Enhanced photocatalytic degradation of N-doped TiO2-SiO2 composite for degradation of phenol under simulated natural light assisted by S2O8 2- anions

In recent years, TiO2 photocatalyst has been studied to increase the overall efficiency in the degradation of organic pollutants in water. Several solutions have been proposed such as non-metal doping to reduce a high band gap energy (3.2 eV) of TiO2 to increase absorption in the visible region and synthesis of composite photocatalyst to improve the efficiency of electron-hole separation and the specific surface area. Herein, the N-doped TiO2-SiO2 photocatalysts were investigated. Powder samples with three molar ratios of TiO2/SiO2 (95/5-TS5, 85/15-TS15, 75/25-TS25) were successfully synthesized, characterized, and estimated their photocatalytic activity toward the phenol degradation (initial concentration to be 10 ppm) under simulated natural light. N-doped TiO2-SiO2 samples were prepared with molar ratios of N to designed TiO2 to be 3%, 5%, 7%. The 3N-TS5 photocatalyst (3 mol % N doped TS5) shows the highest phenol efficiency degradation, to be 95% in 4 h, photocatalytic degradation rate constant of 1.02}10−2 min−1 due to its narrower band gap energy (3.05 eV). Furthermore, the addition of S2O8 2- anions at a concentration of 1 mM is enhanced degradation efficiency and degradation rate. And phenol is almost completely degraded within 60 min and achieved a degradation rate constant of 7.65*10−2 min−1, 7.5 times higher than that without the presence of S2O8 2- anions. This attractive result is attributed to the generation of sulfate radical (SO4 *“) during photolysis. Finally, N-doped TiO2-SiO2 photocatalyst assisted by S2O8 2- anions shows potential to design and improve manufacturing processes to obtain photoreactors for organic degradation from waste-water under natural light degradation.

Long term conservation of DNA at ambient temperature. Implications for DNA data storage

DNA conservation is central to many applications. This leads to an ever-increasing number of samples which are more and more difficult and costly to store or transport. A way to alleviate this problem is to develop procedures for storing samples at room temperature while maintaining their stability. A variety of commercial systems have been proposed but they fail to completely protect DNA from deleterious factors, mainly water. On the other side, Imagene company has developed a procedure for long-term conservation of biospecimen at room temperature based on the confinement of the samples under an anhydrous and anoxic atmosphere maintained inside hermetic capsules. The procedure has been validated by us and others for purified RNA, and for DNA in buffy coat or white blood cells lysates, but a precise determination of purified DNA stability is still lacking. We used the Arrhenius law to determine the DNA degradation rate at room temperature. We found that extrapolation to 25°C gave a degradation rate constant equivalent to about 1 cut/century/100 000 nucleotides, a stability several orders of magnitude larger than the current commercialized processes. Such a stability is fundamental for many applications such as the preservation of very large DNA molecules (particularly interesting in the context of genome sequencing) or oligonucleotides for DNA data storage. Capsules are also well suited for this latter application because of their high capacity. One can calculate that the 64 zettabytes of data produced in 2020 could be stored, standalone, for centuries, in about 20 kg of capsules.

Degradation of Chloramphenicol Using UV-LED Based Advanced Oxidation Processes: Kinetics, Mechanisms, and Enhanced Formation of Disinfection By-Products

As an emerging light source, ultraviolet light emitting diodes (UV-LEDs) are adopted to overcome the shortcomings of the conventional mercury lamp, such as mercury pollution. The degradation of chloramphenicol (CAP) using three UV-LED-based advanced oxidation processes (AOPs)—UV-LED/persulfate (UV-LED/PS), UV-LED/peroxymonosulfate (UV-LED/PMS) and UV-LED/chlorine—was investigated. Results indicate that CAP can be more effectively degraded by the hybrid processes when compared to UV irradiation and oxidants alone. Degradation of CAP using the three UV-LED-based AOPs followed pseudo-first-order kinetics. The degradation rate constants (kobs) for UV-LED/PS, UV-LED/PMS, and UV-LED/chlorine were 0.0522, 0.0437 and 0.0523 min−1, and the CAP removal rates 99%, 98.1% and 96.3%, respectively. The degradation rate constant (kobs) increased with increasing oxidant dosage for UV-LED/chlorine, whereas overdosing reduced CAP degradation using UV-LED/PS and UV-LED/PMS. Ultraviolet wavelength influenced degradation efficiency of the UV-LED based AOPs with maximum CAP degradation observed at a wavelength of 280 nm. The application of UV-LED enhanced the formation DBPs during subsequent chlorination. uUV-LED/PMS produced more disinfection by-products than UV-LED/PS. Compared to UV-LED, UV-LED/PS reduced the formation of dichloroacetonitrile and trichloronitromethane during chlorination owing to its capacity to degrade the nitro group in CAP. The intermediates dichloroacetamide, 4-nitrobenzoic acid, 4-nitrophenol were produced during the degradation of CAP using each of UV-LED, UV-LED/PS and UV-LED/chlorine. The present study provides further evidence supporting the application of UV-LED in AOPs.

