Facile Synthesis of Porous Carbon for the Removal of Diclofenac

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Facile Synthesis of Porous Carbon for the Removal of Diclofenac Sodium from Water Naqing Mao, Lijin Huang,* and Qin Shuai* Faculty of Materials Science and Chemistry, Engineering Research Center of Nano-Geomaterials of Ministry of Education, China University of Geosciences (Wuhan), 388 Lumo Road, Hongshan District, Wuhan 430074, P. R. China

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S Supporting Information *

ABSTRACT: In this work, a series of porous carbon materials (PCs) were obtained at different carbonization temperatures (800, 900, 1000, and 1100 °C) by a simple and fast solvent-free method. Moreover, the feasibility of PCs as reliable and efficient adsorbents to capture diclofenac sodium (DCF) from the water was evaluated. Notably, porous carbon (PC) prepared at 1000 °C (PC-1000) was found to be the best candidate for the adsorption of DCF. Remarkably, adsorption equilibrium was achieved within 3 h, which followed a pseudo-second-order kinetic model with a high correlation coefficient (R2 > 0.994). Furthermore, experimental data obtained from adsorption isotherm indicated that the capture of DCF onto PC-1000 followed the Langmuir adsorption model (R2 > 0.997), wherein its maximum adsorption capacity was calculated to be 392 mg/g. In addition, based on the results obtained from the zeta potential of PC-1000 under different pH and the adsorbed quantity of DCF along with functional groups created on the surface of PC-1000, electrostatic and H-bonding interactions were proposed as the possible adsorption mechanisms. Due to its high stability and excellent reusability, PC-1000 has been testified as a promising candidate for removing DCF from contaminated water.

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INTRODUCTION Nonsteroidal anti-inflammatory drugs are effective antiinflammatory, antirheumatic, analgesic, antipyretic, and anticoagulant.1,2 Also, they are one of the most widely used antiinflammatory drugs in the world.3,4 Inevitably, they are easily being released into the environment through direct discharge of domestic sewage and industrial wastewater due to their broad applications.5 Since nonsteroidal anti-inflammatory drugs are lipophilic and nonbiodegradable,6 they can result in a series of serious environmental problems.2 Diclofenac sodium (DCF), one of the most consumed nonsteroidal antiinflammatory drugs,7 has been frequently detected in wastewater and natural water, wherein its concentrations in rivers and groundwater were found in the range of ng/L to g/L.8 Due to its high water solubility (5000 mg/L) and low log Kow (1.56),9 DCF is not easy to remove from water in conventional water treatment plants.10,11 Thus, in general, they may still exist in the treated effluents.12−14 Worse still, even at a low concentration, the continuous emission of DCF into environment will cause serious toxic effects on aquatic organisms. In addition, accumulation through food chain will pose a great threat to other organisms and human health.15,16 Therefore, it © XXXX American Chemical Society

is extremely important to develop a simple and efficient method for removing it from the polluted water. Compared to existing treatment techniques, such as biodegradation,17 advanced oxidation processes,18−20 and electrochemical degradation,21 adsorption stands out because of its high efficiency and simple operation.22−25 For instance, compared to photocatalysis, adsorption will not be limited by light and in some cases, the adsorbed target could be recovered. Adsorption has been widely used for contaminants treatment, including pharmaceuticals,26 heavy metals,27 and dyes.28 So far, several carbonaceous materials, such as carbon nanotube,29−31 graphene,32,33 activated carbon,34 and porous carbon (PC),35−37 have been exploited to remove nonsteroidal drugs from water.38,39 Among them, PCs have received increasing attention due to their high hydrophobicity, large specific surface area, high thermal/chemical stability, and relatively low cost.40,41 Presently, there are many methods for the construction of PCs. In general, the hard- and soft-template Received: June 20, 2019 Accepted: August 21, 2019

