Synthesis, Characterization of the Novel Heterojunction Photocatalyst Sm₂NdSbO₇/BiDyO₃ for Efficient Photodegradation of Methyl Parathion

Abstract

A new catalyst, Sm₂NdSbO₇, was synthesized for the first time by solid-phase sintering. The study utilized X-ray diffraction, transmission electron microscope energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy to examine the structural characteristics of monocrystal BiDyO₃, monocrystal Sm₂NdSbO₇ and Sm₂NdSbO₇/BiDyO₃ heterojunction photocatalysts (SBHP) prepared by solid-phase sintering. The Sm₂NdSbO₇ photocatalyst owned a pyrochlorite structure, belonged to the face-centered cubic crystal system, possessed a space group of Fd3m and a bandgap width of 2.750 eV. After 145 min of visible light irradiation (145-VLIRD), the removal rate (RMR) of methyl parathion (MP) or total organic carbon of SBHP was 100% or 97.58%, respectively. After 145-VLIRD, the photocatalytic degradation rates of SBHP to MP were 1.13 times, 1.20 times, and 2.43 times higher than those of the Sm₂NdSbO₇ photocatalyst, the BiDyO₃ photocatalyst, and the nitrogen-doped TiO₂ catalyst, respectively. The experimental results showed that SBHP had good photocatalytic activity. After four cycles of cyclic degradation experiments with SBHP, the elimination rates of MP were 98.76%, 97.44%, 96.32%, and 95.72%, respectively. The results showed that SBHP had good stability. Finally, the possible degradation pathways and degradation mechanisms of MP were speculated. In this study, we successfully developed a high-efficiency heterojunction catalyst which responded to visible light and possessed significant photocatalytic activity. The catalyst could be used in photocatalytic reaction system for eliminating the harmful organic pollutants from wastewater.

1. Introduction

Global population growth has put enormous pressure on the food system; thus, more pesticides are used to increase crop yields to meet food demand. Organophosphorus pesticides are mainly used for controlling plant diseases, insect pests, weeds, etc., and at the same time, food production could be increased. Organophosphorus pesticides have the advantages of economy, high efficiency and convenience of use. In agricultural production, the widespread use of organophosphorus pesticides led to different degrees of residues in crops, resulting in water pollution [1,2,3]. The residues of organophosphorus pesticides might cause acute poisoning. Therefore, it was urgent to find an effective method for removing pesticide residues from wastewater and purifying water resources [4].

Methyl parathion (MP), one of the most widely used organophosphorus pesticides in agriculture, could effectively control a variety of pests. MP was highly toxic and harmful to the nervous systems of humans and animals. In addition, MP was easily soluble in water; once the excess MP was dissolved in the underground water, it would cause serious environmental pollution. For the degradation of MP, the traditional methods mainly included chemical oxidation and biological degradation. However, there were several drawbacks associated with these approaches. For example, the chemical oxidation method was complex and required a large number of chemical reagents, and it also produced a large amount of waste liquid, which might lead to secondary pollution. Although the biodegradation method could effectively degrade organic matter, it required specific microbial populations, and the degradation rate was relatively slow [5,6,7,8]. Therefore, it was necessary to find a more effective degradation method for reducing the impact of its residues on the environment and humans.

Compared with other degradation methods for the degradation of MP, photocatalytic technology was a more promising choice. Photocatalysis is a chemical reaction process that uses light energy to stimulate catalysts. This technology has a wide range of applications in science and technology. Moreover, it could use solar energy, which is an environmentally friendly and energy-saving technology [9,10]. The principle of photocatalytic technology was mainly based on the photocatalytic activity of photocatalysts. When incident light with energy greater than the band gap width (Eg) was used to irradiate the photocatalysts, the electrons on the valence band of the photocatalysts were excited by the incident light and transited to the conduction band. As a result, negatively charged and highly reactive electrons formed on the conduction band, and correspondingly, positively charged holes could be generated on the valence band [11]. These photogenerated electrons and holes participated in the redox reactions of organic matter at the surface active sites and decomposed organic pollutants into harmless substances such as carbon dioxide and water, thereby achieving the degradation of organic pollutants. Therefore, the development of a photocatalyst with high degradation efficiency was the key to the treatment of MP, which is derived from pesticide wastewater (PW).

Traditional commercial metal oxide photocatalysts such as TiO₂ and ZnO could only be stimulated by ultraviolet light or near-ultra-violet light radiation due to the band gap. These materials possessed other limitations, such as weak light scattering properties and the presence of point defects [12,13]. In order to effectively utilize the largest proportion of the solar spectrum in the visible light region (λ > 400 nm), it was feasible to construct a composite material system with a more complex construction compared with the single metal oxide [14,15]. Based on the previous reports, A₂B₂O₇ and ABO₃ compounds showed better photocatalytic performance under visible light irradiation (VLIRD) [16]. The A₂B₂O₇ and ABO₃ compounds were characterized by the substitution of metal ions to improve the photocatalytic efficiency while maintaining their structure. Xing et al. [17,18] prepared Bi₂Sn₂O₇ and Y₂Ti₂O₇, which showed good photocatalytic performance under VLIRD. Wang et al. studied the ABO₃-type (A = Ca, Sr, Ba; B = Ti, Zr) catalyst, which indicated that the structure had the potential to improve performance by changing the structure [19].

In a prior investigation [20], it was determined that Bi₂InNbO₇ exhibited a pyrochlore structure and a face-centered cubic crystal system. The structure of Bi₂InNbO₇ had the capability to improve photocatalytic activity. We anticipated that replacing Sm³⁺ and Bi³⁺ in Bi₂InNbO₇, Nd³⁺ and In³⁺ in Bi₂InNbO₇, and Sb⁵⁺ and Nb⁵⁺ in Bi₂InNbO₇ might potentially boost the carrier concentration based on the study provided. We hypothesized that elevating the carrier concentration would yield an improved Sm₂NdSbO₇ photocatalyst with enhanced photocatalytic capabilities.

