different pollutants in water, such as heavy metals [31] phosphate [32] organics dyes [33-36] organic arsenic acids [37, 38] bisphenol-A [39, 40] and PPCPs (naproxen and clofibric acid) ) [41-43] from water. In this study, we used MIL-101, MIL-101-OH and Oxybenzone as representatives MOF and PPCP, respectively. 2. Experimental 2.1 Chemicals and Synthesis and Modification of Adsorbent Reagents and solvents were commercially available products and used without any further purification. Chromium (III) nitrate nanohydrate (Cr(NO3)3.9H2O) (99%) and terephthalic acid (TPA,99%) were purchased from Daejung and Junsei Chemicals, repectively. Ethanolamine (ETA,98%) was obtained from Alfa Aesar. Toluene (99.5%) was procured from Daejung Chemicals. N,N-Dimethylformamide (99%) and ethanol (99.5%) for the purification of the MOFs were obtained from Daejung Chemicals. Methanol and acetone were obtained from Daejung Chemicals, and Oxybenzone was obtained from Alfa Aesar. MIL-101 was synthesized from Cr(NO3)3.9H2O, TPA, and deionized water similar to a previously described method [44-46]. Cr(NO3)3.9H2O (4.0 g) 10 mmol, terephthalic acid (TPA) (1.66 g) 10 mmol, and deionized water (40mL) were blended and briefly sonicated resulting in a dark blue-color suspension. The suspension was then placed in a Teflon-lined autoclave bomb and was kept in an oven at 220°C for 17 h without stirring. After the reaction, autoclave was cool to room temperature. After that the MOF solids with green-colored was separated from water using a centrifuge (3,134xg, 15min) and was washed with water, methanol and acetone. The suspension in acetone was centrifuged and separated, to remove the unreacted TPA, the solids was placed in N,N- dimethylformamide (40 mL) and the suspension was sonicated for 10 min and then keep at 70 °C overnight. The resulting solids were separated by centrifugation, repeatedly washed with methanol and acetone, was dried at 100°C overnight. The –OH functionalized MIL-101s name MIL-101-OH was synthesized via grafting utilizing reported procedures [43, 47]. Before functionalization, MIL-101 was dehydrated at 150 0C for 12 h in a vacuum oven to generate CUSs (coordinatively unsaturated sites ).The dehydrated MIL-101 (0.6 g) was suspended in anhydrous toluene (60 mL) in a round-bottom flask equippe with a reflux condenser and a magnetic stirrer, and each of 2 mmol of ETA (Ethanolamine) was added to this suspension. The mixture continuously was stirred and refluxed for 12 h. The obtaind solid was cool to room temperature, was separated and was washed with ethanol/de-ionized water, and was dried at room temperature and then the MOFs solid was kept in desiccators for further use. 2.2 Characterization X-ray powder diffraction patterns were obtained with a diffractometer (SWXD, CuKα radiation). FT–IR spectra were recorded on a Hyperion-2000 (ATR, maximum resolution). The nitrogen adsorptions of the adsorbents was obtain at -196 0C with a surface area and porosity analyzer (BRLSORP-max) after evacuation at 150 0C for 12 h. The surface area of adsorbents was calculated using the BET equation. Asian Review of Environmental and Earth Sciences, 2018, 5(1): 1-7 3 2.3 General Procedures for the Adsorption Experiments Oxybenzone solutions with the desired concentrations were prepared using deionized water. An oxybenzone calibration curve was prepared by determining the absorbance at 230 nm with a series of standard oxybenzone solutions (1–10 mg/L), and the initial or equilibrium concentrations of oxybenzone was calculated with the calibration curve. Formerly to adsorption, the sample was dried for 12 h at 100 0C under vacuum conditions. For each adsorption experiment, approximately 5 mg of the sample was added to the oxybenzone solution (50mL, fixed concentration) and was stirred for 10 min to 12 h at 25 0C. After stirring the solution, the adsorbents was filtered with a syringe filter (PTFE, 0.45 µm) and the oxybenzone concentration was determined from the absorbance of the UV spectrum. In the case of a high oxybenzone concentration, the UV analysis was conducted after consecutive dilutions of the oxybenzone solutions. The following mass-balance relation (Eq.1) was used to determine the amount of adsorbed oxybenzone ⁄ - - - - - - - - - - - - - - (1) where C0 (mg/L) was the initial concentration, Ct (mg/L) was the concentration at time t, V(L) was the volume of the oxybenzone solution and w(g) was the weight of the adsorbents. 3. Results and Discussion 3.1 Characterization of the Adsorbents The XRD patterns of the MIL-101s shown in Fig. 1a was accommodating with simulated one [43, 44] confirmed the MIL-101s were successfully prepared and that the crystal structure of pristine MIL-101 does not change with functionalization. However, the XRD intensities of the MIL-101s decreased slightly on modification, particularly those of MIL-101-(OH), probably because of some severe conditions which was required for these modifications. The nitrogen adsorption isotherms of the MIL-101s and the BET surface areas (Table 1) obtained from these isotherms show that the MIL-101s have considerable porosities, although functionalization (to introduce –OH group) reduced the porosities. This reduction could be due to the volumes of the functional groups and/or the decreased crystallinity with modifications (as shown by the XRD patterns). FTIR spectra of the