In this study, hypercrosslinked styrene-divinylbenzene copolymers (HCCPs) designated as HCCP-1DVB, HCCP-2DVB and HCCP-3DVB were obtained by post-crosslinking of styrene-divinylbenzene copolymers containing 1, 2 and 3 % of divinylbenzene by chloromethyl methyl ether via the Friedel-Crafts reaction. The chemical structure, porous and morphological characteristics of HCCPs were determined by FT-IR, low-temperature nitrogen adsorption-desorption method and SEM, respectively. The synthesized hypercrosslinked copolymers had high surface area values and different micro/mesoporous structures. It was found that mesopore volume increased with a decrease in divinylbenzene content in a copolymer. HCCP-1DVB had the largest mesopore volume (0.53 cm3/g), the highest adsorption capacity for rifampicin (qmax = 183.27 mg/g), and the highest rifampicin adsorption rate. The adsorption equilibrium and kinetic processes were well described by the Langmuir model and the pseudo-second-order model. The experimental data indicated that the removal efficiency of rifampicin reached 99.8 % at the dosage of HCCP-1DVB equal to 80 mg/10 mL. After 5 cycles of reuse, the adsorption capacity of HCCP-1DVB decreased only by 7 %, which indicates sufficient stability and reusability of this hypercrosslinked copolymer.
Research Article
Tuning the porosity of hypercrosslinked styrene-divinylbenzene copolymers for efficient adsorption of rifampicin from aqueous media
https://doi.org/10.21203/rs.3.rs-3243528/v1
This work is licensed under a CC BY 4.0 License
Journal Publication
published 18 Oct, 2023
You are reading this latest preprint version
hypercrosslinked copolymers
porosity
adsorption
rifampicin
Rifampicin (RIF), which belongs to the class of ansamycin antibiotics, is one of the most effective drugs for tuberculosis therapy [1]. However, RIF is resistant to biodegradation (compared, for instance, to penicillin), and high dosages of the drug are required to achieve therapeutic effect [2]. The presence of RIF and other antibacterial agents in wastewater can lead to the appearance of antibiotic-resistant bacteria and antibiotic-resistance genes [3]. RIF is a large hydrophobic molecule (it has log P = 2.7 and a relatively high molecular weight of 822 g/mol, Fig. 1); therefore, its removal from aqueous media is a challenging task.
Various methods (biodegradation [4], membrane filtration [5], photocatalytic degradation [6] and adsorption [7]) are applied to remove antibiotics from wastewater. However, adsorption is the most efficient method, since it possesses such advantages as high efficiency, low cost, and simplicity. Several types of materials have been used to adsorb RIF, including nanoparticles of various compositions [8–10], adsorbents based on chitosan [11, 12] and cocoa shells products [13].
In recent years, hypercrosslinked polymers have been widely used as adsorbents. These polymers have high surface areas, pore volumes, and well-developed microporous structures; other benefits include relative ease of synthesis and possibility of surface modification [14, 15], which allows one to produce materials with desired characteristics. One of the representatives of such polymers is hypercrosslinked polystyrene (HCP), which is used as an adsorbent for a wide range of organic compounds [16]. HCP has a non-polar surface and therefore possesses a great potential for adsorption of hydrophobic molecules, such as RIF.
The synthetic approach for obtaining HCP is based on crosslinking of linear polystyrene in solution or post-crosslinking of slightly crosslinked styrene-divinylbenzene copolymers in the swollen state [17] with various external crosslinkers (chloromethyl methyl ether, dimethoxymethane, etc.) [18–21] via the Friedel-Crafts reaction using different Lewis acids as catalysts [22, 23]. It is also possible to obtain HCPs using copolymers based on vinylbenzyl chloride, which acts as an internal crosslinker in the post-crosslinking stage [24]. The initial slightly crosslinked copolymers can be obtained in the form of spherical particles by heterogeneous polymerization; therefore, they are most frequently used as precursors for HCPs [25].
Adsorption of large organic molecules on HCP can be hindered by steric factors due to the presence of well-developed microporous structure. Macroporous styrene-divinylbenzene copolymers are able to adsorb large organic molecules, but their adsorption capacity values are relatively low due to small specific surface areas [26, 27]. At the same time, HCPs with predominantly mesoporous structure are promising materials for efficient adsorption of various bulky organic molecules.
It is possible to achieve formation of mesopores, along with micropores, in the structure of HCPs by changing the amount of divinylbenzene (DVB) in the initial copolymer. The predominantly mesoporous structure appeared at a DVB content of less than 6% [28]. It was shown that an increase in the DVB content from 0.5 to 2% led to a significant increase in copolymer surface area. The authors of [29] did not observe adsorption of proteins on HCPs containing more than 1% of DVB. On the other hand, good adsorption of a series of small phenyl carboxylic acids was observed due to the predominantly microporous structure of HCPs. Nevertheless, the effect of the amount of DVB in the initial copolymer on the adsorption properties of HCP towards large organic molecules has not been comprehensively studied. Thus, a distinctive and advantageous feature of HCPs is the possibility to adjust their porosity parameters depending on the nature of the adsorbate.
