Removal of water-soluble dyes and pharmaceutical wastes by combining the photocatalytic properties of Ag₃PO₄ with the adsorption properties of halloysite nanotubes

Contaminated water can be best treated by a combination ofzi water treatment technologies such as photocatalysis and adsorption. A photocatalyst-adsorbent system made up of Ag₃PO₄ and halloysite nanotubes (HNTs) was synthesized by precipitating Ag₃PO₄ in the presence of dispersed HNTs. The synthesized Ag₃PO₄–HNTs were characterized by X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FTIR), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDX), thermogravimetric analysis (TGA), and diffuse reflectance spectroscopy (DRS). The as-prepared Ag₃PO₄–HNTs showed high photocatalytic activity in visible light and high efficiency of adsorption for water-soluble dyes, such as methylene blue and rhodamine B, and pharmaceutical chemicals, such as diclofenac sodium, ibuprofen, flurbiprofen, naproxen sodium, and carbamazepine. The efficiency of the photocatalytic activity and the adsorption capacity of Ag₃PO₄–HNTs were dependent on the percentage of HNTs in the photocatalytic-adsorbent material of Ag₃PO₄–HNTs. The intermediate products for the photodegradation of ibuprofen and naproxen sodium were identified with liquid chromatography-mass spectrometry (LC-MS). The synthesized Ag₃PO₄–HNT composites showed good potential application in the treatment of polluted water.