[Adsorption Performance and Mechanism of Oxytetracycline in Water by KOH Modified Biochar Derived from Corn Straw].

The pollution control of tetracycline antibiotics in the environment has become a hot topic, and biochar adsorption has become an important technology to remove organic pollutants. Pyrolytic biochars (BC400, BC500, and BC600) were prepared from corn straw and then were modified by KOH to obtain KBC400, KBC500, and KBC600. Among them, KBC400 was selected for secondary pyrolysis activation at 400-600℃ to obtain AKBC400, AKBC500, and AKBC600. The structure characteristics and surface properties of AKBC were also characterized. The adsorption kinetics and thermodynamic characteristics of oxytetracycline hydrochloride (OTC) in the solution by AKBC were investigated using batch experiments. Compared to that of BC400, the specific surface area and pore structure of AKBC were significantly improved, and the aromaticity was also enhanced, resulting in the notable enhancement of the adsorption capacities for OTC. The pseudo-second-order kinetics model could better fit the adsorption process, and AKBC500 had the largest adsorption rate constant and capacity. Both the intraparticle diffusion and film diffusion were the rate-limiting steps. The Langmuir, Freundlich, and Temkin models could fit the adsorption isotherms perfectly. The adsorption of OTC on AKBC was a spontaneous, endothermic, and entropy-increasing process by both physisorption and chemisorption. The pH values in the range of 3.0-7.0 were favorable for the adsorption of OTC by AKBC. The adsorption capacity decreased with the humic acid concentration over 10 mg·L-1. The adsorption mechanism of OTC by AKBC involved pore filling, hydrogen bonding, π-π conjugation, cation-π bond, and strong electrostatic effect. AKBC still had good reusability for OTC removal after five times of regeneration. The obtained AKBC is a potential adsorbent for OTC removal from water due to the good pore structure, high adsorption capacity, and stable adsorption effect.

Efficient photocatalytic H2 evolution and Cr(VI) reduction under visible light using a novel Z-scheme SnIn4S8/CeO2 heterojunction photocatalysts.

Semiconductor photocatalysis technology is a promising method for hydrogen production and water pollution treatment. Here, the SnIn4S8/CeO2 (SISC) composites were fabricated by a stirring and calcination method, and the mass ratio of SnIn4S8 to CeO2 was optimized. The 50 wt% SISC heterojunction photocatalyst has the highest visible light catalytic activity. The degradation rate of hexavalent chromium (Cr (VI)) is 98.8% in 75 min of light irradiation, which is 2.48 times that of pure CeO2. Besides, the 50 wt% SISC composite photocatalyst also has the highest photocatalytic hydrogen production efficiency (0.6193 mmol g-1 h-1), which exhibits a higher photocatalytic activity than pure CeO2 and SnIn4S8. The enhanced photocatalytic performance can be attributed to the Z-scheme heterojunction structure between CeO2 and SnIn4S8, which can effectively separate and transfer photo-generated charges, thereby reducing the recombination of photo-generated carriers. We hope this work can provide ideas for constructing Z-scheme heterojunction structures and improving photocatalytic activity under visible light.

Highly efficient activation of peroxymonosulfate by Co3O4/Bi2WO6 p-n heterojunction composites for the degradation of ciprofloxacin under visible light irradiation.

Photocatalytic technology assisted via peroxymonosulfate (PMS) has good potential in water treatment. In this study, the Co3O4/Bi2WO6 composite was constructed via an in-situ calcination process and used to activate PMS for the degradation of ciprofloxacin (CIP) under visible light irradiation. The obtained 5 wt% Co3O4/Bi2WO6(CBWO-2) can highly effectively remove 86.2% CIP within 5 min visible light irradiation in presence of PMS. The excellent degradation performance of Co3O4/Bi2WO6/PMS system can be attributed to the synergistic effect between p-n heterojunction and PMS activation. The conduction band and valence band deviation between Co3O4 and Bi2WO6 were calculated by XPS techniques. Besides, DFT calculations were performed to further confirm the internal structure between Co3O4 and Bi2WO6. This work not only provides an approach to fabricate heterostructures but also indicated that Co3O4/Bi2WO6/PMS/Vis system is a potential environment remediation alternative for the efficient removal of recalcitrant organic compounds from wastewaters.

