Degradation Rate Constants Research Articles

Design and fabrication of graphitic carbon nitride incorporated nickel selenide hybrid composite for effective degradation of organic pollutants under UV and natural sunlight irradiations

Addressing the challenge of developing a visible-light-driven photocatalyst with robust redox capabilities for organic pollutant degradation in environmental remediation, this study presents a novel hybrid composite. The composite was synthesized using g-C3N4 and NiSe2 through an ultrasonication-assisted hydrothermal method. Notably, the energy gap of this hybrid composite decreased from 2.72 to 2.30 eV as the g-C3N4 concentration ranged from 0 wt% to 30 wt%, as per the Kubelka–Munk theory. The surface area of the hybrid composite stood out at 31.2 m2/g, surpassing pristine NiSe2 (18.9 m2/g) and g-C3N4 (15.2 m2/g), as confirmed by BET analysis. The photocatalytic prowess of NiSe2/g-C3N4 composites was systematically investigated for the degradation of Reactive Blue 5 (RB 5) and Reactive Violet 5 (RV 5). Notably, the compositions with 30 % g-C3N4 incorporated into NiSe2 exhibited the highest degradation rates (86.4 % for RB 5 and 89.4 % for RV 5) and rate constants (0.0093 min−1 for RB 5 and 0.0095 min−1 for RV 5) during the degradation processes. Furthermore, the incorporation of g-C3N4 into NiSe2 not only elevated the surface area but also improved the separation rate of photogenerated electrons and holes. This enhancement significantly enhanced the visible-light-driven photodegradation performance of RB 5 and RV 5. The study also proposes a mechanism to explain the impact of graphitic carbon nitride concentration on photocatalytic performance. This research contributes to the development of advanced photocatalysts for eco-friendly pollutant degradation and provides insights into their composition-performance relationships.

Degradation kinetics of medium chain length Polyhydroxyalkanoate degrading enzyme: a quartz crystal microbalance study.

This study investigates the enzymatic degradation processes of different classes of polyhydroxyalkanoates (PHAs), a group of biopolymers naturally synthesized by various microorganisms. Medium chain length PHAs (mcl-PHAs) are distinguished biopolymers due to their biodegradability and diverse material properties. Using quartz crystal microbalance measurements as a valuable tool for accurate real-time monitoring of the enzymatic degradation process, the research provides detailed kinetic data, describing the interaction between enzymes and substrates during the enzymatic degradation process. Thin films of poly-3-hydroxybutyrate (PHB) and polyhydroxyoctanoate copolymer (PHO), containing molar fractions of about 84% 3-hydroxyoctanoate and 16% 3-hydroxyhexanoate, were exposed to scl-depolymerases from Pseudomonas lemoignei LMG 2207 and recombinant mcl-depolymerase produced in Escherichia coli DH5α harboring the plasmid pMAD8, respectively. Analyses based on a heterogeneous kinetic model for the polymer degradation indicated a six-fold stronger adsorption equilibrium constant of mcl-depolymerase to PHO. Conversely, the degradation rate constant was approximately twice as high for scl-depolymerases acting on PHB. Finally, the study highlights the differences in enzyme-substrate interactions and degradation mechanisms between the investigated scl- and mcl-PHAs.

Insight into the humic acid/antibiotic complexation for boosting tetracycline degradation by heterogeneous persulfate activation

Little attention has been paid to the degradation of antibiotics in their bound states, although numerous ionizable organic micro-pollutants possessed a strong tendency towards complexing with natural organic matters (NOM) in aquatic ecosystems. This study systematically investigated the degradation kinetics of tetracycline (TCH) bound with humic acid (HA) versus free TCH in heterogeneous persulfate activation system. Contrary to the homogeneous UV/PS oxidation processes documented, the complexation with HA promoted the removal of TCH due to the adsorption behavior of TCH on the heterogeneous catalyst. The results displayed that higher first-order rate constants of HA-bound TCH degradation (up to 3.8 folds) were obtained compared to free TCH at varying TCH and HA concentrations. The presence of ionic strength, alkalinity and hardness had an inhibitory effect on the degradation of bound TCH, and the effect of pH was more significant due to the change of electrostatic complexation of TCH/HA. Differential absorbance spectra further identified that the degradation sensitivity followed the order of bound TCH ＞ free TCH in TCH/HA mixed systems. In addition, the enhanced interfacial electron transfer that played a dominant role in TCH oxidation may be responsible for the efficient removal of TCH in the bound state. Results of this study provide new insights into the NOM/antibiotics complexation for boosting the antibiotics degradation in heterogeneous catalysis.

