In this study, H2(g) production from real wastes of polyethylene terephthalate and polylactic acid using CNx/Ni2P nanocatalyst was investigated with photoreforming process. Optimum experimental conditions were found at ultrasonicated 4.8 mg/ml CNx/Ni2P nanocatalyst, at pre-treated 20 mg/ml polyethylene terephthalate, at pre-treated 20 mg/ml polylactic acid, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at 60 h photoreforming solar irradiation time, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively. XRD, FESEM, EDX, FTIR, TEM, DRS and XPS analyzes were performed for characterization studies of microplastics. Polyethylene terephthalate and polylactic acid measurements were measured in inductively coupled plasma mass spectrometry (ICP-MS). H2(g) measurements were made in gas chromatography–mass spectrometry (GC-MS). The maximum 41.40 ± 5.10 and 48.60 ± 3.12 µmol H2 / gsub yields were measured for CNx=20 mg/ml and for Ni2P=20 mg/ml, respectively. The maximum 18.26 ± 1.18 and 52.41 ± 7.29 µmol H2 / gsub H2(g) production yields were found for non-sonicated CNx/Ni2P and ultra-sonicated CNx/Ni2P nanocatalyst, respectively, after 24 h photoreforming solar irradition time. The maximum 123.75 ± 11.92 and 267.41 ± 24.65 µmol H2 / gsub H2(g) production yield was measured for polyethylene terephthalate and polylactic acid, respectively, after 60 h photoreforming solar irradiation time. The maximum 6.57 ± 0.87Percentage and 2.43 ± 0.38Percentage stoichiometric H2 conversion yields were observed for polyethylene terephthalate and polylactic acid, respectively, after 60 h photoreforming solar irradition time. The maximum 96 and 57 μmol H2 / gsub H2(g) yields for polyethylene terephthalate were obtained over CNx/Ni2P and H2NCNx/Ni2P, respectively, after 60 h photoreforming solar irradiation time. The maximum 182 and 173 μmol H2 / gsub H2(g) yields for polylactic acid were observed over CNx/Ni2P and H2NCNx/Ni2P, respectively, after 60 h photoreforming solar irradiation time. The maximum 4.85 ± 0.62, 88.37 ± 10.74, 26.55 ± 1.95, 21.94 ± 1.86, 75.30 ± 9.34, 60.07 ± 5.11 and 14.61 ± 2.14 μmol H2 / gsub H2(g) production yields were obtained for Acetate, Ethylene glycol, Formate, Glycolate, Glyoxal, Lactate and Terephthalate oxidation intermediates, respectively, after 24 h photoreforming solar irradiation times. 126 nmol Acetate, 131 nmol Formate, 5 nmol Glycolate and 6200 nmol Glyoxal organic oxidation intermediates for polyethylene terephthalate with CNx/Ni2P nanocatalyst were found after 7 days photoreforming solar irradiation time. 67 nmol Acetate and 63 nmol Formate organic oxidation intermediates for polylactic acid with CNx/Ni2P nanocatalyst were obtained after 7 days photoreforming solar irradiation time. Photoreforming process is a very effective, easy to apply, economical and environmentally friendly method for the removal of plastic and microplastic wastes.

86Percentage of plastic packages are collected in landfills, or they are randomly mixed into the environment (Garcia et al., 2017; Geyer et al., 2017; MacArthur, 2017a; MacArthur, 2017b). Plastic pollution is not only a global environmental pollution problem; it also shows the unconscious waste of a very valuable resource that can be recycled and reused. The majority of polymers are synthesized from fossil fuels, especially petroleum derivatives (Garcia et al., 2017). It is estimated that approximately 3.5 billion barrels of oil can be saved each year if all global plastic waste is recycled (Garcia et al., 2017). The most important problems in the widespread application of plastic recycling are; suboptimal waste management, lack of awareness and limited size of various chemicals, complexes and polymer products (MacArthur, 2017a; MacArthur, 2017b).

Pieces of polymer smaller than ≤ 5 mm are defined as microplastics; and for recycling, microplastics represent a particularly problematic group of plastics (Cozar et al., 2014; Law and Thompson, 2014; Andrady, 2015). Microplastics formed when plastic degrades over time; They are available in a wide variety of products (Law and Thompson, 2014). Very small sizes and very dilution of microplastics; making it very difficult to collect and reuse salts from the oceans (Cozar et al., 2014; Law and Thompson, 2014; Andrady, 2015), drinking water and salts (Kosuth et al., 2018; Mason et al., 2018; Pivokonsky et al., 2018) from almost all parts of the world. A disadvantage is that even the recycling of reusable plastics has some limitations. For this reason, many polymers can only be converted into lower quality products. To give an example, only 7Percentage of recycled poly (ethylene terephthalate) (PET) bottles can be produced as re-bottles (MacArthur, 2017a). Management structures used in plastic recycling; currently far from being able to sustainably and economically treat a wide variety of plastic waste. In order to overcome these problems: in order to be able to convert the polymers at the end of use into valuable products; more functional and usable new technologies are urgently needed.

