Sequential UV Research Articles

Comparative effectiveness of sequential and synergistic (VUV/)UV and chlorine disinfection on DBPs and humic acid reduction

The widespread use of chlorine during disinfection has led to the problems of disinfection by-products (DBPs). Recently, the combination of ultraviolet (UV, 254 nm) and vacuum ultraviolet (VUV, 185 nm) with chlorine has been considered a promising strategy to mitigate the formation of DBPs. This study systematically evaluated the efficacy of six different disinfection methods in abating humic acid (HA), a common precursor of DBPs (UV-Chlorine, VUV/UV-Chlorine, Chlorine-UV, Chlorine-VUV/UV, UV/Chlorine, and VUV/UV/Chlorine). Under 40 mJ/cm2 UV fluence and 3 mg/L chlorine dose, the synergistic processes yielded DBP levels below 20 μg/L, whereas sequential disinfection resulted in DBP levels exceeding 100 μg/L. Additionally, there was no significant difference in the formation of DBPs between the two methods of chlorination followed by irradiation. However, for irradiation followed by chlorination, the addition of VUV led to an increase of 50 μg/L in trihalomethanes (THMs). As the irradiation time increased, the inclusion of VUV demonstrated enhanced control of DBP levels in the sequential disinfection process. Moreover, compared to UV/Chlorine, at 13 mg/L chlorine dose in VUV/UV/Chlorine process, the inclusion of VUV expedited the appearance of peak DBPs by two minutes and reduced the peak value by 25.6 %, but the DBP yield was 12.9 times higher than that at a chlorine dose of 3 mg/L. This study, comparing six combination disinfection methods, will provide deeper insights into precursor abatement and DBP control during drinking water disinfection.

DBP-FP change of biofilm in drinking water distribution system induced by sequential UV and chlorine disinfection: Effect of UV dose and influencing mechanism

The issue of biofilm-related disinfection byproducts (DBPs) in drinking water distribution system (DWDS) has garnered significant attention. This study sought to examine the changes in biofilm-originated halogenated DBP formation potential (biofilm DBP-FP) in simulated continuous-flow DWDSs subjected to sequential UV and chlorine disinfection (UV–Cl2) treatments with varying UV doses and to propose the underlying mechanism. The formation potential of trihalomethanes (THMs), haloacetic acids (HAAs), and the total organic halogen (TOX, X = Cl and Br) produced by biofilm were measured. Results showed that the biofilm TOCl-FP was at a minimum with a UV dose of 80 mJ/cm2, corresponding to the lowest amounts of protein and polysaccharides in the extracellular polymeric substances (EPS). Sphingobium, Methylobacterium, and Sphingomonas played a crucial role in protein and polysaccharide biosynthesis. Bacterial community composition characterization together with metabolic function analysis indicated that dominant bacteria varied and metabolic function shifted due to UV-Cl2 disinfection, with Alphaproteobacteria increasing in relative abundance and Bacteroidia showing the opposite trend with increasing UV doses. Correlation analysis suggested that the UV-Cl2 disinfection process led to changes in the water matrix, including organics, inorganics, bacteria, and components that provide environmental pressure for the biofilm. These changes ultimately influenced the properties of the biofilm EPS, which had a direct impact on biofilm DBP-FP.

Comparison of inactivation characteristics between Gram-positive and Gram-negative bacteria in water by synergistic UV and chlorine disinfection

Disinfection is essential in water and wastewater treatment process as a guarantee for microbial safety. This study systematically investigated: (i) the inactivation characteristics of bacteria widely existed in water, including Gram-negative bacteria (Escherichiacoli) and Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis spores), by sequential UV and chlorine disinfection processes (UV–Cl and Cl-UV), simultaneous UV and chlorine disinfection process (UV/Cl); and (ii) the disinfection mechanisms on different bacteria. The combination of UV and chlorine disinfection could inactive bacteria at lower doses, but showed no synergistic effect on E. coli. Contrarily, disinfection results indicated that UV/Cl performed an obvious synergistic effect on highly disinfectant-resistant bacteria (e.g. S. aureus and B. subtilis spores). Specifically, UV/Cl at the UV dose of 9 mJ/cm2 and chlorine dose of 2 mg-Cl/L could inactivate S. aureus completely. Moreover, the effectiveness of UV/Cl on the removal of indigenous bacteria in actual water conditions was also confirmed. In short, the study provides significant theoretical and practical implications for ensuring microbial safety during water treatment and use.

