Adsorption Behavior and Mechanism of Sulfonamide Antibiotics in

Article Cite This: J. Chem. Eng. Data XXXX, XXX, XXX−XXX

pubs.acs.org/jced

Adsorption Behavior and Mechanism of Sulfonamide Antibiotics in Aqueous Solution on a Novel MIL-101(Cr)@GO Composite Xiuna Jia,† Sijia Li,† Yudan Wang,† Ting Wang,*,‡ and Xiaohong Hou*,‡ †

School of Pharmacy and ‡School of Pharmaceutical Engineering, Shenyang Pharmaceutical University, Shenyang Liaoning Province, P. R. China

Downloaded via WASHINGTON UNIV on March 2, 2019 at 05:03:16 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

S Supporting Information *

ABSTRACT: The occurrence of numerous antibiotics, such as sulfonamides (SAs), in environmental water has recently heightened concerns in consideration of their potential threat to human health and aquatic ecosystems. The removal of pharmaceuticals by adsorption comprises some of the most promising techniques because of their easy regeneration, low cost, and high efficiency. In this work, MIL-101(Cr)@GO, with a high surface area, was synthesized. Its adsorption properties toward three SAs were examined in batch adsorption experiments to probe the underlying factors of adsorption behavior and the mechanism for the first time. The pronounced factors that influenced the adsorption and removal process were investigated. The adsorption kinetics and isotherms were studied in order to characterize the operation. The adsorption kinetics demonstrated that the adsorption process would match the pseudo-second-order kinetic model. Furthermore, the adsorption was spontaneous, entropy was decreased, and the process was exothermic, and the equilibrium data was more appropriate described by the Freundlich isotherm model. Moreover, the adsorption−desorption of MIL-101(Cr)@GO could be consecutively cycled at least five times. MIL-101(Cr)@GO exhibited remarkable removal efficiency compared to MIL-100(Fe), MIL-101(Cr), and other adsorbents. These results demonstrated that MIL-101(Cr)@GO would be a promising adsorbent for the removal of sulfonamides from water samples and even for environmental protection.

1. INTRODUCTION During the past decade, concern about the occurrence and fate of pharmaceuticals in aquatic environments has been on the increase throughout the world.1−3 Though the pharmaceuticals are present at low concentration (ng L−1 or μg L−1) in natural water,4 there is much information about the potential effects on living organisms.5 For instance, sulfonamides (SAs) are a class of synthetic antimicrobials and have frequently been used in human medicine as well as cattle farming.6,7 The three representative sulfonamides, sulfadiazine (SDZ), sulfamethoxazole (SMX), and sulfadoxine (SDX), are commonly used antibiotics in veterinary practice to promote the growth of livestock and to prevent and treat bacterial infections at lower cost.8,9 As a result, the increasing contamination of SAs not only deteriorates the quality of environmental water but also has an unpredictable influence on human health because of its hypersensitive allergic reaction, drug-resistance problem, and even carcinogenic character.10 Therefore, the removal of SAs from wastewater is of great significance to the safety of water environments and the protection of human health.11,12 Nowadays, a variety of physiochemical techniques have been developed to remove or destroy antibiotics from water sources, including oxidation,13 reverse osmosis,14 ion exchange,15 and adsorption.16 Among these methods, adsorption is regarded as © XXXX American Chemical Society

one of the most effective technologies because of its wide application scope, excellent treatment effect, and capacity to recover valuable products and raw materials.17,18 More importantly, it would not cause secondary pollution.19 However, the core of the practical application of adsorption technology is to find efficient solid sorbent materials. Metal−organic frameworks (MOFs), an extensive class of crystal porous materials, were first introduced by Yaghi and his co-worker20,21 and were formed by the self-assembly between metal ions and organic ligands.22 Recently, they have attracted considerable attention for their potential applications in pharmaceutical adsorption as a result of their ultrahigh porosity, regular porous structures, manipulative pore sizes, and chemical functionalities via the modification of metal groups or organic linkers.23−25 These unique characteristics make them promising materials in gas storage,26 adsorption/ separation,27 and drug delivery.28 Among countless MOFs reported so far, MIL-101(Cr) (MIL, Matérial Institut Lavoisier) is one of the most prominent sorbents owing to its superior features, such as Received: December 2, 2018 Accepted: February 22, 2019

A

DOI: 10.1021/acs.jced.8b01152 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

Figure 1. Chemical structures, molecular weight, and pKa values of the target sulfonamides.

more excellent chemical stability and inexpensiveness.29,30 However, it has an inherent problem of providing fewer dispersive forces to bind small molecules as a result of their low density of atoms in structures.31 That is to say, the combination of adsorbent with other substrates could not only improve the adsorbent’s atomic density but also further boost its adsorption properties. In this sense, graphite oxide (GO) would be an excellent prospect as a mixed substrate owing to its dense arrays of atoms and its rich epoxy functional groups in the plane surface of each sheet coupled with carboxyl groups on the edges.32,33 The novel structure of GO would enhance the dispersive forces and increase the porosity of the materials by “incorporation” in the composites. These functional groups also offer the possibility to form hydrogen bonds and electrostatic interactions with organic compounds or metal ions. For instance, Bandosz and his colleagues synthesized composites of MOFs such as MOF-5@GO34 and HKUST-1@GO (HKUST, Hong Kong University of Science and Technology)35 and then tested their properties for the adsorption of small gas molecules (NH3, H2S, and NO2). The results showed that compared to their parent MOFs both the dispersive forces and porosities of these composites were enhanced; consequently, their adsorption capacities for these toxic gases were significantly improved. Kumar et al.36 prepared hybrid nanocomposites based on graphene oxide and ZIF-8 (ZIF, Zeolitic Imidazolate Frameworks) and reported GO to be a structure-oriented agent for the growth of nanocrystals of ZIF-8 due to the coordination modulation effect, and the CO2 adsorption properties of ZIF-8/GO increased compared to those of ZIF-8. It is worth mentioning that Ahmed et al.37 synthesized the MIL-101(Cr)@GO composites, which had not only a larger surface area but also a higher nitrogen-containing compound adsorption capacity compared to that of virgin MIL-101(Cr). Therefore, it is rationalized to expect an excellent adsorption performance from this new composite material for SAs. To our knowledge, there has not yet been such a report. Therefore, it is reasonable to explore the adsorption behavior of MIL-101(Cr)@GO toward SAs. Herein, the adsorption mechanism and performance of the novel composite MIL-101(Cr)@GO for SAs was investigated for the first time. The objective of this work is to prepare MIL101(Cr)@GO by a modified simple hydrothermal method and to characterize its chemical performance and physical structure. The adsorption conditions of SDZ, SMX, and SDX on MIL101(Cr)@GO and the adsorption isotherms and adsorption kinetics were assessed by means of a batch equilibrium method. Finally, adsorption and desorption were performed to study the recycling and reusability of SAs adsorption on MIL101(Cr)@GO. The explorative research indicated that MIL101(Cr)@GO has the potential to quickly remove SAs from contaminated water. The effects of SA properties on the adsorption of MIL-101(Cr)@GO would be discussed and reported here.