A new technology that has recently started to be used in the recovery of plastics and especially microplastics; It is a photoreformation method in which sunlight and a photocatalyst produce H2(g) from an organic substrate and water. The basic principle in the photoreformation method is that the substrate is oxidized to other organic molecules by the excited photocatalyst, acting as an electron donor. Photogenerated electrons are transferred from the photocatalyst to a co-catalyst in the next step; they reduce water to H2(g). H2(g) is in very high demand in the agricultural, pharmaceutical and chemical industries, as well as in renewable energy applications; It is a very valuable raw material (DOE, 2013; IEA, 2015). One of the existing H2(g) production technologies; In contrast to fossil fuels' steam reforming (Spath and Mann, 2001) or thermal-based approaches to converting plastic to oil (Chen et al., 2019), the key advantages of PR are; They can be run at ambient temperature and pressure, use sunlight as their sole energy input, and produce fuel cell grade H2(g). (Wakerley et al., 2017). While the photocatalytic degradation of plastics, typically to microplastics and CO2(g), has been investigated for years (Ohtani et al., 1992; Horikoshi et al., 1998; Tofa et al., 2019), not only plastic waste is reduced by the phtoreformation method; At the same time, a very important advantage is provided by producing valuable chemical products. The thermodynamics of the photoreformation process is also almost energy neutral (Kuehnel and Reisner, 2018): Photoreformation of ethylene glycol at 25oC requires ΔG° = 9.2 kJ mol-1 and E°cell = -0.01 V.

Although the photoreformation of simple molecules and biomass has been investigated in detail (Puga, 2016; Pellegrin and Odobel, 2017; Kuehnel and Reisner, 2018), plastic substrates have been largely ignored. Making polymer recycling difficult; Complex structures, low water solubility and poor biodegradation also make the photoreformation method more difficult. There are only a few previous studies on the photoreformation of plastics: in one of them; While using expensive and ultraviolet (UV) absorbing TiO2/Pt photocatalyst (Kawai and Sakata, 1981), in another; toxic CdS/CdOx quantum dots are used (Uekert et al., 2018).

Since the polymeric carbon nitride has a composition based on CNx, high stability, well-positioned conductivity (CB) and valence bands (VB) and the elements Carbon (C) and Nitrogen (N), which are abundant in the soil; It is of great interest as a new generation photocatalyst (Wang et al., 2009; Vilela et al., 2012; Cao et al., 2015; Gong et al., 2015). In recent years, CNx has been proven to support solar-powered organic substrate oxidation (Su et al., 2010), pollutant degradation (Cui et al., 2012; Qiu et al., 2015), H2(g) production (Maeda et al., 2009; Caputo et al., 2015; Lau et al., 2016), and water decomposition (Wang et al., 2009; Liu et al., 2015; Zhu et al., 2017). Photocatalytic performances; is limited to the rapid recombination of photogenerated hole-electron pairs. To overcome this limitation; Various strategies such as nonmetal doping (Zhang et al., 2010; Wang et al., 2011; Li et al., 2012), noble metal doping (Ding et al., 2011; Gao et al., 2016; Li et al., 2016) and nanoengineering of CNx (Yang et al., 2013; Zhan et al., 2017) can be applied. As an alternative strategy, it may be aimed to design a system in which photogenerated holes or electrons are consumed faster than charge recombination reactions by accelerating charge transfer to the catalytic sites.

Carbon nitride is a non-toxic and very affordable polymeric photocatalyst (Thomas et al., 2008; Wang et al., 2009; Lin et al., 2019); With the addition of cyanamide defects, the photocatalytic efficiency can be increased (Lau et al., 2016). CNx has visible light absorption and band edges suitable for photoreformation reactions; CB= - 0.5 V-NHE (normal ized hydrogen electrode), VB=2.2 V-NHE has a permissive band gap of 2.7 eV (Meyer et al., 2017). It is stated in the literature that CNx is also used for photoreformation of biomass with various cocatalysts over a wide pH range (Kasap et al., 2018). With its key advantages of visible light absorption, alkalinity stability, low cost and non-toxicity, CNx is at a level that can compete with both CdS/CdOx and TiO2/Pt for polymer photoreformation. Ni2P has previously been used for H2(g) formation with nonfunctional carbon nitride (H2NCNx) and a soluble sacrificial electron donor (triethanolamine) evolution (Indra et al., 2017; Ye et al., 2017; Wen et al., 2017), and has high potential for plastic PR given its alkaline compatibility and relatively high H2(g) forming activity (Cao et al., 2017).

Kasap et al. (2016), in order to simultaneously produce aldehyde and H2(g) from alcohol in 1/1 stoichiometry; investigated a melon type carbon nitride (NCNCNx) with cyanamide surface function in combination with a molecular nickel (II) bis(diphosphine) H2(g) evolution catalyst NiP, oxidation and proton reduction, respectively. This closed photocatalytic redox system exhibited enhanced photoactivity with NCNCNx compared to the unfunctionalized (amino-terminated) carbon nitride H2NCNx with superior hole quenching ability of 4-methyl benzyl alcohol (4-MBA). The slow transfer of photogenerated electrons to diffusional NiP has been observed as the overall rate-limiting step for this photocatalyst system (Kasap et al., 2016). 

A noble metal-free sacrificial photocatalytic system using dysfunctional H2NCNx and molecular catalyst NiP was investigated (Caputo et al., 2014). When NiP is fixed in a homogeneous solution and on semiconductor surfaces (Gross et al., 2014; Leung et al., 2017; Creissen et al., 2018); It is a hydrogenase-inspired molecular H2(g)-evolution catalyst (Helm et al., 2011; Kilgore et al., 2011) with good activity. Catalyzed by a more active and surface functionalized NCNCNx and sacrificial electron donor NiP; It is modified by a selective and almost quantitative alcohol oxidation reaction due to proton reduction (Kasap et al., 2016). 

