Sulfonic-functionalized MIL-100-Fe MOF for the removal of diclofenac from water

In this work, a novel adsorbent (MIL-100-Fe-AMSA), for the removal of the nonsteroidal anti-inflammatory drug sodium diclofenac (DCF), was prepared by grafting aminomethanesulfonic acid to the open iron sites in a porous MIL-100-Fe MOF obtained by a green microwave-assisted synthesis.

Available online 9 December 2022

1387-1811/© 2022 The Authors Published by Elsevier Inc This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/)

Sulfonic-functionalized MIL-100-Fe MOF for the removal of diclofenac

from water

Neus Crespí S´anchez , Gemma Turnes Palomino**, Carlos Palomino Cabello*

Department of Chemistry, University of the Balearic Islands, Palma de Mallorca, E-07122, Spain

A R T I C L E I N F O

Keywords:

Sulfonic-grafted metal-organic frameworks

3D printing

Functional devices

Removal of pollutants

Diclofenac

A B S T R A C T

In this work, a novel adsorbent (MIL-100-Fe-AMSA), for the removal of the nonsteroidal anti-inflammatory drug sodium diclofenac (DCF), was prepared by grafting aminomethanesulfonic acid to the open iron sites in a porous MIL-100-Fe MOF obtained by a green microwave-assisted synthesis The obtained materials were characterized

by XRD, N2 adsorption-desorption, FTIR spectroscopy of adsorbed CO, electron microscopy and EDS spectros-copy MIL-100-Fe-AMSA showed fast adsorption kinetics and an excellent maximum adsorption capacity of 476 mg/g Synergistic effect of H-bonding, between the electronegative ionized –SO3H groups of MIL-100-Fe-AMSA and –NH group of DCF, and π−π interactions between the aromatic rings that are present in both MOF and pollutant, is probably the main mechanism of adsorption In addition, the developed functionalized-MOF showed excellent reusability for at least five consecutive adsorption-desorption cycles, demonstrating its stability and potential for the removal of DCF For practical applications, the prepared MIL-100-Fe-AMSA was incorporated into a 3D printed column for flow-through solid-phase extraction of pharmaceuticals pollutants before HPLC determination The functional device showed excellent performance for the preconcentration and further detection and quantification of ketoprofen and DCF pollutants

1 Introduction

Water is one of the most important natural resources for life on our

planet [1] Nowadays, the rapid progress of modern industry and

pop-ulation growth have led to the contamination of water with a variety of

different organic pollutants, this having become a major global problem

[2,3] Particularly, pharmaceutical compounds, such as antibiotics,

anti-inflammatory drugs, analgesics, and hormones, and their

metabo-lites have attracted attention due to their potential harmful effects to

human health and ecosystems [4,5] The inadvertently release of these

compounds into the environment and their ineffective removal by

wastewater treatment plants (WWWTPs) have led to their detection in

different water resources, including drinking water [6–8] Therefore, a

lot of research is being carried out on the elimination of pharmaceuticals

from water

Various strategies have been explored to remove pharmaceuticals

from water bodies, such as chlorination [9], biodegradation [10],

pho-tocatalysis [11], coagulation-flocculation [12] or advanced oxidation

processes (AOPs) [13] However, these methodologies are limited due to

their high energy consumption, low effectiveness and the generation of residual byproducts that can also be toxic Adsorption by porous mate-rials is considered one of the cheapest, simplest, most efficient and competitive methods for pharmaceuticals removal [14–16] Common adsorbents include carbonaceous materials [17,18], zeolites [19,20], and mesoporous silica [21,22] However, most of these solids have shortcomings such as low extraction capacity and poor adsorption selectivity, and therefore, there is a need to develop novel porous ma-terials with high adsorption efficiency

Recently, metal-organic frameworks (MOFs), a relatively new family

of materials that are built up from the union of organic ligands and metal centers, have shown high potential in the adsorption removal of phar-maceuticals from water due to their unique characteristics, such as simple synthesis, large surface area, tunable pore size and presence of metal active sites [23–27] Compared to conventional adsorbents, many MOFs exhibit superior extraction performance thanks to their ability of establishing different and multiple interactions with organic pollutants, including electrostatic interactions, acid-base interactions, H-bonding and π-π stacking [28–30] In this context, it has been reported that the

