Statistical optimization of process conditions for pyrvinium pamoate elimination using UV/zeolite‐based nanostructures/H 2 O 2

Abstract

Anthelmintic drugs such as mebendazole, niclosamide, albendazole, pyrantel, pyrvinium etc. have been applied to kill the helminthes, worm-like parasites such as flukes, roundworms, and tapeworms, in humans and livestock [1, 2]. Pyrvinium pamoate as a quinoline-derived cyanine dye, has been used to treat pinworm, nematode, or a roundworm infection in humans [3, 4]. This drug as an FDA-approved classical anthelmintic, can be useful for cancer therapy, antitumor activity [3, 5, 6]. During the past decades a wide range of these compounds as well as other pharmaceuticals have been described as emerging environmental contaminants [7-10]. High levels of pharmaceutical compounds have been discovered in sewage, sludge fields, surface water, groundwater, and even drinking water [11]. The majority of the adverse effects of toxic organic micro-pollutants has increased the requirement of the complete removal of these contaminants from the aquatic environment [12]. Different procedures such as physical approaches (flocculation, adsorption, coagulation, and membrane filtration, etc.), chemical approaches (electrochemical treatment and ozonation), and biological methods (using microorganisms and/or enzymes) have been applied for degradation of dyes and drugs [13, 14]. Advanced oxidation processes (AOPs), such as Fenton's oxidation, ozonation, photocatalytic oxidation, and sonolysis have been widely used for treatment of wastewaters [15-18]. AOPs have related to the ultraviolet light and semiconductors such as titanium dioxide (TiO2) and zinc oxide (ZnO) etc. and applied for the change of molecules and the formation of hydroxyl radicals (OH) [17, 19, 20]. In general, photocatalytic oxidation together with ultraviolet radiation formed a redox environment in the aqueous solution and usually decomposed the undesired contaminant into water [21, 22]. Investigation of photocatalytic methods by using the photo-catalysts such as TiO2, ZnO, WO3, Fe2O3, ZnS, and CdS have included in the previous studies for the removal of pollution resources from wastewaters [17, 23]. For example, Jiang et al. [24] described about photocatalytic degradation of dimethyl phthalate by TiO2 coated glass microspheres–UV irradiation process. In the other study done by Zhang et al. [25], the photo-catalyst nano-TiO2 has been successfully applied for the degradation of chloramphenicol under UV irradiation [25]. Zeolites as crystalline aluminosilicates with 3D microporous structure, which attracted great attentions due to their unique properties such as ion exchangeability, high thermal, mechanical, and chemical stability, high capacity for catalytic reactions. The uses of zeolites for removal of pharmaceuticals from wastewaters have been reported in the last decades [26-28]. For example, Li et al. [27] applied the HZSM-5 zeolite supported boron-doped TiO2 for photocatalytic degradation of ofloxacin. Liu et al. [28] also used novel CoS2/MoS2@Zeolite for tetracycline removal in wastewater. The statistical and mathematical methods have successfully been applied to determine the optimal conditions for a variety of processes [8, 9, 24, 25]. In the study of Farzadkia et al. [11], the influences of some effective parameters, such as varying of pH value, nano-ZnO loading amount, UV-A light time, and intensity of radiation on the degradation efficiency of metronidazole in aqueous solution were discussed through photocatalytic trials using nano-ZnO as the photo-catalyst [11]. Optimization of photocatalytic degradation of phenazopyridine under UV light irradiation using immobilized TiO2 nanoparticles studied by Fathinia and Khataee [29]. In the present study the potential ability of the synthesized zeolite-based nanostructures for elimination of pyrvinium pamoate (PP) in the presence of UV light and H2O2 was evaluated. For this purpose, response surface methodology (RSM), a mathematical and statistical technique, was applied for the optimization of the removal process of PP and determines the optimum operational condition of the removal (%) by a predictive model. Pyrvinium pamoate was purchased from Aboureihan Pharmaceuticals Co. (Tehran, Iran). Sodium hydroxide, silicon dioxide, sodium aluminate, and