2. EXPERIMENTAL SECTION 2.1. Reagents and Materials. Terephthalic acid (H2 BDC), chromium nitrate nonahydrate (Cr(NO3 ) 3 · 9H2O), and hydrofluoric acid (HF) were supplied by the Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). Graphite powder was purchased from Shanghai Aladdin Chemistry Co., Ltd. (Shanghai, China). Sodium nitrate (NaNO3), potassium permanganate (KMnO4), ethanol, N,Ndimethylformamide, and H2O2 (30%) were purchased from Kermel Chemical Reagent Co., Ltd. (Tianjin, China). Concentrated nitric acid (HNO3), sodium chloride (NaCl), concentrated sulfuric acid (H2SO4), sodium hydroxide (NaOH), hydrochloric acid (HCl), and activated carbon were obtained from Damao Chemical Reagent Factory (Tianjin, China). All solvents and reactants above were of analytical grade. The MIL-101(Cr) and MIL-100(Fe) materials have been previously synthesized and characterized in our laboratory, and detailed descriptions are given in the Supporting Information (SI). The standards of SAs, including sulfadiazine (SDZ, 99.88%), sulfadoxine (SDX, 99.08%), and sulfamethoxazole (SMX, 99.87%), were obtained from Shanghai Aladdin Chemistry Co., Ltd. (Shanghai, China). The chemical structures and the pKa values of the target SAs are shown in Figure 1. 2.2. Synthesis and Characterization of GO and MIL101(Cr)@GO. Graphite oxide (GO) was synthesized from expandable graphite power according to the modified Hummers method.38 Composite material MIL-101(Cr)@GO was prepared using a hydrothermal method.39 The specific process of synthesis, purification, and characterization of GO and MIL-101@GO is described in the SI. Prepared MIL101(Cr)@GO was directly ultrasonicated in a methanol bath for 10 min, dried overnight under vacuum at 80 °C, and kept in a desiccator. Then it was used for further characterization and experiments. 2.3. Adsorption Experiments. Stock solutions (1 mg mL−1) were prepared separately for three SAs by dissolving them in chromatographic-grade methanol and were stored at 4 °C in darkness. Working solutions were prepared through sequential dilution of the stock solution with purified water. In addition, the calibration curves (Table S1) were obtained from the absorbance in the concentration range from 10 to 50 mg L−1. In all batch experiments, the SDZ, SMX, and SDX concentrations were measured with a Shimadzu UV-2450 UV−visible spectrophotometer (Kyoto, Japan) at 265, 270, and 278 nm, respectively (Figure S3). The adsorption efficiency was assessed by the batch experiments carried out as follows: an exact amount of the MIL-101(Cr)@GO composite (50 mg) was added to the SAs solutions (50 mL) in the concentration ranging from 10 to 50 mg L−1. The pH of the solution was adjusted to 5. The conical flasks were fixed on an HZQ-C temperature-controlled air bath oscillator (Harbin Dongming Ltd., China) under the condition of 298 K at 150 rpm for a period of 2 h. The MIL-101(Cr)@ B



Article

Figure 2. (A) Comparison of the XRD pattern of synthesized MIL-101(Cr)@GO with that of previously reported simulated MIL-101(Cr). (B) XRD pattern of synthesized GO. (C) SEM image of synthesized GO. (D) SEM image of synthesized MIL-101(Cr)@GO. (E) Comparison of the TGA curve of synthesized MIL-101(Cr)@GO with that of MIL-101(Cr). (F) Comparison of the N2 adsorption−desorption isotherms of synthesized MIL-101(Cr)@GO with MIL-101(Cr).

GO was then separated from the solution via centrifugation at 12 000 rpm for 5 min, and the equilibrium concentration of SAs versus contact time was measured at the maximum absorption wavelength. Regeneration tests were conducted by washing the composite several times with methanol and deionized water to remove SAs, which were dried and reused for the next adsorption. To achieve favorable adsorption conditions, a series of extraction parameters, including the types of materials, pH of the water, adsorbent dosage, salt content, and initial concentration, were investigated. The equilibrium adsorption capacity Qe (mg g−1) and the removal efficiency were calculated with the following equations Qe =

(C0 − Ce)V m

removal (%) =

(C0 − Ce)100 % C0

(2)

where C0 (mg L−1) and Ce (mg L−1) are the initial and the equilibrium concentrations of the SAs, respectively; V (L) is the volume of the SA solution; and m (g) is the mass of adsorbent. For the adsorption kinetics experiments, a certain amount of MIL-101(Cr)@GO (30 mg for SDZ, 40 mg for SMX and SDX) was placed in 50 mL of SA solution having definite concentrations from 10 to 50 mg L−1 at pH 5. In a fixed time interval, the rest of the concentrations of the sulfonamides were measured. Furthermore, the adsorption isotherms were determined in the uniform system, and the concentrations of

(1) C



Article

the sulfonamides were measured after merely 2 h of adsorption.