* Corresponding author

** Corresponding author

E-mail addresses: g.turnes@uib.es (G Turnes Palomino), carlos.palomino@uib.es (C Palomino Cabello)

Contents lists available at ScienceDirect Microporous and Mesoporous Materials journal homepage: www.elsevier.com/locate/micromeso

https://doi.org/10.1016/j.micromeso.2022.112398

Received 8 October 2022; Received in revised form 5 December 2022; Accepted 7 December 2022

incorporation of functional groups in MOFs, through functionalization

of the organic linker or the inorganic building blocks, is key to favoring

and strengthening these interactions, thus improving the adsorption of

pharmaceuticals [31,32] For example, Hasan et al [33] synthesized

MIL-101 functionalized with acidic (-SO3H) and basic (-NH2) groups, by

grafting them to the coordinatively unsaturated Cr3+centers of the

MOF, and used the functionalized MOFs to extract naproxen and

clofi-bric acid In the case of the adsorption of naproxen and cloficlofi-bric acid

over the amino-functionalized MIL-101 was 1.17 and 1.10 times higher

than that of the bare MIL-101, respectively, due to the acid-base

inter-action between the basic adsorbent and the acidic adsorbates A similar

approach was used by Song et al [34] to prepare MIL-101 MOFs with

different number of –OH groups for the extraction of five

pharmaceu-ticals and personal care products The MIL-101 material with the highest

concentration of –OH groups, MIL-101-(OH)3, showed a maximum

adsorption capacity of 80 and 156 mg/g for the ketoprofen and

nap-roxen, respectively, which was attributed to H-bonding between the

adsorbent (H-donor) and the pollutants (H-acceptors) On the other

hand, using 2-sulfoterephthalic acid monosodium salt as a linker,

MIL-101-SO3H material with high surface area (1760 m2/g) has been

obtained and tested in the extraction of three fluoroquinolone

antibi-otics [35] Thanks to the electrostatic interaction between the ionized

sulfonic acid groups and positive charged segment of fluoroquinolone

molecules, very high adsorption capacities between 408 and 426 mg/g

were obtained Very recently, it has also been reported the

functionali-zation of UiO-66-(COOH)2 with copper and iron and their use as

sor-bents for the removal of the nonsteroidal anti-inflammatory drug

diclofenac sodium [36] Due to H-bonding and metal-π interactions,

UiO-66-(COOFe)2 showed the maximum adsorption capacity followed

by UiO-66-(COOCu)2 and UiO-66-(COOH)2

One of the most important limitations for the removal of pollutants

from water by MOFs is their recovery after extraction, since it includes

tedious and incomplete filtration and centrifugation steps In order to

facilitate the post-extraction procedure, and thus enhance the

applica-bility of MOFs as sorbents, different strategies have been developed,

including the preparation of MOFs with magnetic properties or their

immobilization on robust supports [37,38] Through this last approach,

promising functional materials for the extraction of organic pollutants

have been obtained, such as MIL-125(Ti)-chitosan membranes [39],

ZIF-8/polyacrylonitrile fibers [40], polydopamine/Zr-MOF foams [41],

and MIL-101(Cr)/chitosan composite beads [42], among others In this

context, recently, additive manufacturing (3D printing) has emerged as

a powerful tool for the preparation of novel functional 3D printed

de-vices for the removal of pollutants from water [43–45]

In this work, we report the preparation of a novel adsorbent by

grafting aminomethane sulfonic acid (AMSA) to coordinatively

unsat-urated iron sites of MIL-100-Fe, an iron-benzenetricarboxylate MOF

characterized by its low cost, great porosity and water stability, that was

prepared in 10 min by microwave-assisted method The developed

sulfonic-functionalized MIL-100-Fe was used for the removal of

diclo-fenac, the non-steroidal anti-inflammatory drug that presents the most

important acute toxic effects on biota The kinetics, maximum

adsorp-tion capacity, reusability and the influence of the pH of the extracadsorp-tion