Simple Fabrication of Visible Light-Responsive Bi-BiOBr/BiPO4 Heterostructure with Enhanced Photocatalytic Activity

A Bi-BiOBr/BiPO4 heterojunction structure was successfully synthesized via a two-step solvothermal method with ethylene glycol as a reducer. Little BiPO4 irregular polyhedrons and little metal Bi spherical nanoparticles were uniformly dispersed on the surface of BiOBr nanosheets with intimate contact and formed a heterojunction structure between BiPO4 and BiOBr. It was found that Bi-BiOBr/BiPO4 had a significant improvement in photocatalytic performance for RhB degradation compared to bare BiOBr and BiPO4. The photocatalytic degradation rate constant of 0.2-Bi/BiOBr/BiPO4 was 1.44 h-1, which was 3.8 times and 14.2 times more than that of bare BiOBr and BiPO4, respectively. This is attributed to the formation of a ternary heterojunction, which benefits the separation of photogenerated electron-hole pairs. Furthermore, with the introduction of metal Bi, the SPR effect of metal Bi can effectively improve the absorption ability of Bi-BiOBr/BiPO4 photocatalyst, resulting in enhanced photoactivity. In this work, the mechanism of photocatalytic degradation was studied by using the photochemical technique and the capture experiment of active species, and it was revealed that h+ and ⋅O2- played a major role in the photocatalytic process.

More Precise Control of the In Vitro Enzymatic Degradation via Ternary Self-Blending of High/Medium/Low Molecular Weight Poly(trimethylene carbonate)

To more precisely control the degradation rate of poly(trimethylene carbonate) (PTMC), self-blending films were prepared via the ternary self-blending of pure PTMC with a molecular weight of 334, 152, and 57 kg/mol. The in vitro enzymolysis degradation of the ternary self-blending films was performed in lipase solutions. The results showed that ternary self-blending could control the degradation of PTMC by adjusting the mass ratio of high/medium/low molecular weight PTMC in the composition, and the PTMC334/PTMC152/PTMC57 films with a mass ratio of 1/4/16 showed mass loss of 85.96% after seven weeks of degradation, while that of PTMC334/PTMC152/PTMC57 films with a mass ratio of 1/1/1 was 96.39%. The former and latter’s degradation rate constant was 13.263 and 23.981%/w, respectively, and the former presented better morphology stability than the latter. The strategy of ternary self-blending could simultaneously bestow PTMC with a lower degradation rate and good morphology stability, indicating that ternary self-blending is an efficient way to control the degradation performance of PTMC more precisely.

Photocatalytic degradation of tetracycline by Phosphorus-doped carbon nitride tube combined with peroxydisulfate under visible light irradiation

Photocatalysis has been regarded as a kind of environmentally friendly advanced oxidation process to eliminate pollutants. In this work, Phosphorus-doped carbon nitride tube (PCN) was synthesized via a hydrothermal calcination method and applied to degrade tetracycline (TC) through combing with peroxydisulfate (PDS) under visible light irradiation. Experimental results showed that the optimized catalysts PCN-5 exhibited superior degradation performance and reusability for TC degradation. 96.4% TC could be degraded for optimal PCN-5 with 0.3 g·L−1 catalysts and 1.0 g·L−1 PDS under visible light within 60 min. In addition, the degradation rate constant for TC of PCN + PDS + Vis system was still above 85% after five uses. Radical trapping experiment indicating that O2·− is the dominant radical for TC degradation. The findings of this work revealed the potential application of the PCN + PDS + Vis system toward degrading contaminants in wastewater.