In the past, many researchers had studied various strategies for improving the photocatalytic efficiency of photocatalysts [21,22,23,24,25], such as proper surface engineering [26], ion doping [27], and the formation of semiconductor heterojunctions with metals [28,29,30,31,32,33,34] or other semiconductors. Among these strategies, the construction of semiconductor heterojunctions has received widespread attention owing to its perfect effect on improving photocatalytic activity [35,36,37,38,39,40,41,42]. In addition, the construction of heterostructural photocatalysts has shown great prospects for improving photocatalytic performance [43,44,45,46,47,48,49]. The interlaced band structure in the heterostructure formed a tight interface, resulting in the establishment of a strong internal electric field near the interface. This promoted the efficient transfer and separation of photocharged load charges [50,51]. Higher photocatalytic efficiency could also be obtained by constructing many different types of heterojunction catalysts using different methods [52]. Baaloudj and Nguyen-Tri et al. discussed the formation, morphological modification, doping, and hybridization processes of advanced engineering strategies for designing silicate-based photocatalysts, including heterojunctions. Each of these strategies provided important implications for our research [53]. We wanted to create a photocatalyst by constructing a heterojunction. The SBHP was synthesized for the first time, and its structural type was Z-scheme heterojunction. The SBHP was synthesized for the first time, and its structural type is Z-scheme heterojunction. The removal rate of the SBHP prepared by us reached 98% under VLIRD for 120 min, which was better than other reports. For example, the GO-Fe₃O₄/Bi₂MoO₆ catalyst and NiO/Bi₂MoO₆ catalyst prepared by Nasiripur, P et al. [54,55] achieved a removal rate of 95% for MP derived from PW under the same illumination time.

This study utilized X-ray diffraction (XRD), transmission electron microscope energy dispersive X-ray spectroscopy (TEM-EDS), and X-ray photoelectron spectroscopy (XPS) to examine the structural characteristics of monocrystal BiDyO₃ and single-phase Sm₂NdSbO₇ created through high-temperature solid-phase sintering. The elimination effectiveness of microplastics was measured during very low input rate digestion using several materials such as Sm₂NdSbO₇, BiDyO₃, N-doped TiO₂ (N-T), and SBHP. This work is intended to create a novel heterostructural catalyst to break down MP produced from PW using VLIRD. To our knowledge, no work has synthesized the catalyst Sm₂NdSbO₇, and this is the first time that it has been used in heterojunction photocatalytic applications. This work introduced a unique approach by utilizing high-temperature solid-phase synthesis to create a new Sm₂NdSbO₇ nanocatalyst and SBHP for the first time. An efficient photocatalyst responsive to visible light was developed, demonstrating great activity in removing MP originating from PW. The SBHP demonstrated superior efficiency in degrading organic pollutants originating from PW while ensuring safety.

2. Findings and Analysis

2.1. XRD Analysis

Figure 1 shows that the catalyst was well crystalline with no heterophase present. Data analysis was conducted using the Rietveld analysis approach in the Materials Studio application. It could be inferred from Figure 2a and Figure 3a that Sm₂NdSbO₇ with a Rp factor of 3.21% and BiDyO₃ with a Rp factor of 4.22% exhibited good crystallization. The final structural refinement of Sm₂NdSbO₇ confirmed agreement between observed and calculated intensities of the pyrochlore-type structure. The crystal system was cubic with space group Fd3m, resulting in a lattice parameter of 10.58142 angstroms. The crystal structure of BiDyO₃ was revised using the Rietveld method based on the XRD data from Figure 3. The final refinement for BiDyO₃ showed excellent agreement between the observed and estimated intensities. BiDyO₃ possessed a fluorite-type structure with a face-centered cubic crystal system and belonged to the space group Fm3m. The lattice parameter a for BiDyO₃ in the improved finding was 5.455 angstroms. Figure 2b displays the atomic arrangement of Sm₂NdSbO₇, whereas Figure 3b illustrates the atomic configurations of BiDyO₃.

Table 1. Structural parameters of Sm₂NdSbO₇.

Atom	x	y	z	Occupation Factor
Sm	0	0	0	1
Nd	0.5	0.5	0.5	0.5
Sb	0.5	0.5	0.5	0.5
O(1)	−0.185	0.125	0.125	1
O(2)	0.125	0.125	0.125	1

displays the atomic coordinates and structural characteristics of Sm₂NdSbO₇.

Table 2. Structural parameters of BiDyO₃.

Atom	x	y	z	Occupation Factor
Bi	0.5	0.5	0.5	1
Dy	0	0	0	1
O	0.25	0	0	0.5

displays the atomic coordinates and structural characteristics of BiDyO₃.

The x-coordinate of the O(1) atom in the pyrochlore-type A₂B₂O₇ compound (with cube syngony and space group Fd3m) serves as an indicator of changes in the crystal structure. When the length of the six A−O(1) bonds equals the length of the two A−O(2) bonds, the x-coordinate is 0.375. Information on MO₆ (M = Nd³⁺ and Sb⁵⁺) could be derived from the x value [56]. The crystal structure of Sm₂NdSbO₇ exhibited a clear deformation of the MO₆ (M = Nd³⁺ and Sb⁵⁺) octahedral due to an x-value shift of 0.375. To prevent the recombination of photogenerated electrons with photoinduced holes during the PHDE of MP under VLIRD, charge separation was necessary. Scientific reports by Inoue and Kudo suggest that local distortion of the MO₆ octahedron in photocatalysts like BaTi₄O₉ and Sr₂M₂O₇ (M = Nb⁵⁺ and Ta⁵⁺) is crucial for inhibiting charge recombination and enhancing photocatalytic activity [57,58]. The deformation of the MO₆ (M = Nd³⁺ and Sb⁵⁺) octahedron in the crystal structure of Sm₂NdSbO₇ could be utilized to improve photocatalytic activity. The structure of Sm₂NdSbO₇ is a three-dimensional mesh composed of MO₆ octahedra (where M = Nd³⁺ and Sb⁵⁺) that share angles. Sm³⁺ ions connected MO₆ octahedra (where M = Nd³⁺ and Sb⁵⁺) into chains. There were two different Sm−O bond lengths observed: six Sm−O(1) bonds were 2.842 Å long, while two Sm−O(2) bonds were 2.479 Å long. Six bond lengths of M−O (M = Nd³⁺ and Sb⁵⁺) were 2.195 Å each, whereas M−Sm (M = Nd³⁺ and Sb⁵⁺) bond lengths measured 3.565 Å. The bond angle in the Sm₂NdSbO₇ crystal structure, including Nd³⁺ and Sb⁵⁺ ions, was measured at 139.424°. The bond angle between Sm-M-Sm (M = Nd³⁺ and Sb⁵⁺) was measured at 135.721° in the crystal structure of Sm₂NdSbO₇. The bond angle in the Sm₂NdSbO₇ crystal structure involving Sm-M-O (M = Nd³⁺ and Sb⁵⁺) was measured at 133.680°. Research on luminescence qualities determined that an M-O-M bond angle closer to 180° resulted in a higher degree of delocalized excited states [59]. The study found that the angle between MO₆ (M = Nd³⁺ and Sb⁵⁺) octahedra with common angles, such as the M-O-M bond angle in Sm₂NdSbO₇, significantly influenced the photocatalytic activity of Sm₂NdSbO₇. As the M-O-M bond angle approached 180°, the mobility of photogenerated electrons and holes increased. The movement of electrons and holes generated by light impacts the efficiency of photocatalysis by influencing the likelihood of these particles reaching the reaction site on the catalyst’s surface.

