Introduction

Currently, environmental pollution has profound negative effects on people’s lives. As organic contaminants degrade, they possess an adverse effect on human wellness, which has become a focus of scientific research today (Sugashini et al. 2022). As a result of their slow biodegradability and ineffective and environmentally damaging conventional treatment methods, pollutants released from a variety of sources pose a serious threat to the environment (Chatterjee and Dasgupta 2005). Compared to traditional chemical oxidation processes, photocatalysis, particularly semiconductor photocatalysis, seems to be the most attractive method for degrading organic compounds into harmless substances (Abdullah et al. 2022; Wei et al. 2024). This is because semiconductors are safe, low cost, have wide spectrum of absorption with significant absorption values, have large surfaces, and have adjustable features, which can be altered by sensitizers, doping, and dimension decrease. A multielectron transfer operation is available, and the photocatalytic performance can be maintained for an extended period without deterioration (Rahman et al. 2022). Furthermore, semiconductor particles regained by centrifugation, filtration, or immobilization in a fluidized bed reactor maintain a significant amount of their original activity even after numerous catalytic cycles. A number of papers have been published in the literature describing the general properties of polymeric composite suspensions in terms of adsorption, biosorption, adsorptive removal, separation and determination (Fan et al. 2016; Hernández-Moreno et al. 2021; Taifi et al. 2022; Mahdi et al. 2021; Aljeboree et al. 2021; Ganduh et al. 2021).

The use of materials with small particle sizes and large surface areas is essential for various technical applications (Parsayi et al. 2023). Recently, nanomaterials have gained much concentration for their versatile functions and fascinating attributes (Liu et al. 2012; Yan 2020). Combinations of M2SiO4 (M = transition metals) crystallize in olivine crystals and exhibit distorted hexagonal close-packed (hcp) oxygen anions where silicon occupies one-eighth of the tetrahedral interstitial zones. Divalent metal cations M colonize one-half of the octahedral interstitial zones (Cheng et al. 2019; Sazonov et al. 2009). There is no doubt that the olivines are significant geophysical and geological elements within the Earth’s upper mantle (Dong et al. 2021). In the ceramic industry, Co2SiO4 (CSO) is commonly utilized as a pigment due to its high thermal stability, and is presently being evaluated as a catalyst and magnetic material (Yatabe et al. 1997). There are multiple ways to synthesize Co2SiO4 nanostructures, such as sol–gel (Stoia et al. 2010), hydrothermal (Taguchi et al. 2002), precipitation (Yatabe et al. 1997). In this work, Co2SiO4 nanostructures are fabricated by sonochemical method.

In recent years, carbon nitride (CN) has emerged as an intriguing photocatalyst material, although it is by no means a new material. Among the earliest synthetic polymers, “melon” is the name given to a polymeric derivative created by Berzelius and called by Liebig in the year 1834 (Wang et al. 2012). The major components of this polymeric semiconductor are nitrogen and carbon, which organic chemistry offers methods and reactions to alter its reactivity without significantly altering its composition. Several studies have been conducted on methods for synthesizing various modifications and clarifying the structure and composition of CN materials in the literature (Bai et al. 2010; Banerjee et al. 2010; Xia et al. 2010). Its possible uses for hydrogen storage, energy conversion (Habibi-Yangjeh and Basharnavaz 2021, Mahdizadeh and Goharshadi 2019), water purification (Cui et al. 2021), carbon dioxide storage, gas and humidity sensors (Meng et al. 2020; Yu et al. 2020), solar cell manufacturing (Safaei et al. 2018; Xu et al. 2014), among other things, have all been documented. Recent research has concentrated on graphitic carbon nitride, or g- C3N4, the most stable allotrope of CN (Yousefzadeh et al. 2022)gh. Tri-s-triazines connected by tertiary amines provide the basis of g-C3N4’s 2D sheets (Chen et al. 2022; Zheng et al. 2012). Nevertheless, the application of g-C3N4 in heterogeneous catalysis dates back to 2006. Wang et al. reported the use of g-C3N4 for photocatalytic water splitting under visible-light for the first time (Wang et al. 2009).

