Removal and degradation of triazole fungicides using Ag/PEG-CuO: an efficient adsorbent-catalyst coupling process

ABSTRACT In this work, an effective adsorbent-catalyst coupling (ACC) process is proposed and investigated to treat the wastewater polluted with triazole fungicides. In this regard, PEG-CuO as well as Ag particles were prepared and used as the adsorbent and catalyst in the ACC process, respectively. For comparison purposes, Fe3O4 was also utilised as a catalyst. The experiments were conducted to remove penconazole, hexaconazole, and diniconazole (as representative fungicides which were analysed by HPLC-UV). The results show that sole catalysts could not completely remove the triazole fungicides. However, it was found that complete removal and degradation of all fungicides can be obtained using the ACC approach. In the next step, the effects of important operating parameters of the ACC process, i.e. adsorbent load, catalyst load, ratio of catalyst to adsorbent, salt concentration, pH, and operation time were studied. It was found that the optimum condition for all the fungicides was 50/50 ratio of Ag/PEG-CuO, pH of 7, and operating time of 85 min. Finally, the ACC process capability was evaluated for the treatment of five real wastewaters containing triazole fungicides, and the excellent performance of this process was confirmed by observing the complete removal and degradation.


Introduction
In recent years, the appearance of various pollutants in surface water raised concerns about the contamination of water resources which can seriously affect the quality of drinking water and cause long term health issues [1].Since the production of drinking water from surface water is a suitable approach from the sustainable development point of view, appropriate treatment of surface water is critical for societies [2,3].Some agriculture approach consumes different chemicals in the form of fertilisers and pesticides.The runoff of these chemicals into surface or ground water contaminates the water resources and adversely affects the quality of drinking water [4][5][6].Pesticides consist of different classes including insecticides, fungicides, herbicides, and rodenticides.Triazole-based compounds like penconazole, hexaconazole, and diniconazole are among the most important fungicides [7,8].Using triazoles in agriculture is utilised to fight a variety of pests that could destroy crops [9].Triazoles can be directly utilised in the soil or sprayed over crop fields that pollute water resources [10].The treatment of these pollutions from water resources is one of the nowadays challenges.Various methods can be employed to treat the fungicides like hydrolysis [11], biodegradation [12], photodegradation [13], adsorption [14], and catalytic degradation [15].Effective adsorbents and catalysts can be employed in many cases to solve water treatment issues.As an efficient example Polyethylene Glycol-CuO (PEG-CuO) can be used for water purification because of its excellent adsorption capability [10,16].Utilising PEG as a well-known template for catalyst synthesis not only improves the surface area of catalyst but also hinders catalyst aggregation [17,18].The metallic nanoparticles (NPs) such as iron oxide and silver can demonstrate high catalytic activity at ambient temperature that introduces them as promising catalysts for water treatment [19][20][21].For example, Fe 3 O 4 displayed strong ability in the degradation of compounds [16,22].The structure of Fe 3 O 4 includes both Fe 2+ and Fe 3+ ions; the former can play an important role as an electron donor in the degradation of fungicides [23].Ag-NPs were also incorporated to remove pollutants like pesticides, heavy metals, and microorganisms from wastewater [24].
The metallic NPs can be synthesised by several physical, chemical, and biological methods [25].Green synthesis of NPs has some advantages over conventional methods such as being environmentally friendly and cost effective [21,26], and employing the natural resources in the synthesis of materials is a promising approach from a sustainable development point of view.Natural sources like plants, bacteria, fungi, yeast, and honey have been used for synthesising metallic NPs [27].For example, plant source biomolecules can reduce Ag + ions from silver nitrate to form silver NPs [25].
Preparation of a dual functional adsorbent/catalyst system has already been proposed for the removal of volatile organic compounds (VOCs) [28,29].This approach is interesting because a single material can simultaneously act as adsorbent and catalyst.However, it is not usually efficient in practice, because a single material cannot often simultaneously exhibit the expected specifications of effective adsorbent and catalyst.Therefore, previous research was usually using individual adsorbent for the removal or catalyst for the degradation of pollutants [15,30,31].To the best of our knowledge, no work has been performed on an adsorbent-catalyst coupling (ACC) process for the treatment of fungicides and pesticides.
In this paper, for the first time, an efficient ACC process is proposed for the removal and degradation of three triazole fungicides in wastewater.Penconazole, hexaconazole, and diniconazole were selected as representative fungicides.In this regard, PEG-CuO was first prepared and used as adsorbent.On the other hand, Ag-NPs were prepared and employed as a catalyst and for comparison purposes; Fe 3 O 4 was used as another catalyst.Afterwards, the capability of ACC process (using Ag/PEG-CuO and Fe 3 O 4 /PEG-CuO) to degrade the triazole fungicides was examined.Moreover, effects of the main operating parameters of this process, i.e. amount of PEG-CuO, Fe 3 O 4 , and Ag, as well as ratio of adsorbent (PEG-CuO) to catalyst (Fe 3 O 4 or Ag), salt concentration, pH, and operation time on the removal and degradation efficiencies were studied.Finally, five real wastewaters containing triazole fungicides were treated using the prepared materials at the obtained optimum condition to evaluate the capability of the present ACC process.