Construction of double 3D flower-like CoWO4/(1T/2H)-MoS2 Z-scheme heterojunctions with S defects for enhanced visible light-driven removal of gatifloxacin hydrochloride

Pollution resulting from antibiotics is a widespread problem, so it is crucial to provide an effective treatment method to reduce antibiotics from wastewater. In this study, to enhance the photocatalytic degradation of gatifloxacin hydrochloride (GAT-HCl) under visible light over MoS2, CoWO4 coupling and S defects were used to co-modify MoS2 to obtain CoWO4/1 T @ 2 H-MoS2 (CM) heterojunction catalyst. The prepared CM exhibited enhanced photocatalytic GAT-HCl degradation efficiency and could degrade approximately 91.6% of GAT-HCl in 50 min with a degradation rate constant of 0.0319 min−1, which was 11.39 and 12.76 times higher than that of pure MoS2 (0.0028 min−1) and CoWO4 (0.0025 min−1), respectively. The boosted GAT-HCl degradation over CM was attributed to the fact that CM could expose more exfoliation defects, trap photogenerated holes, promote the rapid separation and transfer of photogenerated carriers, release more active substances such as ⋅O2–, and enhance the interaction between the antibiotic and the active substances, which in turn facilitated the oxidative mineralization of GAT-HCl. CM has good reusability and the mechanism of enhanced photocatalytic degradation of GAT-HCl was proposed. This study provides a new strategy for the rational design of high-performance photocatalysts for water pollution remediation.

Degradation of atrazine by electro-peroxone enhanced by Fe and N co-doped carbon nanotubes with simultaneous catalysis of H2O2 and O3

Fe and N co-doped carbon nanotubes (Fe-N-CNT) was synthesized and attempted as efficient heterogeneous catalysts for simultaneous catalysis of H2O2 and O3 to improve electro-peroxone (Fe-N-CNT/EP) process efficiency for atrazine (ATZ) degradation. The removal and mineralization of ATZ was significantly enhanced, obtaining the degradation rate constant (k) by Fe-N-CNT/EP (0.23 min−1) about two times that of EP (0.12 min−1) owing to the formation of Fe0 and Fe-N coordination in Fe-N-CNT catalyst for co-catalysis of H2O2 and O3. The important factors such as applied current and ozone concentration were investigated, demonstrating that the optimized performance could be achieved at current of 30 mA and ozone concentration of 55 mg L−1. The oxidation capacity of Fe-N-CNT/EP maintained stably under wide pH range of 3∼7, obtaining the degradation rate constant 1.23–1.92 times that of EP and overcoming the defect of EP at acidic and neutral conditions. Capture experiments and electron paramagnetic resonance (EPR) experiments verified that .OH, generated by accelerating decomposition of H2O2/O3 and peroxone reaction, was the dominant active specie in Fe-N-CNT/EP. Besides, Fe-N-CNT showed high catalytic activity and good stability during six cycles. This work provides an efficient activator for enhanced EP process, exhibiting a promising prospect for water and wastewater purification.

Decoration of Ag/Bi nanoparticles over brown TiO2-x/AgBiO3 nanocomposites: QDs-sized photocatalysts for impressive mitigation of water pollutants

Heterogeneous photocatalysis is a hot-spot research field for energy conversion and water detoxification. One of the most important challenges of photocatalysis is the designing and development of efficacious visible-light-triggered photocatalysts. In this regard, perovskite AgBiO3 and Ag/Bi elemental nanoparticles were decorated on brown TiO2−x via a facile procedure. Electron microscopy, XPS, and XRD studies provided strong evidence about developing TiO2−x/Ag/AgBiO3/Bi photocatalysts with quantum dot size of about 5.5 nm, and intimate contact among the counterparts. The TiO2−x/Ag/AgBiO3/Bi photocatalysts displayed boosted ability in the detoxification of tetracycline (TC), amoxicillin (AMX), fuchsine (FS), and methylene orange (MO) pollutants. The degradation rate constants of TC, AMX, FS, and MO over the optimum TiO2−x/Ag/AgBiO3/Bi photocatalyst were 25.9, 3.40, 5.70, and 1.92 folds greater than TiO2−x and 20.3, 12.3, 6.77, and 2.33 times larger than Ag/AgBiO3/Bi, respectively. Photoluminescence spectroscopy, EIS experiments, and Bode plots showed accelerated charge transfer and significant reduction of charges recombination within TiO2−x/Ag/AgBiO3/Bi nanocomposites. The recycling studies showed that the plasmonic photocatalyst retained the most activity after four times of utilization. Ultimately, an s-scheme charges segregation route was suggested for the boosted activity of the plasmonic TiO2−x/Ag/AgBiO3/Bi photocatalysts.

