UV Irradiation Time Research Articles

UV-modified biochar-Bacillus subtilis composite: An effective method for enhancing Cd(II) adsorption from water

The adsorption of Cd(Ⅱ) in sewage by single-modified biochar systems have limitations, whereas composite modification can enhance the efficiency. In this study, reed straw biochar and Bacillus subtilis were used as raw materials. UV radiation was employed to modify the biochar, and subsequently, Bacillus subtilis was loaded onto the biochar by adsorption, creating modified biochar composites. The Cd(II) adsorption performance and removal efficiency of these composites were then investigated. It was characterized by BET, SEM-EDS, FT-IR, XRD and ZETA potential analysis. Adsorption experiments were conducted under varying conditions (initial Cd(Ⅱ) concentration, UV radiation time, initial pH, etc.), with adsorption isotherms and kinetic models used. Results indicated that 24 hours UV radiation significantly enhanced adsorption performance, increasing the biochar’s surface area by 40 % and pore volume by 20 %, and introducing numerous pores and oxygen-containing functional groups to the biochar's surface. Significantly enhancing the saturation adsorption capacity for Cd(II) from 23.98 mg/g to 49.93 mg/g after UV- Modified biochar was loaded with Bacillus. Modified biochar composites performed better compared to single-modified biochar across different initial Cd(Ⅱ) concentrations, particularly in slightly alkaline environments. The primary adsorption mechanisms were chemical adsorption, such as ion exchange and surface precipitation. The synergistic effect of UV radiation and microbial loading significantly enhanced Cd(Ⅱ) adsorption efficiency. This study demonstrates that composite modification is a more efficient method, aiding in the removal of heavy metal ion Cd(Ⅱ) from water.

Colorimetric Detection of Aqueous N-Nitrosodimethylamine via Photonitrosation of a Naphtholsulfonate Indicator.

N-Nitrosamines are contaminants found throughout the environment, including in drinking water, and many nitrosamines are likely potent carcinogens. Correspondingly, there is a need for rapid and cost-effective in-field detection methods that can provide timely information about their contamination levels in water. This study details a colorimetric assay for detecting aqueous N-nitrosodimethylamine (NDMA) by photochemical nitrosation of a commercial naphtholsulfonate, to offer an attractive alternative to traditional laboratory-based analysis. The resulting naphthoquinone-oxime coordinates to aqueous iron(II) ions to form a green complex, allowing for direct visual detection. Characterization via Mössbauer and electron paramagnetic resonance (EPR) spectroscopy, alongside single-crystal structure determination, provides comprehensive structure information on the iron indicator complex. Optimization of detection conditions, including UV irradiation and response times, led to an improved colorimetric detection method with a limit of detection of 0.66 ppm for NDMA. The practical applicability and selectivity of this colorimetric detection scheme make it a promising candidate for the development of field-deployable sensors for NDMA in environmental water samples.

A superhydrophilic/air superoleophobic sponge based on layer by layer deposition for high-performance continuous adsorption water in oil

At present, there are few studies on the removal of water from oil, but water in fuel can cause machine malfunctions and even safety accidents, which cannot be ignored. In this study, an oil-resistant superhydrophilic/air superoleophobic sponge (SS-MS) was designed to selectively absorb water from oil. Through layer by layer deposition, polyphenols, particles, and fluorinated surfactants were assembled on the sponge, finally achieving the effect of super hydrophilic and super oil phobic in the air. The contact angle of the modified sponge SS-MS on diesel oil can reach 153°, and the absorption efficiency of water in diesel oil can reach more than 99 %. Moreover, a continuous selective absorption device for water in oil was constructed, the SS-MS sponge can still achieve a water absorption efficiency of 98 % after ten cycles. Importantly, the SS-MS has excellent mechanical and chemical stability under 80 % strain, different pH, UV irradiation times and temperatures. In addition, the materials used in this study are all green and low-pollution substances, and melamine sponge has the advantages of low price, light weight, good elasticity and high porosity. In summary, SS-MS offers a new approach to remove water from fuel and has the potential for large-scale applications.