Structurally integrated asymmetric polymer electrolyte with stable Janus interface properties for high-voltage lithium metal batteries

Solid-state polymer electrolytes are outstanding candidates for next-generation lithium metal batteries in the realm of high specific energy densities, high safeties and tight contact with electrodes. However, their applications are still hindered by the limitations that no single polymer is electrochemically stable with the oxidizing high-voltage cathode and the highly reductive Li anode, simultaneously. Herein, a bilayer asymmetric polymer electrolyte (SL-SPE) without accessional interface resistance that using poly (ethylene glycol) diacrylate (PEGDA) as a “bridge” to connect the sulfonyl (OS = O)-contained oxidation-tolerated layer and polyether-derived reduction-tolerated layer (SPE), is proposed and synthesized by sequential two-step UV polymerizations. SL-SPE can provide widened electrochemical stability window up to 5 V, while simultaneously deploying a stable Janus interface property. Eventually, the superior high-voltage (4.4 V) cycling durability can be displayed in LiNi0.6Co0.2Mn0.2O2|SL-SPE|Li batteries. This finding provides a bran-new idea for designing multifunctional polymer electrolytes in the application of solid-state batteries.

Towards an enhanced nanocarbon crystallization from lignin

In this work, a new approach to the synthesis of lignin-derived nanocarbon crystals based on lignin depolymerization is proposed. The lignin chemical structure was modified through a controlled routine, which was based on sequential UV light irradiation, hydrothermal carbonization in autoclave, vacuum degassing, pyrolysis and mechanical exfoliation. In this way, we were able to obtain a lignin-based nanocarbon with a sp2-hybridized nanoporous framework structure with oxygenated functional groups attached to this structure. The used catalyst-free route resulted in high nanocarbon yields and turns out to be an eco-friendly strategy of a synthesis of low-cost carbon materials. The characterization of the lignin-derived nanocarbon was carried out using X-ray diffraction measurements, infrared, Raman and X-ray photoelectrons spectroscopies analyses. The nanocarbon materials' morphology was evaluated by scanning and transmission electron microscopy. The method of lignin's transformation developed in this work showed itself as a promising alternative for provision of large amounts of carbon-based materials for industrial applications. The proposed approach may be adapted to various biomass feedstocks with aromatic groups' content suitable for their high yield polycondensation. The achieved nanocarbon yield, when starting from a commercial purified lignin, varied between 50 wt% and 70 wt%.

Synergistic effects of UV and chlorine in bacterial inactivation for sustainable water reclamation and reuse

Disinfection is a necessity in water and wastewater treatment and reclamation. This study examined the inactivation of a disinfectant resistant but widely existed opportunistic pathogen in reclaimed water, Staphylococcus aureus (S. aureus), by sequential UV and chlorine disinfection or simultaneous UV and chlorine disinfection (UV/Cl). It was identified that UV/Cl greatly promoted the inactivation efficacy and inhibited photoreactivation of S. aureus by the generation of free radicals (i.e. OH and Cl), which reached a 7-log10 reduction at UV and chlorine doses of 18 mJ/cm2 and 2 mg-Cl/L, respectively. The changes of bacterial viability and morphology and the increase of extracellular ATP concentration confirmed the enhancement of cell membranes damages (>21.4 %) due to free radicals generated in UV/Cl process, which caused a dramatic reduction in metabolic activity and suppressed the photoreactivation. Furthermore, this study demonstrated that UV/Cl effectively removed heterotrophic plate count bacteria and aromatic organic fluorophores in reclaimed water samples. This study is of significant theoretical and applicable importance in guaranteeing safe microbial levels for water reclamation and reuse.