medium were studied After batch experiments, the functionalized MIL-

100 material was immobilized in a 3D column by a simple and fast

coating method and used for the extraction and preconcentration of two

pharmaceutical compounds

2 Experimental section

2.1 Chemicals

Hydrochloric acid (HCl, 37.0%), methanol (≥99.8%), N,N-

dimethylformamide (DMF, 99.5%) and acetone (≥99.8%) were

ac-quired from Scharlau 1,3,5-benzenetricarboxylic acid (H3BTC, >98%)

and aminomethanesulfonic acid (AMSA, 97%) were obtained from

ACROS Organics Diclofenac sodium salt (DCF, ≥98.0%), poly-vinylidene difluoride (PVDF, MW ~ 180,000), ketoprofen (≥98%) and sodium hydroxide (NaOH, ≥97.0%) were obtained from Aldrich Iron (III) chloride hexahydrate (FeCl3⋅6H2O, >97%) was acquired from Panreac Ultrapure water (18.2 MΩ cm) was obtained from a Milli-Q water generator

2.2 Synthesis of MIL-100-Fe

Iron-based MIL-100 was synthesized using a rapid microwave- assisted method by adapting a procedure described in a previous report [46] Typically, 2.43 g of FeCl3⋅6H2O were dissolved in 30 mL of water After that, 0.84 g of 1,3,5-benzenetricarboxylic acid were added under constant stirring The resulting mixture was introduced to a Teflon vessel and heated at 403 K for 10 min in a microwave oven The obtained light brown solid was separated by centrifugation and washed three times with water and ethanol Finally, the product was treated with 150 mL of ethanol at 373 K for 24 h

2.3 Synthesis of sulfonic-functionalized MIL-100 (MIL-100-Fe-AMSA)

MIL-100-Fe was functionalized following an adaptation of the experimental procedure reported by Hasan et al [33] Before func-tionalization, 0.5 g of MOF were activated at 453 K for 12 h in a round bottom flask with continuous circulation of N2 to generate coor-dinatively unsaturated sites (CUSs) After activation, MIL-100-Fe was suspended in 50 mL of ethanol, and 1 mmol of AMSA was added The mixture was stirred under reflux overnight The obtained solid was filtered, washed with ethanol and then dried at room temperature

2.4 Fabrication of 3D printed column

The design of the 3D printed column with integrated packing based

on interconnected cubes was carried out using the software Rhinoceros 5.0 SR11 32 (McNeel & Associates, USA) This device was 3D printed vertically with stand with 1016 layers at a resolution of 0.500 mm using the SLA technique In order to remove unreacted monomers, the 3D printed column was washed with 2-propanol and then dried at room temperature Finally, the UV post-curing was carried out for 4 h at 365

nm

2.5 Immobilization of MIL-100-Fe-AMSA in 3D printed column

MIL-100-Fe-AMSA/3D column was prepared by an easy coating method using a concentrated ink [47] Basically, 150 mg of MIL-100-Fe-AMSA were dispersed in 5 mL of acetone through sonication for 30 min Then, the dispersion was mixed with 1 g of PVDF solution (7.5 wt% in DMF), and the resulting mixture was sonicated for another

30 min, and subsequently concentrated by acetone evaporation using gentle nitrogen flow The obtained dispersion was pumped through the 3D printed column and, after removing the excess of dispersion using a nitrogen stream, the 3D device was introduced in an oven at 333 K to eliminate DMF

2.6 Characterization

Nitrogen adsorption-desorption isotherms were acquired at 77 K by using a TriStar II (Micromeritics) gas adsorption instrument The sam-ples were previously activated at 423 K for 15 h Data were analysed using the Brunauer-Emmett-Teller model (BET) to obtain the specific surface area and the two-dimensional non-local density functional the-ory model (2D-NLDFT) to determine the pore size distribution The X- ray diffraction (XRD) patterns were obtained using CuKα radiation on a Bruker D8 Advance diffractometer The morphology and elemental distribution of the prepared materials were studied by using a scanning electron microscope (SEM) Hitachi S–3400 N, equipped with a Bruker