Synthesis of PEG-CuO
PEG-CuO was synthesised using a hydrothermal technique similar to introduced in our previous study [10].In this method, Cu(NO 3 ) 2 .3H 2 O solution was prepared by dissolving 3.159 g of copper (II) nitrate in deionised water (25 mL) and was then added to NH 4 HCO 3 solution (30 mL, 2 mol/L) under vigorously stirring to observe intense blue precipitates.A 0.22 µm membrane and distilled water were utilised to vacuum filter and wash the precipitate before 1.5 h of stirring, respectively.The obtained suspension was added into PEG solution (80 mL, 5 wt.%) and then stirred for 30 min at a constant temperature of 60°C to completely ensure the PEG dissolution.Afterwards, the suspension was poured into a 100 mL Teflon-lined stainless autoclave and heated in an oven (170°C, 24 h) leading to the PEG's attachment onto the prepared CuO surface.After cooling the suspension up to room temperature, the deionised water as well as absolute ethanol were repeatedly conducted to wash the black produced precipitate.The resulted sample was subsequently dried in a vacuum oven at 100°C for 6 h.

Preparation of Ag by green method
Amaranthus Retroflexus leaf was used as a bio-source reducing agent in the preparation of Ag-NPs as by Bahrami-Teimoori et al. [32].After thoroughly washing 5 g of leaf by deionised water, it was dried and cut into fine pieces.To make leaf extract, the mixture was mixed with 100 mL of deionised water in an Erlenmeyer flask and then boiled for 5 min at 100°C.The mixture was then cooled and filtered through Grade 1 Whatman filter paper.1.0 ml of the obtained extract was added to 9.0 ml of silver nitrate (1.0 mM) at room temperature leading to turning the mixture from colourless to reddish brown as a consequence of the reducing Ag + to Ag 0 .The reduced solution was then centrifuged and washed three times at 12,000 rpm for 15 min.The obtained pellet was dried in a vacuum oven and the dried Ag-NPs were then scrapped out.

Characterisation techniques
The structure and morphology of the prepared material were analysed by scanning electron microscopy (SEM, LEO 1450VP) and transmission electron microscopy (TEM, Phillips CM10).Fourier-transform infrared spectroscopy (FT-IR) analysis was performed using a FT-IR spectrometer (Thermo Nicolet, Avatar 370) to evaluate the functional groups on the surface of prepared materials.The X-ray diffraction (XRD) patterns of materials were collected by a Philips (X'pert Pro MPD) X-ray diffractometer with a Cu Kα radiation source.

