Photolysis Process Research Articles

Biohydrogen production: An outlook on methods, constraints, economic analysis and future prospect

Utilization of hydrogen as fuel lights into various technological, economic and ecological challenges. High production cost and low yield are main drawbacks of commercial hydrogen production methods. Hydrogen production by biological methods helps to overcome these issues owing to its merit such as cost-effective, non-pollutant, recyclability and efficiency in energy conversion. Research has been conducted in utilizing cyanobacteria and algal species for producing biohydrogen utilizing solar light and other sources. Developments have been made for improving biohydrogen productivity through genetic and metabolic engineering. This review outlines the importance of biohydrogen and the constraints in producing biohydrogen in detail. Biohydrogen production can be facilitated using photolysis, fermentation and electrochemical processes. Bioreactors can be used effectively with specific designs and configuration for increasing productivity. The challenges faced during biological production and methods to overcome those demerits are also included for bringing the uncharted principles for producing biohydrogen in an efficient method.

Revisiting the mechanisms of nitrite ions and ammonia removal from aqueous solutions: photolysis versus photocatalysis.

Nitrite ions and ammonia are widespread forms of inorganic water pollutants. Nevertheless, the mechanisms of their photolytic and photocatalytic reactions under UV-A irradiation are still fully undisclosed, particularly, at different pH values under aerobic and inert atmospheres. Herein, we have studied the photolytic decomposition of nitrite ions under different conditions using 365nm UV-A LED as a light source instead of mercury lamps that emit photons in the UV-B region and generate a lot of heat. The results indicated that the rate of nitrite disproportionation in the dark at pH ≤ 3.0 is remarkably high relative to the rate of the photolytic decomposition. At pH ˃ 3, the photolytic reaction is negligible and nitrite ions showed considerable stability. In contrast, the photocatalytic oxidation of nitrite ions over TiO2 photocatalysts, namely, TiO2P25, TiO2UV100, and TiO2 anatase/brookite mixture proceeds at pH ˃ 3.0. TiO2 P25 exhibited the highest photocatalytic activity at pH 5. Interestingly, the photolytic simultaneous removal of nitrite ions and ammonia was possible at pH 9.0 in the absence of oxygen (Ar atmosphere). A 42.69 ± 0.66%, 27.75 ± 1.7%, and 32.74 ± 0.59% of nitrogen calculated based on nitrite, ammonia, and both of them, respectively, can be removed after 6h of UV-A irradiation. The selectivity of N2 evolution was 77.6%. The nitrogen removal rate was significantly reduced in the presence of TiO2 photocatalyst evincing that TiO2 photocatalysis is applicable for nitrite ions oxidation, whereas the photolytic process is better suited for the simultaneous removal of nitrite ions and ammonia.

Exploring influence of organics on the photodegradation of nitroaromatic compounds: Focus on HONO/NO formations and kinetics

The effects of aromatic carbonyls (ACs), polycyclic aromatic hydrocarbons (PAHs) and phenols (PHs) on the photolysis of nitroaromatic compounds (ArNO2) in the solid phase were explored. The reactive nitrogen gas formation by the photolysis process was investigated in a cylindrical reactor coupled to a NOx analyzer. These organics had an enhanced or inhibited influence on the nitrous acid (HONO) and NO formations by the photolysis of 1-nitropyrene (NPy) and 5-nitrosalicylic acid (NSA), depending on the hydrogen abstraction and donation abilities of organics. Based on the high-performance liquid chromatography (HPLC) results, methyl-2-benzoylbenzoate (MBB), fluoranthene (FLA) and syringaldehyde (SG) showed a promoted effect on the photodegradation of NPy and NSA, as shown by an increase in the photolysis frequency of ArNO2 (JArNO2) by a factor of 1.19–2.76. Based on experimental results, the HONO source strength by the photolysis of ArNO2 in organic aerosols was estimated to be lower than 1 ppt h−1.