A Dipolar Cyclization/Fragmentation Strategy for the Catalytic Asymmetric Synthesis of Chiral Eight-Membered Lactams

A Dipolar Cyclization/Fragmentation Strategy for the Catalytic Asymmetric Synthesis of Chiral Eight-Membered Lactams

Dual-Encryption in a Shape-Memory Hydrogel with Tunable Fluorescence and Reconfigurable Architecture.

Materials capable of shape-morphing and/or fluorescence imaging have practical significances in the fields of anti-counterfeiting, information display, and information protection. However, it's challenging to realize these functions in hydrogels due to the poor mechanical properties and lack of tunable fluorescence. A tough hydrogel with good shape-memory ability and phototunable fluorescence is reported here, which affords reprogrammable shape designing and information encoding for dual-encryption. This hydrogel is prepared by incorporating donor-acceptor chromophore units into a poly(1-vinylimidazole-co-methacrylic acid) network, in which the dense intra- and interchain hydrogen bonds lead to desirable features including high stiffness, high toughness, and temperature-mediated shape-memory property. Additionally, the hydrogel shows photomediated tunable fluorescence through a unimer-to-dimer transformation of the chromophores. By combining photolithography and origami/kirigami designs, hydrogel sheets encoded with fluorescent patterns can deform into specific 3D configurations. The geometrically encrypted fluorescent information in the architected hydrogels is readable only after sequential shape recovery and UV light irradiation. As demonstrated by proof-of-concept experiments, both the fluorescent pattern and the 3D configuration are reprogrammable, facilitating repeated information protection and display. The design of tough hydrogels with rewritable fluorescent patterns and reconfigurable shapes should guide the future development of smart materials with improved security and wider applications in aqueous environments.

Efficient and sustainable treatment of tannery wastewater by a sequential electrocoagulation-UV photolytic process

Tannery wastewater contains large amounts of pollutants that, if directly discharged into ecosystems, can generate an environmental hazard. The present investigation has focused the attention to the remediation of wastewater originated from tanned leather in Tunisia. The analysis revealed wastewater with a high level of chemical oxygen demand (COD) of 7376 mgO2/L. The performance in reduction of COD, via electrocoagulation (EC) or UV photolysis or, finally, operating electrocoagulation and photolysis in sequence was examined. The effect of voltage and reaction time on COD reduction, as well as the phytotoxicity were determined. Treated effluents were analysed by UV spectroscopy, extracting the organic components with solvents differing in polarity. A sequential EC and UV treatment of the tannery wastewater has been proven effective in the reduction of COD. These treatments combined afforded 94.1 % of COD reduction, whereas the single EC and UV treatments afforded respectively 85.7 and 55.9 %. The final COD value of 428.7 mg/L was found largely below the limit of 1000 mg/L for admission of wastewater in public sewerage network. Germination tests of Hordeum Vulgare seeds indicated reduced toxicity for the remediated water. Energy consumptions of 33.33 kW h/m3 and 314.28 kW h/m3 were determined for the EC process and for the same followed by UV treatment. Both those technologies are yet available and ready for scale-up.

Mechanical Properties and Photomechanical Fatigue of Macro- and Nanodimensional Diarylethene Molecular Crystals.

The diarylethene derivative, 1,2-bis(2,4-dimethyl-5-phenyl-3-thienyl)perfluorocyclopentene, undergoes a reversible photoisomerization between its ring-open and ring-closed forms in the solid-state and has applications as a photomechanical material. Mechanical properties of macrocrystals, nanowire single crystals, and amorphous films as a function of multiple sequential UV and visible light exposures have been quantified using atomic force microscopy nanoindentation. The isomerization reaction has no effect on the elastic modulus of each solid. But going from the macro- to the nanowire crystal results in a remarkable over 3-fold decrease in the elastic modulus. The macrocrystal and amorphous solids are highly resistant to photomechanical fatigue, while nanowire crystals show clear evidence of photomechanical fatigue attributed to a transition from crystal to amorphous forms. This study provides first experimental evidence of size-dependent photomechanical fatigue in photoreactive molecular crystalline solids and suggests crystal morphology and size must be considered for future photomechanical applications.