Leaf extract of Cimbopogan citratus supported CuO/ZnO nanocomposite and their applications in photocatalytic and antibacterial activities

We have focused on the green synthesis of copper oxide nanoparticles (CuONPs) and zinc oxide nanoparticles (ZnONPs) and CuO coated with ZnO nanocomposite (CuO/ZnO) by using leaf extract of Cimpobogan citrates (CC) as reducing and stabilizing agent. Copper sulfate pentahydrate (CuSO4.5H2O) and zinc acetate dihydrate (Zn(CH3COO)2.2H2O) are the forerunners in the hydrothermal synthesis. The prepared ZnONPs, CuONPs and CuO/ZnO nanocomposite were characterized using various instrument techniques such as Fourier Transform-Infrared spectroscopy (FT-IR), UV-visible spectroscopy (UV-Vis), X-ray diffraction pattern (XRD), Scanning electron microscope (SEM), Energy dispersive X-ray analysis (EDAX) and High Resolution-Transmission Electron microscope (HR-TEM). The results showed that the average size of CuO/ZnO nanocomposite was 20-50 nm. The Tauc plot of CuO/ZnO nanocomposite shows low band gap (1.56ev). Under visible light illumination, methylene blue (MB) was degraded photocatalytically using ZnONPs, CuONPs and CuO/ZnO nanocomposite which was then examined using UV-visible spectroscopy. In comparison to ZnONPs (65%) and CuONPs (80%), CuO/ZnO nanocomposite showed superior photocatalytic activity for the breakdown of MB with a high percentage degradation efficiency (85%). The photocatalytic degradation rate constant was evaluated by using a pseudo-first order kinetic equation. Additionally, the agar disc diffusion method was used to examine the antibacterial activity against two bacterial strains (Escherichia coli and Staphylococcus aureus) and a sizable zone of inhibition against the bacterial strains was found.

Photocatalysis of silicon nanowires decorated with metallic nanoparticles and graphene oxide under different light intensities

This work shows silicon nanowires (SiNWs), decorated with different nanoparticles, as a photocatalytic material under different lighting conditions. In this system, the comparison between different materials and the influence of light intensity on their performances are studied. On the other hand, the synthesis of SiNWs was done by a metal-assisted chemical etching. The decoration with nanoparticles of copper CuNPs and cuprous oxide CuO2NPs was conducted with the electroless technique. Graphene oxide (GO) lamellar particles passing through an atmospheric pressure plasma (APPJ) were instantaneously ionized losing OH radicals and connecting them into a continuous coating around the SiNWs nanostructures. Such a layer with a large contact area among SiNWs/GO/Cu/CuO2 was obtained with a small thickness of about 10–20 nm. This is proposed to allow and increase charge carrier transference to the aqueous solution for redox reactions to degrade the dye molecules. Through statistical analysis, we compared the percentages of the decrease in methyl orange concentration used to measure the photocatalytic performance. SiNWs – CuNPs surfaces, in combination with high-intensity light, exhibit higher degradation percentages and rate constants. The graphene oxide coatings were deposited on monocrystalline silicon wafers and silicon nanowires, constituting a semiconductor-semiconductor heterojunction. This is an innovation proposed in this work that could lead to the fabrication of semiconductor heterojunctions with Z-scheme complementarity.

