Prominent Visible Light Photocatalytic and Water Purification Activity of PbS/CdS/CdO Nanocomposite Synthesized via Simple Co-Precipitation Method

Background: Due to unique chemical and physical properties and potential application in many fields, nanostructured materials have attracted many attentions. Cadmium sulfide (CdS) is a semiconductor that has a wide band gap of 2.42 eV at room temperature and can be served in solar cells and photoluminescence devices. Cadmium sulfide (CdS) is a kind of attractive semiconductor material, and it is now widely used for optoelectronic applications. CdS nano and microstructures can be synthesized via different chemical methods such as microwave-solvothermal synthesis, surfactant-ligand coassisting solvothermal method and hydrothermal route. Also different morphologies of this semiconductor such as dendrites, nanorods, sphere-like, flakes, nanowires, flower-like shape triangular and hexagonal plates, were synthesized. Methods: To synthesis of the nanocomposite, a simple co-precipitation method was served. In briefly, 0.1 g of Pb(NO3)2 was dissolved in the distilled water (Solution 1). Also different aqueous solutions were made from dissolving different mole ratio of Cd(NO3)2.6H2O respect to the lead source in the water (Solution 2). Two solutions were mixed together under vigorous stirring and then S2- solution (0.02 g thiourea in the water) was added to the Pb2+/Cd2+ solution. After that 0.1 g of CTAB as surfactant was added to the final solution. Finally to the synthesis of both sulfide and oxide nanostructures, NaOH solution was added to the prepared solution to obtain pH= 10. Distilled water and absolute ethanol were used to wash the obtained precipitate and then it dried at 80 °C for 8 h. Results: From the XRD pattern it was found that the peaks placed at 24.9°, 27°, 44.1°, 48°, 52°, 54°, 57.8°, 66.8°, 71.2° are associated to CdS compound with hexagonal phase (JCPDS=00-001-0780) that belong to (100), (002), (110), (103), (112), (201), (202), (203), (211) Miller indices respectively. The Other peaks belong to PbS with hexagonal phase (JCPDS=01-078-1897), and CdO with cubic phase (JCPDS=00-001-1049). From SEM images, it was found by choosing the mole ratio to 1:1, very small and uniform particles were achieved. By increasing Pb2+/Cd2+ mole ratio to 1:2, very tiny particles aggregated together were achieved. Conclusion: The results showed that the product can adsorb extra 80% of heavy metal ions from the water. So it can be said that the nanocomposite can be used in the water treatment due to its high photocatalytic and surface adsorption activities. In other words, it can remove heavy metals from the water and also decompose organic pollutions.