Bio-mimetic synthesis of catalytically active nano-silver using Bos taurus (A-2) urine

Herein we have synthesized silver nanoparticles (Ag NPs) using liquid metabolic waste of Bos taurus (A-2 type) urine. Various bio-molecules present in cow urine, are effectively used to reduce silver (Ag) ions into silver nanoparticles in one step. This is bio-inspired electron transfer to Ag ion for the formation of base Ag metal and is fairly prompt and facile. These nanoparticles act as a positive catalyst for various organic transformation reactions. The structural, morphological, and optical properties of the as-synthesized Ag NPs are widely characterized by X-ray diffraction spectroscopy, ultraviolet–visible spectroscopy, scanning electron microscope, Fourier transmission infra-red spectroscopy, and atomic force microscopy. The as-synthesized bio-mimetic Ag NPs show potential activity for several reduction reactions of nitro groups. The Ag NPs were also used for degradation of hazardous dyes such as Methylene blue and Crystal violet with good degradation rate constant.

Polymer Flooding in Heterogeneous Heavy Oil Reservoirs: Experimental and Simulation Studies

Polymer flooding (PF) in heterogeneous heavy oil reservoirs is not only closely related to polymer degradation, but also to non-Newtonian flow. In this paper, both experimental and simulation methods are combined to investigate this type of flooding. Through experiments, the degradation of polymer, rheological properties of fluids, and flow of fluids in porous media were determined. Based on the experimental results, a novel mathematical model was established, and a new PF simulator was designed, validated, and further applied to study the effects of polymer degradation, polymer solution shear thinning, and non-Newtonian flow on PF in heterogeneous heavy oil reservoirs. These experimental results demonstrated that the polymer first-order static degradation rate constant was lower than the polymer first-order dynamic degradation rate constant; the polymer solution and heavy oil were non-Newtonian fluids, with shear thinning and Bingham fluid properties, respectively; and the heavy oil threshold pressure gradient (TPG) in low-permeability porous media was higher than that in high-permeability porous media. All comparison results showed that the designed simulator was highly accurate and reliable, and could well describe both polymer degradation and non-Newtonian flow, with special emphasis on the distinction between polymer static and dynamic degradation and heavy oil TPG. Furthermore, the simulation results verified that polymer degradation, polymer solution shear thinning, and heavy oil TPG all had negative effects on the efficiency of PF in heterogeneous heavy oil reservoirs.

Long term conservation of DNA at ambient temperature. Implications for DNA data storage

DNA conservation is central to many applications. This leads to an ever-increasing number of samples which are more and more difficult and costly to store or transport. A way to alleviate this problem is to develop procedures for storing samples at room temperature while maintaining their stability. A variety of commercial systems have been proposed but they fail to completely protect DNA from deleterious factors, mainly water. On the other side, Imagene company has developed a procedure for long-term conservation of biospecimen at room temperature based on the confinement of the samples under an anhydrous and anoxic atmosphere maintained inside hermetic capsules. The procedure has been validated by us and others for purified RNA, and DNA in buffy coat or white blood cells lysates, but a precise determination of purified DNA stability is still lacking. We used the Arrhenius law to determine the DNA degradation rate at room temperature. We found that extrapolation to 25 degree C gave a degradation rate constant equivalent to about 1 cut per century per 100000 nucleotides, a stability several orders of magnitude larger than the current commercialized processes. Such a stability is fundamental for many applications such as the preservation of very large DNA molecules (particularly interesting in the context of genome sequencing) or oligonucleotides for DNA data storage. Capsules are also well suited for this latter application because of their high capacity. One can calculate that the 64 zettabytes of data produced in 2020 could be stored, standalone, for centuries, in about 20 kg of capsules.

Self-Driven Pretreatment and Room-Temperature Storage of Water Samples for Virus Detection Using Enhanced Porous Superabsorbent Polymer (PSAP) Beads

The continuous emergence of infectious viral diseases has become a major threat to public health. To quantify viruses, proper handling of water samples is required to ensure the accuracy and reliability of the testing results. In this study, we develop enhanced porous superabsorbent polymer (PSAP) beads to pretreat and store water samples for virus detection. By applying PSAP beads to collect water samples, the viruses are captured and encapsulated inside the beads while undesired components are excluded. We have successfully demonstrated that the shelf life of the model virus can be effectively extended at room temperature (22°C) and elevated temperature (35°C). Both the infectivity level and genome abundance of the viruses are protected even in a complex medium like untreated wastewater. Under the tested conditions, the viral degradation rate constant can be reduced to more than 10 times using the PSAP beads. Therefore, the enhanced PSAP beads provide a low-cost and efficient sample pretreatment and storage method that is feasible and practicable for large-scale surveillance of viral pathogens in water samples.