Cu Distribution Pattern Controlled Active Species Generation and Sulfamethoxazole Degradation Routes in a Peroxymonosulfate System

The distribution pattern of metals as active centers on a substrate can influence the peroxymonosulfate (PMS) activation and contaminants degradation. Herein, atomic layer deposition is applied to prepare Cu single atom (SA-Cu), cluster (C-Cu), and film (F-Cu) decorated MXene catalysts by regulating the number of deposition cycles. In comparison with SA-Cu-MXene (adsorption energy (Eads) = −4.236 eV) and F-Cu-MXene (Eads = −3.548 eV), PMS is shown to adsorb preferably on the C-Cu-MXene surface for activation (Eads = −5.435 eV), realizing higher utilization efficiency. More SO4− are generated in C-Cu-MXene/PMS system with steady-state concentration and 1–3 orders of magnitude higher than those in the SA-Cu-MXene and F-Cu-MXene activated PMS systems. Particularly, the contribution of SO4− oxidation to sulfamethoxazole (SMX) degradation followed the order, C-Cu-MXene (97.3%) > SA-Cu-MXene (90.4%) > F-Cu-MXene (71.9%), realizing the larger SMX degradation rate in the C-Cu-MXene/PMS system with the degradation rate constants (k) at 0.0485 min−1. Additionally, SMX degradation routes in C-Cu-MXene/PMS system are found with fewer toxic intermediates. Through this work, we highlighted the importance of guided design of heterogeneous catalysts in the PMS system. Appropriate metal distribution patterns need to be selected according to the actual water treatment demand. Metal sites could be then fully utilized to produce specific active species to improve the utilization efficiency of the oxidants.

Curcumin-loaded oil body emulsions prepared by an ultrasonic and pH-driven method: Fundamental properties, stability, and digestion characteristics

In this study, oil bodies (OBs) loaded with curcumin (Cur) were successfully prepared via an ultrasonic and pH-driven method. Ultrasonic treatment significantly improved the encapsulation efficiency (EE) and loading capacity (LC) of Cur, producing OB particles with small size, uniform distribution, and high ζ-potential absolute values. When the ultrasonic power was 200 W, the EE, LC, and ζ-potential absolute value were the greatest (88.27 %, 0.044 %, and −25.71 mV, respectively), and the OBs possessed the highest yellowness, representing the best treatment result. The confocal laser scanning microscopy (CLSM) and cryo-scanning electron microscopy (cryo-SEM) results was also intuitionally shown that. Moreover, circular dichroism (CD) proved that ultrasonic treatment could unfold the surface protein structure, further enhancing the stability. Therefore, the cream index (CI), peroxide value (POV), and thiobarbituric acid reactive substances (TBARS) were the lowest when the ultrasonic power was 200 W. In this case, the Cur loaded in OBs was well protected against hostile conditions, evidenced by the highest Cur retention rate and the lowest degradation rate constant. Finally, the in vitro gastrointestinal digestion simulation results showed that the ultrasonic treatment effectively increased the release of FFA, bioaccessibility, and stability of Cur, especially when the ultrasonic power was 200 W. This research offers a new OB-based delivery system to stabilize, deliver, and protect Cur for food processing.

Overlooked role of void-nanoconfined effect in emerging pollutant degradation: Modulating the electronic structure of active sites to accelerate catalytic oxidation

The efficient removal of emerging pollutant from water is the ultimate frontiers of advanced oxidation processes (AOPs), yet it is challenging to obtain higher catalytic activity and oxidation rate. Herein, a sustainable solution was proposed by optimizing the curvature of confined structure to modulate the electronic state of the active sites in nanochannels for improving the catalytic activity. In addition, the confined effect can enhance the oxidation rate by shorting the mass transfer of active species and pollutants. A void-nanoconfined nanoreactor was prepared by loading Fe2O3 into the nanochannels (<5 nm) of the hollow carbon sphere. An enhancement of 3 orders of magnitude was obtained in the degradation rate constant of void-nanoconfined catalytic system toward sulfamethoxazole (SMX) (6.25 min−1) compared with the non-confined system. The kinetics enhancement was attributed to the larger electron potential difference between the outer and inner nanochannel caused by the curvature increase of carbon sphere, accelerating the electron transfer, so that the energy barrier of SMX degradation reaction was reduced by 31 kcal/mol with the assistance of confinement energy. Importantly, the NC-IN/PDS system exhibited outstanding removal efficiency for the actual river water using a continuous flow reactor. This work provides a new insight into designing an efficient and stable catalytic nanoreactor, enriching the domain of advanced wastewater treatment strategies.

Cost-effective efficient materials for dye degradation using non-aqueous sol-gel route.