3. RESULTS AND DISCUSSION 3.1. Characterization of GO and MIL-101(Cr)@GO. The surface morphology and structure of prepared GO and MIL101(Cr)@GO were evaluated via XRD, TGA, SEM, and N2 adsorption−desorption experiments (Figure 2). It is evident from Figure 2A that the powder XRD pattern of the produced MIL-101(Cr)@GO was nearly the same as that of MIL101(Cr) that was previously reported.40 The XRD pattern implied that the MIL-101(Cr)@GO preserved the crystalline character of the parental MIL-101(Cr). In Figure 2B, the diffraction peak of GO at about 10′ ensured that GO was successfully synthesized. The surface morphology of the prepared MIL-101(Cr)@GO and GO were characterized by SEM. In Figure 2C, a sheetlike surface of GO is clearly seen. Figure 2D indicates that the MIL-101(Cr) nanoparticles were homogeneously stacked on the layered structure of GO. This morphology further indicates that MIL-101(Cr)@GO was successfully synthesized. In addition, TGA determined the thermal stability of the prepared materials. Figure 2E shows the TGA curves of MIL-101(Cr)@GO and MIL-101(Cr). As can be seen, the TGA curve of MIL-101(Cr)@GO was very similar to that of MIL-101(Cr): both of them had a weight-loss step at about 400 °C, which was due to the missing OH/F groups, resulting in the breaking down of MIL-101(Cr) or the collapse of the frameworks. As described in Figure 2F and Figure S5, MIL-101(Cr)@GO gave a larger BET surface area (3351.64 m2 g−1) as well as a larger total pore volume of 2.2756 cm3 g−1 than did MIL-101(Cr) (BET surface area 3311.88 m2 g−1, pore volume 1.5732 cm3 g−1). The TGA and N2 sorption− desorption test demonstrated that MIL-101(Cr)@GO has excellent properties of stability and adsorptivity. 3.2. Adsorption Properties. 3.2.1. pH Responsiveness. The pH of the solution is one of the most pronounced parameters influencing the adsorption of the SAs by influencing the existing states of the adsorbates as well as the surface binding sites of the used adsorbent. Considering the instability of MIL-101(Cr)@GO in highly alkaline aqueous solutions, the pH values of the sample solution were examined in the range of 3−9. Excess MIL-101(Cr)@GO was placed into 50 mL of SA liquor, which was adjusted to the appropriate pH value by NaOH (0.1 M) or HCl (0.1 M) solution. The results are shown in Figure 3. The highest removal efficiency was obtained at pH 5. It is known that the pKa of the three SAs varies from 5.60 to 6.52, and the SAs were mainly in the form of a molecular state when the pH of the solution was less than the pKa, that is, approximately 5.0. At this pH, the material is positively charged, and Figure S6 shows the plots. The point of zero charge (PZC) of MIL-101(Cr)@GO is 7.18. When the pH value of the solution was lower than the PZC 7.18 of the material, the adsorbent surface has a positive charge. And the main adsorption forces are coordination bonds, intermolecular hydrogen bonds, π−π interaction, and the hydrophobic effects. When the pH value was larger than 5, the SAs would lose their protons gradually so that their hydrophilicity was strongly weakened. Under such alkaline conditions, many electron-rich hydroxyl groups would be adsorbed on the unsaturated Cr(III) sites of MIL-101(Cr)@GO, and the adsorption ability of the analytes would be obviously decreased. As a result, the following experiments were carried out at pH 5.

Figure 3. Effect of solution pH on sulfonamide adsorption by the MIL-101(Cr)@GO composite.

3.2.2. Effect of Mass of Adsorbent. The amount of MIL101(Cr)@GO in the range of 10 to 50 mg at an interval of 10 mg was evaluated under the same experimental conditions. As shown in Figure 4, in the initial stage of the adsorption

Figure 4. Effect of the different masses of MIL-101(Cr)@GO.

reaction, the sulfonamide can be freely combined with the adsorbent as a result of the large number of active sites on the surface of the adsorbent, and the removal rates of SAs rapidly increased with the increase in the adsorption mass. However, as the active site is gradually occupied by the SAs, and the adsorbate adsorbed on the material and the adsorbate in the solution generates a repulsive force. The remaining vacancies of the adsorbent are difficult to occupy, and then the removal remained nearly constant. It proved that for the sulfonamide solution with a fixed concentration, 30 mg of sorbent for SDX and 40 mg of sorbent for SDZ and SMX could provide sufficient surface area and sufficient adsorption sites. Consequently, 30 mg for SDX and 40 mg for SDZ and SMX were reasonable adsorbent dosages to ensure satisfactory results in the following experiments. 3.2.3. Effect of Salt Content. The ionic strength was investigated by spiking NaCl in the concentration range from 0 to 1 mol L−1 while other conditions remained constant. Figure 5 showed that the removal efficiencies of all analytes gradually decreased with the increase in NaCl concentration. As the D



Article

investigated, and Figure S7 shows the plots. The adsorption was very fast, and the curves maintained the uniform trend with different initial concentrations of SAs. Most of the adsorbates’ uptake was completed during the first 10 min, and equilibrium was gradually reached in 60 min, implying that the MIL-101(Cr)@GO composite possessed both high adsorption ability and superior removal efficiency toward SAs in water. Hence, to achieve the highest adsorption, 2 h was selected to be a reasonable time in the following experiments. Three classical models were utilized to examine the adsorptive interaction pathways, the rate of SAs removal, and the control step of the overall adsorption process. The generated plots of the SAs adsorptions at the initial concentrations of 10−50 mg L−1 are shown in Figure S8. The pseudo-first-order model, describing the adsorption rate based on the adsorption capacity, proposed by Lagergren can be expressed as follows

Figure 5. Effect of salt content on sulfonamide removal.

