Qishe Yan

Efficient photocatalytic degradation of tetracycline hydrochloride by Ag3PO4 under visible-light irradiation

A facile, environmental-friendly Ag3PO4-PN photocatalyst was synthesized by a simple precipitation method at room temperature in the presence of ammonia and polyvinyl pyrrolidone (PVP). As-synthesized samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV–visible diffuse reflectance spectroscopy (UV–vis DRS). The enhancement of photocatalytic efficiency of Ag3PO4-PN is strongly dependent on the excellent photo-absorption capacity, sharp edges and corners, and synergistic effect of PVP and NH3·H2O. The effects of catalyst dosage, TC concentration and solution pH were explored with tetracycline hydrochloride (TC) as target contamination. The mineralization was evaluated by total organic carbon (TOC) analysis and determination of the concentration of inorganic ions such as NO3− and Cl−. Radical detection experiment indicated the h+ and ·O2− are major active species in the degradation of TC by Ag3PO4-PN. Moreover, photocatalyst stability and regeneration experiments exhibited the favorable stability and rejuvenation ability, suggesting a promising prospect of practical application of Ag3PO4 in the wastewater treatment.

Efficient visible-light photocatalytic degradation of sulfadiazine sodium with hierarchical Bi7O9I3 under solar irradiation

Bi₇O₉I₃, a kind of visible-light-responsive photocatalyst, with hierarchical micro/nano-architecture was successfully synthesized by oil-bath heating method, with ethylene glycol as solvent, and applied to degrade sulfonamide antibiotics. The as-prepared product was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-visible diffuse reflection spectra and scanning electron microscopy (SEM). XRD and XPS tests confirmed that the product was indeed Bi₇O₉I₃. The result of SEM observation shows that the as-synthesized Bi₇O₉I₃ consists of a large number of micro-sheets with parallel rectangle structure. The optical test exhibited strong photoabsorption in visible light irradiation, with 617 nm of absorption edges. Moreover, the difference in the photocatalytic efficiency of as-prepared Bi₇O₉I₃ at different seasons of a whole year was investigated in this study. The chemical oxygen demand removal efficiency and concentration of NO(3)(-) and SO(4)(2-) of solution after reaction were also researched to confirm whether degradation of the pollutant was complete; the results indicated a high mineralization capacity of Bi₇O₉I₃. The as-synthesized Bi₇O₉I₃exhibits an excellent oxidizing capacity of sulfadiazine sodium and favorable stability during the photocatalytic reaction.

Sorption of chloramphenicol on pond sediments and the effect of coexistence Cu(II)

The sorption of chloramphenicol on four types of sediment and the effect of coexistence Cu(II) on the sorption were studied. Sorption isotherms and thermodynamic analysis were employed to dispose the experimental sorption data. Experimental results showed that organic matter was the dominant parameter and the coexistence of heavy metal Cu(II) could promote the sorption of chloramphenicol on four tested sediments. The adsorption parameter analysis showed sorption of chloramphenicol on the sediment was not pure distributional effects, not a strong interaction between molecule and surface, but other weak interactions. Thermodynamic parameters values such as ΔG, ΔH and ΔS were all below zero, which indicated that the sorption was a spontaneous and exothermal process.

Synthesis of graphene oxide/Ag3PO4 composite with enhanced visible-light photocatalytic activity

The nano-scale Ag3PO4 was successfully synthesized by the silver ammonia complexing precipitation method at room temperature. And the Graphene oxide (GO)/Ag3PO4 nanocomposites with different contents of GO were successfully synthesized using the electrostatic driving method. The as-prepared GO/Ag3PO4 nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV–visible diffuse reflectance spectroscopy (UV–Vis DRS), confirming that Ag3PO4 were highly dispersed to GO sheet. The photocatalytic properties of GO/Ag3PO4 were evaluated by the degradation of Methyl Orange (MO) under visible light irradiation and solar irradiation respectively. The results showed that the photocatalytic efficiencies of GO/Ag3PO4 nanocomposites had enhanced largely and the kinetics reaction models were followed first-order. Furthermore, 5% GO/Ag3PO4 exhibited the highest photocatalytic activity on degradation of MO under visible-light irradiation. The improved photocatalytic performances of the GO/Ag3PO4 nanocomposites mainly attributed to the introducing of GO, which benefit for electron transfer and inhibit the recombination of electron–hole pairs, promoting the practical application of Ag3PO4 in water purification.