Current Trends in the Utilization of Photolysis and Photocatalysis Treatment Processes for the Remediation of Dye Wastewater: A Short Review

Development in the textile industry leads to an increased demand for the use of various dyes. Moreover, there is the use of some dyes in the food industry as well as medical diagnostics. Thereby, increased demand for dyes in various fields has resulted in dye-containing wastewater. Only a small portion of the generated wastewater is adequately treated. The rest is usually dumped or otherwise directly discharged into the sewage system, which ultimately enters rivers, lakes, and streams. The handling and disposal of such concentrated wastewater, especially the dye-containing wastewater, is considered to be a major environmental issue from the moment of its generation to its ultimate disposal. Conventional water treatment methods such as flotation, filtration, adsorption, etc., are non-destructive physical separation processes. They only transfer the pollutants to other phases, thereby generating concentrated deposits. The advanced oxidation process (AOP) is one of the most effective emerging methods for the treatment of wastewater containing chemical pollutants. The method involves the formation and interaction of highly reactive hydroxyl radicals under suitable activation conditions. These radicals are non-selective and efficient for the destruction and eventual mineralization of recalcitrant organic pollutants. This review aims at the pros and cons of using photocatalysis as an efficient AOP to degrade dye-containing wastewater.

Photodegradation of oxytetracycline by UV-assisted persulfate and percarbonate processes: kinetics, influencing factors, anion effect, and radical species.

In this study, the performance of ultraviolet (UV)-assisted persulfate (PS) and percarbonate (PC) oxidation processes in oxytetracycline (OTC) removal was investigated. UVC lamps were used for the photolysis process and the effect of operating parameters (initial pH, oxidant dose, initial OTC concentration, UV intensity) on OTC removal efficiency was determined. Control experiments were carried out at pH 5.5 and 32W UV power for 60min by adding a 4mM oxidant with 10mg/L initial OTC concentration. The OTC removal efficiency obtained as a result of only photolysis was 17.3% and the removal efficiency obtained by PS and PC oxidation alone was 18.3% and 12.7%, respectively. The OTC removal efficiencies increased in the combined processes and reached 58.1% and 69.9% for the UV-PS and UV-PC processes, respectively. The reaction rates of the processes were ranked as UV-PC > UV-PS > PS > UV > PC. In the UV-PS and UV-PC processes, the highest removal efficiencies were achieved at alkaline pH values. The OTC removal efficiency was increased with the increase in oxidant dose; however, the efficiency decreased after a certain dose due to the scavenging effect. The removal efficiency also increased as the initial OTC concentration decreased. The UV intensity had a positive effect on OTC removal efficiency. The effect of the water matrix on OTC removal efficiency was investigated while the dominant radical types were determined in UV-assisted processes. The EE/O values for the UV-PS and UV-PC processes were calculated as 211 kWh/m3 and 153 kWh/m3, respectively for 60min of reaction time. Although similar removal efficiencies were obtained with both UV-assisted processes, the UV-PC process steps forward in terms of being a novel, environmentally friendly, more economic, and promising technology for OTC removal.

Toxicity Assessment and Treatment Options of Diclofenac and Triclosan Dissolved in Water.

The presence of pharmaceutical and personal care products in water is increasing tremendously nowadays. Typical representatives are diclofenac (DCF) and triclosan (TCS). Acute toxicity of these substances was experimentally assessed using the freshwater algae Raphidocelis subcapitata (living, immobilized). The IC50 achieved for R. subcapitata was 177.7–189.1 mg·L−1 for DCF and 5.4–17.2 µg·L−1 for TCS, whereas, regarding DCF, the results corresponded to the values observed by other authors. Concerning TCS, the results were lower than predicted and indicated TCSs’ higher toxicity. The immobilized R. subcapitata showed comparable results with its living culture for DCF only. Regarding K2Cr2O7 and TCS, the immobilized alga was more sensitive. The DCF and TCF removal from water was tested by sorption, photocatalytic and photolytic processes. TiO2 was used as a photocatalyst. Norit and SuperSorbon were used as sorbents based on activated charcoal. The DCF decomposition achieved by both photo-processes was very fast. The starting concentration fell below the detection limit in less than one minute, while bioluminescence on Aliivibrio fischeri showed no toxic intermediates formed only in the case of photocatalysis. DCF and TCS removals by sorption were significantly faster on Norit than SuperSorbon, while the bioluminescence inhibition remained insignificant.