Photo/thermal dual-responsive azobenzene-based photosensitive resin for 4D printing

4D printing, combining the advantages of 3D printing and stimuli-responsive materials, provides a precise and rapid fabrication method for complex-shaped smart objects. In this study, the photoisomerization characteristic of azobenzene is used to develop 4D printable resins composed of azobenzene-based acrylates (AZO) and other acrylate compounds, which can be UV-cured and 3D printed into objects with photo and thermal dual responsiveness. UV-curing kinetics reveal that AZO competes with the photoinitiator for photons during photopolymerization, reducing the generation of reactive oxygen species and subsequently affecting the mechanical properties of UV-cured resin. The optimum content of AZO in 4D printing resins is 0.5 wt%, producing 3D printed objects with excellent mechanical properties, including a maximum stress of 25.2 MPa and a strain of 100 %. This ensures the successful formation of complex-shaped objects in the 3D printing process. Moreover, the objects printed with this photosensitive resin demonstrate exceptional shape memory capabilities, achieving a 100 % shape recovery ratio over three cycles of thermal stimulation. The printed openwork spheroid with a concave shape can successfully revert to its original form after 48 s of irradiation with 365 nm UV light. The degree of shape recovery can be precisely controlled by adjusting the UV irradiation time and position. Therefore, these photo/thermal dual-responsive 4D objects show great application prospects in medical devices and smart materials.

Role of Density and Conformational Composition in the Surface-to-Bulk Molecular Dosing of Photosensitive Surfactant Monolayers.

Poorly water-soluble photosensitive monolayers might enable very precise control of the rate and number of desorbing molecules by controlling both the monolayer density and conformational composition. In this perspective, we systematically characterized the interfacial behavior of Langmuir monolayers consisting of a poorly water-soluble azobenzene-containing surfactant as a function of its trans/cis ratio. Precise control of the conformational ratio was achieved by controlling the UV irradiation time, allowing researchers to investigate compositions spanning from 100% trans to 90% cis. Our results demonstrate that in 100% trans monolayers, molecules do not desorb with compression until a threshold area is reached. Instead, the number of molecules desorbing in mixed trans-cis monolayers can be modulated by controlling both the composition and the compression rate. Additionally, the desorption rate at constant density is also strongly composition-dependent, and it accounts for two different regimes with two different characteristic times. We will show that trans molecules mostly desorb according to the slow regime while cis molecules conform to the fast one, but the two conformers mutually influence each other.

Initial Litter Chemistry and UV Radiation Drive Chemical Divergence in Litter during Decomposition.

Litter's chemical complexity influences carbon (C) cycling during its decomposition. However, the chemical and microbial mechanisms underlying the divergence or convergence of chemical complexity under UV radiation remain poorly understood. Here, we conducted a 397-day field experiment using 13C cross-polarization magic-angle spinning nuclear magnetic resonance (13C-CPMAS NMR) to investigate the interactions among the initial chemistry, microbial communities, and UV radiation during decomposition. Our study found that the initial concentrations of O-substituted aromatic C, di-O-alkyl C, and O-alkyl C in Deschampsia caespitosa were higher than those in Kobresia tibetica. Litter's chemical composition exhibited divergent patterns based on the initial chemistry, UV radiation, and decay time. Specifically, D. caespitosa consistently displayed higher concentrations of di-O-alkyl C and O-alkyl C compared to K. tibetica, regardless of the UV exposure and decay time. Additionally, litter's chemical complexity was positively correlated with changes in the extracellular enzyme activities, particularly those involved in lignin, cellulose, and hemicellulose degradation, which accounted for 9%, 20%, and 4% of the variation in litter's chemical complexity, respectively. These findings highlighted the role of distinct microbial communities in decomposing different C components through catabolism, leading to chemical divergence in litter. During the early decomposition stages, oligotrophic Planctomycetes and Acidobacteria metabolized O-alkyl C and di-O-alkyl C under UV-blocking conditions. In contrast, copiotrophic Actinobacteria and Chytridiomycota utilized these components under UV radiation exposure, reflecting their ability to thrive under UV stress conditions due to their rapid growth strategies in environments rich in labile C. Our study revealed that the inherent differences in the initial O-alkyl C and di-O-alkyl C contributed to the chemical divergence, while UV radiation further influenced this divergence by shifting the microbial community composition from oligotrophic to copiotrophic species. Thus, differences in the initial litter chemistry, microbial community, and UV radiation affected the quantity and quality of plant-derived C during decomposition.