Degradation of Sulfadimethoxine and Products in Aqueous Solution by BiOI Under Visible Light with H2O2

A visible light-induced BiOI photocatalytic process was used to degrade sulfadimethoxine (SDM). The highest degradation efficiency of SDM was 96% after 2 h of visible light irradiation. The chemical oxygen demand (COD) of the solution decreased substantially and the high COD removal achieved 88%. During this time, the organic sulfur was recovered in the form of sulfate and the organic nitrogen was retrieved in the form of nitrate. Moreover, the high photodegradation efficiency and the less toxic photodegradation products suggest BiOI is a likely photocatalyst for the degradation of SDM under visible light.

Synthesis of Bi-Co 0.5 Zn 0.5 Fe 2 O 4 /AgBr hybrids with enhanced visible-light photocatalytic activity

The Bi-Co0.5Zn0.5Fe2O4/AgBr photocatalyst was fabricated by facile sol–gel and hydrothermal methods. The crystal phase, microstructures, morphologies composition, chemical states and optical absorption property were studied by XRD, SEM, XPS and UV–Vis diffuse reflection spectroscopy, respectively. The degradation capability for methyl orange was evaluated under visible light irradiation. The results show that the hybrid photocatalyst exhibited higher photocatalytic activity than pure AgBr, among which 15% Bi-Co0.5Zn0.5Fe2O4/AgBr (Bi-Co0.5Zn0.5Fe2O4/AgBr, 15%) emerge the highest degradation efficiency (85.2%) in an hour. The enhanced photocatalytic activity could be attributed to the enhancement of the visible absorption range. Free radicals trapping experiments reveal that ·OH plays a key role in catalytic action. Furthermore, the introducing of Bi-Co0.5Zn0.5Fe2O4/AgBr provides the composite a good photocatalytic property, which is expected to widely applied in water purification.

A research on shape-controllable synthesis of Ag3PO4/AgBr and its degradation of ciprofloxacin

Antibiotic ciprofloxacin is one of the commonly used broad spectrum fluoroquinolone human and veterinary drugs. Because of the overuse of human beings, the presence of ciprofloxacin has been detected in a variety of environmental matrices. To solve this problem, a facile, environmentally-friendly Ag3PO4/AgBr composite photocatalyst was synthesized by a simple precipitation method at room temperature in the presence of cetyltrimethyl ammonium bromide (CTAB). CTAB was served as surfactant and the source of bromide ions. The as-prepared Ag3PO4/AgBr microspheres were characterized by means of powder X-ray diffraction (XRD), scanning electron microscope (SEM) and UV-visible diffuse reflectance spectroscopy (UV-vis DRS). The results revealed that the Ag3PO4/AgBr sample (synthesized with CTAB, 0.8 g) exhibited the highest photocatalytic activity to the photodegradation rate of 96.36%. Moreover, mechanism detection experiment indicated that h+ was the major active species in the degradation process. So the enhanced photocatalytic activity of Ag3PO4/AgBr composites is attributed to its excellent separation of photogenerated electron-hole pairs through Ag3PO4/AgBr heterojunction. Also, Ag3PO4/AgBr heterojunction has a lower band gap compared to pure Ag3PO4 and pure AgBr, so higher efficiency of light harvesting is equipped.

Treatment of domestic wastewater using composite ecological system in Chinese rural area

In this study, a newly developed contaminant removal system for domestic wastewater in rural area was used at the first time in Henan province, China. This composite ecological system (CES) consists of septic tank (ST), improved soil filter (ISF) and surface flow wetland (SFW). The performances of the system was to investigate the removal of biological oxygen demand (BOD), total nitrogen (TN), total phosphorus (TP), total suspend solid (TSS) and total coliform, and to evaluate its technical and economical suitability. The wastewater treatment capacity of the constructing system is 200 m3 d−1. The results show that the average removal values of the combined system which has been observed in a 14-month period are as follows: BOD = 90%, TN = 83%, TP = 98% and TSS = 93%. The intermittent result of the removal total bacterial count and total coliform are 2.1 to 2.6 log unit and the dissolved oxygen increases from 0.8 to 3.5 mg l−1. The facts indicate that the system is a cost-effective and technically feasible process for rural area domestic sewage treatment.