2.2. FTIR Analysis

Figure 4 shows distinct absorption peaks in the FTIR spectra of SBHP, Sm₂NdSbO₇, and BiDyO₃. The peaks identified were related to Sm−O, Nd−O, Sb−O, Sb−O−Sb, Bi−O, and Dy−O bonds. The stretching vibration (SV) of Sm−O occurred at 520 cm⁻¹ [60,61], whereas the SV of Nd−O was seen at 630 cm⁻¹ [62]. The Bi−O bending vibration (BV) peak was observed at 428 cm⁻¹ [63], and the Dy−O SV peak was found at 613 cm⁻¹ [64]. The Sb−O BV was detected at 458 cm⁻¹ and 583 cm⁻¹ [65]. The BV of Sb−O−Sb was shown by peaks at 658 cm⁻¹ [66]. The wide peaks found between 3431 cm⁻¹ and 3576 cm⁻¹ represent the SV of O−H groups from chemisorbed water molecules [67,68]. The peak at 1632 cm⁻¹ represents the BV mode of the O−H groups [69]. The bands found between 1379 cm⁻¹ and 1632 cm⁻¹ were identified as vibrations of C−H bonds from adsorbed water [70,71].

2.3. Raman Analysis

Figure 5 shows the Raman spectra of SBHP, Sm₂NdSbO₇, and BiDyO₃. The Raman spectra of Sm₂NdSbO₇ displayed distinctive modes such as the Ag internal Sm−O stretching modes at 562 cm⁻¹ [72] and peaks at 363 cm⁻¹ related to the SV of Nd−O bonds [73]. The peaks at 504 cm⁻¹ and 622 cm⁻¹ are likely associated with the BV of Sb−O and Sb−O−Sb [74,75]. The Raman spectra of BiDyO₃ displayed a wide band at 131 cm⁻¹ and 641 cm⁻¹, corresponding to the SV of Bi−O and Dy−O, respectively [76,77]. Notably, the Raman spectra of SBHP exhibited strong peaks encompassing the distinct absorption peaks of both Sm₂NdSbO₇ and BiDyO₃, including peaks at 134 cm⁻¹, 357 cm⁻¹, 503 cm⁻¹, 558 cm⁻¹, 636 cm⁻¹ and 641 cm⁻¹.

2.4. UV–Vis Diffuse Reflectance Spectra

Figure 6 displays the absorption spectra of SBHP, Sm₂NdSbO₇, and BiDyO₃ samples. The absorption edges were observed at 551 nm, 450 nm and 602 nm in the visible range of the spectra, as shown in Figure 6. The band gap energies of crystalline semiconductors could be calculated by identifying the point where the photon energy (hν) axis intersects with the extrapolated line from the linear section of the absorption edge of the Kubelka–Munk function (1) [78].

$$\frac{{\left[1-{\mathrm{R}}_{\mathrm{d}}\left(\mathrm{h}\mathsf{\nu }\right)\right]}^2}{2{\mathrm{R}}_{\mathrm{d}}\left(\mathrm{h}\mathsf{\nu }\right)}=\frac{\mathsf{\alpha }\left(\mathrm{h}\mathsf{\nu }\right)}{\mathrm{S}}$$

(1)

where S was the scattering factor, R_d was the diffuse reflectance, and α represented the absorption coefficient of radiation.

The optical absorption near the band edge of the crystalline semiconductors obeyed Equation (2) [79,80]:

Ahν = A (hν − E_g)ⁿ

(2)

A, α, E_g, and ν symbolize the proportional constant, absorption coefficient, band gap, and light frequency, respectively. The variable “n” dictates the nature of the transition in a semiconductor inside this equation. E_g and n could be determined using the following steps: (1) Plotting the natural logarithm of (αhν) against the natural logarithm of (hν-Eg) using an estimated value of Eg; (2) determining the value of n based on the slope of this graph; (3) improving the value of Eg by graphing (αhν)^1/n against hν and extending the plot until (αhν) ^1/n = 0 [81,82]. The Eg values of SBHP, Sm₂NdSbO₇, and BiDyO₃ were determined to be 2.250 eV, 2.750 eV, and 2.060 eV, respectively, using the approach described above. The approximate value of n was around 2, and the optical transition was classified as an indirect transition.

2.5. Performance Characterization of Sm₂NdSbO₇/BiDyO₃ Heterojunction Photocatalysts

Figure 7 shows the XPS measurement spectra of SBHP, Sm₂NdSbO₇ and BiDyO₃. The presence of Sm, Nd, Sb, Bi, Dy and O elements in SBHP could be clearly seen, which proved the successful preparation of heterojunction structure. An observed carbon signal was identified as adventitious hydrocarbon, used as a calibration.

It could be seen from Figure 8 that various element peaks with specific binding energies were obtained; demonstrably, the Sm 3d_5/2 peak of samarium for Sm₂NdSbO₇ was situated at 1084.09 eV, and the Nd 3d_5/2 peak of neodymium for Sm₂NdSbO₇ was situated at 982.62 eV. The Sb 4d_5/2 peak of antimony for Sm₂NdSbO₇ was situated at 35.09 eV. The Bi 4d_5/2 peak of the bismuth for BiDyO₃ was situated at 442.44 eV. The Dy 4d_5/2 peak of the dysprosium for BiDyO₃ was situated at 158.95 eV. Comparison with the XPS map of SBHP found that these peaks showed a slight shift toward higher binding energy. These shifts confirmed the presence of a strong interfacial interaction between Sm₂NdSbO₇ and BiDyO₃, potentially resulting from electron transfer and delocalization between these two components in heterojunction photocatalytic materials.