density and the viscosity of the liquor increased with the addition of salt, the mass transfer of the analytes to the sorbent was hampered. It can also be speculated that the addition of salt would reduce the solubility of the target compounds and even lead to a salting-out effect. Moreover, another conjecture was that the electrostatic interaction would be another mechanism for the adsorption of SAs on MIL-101(Cr)@GO. As a consequence, none of NaCl was assigned to subsequent experiments. 3.2.4. Reuse of MIL-101@GO. The reversible adsorption on composite MIL-101@GO is one of the most important parameters regarding evaluating the applications in industry and may reduce the overall cost of the adsorbent. In this work, five consecutive cycles of adsorption−desorption on the composite under optimized conditions were performed. Figure 6 demonstrated that MIL-101(Cr)@GO was stable and

log(qe − qt ) = log qe −

k1 t 2.303

(3)

where qe and qt (mg g−1) are the adsorption capacities at equilibrium and any time t (min), respectively, and k1 (g mg−1 min−1) is the pseudo-first-order rate constant. Kinetic parameters qe and k1 were calculated from the intercept and the slope of the plot of log(qe − qt) against t (shown in Table 1). The pseudo-second-order model in linear form is written as t 1 1 = + t qt qe k 2qe 2

(4)

where k2 (g mg−1 min−1) is the second-order rate constant. A plot of t/qt versus t provides second-order adsorption rate constants k2 and qe values from the intercepts and the slopes, respectively. The parameters are listed in Table 1. The intraparticle diffusion model can be expressed by eq 5 qt = kit 1/2 + c −1

(5) 1/2

where ki (mg g min ) is the intraparticle diffusion rate constant and c (mg g−1) is a constant revealing the thickness of the boundary layer. The plot was generated by plotting qt versus t1/2, and the results are listed in Table 1. The data in Table 1 clearly shows that compared to the pseudo-first-order kinetic model (0.8716−0.9976) and the intraparticle diffusion model (0.3666−0.5293), the pseudosecond-order kinetic model (0.9991−1.0000) has the highest correlation coefficient. In addition, the values of experimental Qe,exp were consistent with the calculated qe (qe,cal) based on the second-order model. Therefore, it is concluded that the adsorption mechanisms of SAs on MIL-101(Cr)@GO abided by the pseudo-second-order kinetic model. This results also implied that the chemisorptions may be the rate-limiting step, which further suggested that MIL-101(Cr)@GO had excellent kinetic properties for SAs. 3.2.6. Adsorption Isotherm Study. Some well-known isotherm models, Freundlich, Langmuir, and Dubinin− Radushkevich (D−R), were selected to fit the experimental data. The models are expressed in eqs 6, 7, and 9. The adsorption isotherm plots are shown in Figure 7. All calculated results of the adsorption experiment are listed in Table 2. The Freundlich isotherm presupposes that adsorption is multilayered. The empirical equation is represented as follows

Figure 6. Reuse of MIL-101(Cr)@GO on adsorption of SDZ, SDX, and SMX (50 mg L−1, T = 298 K). Parts 1−5 represent the number of consecutive cycles of adsorption−desorption on MIL-101(Cr)@GO.

reusable during five consecutive cycles without any dramatic loss of capacity and a decrease in the removal efficiency for the target SAs. It was clearly visible that the SA removal efficiency is still above 95% for the first removal after five cycles, showing a high removal capacity and robust cycling performance. 3.2.5. Adsorption Kinetics Study. To understand the adsorption kinetics, the effect of contact time on the adsorption of SAs onto MIL-101(Cr)@GO was first E



Article

Table 1. Kinetic Models and Parameters for SMX, SDZ, and SDX Adsorption onto MIL-101(Cr)@GO pseudo-first-order kinetic analyte SMX

SDZ

SDX

C0 (mg L−1)

qe,exp (mg g−1)

k1 (min−1)

qe,cal (mg g−1)

10 20 30 40 50 10 20 30 40 50 10 20 30 40 50

13.17 21.78 29.72 39.07 47.25 13.98 24.12 36.30 45.42 58.57 13.78 26.18 39.32 50.07 58.99

0.7195 0.9175 1.0573 1.0734 1.1667 0.5430 0.7259 0.8848 1.0474 0.9150 0.5196 0.6250 0.7975 0.8314 0.8818

2.82 6.78 13.54 27.02 38.42 0.95 2.23 14.53 35.95 48.48 1.93 6.98 15.49 19.16 28.39

pseudo-second-order kinetic R2

k2

(g mg−1 min−1)

qe,cal (mg g−1)

0.8716 0.9939 0.9861 0.9900 0.9894 0.9714 0.9839 0.9976 0.9248 0.9263 0.9937 0.9916 0.9841 0.9914 0.9906

0.0948 0.0842 0.0358 0.0195 0.0166 0.2064 0.1308 0.0250 0.0152 0.0083 0.0934 0.0318 0.0210 0.0182 0.0134

13.28 21.93 30.03 39.53 47.25 14.01 24.15 36.63 46.08 59.52 13.85 26.46 39.68 50.51 59.52

intraparticle kinetic R2

kp (mg g−1 min1/2)

b

R2

0.9997 0.9998 0.9995 1.0000 0.9995 1.0000 1.0000 0.9997 0.9995 0.9991 0.9999 0.9998 0.9997 0.9997 0.9996

1.2432 2.0146 2.9535 3.8814 4.4089 1.2063 2.0885 3.4841 4.4236 5.8808 1.2377 2.4462 3.7203 4.7136 5.6777

5.5537 9.5291 12.3777 15.4399 18.1131 6.6403 11.4465 14.7768 17.8545 21.3840 6.1421 10.9640 16.1969 20.7616 23.7413

0.4432 0.4216 0.4684 0.4921 0.4795 0.3666 0.3683 0.4673 0.4882 0.5293 0.4074 0.4474 0.4592 0.4542 0.4741

Figure 7. Adsorption isotherms of SDZ, SDX, and SMX at 298 K.