In this work, we synthesized hypercrosslinked styrene-divinylbenzene copolymers with well-developed micro- and mesopore structures intended for effective adsorption of RIF from aqueous solutions. The amount of DVB in the hypercrosslinked copolymers (HCCPs) varied from 1 to 3%, which allowed us to determine the most promising polymeric matrix for RIF adsorption. The effects of pH and temperature on the RIF adsorption, kinetics and thermodynamics of the process were also studied.
2.1. Materials
Styrene (ST, 99%), divinylbenzene (DVB, 80%), benzoyl peroxide (BPO, 75%), and anhydrous ferric (III) chloride (FeCl3, 97%) were purchased from Sigma-Aldrich (Germany). Polyvinyl alcohol (PVA), sodium chloride (NaCl), potassium dichromate (K2Cr2O7), and 1,2-dichloroethane (1,2-DCE) were purchased from LenReaktiv (St Petersburg, Russia). Rifampicin was supplied by BelMedPreparaty (Minsk, Belarus). Commercially available hypercrosslinked adsorbents Macronet Hypersol MN-200, MN-202, and MN-270 were purchased from Purolite International (USA).
2.2. Synthesis of copolymers
The copolymers were prepared according to the modified procedure [29] by means of free radical suspension polymerization. A 250 mL three-necked cylindrical flask equipped with a power-driven stirrer, a reflux condenser, and a thermometer was charged with 105 mL of the aqueous phase containing 1 wt% of PVA, 3 wt% of NaCl, and 0.02 wt% of K2Cr2O7. Then the organic phase containing styrene (15 g, 0.143 mol), benzoyl peroxide (0.4 g), and DVB (1, 2, or 3 mol%) was added. Copolymerization was performed for 10 h at 85°С at continuous stirring (1850 rpm). The resulting copolymer beads were filtered off and washed with hot water, acetone, and cold water. The beads were dried in air overnight, then under vacuum at 333 K for 8 h. The obtained copolymers were designated as CP-1DVB, CP-2DVB, and CP-3DVB.
2.3. Synthesis of hypercrosslinked copolymers
The hypercrosslinked copolymers were prepared by the Friedel-Crafts reaction using chloromethyl methyl ether (CMME) as an external crosslinker; CMME was prepared as described in [30]. Typically, 3.0 g (0.028 mol) of dry copolymer was swollen with 25 mL of 1,2-DCE containing 2.25 g (0.028 mol) of CMME overnight in a three-necked 50 mL flask. Then the flask equipped with a power-driven stirrer, a thermometer, and a reflux condenser with a calcium chloride tube was cooled down to 273 K, and 1.36 g (0.0084 mol) of anhydrous FeCl3 was quickly added at vigorous stirring (700 rpm). The temperature was gradually raised to 323 K, and the reaction was performed for 2 h at continuous stirring. After that, the temperature was raised to 358 K, and the reaction was carried out for 9 h. The beads of hypercrosslinked copolymers were washed with acetone, ethanol, 0.5 M aqueous solution of HCl, and distilled water. The beads were dried in air overnight and then under vacuum at 333 K for 8 h. The obtained hypercrosslinked copolymers were designated as HCCP-1DVB, HCCP-2DVB and HCCP-3DVB.
2.4. Characterization
Fourier transform infrared spectra (FT-IR) were obtained using an IRAffinity-1S spectrometer (Shimadzu, Japan) (KBr pellets) in the 4000 to 400 cm− 1 wavenumber range. The pore structure of the samples was determined from N2 adsorption-desorption isotherms measured at 77 K with a Nova 1200 gas sorption analyzer (Quantachrome, USA). Morphology of the samples was studied using a SUPRA 55-VP field emission scanning electron microscope (SEM) (Carl Zeiss, Germany) operating at 5 kV. The concentration of rifampicin was measured with the aid of an SF-2000 UV-spectrophotometer (OKB Spectr, Russia) at a wavelength of 474 nm; the concentration was determined by the standard curve method. The data were processed using the OriginPro 2021 software.
2.5. Adsorption isotherms
0.02 g of dry HCCP was introduced into a 50 mL flask, then 20 mL of RIF aqueous solution was added. The initial concentrations of RIF C0 (mg/L) were 100.0, 200.0, 300.0, 400.0, and 500.0 mg/L. The flasks were placed on the orbital shaker and shaken for 4 h at various temperatures (298, 308 and 318 K) at 160 rpm. 0.1 M NaOH and 0.1 M HCl solutions were used to adjust pH. The original solution was used directly without adjustment with HCl or NaOH. The equilibrium concentration of RIF Ce (mg/L) was determined spectrophotometrically by the standard curve method. The equilibrium capacity qe (mg/g) was calculated by Eq. (1) as:
$${q}_{e}=\frac{\left({C}_{0}-{C}_{e}\right)V}{m}$$
1
where V (L) is the volume of the solution, and m (g) is the HCCP mass.