Figure 8f displays the separated O 1s spectra of SBHP and Sm₂NdSbO₇. The peaks seen at 529.97 eV and 529.71 eV were attributed to lattice oxygen. The peaks at 531.12 eV and 530.86 eV represented the signal coming from hydroxyl groups. The peaks at 532.29 eV and 532.03 eV were related to the signal of oxygen vacancies. The deconvoluted O 1s peaks in the SBHP sample showed noticeable alterations compared to their positions in the pure Sm₂NdSbO₇ sample. The shifts indicated more evidence of interfacial interactions between Sm₂NdSbO₇ and BiDyO₃ species. The spin-orbit disassociation numerical value between Sb 3d_5/2 and Sb 3d_3/2 was consistently measured as 7.1 eV for both Sm₂NdSbO₇ and SBHP, confirming the sole occurrence of Sb⁵⁺ species [83,84].

The XPS spectrum of SBHP indicated the presence of Nd, Sm, Bi, Sb, Dy, and O components in the synthesized SBHP. The XPS examination results indicated that the oxidation states of Nd, Sm, Bi, Sb, Dy, and O ions were +3, +3, +3, +5, +3, and −2, respectively. The surface elemental analysis results indicated an average atomic ratio of Sm:Nd:Sb:Bi:Dy:O of 731:365:368:324:326:3593. The samples of SBHP have atomic ratios of 1.99:0.99:1.00 for Sm:Nd:Sb and 0.99:1.00 for Bi:Dy. The elevated oxygen concentration was a result of the significant oxygen adsorption on the surface of SBHP. No hetero-peaks were detected in the XPS peak of the SBHP, indicating the absence of additional components.

Figure 9 and Figure 10 show that the bigger hexagonal particles are from Sm₂NdSbO₇, while the smaller circular and quadrangular particles are from BiDyO₃. Figure 9 and Figure 10 show that the Sm₂NdSbO₇ particles were enveloped by smaller BiDyO₃ particles, and the two particles were closely connected, suggesting the effective synthesis of SBHP. Sm₂NdSbO₇ exhibited an octahedral shape. Figure 9 displays experimental data revealing that BiDyO₃ exhibited a consistent spherical shape and even particle distribution. The particle size of BiDyO₃ was approximately 446 nm, whereas the particle size of Sm₂NdSbO₇ was around 775 nm.

The TEM-EDS investigation results indicated the absence of impurity elements in the SBHP compound. The pure phase of Sm₂NdSbO₇ matched the XRD data presented in Figure 1. The SBHP was found to contain neodymium, samarium, antimony, bismuth, dysprosium, and oxygen based on the analysis of Figure 10 and Figure 11. The previous findings aligned with the XPS results of the SBHP, as depicted in Figure 7 and Figure 8.

The atomic ratio of Sm:Nd:Sb:Bi:Dy:O in the SBHP, as determined by the EDS spectra, was 853:385:386:305:331:7830, which matched the XPS results of the SBHP. The atomic ratio between Sm₂NdSbO₇ and BiDyO₃ was around 65:53. Based on the results provided, we may infer that the SBHP exhibited good purity given our preparation conditions. The specific surface area of SBHP heterojunction catalyst is 6.28 m²·g⁻¹, that of Sm₂NdSbO₇ is 5.19 m²·g⁻¹, that of BiDyO₃ is 4.15 m²·g⁻¹, and that of N-T is 106.48 m²·g⁻¹. This indicated that the catalytic activity and catalytic efficiency of SBHP were increased due to the increase of surface active sites.

2.6. Electrochemical Characterization

Electrochemical impedance mapping is a crucial technique for analyzing the movement of photogenerated electrons and photoholes in the prepared photocatalyst at the solid/electrolyte interface. Decreasing the arc radius increases the efficiency of photogenerated electron and photogenerated hole transport in the photocatalyst. Figure 12 illustrates that the arc radius diameter sequence is BiDyO₃ > Sm₂NdSbO₇ > SBHP. The results indicated that the prepared SBHP demonstrated superior separation of photogenerated electrons and holes, as well as faster interfacial charge migration.

2.7. Optical Characterization

The influence of the sample on the separation of photogenerated charge carriers (PCC) was examined using electrochemical impedance spectroscopy (EIS) techniques. Figure 13 demonstrates that the SBHP exhibits the highest intensity of photocurrent response when compared to Sm₂NdSbO₇ and BiDyO₃, as shown by the results. The enhanced photocurrent in SBHP resulted from the efficient diffusion of photoexcited electrons and the rapid transfer of photoexcited holes to the BiDyO₃ surface. The event occurred because of the electric potential difference between the valence bands of Sm₂NdSbO₇ and BiDyO₃ in the SBHP composite. The enhanced photocurrent response in SBHP indicated effective separation of PCC and extended durability in comparison to Sm₂NdSbO₇ and BiDyO₃ in the photodegradation process. The observations clarified the improved photocatalytic efficiency achieved with SBHP [85,86].

UPS spectra were performed to determine the ionization potential of Sm₂NdSbO₇ and BiDyO₃. UPS analysis could determine the valence band potentials of both p-type and n-type semiconductor materials. Figure 14 shows the initial (Ei) and maximum (Ecutoff) binding energies for the semiconductor samples. The measured numerical values were 1.378 eV and 19.965 eV for Sm₂NdSbO₇, and 0.749 eV and 20.471 eV for BiDyO₃. The ionization potentials of Sm₂NdSbO₇ and BiDyO₃ were determined to be 2.613 eV and 1.478 eV, respectively, using an excitation energy of approximately 21.2 eV [87,88]. The conduction band potentials of Sm₂NdSbO₇ and BiDyO₃ were determined to be −0.137 eV and −0.582 eV, respectively. The results provide further support for the mechanistic paradigm described in this study.

2.8. Photocatalytic Activity

In the photocatalytic degradation experiment, the adsorption equilibrium experiment was carried out between −40 min and 0 min, and the adsorption equilibrium experiment was mainly to exclude the influence of photocatalyst adsorption on pollutant concentration. After the adsorption equilibrium was reached, it could be considered that the subsequent decrease in the concentration of pollutants was caused by photocatalytic degradation. N-doped TiO₂ (N-T), a widely recognized visible-light-responsive photocatalyst, was employed as a benchmark to assess and compare the differences in photodegradation efficiency among various catalyst samples. In this study, we chose the organophosphorus pesticide methylparathion, and the potential surface charge present is a negative charge.