Table 2. Isotherm Parameters for SDZ, SMX, and SDX Adsorption onto MIL-101(Cr)@GO Langmuir

Freundlich

Dubinin−Radushkevich

analyte

Qm (mg g−1)

KL (L mg−1)

R2

K (mg g−1 (L mg−1)1/n)

n

R2

Qm (mg g−1)

K (kJ2 mol2)

E (kJ mol−1)

R2

SMX SDZ SDX

101.01 135.14 119.05

0.2836 0.1979 0.4330

0.9900 0.9821 0.9761

21.5678 21.9354 34.0558

1.4043 1.3488 1.4081

0.9977 0.9927 0.9987

43.28 50.95 54.25

0.180 0.220 0.103

1.6667 1.5076 2.2033

0.9376 0.9094 0.9343

qe = KFCe1/ n

(6)

qe =

where KF and 1/n represent the Freundlich constants corresponding to the adsorption capacity and the adsorption intensity, and the values of 1/n and KF can be determined from the slope and intercept of the linear plot of ln qe against ln Ce. As shown in Table 2, the Freundlich model was more suitable for describing the adsorption isotherms. In addition, the linear correlation coefficients for SDZ, SMX, and SDX were 0.9927, 0.9977, and 0.9987, respectively, indicating that the adsorptions were typical multilayer adsorptions. Furthermore, the Freundlich constants n were found to be greater than 1, which demonstrated that the adsorption intensity would be favorable in this research and suggested that the MIL-101(Cr) @GO composites possessed heterogeneous surfaces. The Langmuir adsorption isotherm model assumes that adsorption occurs at specific homogeneous and slippery sites within the adsorbent by monolayer adsorption without any interaction between adsorbed targets.41 The Langmuir equation is given as eq 7

Q mKLCe 1 + KLCe

(7)

where qe (mg g−1) is the quantity of SAs adsorbed per unit of adsorbent, Qm (mg g−1) is the maximum amount of adsorption which completes monolayer coverage on the adsorbent surface, KL (L g−1) is the Langmuir equilibrium constant including the affinity of binding sites, and Ce (mg g−1) is the equilibrium concentration of the SAs in solution. Table 2 lists the adsorption parameters. The maximum adsorption capacity (Qm) of SAs was calculated to be 135.14 mg g−1 for SDZ, 101.01 mg g−1 for SMX, and 119.05 mg g−1 for SDX, respectively, indicating that the MIL-101(Cr)@GO composite had quite high adsorption capacities for three SAs. However, it can be easily determined that the adsorption capacity of MIL-101(Cr)@GO for SAs followed the order SDZ > SDX > SMX. Although these differences are a bit small, according to the structural formula of three SAs analyzed the molecular size of SDZ was the smallest, which might be owing to the lack of methoxy groups in the SDX structure or the F



Article

ΔS ΔH − (12) R RT where T (K) is the absolute temperature of the solution, R (8.314 J mol−1 K) is the universal gas constant, and K is the thermodynamic equilibrium constant of the adsorbent equal to Qe/Ce. The values of thermodynamic parameters and linear plots are presented in Table 3 and Figure S10. The negative values

methyl of the SMX structure. On the other hand, there are more oxygen and nitrogen atoms in the structure of SDX than in the structure of SMX because of pyrimidine and methoxy groups. The possible interactions of MIL-101(Cr)@GO toward SAs might be due to the coordination bonds and intermolecular hydrogen bonds, so the oxygen and nitrogen atoms in these chemical bonds would play an important role. In addition, the essential features of the Langmuir isotherm can be expressed in terms of a dimensionless constant RL, which was called the equilibrium parameter or separation factor.42 It can be expressed by eq 8 RL =

1 1 + KLC0

ln K =

Table 3. Thermodynamic Parameters for SDZ, SMX, and SDX Adsorption onto MIL-101(Cr)@GO

(8)

analyte

T (K)

ΔG (kJ mol−1)

ΔH (kJ mol−1)

SDZ

298 308 318 298 308 318 298 308 318

−30.41 −29.20 −27.99 −49.42 −47.17 −44.92 −26.24 −25.25 −24.27

−32.13 −33.21 −34.28 −56.32 −58.21 −60.09 −26.85 −27.75 −28.65

−1

where C0 (mg g ) is the initial SAs concentration and the parameter (RL) suggests the type of isotherm that is favorable at 0 < RL < 1. On the contrary, the adsorption process becomes unfavorable at RL > 1 or RL < 0. As shown in Figure S9, all of the RL values varied from 0.1979 to 0.4330, indicating that the adsorption behaviors were favorable. The D−R isotherm model also examined the equilibrium data with eq 9, which can judge the process as being chemical or physical qe = Q m exp−Kε

SDX

SMX

1 2K

(9)

(10)

We could judge the adsorption process to be a physical or chemical process according to the value of E. It can be seen from Table 2 that all of the E values were smaller than 8 kJ mol−1, indicating that the adsorption behavior belonged to a physical process. In addition, according to the pH dependence studies, it is rational to conjecture that the adsorption of MIL101(Cr)@GO toward three SAs would be possibly driven by interactions as follows: coordination bonds between −NH2 groups in the structures of sulfonamides and the open Cr(III) sites in MIL-101(Cr)@GO, the intermolecular hydrogen bonds between −COOH in MIL-101(Cr)@GO and −NH2 groups in the structures of sulfonamides, the hydrophobic effects and π−π interactions between phenyl rings of MIL101(Cr)@GO and the sulfonamide, and van der Waals interactions. All of these interactions jointly accelerate the adsorption process. Therefore, we can reasonable infer that both physical and chemical adsorption mechanisms would exist in adsorption.43 3.2.7. Adsorption Thermodynamics Study. To investigate the thermodynamic parameters, the adsorption experiments were also carried out at 298, 308, and 318 K, respectively. The Gibbs free energy44 is calculated with eq 11. The values of the enthalpy change (ΔH, kJ mol−1) and entropy change (ΔS, J mol−1 K−1) can be obtained from the van’t Hoff’s equation (eq 12) ΔG = −RT ln K