CeO2-CuO composites prepared via supercritical antisolvent precipitation for photocatalytic hydrogen production from lactic acid aqueous solution

The global increase in energy demand requires a continuous search for renewable and clean alternative resources to fossil fuels. Hydrogen is emerging as a promising energy carrier for the future; its production via photocatalysis, driven by sunlight, can directly convert solar energy into a usable or storable energy resource. However, water splitting requires sacrificial agents or electron donors/hole scavengers, such as short-chain organic acids. This research explores the use of lactic acid as a source for photocatalytic hydrogen production, offering valuable alternatives for wastewater management and renewable energy production. This study employed the innovative supercritical antisolvent (SAS) technique to micronize the precursors of both the active phase (CeO2) and co-catalyst (CuO), ensuring rapid and complete solvent removal and size reduction of photocatalyst precursors. The prepared samples were characterized by field emission scanning electron microscopy (FESEM), Fourier transform infrared (FT-IR) spectroscopy, dynamic light scattering (DLS) analysis, Brunauer-Emmett-Teller (BET) analysis and thermogravimetric analysis (TGA). This study has shown that the micronization process resulted in a notable improvement in CeO2 photocatalytic activity, attributed to the reduction of the dimensions of the powders. Hydrogen production was equal to 3989 μmol L−1 for the SAS-produced photocatalyst while using a commercial CeO2 sample resulted in H2 production of 2519 μmol L−1. The enhanced photoactivity of CeO2-CuO composites was found to be related to the presence of CuO. The optimal CuO amount was equal to 0.5 wt%, determining a hydrogen production of 9313 μmol L−1 after 4 h of UV irradiation time. A photocatalytic test carried out with deuterated water (D2O) instead of distilled H2O demonstrated that hydrogen was preferentially produced from water splitting reaction, whereas lactic acid acted as a sacrificial agent being oxidized from positive holes photogenerated in the valence band of CuO.

Photoactivated Circularly Polarized Room‐Temperature Phosphorescence from Phenoselenazine Derivative and Its Application in Information Security†

Comprehensive SummaryRoom‐temperature phosphorescence (RTP) materials have experienced rapid development due to their potential in organic light‐ emitting diode, information security, bioimaging, etc. However, the design of chiral organic phosphors with circularly polarized RTP (CPP) property remains a formidable challenge. Here, we introduce a chiral perturbation approach using a combination of chiral binaphthol and phenoselenazine derivative to achieve CPP. The photoactivated CPP in polystyrene (PS) film demonstrates a luminescence dissymmetry factor (glum), emission efficiency, and RTP lifetime up to 9.32 × 10–3, 27.0%, and 40.0 ms, respectively. The remarkable sensitivity of PS film to oxygen and temperature enables the adjustable emission colors, ranging from green to offwhite and blue under varying conditions. The doping systems, utilizing hosts of triphenylphosphine and 9‐phenylcarbazole, demonstrate an extended CPP lifetime of 85.9 ms and exhibit a persistent mechanoluminescence property with low pressure response threshold as low as 0.15 N. The information security provided by this CPP material was attained via the using of diverse emission colors and afterglow generated by distinct UV irradiation times and host materials. Alternately, it can also be achieved by observing different emission patterns using R‐ and L‐polarizer. The research has presented a reliable approach for producing CPP materials with high emission efficiency and glum.