Treatment of fungicides polluted water
PEG-CuO/Fe 3 O 4 or PEG-CuO/Ag were employed for the removal and degradation of fungicides as follows: Firstly, the required amount of prepared PEG-CuO (as adsorbent) as well as Fe 3 O 4 or Ag (as the catalyst) were dispersed into 8 mL of the wastewater which contains 5 ppm of fungicides (penconazole, hexaconazole, or diniconazole), in a 10 mL centrifuge tube.Secondly, the suspension was agitated by vortex mixer (for the determined time) to remove and degrade the fungicides.It should be mentioned that all experiments were conducted for 85 min, except the ones corresponding to the study of operation time's effect.Subsequently, the particles were separated from the solution by centrifugation (4000 rpm for 10 min).The supernatant was filtered through a 0.45-μm membrane and transferred into a 1.5 mL vial.In order to determine the amounts of removed fungicides from the wastewater, the filtered supernatant was analysed by a HPLC-UV.
On the other hand, the adsorbed fungicides on the separated particles (from the wastewater) were desorbed using methanol (as an extracting solvent).To do so, 1.5 ml of methanol was added to the separated Fe 3 O 4 /PEG-CuO or Ag/PEG-CuO, and the mixture was then mixed for 10 min to desorb the fungicides.The prepared mixture was centrifuged at 4000 rpm for 10 min.The obtained solution was analysed by the HPLC-UV to measure the amounts of desorbed fungicides (the fungicides which were removed from the wastewater sample, but not degraded by the catalyst).Accordingly, the amounts of degraded fungicides were calculated by subtracting the desorbed amounts of fungicides from the removed fungicides (measured from the supernatant).Each experiment was repeated five times and the relative standard deviation (RSD) analysis was performed.Figure 1a presents a schematic diagram of the experimental procedure and Figure 1b illustrates removal and degradation definition by mentioned catalysts and adsorbent.Furthermore, the recycling study was conducted to investigate the reusability of the Ag/PEG-CuO for diniconazole removal.It was examined for 4 cycles under optimum operating condition.

HPLC analysis method
Liquid chromatographic analysis carried out using a Waters 600 E (Millipore, Milford, MA, USA), LC 600 pump, C 1 Cheminert injector valve provided with a 20 µL sample loop (Switzerland) and a Waters 486 tunable UV-Vis detector.The analysis was performed at 22°C on a C18 analytical column (4.6 mm×150 mm, 5 µm).A 70% (v/v) of methanol solution in water was utilised as mobile phase under a flow rate of 1.0 mL/min and 220 nm was adjusted as the wavelength of UV detection.

Real wastewater
Real fungicide polluted wastewaters were obtained by washing different vegetables (including cucumber, lettuce, bell pepper, cabbage, and tomato) which were taken from local markets (Mashhad, Iran).In order to determine the type and concentration of fungicide residues in the wastewaters, standard solutions (5 ppm) of triazole compounds (namely, penconazole, hexaconazole, and diniconazole) were used as standard.The standard solution peak area was utilised to prepare calibration curves and find the amounts of triazole compounds in the wastewater before and after the treatment process by the HPLC-UV.