Thedata in Figure 15 indicated that using SBHP, the removal rate (RMR) of methyl parathion (MP) from pesticide wastewater (PW) approached 100% after 145 min of visible light irradiation (145-VLIRD). The reaction rate (RTR) was 2.87 × 10⁻⁹ mol·L⁻¹·s⁻¹, with a photon efficiency (PE) of 0.0603%. All subsequent studies adhered to the identical 145-VLIRD protocol. Using Sm₂NdSbO₇ resulted in an 88.24% RMR of MP, with a RTR of 2.54 × 10⁻⁹ mol·L⁻¹·s⁻¹ and a PE of 0.0533%. Using BiDyO₃, the RMR of MP from PW was 83.16%, with a RTR of 2.39 × 10⁻⁹ mol·L⁻¹·s⁻¹ and a PE of 0.0502%. Using N-T as the photocatalyst, MP RMR was 41.16%, with a RTR of 1.18 × 10⁻⁹ mol·L⁻¹·s⁻¹ and a PE of 0.0248%. The results indicated that SBHP could enhance the photodegradation efficiency of MP. Among the other photocatalysts tested, Sm₂NdSbO₇ showed the highest efficiency, followed by BiDyO₃ and N-T. BiDyO₃ exhibited higher efficiency than N-T. The study demonstrated that SBHP had the highest visible photocatalytic activity when compared to Sm₂NdSbO₇, BiDyO₃ and N-T. After 145-VLIRD, the RMR of MP by SBHP was 1.13, 1.20 and 2.43 times higher than that of Sm₂NdSbO₇, BiDyO₃ and N-T photocatalysts, respectively.

The concentration curve (CTC) of MP gradually decreases with the increase of VLIRD time. It could be seen from Figure 16 that MP was degraded by SBHP, Sm₂NdSbO₇, BiDyO₃ and N-T, respectively. The RMR of TOC, which was derived from PW, reached 97.58%, 84.15%, 79.06% and 40.52%, respectively, after 145-VLIRD. In summary, it could be seen from the above results that the RMR of TOC in the presence of SBHP with descending MP was higher than that of Sm₂NdSbO₇, BiDyO₃, or N-T. The above results also showed that in the presence of Sm₂NdSbO₇, the RMR of TOC during the degradation of MP was much higher than that of BiDyO₃ or N-T, which meant that compared with Sm₂NdSbO₇, BiDyO₃, or N-T, SBHP has the greatest efficiency in the degradation of MP.

Figure 17a shows that the RMR of MP reached 98.76%, 97.44%, 96.32% and 95.72% after being irradiated with SBHP for 145-VLIRD following four cycle tests for MP degradation. Figure 17b shows that the RMR of TOC was 96.13%, 95.04%, 94.02%, or 93.11%. Figure 17c shows that when using SBHP for degradation, the RMR of MP was 99.3%, 100% and 98.5%, respectively, at pH values of 3, 7 and 11. This indicated that the pH value had no significant effect on the removal rate. Figure 17a–c show that the experimental findings demonstrated the SBHP’s significant stability.

Figure 17a–c show that after four cycles of deterioration testing under VLIRD, the RMR of MP decreased by 4.28% due to SBHP, the RMR of TOC decreased by 4.47%, and the effect of different pH values decreased by 0.7% and 1.5%. There was no significant difference in degradation efficiency, indicating that the photochemical structure stability of the photocatalyst was maintained.

According to Figure 18a,b, the kinetic constants k obtained from the kinetic curves (K_C) of MP concentration and VLIRD time reached 0.02127 min⁻¹ or 0.01001 min⁻¹ or 0.00836 min⁻¹ or 0.00836 min⁻¹, respectively, using SBHP, Sm₂NdSbO₇, BiDyO₃, or N-T. And the kinetic constant k of TOC concentration (K_TOC) reached 0.02091 min⁻¹ or 0.00868 min⁻¹ or 0.00734 min⁻¹ or 0.00285 min⁻¹.

The K_TOC degradation of MP was lower than the K_C degradation of MP in the same catalyst, suggesting the occurrence of PHDE intermediate products in MP during the PHDE of MP under VLIRD. Compared to the other three photocatalysts, SBHP exhibited superior efficiency in degrading MP.

The results from Figure 19a,b show that in the four-cycle deterioration tests, the kinetic constant k obtained from the kinetic curve of MP concentration and the VLIRD time of SBHP ranged from 0.02127 min⁻¹ to 0.01626 min⁻¹. The kinetic constant k for the degradation test in four cycles using SBHP ranged from 0.01829 min⁻¹ to 0.01439 min⁻¹. The experimental data from Figure 18a,b and Figure 19a,b indicated that the PHDE of MP, produced from PW by SBHP under VLIRD, followed first-order reaction kinetics.

2.9. Mechanism Study

During the initial stage of the photocatalytic experiment, various radical trappers were individually introduced into the MP solution to identify the active substance involved in the degradation of MP. We employed isopropanol (IPA) with captured hydroxyl radicals (•OH), benzoquinone (BQ) with captured superoxide anions (•O₂⁻), and ethylenediaminetetraacetic acid (EDTA) with trapped holes (h⁺). The concentration of IPA, BQ, and EDTA was 0.15 mmol/L, and the dosage of each trapping agents was 1 mL. Figure 20 demonstrates that the addition of IPA, BQ, or EDTA to the MP solution resulted in a reduction of 63.80%, 47.64%, or 34.64% in the RMR of MP compared to the control group. It could be inferred that •OH, H⁺, and •O₂⁻ were all active radicals involved in the breakdown of MP. It could be seen from Figure 20 that the •OH in the MP solution plays a dominant role in degradation by SBHP under VLIRD. The experiment showed that hydroxyl radical was the most effective in oxidizing and eliminating MP derived from PW, compared to superoxide anion or hole.

EPR analysis was used to study the production of •O₂⁻ and •OH in the PHDE process [89,90,91]. We prepared a solution by combining 20 mg of the SBHP sample, 90 µL of DMPO (1 mol/L), and 1 mL of deionized water for the purpose of detecting the •OH radicals or •O₂⁻ radicals generated by SBHP in our experiment. Figure 21 demonstrates that after being exposed to visible light for 10 min, a four-line signal with a 1:2:2:1 intensity ratio, characteristic of the DMPO •OH signal, was identified. In addition, the EPR spectra showed a clear signature of DMPO •O₂⁻ with four conspicuous peaks of equal intensity ratio 1:1:1:1. This observation suggested the presence of superoxide radicals. The results indicated the simultaneous generation of •OH and •O₂⁻. The elevated relative intensity of the EPR signals suggested a higher production of these reactive radicals. The concentration of hydroxyl radicals surpassed the generation of superoxide radicals. The outcomes were consistent with the results of the radical-scavenger tests discussed previously.