The structural and optical properties of PVA/CMC copolymer cured by UV irradiation for different times

Poly(vinyl alcohol) (PVA)/carboxymethylcellulose (CMC) blend films with equal amounts (0.25 g) of both polymers were prepared through a simple and low-cost comparative casting method. Then, the PVA/CMC blend films were exposed to ultraviolet (UV) radiation for varied time intervals (1, 12, 26, 32, 40 and 48 h). The UV-irradiation effect on the physical properties of as-prepared films, including the structure, morphology, composite and optical properties (transmittance, absorbance and band gap (E g)), was examined. Field-emission scanning electron microscopy images showed that UV irradiation had a strong effect on the shape of PVA/CMC blend films. The X-ray diffraction patterns showed various crystalline qualities in the microstructure of as-synthesized samples. The Fourier transform infrared spectra showed that the UV-irradiation time and CMC film had a positive impact on the blend polymer structure since covalent connections were formed between CMC and PVA. Furthermore, the analysis results of optical inspections showed that the absorbance of the PVA/CMC films improved with an increment in irradiation time from 1 to 40 h. Important tuning of the E g values of blend films was realized. It showed a slight increase from 4.64 to 4.84 eV with increasing irradiation time from 1 to 40 h. The E g value (3.21 eV), however, displayed an inverted behavior due to an increased irradiation time of 48 h. This reduction could be ascribed to the creation of defects inside the blend band gap. Finally, the physical property modification of PVA/CMC blend film using UV irradiation made it an amazing contender in the optoelectronic field.

Synthesize electrode material based on rGO/Polyacrylic acid prepared by a combination of direct ink writing technique and UV irradiation

In this work, the rGO/polyacrylic acid (rGO/PAA) composite film was synthesized using the 3D direct ink writing technique with GO/acrylic acid (GO/AA) ink and UV irradiation. Results show that after a UV irradiation time of 3.6 seconds, GO was reduced into rGO, and AA was polymerized into PAA. The prepared material was characterized by using Fourier Transform Infrared Spectroscopy (FT-IR), Energy-dispersive X-ray spectroscopy (EDX), cyclic voltammetry (CV), and galvanostatic charge/discharge technique (GCD). The obtained composite film is applied as an electrode for the supercapacitor. The electrode has a specific capacity of 321 F/g at a current density of 1 A/g and retains 82% of its initial capacity after 5,000 charge/discharge cycles at a current density of 5 A/g.

Enhancing Domestic Wastewater Treatment: A Study on the Efficacy of Tiered Filtration and a Combined Photocatalytic Ozonation Methods

This study aimed to construct an optimized reactor using photocatalytic ozonation, and its effectiveness was determined using PermenLHK No. 86/2016. The Tanjung Uma housing estate in Batam city was selected as the study sample site for domestic wastewater because of its role as a significant water body that receives liquid waste from a majority of activities across the city. The experiment employed a quantitative research approach and a true experimental approach, testing variables (catalyst weight, UV irradiation time, and ozonation duration) in a laboratory setting (25°C and 40-70% Humidity). The study found that the optimized parameter (a combination of 2 h of irradiation, with 2 g of TiO2 along with 5 min of ozonation) resulted in a significant difference in water quality parameters compared to before treatment with 92% effectivity. It can be concluded that this Reactor prototype was highly successful in reducing environmental impacts based on its effectiveness

UV-Radiation and TiO2 Nanoparticles Effects on Physical Properties of PVA/CMC/TiO2 Nanocomposite Films