In the present studies, the synthesis of pure ZnO nanoparticles and Mg and S-doped ZnO particles were carried out using a non-aqueous sol-gel method. The synthesized nanoparticles (NPs) are characterized using XRD, FESEM, EDX, FTIR, UV-Vis-DRS, XPS, PL, and BET surface area analysis. X-ray diffraction (XRD) techniques were used to examine the crystallization of ZnO, Mg-ZnO, and S-ZnO samples. The Mg-ZnO and S-ZnO samples exhibit significant c-axis compression and smaller crystallite sizes as compared to undoped ZnO. The optical band gap of Mg-ZnO and S-ZnO NPs were found to be 2.93eV and 2.32eV, respectively, which are lower than that of ZnO NPs (3.05eV). The S-doped ZnO resulted in the homogenous distribution of sulfur ions in the ZnO lattice crystal. XPS analysis revealed that the doped S element was mostly S4+ and S6+. A systematic evaluation has been conducted to assess the influence of several operational parameters, including doped/undoped stoichiometry, solution pH, catalyst dosage, and radical trapping experiment, on the photocatalytic degradation of Rhodamine 6G (Rh 6G) dye. Furthermore, we investigated the photocatalytic degradation activity of ZnO, Mg-ZnO, and S-ZnO samples with aquoues solution of 5ppm Rhodamine 6G (Rh 6G) at room temperature. Results indicated that pure ZnO nanoparticles have the highest photocatalytic degradation rate constant (0.00344min-1), compared to the samples Mg-ZnO (0.00104min-1) and S-ZnO (0.00108min-1) with Rh 6G dye in presence of visible light emitting diode (Vis-LED) source at room temperature. The enhanced visible light photocatalytic activities of pure ZnO NPs were attributed to their superior surface properties (18.30 m2/g) and effective electron-hole separation.

Modified carbon nitride incorporating Keggin-type potassium phosphotungstate enhances photocatalytic degradation of imidacloprid under visible light

Despite the significant research efforts that have been dedicated to the applications of graphite carbon nitride (g-C3N4) in the flied of photocatalysis, there is still a significant challenge in terms of its efficiency under visible light conditions. In this study, potassium phosphotungstate (KPW), phosphotungstic acid (HPW), and ammonium phosphotungstate (NHPW) were used to synthesize composite photocatalysts with g-C3N4 by a post-impregnation activation method, and the synthesized g-C3N4/KPW-0.2 exhibited excellent photocatalytic performance. When illuminated by visible light for a duration of 3 h, g-C3N4/KPW-0.2 demonstrated an outstanding degradation rate of 91.72 % for the imidacloprid, with a photocatalytic degradation rate constant of 0.0134 min−1, which is 2.8 times higher than that of g-C3N4. Notably, g-C3N4/KPW-0.2 shows better performance compared to g-C3N4/HPW-0.5 and g-C3N4/NHPW-1.2 prepared using the same procedure. Experimental results have established that KPW forms a strong interaction with g-C3N4, facilitating the migration of electrons, the KPW acting as an electron mediator, enabling increased absorption of visible light, and reducing electron-hole recombination. These synergistic effects significantly improve the photocatalytic activity of g-C3N4. Additionally, g-C3N4/KPW-0.2 showed excellent stability, retaining its high photocatalytic activity even after five cycles of use. From the results of electron spin resonance measurements and radical quenching experiments, photogenerated holes (h+) and superoxide radicals (·O2−) are the keys to the photocatalytic degradation process. The work presented here provides valuable insights into the effective compound of POMs with g-C3N4 in photocatalytic degradation technology. This research can inspire future applications of photocatalytic technology in the treatment of chemical substances in wastewater.