AXS Xflash 4010 energy-dispersive X-ray spectroscopy (EDS) system,

and transmission electron microscope (TEM) ThermoScientific Talos

F200i operated at 200 kV Fourier transform infrared (FTIR) spectra

were acquired using a Bruker 80v spectrometer equipped with an MCT

cryodetector For IR experiments, thin self-supported wafers of the MOF

samples were prepared and outgassed in a dynamic vacuum at 453 K for

8 h After this activation treatment, carbon monoxide was dosed into the

cell to study the open metal centers Zeta potential was measured by

employing a Zetasizer Nano ZS90 (Malvern) A Formlabs Form 2 3D

Printer and clear photoactive resin composed of methacrylate

mono-mers/oligomers and initiator (Formlabs Clear V4 (FLGPCL04)) were

used for device fabrication For post-curing the 3D printed devices, an

Upland CL-1000 ultraviolet crosslinker with a 365 nm UV lamp was

used

2.7 Adsorption experiments in batch conditions

DCF solutions with different concentrations were obtained by

diluting a stock solution of DCF (1 g/L) with deionized water All the

batch experiments were carried out at room temperature with 1 mg of

sample (MIL-100-Fe or MIL-100-Fe-AMSA) per ml of DCF aqueous

so-lution Adsorption isotherms experiments were conducted in a

concen-tration range of 10–700 mg/L of DCF during 24 h to ensure the

equilibrium conditions The pollutant concentration after the adsorption

process was determined by UV–Vis spectrophotometer (Cary 300 Bio) at

276 nm The maximum adsorption capacity was obtained using the

linearized form of the Langmuir equation [48], which is commonly

represented as:

C e

q e

= C e

q max

q max ⋅k

where C e is the remaining DCF concentration (mg/L) at equilibrium, q e

(mg/g) is the quantity of DCF adsorbed, qmax is the maximum adsorption

capacity (mg/g), and k is the Langmuir constant (L/mg)

Kinetic studies were carried out with the initial DCF concentration of

100 mg/L and measuring the concentration of remaining pollutant in

solution at appropriate time intervals Adsorption data was analysed

with a pseudo-second-order adsorption model [49], whose

linearized-integral form is expressed by the following equation:

t

q t

= t

q e

+ 1

k2⋅q2

e

where q t and q e (mg/g) are the amount of DCF per unit mass of the

adsorbent at time t (min) and at equilibrium, respectively, and k 2 is the

rate constant (g/mg min)

2.8 Flow-through extraction and preconcentration of diclofenac and

ketoprofen

The 3D printed device with integrated packing was connected to a

multi-syringe pump equipped with 5 and 10 mL glass syringes Syringe 1

contained an aqueous solution of a mixture of DCF and ketoprofen (1

ppm, each), and Syringe 2 contained methanol First, 50 mL of a solution

of the pharmaceutical products were automatically circulated through

the column to preconcentrate them After that, the retained compounds

were eluted by running 2 mL of methanol through the column The

output liquid was analysed by HPLC for the simultaneous determination

of enrichment factors of both pharmaceuticals, DCF and ketoprofen

3 Results and discussion

3.1 Synthesis and characterization of MIL-100-Fe-AMSA

MIL-100-Fe precursor was prepared by a green microwave-assisted

synthesis, which allowed a significant decrease in the reaction time

compared to the solvothermal method [50] Then, using a simple pro-cedure, sulfonic-functionalized MIL-100 MOF (MIL-100-Fe-AMSA) was obtained by grafting aminomethanesulfonic acid onto the coor-dinatively unsaturated iron sites of MIL-100 Fig 1a shows the X-ray diffraction patterns of MIL-100-Fe before and after functionalization Both diffractograms show good crystallinity and matched well with those previously reported [51], indicating that the grafting process did not alter the structure of MIL-100-Fe

The textural properties of the materials were investigated by N2 adsorption-desorption measurements As shown in Fig 1b, the N2 iso-therms of the prepared MIL-100-Fe and MIL-100-Fe-AMSA are a com-bination of type I and IV isotherms with a significant N2 uptake at lower P/P0 values, suggesting that the obtained materials were mainly microporous Both materials exhibit a multimodal distribution with pores centered at around 10, 15 and 20 Å (inset of Fig 1b) The BET specific surface and total pore volume of the MIL-100-Fe material were

