Striking the balance: Unveiling the interplay between photocatalytic efficiency and toxicity of La-incorporated Ag3PO4

Persistent molecules, such as pesticides, herbicides, and pharmaceuticals, pose significant threats to both the environment and human health. Advancements in developing efficient photocatalysts for degrading these substances can play a fundamental role in remediating contaminated environments, thereby enhancing safety for all forms of life. This study investigates the enhancement of photocatalytic efficiency achieved by incorporating La3+ into Ag3PO4, using the co-precipitation method in an aqueous medium. These materials were utilized in the photocatalytic degradation of Rhodamine B (RhB) and Ciprofloxacin (CIP) under visible light irradiation, with monitoring conducted through high-performance liquid chromatography (HPLC). The synthesized materials exhibited improved stability and photodegradation levels for RhB. Particularly noteworthy was the 2% La3+-incorporated sample (APL2), which achieved a 32.6% mineralization of CIP, nearly three times higher than pure Ag3PO4. Toxicological analysis of the residue from CIP photodegradation using the microalga Raphidocelis subcapitata revealed high toxicity due to the leaching of Ag + ions from the catalyst. This underscores the necessity for cautious wastewater disposal after using the photocatalyst. The toxicity of the APL2 photocatalysts was thoroughly assessed through comprehensive toxicological tests involving embryo development in Danio rerio, revealing its potential to induce death and malformations in zebrafish embryos, even at low concentrations. This emphasizes the importance of meticulous management. Essentially, this study adeptly delineated a thorough toxicological profile intricately intertwined with the photocatalytic efficacy of newly developed catalysts and the resultant waste produced, prompting deliberations on the disposal of degraded materials post-exposure to photocatalysts.

Temperature-dependent phonon dynamics of Ag3PO4 microcrystals

In this work, we present the study of the temperature-dependent behavior of silver orthophosphate (Ag₃PO₄) microcrystals using in situ Raman scattering. The Ag₃PO₄ as-synthesized microcrystals were prepared by the precipitation method and characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman and infrared spectroscopy, and differential scanning calorimetry (DSC). Temperature-dependent phonon dynamics were performed on Ag₃PO₄ microcrystals and pointed to a first-order phase transition in the temperature range 500-515 °C: Phase I (25-500 °C) → Phase II (515-590 °C). The phase transition is reversible and a temperature hysteresis was observed during the heating - cooling process: Phase II (590-470 °C) → Phase I (455-25 °C). The reversible phase transition is related to the distortion of the tetrahedral symmetry of PO₄ caused by the decrease in the crystalline order. DSC analysis confirmed the results of temperature-dependent Raman spectroscopy.

Significant visible-light photocatalytic enhancement in Rhodamine B degradation of silver orthophosphate via the hybridization of N-doped graphene and poly(3-hexylthiophene)

Organic pollutants as typical water contaminants are potentially harmful to human health. In this study, we suggested that the novel Ag3PO4/N-doped graphene (NG)/Poly(3-hexylthiophene) (P3HT) composites can remove the organic dye Rhodamine B (RhB) from water. This Ag3PO4-based photocatalyst was synthesized via a facile method and subsequently characterized by XRD, SEM, TEM, XPS, Raman spectroscopy, PL spectroscopy, and UV-vis DRS. The photocatalytic activity of Ag3PO4/NG/P3HT composites is significantly higher than that of pristine Ag3PO4, Ag3PO4/NG, and Ag3PO4/P3HT for RhB degradation under visible light irradiation, especially the kinetic constant of Ag3PO4/NG/P3HT is more than 6 times of pristine Ag3PO4. The reactive oxygen species trapping experiments indicate that the degradation of RhB over the Ag3PO4/NG/P3HT composites mainly results from the holes oxidation and superoxide radical reduction. Besides, Ag3PO4/NG/P3HT composites exhibit better recyclability and stability than pristine Ag3PO4. Furthermore, the photocatalytic mechanism of Ag3PO4/NG/P3HT composites for RhB degradation under visible light was proposed as the synergistic effect of irradiated Ag3PO4, P3HT and NG sheets on the effective separation of photogenerated electron-hole pairs, and the enhancement of visible light absorbance.

High efficient multifunctional Ag3PO4 loaded hydroxyapatite nanowires for water treatment

Organic, inorganic, and biological pollutants are typical water contaminants and they seriously affect water quality. In this study, we suggested that a novel multifunctional Ag3PO4 loaded hydroxyapatite (HAP) material can remove the typical pollutants from water. The Ag3PO4/HAP composites were synthesized facilely via in-situ precipitation of Ag3PO4 on the pre-existing HAP nanowires. By optimizing the composition of Ag3PO4 and HAP, the material could achieve an optimal photocatalytic activity to decompose rhodamine B (RhB), methyl orange (MO) and methylene blue (MB) under visible light irradiations with enhanced pH stability. Besides, the adsorption of Pb(II) on the Ag3PO4/HAP reached a maximum capacity of 250 mg/g and this value was approximately three times as that of pure HAP. Furthermore, the composite material exhibited excellent antibacterial activities towards gram-negative bacterium (Escherichia coli) and gram-positive bacterium (Stphylococcus aureus). The results highlighted the cooperative effect between Ag3PO4 and hydroxyapatite (HAP). The simultaneous removals of dyes, toxic metal ions, and bacteria with a high efficiency followed an easy approach for the purification of contaminated water via the rationally designed material, in which the Ag3PO4/HAP composite might be developed as a general water treatment material with multiple functions.