−13.00

−35.82

−8.11

of ΔG at various temperatures indicated that the adsorption process was spontaneous and feasible. Moreover, a close analysis of the data can be seen in which a reduction in the absolute value of ΔG is almost proportional to the increase in the temperature, and the lower temperature could be beneficial to the exothermic adsorption processes. The value of ΔH is negative, suggesting that the adsorption reactions were exothermic. The values of ΔS are negative, implying that the randomness gradually decreased at the solid/liquid interface over the course of the adsorption process, which should be a higher order of the interaction of the SAs with MIL-101(Cr)@ GO. Therefore, the enthalpy effect and the entropy effect at the same time drove the three SAs’ adsorption onto MIL101(Cr)@GO, whereas enthalpy effect played a more important role. As consequence, the adsorption of three SAs on MIL-101(Cr)@GO would be a spontaneous and exothermic process. 3.3. Comparison of MIL-101(Cr)@GO with Other Adsorbents for the Adsorption of SAs. In the present work, the same amounts of MIL-100(Fe), MIL-101(Cr), and powdered activated carbon sorbents were directly compared to the removal efficiency with MIL-101(Cr)@GO for SAs at 298 K. The experimental results are depicted in Figure 8. MIL101(Cr)@GO had a larger adsorption capacity for SDZ, SMX, and SDX than did the other three sorbents. This may be ascribed to the better water dispersion performance of the MIL-101(Cr)@GO structure compared to that of MIL101(Cr). Besides, MIL-101(Cr)@GO gave rise to a 2-foldhigher removal efficiency compared to that of MIL-100(Fe). The surface area of MIL-101(Cr)@GO obtained in the laboratory was 3351.64 m2 g−1, while that of MIL-100(Fe) was 1225.53 m2 g−1.45 In the case of the powdered activated carbon, the adsorption primarily depends only on the van der Waals interactions. In addition, it should be noted that the largest adsorption capacity of MIL-101(Cr)@GO toward SMX was 101.01 mg g−1, which was larger than those in the literature reported by using Fe3O4@C (C, carbon),46 high silica zeolite,47 MWCNT10 (MWCNT, magnetic multiwalled carbon nanotubes), and

2

where Qm (mol g−1) is the maximum monolayer adsorption capacity, qe (mol g−1) is the adsorption capacity at equilibrium, K (mol2 kJ−2) is the activity coefficient related to the adsorption mean free energy, and ε is the Polanyi potential. Furthermore, the values of the average free energy (E, kJ mol−1) can be obtained from eq 10:

E=

ΔS (J mol−1 K−1)

(11) G



Article

■

Figure 8. Comparison of the adsorption capacity of MIL-101(Cr)@ GO with different sorbent materials.

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. Tel: +86 13998830917.

aligned-MWCNT,48 strongly indicating that MIL-101(Cr)@ GO could be an excellent adsorbent for the adsorption and removal of the SAs (Table S2). It was a pity that there were bare reports in the literature regarding the adsorption performance of the reference materials for SDZ and SDX.

ORCID

Xiaohong Hou: 0000-0003-4210-9381 Notes

The authors declare no competing financial interest.

■

4. CONCLUSIONS In this article, novel MIL-101(Cr)@GO with both larger BET and enhanced adsorption ability for SAs compared to those of parent MIL-101(Cr) was successfully synthesized. After the optimization of the adsorption conditions, the adsorption behavior and mechanism of MIL-101(Cr)@GO toward SAs was thoroughly investigated. The kinetics of adsorption followed a pseudo-second-order model. Moreover, the Freundlich isotherm model yielded a better fit than the other two models for SAs adsorbed onto the composites. The maximum amounts of SDZ, SMX, and SDX adsorbed are 135.14, 101.01, and 119.05 mg g−1 at 298 K, respectively. Adsorption isotherms proved that the adsorption process included both physical and chemical adsorption. In addition, a thermodynamic study revealed that adsorption was spontaneous and exothermic and was a process of reduced randomness. Thereby, we can deduce that the driving forces of SAs on MIL-101(Cr)@GO were primarily due to coordination bonds, intermolecular hydrogen bonding, π−π interactions, and hydrophobic effects. The consecutive cycles of SA adsorption−desorption experiments indicated that MIL101(Cr)@GO had excellent regenerability and stability in performance. A high adsorption capacity and superior recycling performance for SAs make the composite MIL-101(Cr)@GO a promising adsorbent for industrial applications in the field of SA adsorption and environmental protection. Maybe we can anticipate that the composite MIL-101(Cr)@GO with excellent properties can also be used for the removal of other pharmaceuticals and pollutants for water treatment.

■

101(Cr)@GO, UV−vis spectrum of three sulfonamides, calibration curves of three sulfonamides, characterization of GO, total pore volume of the synthesized MIL101(Cr)@GO and MIL-101(Cr), effect of solution pH on the zeta potential of the MIL-101(Cr)@GO composite, effect of different initial concentration, adsorption kinetics plots for adsorption of sulfonamides on MIL-101(Cr)@GO, value of separation factor RL of MIL-101(Cr)@GO toward three sulfonamides, van’t Hoff plots to obtain ΔH and ΔS of MIL-101(Cr)@GO toward three sulfonamides, comparison of the maximum adsorption capacities for SMX adsorption on MIL101(Cr)@GO with other adsorbents, and references (PDF)

ACKNOWLEDGMENTS This work was financially supported by the Program for Liaoning Province Natural Science Foundation (201602693, 2016-2018), the Natural Science Foundation of Liaoning Provincial Department of Education (2017LQN12), and the Student’s Platform for Innovation and Entrepreneurship Training Plan of Shenyang Pharmaceutical University (201710163000120).