hydrogen peroxide (H2O2) solution (30 wt%) were obtained from Merck chemicals (Darmstadt, Germany). All other chemicals and the used solvents were of analytical grade. In order to synthesize zeolite-based nanostructures, 5 mL sodium hydroxide (2 m) was added to a 50 mL round bottom balloon and 0.05 g silicon dioxide was added to the above solution until clarified completely. In the next step, the obtained silicate solution was slowly added to the alumina solution (0.1 mm) to form a clear white gel. The formed white gel was then transferred to a 250 mL container and exposed to microwave irradiation in a domestic microwave oven operating at 2,450 MHz for different output such as 600 and 300 W for 15 min. Then, the solution was transferred to an autoclave and heated at 200°C for 6 h. Then, to eliminate the alkalinity, the solution was passed through a filter paper and washed several times with deionized water. The pH of the solution was measured after each washing step until the solution reached a dull state and the pH adjusted to approximately 7. The remaining precipitate from the washed solution was transferred to a glass filter on a filter paper and kept aside for 9 h. At the final step, the precipitates were dried in vacuum at 50°C for 48 h. XRD patterns of as-synthesized zeolite-based nanostructures were collected from a diffractometer of Philips company with X'PertPro monochromatized Cu Ka radiation (k = 1.54 A°). Microscopic morphology of the products was visualized by a LEO 1455VP scanning electron microscope (SEM) operated at 20 keV. The synthesized zeolite-based nanostructures were examined for removal of PP by direct irradiation of UV light in a UV cabinet equipped by three 15 W UV lamps with wavelength of 254 nm (Philips, Holland) which sited in 25 cm on the top and behind the batch photoreactor [8, 30]. The reaction mixture was prepared by mixing PP solution of different concentrations (5−100 μg/mL) with the altered doses of nanostructure solution (0.5−5 μg/mL) and hydrogen peroxide (0−5 mm). The prepared mixtures were continuously stirred for 60 min in the presence of UV light (15−30 W/m2) and samples then taken each 15 min for 60 min. The nanocatalyst was then removed by centrifugation (8,000 × g for 5 min) and filtration (0.22 μm filters). The concentration of PP in samples was monitored using a Shimadzu UV–vis Double Beam PC Scanning spectrophotometer (UV-1800, Shimadzu CO, USA) at maximum absorbance of 507 nm (Figure 1). The experimental design technique, response surface methodology (RSM), was employed to optimize the removal process [8, 25, 31]. The removal effectiveness of pyrvinium pamoate was assessed using D-optimal design. Four factors were chosen including nanostructure dose (1−2 μg/mL), drug concentration (10−50 μg/mL), hydrogen peroxide concentration (0−1 mm), and light intensity (15−30 W/m2) (Table 1). XRD pattern of the as-synthesized zeolite-based nanostructures sample is shown in Figure 2. It can be seen from the XRD pattern that crystallinity phase shows the formation of structures in a completely pure way. No other crystalline phases were detected in the heated sample. The diffraction peaks of the as-synthesized zeolite-based nanostructures were matched with the signals of standards including Na2CO3 (JCPDS No. 00-018-1208), NaNO3 (JCPDS No. 01-070-1518) and Na3H (CO3)2.2H2O (JCPDS No. 01-078-1064) (Figure 2). Talebian-Kiakalaieh and Tarighi [32] synthesized and characterized the initially parent NaY and ZSM-5 zeolites. All XRD patterns demonstrated the high crystallinity of obtained zeolites without any amorphous phase. Ahmadi et al. [33] showed the characteristic peaks of zeolite NaY at 2 theta 6.1°, 11.8°, 15.5°, and 23.4°. Selim et al. [34] prepared the Na-A zeolite from aluminium scrub and sodium silicate and revealed the formation of pure Na-A zeolite without interference of other crystalline by-products [34]. Microscopic images show that samples are nanometre-sized and generally formed on a regular, uniform substrate (Figure 3). Ramezani et al. [35] synthesized NaY zeolite and revealed the formation of well-shaped crystals with an approximate size of 1 μm. Ameri et al. [36] observed the faujasite and hexagonal shapes for NaY and ZSM-5 zeolite, respectively, in the SEM images [36]. FESEM images of NH4Y zeolite, and amorphous silica–alumina