1245 m2/g and 0.77 cm3/g, respectively, which are comparable to those reported in the literature [52] In the case of MIL-100-Fe-AMSA, the values of surface area and the total pore volume decreased to 845 m2/g and 0.50 cm3/g, respectively, what could be attributed to the partial occupation of the pores of MIL-100-Fe by the aminomethanesulfonic acid molecules Similar results have been described in the literature for the functionalization of uncoordinated metal centers of MOFs with organic molecules [33,34]

The prepared materials were characterized by FTIR spectroscopy (Fig S1) The FTIR spectrum of the MIL-100-Fe shows bands at 1629,

1452, 1380, 760 and 711 cm− 1, which match well with those of MIL- 100-Fe MOF previously reported by other authors [53,54] The band

at 1629 cm− 1 is attributed to C–O stretching vibration of carboxylic groups, while the bands at 1452 and 1380 cm− 1 can be assigned to the symmetric and asymmetric vibration of the OCO group, respectively The last two peaks at 760 and 711 cm− 1 corresponds to the C–H vi-brations of benzene ring The MIL-100-Fe-AMSA sample exhibits addi-tional absorption bands at 1223 and 1152 cm− 1, which are assigned to the O––S––O asymmetric and symmetric stretching modes, respectively, and at 1041 that comes from the stretching mode of S–O [55,56], con-firming the incorporation of the sulfonic groups in the grafted sample The functionalization of MIL-100-Fe was also checked by infrared spectroscopy of adsorbed carbon monoxide at 100 K For that, after activation of the obtained materials, a saturation dose of CO was introduced into the IR cell and the corresponding spectra were regis-tered (Fig 1c) The IR spectrum of adsorbed CO on MIL-100-Fe shows an intense IR absorption band at 2170 cm− 1 that corresponds to the fundamental C–O stretching mode of carbon monoxide interacting (through the carbon atom) with coordinatively unsaturated iron cations

of MIL-100-Fe [57,58] The IR spectrum of the MIL-100-Fe-AMSA ex-hibits the IR absorption band at 2170 cm− 1, although much less intense, indicating a partial functionalization of the open metal sites with the sulfonic acid groups In both cases, the spectra show an additional weaker band at 2135 cm− 1, which, in agreement with the literature, is assigned to physisorbed CO [57] The incorporation of AMSA molecules into the MIL-100-Fe sample was corroborated by EDS analysis (Fig 1d),

in which a band at 2.31 KeV, corresponding to S (Kα) signal, was detected

To study the morphology of the obtained MOFs, they were charac-terized by scanning electron microscopy (Fig 2a and b) and trans-mission electron microscopy (Fig 2c and d) As can be seen in the micrographs, both materials are formed of agglomerates of particles with an average crystal size of about 400 nm and octahedral shaped morphology, indicating that both, the morphology and the particle size, remain unchanged after the functionalization process

3.2 Extraction of diclofenac under batch conditions

To evaluate the adsorption capacity of the sulfonic-functionalized MIL-100-Fe material as an adsorbent, diclofenac, one of the most

common pharmaceutical pollutants found in wastewater [59], was

chosen as model adsorption analyte Fig 3a shows the adsorption

iso-therms of DCF on MIL-100-Fe and MIL-100-Fe-AMSA recorded at room

temperature after 24 h of adsorption Langmuir model was used to fit the

experimental results (Fig 3b), obtaining, in both cases, good correlation

coefficients (R2 = 0.996–0.998), which confirms that this model is

suitable for describing the DCF adsorption on both MOFs samples

MIL-100-Fe-AMSA has a maximum adsorption capacity of DCF of 476 mg/g, which is higher than most of the values of adsorption capacity of DCF reported in the literature (Table S1) and was significantly better than that of the MIL-100-Fe (357 mg/g), demonstrating that the incor-poration of the sulfonic acid groups improves the adsorbent properties of the MOF

The adsorption rate is an important parameter to consider when

Fig 1 Characterization of MIL-100-Fe and MIL-100-Fe-AMSA samples: (a) XRD patterns, (b) N2 adsorption-desorption isotherms Inset: Pore size distribution, (c) FTIR spectra of CO adsorbed at 100 K, and (d) energy dispersive X-ray spectra