A variety of effective characterization techniques were used to thoroughly understand the interfacial carrier dynamics and recombination. The PL spectra in Figure 22 show emission peaks at 470 nm for all samples. The PL emission of the sample may be caused by the recombination of the excitation associated with the defect through the excitation–excitation collision process. After the sample is excited, an electron-hole pair is generated, where the hole is in the valence band or defect-related position and the electron is in the conduction band or defect-related position, both of which emit photons during the recombination process [92,93], thus producing a light emission spectrum as shown in Figure 22. The SBHP has the lowest emission peak intensity, which means the lowest recombination rate of electrons and holes, indicating that the SBHP has the highest catalytic activity. A heterostructured sample could significantly improve the photocatalytic action on MP. Moreover, the study also demonstrated additional proof that SBHP has the most potent photocatalytic properties. Figure 23a–c displays the TRPL spectra of SBHP (τ₁ = 1.652 ns, τ₂ = 146.5 ns, τ_ave = 81.29 ns), which presented a much higher PCC lifetime than Sm₂NdSbO₇ (τ₁ = 1.752 ns, τ₂ = 111.5 ns, τ_ave = 38.49 ns) and BiDyO₃ (τ₁ = 1.61 ns, τ₂ = 36.56 ns, τ_ave = 7.6 ns), which indicated that SBHP was endowed with unbeatable photocatalytic efficacy over the individual Sm₂NdSbO₇ and BiDyO₃.

2.10. Analysis of Possible Photocatalytic Degradation Mechanisms

Figure 24 illustrates that when the SBHP is exposed to visible light, both Sm₂NdSbO₇ and BiDyO₃ could absorb the light and produce electron-hole pairs internally. It is composed of two staggered semiconductor photocatalysts, Sm₂NdSbO₇ and BiDyO₃. After the photo-excitation of the two catalysts to generate electron holes, the photogenerated holes of BiDyO₃ react with the photogenerated electrons of Sm₂NdSbO₇. The electron holes in the two catalysts are retained separately for the redox reaction. The use of this system could not only realize the spatial separation of redox sites but also ensure that the photocatalyst could maintain a suitable valence band position so as to maintain a strong redox reaction ability [94]. Consequently, generating more oxidized radicals like •OH or •O₂⁻ could enhance the degrading efficiency of MP. The conduction band potential of BiDyO₃ was −0.582 eV, higher than the negative value of O₂/•O₂⁻ (−0.33 eV vs. NHE). This suggested that electrons in the conduction band of BiDyO₃ could react with oxygen to form O, leading to the degradation of MP (as illustrated in path 1 in Figure 24). The valence band potential of Sm₂NdSbO₇ was 2.613 eV, adjusted for OH⁻/•OH (2.38 eV vs. NHE), suggesting that the valence band hole of Sm₂NdSbO₇ could oxidize H₂O or OH⁻ to •OH to break down MP, as demonstrated in path 2. The light-induced holes in the valence band of BiDyO₃ or Sm₂NdSbO₇ could directly oxidize MP and degrade it because of their potent oxidizing ability, as demonstrated by path 3. The superior photocatalytic performance of SBHP in degrading MP was primarily due to the effective separation of electrons and holes caused by SBHP. The blue dashed line and orange dashed line indicate the valance band and conduction band charged chemical potential of Sm₂NdSbO₇ and BiDyO₃, respectively. The crimson lines mark the electrochemical potentials of O₂/•O₂⁻ and OH⁻/•OH. The shape mark 1 to 3 represent the three locations where degradation reactions occur.

The intermediates of the PHDE of MP were C₆H₅OH(NO₂) (m/z = 139), C₆H₅OH (m/z = 94), (CH₃O)₃P(S) (m/z = 156), C₆H₄(OH)₂ (m/z = 110), C₆H₃(OH)₃ (m/z = 126), C₆H₄(NH₂)OP(O)(OCH₃)₂ (m/z = 247), and (CH₃O)₂P(O)OH (m/z = 126). Based on the intermediates examined above, a PHDE pathway for MP was proposed. Figure 25 shows that both the oxidation reaction and the hydroxylation reaction of MP were realized during the PHDE. Eventually, MP was converted to small-molecule organic compounds that eventually combined with other organically active groups to convert to NO₃⁻, SO₄²⁻, CO₂, and H₂O.

3. Materials and Methods

3.1. Materials and Reagents

Sm₂O₃ (purity = 99.9%), Nd₂O₃ (purity = 99.9%), Sb₂O₅ (purity = 99.9%), Bi₂O₃ (purity = 99.9%), Dy₂O₃ (purity = 99.9%), Ethylenediaminetetracetic acid (EDTA, C₁₀H₁₆N₂O₈, purity = 99.5%), isopropyl alcohol (IPA, C₃H₈O, purity ≥ 99.7%), benzoquinone (BQ, C₆H₄O₂, purity ≥ 98.0%), the above chemical reagents were all purchased from Sinopharm Group Chemical Reagent Co., Ltd. (Shanghai, China). Absolute ethanol (C₂H₅OH, purity ≥ 99.5%) was purchased from Aladdin Group Chemical Reagent Co., Ltd. (Shanghai, China). Parathion methyl (C₈H₁₀NO₅PS, purity ≥ 98%) was gas chromatography grade and was purchased from Tianjin Bodi Chemical Co., Ltd., Tianjin, China, as the model material.

3.2. Preparation Method of Sm₂NdSbO₇

The novel photocatalyst Sm₂NdSbO₇ was produced using the solid-phase sintering process. Powders with a molar ratio of 2:1:1 of Sm₂O₃, Nd₂O₃, and Sb₂O₅ were dehydrated at 200 °C for 4 h prior to the synthesis process. The precursors of Sm₂NdSbO₇ were combined in the correct proportions, formed into tiny columns, and placed in an alumina crucible. The raw materials and the tiny columns were removed from the electric furnace after being calcined at 400 °C for 2 h. The blended materials were ground and then placed in an electric furnace. The calcination procedure was conducted at 1050 °C for 30 h in an electric furnace.

3.3. Preparation Method of BiDyO₃

BiDyO₃ was synthesized using a high-temperature solid-phase sintering technique. Because Bi₂O₃ performance is unstable at high temperatures, we decided to increase the amount of Bi₂O₃ by 120% after conducting 5 experiments. The materials with a molar ratio of 1.2:1 of Bi₂O₃ to Dy₂O₃ were well mixed and then milled in a ball mill until the particle size of the powder reached 1–2 µm. All powders were dehydrated at 200 °C for 4 h before synthesis. The powders were combined in an aluminum oxide crucible, formed into disks, and then sintered in an electric furnace at 750 °C for 10 h. The mixture was sintered in an electric furnace at 1050 °C for 12 h after being crushed and pressed. After complete grinding, a pure BiDyO₃ catalyst was finally achieved.