The aim of this work is to present a novel nanocomposite for the photodegradation of Eriochrome Black-T (EB) under UV light that contains g-C3N4 and varying amounts of Co2SiO4. An ultrasonic-assisted co-precipitation approach was used to add CSO to g-C3N4 by the sonochemical method. As far as we know, that CSO/CN nanocomposites have never before been synthesized and utilized as photocatalysts for degrading organic dyes.

Materials and methods

Materials

The chemical substances utilized were of the greatest grade. Tetraethyl orthosilicate > 99% (TEOS), Cobalt acetate tetrahydrate 99% (Co(CH3CO2)2.4H2O), Eriochrome Black-T (EB), Tetraethylenepentamine > 95% (TEPA), Benzoic acid (BA), 1, 4-Benzoquinone (BQ), Melamine 99.9% (C3H6N6), and Ethylenediaminetetraacetic acid (EDTA), were sourced from Sigma-Aldrich and implemented with no extra processing.

Synthesis of Co2SiO4 by sonochemical method

The first step was to dissolve 1.18 g of Co(CH3CO2)2 in 40 mL of water and stir for 15 min. Next, 531 µL TEOS were mixed with 10 mL of ethanol. Afterward, the second solution was poured to the cobalt acetate solution and mixed for 30 min. In the following steps, the solution was subjected to ultrasonic waves for 10 min, TEPA was added during the ultrasonic operation until the pH of the solution exceeded 10. After centrifugation, the obtaining powder was oven-dried for 24 h and calcined at 900 °C for five hours.

Synthesis of Co2SiO4/g-C3N4 nanocomposites

As previously described in our works (Hosseini et al. 2024c), graphitic carbon nitride nanosheets were first prepared. A standard process involved direct heating 10.0 g melamine at 550 °C for four hours. After being acquired, the yellow powder of CN was utilized in other experiments. Following that, 2.0 g of g-C3N4 was ultrasonically dispersed in 30 mL of water for 10 min. Then, four different amounts of Co2SiO4, including 0.2, 0.6, 1.0, and 1.4 g were separately added to the mixture containing g-C3N4 and mixed for one day. After 24 h, the powder was centrifuged and dried for 24 h at 65 ℃.

Characterization methods

X-ray diffraction (XRD) patterns were obtained by a Philips diffractometer with X’PertPro monochromatized Cu K radiation (λ = 1.54) to evaluate the structure and purity of the products. The sample’s Fourier Transform Infrared (FTIR) spectra were recorded by Shimadzu FTIR-8300 E spectrophotometer in the range of 400–4000 cm–1. Field emission scanning electron microscopy (FESEM) MIRA 3 TESCAN equipped with EDS (energy-dispersive spectrometry) was used to study the nanoparticles’ shape and distribution. Transmission electron microscopy (TEM) (JEM-2100) was used to study the structure of products. A Jasco V-670 spectrophotometer recorded the UV–visible spectrum, and the bandgap was measured by Diffuse Reflectance Spectrophotometer (DRS) (Model: HO-SP-DRS100). A surface area and porosimetry analyzer (Tristar 3000, Micromeritics) was used to define the surface areas (Brunauer–Emmett–Teller, BET) through N2 adsorption at − 196 ℃ using. An MPI Ultrasonic; welding, 1000 W, 20 kHz, Switzerland (multi-wave ultrasound generator) was provided by a transducer/converter.

Photocatalytic process

As a photocatalyst, pure Co2SiO4 and its different contents, in conjunction with g-C3N4, were utilized in the photocatalytic operation since these compounds have a good potential for destroying toxic coloring agents, including Eriochrome Black T (EB) below UV radiation. For the photocatalytic operation, a 400 W Osram light was used as the irradiation origin. Approximately 315 to 400 nm of UVA and 280 to 315 nm of UVB are emitted by this lamp. After 120 min, almost no EB had been destroyed without a catalyst and light. 50 mL of 10 ppm EB solutions were mixed with 0.05 g of various samples (e.g., CSO and CSO/CN with various concentrations of CSO). It is important to note that the catalyst and EB were mixed in the dark for 30 min prior to exposure. Every 15 min, a 3 mL sample of the suspension is taken and centrifuged at 13,000 rpm for 3 min to remove particles. In order to estimate the float’s absorption, a UV–VIS spectrophotometer was used. The degradation percentage (%D) is determined by the following these steps:

$$ D(\% ) = \frac{{A_{0} - A_{t} }}{{A_{0} }} \times 100 $$
(1)

In this equation, A0 and At indicate the absorption of dye solution at 0 and t minute, respectively (Saadati-Gullojeh et al. 2024).