Fig 2 SEM images of (a) MIL-100-Fe and (b) MIL-100-Fe-AMSA samples TEM images of (c) MIL-100-Fe and (d) MIL-100-Fe-AMSA samples

designing adsorbents for the removal of pollutants, and can be assessed

by evaluating the effect of the contact time on the adsorption Fig 3c

shows the percentage of DCF adsorbed by MIL-100-Fe before and after

functionalization at different time intervals As can be observed, DCF

was extracted faster using the MIL-100-Fe-AMSA MOF, reaching after

only 4 min, a percentage of extraction higher than 80%, showing the

remarkable fast uptake of DCF by this material The adsorption kinetic

data were analysed using a pseudo-second-order kinetic model (Fig 3d)

In both cases, correlation coefficients of 0.999 were obtained, indicating

that the experimental data are well described by this model

To gain a better understanding of the DCF adsorption efficiency of

MIL-100-Fe-AMSA, the possible interactions involved during the

extraction process were studied For that, since the protonation/

desprotonation of adsorbates and the surface charges of adsorbents

de-pends on the solution pH, DCF adsorption over MIL-100-Fe-AMSA was

carried out in a wide pH range (4.5–10.5) As shown in Fig 4a, the

extraction capacity of MIL-100-Fe-AMSA was hardly affected by the pH

of the solution and only a slight decrease of 8% was observed in the

adsorption capacity when the pH changes from 4.5 to 10.5 Considering

the isoelectric point of MIL-100-Fe-AMSA (Fig 4b) and the pKa of DCF

(4.2) [60], this decrease could be due to the electrostatic repulsion

be-tween the negatively charged surface of the MIL-100-Fe-AMSA, that

becomes more negative as the pH increases, and the DCF molecules, which are negatively charged over the pH range studied However, the small variation of the DCF adsorption on MIL-100-Fe with the pH sug-gests that the electrostatic interactions are not significant in the extraction process So the superior extraction capacity of MIL-100-Fe-AMSA can be due by the synergistic effect of H-bonding and

π-π interactions As DCF has hydrogen bond donor atoms (− NH group) and the sulfonic acid group of the MIL-100-Fe-AMSA, which is ionized in the pH range studied, can act as hydrogen bond acceptor, strong inter-molecular hydrogen bonds can be established between them [61] In order to confirm this interaction, FTIR analysis was carried out (Fig S2) The FTIR spectrum of MIL-100-Fe-AMSA after DCF adsorption shows a shift of the stretching vibration of sulfonic group, which, in agreement with the literature, proves the interaction between the sulfonic groups and DCF molecules [30,62] Accordingly, after washing and removing the adsorbed DCF, the original MIL-100-Fe-AMSA spectrum is recov-ered On the other hand, the adsorption of DCF over MIL-101-Fe-AMSA can also be facilitated by the π− π interactions between the benzene rings

of both DCF and the skeleton of MIL-100-Fe-AMSA [28,63] The sug-gested mechanism for DCF adsorption on MIL-100-Fe-AMSA is shown in Fig 5

To evaluate the reusability of MIL-100-Fe-AMSA in the adsorption

Fig 3 DCF adsorption isotherms (a), and corresponding Langmuir plots (b) of MIL-100-Fe and MIL-100-Fe-AMSA (c) Kinetic adsorption data (c) and corresponding

linear fit of pseudo-second order kinetics model (d) for the adsorption of DCF (100 mg/L) on MIL-100-Fe and MIL-100-Fe-AMSA