3.4. Synthesis of N-Doped TiO₂

The N-doped TiO₂ (N-T) catalyst was prepared using the sol-gel method, with tetrabutyl titanate as a precursor and ethanol as a solvent. The process unfolded in the following manner: Solution A was produced by mixing 17 mL of tetrabutyl titanate with 40 mL of pure ethyl alcohol. Solution B was produced by mixing 40 mL of pure ethyl alcohol, 10 mL of glacial acetic acid, and 5 mL of double-distilled water. Solution A was gradually introduced into solution B with vigorous stirring, leading to the creation of a transparent colloidal suspension. Subsequently, an aqua ammonia solution with a N/Ti ratio of 8 mol% was introduced into the transparent colloidal suspension and agitated using a magnetic stirrer for 1 h. The xerogel was created during a 2-day aging procedure. The xerogel was crushed into fine particles and thereafter subjected to a temperature of 500 °C for a duration of 2 h. The powder was treated in an agate mortar and sifted using a shaker to obtain N-T particles.

3.5. Synthesis of Sm₂NdSbO₇/BiDyO₃ Heterojunction Photocatalysts

(1)

Sm₂NdSbO₇ and BiDyO₃, respectively, were weighed and evenly mixed, then added to the ball mill to be ground into a powder;

(2)

The above powder was taken to dry, pressed into sheets, put it into a high-temperature sintering furnace for sintering, raising the temperature from room temperature to 400 °C at a heating rate of 10 °C/min, and then maintained at 400 °C for 4 h. Then, the temperature was raised from 400 °C to 800 °C at a heating rate of 9 °C/min, and then maintained at 800 °C for 12 h. The temperature was then raised from 800 °C to 1250 °C at a heating rate of 8 °C/min, then maintained at 1250 °C for 30 h. Finally, the first sintered tablet sample was cooled from 1250 °C to room temperature at a cooling rate of 8 °C/min.

(3)

The above first sintering tablet was taken, crushed, pressed into a sheet, and then placed in a high-temperature sintering furnace for sintering. The temperature was raised from room temperature to 500 °C at a heating rate of 10 °C/min, and then maintained at 500 °C for 5 h. Then, the temperature was raised from 500 °C to 900 °C at a heating rate of 9 °C/min, and maintained at 900 °C for 15 h. The temperature was raised from 900 °C to 1300 °C at a heating rate of 8 °C/min, and then maintained at 1300 °C for 25 h. Finally, the second sintered tablet sample was obtained by cooling from 1300 °C to room temperature at a cooling rate of 7.5 °C/min.

(4)

The above second sintering tablet was taken and crushed again, pressed into a sheet, and placed in a high-temperature sintering furnace for sintering. The temperature was raised from room temperature to 550 °C at a heating rate of 10 °C/min, and then maintained at 550 °C for 4 h. Then, the temperature was raised from 550 °C to 950 °C at a heating rate of 9 °C/min, and it was then maintained at 950 °C for 16 h. The temperature was raised from 950 °C to 1350 °C at a heating rate of 8 °C/min, and then maintained at 1350 °C for 35 h. Finally, the third sintered tablet sample was obtained by cooling from 1350 °C at a cooling rate of 7 °C/min.

(5)

The above third sintered tablet sample was then taken and crushed to obtain the Sm₂NdSbO₇/BiDyO₃ powder catalytic material.

3.6. Characterizations

The pristine crystals of the fabricated designs were examined using an XRD (XRD, Shimadzu, XRD-6000, Cu Kα radiation, Kyoto, Japan). The patterns, shape, and microstructure were analyzed using TEM models (JEM-F200, FEI Tecnai G2 F20, Waltham, MA, USA). The elemental composition was determined by EDS. The sample was analyzed for its diffuse reflectance spectrum using a UV–Vis DRS (Shimadzu, UV-3600, Kyoto, Japan). Analyzed the functional groups and chemical bonds using FTIR (WQF-530A, Beifen-Ruili Analytical Instrument Group Co., Ltd., Beijing, China). The chemical bond interactions were examined using a Raman spectrometer (INVIA0919-06, RENISHAW plx, Wotton-under-Edge, Gloucestershire, UK). Analyzed the surface chemical composition and states of the sample using an XPS (PHI 5000 VersaProbe, UlVAC-PHI, Maoqi City, Japan) equipped with an Al-kα X-ray source. The ionization potential of the valence band of the samples was measured using ultraviolet photoelectron spectroscopy (UPS) with an Escalab 250 xi instrument from Thermo Fisher Scientific in Waltham, MA, USA. The free radicals in the samples were identified using an electron paramagnetic resonance spectrometer (EPR, A300, Bruker Corporation, Karlsruhe, Germany).

The characteristics of PL and TRPL were analyzed using a fluorescence spectrophotometer (FLS980, Edinburgh Instruments Ltd., Edinburgh, UK).

Which were analyzed using double-exponential decay Equation (3) [95]:

$$\mathrm{I}\left(\mathrm{t}\right){=\mathrm{I}}_0+{\mathrm{A}}_1\mathrm{e}\mathrm{x}\mathrm{p}\left(-\frac{\mathrm{t}}{{\tau }_1}\right)+{\mathrm{A}}_2\mathrm{e}\mathrm{x}\mathrm{p}\left(-\frac{\mathrm{t}}{{\tau }_2}\right)$$

(3)

In the provided equation, τ₁ and τ₂ represent the first- and second-order decay times, respectively, and A₁ and A₂ are the weighting coefficients of each decay channel [96]. To determine the average photogenerated charge carrier lifetime (τ_ave), the following Equation (4) was utilized [97]:

$${\tau }_{\mathrm{a}\mathrm{v}\mathrm{e}}=\left({\mathrm{A}}_1{\tau }_1^2+{\mathrm{A}}_2{\tau }_2^2\right)/\left({\mathrm{A}}_1{\tau }_1+{\mathrm{A}}_2{\tau }_2\right)$$

(4)

3.7. Photoelectrochemical Experiments

Electrochemical impedance spectroscopy (EIS) and photocurrent (PC) measurements were performed using a CHI660D electrochemical station manufactured by Chenhua Instruments Co. in Shanghai, China, using a standard three-electrode configuration. The system comprised a working electrode, counter electrode, and reference electrode, which were catalysts: a platinum plate and a commercial Ag/AgCl electrode, respectively. A 0.5 mol·L⁻¹ aqueous solution of Na₂SO₄ was used as an electrolyte. Photochemical experiments were carried out utilizing a 500 W xenon lamp with a UV cut-off filter serving as the visible light emitter. The electrode was produced using the following method: A 0.03 g sample and 0.01 g of chitosan were dissolved in 0.45 mL of dimethylformamide to form a uniform suspension solution after one hour of ultrasonic treatment. The solution was applied to a 10 mm × 20 mm indium tin oxide (ITO) conducting glass. The working electrode was dried at 80 °C for 10 min.