Results and discussion

Product characterization

As depicted in Fig. 1a, the XRD pattern of pure Co2SiO4 displays an orthorhombic crystal structure with 01-084-1298 cobalt silicate. Figure 1b–e indicates the XRD patterns of CSO/CN with various levels of CSO. The patterns include Co2SiO4 (01-084-1298) and carbon nitride (01-87-1526). It was determined that CN has two distinct peaks at 13.1° and 27°, referred to as (001) and (002). The number and intensity of Co2SiO4 peaks in the composition increase as the content of Co2SiO4 increases. The crystallite size was determined utilizing Scherrer formula (Tahir et al. 2020) to be between 25 and 27 nm.

$$ D = \frac{K\lambda }{{\beta \cos \theta }} $$
(2)
Fig. 1
figure 1

The XRD patterns of a pure CSO, b CSO/CN (0.1:1), c CSO/CN(0.3:1), d CSO/CN (0.5:1), and e CSO/CN (0.7:1)

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Co2SiO4 nanostructures were synthesized using ultrasound technology. Ultrasonic wave cavitation is utilized to create acceptable nanostructures. The hot-spot theory states that tremendous powers are employed to produce very high pressures and temperatures, which create radicals that are active during the process (Hosseini et al. 2024a). The reactions listed below show that the sonochemical method was used to create the product:

$$ {\text{H}}_{2} {\text{O}} \to \bullet {\text{OH}} + \bullet {\text{H}} $$
(3)
$$ \bullet {\text{OH}} + \bullet {\text{OH}} \to {\text{H}}_{2} {\text{O}}_{2} $$
(4)
$$ \bullet {\text{H}} + \bullet {\text{H}} \to {\text{H}}_{2} $$
(5)
$$ {\text{O}}_{2} + \bullet {\text{H}} \to \bullet {\text{O}}_{2} {\text{H}} $$
(6)
$$ \bullet {\text{O}}_{2} {\text{H}} + \bullet {\text{H}} \to {\text{H}}_{2} {\text{O}}_{2} $$
(7)
$$ 2 \bullet {\text{O}}_{2} {\text{H}} \to {\text{H}}_{2} {\text{O}}_{2} + {\text{O}}_{2} $$
(8)
$$ {\text{Si}}\left( {{\text{OEt}}} \right)_{4} + {\text{H}}_{2} {\text{O}}_{2} \textregistered 4{\text{C}}_{2} {\text{H}}_{5} {\text{OH}} + {\text{Si}}\left( {{\text{OH}}} \right)_{4} $$
(9)
$$ {\text{Si}}\left( {{\text{OH}}} \right)_{4} + {\text{Co}}\left( {{\text{CH}}_{3} {\text{CO}}_{2} } \right)_{2} + {\text{TEPA}} \to {\text{Co}}^{2 + } + \left( {{\text{SiO}}_{4} } \right)^{4 - } + {\text{HCH}}_{3} {\text{CO}}_{2} $$
(10)
$$ \left( {{\text{SiO}}_{4} } \right)^{4 - } + {\text{Co}}^{2 + } + {\text{TEPA}} \to {\text{Co}}_{2} {\text{SiO}}_{4} $$
(11)