Novel Z-scheme W18O49/CeO2 heterojunction for improved photocatalytic hydrogen evolution.

The novel Z-scheme heterojunction photocatalyst W18O49/CeO2 was prepared by hydrothermal synthesis. The photocatalytic properties of W18O49/CeO2 were evaluated by photocatalytic hydrogen evolution under visible light. The result shows that the 15 wt% W18O49/CeO2 composite has the best hydrogen production efficiency of about 0.2061 mmol g-1h-1, which was 1.93 times higher than that the obtained pure CeO2. The characterization results demonstrated that the existence of Z-scheme heterojunction structure at the contact interface of W18O49 and CeO2 was the origin of the enhanced photocatalytic performance for hydrogen evolution, which could greatly increase the accumulation of photo-generated electrons and the separation efficiency of charge carrier. In accordance with density functional theory (DFT) calculation, we further confirmed the formation of Z-scheme heterojunction structures. This work is anticipated to expand the ideas for modifying CeO2 semiconductor materials to improve the rate of photocatalytic hydrogen production.

Photocatalytic degradation of sulfamethazine using a direct Z-Scheme AgI/Bi4V2O11 photocatalyst: Mineralization activity, degradation pathways and promoted charge separation mechanism.

Z-scheme heterojunction can not only promote the separation of photogenerated carriers, but also retain the strong redox potential of the system, which would greatly improve the photocatalytic performance of catalyst. Herein, a Z-scheme AgI/Bi4V2O11 heterojunction photocatalyst was prepared by a hydrothermal process combined with in situ coprecipitation process. Multiple techniques were employed to investigate the morphology, composition, chemical and electronic properties of the as-prepared samples. The obtained Z-scheme AgI/Bi4V2O11 heterojunction photocatalyst exhibited remarkably enhanced photocatalytic performance towards sulfamethazine (SMZ) degradation under visible light irradiation. Especially, the 20 wt% AgI/Bi4V2O11 composites exhibited the highest photocatalytic activity for sulfamethazine (SMZ) degradation and 91.47% SMZ would be eliminated within 60 min. In comparison with NO3- and SO42-, the presence of Cl- and HCO3- presented more obviously inhibition effects on SMZ degradation. The possible degradation pathways of SMZ were speculated by identifying degradation intermediates. O2-, h+ and OH all involved in the photocatalytic degradation SMZ. The highly enhanced photocatalytic performance might be attributed to form Z-scheme junction between AgI and BVO, which are conducive to the efficient charges separation and maintain high redox potential. This work enriches Bi4V2O11-based Z-scheme heterojunction photocatalytic system and provides a reference for the preparation of effective Z-scheme junction photocatalysts.

Constructing magnetic and high-efficiency AgI/CuFe2O4 photocatalysts for inactivation of Escherichia coli and Staphylococcus aureus under visible light: Inactivation performance and mechanism analysis.

Magnetic materials usually exhibit advanced performance in many areas for their easy separating and recycle ability. In this study, silver iodide/copper ferrite (AgI/CuFe2O4) catalysts with excellent magnetic property were successfully synthesized and characterized by a series of techniques. Two typical bacteria Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were applied to estimate the photocatalytic inactivation performance of obtained AgI/CuFe2O4 catalysts. Results revealed that the AgI/CuFe2O4 (12.5% AgI) composite could absolutely inactivate 3 × 109 CFU/mL E. coli and 2.7 × 108 CFU/mL S. aureus cells severally in 50 min and 40 min under visible light irradiation, which showed a much higher photo-disinfection activity than monomers. Transmission electron microscopy was used to study the biocidal action of this nanocatalyst, the results confirmed that the treated E. coli cells were damaged, the nanocatalyst permeated into cells and resulting in death of cells. Besides, it was found that the destruction of bacterial membrane together with substantial leaked potassium ion (K+) which caused by the photo-generated reactive species superoxide radical (O2-) and holes (h+) could be the direct disinfection principles. For a deep insight into practical applications, the influences of different catalyst concentrations and reaction pH were also taken into discussion in details. The overall results indicated the novel photocatalyst with strong redox capacity and outstanding reusability can be widely employed in bacteria elimination.