2.5. Adsorption kinetics
0.1 g of dry HCCP was introduced into a 250 mL flask, and aqueous solution of RIF (100 mL) was added. The initial concentration of RIF C0 (mg/L) was about 500.0 mg/L. The flasks were continuously shaken at 298 K until equilibrium was reached. During the experiment, samples of solution (0.2 mL) were taken at different time intervals, and the RIF concentration was determined spectrophotometrically. The adsorption capacity qt (mg/g) at contact time t (min) was calculated according to Eq. (2) as:
$${q}_{t}=\frac{\left({C}_{0}-{C}_{t}\right)V}{m}$$
2
where Ct (mg/L) is the concentration of rifampicin at contact time t.
2.6. Effect of the adsorbent dosage on removal efficiency
Different amounts (10–80 mg) of dry HCCP were introduced into 25 mL flasks, and 10 mL of RIF aqueous solution with concentration about 500.0 mg/L was also added. The flasks were shaken for 4 h at 298 K. After that, the equilibrium concentration of RIF Ce (mg/L) in each flask was determined spectrophotometrically, and the removal efficiency (RE) of RIF (%) was calculated according to Eq. (3) as:
$$RE=\frac{{C}_{0}-{C}_{e}}{{C}_{0}}\times 100 \%$$
3
2.6. Reusability tests
After adsorption, HCCP was filtered off and regenerated using ethanol for 3 h at constant stirring with an orbital shaker at 298 K. Then the regenerated HCCP was dried overnight at 353 K. Adsorption-desorption cycles of RIF were performed five times at an initial RIF concentration of 500 mg/mL and the HCCP to ethanol ratio equal to 10 mg/10 mL.
3.1. Characterization
Slightly crosslinked styrene-divinylbenzene copolymers containing 1, 2, and 3% of DVB (CP-1DVB, CP-2DVB, CP-3DVB) were prepared by free radical suspension polymerization as shown in Scheme 1. The synthesis conditions (cylindrical shape of flask, high stirring rate and the presence of 1 wt% of suspension stabilizer) made it possible to prepare particles with relatively narrow size distributions. Hypercrosslinked copolymers (HCCP-1DVB, HCCP-2DVB, and HCCP-3DVB) were obtained by post-crosslinking of slightly crosslinked copolymers using CMME as an external agent. In this case, the selected amount of CMME introduced into the reaction (1 mol of CMME per 1 mol of the copolymer) ensures that, statistically, each phenyl group of the copolymer forms methylene bonds with two neighboring phenyl groups [17].
The FT-IR spectra of the copolymer before (CP-1DVB) and after the post-crosslinking procedure (HCCP-1DVB) are shown in Fig. 2. The absorption bands at 2853 and 2918 cm–1 can be assigned to C–H symmetric and asymmetric stretching vibrations. The absorption bands at 753 and 820 cm–1 correspond to C–H bending vibrations of mono- and disubstituted phenyl rings [31]. Intensities of the absorption bands at 753 and 820 cm–1 changed after the post-crosslinking procedure. The absorption band at 1704 cm–1 is traditionally assigned to C = O vibrations. However, in [32] it has been proved that hypercrosslinked polystyrenes have no functional groups, and this band is most probably related to vibrations of polysubstituted aromatic rings. Thus, it may be assumed that hypercrosslinked structure was formed under the synthesis conditions described above.
The nitrogen adsorption-desorption isotherms of the synthesized HCCPs are presented in Fig. 3(a). According to the IUPAC classification [33], these isotherms belong to type IV, which confirms micro/mesoporous structure of the samples. The hysteresis loop between the adsorption and desorption branches for HCCP-1DCB is assigned to the H2 type and suggests that this sample has a predominantly mesoporous structure. For HCCP-2DVB, the hysteresis loop is an intermediate between the H2 and H4 types, while the hysteresis loop for HCCP-3DVB can be assigned to the H4 type. Thus, the shapes of the hysteresis loops of HCCPs changed from the H4 to the H2 type with a decrease in the DVB content from 3 to 1%. This fact indicates the formation of mostly mesoporous structure during post-crosslinking of copolymers with a lower DVB content. The absence of a sharp rise in the isotherms in the region of high relative pressures indicates the absence of macropores in the HCCP structure. The pore size distribution curves of the synthesized HCCPs are presented in Fig. 3(b). In the case of HCCP-1DVB, the contribution of small mesopores with sizes of 2–4 nm is significantly higher in comparison with HCCP-2DVB and HCCP-3DVB. At the same time, HCCP-2DVB and HCCP-3DVB have a large number of micropores with sizes less than 2 nm.