In this study, production of H2(g) from polyethylene terephthalate and polylactic acid wastes using CNx/Ni2P nanocatalyst was investigated. In our experimental study, polyester microfibers and real non-recyclable plastic waste, including those contaminated with oil, were used. XRD, FESEM, EDX, FTIR, TEM, DRS and XPS analyzes were performed for characterization studies of microplastics. Polyethylene terephthalate and polylactic acid measurements were measured in inductively coupled plasma mass spectrometry (ICP-MS). H2(g) measurements were made in gas chromatography–mass spectrometry (GC-MS).

1. Preparation of Carbon Nitride 

Nonfunctionalized carbon nitride (H2NCNx) was prepared by slow heating of melamine to 550°C for 3 h in a ventilated environment according to the literature procedure (Liu et al., 2015). The resulting compound was ground and powdered in a mortar. Combining cyanamide-functional CNx, H2NCNx and KSCN (weight ratio=1/2); It was prepared by heating under Ar gas for 1 h at 400°C and then at 500°C for 30 min (Lau et al., 2016). After cooling the powder was washed with deionized H2O and dried under vacuum at 60°C.

1. Preparation of Ni2P

NiCl2.6H2O and NaH2PO2.H2O (weight ratio=1/5) were mixed in water for 1 h and then subjected to an ultrasonic bath for 1 h; finally dried under vacuum at 60°C. The dry compound was heated at 200°C for 1 h under Ar gas with a ramp rate of 5°C/min. After cooling to 25oC, it was washed with 2 units of black powder, 2 units of deionized H2O and 1 unit of ethanol; It was dried under vacuum at 60°C.

1. Preparation of Ni2P with Light Absorber

According to the procedure described in the literature (Indra et al., 2017), CNx, H2NCNx or TiO2 nanoparticles (NPs) (300 mg) and 20 mg NiCl2.6H2O were taken and combined in 1 ml of deionized H2O; It was stirred for 1 h and then sonicated for 1 h. Then, 100 mg of NaH2PO2.H2O was added to the mixture, mixed again and sonicated for 1 h. This mixture was dried under vacuum at 60°C and heated under Ar(g) with a rise rate of 5°C/min at 200°C for 1 h. After cooling to 25oC, the powder mixture; washed with 3 parts of deionized H2O and 3 parts of ethanol, respectively, and dried under vacuum at 60°C.

1. Pretreatment of Substrate 

50 mg/l polymer was mixed at 300 rpm with our adaptation from the procedure described in the literature (Uekert et al., 2018). Then put in a closed bottle; It was immersed in 2 M aqueous semiconductor grade KOH at 40oC for 24 h.

1. Generation of Photocatalytic H2(g)

A dispersion of CNx/Ni2P nanocatalyst in 5 mg/ml deionized H2O; 10 minutes were ultrasonicized with 30 second pulses at 100Percentage amplitude followed by 5 second pauses (Kasap et al., 2018). For 0.65 ml mixture in 2 M aqueous semiconductor grade KOH; 1 ml of pretreated polymer and 0.35 ml of deionized H2O per sample were used. Optimal experimental conditions were determined for 4 ml of 1 M KOH, 4.8 mg/ml CNx/Ni2P nanocatalyst, 50 mg/ml polymer, 20 mg/ml polyethylene terephthalate bottle or 15 mg/ml polyester microfibers, respectively. CNx/Pt nanocomposites (NCs); It was made by ultrasonicating CNx and then adding H2PtCl6 as a precursor, while Pt was synthesized via in situ photodeposition. Prepared samples were added to Pyrex glass photoreactor bottles with an internal volume of 10 ml and the bottles were tightly closed with rubber septa caps. After a short vortexing the samples; For 10 min GC grade analysis, it was cleaned by sparging with N2(g) containing 2Percentage CH4(g) and no CH4(g) was found in the samples after illumination without adding this internal standard. The samples were equipped with an AM 1.0 global (G) air mass filter and to remove infrared radiation; irradiated with a sunlight simulator (Newport/Oriel Sol3A Class AAA Solar Simulator, Model 94043A, 150 mW/cm2) equipped with a water filter. Visible light experiments were performed by adding a cut-off filter for λ Greater-than 400 nm. All samples were mixed at 600 rpm and held constant at 25°C during irradiation. Considering 40 µl of reactor headspace gas for each sample; H2(g) production in the samples was analyzed periodically by GC-MS. Excessive pressure inside the bottle; minimally observed, with an increase of 0.02 atm per 10 μmol H2(g) produced.

1. Stoichiometric H2(g) Conversion Mechanism

4 ml of 1 M KOH is taken; Samples containing 10 mg of substrate were prepared and irradiated for photocatalysis. H2(g) conversion (Percentage) were calculated as in Equation 1 (Emel’yanenko et al., 2010; NIST Chemistry WebBook, 2023):

                          (1)

where; nH2, exp: is the H2(g) measured in experiment (mol), n substrate, exp: is the substrate used in experiment (mol), and nH2, idealn substrate, ideal −1: is the ideal ratio of moles H2(g) to substrate, respectively.

1. Calculation of Power 

Power output from generated H2(g); It was calculated according to Equation 2:

                        (2)

where; VH2: is the molar volume of H2(g) (24.47 l/mol at 25oC), nH2: is the moles of H2(g) produced, ρH2: is the density of H2(g) (8.235×10−5 kg/l at 25oC), uH2: is the lower heating value of H2(g) (120×106 J/kg), and tirr: is the irradiation time (s), respectively.