A

DOI: 10.1021/acsomega.9b01838 ACS Omega XXXX, XXX, XXX−XXX

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Figure 1. (a) X-ray diffraction pattern, (b) Raman spectra, (c) N2 adsorption−desorption isotherms, and (d) BJH pore-size distributions of different samples.

formaldehyde, which were utilized as the in situ N-dopant and the cross-linking agent, respectively. The templates of ZnCl2 and Pluronic F127 could be removed and converted to carbonaceous residues, respectively, during the process of hightemperature carbonization. The adsorption properties of the PCs over DCF were investigated. The influence of environmental interference factors (ions strength and humic acid) was also explored. Furthermore, a plausible adsorption mechanism was discussed based on the influences of the amounts of acidic functional groups and the zeta potential of PCs on the adsorption performance.

syntheses are two of the most commonly used methods. However, these syntheses involved the preparation of precursors, which were carried out under hydrothermal, solvothermal, or ionic heat conditions, requiring a large number of solvents or high reaction pressure.42−44 As a consequence, neither its environmental impact, process safety, energy consumption, nor production cost is sufficient, which has resulted in difficulties in practical applications.45 Compared with the traditional solvent-involved method, in addition to producing less pollution and waste, the solvent-free method has the advantages of being easy to operate and time-saving.46 Therefore, it is highly desirable to develop a solvent-free method for preparing PC. Recently, Zhang et al.47 synthesized a nitrogen-doped ordered mesoporous carbon (OMC) without employing any solvent or catalyst. The specific surface area of OMCs was >1000 m2/g. Yet, Yu et al.48 prepared a carbon material with a high specific surface area (1340 m2/g) by polymerizing phenol (P) and formaldehyde (F) under high salt condition (ZnCl2) and subsequent high-temperature carbonization.49 These results indicated that solvent-free strategy was promising for PC preparation. In the current work, PC materials were prepared by a solvent-free preparation method via pyrolyzing the mixture of hydroquinone, hexamethylenetetramine (HMTA), Pluronic F127, and ZnCl2. Remarkably, Pluronic F127 and ZnCl2 were used as the soft and hard template, respectively. Meanwhile, hydroquinone was employed as the carbon source, and HMTA was thermally decomposed into ammonia and

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RESULTS AND DISCUSSION XRD, Raman, and N2 Adsorption−Desorption Measurements. To confirm the structure of PCs, XRD and Raman spectroscopy characterizations were performed primarily. As shown in Figure 1a, two broad diffraction patterns appeared at about 26 and 44o, which correspond to the amorphous carbon and the graphitized carbon (100) plane, respectively, indicating the successful preparation of the carbon materials. As the temperature increased, the peak intensity of the graphitized carbon was gradually enhanced. Furthermore, no phase of elemental Zn or ZnCl2 was observed in the XRD spectrum, indicating that Zn might exist at very low concentrations or is completely eliminated during the process of carbonization. It was inferred that first, ZnCl2 is converted into ZnO nanocrystals during the heating process, and then the derived ZnO was transformed into Zn due to the carbothermal reduction; finally, Zn was removed via evaporation at high B