Fabrication of nanocomposite films of polyvinyl alcohol/carboxymethyl cellulose (PVA/CMC) blended with Titanium dioxide nanoparticles (TiO2 NPs) by a modest solution casting technique is investigated. Also, TiO2 NPs and UV-irradiation effects for different intervals (12, 26, 40, and 48 hours) on the morphology (FESEM), structure (XRD), composition (FTIR) and optical properties (UV-Vis) of as-prepared films are inspected. FESEM images display that the morphology of PVA/CMC/TiO2 nanocomposite films is altered due to the strong influence of TiO2 NPs and UV exposure. The XRD spectra indicate that the amorphous phase of the samples has changed (decline or enhancement) due to UV exposure. The FTIR spectra demonstrate that the UV-irradiation period had a favourable impact on polymer structure by exhibiting some interesting IR peaks. Furthermore, the UV-Vis examination illustrates that the increased UV-irradiation times (12 h to 40 h) and TiO2 NPs addition improved the absorption intensity of the as-prepared films. Interestingly, the Energy gap Eg of the nanocomposite films was tuned from 4.47 eV to 5.01 eV with increased irradiation time (12 h to 40 h). In contrast, due to a higher increased UV-irradiation time of 48 h, the Energy gap Eg value of nanocomposite film was decreased to 4.62 eV. That can be attributed to the strong effect of UV exposure, which influenced the creation of structural defects. Finally, these findings prove that the PVA/CMC/TiO2 nanocomposite films have an amazing chance to be used in important optoelectronic applications.

The bacteriostatic effect of a new controlled-release carotenoids-silver nanoparticle

Discuss the bacteriostatic effect of a novel controlled release silver nanoparticles carotenoids-silver nanoparticle. Detect the optimal extraction conditions for carotenoids through material liquid ratio, different ultrasonic temperatures and times; Detect the optimal synthesis conditions of carotenoids-silver nanoparticle through different volume ratios, UV irradiation times, and temperatures; Detect the bacteriostatic effects on Escherichia coli and Staphylococcus albus using the minimum inhibitory concentration (MIC) and Oxford cup agar plate diffusion method. The experiment proved that the best extraction effect of carotenoids was achieved when the volume ratio of orange peel powder to ethanol was 1:25, the ultrasound time was 40 min, and the temperature was 50 °C; When the amount of carotenoid extract added is 12 mL, the concentration of silver nitrate is 8 mmol/l, the UV irradiation time is 40 min, and the ultrasound temperature is 60 °C, the synthesized carotenoids-silver nanoparticle has the highest absorbance value; carotenoids-silver nanoparticle have strong inhibitory effects on the growth of both Escherichia coli and Staphylococcus albus. As the concentration increases, the bacteriostatic effect also becomes stronger, especially the strongest inhibitory effect on Staphylococcus albus. It was shown that carotenoids-silver nanoparticle has significant bacteriostatic effects, providing new ideas for the development of bacteriostatic agents in plant resources.

UV‐Induced Oxidation Preparation of Multi‐Functional Lignin‐Based AgNPs and its Application for Conductive Coating, Antibacterial Enhancement, and Product Separation

AbstractThis study presents a novel approach for regulating the properties of lignin‐based silver nanoparticles (AgNPs), which was UV‐induced Tetrahydrofuran (THF) to form peroxide for the etching of these nanoparticles. The lignin coating was first degraded by oxidation, and the properties of the exposed AgNPs changed under etching. Notably, water can greatly regulate the oxidation capacity of the THF medium, thereby controlling the degradation degree of lignin coating and obtaining dissolution, aggregation, precipitation, and color‐variable phenomena of AgNPs under the synergistic effect of UV irradiation and peroxide etching. By adjusting UV irradiation time, various functional products of silver nanowires (AgNWs), color‐variable AgNPs, lignin‐based AgNPs aggregates, and composite solution of Ag particles and Ag+ were obtained. The transformation of these product properties is closely related to the oxidation capacity of H2O/THF medium. In addition, Multi‐functional Lignin‐based AgNPs show excellent application potential in conductive coating, antibacterial enhancement, and product separation, providing a promising avenue for the targeted utilization of lignin‐based AgNPs.