Ozonation and UV photolysis for removing anticancer drug residues from hospital wastewater

The present study investigates the use of UV light and the ozone process for doxorubicin, daunorubicin, epirubicin, and irinotecan degradation. The process was carried out using different pH values in hospital wastewater. The use of UV radiation reduces the concentration of anticancer drugs, but in all cases, this technology was not able enough to remove on the whole these contaminants from hospital wastewater. The best condition was achieved when using pH 9 for most of the analytes. Doxorubicin, daunorubicin, and epirubicin were degraded at 97.3%, 88.3%, and 99.0%, respectively. Irinotecan showed the lowest degradation, just 55.6%; a slightly higher degradation (63.8%) was obtained when pH 5 was used. Complete removal of doxorubicin, daunorubicin, epirubicin, and irinotecan was achieved when ozone treatment was used for all the pH studied. The results indicated that UV light and the ozone process can be used as a tertiary treatment to reduce the concentration of anticancer drugs in the effluents. Ozonation, therefore, proved to be more efficient than the photolysis process, when considering the percentual degradation of the original compounds in shorter timespans.

Photoproduct formation in coenzyme B12-dependent CarH via a singlet pathway

The CarH photoreceptor exploits of the light-sensing ability of coenzyme B12 ( adenosylcobalamin=AdoCbl) to perform its catalytic function, which includes large-scale structural changes to regulate transcription. In daylight, transcription is activated in CarH via the photo-cleavage of the Co-C5' bond of coenzyme B12. Subsequently, the photoproduct, 4',5'-anhydroadenosine (anhAdo) is formed inducing dissociation of the CarH tetramer from DNA. Several experimental studies have proposed that hydridocoblamin (HCbl) may be formed in process with anhAdo. The photolytic cleavage of the Co-C5' bond of AdoCbl was previously investigated using photochemical techniques and the involvement of both singlet and triplet excited states were explored. Herein, QM/MM calculations were employed to probe (1) the photolytic processes which may involve singlet excited states, (2) the mechanism of anhAdo formation, and (3) whether HCbl is a viable intermediate in CarH. Time-dependent density functional theory (TD-DFT) calculations indicate that the mechanism of photodissociation of the Ado ligand involves the ligand field (LF) portion of the lowest singlet excited state (S1) potential energy surface (PES). This is followed by deactivation to a point on the S0 PES where the Co-C5' bond remains broken. This species corresponds to a singlet diradical intermediate. From this point, the PES for anhAdo formation was explored, using the Co-C5' and Co-C4' bond distances as active coordinates, and a local minimum representing anhAdo and HCbl formation was found. The transition state (TS) for the formation of the Co-H bond of HCbl was located and its identity was confirmed by a single imaginary frequency of i1592 cm-1. Comparisons to experimental studies and the potential role of rotation around the N-glycosidic bond of the Ado ligand were discussed.

Retention and Inactivation of Quality Indicator Bacteria Using a Photocatalytic Membrane Reactor

The development of effective disinfection treatment processes is crucial to help the water industry cope with the inevitable challenges resulting from the increase in human population and climate change. Climate change leads to heavy rainfall, flooding and hot weather events that are associated with waterborne diseases. Developing effective treatment technologies will improve our resilience to cope with these events and our capacity to safeguard public health. A submerged hybrid reactor was used to test the efficiency of membrane filtration, direct photolysis (using ultraviolet-C low-pressure mercury lamps, as well as ultraviolet-C and ultraviolet-A light-emitting diodes panels) and the combination of both treatment processes (membrane filtration and photolysis) to retain and inactivate water quality indicator bacteria. The developed photocatalytic membranes effectively retained the target microorganisms that were then successfully inactivated by photolysis and advanced oxidation processes. The new hybrid reactor could be a promising approach to treat drinking water, recreational water and wastewater produced by different industries in small-scale systems. Furthermore, the results obtained with membranes coated with titanium dioxide and copper combined with ultraviolet-A light sources show that the process may be a promising approach to guarantee water disinfection using natural sunlight.

Structure, Spectra and Photochemistry of 2-Amino-4-Methylthiazole: FTIR Matrix Isolation and Theoretical Studies.

The structure, tautomerization pathways, vibrational spectra, and photochemistry of 2-amino-4-methylthiazole (AMT) molecule were studied by matrix isolation FTIR spectroscopy and DFT calculations undertaken at the B3LYP/6-311++G(3df,3pd) level of theory. The most stable tautomer with the five-membered ring stabilized by two double C=C and C=N bonds, was detected in argon matrices after deposition. When the AMT/Ar matrices were exposed to 265 nm selective irradiation, three main photoproducts, N-(1-sulfanylprop-1-en-2-yl)carbodiimide (fp1), N-(1-thioxopropan-2-yl)carbodiimide (fp2) and N-(2-methylthiiran-2-yl)carbodiimide (fp3), were photoproduced by a cleavage of the CS–CN bond together with hydrogen atom migration. The minor photoreaction caused by the cleavage of the CS–CC bond and followed by hydrogen migration formed 2-methyl-1H-azirene-1-carbimidothioic acid (fp15). We have also found that cleavage of the CS–CN bond followed by disruption of the N–C bond produced cyanamide (fp11) and the C(CH3)=CH–S biradical that transformed into 2-methylthiirene (fp12) and further photoreactions produced 1-propyne-1-thiole (fp13) or methylthioketene (fp14). Cleavage of the CS–CC bond followed by disruption of the N–C bond produced propyne (fp22) and the S–C(NH2)=N biradical that transformed into 3-aminethiazirene (fp23); further photoreactions produced N-sulfanylcarbodiimide (fp25). As a result of these transformations, several molecular complexes were identified as photoproducts besides new molecules in the AMT photolysis process.