modified MOFs shown in Fig. 2c confirmed the grafting was successful based on the presence of the band at 1216 cm−1, which originate from the C-N stretching of the grafting agents [48]. (b) (Blue color – MIL-101(Cr) & Red color- MIL-101-OH) Figure-1. (a) XRD patterns, and (b) FTIR spectra of MIL-101s Table-1. BET surface areas and total pore volume of MIL-101s Adsorbent BET surface area SABET(m2/g) Total pore volume [cm3 g-1] MIL-101(Cr) 2,534.4 1.847 MIL-101-OH 1,951.5 0.9615 3.2 Adsorption Isotherms and Kinetics Results Isotherms for oxybenzone adsorption by MIL-101s were obtained at 20-25 °C after 12 h of adsorption, which is sufficient for equilibrium, and the results are shown in Fig. 3. The adsorbed amounts (based on weight of MIL- 101s) at equilibrium decreased in the order MIL-101–OH > MIL-101, which was the same order as observed for quantity adsorbed after various times with different concentration (Fig.2). The maximum adsorbed quantities (Q0) obtained from Langmuir plots are summarized in Table 2, and the results again show that MIL-101s functionalized with –OH groups were highly effective at adsorbing oxybenzone from water. Table-2. Relative adsorbed amounts of PPCPs over the two MOFs (MIL-101, MIL-101-OH) after 12 h of Adsorption MOFs PPCPs Maximum adsorption (Q0 mg/g) r² MIL-101(Cr) Oxybenzone 73.50 0.9999 MIL-101-OH Oxybenzone 121 0.9998 Isotherms for ibuprofen adsorption by MIL-101s were obtained at 25 °C after 12 h of adsorption, which is sufficient for equilibrium, and the results are shown in Fig. 3. The adsorbed amounts (based on weight of MIL- Asian Review of Environmental and Earth Sciences, 2018, 5(1): 1-7 4 101s) at equilibrium decreased in the order MIL-101–OH > MIL-101, which was the same order as observed for quantity adsorbed after various times (Fig.2). The maximum adsorbed quantities (Q0) obtained from Langmuir plots are summarized in Table 1, and the results again show that MIL-101s functionalized with –OH groups were highly effective at adsorbing ibuprofen from water. (a) MIL-101(Cr) (b) MIL-101(Cr) Figure-2. Effect of adsorption times on the adsorbed amounts of oxybenzone over (a) MIL-101(Cr) and (b) MIL-101-OH. Show the adsorbed amounts of oxybenzone based on the unit weight of adsorbents. The initial concentration of oxybenzone was (10-50 ppm.) The kinetics of oxybenzone adsorption of different concentration over MIL-101(Cr) and MIL-101-OH had been calculated. Oxybenzone adsorption kinetics followed previously described method [49] the pseudo-second- order equation can exactly illustrated. The Equation (2) for pseudo-second-order model which can explain the kinetics has given below - - - - - - - - - - - - - - - - - -- (2) qt(mg/g) at time t, the amount of adsorbed, qe (mg/g) at equilibrium stage the amount of adsorbed, t(hour) time (adsorption time) and k2(g/mg, hour) pseudo-second-order rate constant. The kinetics results of oxybenzone adsorption over MIL-101s have been given in Table 3. The kinetics of oxybenzon adsorption over MIL-101s showed that the qe value and k2 value of oxybenzone adsorption over MIL-101(Cr) and MIL-101-OH were decreased in the order of MIL-101-OH > MIL-101(Cr) respectively. The kinetics of oxybenzon adsorption over MIL-101s showed that the qe value and k2 value of oxybenzone adsorption over MIL-101(Cr) and MIL-101-OH were decreased in the order of MIL-101-OH > MIL-101(Cr) respectively. 0 20 40 60 80 100 120 0 2 4 6 8 10 12 14 A m o u n t ad so rb ed ( m g/ g) Time (h) 50 ppm 40 ppm 30 ppm 20 ppm 10 ppm 0 20 40 60 80 100 120 0 2 4 6 8 10 12 14 A m o u n t ad so rb ed ( m g/ g) Time (h) 50 ppm 40 ppm 30 ppm 20 ppm 10 ppm Asian Review of Environmental and Earth Sciences, 2018, 5(1): 1-7 5 Table-3. The kinetics of oxybenzone adsorption over MIL-101(Cr) and MIL-101-OH. [when the Concentrations of oxybenzone solutions were 40 & 50ppm] MOF(adsorbent) Initial concentration qe (mg/g) k2(g/mg,hour) MIL-101(Cr) 10ppm 47.26 0.0291 20ppm 63.59 0.0305 30ppm 67.90 0.0312 40ppm 69.92 0.0372 50ppm 70.94 0.0475 MIL-101-OH 10ppm 60.25 0.0385 20ppm 81.05 0.0403 30ppm 92.34 0.0422 40ppm 102.12 0.0528 50ppm 104.16 0.0561 Figure-3. Adsorption isotherms of oxybenzone over (a) MIL-101 and (b) MIL-101-OH (at 20- 25 °C) 3.3 Discussion From the above tables (Table 2 and Table 3), Q0 means the highest oxybenzone adsorption capacity of MOFs and qe means the adsorbed amount during equilibrium. So in this research the highest oxybenzone adsorption capacity of MIL-101(Cr) was 73.50 mg/g (based on unit weight of MIL-101) and highest oxybenzone adsorption capacity of MIL-101-OH was 120 mg/g (based on unit weight of MIL-101-OH) and the kinetics of oxybenzon adsorption over MIL-101s showed that the qe value and k2 value of oxybenzone adsorption over MIL-101(Cr) and MIL-101-OH were decreased in the order of MIL-101-OH > MIL-101(Cr)respectively. So on the basis of comparison the adsorption capacity of MIL-101-OH was higher than the adsorption capacity of MIL-101(Cr), and oxybenzone’s adsorption capacity of both MOFs were decreased on the order MIL-101-OH > MIL-101(Cr) (based on unit weight). The reason for which, MIL-101-OH oxybenzone’s adsorption capacity was higher compared to MIL-101(Cr) because it contain H-bonding and that H-bonding was maybe responsible for making MIL-101-OH more capable for oxybenzone’s higher adsorption. 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