2.8. Characterization 

2.8.1. X-Ray Diffraction (XRD) Analysis

Powder XRD patterns were recorded on a Shimadzu XRD-7000, Japan diffractometer using Cu Kα radiation (λ = 1.5418 Å, 40 kV, 40 mA) at a scanning speed of 1o /min in the 10-80o 2θ range. Raman spectrum was collected with a Horiba Jobin Yvon-Labram HR UV-Visible NIR (200-1600 nm) Raman microscope spectrometer, using a laser with the wavelength of 512 nm. The spectrum was collected from 10 scans at a resolution of 2 /cm. The zeta potential was measured with a SurPASS Electrokinetic Analyzer (Austria) with a clamping cell at 300 mbar.

2.8.2. Field Emission Scanning Electron Microscopy (FESEM) 

The morphological features and structure of the experimental samples were determined by Field Emission Scanning Electron Microscopy (FESEM) (FESEM, Hitachi S-4700). 

2.8.3. Energy Dispersive X-Ray (EDX) Spectroscopy Analysis

The elements on the surface of the experimental samples were analyzed using energy dispersive X-ray analysis (EDX) with EDX spectrometry device (TESCAN Co., Model III MIRA). 

2.8.4. Fourier Transform Infrared Spectroscopy (FTIR) Analysis 

The FTIR spectra of experimental samples were recorded using the FT-NIR spectroscope (RAYLEIGH, WQF-510).

2.8.5. Transmission Electron Microscopy (TEM) Analysis

The obtained experimental samples were collected and harvested by centrifugation (8000 rpm, 5 min), washed twice with deionized H2O, and resuspended in ethanol (C2H6O) and dripped onto a carbon-coated copper (Cu) Transmission Electron Microscopy (TEM) grid. Vacuum drying then occurred to the experimental samples for 24 h at 25oC room temperature. The dry samples on the Cu grid were viewed and examined by TEM Analysis recorded in a JEOL JEM 2100F, Japan under 200 kV accelerating voltage. The size and structure of the experimental samples were identified with TEM analysis.

2.8.6. Diffuse Reflectance UV-Vis Spectra (DRS) Analysis

DRS Analysis in the range of 200–800 nm was recorded on a Cary 5000 UV-Vis Spectrophotometer from Varian. DRS was used to monitor the experimental samples.

2.8.7. X-Ray Photoelectron Spectroscopy (XPS) Analysis

The valence state of the experimental samples were investigated and was analyzed using XPS (ESCALAB 250Xi, England). XPS used an Al Ka source and surface chemical composition and reduction state analyses was done, with the core levels recorded using a pass energy of 30 eV (resolution approximately 0.10 eV). The peak fitting of the individual core-levels was done using XPS-peak 41 software, achieving better fitting and component identification. All binding energies were calibrated to the C 1s peak originating from C–H or C–C groups at 284.6 eV

2.8.8. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) Analysis

The Agilent 8800 ICP-MS instrument (Agilent Technologies, Japan) was used to determine different concentrations of polyethylene terephthalate and polylactic acid. For analysis, the samples were acid digested in closed Savillex® PFA beakers prior to ICP-MS. 5 ml of suspended sample in PBS was centrifuged at 10000 ×g for 30 min, after which the supernatant was removed. The resulting pellet was acid digested with 1.5 ml of 14 mol/l HNO3 and 0.5 ml of 9.8 mol/l H2O2. The closed beakers were heated to 115°C overnight on a hot plate. After complete mineralization, the digestates were evaporated at 90°C until dryness, then redissolved in 2.0 ml of 0.35 mol/l HNO3. This solution was further diluted with 0.35 mol/l HNO3 and rhodium (Rh) was added as the internal standard (final concentration = 2 μg/l) to compensate for potential matrix effects and/or signal instability.

2.8.9. Gas Chromatography–Mass Spectrometry (GC-MS)

Gas chromatography–mass spectrometry (GC-MS) and gas chromatograph (GC) (Agilent Technology model 6890N) equipped with a mass selective detector (Agilent 5973 inert MSD). Mass spectra were recorded using a VGTS 250 spectrometer equipped with a capillary SE 52 column (HP5-MS 30 m, 0.25 mm ID, 0.25 μm) at 220°C with an isothermal program for 10 min. The initial oven temperature was kept at 50oC for 1 min, then raised to 220oC at 25oC/min and from 200 to 300oC at 8oC/min, and was then maintained for 5.5 min. High purity He (g) was used as the carrier gas at constant flow mode (1.5 ml/min, 45 cm/s linear velocity). All H2(g) measurements of the experimental samples were made in the GC-MS device.

1. Characterizations
   1. XRD Analysis

The results of XRD analysis were observed after H2(g) production from real wastes of polyethylene terephthalate and polylactic acid using CNx/Ni2P nanocatalyst with photoreforming process (Figure 1). The characterization peaks were found at 2θ values of 7.74o, 46.10o, 28.16o, 36.11o and 43.87o, respectively, and which can also be indexed as (101), (210), (204), (312) and (222), respectively (Figure 1).

Figure 1: XRD spectra of CNx/Ni2P nanocatalyst after photoreforming process for H2(g) production from real wastes of polyethylene terephthalate and polylactic acid.

1. FESEM Analysis

The morphological features of CNx/Ni2P nanocatalyst was characterized through FESEM images before photoreforming process (Figure 2a) and after photoreforming process (Figure 2b), respectively.