Construction of a high-performance photocatalytic fuel cell (PFC) based on plasmonic silver modified Cr-BiOCl nanosheets for simultaneous electricity production and pollutant removal.

The development of high-performance photocatalytic fuel cells (PFCs) is seriously hampered by poor light utilization rates and low charge carrier transfer efficiency. Herein, we have experimentally obtained plasmonic Ag modified Cr-BiOCl (Cr-BOC/Ag) with high visible light photocatalytic activity and provided direct evidence for the substantially enhanced catalytic activity in metal-semiconductor photocatalysts. The experimental results revealed that the Cr doping and Ag modification could not only extend the photo absorption of BiOCl from the UV to the visible light region but could also greatly increase the generation and transfer rate of charge carriers because of its narrowed band gap and the localized surface plasmon resonance (LSPR) effect of metallic Ag. Under visible light irradiation, the Cr-BOC/Ag showed a remarkable enhancement in the PFC performance when the optimum contents of Cr doping and Ag loading was 14.4% and 4%, respectively. The trapping experiments and multiple characterizations demonstrated that the advantageous combination of the Cr doping effect and SPR effect induced by the Ag nanoparticles is responsible for the high generation rate of oxidative species and effective charge carrier transfer. By using RhB as fuel, approximately 75.1% color removal efficiency and 8.38% coulombic efficiency were obtained under visible light irradiation for 240 min, which are higher than those of MO and TC. In addition, the Jsc and Voc of the Cr-BOC/Ag photoanode were measured to be 0.0073 mA cm-2 and 0.543 V.

Fabrication of visible-light-driven silver iodide modified iodine-deficient bismuth oxyiodides Z-scheme heterojunctions with enhanced photocatalytic activity for Escherichia coli inactivation and tetracycline degradation.

At present, various organic pollutants and pathogenic microorganisms presented in wastewater have severely threatened aquatic ecosystem and human health. Meanwhile, semiconductor photocatalysis technology for water purification has attracted increasingly significant attention. Herein, we successfully constructed a series of novel visible-light-driven (VLD) Bi4O5I2/AgI hybrid photocatalysts with different AgI amounts. Compared with pristine AgI and Bi4O5I2, Bi4O5I2/AgI with the optimal AgI contents exhibited remarkably enhanced photocatalytic performance in probe experiment for Escherichia coli (E. coli) disinfection and tetracycline (TC) degradation. The efficiency for TC degradation and E. coli inactivation reached 82% and 100% in 30 min, respectively. The enhanced electron-hole separation efficiency was responsible for improved photocatalytic activity. In addition, the destruction process of the chemical structure of TC molecules was further investigated by three-dimensional excitation-emission matrix fluorescence spectra (3D EEMs). The activity and crystal phase of the catalysts did not change significantly after four cycles, demonstrating their excellent recyclability and stability of catalysts. The Ag+ ion leaking experiments, radical trapping experiments and ESR tests demonstrated that OH, O2- and h+ were the main active species in photocatalytic disinfection processes. Furthermore, the photocatalytic mechanism of Bi4O5I2/AgI nanomaterials was discussed in detail in conjunction with the energy band structure, and a reasonable Z-scheme interfacial charge transfer mechanism was proposed. This work is expected to provide an efficient water disinfection method.

Construction of 2D heterojunction system with enhanced photocatalytic performance: Plasmonic Bi and reduced graphene oxide co-modified Bi5O7I with high-speed charge transfer channels.

The efficient electron-hole charge pair separation, ultra-fast electron migration and excellent light harvest capacity are essential for semiconductor photocatalyst with superior photocatalytic performance. In this study, we constructed layered 2D/2D heterojunction composite of Bi@Bi5O7I/rGO (BiBGOI) through a facile surface charge mediated self-assembly strategy. The unique 2D/2D heterostructure with face to face contact can increase the contact area and generate a large amount of charge transfer nanochannels in the interfacial heterojunction, resulting in the enhancement of photocatalytic activity. Addition of semimetal Bi can enhance light absorption, and the local electromagnetic field dominated by SPR effect is favorable for photoinduced charge pair separation. The novel composite showed superior photocatalytic performance for decomposing levofloxacin (LVFX), which was attributed to the unique 2D/2D structure and SPR effect. The enhanced mineralization ability of the novel composite was ascribed to the strong oxidization ability of photoinduced holes, further evaluating high charge pair separation efficiency. In addition, the strong adsorption capacity of rGO for LVFX molecules can enable active radicals transfer into the surface to decompose it. This work will shed light on constructing 2D/2D heterojunction system assisted with SPR effect for the practical application in removal of organic pollutants.