Characterisation of the prepared samples
Figure S1a depicts the SEM back scatter analysis of the prepared PEG-CuO which confirms its flower-like shape.Figure S1b shows a TEM image of the biosynthesised Ag-NPs.In this figure, Ag-NPs can be seen in the form of black spheres with an average size of about 25 nm. Figure S2 illustrates FT-IR spectra of the prepared PEG-CuO and Ag.As can be seen, absorption bands are available at 417 and 1030 cm −1 for PEG-CuO spectrum which are ascribed to the asymmetric and symmetric stretching frequency of Cu-O-Cu vibrational bands, respectively [33].In addition, the observed bands at 597, 533, and 433 cm −1 are attributed to the monoclinic CuO phase which confirms the monoclinic phase of the prepared PEG-CuO [34].The obtained bands between 800-3500 cm −1 are attributed to PEG on the CuO particles.For example, the bands in the region from 1000 to 1450 cm −1 are ascribed to C-O stretching and C-H bending vibrations modes [35].These bonds indicate that the PEG was attached to the copper oxide.The band at 2850-2960 cm −1 is due to alkane C-H stretch vibration mode and the band at 3200-3600 cm −1 is related to O-H stretching [36].These functional groups play the role of anchor to adsorb pollutions on the surface of PEG-Cu adsorbent.
On the other hand, as can be seen in Figure S2 that for the case of biosynthesised Ag, the bands are observed at 1147-1154, 1401-1415, 1632-1638, 2922-2924, 3359-3398 which are attributed to dimethyl vibration, C-H bonds in ketones and esters, aminoamides containing NH 2 groups, C-H bonds in alkanes, and N-H bonds in amides, respectively [32].These bonds show that the present amide, carboxylic, amine, and remained amino acid groups in the Amaranthus Retroflexus leaf extract play a role in the biosynthesis of Ag.In addition, these groups assist in the adsorption of pollutions on the surface of biosynthesis Ag particles to be degraded.
The crystalline nature of the synthesised Ag-NPs was confirmed from XRD analysis (Figure S3).This figure shows four distinct diffraction peaks at 38.2°, 44.1°, 64.1°and 77.2° which index the 111, 200, 220 and 311 planes of the cubic face-centred silver [32].The XRD pattern of PEG-CuO (Figure S4) illustrates the presence of crystalline monoclinic cubic cupric oxides.On the other hand, Figure S5 shows the XRD of Fe 3 O 4 are in good agreement with PCPDFWIN v.2.02, PDF No. 89-0691 [37].

Effects of operating parameters
The main operating parameters of ACC process are the amount adsorbent (PEG-CuO), and catalyst (Fe 3 O 4 , or Ag), ratio of the adsorbent to catalyst, salt concentration, pH, and operation time.Effect of these parameters was analysed and discussed in this section.In the present study, the removal efficiency was defined as the percentage of initial fungicides removed from the wastewater by the adsorbent and catalyst, and the degradation efficiency was considered the percentage of the removed fungicides which was degraded by the catalyst.

Amount of added materials 3.2.1.1. Adsorbent load.
Finding an optimum concentration of adsorbent to gain the maximum removal rate can significantly affect the operating cost.The removal efficiency of the three fungicides was evaluated when PEG-CuO used alone in different amounts, as presented in Figure 2a.This figure reveals that the adsorption efficiency is enhanced by increasing the amount of PEG-CuO due to the better adsorption capacity for penconazole and hexaconazole.It can be seen that even at a low amount of 5 mg, around 80% adsorption efficiency was obtained that demonstrates the high adsorption capacity of the prepared PEG-CuO.In addition, at 30 mg load, almost complete removal was obtained for all the three pesticides.This observation can be considered in agreement with optimum load reported for the removal of 2-chloroethyl phenyl sulphide by CuO/AgZSM zeolite composite [38].Accordingly, 30 mg of adsorbent can be considered as the optimum value for further analysis.

Catalyst load.
In order to study the effect of catalyst amount on the removal and degradation of fungicides, different loads of Fe 3 O 4 were tested across the range of 5-40 mg. Figure 2b and c present the removal and degradation efficiency of the three fungicides by Fe 3 O 4 , respectively.The removal results indicate that around 90% removal efficiency was obtained by the addition of 40 mg of Fe 3 O 4 , therefore, this amount can be selected as the optimum value for further analysis.As can be seen in Figure 2c, complete degradation of the fungicides could not be achieved even at 40 mg of Fe 3 O 4 .The observation of increasing removal and degradation efficiency with using more Fe 3 O 4 was found to be in a good agreement with previous research [39][40][41].
Moreover, the effect of Ag loading on the removal and degradation efficiency of fungicides was evaluated and illustrated in Figure 2d and e.It can be observed that the removal of three triazole compounds enhanced with increasing the amount of Ag up to 30 mg and reached 99%, however, further increase had almost no effect on the removal efficiency.Also Figure 2e shows that the degradation efficiency increased to around 67% using 30 mg of Ag, however, further increase to 35 mg had an inconsiderable effect.Accordingly, 30 mg can be selected as the optimum amount of Ag for the removal and degradation of fungicides.In addition, comparison of Figure 2c with Figure 2e shows that Ag has higher activity (in the degradation of the fungicides) than Fe 3 O 4 .
Figure 2 illustrates that the removal efficiency is limited by the catalysts, though a complete degradation of fungicides is possible using them.On the other hand, complete removal can be obtained.These results clearly show the necessity of using both the adsorbent and catalyst (i.e.ACC approach) to simultaneously take advantage of a complete removal by the adsorbent and high degradation efficiency using the catalyst.Therefore, the ACC process was followed in subsequent experiments.