Figure 2: FESEM images of CNx/Ni2P nanocatalyst (a) before photoreforming process (b) after photoreforming process for H2(g) production from real wastes of polyethylene terephthalate and polylactic acid (FESEM size: 4 μm).

1. EDX Analysis

The results of EDX analysis were found after H2(g) production from real wastes of polyethylene terephthalate and polylactic acid using CNx/Ni2P nanocatalyst with photoreforming process (Figure 3).

Figure 3: EDX spectrum of CNx/Ni2P nanocatalyst after photoreforming process for H2(g) production from real wastes of polyethylene terephthalate and polylactic acid.

1. FTIR Analysis

The FTIR spectrum of CNx/Ni2P nanocatalyst was measured to H2(g) production from real wastes of polyethylene terephthalate and polylactic acid after photoreforming process (Figure 4). The main peaks of FTIR spectrum for CNx/Ni2P nanocatalyst was observed at 3700 1/cm, 2250 1/cm, 2010 1/cm, 1870 1/cm, 1600 1/cm, 1150 1/cm, 960 1/cm and 830 1/cm wavenumber, respectively (Figure 4).

Figure 4: FTIR spectrum of CNx/Ni2P nanocatalyst after photoreforming process for H2(g) production from real wastes of polyethylene terephthalate and polylactic acid.

1. TEM Analysis

The TEM images of CNx/Ni2P nanocatalyst was obtained to H2(g) production from real wastes of polyethylene terephthalate and polylactic acid after photoreforming process (Figure 5).

Figure 5: TEM images of CNx/Ni2P nanocatalyst after photoreforming process for H2(g) production from real wastes of polyethylene terephthalate and polylactic acid.

1. DRS Analysis

The DRS spectrum of CNx/Ni2P nanocatalyst was observed to H2(g) production from real wastes of polyethylene terephthalate and polylactic acid after photoreforming process (Figure 6). The DRS spectra of CNx/Ni2P nanocatalyst was recorded in the wavelength range from 300 nm to 600 nm using diffuse reflectance UV-V is spectra (Figure 6). The DRS spectrum absorption peaks of CNx/Ni2P nanocatalyst were found at wavelengths of 310 nm, 320 nm, 335 nm, 348 nm and 425 nm, respectively, for CNx/Ni2P nanocatalyst after photoreforming process (Figure 6).

Figure 6: The DRS spectrum of CNx/Ni2P nanocatalyst after photoreforming process for H2(g) production from real wastes of polyethylene terephthalate and polylactic acid.

1. XPS Analysis

The XPS analysis of CNx/Ni2P nanocatalyst was found to H2(g) production from real wastes of polyethylene terephthalate and polylactic acid after photoreforming process (Figure 7). The results of XPS analysis were measured for N1s edge of CNx/Ni2P nanocatalyst (Figure 7a) and P2p edge of CNx/Ni2P nanocatalyst (Figure 7b), respectively. The binding energy value for N1s edge of CNx/Ni2P nanocatalyst was measured to 398.76 eV for N=C bond and 400.95 eV for N-C bond, respectively (Figure 7a). The binding energy value for P2p edge of CNx/Ni2P nanocatalyst was observed to 133.11 eV for POx (Figure 7b).

(a)

(b)

Figure 7: XPS spectra of (a) N1s edge of CNx/Ni2P nanocatalyst and (b) P2p edge of CNx/Ni2P nanocatalyst after photoreforming process for H2(g) production from real wastes of polyethylene terephthalate and polylactic acid.

1. Photoreforming Experiments of Polyethylene Terephthalate and Polylactic Acid for H2(g) Production 

Photoreforming conditions for H2(g) production from real wastes of polyethylene terephthalate and polylactic acid with CNxNi2P nanocatalyst was summarized at Table 1. The maximum 41.40 ± 5.10 µmol H2 / gsub yield was measured for CNx=20 mg/ml, at ultrasonicated 4.8 mg/ml CNx/Ni2P nanocatalyst, at pre-treated 20 mg/ml polyethylene terephthalate, at pre-treated 20 mg/ml polylactic acid, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at 24 h, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively (Table 1).

Table 1: Photoreforming conditions for H2(g) production from real wastes of polyethylene terephthalate and polylactic acid with CNxNi2P nanocatalyst (Experimental conditions: at ultrasonicated 4.8 mg/ml CNx/Ni2P nanocatalyst, at pre-treated 20 mg/ml polyethylene terephthalate, at pre-treated 20 mg/ml polylactic acid, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at 24 h, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively).The maximum 48.60 ± 3.12 µmol H2 / gsub yield was measured for Ni2P=20 mg/ml, at ultrasonicated 4.8 mg/ml CNx/Ni2P nanocatalyst, at pre-treated 20 mg/ml polyethylene terephthalate, at pre-treated 20 mg/ml polylactic acid, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at 24 h, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively (Table 1).

Optimization was achieved for maximum total H2(g) production under all experimental conditions (CNx loading, Ni2P loading, CNx/Ni2P photocatalyst concentration, polyethylene terephthalate, polylactic acid, polymer concentration, photoreforming time, temperature, pH, and irradiation solar light conditions…etc.) (Table 1). Harsh conditions (e.g., high pH) are often required to solubilize plastic, and polymer photoreforming withCNx/Ni2P improves significantly with increasing pH values, from 41.40 μmol H2 / gsub, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at 24 h, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively (Table 1).