Photolysis by UVA-visible light and thermal degradation of TNT in aqueous solutions according to aerodynamic thermal breakup droplet ionization mass spectrometry

The mechanism of photolytic degradation of 2-4-6-trinitrotoluene (TNT) in an aqueous solution (initial concentration 102 mg L−1) by UVA-visible light (>320 nm) was investigated by aerodynamic thermal breakup droplet ionization mass spectrometry. For photolysis, a DRK-120 mercury-quartz lamp was used. The final and intermediate products of the photolysis reaction were compared with known products of TNT transformation in the environment. The first step in the photolysis process under our conditions was found to be the association of TNT molecules into a fairly stable dimer. The TNT dimer formation proceed through the formation of a Meisenheimer complex. Thermal degradation of the TNT dimer in microdroplets within a heated capillary used as a flow reactor was studied next. It was shown that the degradation of the TNT dimer in microdroplets occurs very quickly (2.1 ms) at heating (up to 200–250 °C). Of course, heating an aqueous aerosol requires energy, but the transformation of TNT can be controlled using a combination of photo- and thermal treatments. We hope that these results will help to reduce the toxicity of TNT contaminants and remove nitroaromatic compounds from water at ambient conditions. In this work, the TNT dimer formed at the first stage is transformed with the loss of NO2 fragments or water. In addition, further polymerization of TNT is observed.

Photoactive Materials for Decomposition of Organic Matter Prior to Water Analysis—A Review Containing Original Research

Water plays a fundamental role in meeting the basic needs of society. Surface waters contain numerous organic pollutants, such as pesticides, drugs, and surfactants. The use of photolysis processes in organic matter degradation not only has practical applications in wastewater treatment but is also of major importance in the pretreatment of samples prior to the trace analysis of numerous analytes. The heterogeneous degradation is simple to implement prior to ultra-traces determination and is the only one allowed before the speciation analysis. Speciation analysis is currently the most important environmental challenge. The analysis of water, including tests associated with wastewater pretreatment and the monitoring of aqueous ecosystems, is the largest segment of environmental analysis. In the trace analysis of water, organic compounds are the principal interfering compounds reducing the quality of the obtained results or even preventing the determination of the examined analytes altogether. Some analytical techniques do not perform well in the presence, for example, of surfactants, so mineralization is sometimes required. Advanced oxidation processes are used to remove interfering organic compounds. The oxidation can be performed using homogenous photolysis (UV mineralization with hydrogen peroxide addition), while heterogenous photolysis using semiconductors helps to increase the removal efficiency of interferents dissolved in water. Utilizing semiconductor nanostructured materials as photocatalysts has been shown to be effective for the adequate removal of a wide spectrum of pollutants in water. Several semiconductor systems are used in the degradation of organic compounds, e.g., TiO2, Fe3O4, WO3, Fe2O3, ZnO, and mixtures of these oxides enriched with various precious metals, such as silver or gold. It is very challenging to manage the selectivity and reduction power so that organic compounds can be degraded but without disturbing the speciation of As, Cr, or Tl. Chemical modification of samples and the selection of semiconductor layers, light wavelength, and pH allow for the targeted degradation of specific compounds but may also indirectly affect the analysis of water samples. This review is a presentation of the state of the art of photocatalysis as a simple and effective technique for sample pretreatment in ultra-trace and speciation analysis and its critical as well as unpublished data related to this topic.