Table 1 summarizes the information about porous structure of the obtained HCCPs. The values of the surface area, total pore volume and mesopore volume increase with a decrease in the DVB content from 3 to 1%. Sample HCCP-1DVB has the highest value of mesopore volume (0.53 cm3/g). Thus, a decrease in the DVB content in the initial copolymer promotes the formation of mesoporous structure in the post-crosslinking stage. This trend was noted in [28]; it may be explained by lower rigidity of the network with lower DVB content. As a result, the distances between chains are less regular, which contributes to lower homogeneity of post-crosslinking throughout the polymer.
|
Sample |
SBETa (m2/g) |
Vmicrob (cm3/g) |
Vmesoc (cm3/g) |
Vtotald (cm3/g) |
|---|---|---|---|---|
|
HCCP-1DVB |
946 |
0.12 |
0.53 |
0.65 |
|
HCCP-2DVB |
897 |
0.23 |
0.35 |
0.58 |
|
HCCP-3DVB |
760 |
0.22 |
0.27 |
0.49 |
| a Surface area calculated from nitrogen adsorption isotherms at 77.3 K using BET equation | ||||
| b micropore volume calculated using t-plot | ||||
| c mesopore volume calculated as Vtot - Vmicro | ||||
| d total pore volume calculated from nitrogen isotherm at P/P0 = 0.989, 77.3 K | ||||
It is seen from the SEM images presented in Fig. 4 that fracture sections of the synthesized HCCPs do not indicate visible pore structure because samples are characterized by micro/mesoporous structure with only small mesopores. However, the scanning micrographs clearly show that the texture becomes smoother in going from HCCP-1DVB (Fig. 4(a, d)) to HCCP-3DVB (Fig. 4(c, f)). This indicates that as the content of DVB in the precursor increases from 1 to 3%, the texture of hypercrosslinked polymer becomes more uniform.
Thus, sample HCCP-1DVB with a pronounced mesoporous structure is promising for efficient adsorption of large organic molecules, in particular, rifampicin.
3.2. Adsorption isotherms and thermodynamics
Figure 5 displays the equilibrium isotherms of RIF adsorption on HCCP-1DVB, HCCP-2DVB and HCCP-3DVB at 298 K. At the equilibrium concentration (Ce) equal to 100 mg/L, the equilibrium adsorption capacity (qe) decreased in the order HCCP-1DVB (122.6 mg/g) > HCCP-2DVB (42.8 mg/g) > HCCP-3DVB (22.1 mg/g). The RIF molecule has a significant size and, therefore, can be adsorbed in mesopores. For this reason, the adsorbent with the largest mesopore volume (HCCP-1DVB) has the most adsorption capacity towards RIF.
The experimental data (Fig. 5) were analyzed using the Langmuir and Freundlich models described by equations (4) and (5), respectively [34]:
$${q}_{e}=\frac{{K}_{L}{C}_{e}{q}_{m}}{1+{K}_{L}{C}_{e}}$$
4
$${q}_{e}={K}_{F}{C}_{e}^{\frac{1}{n}}$$
5
where qm (mg/g) is the maximum adsorption capacity; Ce (mg/L) is the equilibrium concentration of RIF in solution; KL (L/mg) and KF ((mg/g)·(L/mg)1/n)) are the adsorption constants of Langmuir and Freundlich equations, respectively.
Table 2 lists the parameters obtained using these models. The adsorption equilibrium data for all samples are in better agreement with the Langmuir model due to higher correlation coefficients (R2 > 0.99). This model suggests the predominant monolayer adsorption on a homogeneous surface. The highest maximum adsorption capacity (qm) was 183.27 mg/g for HCCP-1DVB. This value is comparable with other adsorbents used for RIF adsorption or even significantly higher (Table 3).
|
Langmuir model |
Freundlich model |
|||||
|---|---|---|---|---|---|---|
|
Sample |
qm (mg/g) |
KL (L/mg) |
R2 |
KF ((mg/g)·(L/mg)1/n) |
n |
R2 |
|
HCCP-1DVB |
183.27 |
2.02 × 10− 2 |
0.994 |
26.82 |
3.18 |
0.987 |
|
HCCP-2DVB |
89.81 |
0.91 × 10− 2 |
0.995 |
7.81 |
2.71 |
0.983 |
|
HCCP-3DVB |
66.94 |
0.49 × 10− 2 |
0.994 |
2.501 |
2.08 |
0.981 |
|
Adsorbent |
qm (mg/g) |
Reference |
|---|---|---|
|
Chitosan |
66.91 |
[11] |
|
Graphene oxide/Chitosan/Fe3O4 |
101.22 |
[12] |
|
Fe3O4 nanoparticles |
107.7 |
[10] |
|
Zeolite − polypyrrole∕TiO2 nanoparticles |
112.31 |
[8] |
|
Activated carbon cocoa shells |
135.2 |
[13] |
|
β-cyclodextrin/mesoporous SiO2 nanospheres |
246.8 |
[9] |
|
HCCP-1DVB |
183.27 |
This work |
The effect of temperature on the RIF adsorption on HCCP-1DVB was investigated at 298, 308 and 318 K (Fig. 6). The equilibrium adsorption capacity increases with increasing temperature, suggesting that adsorption is an endothermic process. The equilibrium data were fitted to the above-mentioned models, and the corresponding parameters are given in Table 4. The Langmuir model was more suitable to fit the adsorption data with higher correlation coefficients (R2 > 0.99) as compared with the Freundlich model. According to [35, 36], the KL values can be used for calculating thermodynamics parameters, including the changes in enthalpy (ΔH, kJ/mol) and entropy (ΔS, J/(mol·K)) by the van’t Hoff Eq. (6) as follows:
where KL (L/mg) is the Langmuir constant, MRIF (822.09 g/mol) is the molecular weight of RIF, T (K) is the temperature, and R (8.3145 J/(mol·K)) is the gas constant.