Ratio of catalyst to adsorbent
The effect of catalyst to adsorbent ratio on the removal and degradation efficiencies of the fungicides was investigated.In this regard, the experiments were conducted with different percentages of Fe 3 O 4 /PEG-CuO and Ag/PEG-CuO.The removal and degradation efficiencies of Fe 3 O 4 /PEG-CuO are depicted in Figure 3a and b, respectively.As can be seen in Figure 3a, the complete removal of the fungicides was obtained after the addition of PEG-CuO.Analysis of the degradation efficiency (Figure 3b) revealed that the complete hexaconazole degradation was obtained by both Fe 3 O 4 and PEG-CuO.However, at least 70% adsorbent was required to achieve complete degradation of all the fungicides.Similarly, Munasir et al. [42] reported an optimum of 50% Fe 3 O 4 for complete removal and degradation of methylene blue by Fe 3 O 4 /rGO.Therefore, 30/70 ratio was selected as the optimal for Fe 3 O 4 /PEG-CuO (i.e.18 mg of Fe 3 O 4 , and 42 mg PEG-CuO) and used for the further experiments.
The removal and degradation efficiencies of Ag/PEG-CuO are depicted in Figure 3c and d, respectively.According to Figure 3c, at catalyst percentages lower than 50%, the removal is not complete because of an insufficient amount of catalyst.On the other hand, Figure 3d shows that at least 50% adsorbent is required to obtain a total degradation efficiency.Therefore, 50/50 ratio of Ag/PEG-CuO (i.e. 30 mg of each) was selected as the optimal for the subsequent parameter study.On the other hand, subtracting the degradation efficiencies from their removal ones illustrates the adsorbed fungicides which were not degraded.For instance, according to Figure 3c and d, 27%, 22% and 32% of penconazole, hexaconazole, and diniconazole were respectively just adsorbed (not degraded) by Ag/PEG-CuO particles at 70/30 ratio.
The mechanism of fungicides treatment by the ACC process involves three main steps.First, the triazole fungicides mostly adsorb on the surface of PEG-CuO [38].Afterwards, the PEG-CuO and catalyst (Ag or Fe 3 O 4 ) can be collided leading to moving the adsorbed fungicides from PEG-CuO to the catalyst surface [43].Finally, the fungicides on the surface of catalysts can be degraded [44,45].

Salt concentration
Analysis of the salting-out effect is useful to study the performance of ACC process for salty wastewater.The addition of NaCl can enhance the ionic strength of water and reduce the solubility of analytes [46][47][48].In fact, the salting-out procedure may contribute in the change of adsorption by decreasing the number of water molecules that interact with analytes [49].On the other hand, adding NaCl can lead to increasing the viscosity of solution, which is unfavourable for the extraction process.Moreover, the presence of Na + on the surface of catalyst can reduce its efficiency because of occupying active site [46].Considering the various effects of salt, different solutions containing 0, 5, 10, 15, 20 and 25 wt.%NaCl were used to investigate the salting-out effect in the ACC process (including Ag/PEG-CuO or Fe 3 O 4 /PEG-CuO).The obtained removal and degradation efficiencies are presented in Figure 4.As can be seen, both the removal and degradation efficiencies decreased as the NaCl content increased, and just at the absence of the salt, complete removal and degradation were achieved.Therefore, the presence of the salt has no positive influence on the ACC process.This result indicates that the impact of viscosity increase as well as surface blockage by Na + were dominant on both degradation and removal efficiency which is in a good agreement with previous works which used only adsorbents [49][50][51].

