The clay material used in this work was collected from the Hambol region (Katiola, North of Côte d’Ivoire). All major reagents utilized for synthesis were AR grade and were used as-received. Titanium sulfate provided by Bodi Chemical co. and silver nitrate supplied by Sigma-Aldrich were used as titanium and silver sources respectively. Orange II purchased from Eyer was used to assess the degradation performance of the samples. Double distilled water was used throughout the experiment. S. aureus (ATCC 6538) and E. coli (ATCC) were obtained from local suppliers.

The nanocomposites were prepared through a simple hydrothermal method using titanium sulfate and silver nitrate as precursor materials for Ti and Ag respectively, and clay. Before using, the clay was crushed, washed and activated in line with the procedure described by Guillaume et al. [20]. 5 g of titanium sulfate and 0.11 g of silver nitrate were dissolved in 150 mL of ultra-pure water. The mixture was kept in a dark room at ambient temperature under constant stirring to enable the complete dissolution of reactants. Various amounts of clay (i.e. 0.05, 0.25, 0.5, 2.5, and 5 g) were then added to the reaction mixture still under strong stirring for 2 hours. Afterwards, the ensemble was placed in an oven at 150˚C for 24 hours to undergo the hydrothermal treatment. The obtained products were ground and calcined in a furnace at 450˚C for 2 hours.

The structural properties of the specimens were determined by means of X-ray diffractometer (XRD, Rigaku D/MAX 2550, Cu Kα radiation, λ = 1.5406 Å) set at 40 kV and 100 - 200 mA in the range of 20˚ - 80˚ (2θ). The sample morphologies were characterized using Scanning electron microscope (SEM, Tescan VEGA3). FTIR spectra were recorded in the 400 - 4000 cm⁻¹ range with NICOLET 380 FTIR spectrometer. Experiments were performed on prepared KBr/sample pellets.

The photocatalytic activity efficiencies of the prepared samples were evaluated by degradation of 25 mg/L solution of Orange II. The photocatalytic activity tests were carried out under ambient temperature in a homemade photocatalytic reactor consisting of 500 W tungsten halogen lamp, put in a double wall jacketed quartz cylinder. Cold water was circulated through the walls for lowering the lamp temperature. A glass filter was inserted between the lamp and the sample to filter out UV light (k < 420 nm). Also, two fans were attached to the reactor; one was directly linked to the lamp while the other was used to cool the catalyst pollutant suspensions. The distance maintained between the lamp and the center of the quartz tube was 10 cm. Degradation studies were performed with 25 mg/L Orange II dye for a period time of 3 hours. 0.1 g of the catalyst was added to 50 mL of dye solution. Before irradiation of light, the samples were kept in dark under stirring to help the adsorption of samples on the surface of dye molecules. Sampling was performed hourly and centrifuged. Then degradation was evaluated by means of UV visible spectrometer (Shimadzu UV-2450). The adsorption/photodegradation efficiency of dyes was calculated using the following relation (1):

η = C 0 − C t C 0 × 100 (1)

where C₀ represents the initial concentration of the pollutants and C_t the concentration of the pollutants at time t.

For antibacterial experiment, E. coli (gram negative) and S. aureus (gram positive) bacteria were used as the target organisms. Luria Bertani (LB) broth and Muller Hinton (MH) agar were used for the growth of selected bacterium. Prior to the experimentation, each material and equipment was submitted to an autoclave sterilization. In the liquid culture the bacterial density was measured by its Optical density by means of UV-Vis Spectrophotometer at the wavelength of 600 nm and OD values were taken equal to 0.2. A 200 - 300 µL aliquot of the liquid culture was used for bacterial growth on agar plates, containing 105 colony-forming units (CFU). The antibacterial activity of the samples was observed using disk diffusion assay.

The aliquot containing bacteria were streaked evenly on the MH agar plates using sterilized cotton swabs. After drying the plates for 5 - 10 minutes, 10 mm diameter of sterilized samples were placed on the plate along with the positive control i.e. Amikacin disks for S. aureus and sulphamethaxazole for E. coli. After 24 hours of incubation at 37˚C in the incubator, the inhibition zones were measured.

SEM images of the clay, titanium oxide, silver doped TiO₂ and silver doped TiO₂ with clay composites are shown in Figure 1. SEM image of TiO₂ shows surface compactness and some clustered nanoparticles and no cracks was found during

annealing process at 450˚C. The incorporation of Ag in TiO₂ nanoparticles induces a change in the structure with respect to the one of the non-doped TiO₂. Ag nanoparticles form micron-sized aggregates on the surface of TiO₂ with a non-uniform distribution. The particles present in the silver doped TiO₂ appear smaller than those of the non-doped TiO₂. A more compact material with a cementation like phenomenon is observed suggesting an increase in the reactivity of the material. Also, one can observe the presence of cracks on the surface of Ag-doped TiO₂ specimen. Besides, adding clay in the Ag-doped TiO₂ system further improves the microstructure of the material with high roughness. However, cracks are still present on the surface of the material. The small size of particles and the fissures along with clay sheets could improve effectively the pollutant absorption and photocatalytic applications [19].