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temperature owing to its low boiling point.48 As shown in Figure S1 and Table S1, XPS analysis also confirmed that the zinc content of PCs was almost negligible ( PC-1100 > PC900 > PC-800), which were much larger than that of FC-1000 (744.3 m2/g). The values were equivalent to or even exceeded the PCs reported in the works of literature, such as oxidized activated carbon (704 m2/g)40 and commercial activated carbon (865 m2/g).53 This phenomenon was attributed to the fact that the evolution of Zn during carbonization accelerated the development of the pores.54 Besides, PC-800 and PC-900 had a similar specific surface area and pore volume, which were much smaller than those of PC-1000 and PC-1100. It was conjectured that some volatile fractions were decomposed and softened, forming an intermediate melt in the pores, but increasing carbonization temperature results in pore expansion or coalescence of neighboring pores to reduce the intermediate melt’s influence into pore volume and surface area due to partial blockage.54−56 SEM and TEM Measurements. To investigate the morphology and pore structure of PC-1000, SEM and TEM characterizations were employed. As shown in Figure 2a,b, PC1000 had a well-developed and uniform porous structure. It could also be seen from the TEM images that PC-1000 has well-distributed and abundant porous structures. The porous structure of the carbon material can result from the vacancies left by the migration and evaporation of PF127 and Zn during the high-temperature carbonization. Choice of Adsorbents. To gain insight into the influence of carbonization temperature and ZnCl2 on the adsorption performance of carbon materials, the adsorption properties of carbon materials toward pharmaceutical pollutants were investigated by taking DCF as a model substrate. As illustrated in Figure 3, PC-1000 showed a better adsorption capacity than other PCs, which could be attributed to the significant influence of the surface area and pore volume of the adsorbents. Since ZnCl2 was generally believed to function as a dehydrating agent,57 it is suggested that ZnCl2 promotes dehydration reactions of the phenolic resin, which results in aromatization of the carbon skeleton with the concomitant

Figure 2. (a, b) SEM and (c, d) TEM images showing the microstructure of PC-1000.

Figure 3. Adsorption properties of different materials toward DCF (conditions: dosage = 5 mg/50 mL, C0 (DCF) = 50 mg/L, T = 25 °C, t = 6 h.).

generation of a pore structure.58 To further investigate the effect of ZnCl2, the adsorption performance of FC-1000 toward DCF was also investigated. As shown in Figure 3, the adsorption capacity of PC-1000 for DCF was much larger than that of FC-1000. This also confirms that ZnCl2 functionalized as a porogen can improve the specific surface area of PCs, leading to an improvement of its adsorption performance. However, it is worth noting that the surface area and pore volume of PC-1100 were similar to those of PC-1000, but their adsorption performance differed. Therefore, the results confirmed that the adsorption capacity of the material for DCF was affected by other factors such as type and quantity of its functional groups in addition to the surface area and pore volume (this will be further discussed in the section of adsorption mechanism). Considering energy consumption and adsorption performance, PC-1000 was selected as an optimized adsorbent for subsequent experiments. As shown in Figure S2, 5 mg was selected as the optimum adsorbent amount for DCF adsorption. Adsorption Kinetics and Isotherms. To determine the time required for adsorption equilibrium, the effect of contact time on the adsorption of DCF onto PC-1000 was observed. As shown in Figure 4a, the adsorption equilibrium for DCF C


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Figure 4. Influence of (a) contact time (C0 (DCF) = 50 mg/L, T = 25 °C) and (b) initial concentration (t = 6 h) over adsorption (conditions: dosage = 5 mg/50 mL, T = 25, 35, 45 °C).

Table 1. Kinetic Parameters for the Adsorption of DCF onto PC-1000 pseudo-first-order model target analyte DCF

Qe actual value (mg/g)

Qe calculated value (mg/g)

330

pseudo-second-order model

K1 (1/min) 6.68 × 10

146

−3

R

2

Qe calculated value (mg/g)

0.584

R2

K2 (g/(mg min)) −4

1.43 × 10

358

0.994

a

K1 (1/min) and K2 (g/(mg min)) represent the rate constant of the corresponding models, and Qe is the amount of analyte adsorbed by per mass unit of adsorbent at equilibrium (mg/g).