The Gibbs free energy (ΔG, kJ/mol) can be calculated using Eq. (7):
The values of ΔS (143.56 J/(mol·K)) and ΔH (18.72 kJ/mol) were calculated according to [36]. The ΔG values calculated according to Eq. (7) were equal to − 24.06 kJ/mol at 298 K, – 25.51 kJ/mol at 308 K, and − 26.93 kJ/mol at 318 K. The positive ΔH value confirms that the RIF adsorption on HCCP-1DVB is an endothermic process. Since the ΔG value is negative, and the ΔS value is positive, it may be concluded that the RIF adsorption is a spontaneous and disordered process.
|
Langmuir model |
Freundlich model |
||||||
|---|---|---|---|---|---|---|---|
|
Sample |
T (K) |
qm (mg/g) |
KL (L/mg) |
R2 |
KF ((mg/g)·(L/mg)1/n) |
n |
R2 |
|
298 |
183.27 |
2.02 × 10− 2 |
0.994 |
26.82 |
3.183 |
0.987 |
|
|
HCCP-1DVB |
308 |
189.59 |
2.53 × 10− 2 |
0.995 |
32.41 |
3.401 |
0.986 |
|
318 |
195.88 |
3.25 × 10− 2 |
0.997 |
40.13 |
3.732 |
0.988 |
|
3.3. Adsorption kinetics
Figure 7 presents kinetic curves for the RIF adsorption on HCCP-1DVB, HCCP-2DVB and HCCP-3DVB. The RIF adsorption rate on HCCPs is high in the initial stage. 52.7, 27.1 and 14.9% of the equilibrium adsorption capacity are attained within the first 5 min for HCCP-1DVB, HCCP-2DVB and HCCP-3DVB, respectively. Then the adsorption rate decreases. More than 90% of the equilibrium adsorption capacity is reached within 30 min for HCCP-1DVB, within 60 min for HCCP-2DVB and HCCP-3DVB. The equilibrium is achieved within 90 min for all adsorbents.
The kinetic data can be fitted to the pseudo-first-order and pseudo-second-order models described by equations (8) and (9), respectively [37, 38]:
$${q}_{t}={q}_{e}(1-{e}^{-{k}_{1}t})$$
8
$${q}_{t}=\frac{{k}_{2}{q}_{e}^{2}t}{1+{k}_{2}{q}_{e}t}$$
9
where qt (mg/g) and qe (mg/g) are the adsorption capacity values at time t (min) and at equilibrium, respectively; k1 (L/min) and k2 (g/(mg·min)) are the constants for the pseudo-first-order and pseudo-second-order models, respectively.
The values of kinetic parameters are given in Table 5. The RIF adsorption on HCCPs is well described by the pseudo-second-order kinetic model due to higher correlation coefficients (R2 ≥ 0.996). The adsorption rate constants of the pseudo-second-order model increase in the order HCCP-1DVB (1.15 × 10− 3 (g/(mg·min)) > HCCP-2DVB (0.74 × 10− 3 (g/(mg·min)) > HCCP-3DVB (0.48 × 10− 3 (g/(mg·min)), which may be related to an increase in the mesopore volume. The adsorption capacity of RIF on HCCPs calculated using the pseudo-second-order model is in good agreement with the qmax value calculated by the Langmuir model.
Pseudo-first-order model | Pseudo-second-order model | |||||
|---|---|---|---|---|---|---|
Sample | qe, cal (mg/g) | k1 (min− 1) | R2 | qe, cal (mg/g) | k2 (g/(mg⋅min)) | R2 |
HCCP-1DVB | 156.26 | 11.89 × 10− 2 | 0.979 | 171.71 | 1.15 × 10− 3 | 0.997 |
HCCP-2DVB | 67.89 | 5.17 × 10− 2 | 0.986 | 80.94 | 0.72 × 10− 3 | 0.996 |
HCCP-3DVB | 47.33 | 3.04 × 10− 2 | 0.989 | 61.41 | 0.48 × 10− 3 | 0.996 |
3.4. Effect of pH on adsorption
RIF is a zwitterionic molecule (pKa1 = 1.7, pKa2 = 7.9) and thus can exist in different states depending on pH; this may affect its adsorption, since HCCPs have non-polar surfaces. The influence of pH on adsorption was studied in the pH range from 2 to 11. It was found that the adsorption capacity of HCCP-1DVB towards RIF reached maximum (162 mg/g) at pH = 7.2 (Fig. 8). This pH value is close to the isoelectric point of RIF (pI = 7.3) [39]. At the same time, the minimum values of adsorption capacity were 146 and 142 mg/g at pH equal to 2.1 and 11, respectively. Thus, the adsorption of RIF on HCCP-1DVB slightly depends on pH. It may be assumed that π-π stacking and hydrophobic interactions are the major driving forces for this process.