Comparison of photoreforming with non-sonicated versus ultra-sonicated CNx/Ni2P nanocatalyst was determined at Table 2. Experimental conditions were optimized at 4.8 mg/ml CNx/Ni2P, 20 mg/ml polyethylene terephthalate, pre-treated 20 mg/ml polylactic acid, 4 ml aqueous 1 M KOH, 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at 24 h, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively (Table 2).

The CNx/Ni2P nanocatalyst was ultrasonicated in H2O for 10 min according to a procedure reported in the literature (Kasap et al., 2018). This ultrasonication process is known to increase the surface area and activity of the CNx/Ni2P nanocatalyst (Kasap et al., 2018).

Table 2: Comparison of photoreforming with non-sonicated versus ultra-sonicated CNx/Ni2P nanocatalyst (Experimental conditions: at 4.8 mg/ml CNx/Ni2P, at pre-treated 20 mg/ml polyethylene terephthalate, at pre-treated 20 mg/ml polylactic acid, at 4 ml aqueous 1 M KOH, at 10 ml internal      volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at 24 h, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively).

The maximum 18.26 ± 1.18 µmol H2 / gsub H2(g) production yield of non-sonicated CNx/Ni2P nanocatalyst was observed during photoreforming process, after 24 h photoreforming solar irradition time, at 4.8 mg/ml CNx/Ni2P, at 20 mg/ml polyethylene terephthalate, at pre-treated 20 mg/ml polylactic acid, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively (Table 2)                                                                                                                                               The maximum 52.41 ± 7.29 µmol H2/gsub H2(g) production yield of ultra-sonicated CNx/Ni2P nanocatalyst was measured during photoreforming process, after 24 h photoreforming solar irradition time, at 4.8 mg/ml CNx/Ni2P, at 20 mg/ml polyethylene terephthalate, at pre-treated 20 mg/ml polylactic acid, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively (Table 2).

The photoreforming of pre-treated polyethylene terephthalate and pre-treated polylactic acid with CNx/Ni2P was obtained at Table 3.Photoreforming experimental conditions was optimized at ultra-sonicated 4.8 mg/ml CNx/Ni2P, at pre-treated 50 mg/ml polymer, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at 24 h, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively. 

Table 3: Photoreforming of pre-treated polyethylene terephthalate and pre-treated polylactic acid with CNx/Ni2P (Experimental conditions: at ultra-sonicated 4.8 mg/ml CNx/Ni2P, at pre-treated 50 mg/ml polymer, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at 24 h, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively).

The maximum 123.75 ± 11.92 µmol H2 / gsub H2(g) production yield was measured during photoreforming process for polyethylene terephthalate after 60 h photoreforming solar irradiation time, at ultra-sonicated 4.8 mg/ml CNx/Ni2P, at pre-treated 50 mg/ml polymer, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively (Table 3).  

The maximum 267.41 ± 24.65 µmol H2 / gsub H2(g) production yield was recorded during photoreforming process for polylactic acid after 60 h photoreforming solar irradiation time, at ultra-sonicated 4.8 mg/ml CNx/Ni2P, at pre-treated 50 mg/ml polymer, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively (Table 3). The stoichiometric H2 conversion calculations for polyethylene terephthalate and polylactic acid were calculated at Table 4. The maximum 6.57 ± 0.87Percentage stoichiometric H2 conversion yield was measured for polyethylene terephthalate during photoreforming process after 60 h photoreforming solar irradition time, at 4.8 mg/ml CNx/Ni2P, at 20 mg/ml polyethylene terephthalate, at 50 mg/ml polymer, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively (Table 4).

Table 4: Stoichiometric H2 conversion calculations (Experimental conditions: 4.8 mg/ml CNx/Ni2P, at pre-treated 20 mg/ml polyethylene terephthalate, at pre-treated 20 mg/ml polylactic acid, at 50 mg/ml polymer, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at 24 h, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively).

The maximum 2.43 ± 0.38Percentage stoichiometric H2 conversion yield was observed for polylactic acid during photoreforming process after 60 h photoreforming solar irradition time, at 4.8 mg/ml CNx/Ni2P, at 20 mg/ml polylactic acid, at 50 mg/ml polymer, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively (Table 4). Values reported for CdS/CdOx under the same conditions were 16.6 ± 1.0Percentage for polyethylene terephthalate and 38.8 ± 4.0Percentage for polylactic acid during photoreforming process (Uekert et al., 2018). It should also be noted that, consistent with previous reports, these calculations assume that only the aliphatic portion of the polyethylene terephthalate is oxidized during photoreforming process (Uekert et al., 2018). Comparison of photoreforming of polyethylene terephthalate and polylactic acid over CNx/Ni2P and H2NCNx/Ni2P were shown at Figure 8. 11, 19, 33, 55, 67 and 79 μmol H2 / gsub H2(g) yields for polyethylene terephthalate over CNx/Ni2P were observed after 5, 10, 20, 30, 40 and 50 h photoreforming solar irradiation times, respectively, at 4.8 mg/ml CNx/Ni2P photocatalyst, at pre-treated 20 mg/ml polyethylene terephthalate, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively (Figure 8a). The maximum 96 μmol H2 / gsub H2(g) yields for polyethylene terephthalate over CNx/Ni2P were obtained after 60 h photoreforming solar irradiation time, at 4.8 mg/ml CNx/Ni2P photocatalyst, at pre-treated 20 mg/ml polyethylene terephthalate, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively (Figure 8a). 5, 21, 38, 42, 44 and 49 μmol H2 / gsub H2(g) yields for polyethylene terephthalate over H2NCNx/Ni2P were measured after 5, 10, 20, 30, 40 and 50 h photoreforming solar irradiation times, respectively, at 4.8 mg/ml CNx/Ni2P photocatalyst, at pre-treated 20 mg/ml polyethylene terephthalate, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively (Figure 8a). The maximum 57 μmol H2 / gsub H2(g) yields for polyethylene terephthalate over H2NCNx/Ni2P were obtained after 60 h photoreforming solar irradiation time, at 4.8 mg/ml CNx/Ni2P photocatalyst, at pre-treated 20 mg/ml polyethylene terephthalate, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively (Figure 8a).