Table 2. Isotherm Parameters for the Adsorption of DCF onto PC-1000 Langmuir parameters

Freundlich parameters 2

target analyte

experimental temperature (°C)

Qe (mg/g)

Ka

Q0 (mg/g)

R

KF

1/n

R2

DCF

25 35 45

346 360 385

0.078 0.067 0.052

392 415 462

0.997 0.995 0.993

121.8 111.4 95.0

0.233 0.262 0.313

0.864 0.864 0.872

a

Ka and KF represent Langmuir and Freundlich constants, respectively.

over as-prepared PC-1000 could be obtained within 3 h. The experimental data were analyzed using pseudo-first-order and pseudo-second-order models (Supporting Information). The parameters are summarized in Table 1. As shown in Figure S3, the pseudo-second-order model with a higher linear correlation (R2 > 0.994) was more suitable to describe the adsorption of DCF over PC-1000 compared to the pseudo-first-order model. In addition, the calculated Qe value obtained from the pseudosecond-order kinetic model was more closely related to the experimental value, indicating that the rate control step was mainly chemical adsorption.59 The effect of initial DCF concentration on adsorption was also investigated. The obtained isotherm, as shown in Figure 4b, revealed that the amount of the DCF adsorbed onto the PC-1000 gradually ascended before reaching a steady state. The Langmuir and Freundlich isothermal models were utilized for data simulation (details can be found in the Supporting Information). The parameters and the fitting curves are shown in Table 2 and Figure S4, respectively. The linear correlation coefficient for the Langmuir model (R2 > 0.997) was higher than that of the Freundlich model (R2 > 0.864), indicating that the single-layer chemisorption played a dominant role in the adsorption process.66 As could be seen from Table 2, the value of maximum adsorption capacity (Q0) was 392 mg/g at 25 °C. Table 3 shows the performance of the reported DCF adsorbents; the as-prepared PC-1000 had equal or even better

Table 3. Maximum Adsorption Capacities (Q0) of Some Studied Adsorbents for the Adsorption of DCF from the Water adsorbent CNT/HNO3 AC from agricultural byproduct CDM6-K1000 CTAB-ZIF-67 CDC-1000 PCDM-1000 PC-800 PC-900 PC-1000 PC-1100

Q0 (mg/g) reference

BET surface area (m2/g)

equilibrium time (min)

190 793

60 30

7 2

24 56

60 61

1484 1082 1676 1855 922 969 1236 1224

240 60 20 360 180 180 180 180

6.5 6.5 6.5 3 6.5 6.5 6.5 6.5

503 61 351 393 186 195 392 309

62 63 64 65 this work

pH

performance than the other adsorbents. These results illustrated that PC-1000 was powerful and well suited for efficient and rapid removal of DCF from wastewater. Possible Adsorption Mechanism. Understanding the adsorption mechanism is vital to the adsorbent for its performance optimization and commercial application. The results obtained in this study from the adsorption of DCF by the synthesized PC (Figure 3 and Table S2) indicated that D


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Previous studies had confirmed that aromatic compounds such as DCF could be adsorbed onto porous materials (such as carbon nanotubes70 and PC65) due to the contribution of π−π stacking interaction between the benzene rings of frameworks and DCF. In this study, electrostatic interactions and possible π−π interactions did not adequately explain the amount of DCF adsorbed by PC-1000. Although the surface area of PC1100 was similar to that of PC-1000, the adsorption capacity was not as good as that of PC-1000, which indicated that the surface groups of PCs also played an important role. As shown in Table S3, there were carboxylic acid (pKa = 4.2), lactone, and phenolic (pKa =10.0) groups on the surface of the adsorbents. Meanwhile, the absorption peaks corresponding to the carboxylic group at 1650 and 1400 cm−1 and lactone group at 1330 to 1050 cm−1 were observed in the infrared spectrum of PC-1000 (see Figure S5). The value of qt that decreased with increasing pH (Figure 5) could be explained by the increase in the negative surface charge of the adsorbent and the number of deprotonated species (COO− and O−) of the DCF. Under these conditions, electrostatic repulsion between negative DCF and adsorbents increased at high pH. Additionally, compared to PC-1100, PC-1000 with more carboxylic acid groups exhibited a better adsorption performance for DCF under natural pH, providing further evidence for the presence of electrostatic interactions. In addition, due to the presence of abundant polar groups on adsorbents and DCF, hydrogen bonding interactions may occur between adsorbents and DCF. Phenol/carboxylic acid protons could pass hydrogen bonding with carbonyl and carboxylate functional groups (protonation) or deprotonated oxygen atoms to form attractive interactions, which have been observed by some of the previously reported works.41,71 Therefore, electrostatic, π−π stacking and hydrogen bonding interactions may be plausible mechanisms for efficient capture of DCF. The schematic diagram of adsorption mechanism at the molecular level is showed as follows (Figure 6). Effect of Humic Acid. Considering the complexity of the actual wastewater sample, the effect of humic acid (HA), which is widely presented in the actual wastewater, on adsorption was evaluated. As shown in Figure 7, the HA has little effect on the adsorption of DCF by PC-1000. This result was due to the low adsorption affinity of PC-1000 for HA. Thus, the PC-1000 could be used as a promising adsorbent for contaminant treatment. Reusability of Adsorbents. Reusability is an important indicator to evaluate the efficiency and cost-effectiveness of any