3.5. Effect of the adsorbent dosage on removal efficiency
The effect of the adsorbent (HCCP-1DVB) dosage on the RIF removal efficiency is illustrated in Fig. 9. The obtained data indicate that an increase in the HCCP-1DVB dosage leads to noticeable increase in removal efficiency of RIF. At an HCCP-1DVB dosage of 10 mg, the RIF removal efficiency was only 35%, but it increased up to 90% when the adsorbent dosage was equal to 50 mg. Finally, the removal efficiency was 99.8% at an adsorbent dosage of 80 mg.
The efficiency of RIF removal with HCCP-1DVB was also compared with the corresponding parameters for commercial hypercrosslinked adsorbents based on styrene-divinylbenzene copolymers (MN-200, MN-202, MN-270) of different porosities. As shown in Fig. 10, the RIF removal efficiency decreases in the order HCCP-1DVB (99.8%) > MN-200 (76.3%) > MN-202 (56.2%) > MN-270 (15.3%) when the adsorbent dosage is equal to 80 mg. The results obtained indicate that HCCP-1DVB can be used as an effective adsorbent for the removal of RIF from aqueous media.
3.6. Adsorbent reusability
An important characteristic of an adsorbent is the possibility of efficient regeneration and repeated use. Thus, HCCP-1DVB was filtered after equilibrium adsorption, and ethanol was employed as a regenerating agent. As illustrated in Fig. 11, after five adsorption-desorption cycles adsorption capacity of HCCP-1DVB was slightly reduced to 151 mg/g (93% of initial adsorption capacity), indicating that HCCP-1DVB has excellent reusability.
In this work, hypercrosslinked styrene copolymers with different contents of divinylbenzene were synthesized by the Friedel-Crafts reaction using CMME as an external crosslinker; their porous structure and adsorption characteristics towards RIF were studied. The surface area, pore volume, and pore structure of HCCPs depend on the DVB content in the polymer. The synthesized HCCPs have micropores and small mesopores (2–4 nm) in their structure. The mesopore volume of HCCPs increases with decreasing DVB content. Sample HCCP-1DVB has the maximum specific surface area (964 m2/g) and mesopore volume (0.53 cm3/g), which results in the best adsorption capacity towards RIF (qm = 183.27 mg/g). It was shown that the RIF adsorption increases with increasing mesopore volume of HCCPs. The RIF adsorption on HCCPs is a predominantly monolayer process; the adsorption kinetics is described by the pseudo-second-order model, and adsorption proceeds at a high rate. The RIF removal efficiency by the HCCP-1DVB copolymer is better (99.8%) than by the commercial hypercrosslinked adsorbents. HCCP-1DVB has good reusability; it retains 93% of its adsorption capacity after 5 cycles of use. The obtained results demonstrate that hypercrosslinked styrene copolymers with low DVB content may be considered as promising adsorbents for the removal of RIF from aqueous media.
Acknowledgments
The authors are grateful to Prof. V. A. Davankov and M. P. Tsyurupa for advices and fruitful discussions.
Funding information
No funding supports this study.
Data availability
Data is available upon requirement.
Conflict of interest
The authors have no conflict of interest to declare.