Figure 2 shows the FTIR spectra of CSO, CN, and CSO/CN. The bending vibration of O‒Si‒O is attributed to the band around 475 cm‒1, and the band at 1080 cm‒1 is associated with the Si‒O‒Si bond’s vibration (Saravanapavan and Hench 2003). The Co‒O (metal–oxygen) stretching mode is assigned to the bands at 578 cm‒1 (Pejova et al. 2001). The peak at approximately 870 cm‒1 is associated with the SiO4 tetrahedron vibrations (Lin 2001). The broad peak at 3432 cm‒1 and the peak near 1637 cm‒1 are attributed to stretching and bending vibrations of moisture absorbed on the surface of nanostructures, respectively. As can be seen in Fig. 2a, there are no further impurity bands. The FTIR spectrum of pure carbon nitride can be seen in Fig. 2b. A relationship exists between the vibrations of s‒triazine and the absorption band at 804 cm‒1 (Yousefzadeh et al. 2022). In heterocyclic compounds, the bands between 1640 and 1230 cm‒1 are in accordance with the C‒N and C=N vibration bands. The stretching band of N‒H of g-C3N4 is placed at 3165 cm‒1 (Saadati-Gullojeh et al. 2024). The peaks at 1230 and 1328 cm‒1 are attributed to bending vibrations of s‒triazine (Choi et al. 2015). The FTIR spectrum of CSO/CN is comparable to that of pure CN and can show all of the distinct bands of g-C3N4. As a result, the CN standard peaks did not change after combining CSO nanoparticles (Wang et al. 2009).

Fig. 2
figure 2

FTIR spectra of a CSO, b CN, and c CSO/CN (0.1:1)

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EDS is a method that scientists use to characterize products chemically and in terms of their elemental composition. The EDS spectra of CSO and CSO/CN are shown in Fig. 3, with all peaks related to the elements Co, O, Si, N, and C. The EDS data confirmed the homogenous element dispersion in the specimens.

Fig. 3
figure 3

EDS spectra of a CSO, b CSO/CN (0.1:1), c CSO/CN (0.3:1), and d CSO/CN (0.5:1)

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The morphology of products was studied by SEM microscopy. Figures 4a and b depict the surface morphology of CSO in two different magnifications. The polyhedral morphology is obvious in these figures. The addition of carbon nitride changes the morphology. Figures 4c and d shows the morphology of CSO/CN (0.1:1) forming from nanoflake of CN and some CSO nanoparticles. Since the amount of CSO is low, the particles are not observable. String-like particles of CSO were composed on the surface of carbon nitride when the weight ratio of CSO to CN was 0.3 to 1 (Figs. 4e and f). Increasing the content of CSO in the composite structure results is agglomeration of CSO. As observed in Figs. 5a and b, CSO was aggregated on the CN surface in the weight ratio of 0.5 to 1. A further increase in the CSO content (0.7) covers the carbon nitride surface (Figs. 5c and d). Figure 6 illustrates the TEM photographs of Co2SiO4/g-C3N4 (0.1:1) at three different scales (100, 60, and 20 nm). As indicated, CSO nanoparticles are composed on the surface of carbon nitride, and the nanoflake morphology of CN is visible in these figures. The HRTEM photograph of Co2SiO4/g-C3N4 (0.1:1) is shown in Fig. 6d. The parallel lines separating the crystal surfaces demonstrated the high crystallinity of CSO. It is well suited to the orthorhombic CSO crystal planes (112), which have an interplanar spacing of 2.5 Å.

Fig. 4
figure 4

FESEM images of a and b CSO, c and d CSO/CN (0.1:1), e and f CSO/CN(0.3:1)

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Fig. 5
figure 5

FESEM images of a and b CSO/CN (0.5:1), c and d CSO/CN (0.7:1)

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Fig. 6
figure 6

TEM and HRTEM images of CSO/CN (0.1:1)

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N2 adsorption and desorption were analyzed by the BET method at 77 k (Fig. 7). The isotherm of the CSO is ordered as an I-type isotherm based on IUPAC (Fig. 7a). The specific surface area of CSO is evaluated at 48.007 m2/g. The CSO nanostructures that are distinguished from the BJH plot (Fig. 7b) have total pore volumes and mean diameters of pores of 0.038156 cm3/g and 3.1792 nm, respectively. The isotherm of CSO/CN belongs to the IV-type isotherm with H3 hysteresis (Fig. 7c). The mean pore diameters, total pore volumes, and specific surface area, are 10.60474 nm, 0.099623 cm3/g, and 37.5770 m2/g, respectively (Fig. 7d).