Effect of UV radiation on the high temperature and fatigue performance of SBS modified asphalt and asphalt mixture

In this study, the effects of UV radiation on the high temperature fatigue performance of SBS modified asphalt and asphalt mixtures were analyzed, and the effects of outdoor atmospheric UV radiation were simulated by indoor UV accelerated aging test. The results showed that the increase of UV radiation time led to the increase of creep recovery rate of asphalt and the decrease of irrecoverable creep flexibility, i.e., the resistance to permanent high temperature deformation of SBS modified asphalt was improved. The fatigue cracking resistance of asphalt was weakened and accelerated by radiation. UV radiation increased the rutting resistance of asphalt mixtures and weakened the fatigue resistance at high temperatures. At the same time, UV radiation reduced the aromatic and saturated content of SBS modified asphalt, which led to a reduction in the relative aromatic and saturated content of asphalt mixtures.

Modification of red mud catalyst using oxalic acid-assisted UV treatment for toluene removal

An innovative simplified modification method for red mud had been proposed, which enabled its utilization as an active Fe2O3-rich component for catalytic oxidation of toluene. The Box-Behnken design, based on Response Surface Methodology (RSM), was employed to optimize the modification of bauxite residue using oxalic acid combined with UV irradiation. Based on the experimental conditions, the optimal conditions for three independent parameters were determined: acid leaching time (2 hours), UV irradiation time (1 hour), and acid dosage (150 ml),which was in order to enhance the maximum catalytic efficiency of toluene at 300 °C. Under the optimal preparation conditions provided by the Box-Behnken design, the catalytic efficiency of toluene at 300°C could reach 99.2%. In comparison to the acid-modified mud (MRM) and untreated bauxite residue (RM), the aluminum refinery residue modified with oxalic acid-assisted UV irradiation (MRM-UV) exhibited the formation of oxalate sub-iron precipitates, resulting in significantly lower catalytic temperatures (238°C). Furthermore, through XRF, XRD, XPS, O2-TPD, and H2-TPD analysis, it was discovered that a large amount of iron oxide and calcium oxide formed CaO+Fe2O3→Ca2Fe2O5, strengthening the interaction between iron and calcium, augmenting the migration rate of lattice oxygen from the bulk phase to the surface. Consequently, T50 were reduced by 20.9% and 31.8% when compared to MRM and RM. Moreover, the CO2 selectivity of MRM-UV increased from 8.6% to 70.5% compared to RM at 300°C. Using in situ DRIFTS, the reaction pathway of toluene on MRM-UV was identified as benzyl alcohol → benzaldehyde or benzoyl → benzoate→maleic anhydride→CO2 and H2O. The process refinement reduced VOCs emissions and promoted sustainable waste management by combining oxalic acid with catalytically active red mud.

Co-existing inorganic anions influenced the Norrish I and Norrish II type photoaging mechanism of biodegradable microplastics

The degradation of biodegradable plastics (BPs) in natural environments is constrained, and the mechanisms underlying their photoaging in aquatic settings remain inadequately understood. In view of this, this study systematically investigated the photoaging process of biodegradable Poly (butyleneadipate-co-terephthalate) microplastics (PBAT-MPs), which are more widely used. The investigation was carried out in the presence of common inorganic anions (Br−, Cl− and NO3−). The results of EPR, FTIR and FESEM tests, along with pseudo-first-order kinetics analyses, showed that the presence of NO3− promoted the photoaging of PBAT-MPs, while the presence of Br− and Cl− inhibited the photoaging of PBAT-MPs. In addition, the results of the Two-Dimensional Correlation Spectroscopy (2D-COS) analysis determined the order of the changes in the functional groups, revealing that the Norrish I and Norrish II reaction mechanisms are presented by PBAT-MPs during the aging process, and the process is closely related to the ion concentration and UV irradiation time. This study provides valuable insights for understanding the phototransformation process of BPs in natural aqueous environments.