- Grobbelaar M, Louw GE, Sampson SL, van Helden PD, Donald PR, Warren RM (2019) Evolution of rifampicin treatment for tuberculosis. Infect Genet Evol. 74:103937. https://doi.org/10.1016/j.meegid.2019.103937
- Van Ingen J, Aarnoutse RE, Donald PR, Diacon AH, Dawson R, Plemper Van Balen G, Gillespie SH, Boeree MJ (2011) Why do we use 600 mg of rifampicin in tuberculosis treatment? Clin Infect Dis 52:194–199. https://doi.org/10.1093/cid/cir184
- Goldstein BP (2014) Resistance to rifampicin: A review. J Antibiot 67:625–630. https://doi.org/10.1038/ja.2014.107
- Li B, Zhang T (2010) Biodegradation and adsorption of antibiotics in the activated sludge process. Environ Sci Technol 44:3468–3473. https://doi.org/10.1021/es903490h
- Wang X, Li F, Hu X, Hua T (2021) Electrochemical advanced oxidation processes coupled with membrane filtration for degrading antibiotic residues: A review on its potential applications, advances, and challenges. Sci Total Environ 784. https://doi.org/10.1016/j.scitotenv.2021.146912
- Li D, Shi W (2016) Recent developments in visible-light photocatalytic degradation of antibiotics. Cuihua Xuebao/Chinese J Catal 37:792–799. https://doi.org/10.1016/S1872-2067(15)61054-3
- Ahmed MB, Zhou JL, Ngo HH, Guo W (2015) Adsorptive removal of antibiotics from water and wastewater: Progress and challenges. Sci Total Environ 532:112–126. https://doi.org/10.1016/j.scitotenv.2015.05.130
- Motamedi M, Mollahosseini A, Negarestani M (2022) Ultrasonic-assisted batch operation for the adsorption of rifampin and reactive orange 5 onto engineered zeolite–polypyrrole/TiO2 nanocomposite. International Journal of Environmental Science and Technology 19:7547–7564. https://doi.org/10.1007/s13762-022-03951-0
- Sun X, Chen M, Lei J, Liu X, Ke X, Liu W, Wang J, Gao X, Liu X, Zhang Y (2022) How β-cyclodextrin- loaded mesoporous SiO2 nanospheres ensure efficient adsorption of rifampicin. Front Chem 10. https://doi.org/10.3389/fchem.2022.1040435
- Cai W, Weng X, Chen Z (2019) Highly efficient removal of antibiotic rifampicin from aqueous solution using green synthesis of recyclable nano-Fe3O4. Environ Pollut 247:839–846. https://doi.org/10.1016/j.envpol.2019.01.108
- Shahrin EWES, Narudin NAH, Shahri NNM, Nur M, Lim JW, Bilad MR, Mahadi AH, Hobley J, Usman A (2023) A comparative study of adsorption behavior of rifampicin, streptomycin, and ibuprofen contaminants from aqueous solutions onto chitosan: Dynamic interactions, kinetics, diffusions, and mechanisms. Emerg Contam 9:100199. https://doi.org/10.1016/j.emcon.2022.100199
- Shafaati M, Miralinaghi M, Shirazi RHSM, Moniri E (2020) The use of chitosan/Fe3O4 grafted graphene oxide for effective adsorption of rifampicin from water samples. Res Chem Intermed 46:5231–5254. https://doi.org/10.1007/s11164-020-04259-9
- Kais H, Yeddou Mezenner N, Trari M (2020) Biosorption of rifampicin from wastewater using cocoa shells product. Sep Sci Technol 55:1984–1993. https://doi.org/10.1080/01496395.2019.1623255
- Liu Q, Wang L, Yu W, Xiao A, Yu H, Huo J (2010) Hypercrosslinked polystyrene microspheres with bimodal pore size distribution and controllable macroporosity. J Appl Polym Sci 116:84–92. https://doi.org/10.1002/app.31422
- Gan Y, Chen G, Sang Y, Zhou F, Man R, Huang J (2019) Oxygen-rich hyper-cross-linked polymers with hierarchical porosity for aniline adsorption. Chem Eng J 368:29–36. https://doi.org/10.1016/j.cej.2019.02.164
- Dmitrienko SG, Tikhomirova TI, Apyari VV, Tolmacheva VV, Kochuk EV, Zolotov YA (2018) Application of hypercrosslinked polystyrenes to the preconcentration and separation of organic compounds and ions of elements. J Anal Chem 73:1053–1063. https://doi.org/10.1134/S1061934818110047
- Davankov VA, Tsyurupa MP (2011) Hypercrosslinked polymeric networks and adsorbing materials. Synthesis, properties, structure and application. Elsevier, Amsterdam
- Pastukhov AV, Tsyurupa MP, Davankov VA (1999) Hypercrosslinked polystyrene: a polymer in a non-classical physical state. J Polym Sci Part B Polym Phys 37: 2324–2333. https://doi.org/10.1002/(SICI)1099-0488(19990901)37:17<3C2324::AID-POLB4>3E3.0.CO;2-B
- Li A, Zhang Q, Zhang G, Chen J, Fei Z, Liu F (2002) Adsorption of phenolic compounds from aqueous solutions by a water-compatible hypercrosslinked polymeric adsorbent. Chemosphere 47:981–989. https://doi.org/10.1016/S0045-6535(01)00222-3
- Ding L, Zhang A, Li W, Bai H, Li L (2016) Multi-length scale porous polymer films from hypercrosslinked breath figure arrays. J Colloid Interface Sci 461:179–184. https://doi.org/10.1016/j.jcis.2015.09.031