■

REFERENCES

(1) Rovani, S.; Censi, M. T.; Jr, P. S.; Lima, E. C.; Cataluña, R.; Fernandes, A. N. Development of a new adsorbent from agroindustrial waste and its potential use in endocrine disruptor compound removal. J. Hazard. Mater. 2014, 271, 311−320. (2) Rigobello, E. S.; Dantas, A. D.; Di, B. L.; Vieira, E. M. Removal of diclofenac by conventional drinking water treatment processes and granular activated carbon filtration. Chemosphere 2013, 92, 184−191. (3) Daughton, C. G.; Ternes, T. A. Pharmaceuticals and personal care products in the environment: agents of subtle change? Environ. Health Perspect. 1999, 107, 907−938. (4) Dutta, K.; Lee, M. Y.; Lai, W. W. P.; Lee, C. H.; Lin, A. Y. C.; Lin, C. F.; Lin, J. G. Removal of pharmaceuticals and organic matter from municipal wastewater using two-stage anaerobic fluidized membrane bioreactor. Bioresour. Technol. 2014, 165, 42−49. (5) Saucier, C.; Adebayo, M. A.; Lima, E. C.; Cataluña, R.; Thue, P. S.; Prola, L. D.; Puchana-Rosero, M. J.; Machado, F. M.; Pavan, F. A.; Dotto, G. L. Microwave-assisted activated carbon from cocoa shell as adsorbent for removal of sodium diclofenac and nimesulide from aqueous effluents. J. Hazard. Mater. 2015, 289, 18−27. (6) Eliopoulos, G. M.; Huovinen, P. Resistance to trimethoprimsulfamethoxazole. Clin. Infect. Dis. 2001, 32, 1608−1614. (7) Aguilararteaga, K.; Rodriguez, J. A.; Miranda, J. M.; Medina, J.; Barrado, E. Determination of non-steroidal anti-inflammatory drugs in wastewaters by magnetic matrix solid phase dispersion-HPLC. Talanta 2010, 80, 1152−1157. (8) Gentili, A.; Perret, D.; Marchese, S. Liquid chromatographytandem mass spectrometry for performing confirmatory analysis of veterinary drugs in animal-food products. TrAC, Trends Anal. Chem. 2005, 24, 704−733.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jced.8b01152. Synthesis of MIL-101(Cr), synthesis of MIL-100(Fe), characterization of MIL-101(Cr), characterization of MIL-100(Fe), synthesis of GO, synthesis of MILH



Article

(29) Lebedev, O. I.; Millange, F.; Serre, C.; Tendeloo, G. V.; Férey, G. First Direct Imaging of Giant Pores of the Metal−Organic Framework MIL-101. Chem. Mater. 2005, 17, 6525−6527. (30) Férey, G.; Mellot-Draznieks, C.; Serre, C.; Millange, F.; Dutour, J.; Surblé, S.; Margiolaki, I. A chromium terephthalate-based solid with unusually large pore volumes and surface area. Science 2005, 309, 2040−2042. (31) Petit, C.; Burress, J.; Bandosz, T. J. The synthesis and characterization of copper-based metal−organic framework/graphite oxide composites. Carbon 2011, 49, 563−572. (32) Petit, C.; Bandosz, T. J. MOF−Graphite Oxide Composites: Combining the Uniqueness of Graphene Layers and Metal−Organic Frameworks. Adv. Mater. 2009, 21, 4753−4757. (33) Bandosz, T. J.; Petit, C. MOF/graphite oxide hybrid materials: exploring the new concept of adsorbents and catalysts. Adsorption 2011, 17, 5−16. (34) Petit, C.; Bandosz, T. J. Exploring the coordination chemistry of MOF-graphite oxide composites and their applications as adsorbents. Dalton T 2012, 41, 4027−4035. (35) Li, L.; Liu, X. L.; Geng, H. Y.; Hu, B.; Song, G. W.; Xu, Z. S. A MOF/graphite oxide hybrid (MOF: HKUST-1) material for the adsorption of methylene blue from aqueous solution. J. Mater. Chem. A 2013, 1, 10292−10299. (36) Kumar, R.; Jayaramulu, K.; Maji, T. K.; Rao, C. N. Hybrid nanocomposites of ZIF-8 with graphene oxide exhibiting tunable morphology, significant CO2 uptake and other novel properties. Chem. Commun. 2013, 49, 4947−4949. (37) Ahmed, I.; Khan, N. A.; Jhung, S. H. Graphite oxide/metalorganic framework (MIL-101): remarkable performance in the adsorptive denitrogenation of model fuels. Inorg. Chem. 2013, 52, 14155−14161. (38) Hummers, W. S.; Offeman, R. E.; Hummers, W. S.; Offeman, R. E. Preparation of Graphitic Oxide. J. Am. Chem. Soc. 1958, 80, 1339−1339. (39) Sun, X. J.; Xia, Q. B.; Zhao, Z. X.; Li, Y. W.; Li, Z. Synthesis and adsorption performance of MIL-101(Cr)/graphite oxide composites with high capacities of n-hexane. Chem. Eng. J. 2014, 239, 226−232. (40) Férey, G.; Mellot-Draznieks, C.; Serre, C.; Millange, F.; Dutour, J.; Surblé, S.; Margiolaki, I. A chromium terephthalate-based solid with unusually large pore volumes and surface area. Science 2005, 309, 2040−2042. (41) Chatterjee, S.; Lee, D. S.; Lee, M. W.; Woo, S. H. Enhanced adsorption of congo red from aqueous solutions by chitosan hydrogel beads impregnated with cetyl trimethyl ammonium bromide. Bioresour. Technol. 2009, 100, 2803−2809. (42) Weber, T. W.; Chakravorti, R. K. PORE AND SOLID DIFFUSION MODELS FOR FIXED-BED ADSORBERS. AIChE J. 1974, 20, 228−238. (43) Wang, T.; Zhao, P.; Lu, N.; Chen, H. C.; Zhang, C. L.; Hou, X. H. Facile fabrication of Fe3O4/MIL-101(Cr) for effective removal of acid red 1 and orange G from aqueous solution. Chem. Eng. J. 2016, 295, 403−413. (44) Haque, E.; Lee, J. E.; Jang, I. T.; Hwang, Y. K.; Chang, J. S.; Jegal, J.; Jhung, S. H. Adsorptive removal of methyl orange from aqueous solution with metal-organic frameworks, porous chromiumbenzenedicarboxylates. J. Hazard. Mater. 2010, 181, 535−542. (45) Jia, X.; Zhao, P.; Ye, X.; Zhang, L.; Wang, T.; Chen, Q.; Hou, X. A novel metal-organic framework composite MIL-101(Cr)@GO as an efficient sorbent in dispersive micro-solid phase extraction coupling with UHPLC-MS/MS for the determination of sulfonamides in milk samples. Talanta 2017, 169, 227−238. (46) Bao, X.; Qiang, Z.; Chang, J.-H.; Ben, W.; Qu, J. Synthesis of carbon-coated magnetic nanocomposite (Fe3O4@C) and its application for sulfonamide antibiotics removal from water. J. Environ. Sci. 2014, 26, 962−969. (47) Fukahori, S.; Fujiwara, T.; Ito, R.; Funamizu, N. pH-Dependent adsorption of sulfa drugs on high silica zeolite: Modeling and kinetic study. Desalination 2011, 275, 237−242.