Effect of TiN thin films deposited by oblique angle sputter deposition on sol-gel coated TiO2 layers for photocatalytic applications

TiO2 monolayer and TiN/TiO2 bilayer coatings were deposited on soda-lime glass prepared by mixing two techniques, TiO2 was deposited by sol-gel dip-coating and TiN film was deposited by oblique angle deposition using reactive magnetron sputtering at α=45° Structural analysis showed typical peaks of TiO2 anatase phase and cubic (Na-Cl type) structure of TiN. Roughness value of 3 nm was obtained for the TiN/TiO2 bilayer film with a rise and elongated grains size. It was found that the optical band gap energy decreases after coupling the TiN sub-layer which is explained by the incorporation of N atoms into TiO2 structure. At constant UV irradiation time, the photo-degradation of methylene blue rate increased for TiN/TiO2 film by 4 % compared to TiO2 film.

Conductance Evolution of Photoisomeric Single-Molecule Junctions under Ultraviolet Irradiation and Mechanical Stretching.

A comprehensive understanding of carrier transport in photoisomeric molecular junctions is crucial for the rational design and delicate fabrication of single-molecule functional devices. It has been widely recognized that the conductance of azobenzene (a class of photoisomeric molecules) based molecular junctions is mainly determined by photoinduced conformational changes. In this study, it is demonstrated that the most probable conductance of amine-anchored azobenzene-based molecular junctions increases continuously upon UV irradiation. In contrast, the conductance of pyridyl-anchored molecular junctions with an identical azobenzene core exhibits a contrasting trend, highlighting the pivotal role that anchoring groups play, potentially overriding (even reversing) the effects of photoinduced conformational changes. It is further demonstrated that the molecule with cis-conformation cannot be fully mechanically stretched into the trans-conformation, clarifying that it is a great challenge to realize a reversible molecular switch by purely mechanical operation. Additionally, it is revealed that the coupling strength of pyridyl-anchored molecules is dramatically weakened when the UV irradiation time is prolonged, whereas it is not observed for amine-anchored molecules. The mechanisms for these observations are elucidated with the assistance of density functional theory calculations and UV-Vis spectra combined with flicker noise measurements which confirm the photoinduced conformational changes, providing insight into understanding the charge transport in photoisomeric molecular junctions and offering a routine for logical designing synchro opto-mechanical molecular switches.

Photoinactivation of jack bean (Canavalia ensiformis) urease in fresh human urine using dichromatic low-pressure UV irradiation

In source-separating sanitation systems, inhibiting urease activity prevents enzymatic urea hydrolysis and volatilisation of ammonia when urine is concentrated by evaporation. This study tested UV-based photoinactivation as a novel alternative to existing methods of inactivating urease that require dosing urine with acid, base or oxidants. The enzymatic activity of jack bean (Canavalia ensiformis) urease in water, synthetic fresh urine and real fresh urine was investigated, with and without a 15 W low-pressure UV lamp that emitted 185 nm and 254 nm radiation. In UV-free controls, urea was hydrolysed at a rate of 3.2 × 10−3 mmol mgurease−1 min−1, 3.3 × 10−3 mmol mgurease−1 min−1 and 2.0 × 10−3 mmol mgurease−1 min−1 in water, synthetic urine and real urine, respectively. In the presence of UV, no urease activity was detected in any matrix. A UV irradiation time of 1.3 and 3.3 min was needed for inactivating urease in water and synthetic urine, respectively, whereas an irradiation time of 71 min was needed for inactivating urease in real urine. Overall, the electrical energy demand for photoinactivation of urease in real human urine was estimated to be 29.1 kWh m−3. Photolysis and photo-oxidation of amino acid residues at the active site of the enzyme were likely reasons for inactivation. Organic metabolites in real urine affected photoinactivation by (i) absorbing radiation between 190 nm and 400 nm, which reduced incident radiant flux; and (ii) scavenging hydroxyl radicals, which impeded oxidative damage to the enzyme. Overall, the findings demonstrate the feasibility of on-site treatment using a low-pressure UV lamp for inactivating urease in freshly excreted urine.