there was another specific interaction between DCF and PC in addition to the surface area of the adsorbent. When the solution’s initial pH was lower than the pKa of the diclofenac acid (4.2), the DCF exists in its neutral form; thus, its solubility is low ( 4.2. On the other hand, the surface of PC-1000 was negatively charged under such condition, and the surface charge decreased with pH increase. These results were similar to those reported for other PCs used for DCF uptake.69 If the adsorption was primarily motivated by electrostatic interaction, the amount of adsorbed DCF could be negligible at high pH condition. However, the experimental results showed that PC1000 still had considerable adsorption capacity for DCF. Therefore, some other factors that contributed to adsorption should be taken into consideration.

Figure 6. Schematic diagram of adsorption mechanism at the molecular level. E


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syringe filter (polytetrafluoroethylene, hydrophobic, 0.45 μm). The results are shown in Figure 9 and Tables 4 and 5. Adsorption peaks centered around 276 nm were observed for both samples, indicating the presence of contaminants. A spiked experiment was also designed for both samples. Remarkably, 5 mg of adsorbent was put into 50 mL of solution, and the resulting mixture was incubated at 25 °C for 6 h under shaking. Then, the filtered solution was tested. The results showed that PC-1000 could successfully remove the contaminants in the actual water samples with high efficiency (Table 5).

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CONCLUSIONS In short, we have successfully established a simple, fast, solvent-free one-pot process for the preparation of PCs. The prepared PCs had a rich microporous structure, high specific surface area, and excellent thermal/chemical stability as well as remarkable adsorption properties toward drug contaminants in aqueous solution. Moreover, it possessed very good reusability for DCF removal. We are firmly convinced that this work can improve the feasibility of the PCs as an effective candidate for removing drug contaminants from aqueous solutions.

Figure 7. Effect of humic acid (conditions: dosage = 5 mg/50 mL, C0 (DCF) = 50 mg/L, T = 25 °C, t = 6 h).

adsorbent. The reusability of PC-1000 for DCF removal was confirmed by solvent (0.1 mol/L NaOH in methanol) washing followed by repeated drying by vacuum. To authenticate that the PC-1000 successfully adsorbed DCF, the FT-IR spectra of PC-1000 (fresh, adsorbed DCF and reused) and DCF were collected (Figure S5). The FT-IR spectra of fresh PC-1000, DCF, and DCF-adsorbed PC-1000 are shown in Figure S5. The peaks of DCF were observed on the DCF-adsorbed PC1000, which verified that DCF was adsorbed onto PC-1000 successfully. At the same time, the FT-IR spectrum of the reused PC-1000 showed a similar frequency band to the original one, indicating successful removal of the adsorbed DCF. The repeatability test was carried out for five cycles, and the results obtained are shown in Figure 8. After the cycles, the