Fig. 7
figure 7

N2 adsorption/desorption isoterms and BJH plots of a and b pure CSO, c and d CSO/CN (0.1:1)

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The optical properties of CSO and CSO/CN were analyzed employing DRS spectroscopy. Applying the Tauc method and the below formula, the photon absorption and energy were used to calculate the bandgap energy:

$$ A\left( {h\upsilon - B.G.} \right) = \left( {\alpha h\upsilon } \right)^{n} $$
(12)

υ is frequency, h presents Planck constant, α is absorbance, A is material constant, and B.G. indicates optical bandgap. Figure 8a depicts the spectrum of CSO. (αhυ)2 vs. hυ is linearly extrapolated to zero to determine the band gap at 3.5 eV (Fig. 8b). The absorption of CSO/CN nanocomposites is depicted in Fig. 8c. As can be seen, the bandgap of CSO was reduced to 3.0 eV by introducing CN to the structure. In addition, the bandgap of CN is calculated at 2.7 eV (Fig. 8d).

Fig. 8
figure 8

DRS spectra and Tauc plots of a and b pure CSO, c and d CSO/CN (0.1:1), e PL spectra of pure CSO, CN, and CSO/CN (0.1:1)

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The PL spectra of CSO, CSO/CN (0.1:1), and pure CN at 245 nm are shown in Fig. 8e. Photogenerated charge carrier recombination was identified as the cause of a strong emission peak observed in the pure CN at 509 nm (Pawar et al. 2017). In comparison to pure CN and CSO, the intensity of the photogenerated charge carrier recombination peak for CSO/CN (0.1:1) under UV irradiation was significantly lower, indicating a lower rate of recombination. The PL study found that the nanocomposite had lower recombination losses than the bare CN and CSO.

Photocatalytic applications

By monitoring the decolorization of EB under UV light, we were able to evaluate the photocatalytic efficacy of Co2SiO4, g-C3N4, and Co2SiO4/g-C3N4 nanocomposites. It was necessary to examine the effects of a number of factors on CSO/CN nanocomposites’ photocatalytic activity, including the mass ratio variety, catalyst doses, and dye concentration. As shown in Fig. 9a, the mass ratio of CSO to CN influences the photocatalytic performance. Based on our observations, pure CN has a photocatalytic efficiency of 57.7% and pure CSO has a photocatalytic efficiency of 63.6%. The addition of 0.1% CSO to pure CN enhances the degradation of EB by 83.3% (Table 1). Due to the increased bandgap, the results indicate that increasing the CSO content reduces the degradation of EB. In spite of this, the photocatalytic percentage of the composite is 71.1% after the addition of 0.7% of CSO, which is higher than the percentage of pure CN and CSO. Combining CSO with CN increases the photocatalytic activity and degrades more EB. The addition of a low content of CSO can potentially increase the photocatalytic activity of CN through several mechanisms: (i) CSO can play as a catalyst that facilitates the photogenerated electron–hole pair’s separation in CN. This separation prevents recombination of the charges, thereby increasing the performance of the photocatalytic process. (ii) The presence of CSO can promote efficient charge transfer between CN and the reactants or intermediates involved in the photocatalytic process. This facilitates faster reaction kinetics and improves overall catalytic performance. (iii) CSO nanoparticles can enhance the stability and durability of the composite material, preventing degradation or deactivation of the photocatalyst over prolonged use. This ensures sustained photocatalytic activity over time.