assessed by Aghakhani et al. [37]. The NH4Y zeolite showed the agglomerated particles with smooth surface and sharp edges having average particle size of 0.7 μm while silica–alumina displayed rough surface irregular agglomerates with sizes in the range of 0.2–2 μm [37]. TEM analysis was used to further investigate the surface properties of zeolite-based nanostructures. According to the TEM image it can be concluded that the porous structures were well formed. The average pore size is below 50 nm. TEM image of the as-synthesized zeolite-based nanostructures is shown in Figure 4. In order to study the porosity of as-synthesized zeolite-based nanostructures, the Brunauer–Emmett–Teller (BET) analysis was used. The obtained data through the BET and BJH with the adsorption/desorption isotherm method demonstrate that cross section area, total pore volumes and dead volume were calculated 0.162 nm2, 0.062 cm3/g, and 17.442 cm3, respectively. BET analysis of the as-synthesized zeolite-based nanostructures is shown in Figure 5. It seems that with increasing the amount of porosity at the level of zeolite structures, these porosities are evenly distributed at the surface of the sample. Energy-dispersive X-ray spectroscopy (EDX) elemental mapping was used to show the distribution of elements within some selected area as a complement to the SEM analysis in the distribution of the as-synthesized zeolite-based nanostructures. The EDX elemental mapping is shown in Figure 6. In this example, the number of elements formed with a uniform scattering distribution. There is a small amount of Ti as impurities in the sample. At first, the effects of each parameter were individually assessed on the removal of PP and thus, the parameters, such as the initial concentration of PP, existence of zeolite-based nanostructures, the presence of UV light irradiation, UV light intensity, the presence of H2O2, and irradiation time were solely evaluated on the elimination of PP in solution. The obtained results showed that the total parameters have the positive effects on the removal process. So, these factors were selected for the optimization of removal conditions of PP using RSM. However, the irradiation time was considered to be constant during the PP removal process (15 min). These results were in accordance with the results reported by Samara et al. [38], who showed that the photodegradation in the absence of a catalyst resulted in changes of the peak intensity under 302-nm UV light. Wang et al. [26] assessed the effective degradation of sulfamethoxazole by Fe2+-zeolite/peracetic acid, and reported that the increase in Fe2+-zeolite/peracetic acid dosage enhanced the degradation of sulfamethoxazole. Sturini et al. [39] evaluated the photocatalytic removal for the degradation of ofloxacin from polluted water. They found that the highest degradation rate (95%) obtained in the presence of undoped composites, the synthesized sepiolite–TiO2 (ST-1) and the synthesized zeolite–TiO2 (ZT) [39]. Before performing of the experimental design, initial experiments (selected as one factor study) were accomplished to evaluate the effect of each parameter on PP elimination. Results obtained by individual factors including the elimination in the absence of UV light (in the presence of zeolite-based nanostructures and dark conditions), photolysis (UV light irradiation), and photodegradation (assisted by UV/zeolite-based nanostructures) for a time period of 90 min proved that factors of UV light intensity, irradiation time, and existence of zeolite-based nanostructures positively affected the elimination of PP. So, these factors were selected for the optimization of PP elimination using UV/zeolite-based nanostructures/H2O2. However, the radiation time was remained constant (15 min) during the removal processes of PP. The graphical tools were applied for diagnostics of the normal distribution of data. The residuals versus the predicted plot were the residuals versus the ascending predicted response values. As shown in Figure 7a, the plot must have a random scatter, which is appropriate for continuing analysis. Figure 7b represents a graph of the actual response values versus the predicted response values. The data points should be split evenly by the 45° line. It can be seen that there was a high correlation between the