3.8. Experimental Setup and Procedure

The research was carried out in a photocatalytic reactor (CEL-LB70, China Education Au-Light Technology Co., Ltd., Beijing, China) at a controlled temperature of 20 °C with circulating cooling water. A 500 W xenon lamp with a 420 nm cut-off filter was utilized to replicate sunlight irradiation. There were 12 identical quartz tubes, each with 40 mL of reaction solution, totaling 480 mL for pesticide wastewater (PW). The concentration of Sm₂NdSbO₇, BiDyO₃, or SBHP was 0.75 g·L⁻¹, and the concentration of methyl parathion (MP) was 0.025 mmol·L⁻¹. The concentration of MP refers to the residual quantity following biodegradation in real PW with a starting MP concentration of 1.0 mmol·L⁻¹. 3 mL of suspension was intermittently removed during the reaction. The catalyst was filtered out using a 0.22 μm PES polyether sulfone filter membrane. The concentration of MP left in the solution was analyzed using Agilent 200 high-performance liquid chromatography (Agilent Technologies, Palo Alto, CA, USA) with a UV detector and a Zorbax 300SB-C18 column (4.6 mm × 150 mm, 5 μm). A mobile phase composed of a 50% mixture of CH₃CN and distilled deionized water was used. The UV detection was calibrated specifically for a wavelength of 254 nm. 10 μL of the post-photodegradation MP solution was injected at a flow rate of 1 mL·min⁻¹. Prior to subjecting the solution to visible light, the combination of photocatalyst and MP was stirred in darkness for 45 min to achieve an adsorption/desorption equilibrium between the components and ambient oxygen.

During exposure to visible light, the suspension is agitated at a speed of 500 rpm. Before the photocatalytic experiment, we first carried out the adsorption equilibrium experiment under the condition of avoiding light. The sample was added to the solution, and the magnetic stirrer was activated for stirring until the dye contaminants in the solution reached the adsorption equilibrium state on the surface of the sample. The experimental process took 40 min. The adsorption equilibrium experiment is mainly to exclude the effect of adsorption on the concentration of pollutants or degraded substances.

The mineralization experimental data of MP in the reaction solution were evaluated with a TOC analyzer (TOC-5000 A, Shimadzu Corporation, Kyoto, Japan). TOC concentration was measured during the PHDE of MP using potassium acid phthalate (KHC₈H₄O₄) or anhydrous sodium carbonate as a reference reagent. Calibration solutions containing potassium acid phthalate with a known carbon concentration varying from 0 to 100 mg·L⁻¹ were prepared. TOC concentration was measured by analyzing six samples, each consisting of 45 mL of reaction solution.

MP and its intermediate degradation products were identified and measured using liquid chromatography–mass spectrometry (LC-MS) with a Thermo Quest LCQ Duo instrument. A total of 20 microliters of the solution resulting from the photocatalytic process were automatically fed into the LC-MS apparatus. The mobile phase consisted of 60% methanol and 40% ultrapure water, with a flow rate of 0.2 mL·min⁻¹. The mass spectrometry setup involved an electrospray ionization interface, a capillary temperature of 27 °C with a voltage of 19.00 V, a spray voltage of 5000 V, and a consistent sheath gas flow rate. The spectra were obtained using negative ion scan mode with a mass-to-charge ratio (m/z) range of 50 to 600.

The radiometer (Model FZ-A, Photoelectric Instrument Factory, Beijing Normal University, Beijing, China) detected an incoming photon flux Io of 4.76 × 10⁻⁶ Einstein·L⁻¹·s⁻¹ within the wavelength range of 400–700 nm. The incident photon flux on the photoreactor was altered by changing the distance between the photoreactor and the Xe arc lamp.

The photonic efficiency was calculated in accordance with the following Equation (5):

ϕ = R/I_o

(5)

where ϕ was the photonic efficiency (%), R was the degradation rate of MP (mol·L⁻¹·s⁻¹), and I_o was the incident photon flux (Einstein·L⁻¹·s⁻¹).

4. Conclusions

Sm₂NdSbO₇ was synthesized for the first time using high-temperature solid-state sintering, resulting in significant photocatalytic activity. Sm₂NdSbO₇/BiDyO₃ heterojunction photocatalyst (SBHP) was produced for the first time using a straightforward solid-phase sintering method. Photophysical properties and photocatalytic performance were analyzed using various techniques, including X-ray diffractometer (XRD), transmission electron microscope (TEM), X-ray photoelectron spectrograph (XPS), Fourier transform infrared dpectrometer (FTIR), Raman spectrometer, fluorescence spectrophotometer, ultraviolet photoelectron spectroscopy (UPS), photocurrent (PC) test, photoluminescence (PL) spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, and UV–Vis diffuse reflectance spectrophotometer (UV–Vis DRS). The results indicate that Sm₂NdSbO₇ is a single-phase material with a pyrochlore structure. It exhibits a cubic crystal system inside the Fd3m space group. Sm₂NdSbO₇ has lattice parameters of a = 10.98142 Å and a band gap of 2.750 eV. SBHP was demonstrated to be a successful photocatalyst for eliminating methyl parathion (MP) from wastewater. After 145 min of visible light exposure (145-VLIRD), the removal rates of MP and TOC were 100% and 97.58%, respectively. The relative metabolic rate of methyl palmitate by solid-phase high-pressure (SBHP) treatment was 1.13, 1.20, or 2.43 times more than that of Sm₂NdSbO₇, or BiDyO₃ as a catalyst, or N-doped TiO₂ as a catalyst, respectively, and it increased after 145-VLIRD. Thus, it may be inferred that SBHP could be a successful approach for treating wastewater contaminated with MP. The potential photodegradation mechanism of MP was hypothesized.