Fig 4 (a) Effect of pH of solution on the extraction of DCF over MIL-100-Fe-AMSA (b) Zeta potential of the MIL-100-Fe-AMSA at different pH values

removal of the DCF, its recyclability was tested by doing five

consecu-tives adsorption-desorption cycles As can be seen in Fig 6a, after the

five cycles, the extraction capacity of the material exceeded 93% in both

cases, without its structure and iron content being affected (Fig 6b and

Fig S3), which demonstrates the excellent recyclability of the prepared

MIL-100-Fe-AMSA In addition, the leaching of iron ions into the water,

after the extraction of DCF, was negligible, corroborating the stability of

MIL-100-Fe-AMSA

3.3 MIL-100-Fe-AMSA/3D device for the enrichment of pharmaceuticals

In order to facilitate and improve the applicability of the MIL-100-Fe-

AMSA for pollutant extraction from water, the material was immobilized

into a 3D printed device by a simple and fast coating method Basically, a

MIL-100-Fe-AMSA/PVDF ink was prepared and incorporated to the 3d

printed column obtaining a functional device (Fig 7)

To exemplify the application of the developed MIL-100-Fe-AMSA/3D

column, it was tested for the simultaneous adsorption and enrichment of

DCF and ketoprofen from water Fig 8 shows the chromatograms of

standard solution of the two pharmaceutical products (1 mg/L, each)

before and after solid-phase extraction with the MIL-100-Fe-AMSA/3D

column It can be observed that the signals corresponding to both

pol-lutants in the direct analysis are very weak, however, after

preconcen-tration with the MIL-100-Fe-AMSA/3D column and using 2 mL of

methanol as eluent, these signals significantly increase, reaching

Fig 5 Proposed adsorption mechanism for DCF removal using MIL-100-Fe-AMSA

Fig 6 (a) Recyclability of MIL-100-Fe-AMSA for the adsorption of DCF from water (b) X-ray diffraction patterns of MIL-100-Fe-AMSA before and after

DCF extraction

Fig 7 Schematic representation of the preparation of the MIL-100-Fe-AMSA/

3D column with integrated packing based on interconnected cubes

enrichment factors of 17 and 9 for DCF and ketoprofen, respectively The

obtained results demonstrate the suitability of the MIL-100-Fe-AMSA/

3D device for the adsorption and preconcentration of pharmaceuticals

pollutants from water

4 Conclusions

In this study, the use of sulfonic-functionalized MIL-100-Fe metal-

organic framework (MIL-100-Fe-AMSA) as sorbent for the removal of

diclofenac has been explored for the first time The MIL-100-Fe-AMSA

was prepared by grafting the coordinatively unsaturated iron sites of

MIL-100-Fe with aminomethanesulfonic acid, obtaining a functional

adsorbent with high surface area The developed material showed fast

uptake (>80% of extraction after only 4 min), high reusability and

excellent adsorption capacity of 476 mg/g, which is higher than that of

the MIL-100-Fe, confirming the role of the sulfonic groups on the

extraction process Adsorption mechanism analysis indicated that

elec-trostatic interactions between DCF and MIL-100-Fe-AMSA were not

significant in the removal of DCF, and synergistic effect of H-bonding

and π− π interactions was suggested to be the main mechanism for

explaining the improved efficiency of the MIL-100-Fe-AMSA The

ob-tained MIL-100-Fe-AMSA was used for the preparation of a functional

device (MIL-100-Fe-AMSA/3D column), which showed high efficiency

for the simultaneous extraction and preconcentration of DCF and

keto-profen, making it a promising device for the analysis of low levels of

emerging pollutants from water

CRediT authorship contribution statement

Neus Crespí S´anchez: Writing – original draft, Visualization,

Methodology, Investigation Gemma Turnes Palomino: Writing –

re-view & editing, Writing – original draft, Supervision, Funding

acquisi-tion Carlos Palomino Cabello: Writing – review & editing, Writing –

original draft, Visualization, Supervision

Declaration of competing interest

The authors declare that they have no known competing financial

interests or personal relationships that could have appeared to influence

the work reported in this paper

Data availability

Data will be made available on request

Acknowledgements

N Crespí acknowledges the support from the Spanish Ministerio de Educaci´on y Ciencia (FPU pre-doctoral fellowship) Financial support from the Spanish Ministerio de Ciencia e Innovaci´on and Agencia Estatal

de Investigaci´on (project PID2019-107604RB-I00/MCIN/AEI/ 10.13039/501100011033) is gratefully acknowledged

Appendix A Supplementary data

Supplementary data to this article can be found online at https://doi org/10.1016/j.micromeso.2022.112398

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