(a)

(b)

Figure 8: Comparison of photoreforming of (a) polyethylene terephthalate and (b) polylactic acid over CNx/Ni2P and H2NCNx/Ni2P. Experimental conditions: at 4.8 mg/ml CNx/Ni2P photocatalyst, at pre-treated 20 mg/ml polyethylene terephthalate, at pre-treated 20 mg/ml polylactic acid, at 4 ml aqueous 1M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at 60 h, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively.

15, 32, 66, 110, 143 and 165 μmol H2 / gsub H2(g) yields for polylactic acid over CNx/Ni2P were observed after 5, 10, 20, 30, 40 and 50 h photoreforming solar irradiation times, respectively, at 4.8 mg/ml CNx/Ni2P photocatalyst, at pre-treated 20 mg/ml polylactic acid, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively (Figure 8b). The maximum 182 μmol H2 / gsub H2(g) yields for polylactic acid over CNx/Ni2P were obtained after 60 h photoreforming solar irradiation time, at 4.8 mg/ml CNx/Ni2P photocatalyst, at pre-treated 20 mg/ml polylactic acid, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively (Figure 8b). 27, 51, 100, 118, 136 and 147 μmol H2 / gsub H2(g) yields for polylactic acid over H2NCNx/Ni2P were measured after 5, 10, 20, 30,40 and 50 h photoreforming solar irradiation times, respectively, at 4.8 mg/ml CNx/Ni2P photocatalyst, at pre-treated 20 mg/ml polylactic acid, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively (Figure 8b). The maximum 173 μmol H2 / gsub H2(g) yields for polylactic acid over H2NCNx/Ni2P were obtained after 60 h photoreforming solar irradiation time, at 4.8 mg/ml CNx/Ni2P photocatalyst, at pre-treated 20 mg/ml polylactic acid, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively (Figure 8b).

3. The By-Products Measurements of Polyethylene Terephthalate and Polylactic Acid 

The GC-MS results was showed that both polyethylene terephthalate and polylactic acid form a variety of oxidation products after 12 h and 24 h photoreforming solar irradiation times, at 4.8 mg/ml CNx/Ni2P, at 20 mg/ml polyethylene terephthalate, at pre-treated 20 mg/ml polylactic acid, at 50 mg/ml polymer, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at 24 h at AM 1.0G, at 150 mW/cm2, at 25°C, respectively (Table 5). 

Table 5: H2(g) production during photoreforming of oxidation intermediates with CNx/Ni2P from GC-MS measurements results (Experimental conditions: at 4.8 mg/ml CNx/Ni2P, at pre-treated 20 mg/ml polyethylene terephthalate, at pre-treated 20 mg/ml polylactic acid, at 50 mg/ml polymer, at 4 ml aqueous 1M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at 24 h at AM 1.0G, at 150 mW/cm2, at 25°C, respectively).

The maximum 4.85 ± 0.62, 88.37 ± 10.74, 26.55 ± 1.95, 21.94 ± 1.86, 75.30 ± 9.34, 60.07 ± 5.11 and 14.61 ± 2.14 μmol H2 / gsub H2(g) production yields were obtained for Acetate, Ethylene glycol, Formate, Glycolate, Glyoxal, Lactate and Terephthalate oxidation intermediates, respectively, after 24 h photoreforming solar irradiation times, at 4.8 mg/ml CNx/Ni2P, at 20 mg/ml polyethylene terephthalate, at pre-treated 20 mg/ml polylactic acid, at 50 mg/ml polymer, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at 24 h at AM 1.0G, at 150 mW/cm2, at 25°C, respectively (Table 5). The photoreforming process of lactic acid (the monomer of polylactic acid) is also faster on CNx/Ni2P (47.43 ± 4.05 μmol H2 /gsub. h, after 24 h photoreforming solar irradiation time at Table 5) than a reported H2NCNx/WS2 system in H2O (0.50 μmol H2 /gsub. h) (Hou et al., 2014). Quantification of organic oxidation intermediates for polyethylene terephthalate and polylactic acid with CNx/Ni2P after 7 days photoreforming process from ICP-MS measurements results were recorded at Table 6. 126 nmol Acetate, 131 nmol Formate, 5 nmol Glycolate and 6200 nmol Glyoxal organic oxidation intermediates for polyethylene terephthalate with CNx/Ni2P nanocatalyst were found after 7 days photoreforming solar irradiation time, at 4.8 mg/ml CNx/Ni2P, at 20 mg/ml polyethylene terephthalate, at 50 mg/ml polymer, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively (Table 6).