A natural cyanobacterial protein C-phycoerythrin as an HS- selective optical probe in aqueous systems.

A naturally fluorescent cyanobacterial protein C-phycoerythrin (CPE) was investigated as a fluorescent probe for biologically and environmentally important hydrosulphide (HS-) ion. It was selective for HS amongst a large anion screen and the optical response was rapid. Sequential UV-visible titration showed considerable peak shift and attenuation with increasing [HS-] while fluorescence titration proved that HS- quenched CPE fluorescence in a concentration dependent manner. The linear response range was 0-2mM HS- while the Stern Volmer curve was non-linear and the limit of detection was 185.12μM. Except bicarbonate and glycine, no anion or biomolecule interfered with the detection even at 10 times the concentration of HS-. It was also free of influences from other sulphur forms like sulphite, sulphate and thiosulphate. CPE reliably detected HS- in freshwater and effluent samples, though some under- and over - estimation was evident. The % recovery ranged from ~96 to 105% (RSD~0.035-0.188%). FTIR analysis showed significant changes in the amide I and II regions of CPE, along with minor modifications in the amide III region as well, showing that HS- was able to influence the protein secondary structure at higher concentrations.

UV‐Micropatterned Miniaturization: Rapid In Situ Photopatterning and Miniaturization of Microscale Features on Shrinkable Thermoplastics

AbstractShrink lithography is a promising top‐down micro/nanofabrication technique capable of miniaturizing patterns/structures to scales much smaller than the initial mold, however, rapid inexpensive fabrication of high‐fidelity shrinkable microfeatures remains challenging. This work reports the discovery and characterization of a simple, fast, low‐cost method for replicating and miniaturizing intricate micropatterns/structures on commodity heat‐shrinkable polymers. Large‐area permanent micropatterning on polystyrene and polyolefin shrink film is attained in one step under ambient conditions through brief irradiation by a shortwave UV pencil lamp. After baking briefly in an oven, the film shrinks biaxially and the miniaturized micropatterns emerge with significantly reduced surface area (up to 95%) and enhanced depth profile. The entire UV‐micropatterned miniaturization process is highly reproducible and achievable on benchtop under a few minutes without chemicals or sophisticated apparatus. A variety of microgrid patterns are replicated and miniaturized with high yield and resolution on both planar and curved surfaces. Sequential UV exposures enable easy and rapid engineering of sophisticated microtopography with miniaturized, multiscale, multidimensional microstructures. UV–ozone micropatterned polystyrene surfaces are well‐suited for lab‐on‐a‐chip analytical applications owing to the inherent biocompatibility and enhanced surface hydrophilicity. Miniaturization of dense, periodic micropatterns may facilitate low‐cost prototyping of functional devices/surfaces such as micro‐optics/sensors and tunable metamaterials.

Characterization of a Sequential UV Photolysis-Biodegradation Process for Treatment of Decabrominated Diphenyl Ethers in Sorbent/Water Systems.

Decabrominated diphenyl ether (BDE-209) is a primary component of the brominated flame retardants used in a variety of industrial and domestic applications. BDE-209 bioaccumulates in aquatic organisms and has been identified as an emerging contaminant that threatens human and ecosystem health. Sequential photolysis-microbial biodegradation processes were utilized here to treat BDE-209 in clay- or soil-water slurries. The removal efficiency of BDE-209 in the clay-water slurries was high; i.e., 96.5%, while that in the soil-water slurries was minimal. In the clay-water slurries the first order rate constants for the UV photolysis and biodegradation of BDE-209 were 0.017 1/day and 0.026 1/day, respectively. UV wavelength and intensity strongly influenced the BDE-209 photolysis and the subsequent biodegradation of photolytic products. Facultative chemotrophic bacteria, including Acidovorax spp., Pseudomonas spp., Novosphingobium spp. and Sphingomonas spp., were the dominant members of the bacterial community (about 71%) at the beginning of the biodegradation; many of these organisms have previously been shown to biodegrade BDE-209 and other polybrominated diphenyl ether (PBDE) congeners. The Achromobacter sp. that were isolated (NH-2; NH-4; NH-6) were especially effective during the BDE-209 degradation. These results indicated the effectiveness of the sequential UV photolysis and biodegradation for treating certain BDE-209-contaminated solids; e.g., clays; in bioreactors containing such solids as aqueous slurries. Achieving a similar treatment effectiveness for more heterogeneous solids containing natural organic matter, e.g., surface solids, appears to be significantly more difficult. Further investigations are needed in order to understand the great difference between the clay-water or soil-water slurries.