Figure 2 shows the FTIR spectra of the prepared Ag doped TiO₂ mixed with various amount of clay. Peaks around 3500 cm⁻¹ and 2400 cm⁻¹ are related to the stretching vibration of OH groups (Ti-OH) in the TiO₂ samples [20] [21]. Increasing the clay content in the system enables an increase in OH groups. This is quite beneficial for the photocatalysis, as it attracts more pollutants on the surface of the samples. A set of bands located from 900 cm⁻¹ to 1100 cm⁻¹ seems to

be linked to the presence of the clay. As, these bands which clearly appear in the case of high amount of clay (Ag-TiO₂: clay corresponding to 1:1 and 1:0.5), are quasi-absent when the clay content is very low. The band that appears at 914 cm⁻¹ is associated with the vibration of hydroxyls groups of aluminum surface (Al-OH). The band located around 1019 cm⁻¹ is related to the stretching vibration of Si-O-Si bonds. Whereas the one 1112 cm⁻¹ is corresponded to the stretching vibration of Si-O bonds [22]. The FTIR band at 1500 cm⁻¹ could be assigned to the interaction between Ag and TiO₂ particles [23].

The X-ray diffraction patterns of clay and the prepared [AgTiO₂]:[clay] samples are shown in Figure 3. The [AgTiO₂]:[clay] pattern shows the presence of phases related to the initial constituent elements (i.e. Ag, TiO₂ and clay). The TiO₂ detected is anatase phase with the mains peaks at 25.65˚ and 54.41˚ corresponding to the [1 0 1] and [1 0 5] crystal planes respectively [20] [24] [25]. Therefore, there were no rutile and brookite phases [26] [27]. Silver (Ag) peaks corresponding to [1 1 1], [2 0 0], and [2 2 0] reflections appear at 38.08˚, 48.43˚ and 63.07˚. Also, the peaks of kaolinite (Al₂Si₂O₅(OH)₄) and quartz (SiO₂) are observed at 35.23˚ and 36.68˚, respectively due to the presence of clay.

The photocatalytic efficiencies of the prepared nanocomposites were evaluated by degradation of 25 mg/L solution of Orange II under visible irradiation. The experimental results for the degradation of Orange II are given in Figure 4(a) and Figure 4(b) for commercial TiO₂, Ag doped TiO₂ and [AgTiO₂]:[clay] with different ratios of clay. The commercial TiO₂ which is a standard photocatalyst was used as the reference to compare its photodegradation activity for dye with the one of AgTiO₂ and [AgTiO₂]:[clay] samples. In fact, this comparison is

necessary to evaluate the synergic effect of the prepared nanocomposites. Figure 4(a) shows that composites of clay and silver doped TiO₂ nanoparticles exhibit better photocatalytic activity than that of the commercial TiO₂ nanoparticles. The good performance of the prepared nanocomposite is due to the combined effect of the silver and the clay. Clay provides better adsorption characteristics to the nanoparticles whereas silver helps to increase the electrical properties of the samples. Furthermore, findings showed that the increase in the clay content in the system induces a decline in the sample activity. This could be due to the coating of TiO₂ nanoparticles by clay. This coating of TiO₂ NPs could be blocking them from exposure to the dye molecules and hence stopping them from doing their action. Degradation pattern of nanoparticles could be better evaluated from Figure 4(b) as well where we showed the percentage degradation of each composite as compared to the TiO₂ nanoparticles. For commercial TiO₂, 22% of Orange II were removed after 180 min of irradiation. When we have doped TiO₂ with Ag, the removal efficiency increase is from 22% to 27%. When Ag doped TiO₂ is associated to clay, the removal efficiency increase from 27% to 32%, 54%, 57%, 58%, and 62% for 5, 0.5, 2.5, 0.25 and 0.05 g amounts of clay added, respectively.

Kinetics study of the photocatalytic degradation of 25 mg/L solution of Orange

II is described using the pseudo-first-order model (Figure 5): ln ( C 0 C t ) = k t ;

where C 0 and C t are the concentrations of dye in the solution at time 0 and t (min), respectively, k is the rate constant (min⁻¹). The results of rate constant and R² are displayed in Table 1. These results reveal that the rate constant for TiO₂ commercial increase to 19% with incorporation of Ag in the photocatalyst.

This observation could be attributed to the reduction of recombination of electron and holes. Table 1 shows that the AgTiO₂/clay have rate constant which is higher than the Ag doped titanium oxide. This is due to the synergic effect between adsorption and photoactivity. The presence of clay increases the surface area of the nanocomposite that offers more sites for the dye to adsorb and hence degrade. However, the rate constant decrease when the amount of clay is important. The (AgTiO₂)(clay)[1:1] sample displayed rate constant 2.34 times lower than (AgTiO₂)(clay)[1:0.01]. The slow rate constant might be due to the reduction of hydroxide radical production resultant to the react of TiO₂ and the photons. Thus, the large amount of clay prevents TiO₂ to products hydroxyl radicals necessary for the dye degradation.

For antimicrobial activity, we named the nanocomposites 18, 19, 20, 21, 22 and 23. 18 is silver doped TiO₂ and clay nanocomposite with ratio 1:1, 19 is silver doped TiO₂ and clay nanocomposite with ratio 1:0.5, 20 is silver doped TiO₂ and clay nanocomposite with ratio 1:0.1, 21 is silver doped TiO₂ and clay nanocomposite with ratio 1:0.05, 22 is silver doped TiO₂ and clay nanocomposite with ratio 1:0.01, 23 is silver doped TiO₂ nanoparticles.