Table 6: Quantification of organic oxidation intermediates for polyethylene terephthalate and polylactic acid with CNx/Ni2P nanocatalyst after 7 days photoreforming process from ICP-MS measurements results (Experimental conditions: at 4.8 mg/ml CNx/Ni2P, at 20 mg/ml polyethylene terephthalate, at 50 mg/ml polymer, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively).

67 nmol Acetate and 63 nmol Formate organic oxidation intermediates for polylactic acid with CNx/Ni2P nanocatalyst were obtained after 7 days photoreforming solar irradiation time, at 4.8 mg/ml CNx/Ni2P, at pre-treated 20 mg/ml polylactic acid, at 50 mg/ml polymer, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively (Table 6).

The maximum 41.40 ± 5.10 and 48.60 ± 3.12 µmol H2 / gsub yields were measured for CNx=20 mg/ml and for Ni2P=20 mg/ml, respectively, with photoreforming process, at ultrasonicated 4.8 mg/ml CNx/Ni2P nanocatalyst, at pre-treated 20 mg/ml polyethylene terephthalate, at pre-treated 20 mg/ml polylactic acid, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at 24 h, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively.

The maximum 18.26 ± 1.18 and 52..41 ± 7.29 µmol H2 / gsub H2(g) production yields were found for non-sonicated CNx/Ni2P and ultra-sonicated CNx/Ni2P nanocatalyst, respectively, with photoreforming process, after 24 h photoreforming solar irradition time, at 4.8 mg/ml CNx/Ni2P, at 20 mg/ml polyethylene terephthalate, at pre-treated 20 mg/ml polylactic acid, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively. The maximum 123.75 ± 11.92 and 267.41 ± 24.65 µmol H2 / gsub H2(g) production yield was measured for polyethylene terephthalate and polylactic acid, respectively, with photoreforming process, after 60 h photoreforming solar irradiation time, at ultra-sonicated 4.8 mg/ml CNx/Ni2P, at pre-treated 50 mg/ml polymer, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively. The maximum 6.57 ± 0.87Percentage and 2.43 ± 0.38Percentage stoichiometric H2 conversion yields were observed for polyethylene terephthalate and polylactic acid, respectively, with photoreforming process, after 60 h photoreforming solar irradition time, at 4.8 mg/ml CNx/Ni2P, at 20 mg/ml polyethylene terephthalate, at 20 mg/ml polylactic acid, at 50 mg/ml polymer, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively. The maximum 96 and 57 μmol H2 / gsub H2(g) yields for polyethylene terephthalate were obtained over CNx/Ni2P and H2NCNx/Ni2P, respectively, with photoreforming process, after 60 h photoreforming solar irradiation time, at 4.8 mg/ml CNx/Ni2P photocatalyst, at pre-treated 20 mg/ml polyethylene terephthalate, at 4 ml aqueous 1 M KOH, at 1200 W Xe solar lamp, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively. The maximum 182 and 173 μmol H2 / gsub H2(g) yields for polylactic acid were observed over CNx/Ni2P and H2NCNx/Ni2P, respectively, with photoreforming process, after 60 h photoreforming solar irradiation time, at 4.8 mg/ml CNx/Ni2P photocatalyst, at pre-treated 20 mg/ml polylactic acid, at 4 ml aqueous 1 M KOH, at 1200 W Xe solar lamp, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively. The maximum 4.85 ± 0.62, 88.37 ± 10.74, 26.55 ± 1.95, 21.94 ± 1.86, 75.30 ± 9.34, 60.07 ± 5.11 and 14.61 ± 2.14 μmol H2 / gsub H2(g) production yields were obtained for Acetate, Ethylene glycol, Formate, Glycolate, Glyoxal, Lactate and Terephthalate oxidation intermediates, respectively, with photoreforming process, after 24 h photoreforming solar irradiation times, at 4.8 mg/ml CNx/Ni2P, at 20 mg/ml polyethylene terephthalate, at pre-treated 20 mg/ml polylactic acid, at 50 mg/ml polymer, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively. 126 nmol Acetate, 131 nmol Formate, 5 nmol Glycolate and 6200 nmol Glyoxal organic oxidation intermediates for polyethylene terephthalate with CNx/Ni2P nanocatalyst were found with photoreforming process, after 7 days photoreforming solar irradiation time, at 4.8 mg/ml CNx/Ni2P, at 20 mg/ml polyethylene terephthalate, at 50 mg/ml polymer, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively. 67 nmol Acetate and 63 nmol Formate organic oxidation intermediates for polylactic acid with CNx/Ni2P nanocatalyst were observed with photoreforming process, after 7 days photoreforming solar irradiation time, at 4.8 mg/ml CNx/Ni2P, at pre-treated 20 mg/ml polylactic acid, at 50 mg/ml polymer, at 4 ml aqueous 1 M KOH, at 10 ml internal volume of sealed photoreactor under anaerobic conditions, at 1200 W Xe solar lamp, at AM 1.0G, at 150 mW/cm2, at 25°C, respectively. High H2(g) production efficiency was obtained by photoreforming process for the production of H2(g) from real polyethylene terephthalate and polylactic acid wastes using CNx/Ni2P nanocatalyst. Photoreforming process is a very effective, easy to apply, economical and environmentally friendly method for the removal of plastic and microplastic wastes. 

This research study was undertaken in the Environmental Microbiology Laboratories at Dokuz Eylül University Engineering Faculty Environmental Engineering Department, Izmir, Turkey. The authors would like to thank this body for providing financial support.