(9) Di Corcia, A.; Nazzari, M. Liquid chromatographic-mass spectrometric methods for analyzing antibiotic and antibacterial agents in animal food products. J. Chromatogr. A 2002, 974, 53−60. (10) Koesukwiwat, U.; Jayanta, S.; Leepipatpiboon, N. Validation of a liquid chromatography-mass spectrometry multi-residue method for the simultaneous determination of sulfonamides, tetracyclines, and pyrimethamine in milk. J. Chromatogr. A 2007, 1140, 147−156. (11) Liu, Z.; Wei, Y.; Zhang, H.; Gu, F.; Jin, X. Salting-out homogenous extraction followed by ionic liquid/ionic liquid liquidliquid micro-extraction for determination of sulfonamides in blood by high performance liquid chromatography. Talanta 2016, 161, 748− 754. (12) Dai, X.; Jia, X.; Pan, Z.; Wang, T.; Jian, W.; Huang, P.; Lu, H.; Hou, X. A combined experimental/computational study on metalorganic framework MIL-101(Cr) as a SPE sorbent for the determination of sulphonamides in environmental water samples coupling with UPLC-MS/MS. Talanta 2016, 154, 581−588. (13) Beltrán, F. J.; Aguinaco, A.; García-Araya, J. F.; Oropesa, A. Ozone and photocatalytic processes to remove the antibiotic sulfamethoxazole from water. Water Res. 2008, 42, 3799−3808. (14) Adams, C.; Asce, M.; Wang, Y.; Loftin, K.; Meyer, M. Removal of Antibiotics from Surface and Distilled Water in Conventional Water Treatment Processes. J. Environ. Eng. 2002, 128, 253−260. (15) Choi, K. J.; Son, H. J.; Kim, S. H. Ionic treatment for removal of sulfonamide and tetracycline classes of antibiotic. Sci. Total Environ. 2007, 387, 247−256. (16) Ternes, A. T.; Meisenheimer, M.; Mcdowell, D.; Frank, S.; Brauch, H.; Haistgulde, B.; Preuss, G.; Uwe Wilme, A.; Zuleiseibert, N. Removal of Pharmaceuticals during Drinking Water Treatment. Environ. Sci. Technol. 2002, 36, 3855−3863. (17) Basnet, P.; Zhao, Y. Superior dye adsorption capacity of amorphous WO3 sub-micrometer rods fabricated by glancing angle deposition. J. Mater. Chem. A 2014, 2, 911−914. (18) Rafatullah, M.; Sulaiman, O.; Hashim, R.; Ahmad, A. Adsorption of methylene blue on low-cost adsorbents: a review. J. Hazard. Mater. 2010, 177, 70−80. (19) Azhar, M. R.; Abid, H. R.; Sun, H.; Periasamy, V.; Tadé, M. O.; Wang, S. Excellent performance of copper based metal organic framework in adsorptive removal of toxic sulfonamide antibiotics from wastewater. J. Colloid Interface Sci. 2016, 478, 344−352. (20) Yaghi, O. M.; Li, H. Hydrothermal Synthesis of a MetalOrganic Framework Containing Large Rectangular Channels. J. Am. Chem. Soc. 1995, 117, 10401−10402. (21) Li, H.; Eddaoudi, M.; O’Keeffe, M.; Yaghi, O. M. Design and synthesis of an exceptionally stable and highly porous metal-organic framework. Nature 1999, 402, 276−279. (22) James, S. L. Metal-organic frameworks. Chem. Soc. Rev. 2003, 32, 276−288. (23) Georgiev, I. G.; MacGillivray, L. R. Metal-mediated reactivity in the organic solid state: from self-assembled complexes to metalorganic frameworks. Chem. Soc. Rev. 2007, 36, 1239−1248. (24) Snurr, R. Q.; Hupp, J. T.; Nguyen, S. B. T. Prospects for nanoporous metal-organic materials in advanced separations processes. AIChE J. 2004, 50, 1090−1095. (25) Zhang, Z.; Huang, S.; Xian, S.; Xi, H.; Li, Z. Adsorption Equilibrium and Kinetics of CO2 on Chromium Terephthalate MIL101. Energy Fuels 2011, 25, 835−842. (26) Rosi, N. L.; Eckert, J.; Eddaoudi, M.; Vodak, D. T.; Kim, J.; O’Keeffe, M.; Yaghi, O. M. Hydrogen storage in microporous metalorganic frameworks. Science 2003, 300, 1127−1129. (27) Gu, Z. Y.; Wang, G.; Yan, X. P. MOF-5 Metal−Organic Framework as Sorbent for In-Field Sampling and Preconcentration in Combination with Thermal Desorption GC/MS for Determination of Atmospheric Formaldehyde. Anal. Chem. 2010, 82, 1365−1370. (28) Abbasi, A. R.; Rizvandi, M.; Azadbakht, A.; Rostamnia, S. Controlled uptake and release of imatinib from ultrasound nanoparticles Cu 3 (BTC) 2 metal−organic framework in comparison with bulk structure. J. Colloid Interface Sci. 2016, 471, 112. I



Article

(48) Zhao, H.; Liu, X.; Cao, Z.; Zhan, Y.; Shi, X.; Yang, Y.; Zhou, J.; Xu, J. Adsorption behavior and mechanism of chloramphenicols, sulfonamides, and non-antibiotic pharmaceuticals on multi-walled carbon nanotubes. J. Hazard. Mater. 2016, 310, 235−245.

J


Adsorption Behavior and Mechanism of Sulfonamide Antibiotics in

Recommend Documents