Enhanced photocatalytic activity of CdS/SnS2 nanocomposite with highly-efficient charge transfer and visible light utilization for selective reduction of 4-nitroaniline.

Photocatalytic reduction can be an effective and promising technology for the selective reduction of aromatic nitro organics. In this paper, a novel Z-scheme CdS/SnS2 photocatalyst was well-designed and fabricated via simple in-site reaction process containing thioacetamide as a sulfur sources and cubic CdSnO3 as template. The resulting CdS/SnS2 composite has well-constructed cubic nanostructure of strong adhesion between CdS and SnS2, presenting high absorption to visible light. Importantly, strong charge transfer between the contacting regions of CdS and SnS2 through the intermediate sulfur atoms combined with both metals was generated, which speeds up separation of photogenerated electron and hole. The advantageous combination of high light-harvesting and effective charge transfer is responsible for the excellent photocatalytic activity at the CdS/SnS2 heterointerface. Resultantly, the prepared CdS/SnS2 composites exhibit high conversion efficiency and selectivity on 4-nitroaniline (4-NA) reduction in the aqueous solution containing ammonium formate under visible light irradiation, which can reduce almost all 4-NA within 12 min. Trapping experiments and ESR analysis demonstrated that ammonium formate not only can effectively decrease recombination of photogenerated charge carriers but also react with holes to generate CO2- radicals possessing strong reduction ability. The 4-NA are effectively photo-reduced by the synergistic effect of electrons and CO2- radicals. According to the experimental results, a possible Z-scheme charge transfer mechanism was proposed. Besides, the photo-reduction of aromatic nitro organics possessed different para-groups (p-nitrophenol, nitrobenzene, and p-nitrobenzaldehyde) was also investigated. It is found that the electron-drawing group can decrease the electron density of its para-position nitryl, which quickens the nitro reduction.

Construction of highly efficient and stable ternary AgBr/Ag/PbBiO2Br Z-scheme photocatalyst under visible light irradiation: Performance and mechanism insight.

In this work, the novel ternary AgBr/Ag/PbBiO2Br Z-scheme photocatalysts were synthesized via a CTAB-assisted calcination process. The AgBr/Ag/PbBiO2Br composites were employed for the degradation of rhodamine B (RhB) and antibiotic bisphenol A (BPA) under visible light irradiation. Results showed that the obtained AgBr/Ag-3/PbBiO2Br displayed optimal photocatalytic performance, which could remove almost all RhB within 25 min and effectively decompose 82.3% of BPA in 120 min. Three-dimensional excitation-emission matrix fluorescence spectra (3D EEMs) were utilized for the purposes of fully grasping the behaviors of RhB molecules during the reaction process. Meanwhile, the effects of initial RhB concentration and co-existent electrolytes were investigated from the viewpoint of practical application. In addition, there was no obvious loss in degradation efficiency even after four cycles. The enhanced photocatalytic performances of AgBr/Ag/PbBiO2Br could be credited to the accelerated interfacial charge transfer process and the improved separation of the photogenerated electron-hole pairs. The existence of a small amount of metallic Ag played a significant role in preventing AgBr from being further photocorroded, resulting in the formation of a stable Z-scheme photocatalyst system. This study demonstrated that using metallic Ag as an electron mediator to construct Z-scheme photocatalytic system provided a feasible strategy in promoting the stability of Ag-based semiconductors.

A facile strategy to fabricate hollow cadmium sulfide nanospheres with nanoparticles-textured surface for hexavalent chromium reduction and bacterial inactivation.