predicted and experimental PP removal (%). The relationship between factors and PP removal (%) was investigated by 3D surface plots. Figure 8a shows the effect of H2O2 concentration and nanostructure dose on pyrvinium pamoate removal (%), while factors such as drug concentration and light intensity were kept at their centre points. As can be seen in the plot, the PP removal (%) improved with increase in nanostructure dose from 1 to 2 μg/mL. However, the removal of PP decreased with the increase in H2O2 concentration (Figure 8a). In the study performed by Zhang et al. [25], they found that the degradation rate of chloramphenicol was 85.97% under optimal conditions especially at TiO2 concentration of 0.94 g/L. Gupta et al. [9] reported that the maximum quinoline degradation efficiency (about 92%) obtained at the optimum condition of 400°C calcination temperature, 8 pH, 1:1 ZnO:TiO2 molar ratio, 50 mg/L initial quinoline concentration, and 2.5 g/L catalyst dose [9]. Photocatalytic degradation of 2,3,7,8-tetrachlorodibenzofuran (2,3,7,8-TCDF) evaluated by Samara et al. [38]. They also applied the both types of silver zeolite (AgY1 and AgY2) to degrade 2,3,7,8-TCDF. The amount of the adsorbed 2,3,7,8-TCDF on AgY1 and AgY2 catalyst was 37.9% and 18.9%, respectively [38]. In general, the amount of catalyst has affected on the degradation efficiency due to provide a greater number of actives sites. Therefore, an enhancement in the amount of catalyst has led to increase in the number of •OH radicals, which produced more free electrons [8, 9]. The effects of the light intensity and H2O2 concentration (other factors such as drug concentration and nanostructure dose were at centre points) on the removal (%) of PP are shown in Figure 8b. The results show that the PP elimination (%) increased with the increasing of light intensity (Figure 8b). Indeed, this behaviour is as an indication of producing the activated •OH and the atomic oxygen due to absorbed UV light energy via H2O2 and O─O bond. The created molecular oxygen, an electron acceptor, operates for the avoidance of recombination of electrons and holes during the photochemical process [17, 40, 41]. When, the higher light intensity was used for the degradation process, the more electron–hole pairs were created by photocatalyst elements [17, 40, 41]. Since the same study reported by Trapido et al. [42] for diclofenac degradation. They applied the several protocols such as UV photolysis, H2O2/ photolysis, and Fenton/photo-Fenton treatment for the diclofenac degradation and reported that the UV photolysis was the main pathway for diclofenac degradation. Achilleos et al. [40] applied the hydrogen peroxide as an oxidizer on diclofenac degradation. They found that the ratio of H2O2 to drug concentration influenced the rate of degradation. Samy et al. [43] synthesized the nanocomposites of carbon nanotubes/lanthanum vanadate for the photocatalytic degradation of a sulfamethazine and optimized the degradation parameters such as solution pH, catalyst dose and light intensity using a central composite design. The predicted and experimental sulfamethazine removal rates were 95.54% and 96.2%, respectively, in the optimum parameters obtained 3.0 (pH), 0.2495 g/L (catalyst dose), and 152.727 W/m2 (light intensity). Apollo et al. [44] assessed a UV/H2O2/TiO2/Zeolite combined system for treatment of molasses wastewater and achieved the highest decolorization in the order H2O2/UV/TiO2/zeolite > H2O2/UV/TiO2 > UV/TiO2 > H2O2/UV system [44]. The effect of drug concentration and nanostructure dose, while factors such as H2O2 concentration and light intensity were at centre points, on PP removal (%) is presented in Figure 8c. It can be observed that nanostructure dose had a major effect on the response, with a high increase in PP removal for high nanostructure dose (2 μg/mL) (Figure 8c). When, an increase in drug concentration from 10 μg/mL to 50 μg/mL decreased the elimination of PP from 65.00% to 60.20%, at high nanostructure dose (2 μg/mL). As observed, at high concentration of drug (50 μg/mL) and in the presence of low dose of nanostructure (1 μg/mL), the PP removal (%) was occurred 53.15% (Figure 8c). Mostafaloo et al. [45] optimized the degradation parameters of ciprofloxacin by BiFeO3 nanocomposites using RSM. The maximum ciprofloxacin removal (100%) obtained at pH 6, initial ciprofloxacin concentration of 1 mg/L, BiFeO3 dosage of 2.5 g/L, and at 30°C for 46 min. They found that the removal efficiency enhanced at low level of ciprofloxacin and at high level of BiFeO3. Apollo et al. [44] reported that when the molasses concentration increased from 1 to 20 g/L, the degradation efficiencies decreased from 57% to 49%, respectively [44]. In the other study of Gupta et al. [9], the initial quinoline concentration (ranging from 50 to 500 mg/L) evaluated for photocatalytic degradation of quinoline. They observed that increasing the concentration of quinoline from 50 to 500 mg/L, the degradation rate reduced from 81.2% to 45.3%, respectively [9]. Figure 8d illustrates the effects of nanostructure dose and light intensity on PP removal efficiencies. As shown in from Figure 8d, the highest removal percent of PP (62.85%) obtained when the nanostructure dose and light intensity were 2 μg/mL and 24 W/m2, respectively. Similar observations were reported by Li et al. [27], who applied HZSM-5 zeolite supported boron-doped TiO2 with ultraviolet irradiation for photocatalytic degradation of ofloxacin [27]. The photocatalytic degradation of tetracycline using a series of CoS2/MoS2@Zeolite photocatalysts showed that CoS2/MoS2@Z-50 was the most effective photocatalyst. Nenavathu et al. [46] found that there is the significant difference between removal of trypan blue with and without UV light irradiation using Se-doped ZnO NPs [46]. Generally, an enhancement of electron–hole pairs generation and an increase of the hydroxyl radical formation depends on the higher energy obtained from UV light intensity, which led to enhancement of removal efficiency [17, 31]. The adequacy of the model was validated under the optimal conditions obtained from D-optimal design (Table 4). Experimental PP removal (%) was found 70.14±1.71% at the optimal conditions. Also predicted PP removal (%) was calculated 72.25 ± 1.23% at the optimal conditions. According to results, verification experiments confirmed the validity of the predicted model (Table 4). Based on Figure 9, the PP removal (%) was increased (97.67 ± 1.1%) with enhancement of irradiation time of 15 to 60 min. X1: 2.00 μg/mL X2: 10.00 μg/mL X3: 0.00 mm X4: 22.50 W/m2 The present study was designed to assess the elimination of PP in the presence of the synthesized zeolite-based nanostructures assisted by UV light radiation in the aqueous solution. Statistical method, D-optimal design, was applied to optimize the essential components for elimination. The effect of four factors including nanostructure dose, drug concentration, H2O2 concentration, and light intensity were evaluated on removal efficiency of PP. Among the total variables, nanostructure dose, and light intensity were significantly showed positive effects on PP removal (p < 0.05), while H2O2 concentration, and drug concentration had negative effect (p < 0.05). Lastly, the best optimum conditions for maximum elimination of PP (70.14 ± 1.71%) was experimentally reached at nanostructure dose of 2.00 μg/mL, drug concentration of 10.00 μg/mL, H2O2 concentration of 0.00 mm, light intensity of 22.50 W/m2, which was very near to the predicted amount (72.25 ± 1.23%). The PP removal (%) was also increased (97.67 ± 1.1%) with the enhancement of irradiation time of 15–60 min. The obtained results confirmed the potential application of zeolite-based nanostructures in the presence of UV light radiation for elimination of the PP. However, more studies are needed to investigate the related mechanism(s) on this process and to identify the probable by-products. Research reported in this publication was supported by Elite Researcher Grant Committee under award number [982564] from the National Institute for Medical Research Development (NIMAD), Tehran, Iran. The authors declare no conflict of interest. None Research reported in this publication was supported by Elite Researcher Grant Committee under award number [982564] from the National Institute for Medical Research Development (NIMAD), Tehran, Iran. Furthermore, we thank the Pharmaceutics Research Center, Institute of Neuropharmacology, Kerman University of Medical Sciences (Kerman, Iran). The data that support the findings of this study are available from the corresponding author upon reasonable request.