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MATERIALS AND METHODS Chemicals. Zinc chloride (≥98%), hexamethylenetetramine (HMTA), methanol, and hydroquinone were obtained from Sinopharm Chemistry Reagent Co., Ltd. (Shanghai, China). Pluronic F127 and humic acid (HA) were obtained from Aladdin (Shanghai, China). Diclofenac sodium (DCF) was obtained from Macklin (Shanghai, China). N2 (99.99%) was supplied by the Oxygen Co. of WISCO (Wuhan, China). All the chemicals were of analytical grade and utilized as received. Preparation of PC. Hydroquinone (0.5 g), 0.15 g of HMTA, 1.25 g of Pluronic F127, and 3 g of ZnCl2 were placed in a mortar and ground at room temperature for 10 min to make them uniformly mixed. Then, the mixture was placed in the center of a 5 × 3 cm porcelain boat; the porcelain boat was placed in a tube furnace, calcined at 160 °C for 2 h under a flowing nitrogen atmosphere, calcined at 360 °C for 2 h to remove Pluronic F127, and then heated to 800 °C for 2 h to carbonize. Finally, it was naturally cooled to room temperature, and the product PC was collected. The carbonization temperatures were changed to 900, 1000, and 1100 °C to explore the optimum synthesis temperature, where the remaining conditions were unchanged. The obtained PC was referred to as PC-T, where T represented the carbonization temperature. To further investigate the effect of ZnCl2 on the material synthesis, a porous carbon named FC-1000 was prepared at 1000 °C without ZnCl2. Characterization of PCs. An X-ray diffractometer (D8 Advance, Bruker, Germany) with Cu-Kα radiation was used to analyze the crystal phases of PCs. Fourier transform infrared (FT-IR) spectroscopy was recorded with a Nicolet 6700 (Thermo Fisher, USA). The elemental valence states (C, O, N, and Zn) were analyzed using X-ray photoelectron spectroscopy (XPS) with an Al K-alpha X-ray source by EscaLab 250Xi (Thermo Fisher Scientific, USA). Raman spectra were obtained using Labor Raman HR (Horiba, USA). The N2 adsorption isotherms at −196 °C were measured by using a surface area and porosity analyzer (ASAP2460, Micromeritics, USA) to evaluate the special surface area. The N2 adsorption−

Figure 8. Reused ability of PC-1000 for DCF (conditions: dosage = 5 mg/50 mL, C0 (DCF) = 50 mg/L, T = 25 °C, t = 6 h).

amount of DCF adsorbed by PC-1000 was negligibly reduced, indicating that PC-1000 had very good stability and reusability. Hence, PC-1000 can be considered as an easy-to-prepare, recyclable, and competitive adsorbent for removing drug contaminants from water. Practical Application. The adsorbent was applied to treat the lake water samples from two lakes (East Lake and Fruit Lake, Wuhan), and the sampling sites were located around the hospitals. Before adsorption, the samples were filtrated with a F


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Figure 9. (a) UV scan of actual water sample and (b) actual water sample spiked 5 ppm DCF before and after being adsorbed.

mg of adsorbent was put into 50 mL of solution and the resulting mixture was incubated at 25 °C for a certain period under shaking. Afterward, the solutions were collected by filtration with a syringe filter (polytetrafluoroethylene, hydrophobic, 0.45 μm). The concentration of the residual target contaminant was evaluated by using an ultraviolet spectrophotometer (Shimadzu, UV-1800, Japan) at 276 nm. The average values considered as the standard were acquired from three consecutive experimental results. Different kinetic models (pseudo-first-order and pseudo-second-order kinetic models) and adsorption isotherm models (Langmuir and Freundlich models) were utilized to analyze the adsorption results. The detail methods/equations for the calculation of adsorption results are explained in the Supporting Information. The effect of the solution’s initial pH on the adsorbed amount over PC1000 was ascertained by adjusting the pH values with HCl or NaOH solution (0.1 mol/L). The reusability of PC-1000 for DCF capture was verified by ultrasonically washing several times with 0.1 mol/L NaOH in methanol, and subsequent drying was conducted by vacuum drying at 60 °C overnight. Total organic carbon (TOC) in the collected water samples before and after adsorption was determined by using a TOC analyzer (TOC-L CPN, Shimadzu, Kyoto, Japan). Boehm Titration Experiments. PC (0.50 g) for analysis was added to each of the three separate beakers containing 50 mL of 0.10 mol/L NaOH,·Na2CO3, or NaHCO3, respectively, and the mixture was magnetically stirred at room temperature for 24 h. Finally, the liquid fraction was collected by filtration, and the amount of the acidic functional group was calculated by titrating the filtered solution with 0.10 mol/L standard aqueous solution of HCl. Methyl red was used as an indicator for all titrations.