Fig. 9
figure 9

Photocatalytic performance and ln(C0/C) plots of a and b different samples of CSO, CN and their nanocomposites, c and d effect of different dosages of CSO/CN (0.1:1) over 10 ppm EB, e and f effect of different EB concentrations in the presence of 70 mg CSO/CN (0.1:1)

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Table 1 Photocatalytic degradation of different CSO/CN nanocomposites
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Catalyst content is an important parameter for increasing photocatalytic efficiency. As can be seen in Fig. 9c, various quantity of CSO/CN (0.1:1) nanocomposites have a differential effect on EB. When the amount of catalyst is increased, the photocatalytic performance increases as expected. When 30, 50, and 70 mg of Co2SiO4/g-C3N4 (0.1:1) are added to EB, the degradation percentage is 69.3, 83.3, and 90.0%. This can be explained by raising the amount of catalyst to enhance the catalyst surface area and thereby increasing EB absorption on the CSO/CN surface (Ebrahimipour et al. 2024). Figure 9e indicates the impact of three various EB concentrations (10, 15, and 20 ppm) over CSO/CN (0.1:1). The result shows that increasing EB concentrations reduces the photodegradation, so that, 90.0% of 10 ppm EB, 80.0% of 15 ppm EB, and 72.3% 20 ppm EB are degraded after 120 min under UV light. A considerable number of EB molecules infiltrate the binding zones on the catalyst surface at high concentrations.

In addition, rate coefficients were calculated using the Langmuir–Hinshelwood reaction (Hosseini et al. 2024a):

$$ \ln \left( {\frac{{C_{0} }}{C}} \right) = kt $$
(13)

where the dye concentrations at times t0 and t, respectively, are indicated by C0 and C. ln(C0/C) linear correlations vs. time are used to calculate the pseudo-rate constant (k). Figure 9b, d, and f shows how the highest photocatalytic activity was attained using a larger rate coefficient. Figure 10 shows the influence of multiple aspects on photodegradation activity, showing that the greatest efficiency was achieved at a higher rate constant.

Fig. 10
figure 10

a and b effect of different scavengers on the photocatalytic performance and its ln(C0/C) plot, c different types of dyes over CSO/CN (0.1:1), and d recycle test in the presence of CSO/CN (0.1:1)

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The scavenger tests were carried out operating BA, BQ, and EDTA to hunt •OH, •O2−, and h+, respectively, to illustrate the performance of functional species in the destruction of EB. As shown in Fig. 10a, adding BQ to the mixture reduced the photocatalytic performance from 90.0 to 33.9%, depicting that •O2− constitutes the most common functional species in photocatalysis. However, by adding EDTA and BA separately to the suspension, the photocatalytic efficacy declined from 90.0 to 81.8 and 72.5%, respectively, displaying that the effect of h+ and •OH on the breakdown of EB was not visible (Sakthivel et al. 2003). Decolorization of EB results from the creation of active •O2− when oxygen molecules are present during the electron (e−) interaction (Wenderich and Mul 2016).

Moreover, the following two equations can be used to calculate the conduction band (ECB) and valence band (EVB) potentials of CN and CSO:

$$ E_{{{\text{VB}}}} = X - E{}_{e} + 0.5E_{g} $$
(134)
$$ E_{{{\text{CB}}}} = E_{{{\text{VB}}}} - E_{g} $$
(15)

X is the semiconductor’s electronegativity and has values of 4.73 and 5.717 eV for CN and CSO, respectively. On the hydrogen scale, Ee is the energy of free electrons and has a constant value of 4.5 eV (Lin et al. 2016). Consequently, it is possible to ascertain that the EVB values of CN and CSO are 1.58 and 2.967 eV, respectively, and that their matching ECB values are − 1.12 and − 0.533 eV. The findings suggest that more exposed active sites, quicker photogenerated carrier transit, and less recombination are responsible for the enhanced photocatalytic efficiency over CSO/CN heterojunctions.

Hence, Scheme 1 graphically illustrates a likely Z-scheme photocatalytic process. Based on the findings, a theoretical investigation of the mechanism of EB photodecomposition over CSO/CN was conducted. Below UV radiation, photogenerated e− and h+ are formed for the CN due to its significantly lower bandgap (2.7 eV). However, under comparable conditions, it proved challenging to excite photoinduced carriers due to the wide bandgap of CSO (3.5 eV).