pH
The pH of wastewater has an important role on the degradation processes, as it affects the strength and stability of active sites of adsorbent and catalyst [52,53].The difference in the acidity of wastewater and the adsorbent can affect the removal of contaminates [54,55].The influence of pH on the removal and degradation efficiency of fungicides was studied in the range of 1-13 for Fe 3 O 4 /PEG-CuO (Figure 5a and c).It was observed that the highest removal and degradation were obtained at pH 7 and the efficiencies were reduced at acidic or basic pH.According to these figures, the negative effect of pH was higher at basic condition, compared to the acidic environment, for both the removal and degradation.For example, the degradation efficiency of diniconazole dropped from about 100% to around 20% by increasing pH from 7 to 13, that indicates pH can have a significant influence on the process performance.
The effect of pH on the removal and degradation efficiencies of Ag/PEG-CuO is, respectively, presented in Figure 5b and d.As can be seen, only at pH 7 complete removal and degradation performance was obtained.Similar to Fe 3 O 4 /PEG-CuO, the efficiency reduced more at basic condition in comparison to highly acidic environment for the case of Ag/PEG-CuO.For example, the degradation efficiency of penconazole decreased to around 26% at pH 13 (Figure 5d).Thus, for Fe 3 O 4 /PEG-CuO and Ag/PEG-CuO pH of 7 and 5 were selected to study other parameters in this research, respectively.These values can be considered in agreement with pH of 5.5 [51], 6 [46], 6.5 [54,55], and 7 [56,57] reported for removal of organophosphorous, carbamate, and aryloxy pesticides.

Operation time
Mass transfer and degradation are time-dependent processes and equilibrium is obtained only after a certain period of time.For process optimisation, it is therefore important to find the appropriate operation time [47,48,58].In this regard, the influence of the operation time on the removal and degradation efficiencies was investigated for Fe 3 O 4 /PEG-CuO and Ag/PEG-CuO, as depicted in Figure 6a-d.According to these figures, when the processing time went up to 85 min, the removal and degradation of fungicides were complete for both Fe 3 O 4 /PEG-CuO and Ag/PEG-CuO.Hence, 85 min was chosen as the optimum operation time and used for other experiments, including the study of the real fungicide polluted wastewater treatment using the ACC process.
The kinetic model of the fungicide degradation may be determined based on the first order reaction (Eq. 1) [59,60]: where K app , C, and C 0 are the first-order rate constant, the concentration of fungicides at time t, and the initial concentration of fungicides.The rate constant as well as R 2 of the first-order reactions by Ag/PEG-CuO and Fe 3 O 4 /PEG-CuO are presented in Table S1.As seen, the R 2 values of all fungicides are close to 1 that confirms the appropriateness of first-order reaction for the fungicide degradation.Furthermore, comparing the K app of Ag/ PEG-CuO and Fe 3 O 4 /PEG-CuO shows that the degradation rate of the synthesised Ag is higher than that of the commercial Fe 3 O 4 for all studied fungicides.The degradation rate of Hexaconazole is higher than two other fungicides by both Ag/PEG-CuO and Fe 3 O 4 /PEG-CuO.
Finally, the recyclability of Ag/PEG-CuO was studied through the removal of diniconazole under optimum process conditions (Figure S6).As seen, Ag/PEG-CuO maintained its removal capability after four recycle.The observed minor reduction of removal can result from adsorbing the persistent intermediates as well as the reduction of Ag + ions [61].On the other hand, after several uses, their valuable metals can be extracted (from the used materials) and reused for the construction of different materials such as catalysts and adsorbents.