Built-in electric field boosted exciton dissociation in sulfur doped BiOCl with abundant oxygen vacancies for transforming the pathway of molecular oxygen activation

The reactive oxygen species (ROS) generated by photoinduced molecular oxygen (O2) activation has attracted great attention in environmental remediation and pollution control. Herein, we establish a facile sulfur doping strategy that promotes the activation of molecular oxygen over BiOCl for rapid and continuous degradation of organic pollutants. In this work, we demonstrate that the significantly enhanced built-in electric field (BIEF) induced by the heterogeneous introduction of S atoms not only multiplies the electron concentration in the BiOCl matrix, but also accelerates the rapid separation/transfer of charge carriers and inhibits recombination. Driven by this, the exciton behavior in the BOC undergoes a transformation. The electrons generated through exciton dissociation activate the adsorbed O2 on the surface into superoxide radicals (•O2–). Benefited from the superior O2 activation efficiency, the degradation rate constant of ciprofloxacin (CIP) the fabricated S-doped BiOCl increased by 8.8 times, under visible light. This work proposes a strategy to promote the photocatalytic O2 activation via tuning BIEF and manipulating excitonic effects, which affords new perspective for understanding the reaction mechanisms related to charge transfer in photocatalytic systems.

P/S-g-C3N4 nanosheet composites with enhanced photocatalytic water splitting and dye degradation

The band gap and photo- and electro-chemical activities of graphic carbon nitride (g-C3N4) depended strongly on their components. In this paper, P-g-C3N4/S-g-C3N4 (PCN/SCN) and S-g-C3N4/P-g-C3N4 (SCN/PCN) composite nanosheets heterostructures were created using P-doped and S-doped g-C3N4 nanosheets as seeds to study the effect of compositions on photo- and electro-chemical properties. Thermal polymerization temperature and the ratios of S- and P-doped g-C3N4 components were adjusted to get optimized conditions. The photo-degradation kinetics of Rhodamine B (Rh B) and photocatalytic H2 generation were used to discuss the relationship of photocatalytic performance and composition of photocatalysts. The degradation of Rh B in visible light region was finished using sample 600MCNS@ 720 DCNP15% within 15 min with a degradation rate constant of 0.197, which was 2.3 and 3.9 times compared with S- and P-doped g-C3N4 nanosheets, respectively. Namely, the H2 generation rate of sample 600MCNS@ 720 DCNP15% was 1851.9 µmolg−1h−1, which is 6.6 and 5.9 times higher than those of S- and P-doped g-C3N4 nanosheets, respectively. Interestingly, these P/S-g-C3N4 composite heterojunctions revealed improved electro-chemical performance. In the case of a current density of 1 mA cm−2, the overpotential of ample 600MCNP@ 720 DCNS20% was 333 mV and a Tafel slope was 155.33 mV dec−1 in KOH solutions. This result supplied an efficient approach to improve the photocatalytic performance of g-C3N4 based materials.

Remarkably fast and reusable photocatalysis by UV annealed Cu2O–SnO2 p−n heterojunction

Powdered micro- or nano-particles photocatalyst has separation and recovery challenges, which may create a second pollution to environment and harmful to animals. To address those issues, SnO2, Cu2O and Cu2O–SnO2 p-n heterojunction thin films are formed on glass substrates using efficient co-sputtering method that is commonly employed for large-area high-definition display panel. Using first-order kinetics, 100 °C ultraviolet (UV) annealed Cu2O–SnO2 p-n heterojunction shows the superb fast degradation rate constant of 0.21 and 0.16 min−1 for methylene blue (MB) and methyl orange (MO) organic dyes, respectively, as photogenerated electron-hole pairs is increased. Record best degradation rate constants of 0.19 and 0.11 min−1 for respective MB and MO are still achieved even after four repeated cycles. The 100 °C UV annealed Cu2O–SnO2 film catalyst displays greater degradation efficiency in both dyes, reaching 100% degradation at room temperature after 30 and 35 min of illumination for MB and MO respectively. The scavenger experiments show that hydroxyl (·OH) and superoxide radicals (·O2−) are the major active species in the degradation of dye. The 100 °C UV annealed Cu2O–SnO2 film catalyst showed stability as well as reusability towards the dye degradation. As a result, the present work delivers an effective way to enhance the photocatalytic performance and also an easy recovery of the catalyst, which can be explored for various emerging pollutants.