Scheme 1
scheme 1

Schematic diagram of photocatalytic mechanism over EB

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By releasing the photo-excited h+ on the VB of CN, the photo-excited e− from the CB of CN (− 1.12 eV vs. NHE) can migrate to the CB of CSO (− 0.533 eV vs. NHE) based on the matchable CB levels. This enables the separation of the photoinduced e−-h+ pairs. Photoinduced electrons on the CB of CSO can capture O2 to form •O2−, which instantly destroys EB. This is demonstrated by the CB of CSO being less positive (− 0.046 eV vs. NHE) than O2/•O2−. The h+ in the VB of CN quickly oxidized the EB by photocatalysis because its VB (1.58 eV vs. NHE) was lower than that of OH−/•OH (2.70 eV vs. NHE) (Hosseini et al. 2024b). While n-type semiconductors have Fermi levels similar to CB (Xu and Schoonen 2000), CN has a higher Fermi level than CSO. In particular, photoinduced e−/h+ pairs are generated on the CSO and CN upon exposure to UV radiation, and because of the strong electrostatic pull, the electrons on the CSO could readily migrate for recombining and replace with h+ at the interface of CN’s VB. Conversely, the significant electrons on the CB of CN and the holes on VB of CSO are kept. Eventually, the photocatalytic activity is enhanced by the favorable spatial separation among h+ on the VB of CSO and e− on the CB of CN. •O2− can be created when electrons on the CN’s CB interact with adsorbed O2 on the surface of semiconductor. The reactions that were carried out on the surface of catalyst and directed to the destruction of EB are defined below (Konstantinou and Albanis 2004):

$$ {\text{CSO}}/{\text{CN}} + h\nu \to {\text{CSO}}/{\text{CN }}\left( {e_{{{\text{CB}}}}^{ - } + \, h_{{{\text{VB}}}}^{ + } } \right) $$
(16)
$$ {\text{CN}}(e^{ - } + \, h^{ + } ) \to {\text{CSO}}(e^{ - } ) + {\text{CN}}\left( {h^{ + } } \right) $$
(17)
$$ O_{2} + e^{ - } \to O_{2} \bullet^{ - } $$
(18)
$$ \bullet {\text{O}}_{2}^{ - } + {\text{EB}} \to {\text{CO}}_{2} + {\text{H}}_{2} {\text{O}} $$
(19)

A variety of dyes, for instance, EB, methylene blue (MB), and Acridine orange (AO), were investigated over CSO/CN (0.1:1) (Fig. 10c). According to the results, 90.0, 69.2, and 47.2% of EB, MB, and AO were degraded over CSO/CN (0.1:1). According to this result, CSO/CN (0.1:1) degrades anionic dyes (EB) more efficiently than cationic dyes (MB or AO) (Table 2). The recycling ability assay was performed to investigate the stability of CSO/CN. In a standard process, CSO/CN was cleaned, oven-dried at 70 °C overnight, and reutilized five times under the same states. Over five cycles, CSO/CN (0.1:1) remains stable and performs at its potential, as shown in Fig. 10d. The degradation percentage has declined by 11.1% during five cycles. To facilitate comparison, Table 3 lists the photocatalytic efficiency of several silicate compositions. Clearly, CSO/CN nanocomposites are capable of removing toxic dyes (EB) and can contend with other materials in this regard.

Table 2 Photocatalytic degradation of CSO/CN (0.1:1) nanocomposites in different conditions
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Table 3 The photocatalytic performance of different ortho silicate compounds
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Conclusions

The ultrasonic-assisted co-precipitation approach produced CSO/CN nanocomposites with varying weight ratios. The photodegradation of EB was studied for the first time using a variety of catalysts, including CSO, CN, and CSO/CN. Under ideal conditions, 90.0% of 10 ppm EB was degraded by 70 mg of CSO/CN (0.1:1). According to the results, this nanocomposite has great potential as a water treatment material. The scavenger experiment demonstrated that •O2− was the most prevalent active element in photodegradation mechanism. CN and CSO were found to be stable in the recycling test, with only 11.1% of their efficiency declining. This work establishes a new route toward the fabrication of next-generation photocatalytic materials for environmental remediation, especially in dye-polluted waters. Such promising performance and stability highlight these materials’ strong potential in dealing with issues related to dye pollution, thus helping to enhance water quality and environmental sustainability through advanced custom materials designed for this application.