Table 4. Solution pH, Total Organic Carbon (TOC), and Metal Ion Concentration of the Collected Samples before and after Adsorption sample 1

sample 2

parameter

before adsorption

after adsorption

before adsorption

after adsorption

pH TOC (mg/L) K+ (mg/L) Na+ (mg/L) Ca2+ (mg/L) Mg2+ (mg/L) Fe3+ (mg/L) Cu2+ (mg/L) Al3+ (mg/L)

7.62 5.30 6.74 47.1 43.5 10.0 0.02 0 0.30

8.05 4.88 6.35 37.2 43.1 9.97 0 0 0.25

7.76 5.62 6.83 45.7 39.1 9.68 0.03 0 0.29

8.14 4.30 6.16 39.4 38.9 9.54 0 0 0.28

desorption isotherms of PCs pretreated at 150 °C for 12 h were achieved. The surface areas were estimated from the N2 adsorption isotherms using the Brunauer−Emmett−Teller (BET) equation in the relative pressure range of 0.05−0.20. The pore volume and pore size distribution were determined using the Barrett−Joyner−Halenda (BJH) model and t-plot method, respectively. The structure and morphology of the samples were observed on a scanning electron microscope (SEM) (SU8010, Hitachi, Japan) and a transmission electron microscope (TEM) (JEM-2010, Tokyo, Japan). The zeta potential of adsorbent was measured at various pH values using a zeta potential and nanometer particle size analyzer (Nano ZS90, Mastersizer, UK). The amount of acidic functional groups (AFG) of materials was determined by Boehm titration.72 Adsorption Experiments. DCF was dissolved in water directly to prepare 100 mg/L stock solutions. Solutions of DCF with the chosen concentrations of 10−100 mg/L for adsorption experiments were prepared by successive dilution of the prepared stock solution. For the adsorption experiment, 5

Table 5. Studies of Adsorption of DCF onto PC-1000 from Actual Water Samples low spiked concentration (5 mg/L)

high spiked concentration (20 mg/L)

analyte

concentration (mg/L)

removal efficiency (%)


RSD (%, n = 3)


RSD (%, n = 3)

DCF

1.0 1.2

100.0 100.0

100.0 91.9

0.6 0.7

99.5 92.5

3.2 3.1

G


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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsomega.9b01838.

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Adsorption kinetics and adsorption isotherm analysis; XPS spectra of PCs; influence of adsorbent dosage; pseudo-first-order and pseudo-second-order kinetic plots for the adsorption of DCF over PC-1000; linear regression by fitting the equilibrium adsorption data with the Langmuir and Freundlich adsorption models for DCF; FT-IR spectra of different samples; XPS spectra of PCs; corresponding parameters of the specific surface areas and pore properties of PCs; and concentrations of acidic functional groups determined by Boehm titration (PDF)

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. Tel.: 86-27-67884283 (L.H.). *E-mail: [email protected] (Q.S.). ORCID

Lijin Huang: 0000-0002-0555-7823 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (21806148), Fundamental Research Funds for the Central Universities, and China University of Geosciences (Wuhan) (grant nos.CUG170102 and CUG180610).

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Facile Synthesis of Porous Carbon for the Removal of Diclofenac

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