Treatment of real wastewater
The optimised conditions of the ACC process were applied to treat real fungicide polluted wastewaters obtained by washing some vegetables such as cucumber, lettuce, bell pepper, cabbage, and tomato.The amounts of fungicides before and after the treatment was analysed by the HPLC-UV and the obtained data is shown in Table 1.As can be seen, the concentration of triazole fungicides in all the wastewaters were less than 5 ppm.All the investigated fungicides were found in the wastewater of cucumber and bell pepper.Only penconazole was detected in the cabbage and lettuce wastewaters, and no fungicide was found in the tomato wastewater.
Ag/PEG-CuO and Fe 3 O 4 /PEG-CuO samples were used at the obtained optimum operating conditions, and results showed complete removal and degradation for all fungicides in the obtained vegetable wash wastewaters (i.e.no fungicides were detected in the treated wastewaters).The obtained HPLC chromatogram of washing cucumber wastewater is presented in Figures S7 and S8 as two samples.There is no peak in these figures which illustrates the presence of penconazole, hexaconazole, and diniconazole in the treated wastewater, and accordingly, the fungicides were completely degraded after the treatment and can be transformed into CO 2 and H 2 O. Thus, it can be concluded that the ACC process has a great capability in the treatment of real fungicide polluted wastewater.

Conclusion
In this research, the ACC approach was proposed and evaluated for the complete removal and degradation of three fungicides in the wastewater.For this purpose, PEG-CuO and Ag particles were first prepared and used as the adsorbent and catalyst, respectively.For comparison purposes, Fe 3 O 4 was also used as a catalyst.The results showed that complete removal of all the fungicides cannot be obtained using the catalysts alone (either Ag or Fe 3 O 4 ), even at their high concentrations.Nevertheless, complete removal and degradation were obtained using the ACC process, i.e. simultaneous use of PEG-CuO (as the adsorbent) and one of the catalysts (Ag or Fe 3 O 4 ).Moreover, effects of different parameters (including the adsorbent load, catalyst load, ratio of catalyst to adsorbent, salt concentration, pH, and operating time) on the performance of ACC process were studied, and the following conclusions were obtained: • All the fungicides can be completely removed and degraded by 50/50 ratio of Ag/ PEG-CuO as well as 30/70 ratio of Fe 3 O 4 /PEG-CuO; • The presence of NaCl in the wastewater has no positive influence on the ACC process, and just at the absence of the salt, complete removal and degradation were achieved; • The optimum pH of the ACC process was 7; • The operation time of 85 min was enough and optimum for the complete treatment of all the fungicides by Fe 3 O 4 /PEG-CuO and Ag/PEG-CuO.
Finally, the ACC process capability was assessed for the treatment of five real fungicide polluted wastewaters, and it was confirmed that the optimised ACC process can successfully treat the wastewaters.Thus, this study suggests the ACC process as a promising n.q a Tomato n.q a n.q a n.q a n.q a Bell pepper 1.77 0.60 0.85 n.q a Cabbage 3.50 n.q a n.q a n.q a Lettuce 3.80 n.q a n.q a n.q a a Not quantified: HPLC-UV did not detect fungicides.
alternative for the complete removal and degradation of chemical contaminants in wastewater.

Figure 1 .
Figure 1.Explanation of removed and degraded of triazole fungicides (a), Definition of removal and degradation efficiency of triazole fungicides (b).

Figure 2 .
Figure 2. Removal efficiency of PEG-CuO (a), removal efficiency of Fe 3 O 4 (b), degradation efficiency of Fe 3 O 4 (c), removal efficiency of Ag (d), and degradation efficiency of Ag (e).

Figure 3 .
Figure 3.Effect of the ratio of Fe 3 O 4 to PEG-CuO on the removal efficiency (a), and degradation efficiency (b); as well as effect of the ratio of Ag to PEG-CuO on the removal efficiency (c), and degradation efficiency (d).

Figure 6 .
Figure 6.Effect of operation time on the removal efficiency of Fe 3 O 4 /PEG-CuO (a), removal efficiency of Ag/PEG-CuO (b), degradation efficiency of Fe 3 O 4 /PEG-CuO (c) and degradation efficiency of Ag/PEG-CuO (d).

Table 1 .
The amounts of fungicide residues in vegetable wash wastewater before and after the treatment.