- Joseph R, Ford WT, Zhang S, Tsyurupa MP, Pastukhov AV, Davankov VA (1997) Solid-state 13C-NMR analysis of hypercrosslinked polystyrene. J Polym Sci Part A Polym Chem 35:695–701. https://doi.org/10.1002/(SICI)1099-0518(199703)35:43C<695::AID-POLA12>3E3.0.CO;2-I
- Veverka P, Jeřábek K (1999) Mechanism of hypercrosslinking of chloromethylated styrene-divinylbenzene copolymers. React Funct Polym 41:21–25. https://doi.org/10.1016/S1381-5148(99)00030-9
- Fontanals N, Cormack PAG, Sherrington DC (2008) Hypercrosslinked polymer microspheres with weak anion-exchange character. Preparation of the microspheres and their applications in pH-tuneable, selective extractions of analytes from complex environmental samples. J Chromatogr A 1215:21–29. https://doi.org/10.1016/j.chroma.2008.10.124
- Ahn JH, Jang JE, Oh CG, Ihm SK, Cortez J, Sherrington DC (2006) Rapid generation and control of microporosity, bimodal pore size distribution, and surface area in Davankov-type hyper-cross-linked resins. Macromolecules 39:627–632. https://doi.org/10.1021/ma051152n
- Fontanals N, Marcé RM, Borrull F, Cormack PAG (2015) Hypercrosslinked materials: Preparation, characterisation and applications. Polym Chem 6:7231–7244. https://doi.org/10.1039/c5py00771b
- Long C, Li A, Wu H, Zhang Q (2009) Adsorption of naphthalene onto macroporous and hypercrosslinked polymeric adsorbent: Effect of pore structure of adsorbents on thermodynamic and kinetic properties. Colloids Surf A Physicochem Eng Asp 333:150–155. https://doi.org/10.1016/j.colsurfa.2008.09.037
- Azanova V V, Hradil J (1999) Sorption properties of macroporous and hypercrosslinked copolymers. React Funct Polym 41:163–175. https://doi.org/10.1016/S1381-5148(99)00029-2
- Li B, Gong R, Luo Y, Tan B (2011) Tailoring the pore size of hypercrosslinked polymers. Soft Matter 7:10910–10916. https://doi.org/10.1039/c1sm06113e
- Popov AY, Blinnikova ZK, Tsyurupa MP, Davankov VA (2018) Hypercrosslinked polymeric restricted access materials for analysis of biological fluids. J Sep Sci 41:3302–3309. https://doi.org/10.1002/jssc.201800528
- Berliner MA, Belecki K (2005) Simple, rapid procedure for the synthesis of chloromethyl methyl ether and other chloro alkyl ethers. J Org Chem 70:9618–9621. https://doi.org/10.1021/jo051344g
- Bartholin M. Boissier G, Dubois J (1981) Styrene-divinylbenzene copolymers, 3. Revisited IR analysis. Makromol Chem 182:2075–2085. https://doi.org/https://doi.org/10.1002/macp.1981.021820719
- Tsyurupa MP, Blinnikova ZK, Davidovich YA, Lyubimov SE, Naumkin AV, Davankov VA (2012) On the nature of “functional groups” in non-functionalized hypercrosslinked polystyrenes. React Funct Polym 72:973–982. https://doi.org/10.1016/j.reactfunctpolym.2011.03.002
- Thommes M, Kaneko K, Neimark AV, Olivier JP, Rodriguez-Reinoso F, Rouquerol J, Sing KSW (2015) Physisorption of gases, with special reference to the evaluation of surface area and pore size distribution (IUPAC Technical Report). Pure Appl Chem 87:1051–1069. https://doi.org/10.1515/pac-2014-1117
- Chung HK, Kim WH, Park J, Cho J, Jeong TY, Park PK (2015) Application of Langmuir and Freundlich isotherms to predict adsorbate removal efficiency or required amount of adsorbent. J Ind Eng Chem 28:241–246. https://doi.org/10.1016/j.jiec.2015.02.021
- Lima EC, Hosseini-Bandegharaei A, Moreno-Piraján JC, Anastopoulos I (2019) A critical review of the estimation of the thermodynamic parameters on adsorption equilibria. Wrong use of equilibrium constant in the Van’t Hoof equation for calculation of thermodynamic parameters of adsorption. J Mol Liq 273:425–434. https://doi.org/10.1016/j.molliq.2018.10.048
- Ghosal PS, Gupta AK (2017) Determination of thermodynamic parameters from Langmuir isotherm constant-revisited. J Mol Liq 225:137–146. https://doi.org/10.1016/j.molliq.2016.11.058
- Ho YS, McKay G (1999) Pseudo-second order model for sorption processes. Process Biochem 34:451–465. https://doi.org/10.1016/S0032-9592(98)00112-5
- Lagergren S (1898) About the theory of so-called adsorption of soluble substances. Svenska vetenskapsakademien Handlingar 24:1–39.
- Khan MF, Rita SA, Kayser MS, Islam MS, Asad S, Bin Rashid R, Bari MA, Rahman MM, Al Aman DAA, Setu NI, Banoo R, Rashid MA (2017) Theoretically guided analytical method development and validation for the estimation of rifampicin in a mixture of isoniazid and pyrazinamide by UV spectrophotometer. Front Chem 5:. https://doi.org/10.3389/fchem.2017.00027
Scheme 1 is available in the Supplementary Files section.
- Scheme1.png
Scheme 1Preparation of HCCPs