Energy selective time of flight spectrometer to study low energy dissociation channels of PAHs

SynopsisDissociation channels induced by sequential UV multiphoton absorption of vapour phase fluorene cation is investigated using energy selective ToF mass spectrometer. Neutral fluorene molecule is ionized by resonantly enhanced multiphoton absorption and dissociated in the same photon field. The main goal of this experiment is to determine the rate constants of statistical dissociation channels of PAH cations for a wide range of internal energies.

Cooperative defect-enriched SiO2 for oxygen activation and organic dehydrogenation

Tailoring oxide functionalities via defect engineering is an effective approach in many advanced materials. Here we report that introducing defect sites in SiO2 via sequential hydrogenation and UV light pre-treatment steps can invoke synergism for oxygen activation and organic dehydrogenation under ambient conditions in the absence of light. The hydrogenation step is proposed to break SiOSi bonds to give an E′δ center – silanol pair. UV light pre-treatment then serves to dehydroxylate the silanol group to give a non-bridging oxygen hole centers (NBOHC). The two defect sites work in harmony to activate oxygen and in turn oxidize formic acid. First-principles calculations indicated that UV light pre-treatment lowered the energy barrier for oxygen activation and formic acid decomposition on the defect sites. Re-illuminating the used SiO2 led to partial recovery of the defect sites and hence oxidation performance. The study demonstrates the capacity for generating synergistic defects in simple metal oxides as an effective way to enhance performance for oxidation processes.

Chlorination and ultraviolet disinfection of antibiotic-resistant bacteria and antibiotic resistance genes in drinking water

This study determined the effectiveness of chlorine, UV and combination of UV/chlorine in inactivating antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARG), as well as potential repair of these bacteria following disinfection processes in drinking water. Previous studies have assessed the efficacy of UV disinfection in inactivating ARBs, however, most of these studies have focused on wastewater treatment applications. The use of chlorine and UV disinfection at typical drinking water industry doses was found to not completely eliminate the resistance genes. Using 30 mg/min/L of chlorine, the inactivation of tet(A), bla- TEM1 , sul1, mph(A) was 1.7-log, while a UV fluence of 200 mJ/cm 2 only resulted in a reduction of up to 1.2-log of these genes. This suggests that these genes can continue to be present in distribution systems even following disinfection. On the other hand, the application of sequential UV disinfection followed by chlorination significantly reduced the ARGs and had synergistic effects compared to single disinfectant use, with a resulting synergy in the inactivation achieved (log units) ranging between 0.01 and 0.62-log across the tested ARGs . The ARBs also demonstrated the potential for re-growth following chlorination up to 5 mg/L and UV disinfection of up to 10 mJ/cm 2 under the conditions of this study.

Highly oriented SnS2/RGO/Ag heterostructures for boosting photoeletrochemical and photocatalytic performances via schottky and RGO-n dual-heterojunctions interfacial effects