Exploring morphology and surface structure of semiconductor photocatalyst is crucial for researching their photocatalytic performance. In this paper, hollow CdS nanospheres (CdS-HSs) were successfully fabricated via simple template self-removal strategy. The prepared CdS-HSs were characterized by XRD, SEM, HR-TEM, UV-vis diffuse reflectance spectra (DRS), XPS, photocurrent response (I-T), photoluminescence (PL) and electrochemistry impedance spectroscopy (EIS). It was found that the prepared CdS-HSs have nanoparticles-textured surface composed of ultra-small CdS nanoparticles (∼20 nm) and large surface areas. DRS result demonstrated that the CdS-HSs exhibit strong visible light absorption capacity. The results of photocurrent response, photoluminescence and EIS revealed that hollow structure and nanoparticles-textured surface can effectively increase light reflection effect and decrease recombination rate of electrons and holes. Compared to the traditional CdS, the hollow CdS nanospheres exhibit higher photocatalytic activity on Cr(VI) reduction under visible light irradiation, which are primarily attributed to its rapid separation of electron-hole pairs and improved visible light absorption. Moreover, CdS-HSs was also demonstrated as an effective and potential material on photocatalytic disinfection. The result of mechanism experiments proved that h+, e- and O2- play important roles on the bacteria inactivation.

Enhanced Escherichia coli inactivation and oxytetracycline hydrochloride degradation by a Z-scheme silver iodide decorated bismuth vanadate nanocomposite under visible light irradiation.

Novel Z-scheme AgI/BiVO4 photocatalysts were fabricated by a chemical deposition-precipitation approach. The photocatalytic activities of the obtained catalysts were evaluated by disinfection of Escherichia coli (E. coli) and degradation of oxytetracycline hydrochloride (OTC-HCl) under visible-light irradiation. The BA3 (contained 9.09% of AgI) exhibited the highest photocatalytic activity and maintained good stability. It could completely inactivate 7.0×107 CFU/mL of E. coli in 50 min and degrade 80% of OTC-HCl in 60 min. The enhanced photocatalytic activity of AgI/BiVO4 composites could be ascribed to the lower recombination rate of electron-hole pairs. Meanwhile, radical trapping experiments revealed that the superoxide radical (O2-) and holes (h+) were the dominant reactive species in photo-disinfection process. Furthermore, the effects of bacterial initial concentration and inorganic anions were also investigated to optimize the photocatalyst for practical application. This study will give a new insight to construct the effective Z-scheme system for bacterial inactivation and organic pollutants degradation.

Novel p-n heterojunction BiOI/CeO2 photocatalyst for wider spectrum visible-light photocatalytic degradation of refractory pollutants.

Recently, visible-light-driven photocatalysts have been widely used in environmental pollutant remediation. In the present study, BiOI/CeO2 p-n junction photocatalysts were successfully fabricated using a facile in situ chemical bath method. The BiOI/CeO2 p-n junction photocatalysts exhibited excellent photoactivity for the decomposition of the refractory pollutant bisphenol A (BPA) and methylene orange (MO) under visible light illumination. The sample with a 1 : 1 mole ratio of BiOI : CeO2 possessed the highest photocatalytic performance out of all of the as-obtained catalysts. Mott-Schottky plots indicated that p-n junctions were successfully constructed between BiOI and CeO2. The optical and electrical properties of the materials demonstrate that the introduction of BiOI can broaden the visible-light absorption region of CeO2, and the transfer rate of the electron-hole pairs dramatically improves through forming a p-n junction. Furthermore, the BPA degradation efficiency exhibited excellent photostability after four consecutive cycles. These features show that the BiOI/CeO2 p-n junction has great application potential for refractory pollutant removal from wastewater.

AgI nanoparticles-decorated CeO(2) microsheets photocatalyst for the degradation of organic dye and tetracycline under visible-light irradiation.

In this paper, CeO2 microplates were synthesized by a sol-gel auto-combustion method. AgI nanoparticles (NPs) were then deposited onto the surface of CeO2 via a facile deposition-precipitation method. The as-prepared AgI/CeO2 samples were characterized by various analytical techniques. The composites exhibited superior photocatalytic activities for the organic dyes (RhB) and the refractory pollutant (tetracycline (TC), a typical antibiotic) degradation under visible light irradiation. The CA-19.03 sample exhibited the highest photocatalytic activity. The enhanced photocatalytic performance could be ascribed to the improved separation of photogenerated charge carriers due to well-matched band structure.