Self-assembled B-doped flower-like graphitic carbon nitride with high specific surface area for enhanced photocatalytic performance

Graphitic carbon nitride (g-C3N4) is a promising nonmetallic photocatalyst. In this manuscript, B-doped 3D flower-like g-C3N4 mesoporous nanospheres (BMNS) were successfully prepared by self-assembly method. The doping of B element promotes the internal growth of hollow flower-like g-C3N4 without changing the surface roughness structure, resulting in a porous floc structure, which enhances the light absorption and light reflection ability, thereby improving the light utilization rate. In addition, B element provides lower band gap, which stimulates the carrier movement and increases the activity of photogenerated carriers. The photocatalytic mechanism and process of BMNS were investigated in depth by structural characterization and performance testing. BMNS-10 % shows good degradation for four different pollutants, among which the degradation effect on Rhodamine B (RhB) reaches 97 % in 30 min. The apparent rate constant of RhB degradation by BMNS-10 % is 0.125 min−1, which is 46 times faster compared to bulk g-C3N4 (BCN). And the photocatalyst also exhibits excellent H2O2 production rate under visible light. Under λ > 420 nm, the H2O2 yield of BMNS-10 % (779.9 μM) in 1 h is 15.9 times higher than that of BCN (48.98 μM). Finally, the photocatalytic mechanism is proposed from the results of free radical trapping experiments.

Material properties and durability of 19th–20th century Tibetan manuscripts

Most currently available research into Tibetan paper focuses on the earliest books from an archaeological perspective. On the other hand, scientific studies of the 19th−20th century Tibetan paper are largely missing, specifically with respect to material properties and paper permanence. To explore these, both conventional and modified methods were applied using reference historic material collection. Material properties such as fibre morphology, paper pH, degree of polymerisation (DP), water and ash contents were investigated. The measurement methods for starch and protein content were explored—and we report on a quantification method for the determination of starch content in paper. The degradation behaviour of Tibetan paper was studied using accelerated degradation experiments at two sets of conditions (80 ˚C, 65% RH and 60 ˚C, 80% RH) for up to 84 days in order to explore the applicability of existing dose-response functions. The results demonstrate that examined 19th−20th century papers used in Tibetan books, were prepared using diverse fibres, similar to traditional Chinese paper. Most of paper sheets presented laminated structures, where starch was used as the predominant glue. The layers within one paper sheet are identical, as evidenced by similar pH and DP values among layers in one sheet. The studied collection of papers tends to have similar properties to modern Chinese paper since most of both types of papers present pH 6.5–8 and DP 1000–2000. The accelerated degradation experiment shows that papers used as writing support in Tibetan books follows the same principle of degradation as western paper has demonstrated, i.e., the rate constants of degradation depend on paper pH, temperature, and relative humidity of the environment. This research expands our understanding of this collection and inform preventive conservation of modern Tibetan manuscripts.

Hydrodynamic cavitation-enhanced activation of sodium percarbonate for estrogen removal

Abstract The present paper investigated the potential of hydrodynamic cavitation (HC) as an effective tool for activating sodium percarbonate (SPC). The method's efficiency was demonstrated by effectively removing estrogens, which are pollutants that have adverse impacts on aquatic ecosystems. The effects of the SPC concentration, temperature of solution, and cavitation time were evaluated. After SPC/HC treatment, the removal of estrogens was monitored by liquid chromatography-tandem mass spectrometry (LC -MS/MS). Already after 4 s of treatment and 24 h of reaction time, more than 97% of estrogens (initial concentration of 300 ng/L) were removed. The effect of post-treatment time is not considered in several papers, even though it seems to be crucial and is discussed here. The results were supported by the values of degradation rate constants, which fit the pseudo-first-order kinetic model. We also verified that HC alone was not effective for estrogen removal under the selected conditions. The sustainability of the SPC/HC system was evaluated based on electric energy per order calculation. The combination of SPC and HC is a promising approach for rapidly degrading micropollutants such as estrogenic compounds without the need for additional technological steps, such as pH or temperature adjustment.

Fabrication of Ti3+/N/B-TiO2@NGQDs composite photocatalyst with significantly enhanced visible light catalytic activity

A two-step hydrothermal process was used to successfully create Ti3+, N, and B co-doped TiO2 modified with nitrogen doped graphene quantum dots (Ti3+/N/B-TiO2@NGQDs (TNBTN)) composite photocatalyst for photodegradation of bisphenol A (BPA) and methyl orange (MO) under visible-light illumination. The prepared TNBTN composite demonstrated significantly enhanced visible light catalytic performance. Especially, the apparent rate constant of BPA degradation with TNBTN was approximately 56.9 times that of pure TiO2, which was attributed to broader visible light absorbance and faster transmission and separation of photoinduced charge. In addition, the mechanism of BPA and MO degradation with TNBTN was distinct.