A single semiconductor remains a great challenge for photocatalysis due to highly recombination of charge carriers. However, construction of multiple heterojunctions photocatalysts is an effective way for photocatalysis technique. Herein, two-dimensional sheet-like highly oriented SnS2/RGO/Ag (SRA) nanocomposites with multiple junctions including schottky- and RGO-n junctions designed and synthesized via hydrothermal strategy followed by in situ sequential UV reductions. The as-prepared SRA nanocomposites exhibited superior photoelectrochemical conversion efficiencies and photocatalytic activities for the degradation of typical antibiotics Norfloxacin (NOR) under simulated solar light condition, with the highest removal ratio of 94%. XPS and low temperature EPR technology demonstrates the existence of oxygen vacancies and chemical bond effect among SnS2, Ag and RGO components. Highly oriented crystal facet and efficient spatial charge carrier separations and interfacial transfers in the photo-induced redox reactions are evidenced by various physical techniques. Interestingly, in this paper, RGO was proposed to act as holes trapper to improve photo responsive charge separation in great extent. The mechanism of photoinduced redox reactions including the pathways of interfacial charges transfers and ROS species generations have been proposed in terms of the Density Functional Theory (DFT) quantum calculations and the outcomes of various physicochemical characterizations over SRA nanocomposites.

The innovative combined microwave-assisted and photo-polymerization technique for synthesis of the novel degradable hydroxyethyl (meth)acrylate/gelatin based scaffolds

The discovery of novel biodegradable biomaterials able to support and control cellular activity as well as development of an enhanced and efficient method for their fabrication, are of paramount importance in the field of tissue engineering. This study highlights the design of novel degradable hydrogels based on gelatin and hydroxyethyl (meth)acrylates using the innovative combined two-step sequential microwave-assisted and UV photo-polymerization technique. Chemical composition, morphology, swelling capacity and degradation rate of the synthesized hydrogels were evaluated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), swelling and weight loss measurements. As an initial step for evaluation of performance of the hydrogels in the biological environment, the in vitro biocompatibility of these hydrogels, was evaluated using L929 mouse fibroblasts. Obtained results demonstrated that the hydrogels possess a porous morphology with interconnected pores, 50% in vitro degradation after 7 months, and satisfied biocompatibility on L929 fibroblast cells. These unique performances of the hydrogels make them promising candidates for in vivo evaluation in clinical studies aiming at tissue regeneration.

Approaches towards the enhanced production of Rapamycin by Streptomyces hygroscopicus MTCC 4003 through mutagenesis and optimization of process parameters by Taguchi orthogonal array methodology.

The present research was conducted to define the approaches for enhanced production of rapamycin (Rap) by Streptomyces hygroscopicus microbial type culture collection (MTCC) 4003. Both physical mutagenesis by ultraviolet ray (UV) and chemical mutagenesis by N-methyl-N-nitro-N-nitrosoguanidine (NTG) have been applied successfully for the improvement of Rap production. Enhancing Rap yield by novel sequential UV mutagenesis technique followed by fermentation gives a significant difference in getting economically scalable amount of this industrially important macrolide compound. Mutant obtained through NTG mutagenesis (NTG-30-27) was found to be superior to others as it initially produced 67% higher Rap than wild type. Statistical optimization of nutritional and physiochemical parameters was carried out to find out most influential factors responsible for enhanced Rap yield by NTG-30-27 which was performed using Taguchi orthogonal array approach. Around 72% enhanced production was achieved with nutritional factors at their assigned level at 23 °C, 120rpm and pH 7.6. Results were analysed in triplicate basis where validation and purification was carried out using high performance liquid chromatography. Stability study and potency of extracted Rap was supported by turbidimetric assay taking Candida albicans MTCC 227 as test organism.

A photoresponsive soft interface reversibly controls wettability and cell adhesion by conformational changes in a spiropyran-conjugated amphiphilic block copolymer.

We developed a photoresponsive polymer soft interface, which was able to spatiotemporally control wettability and cell adhesion/detachment in a reversible manner, by introducing spiropyran into the hydrophobic block of an amphiphilic diblock copolymer. With alternating irradiation using UV and visible light, the surface exhibited unique reversible wettability changes; the direction of hydrophobicity and hydrophilicity change was opposite to the polarity change in spiropyran photo-isomerization. Light-dependent reversible control of spatiotemporal cell adhesion and detachment was also achieved with sequential UV (adhesion) and visible light irradiation (detachment). Cell detachment using noncytotoxic visible light was realized for the first time. Cell-patterning capability stably lasted for 25days. This photoresponsive surface could be applied to fabrication of engineered tissues comprised of several cellular species.