Non-radicals dominated degradation of sulfamethoxazole by a chemical-less microwave enhanced photolysis process

A chemical-less microwave enhanced photolysis process (named MW/UV) was established for sulfamethoxazole (SMX) degradation and the mechanisms were specifically studied. 96.7% of SMX could be removed in an extremely short reaction time of 140 s under 400 W of microwave and 23.0 mW/cm2 of UV light at 254 nm. The half-live of SMX was greatly shortened to 5 s in MW/UV process, compared with 67 s in UV process and 1386 s in MW process. MW/UV process was also effective when applied to complex real water matrices, such as river water, seawater, and synthetic waste water. Non-thermal effects of microwave were found to play an essential role in elevating photolysis degradation efficiency. The ROS formation detected by quenching experiments and EPR test showed that SMX degradation by MW/UV followed non-radicals dominated method, although 1O2 and OH co-existed in this system. 16 intermediates in total were detected by HPLC-Q-TOF and three degradation pathways based on 1O2 and OH oxidation were proposed according to the structural characteristics of the intermediates. Besides, toxicity evaluation of SMX and its intermediates revealed that MW/UV process could effectively reduce the toxicity of SMX. This study provides an efficient and promising scheme for practical SMX degradation.

Degradation of Organics and Change Concentration in Per-Fluorinated Compounds (PFCs) during Ozonation and UV/H2O2 Advanced Treatment of Tertiary-Treated Sewage

This study aimed to investigate the effect of H2O2 addition, ozone feed rate, and UV addition on the change in the concentration of organics such as CODMn, CODCr, TOC, and PFCs in tertiary-treated effluent from a sewage treatment plant (STP) during the O3 and UV/H2O2 process. The degradation of organic pollutants from tertiary effluent is a significant challenge because biological treatment cannot degrade these recalcitrant pollutants. Therefore, the O3/UV/H2O2 process was an effective method for treating recalcitrant organics. Several batch tests were conducted to investigate the direct UV photolysis, UV/H2O2, and ozone-based advanced oxidation process to degrade CODMn, CODCr, TOC, and PFCs. The chemical oxygen demand (COD) and total organic carbon (TOC) with UV irradiation showed 95% and 50% removal efficiency percentages under optimal conditions (initial pH = 6.7, H2O2 dosage = 50 mg/L, ozone feed rate = 5.8 mg/L/min. Moreover, UV irradiation, with the addition of H2O2, and a sufficient dose of ozone, demonstrated the efficient removal of organic compounds by the indication of radical oxidation. (·OH) is the dominant mechanism. However, AOPs are not sufficient to fully treat the PFC compound; thus, additional procedures are required to degrade PFCs. In this study, the removal of organic recalcitrant contaminants and the change in added PFC concentration in tertiary-treated sewage were investigated by applying the ozone-based advanced oxidation process.

The pathway of impacts of aerosol direct effects on secondary inorganic aerosol formation.

Airborne aerosols reduce surface solar radiation through light scattering and absorption (aerosol direct effects, ADEs), influence regional meteorology, and further affect atmospheric chemical reactions and aerosol concentrations. The inhibition of turbulence and the strengthened atmospheric stability induced by ADEs increases surface primary aerosol concentration, but the pathway of ADE impacts on secondary aerosol is still unclear. In this study, the online coupled meteorological and chemistry model (WRF-CMAQ; Weather Research and Forecasting-Community Multiscale Air Quality) with integrated process analysis was applied to explore how ADEs affect secondary aerosol formation through changes in atmospheric dynamics and photolysis processes. The meteorological condition and air quality in the Jing-Jin-Ji area (denoted JJJ, including Beijing, Tianjin, and Hebei Province in China) in January and July 2013 were simulated to represent winter and summer conditions, respectively. Our results show that ADEs through the photolysis pathway inhibit sulfate formation during winter in the JJJ region and promote sulfate formation in July. The differences are attributed to the alteration of effective actinic flux affected by single-scattering albedo (SSA). ADEs through the dynamics pathway act as an equally or even more important route compared with the photolysis pathway in affecting secondary aerosol concentration in both summer and winter. ADEs through dynamics traps formed sulfate within the planetary boundary layer (PBL) which increases sulfate concentration in winter. Meanwhile, the impact of ADEs through dynamics is mainly reflected in the increase of gaseous-precursor concentrations within the PBL which enhances secondary aerosol formation in summer. For nitrate, reduced upward transport of precursors restrains the formation at high altitude and eventually lowers the nitrate concentration within the PBL in winter, while such weakened vertical transport of precursors increases nitrate concentration within the PBL in summer, since nitrate is mainly formed near the surface ground.

Enantioselective hydrolysis and photolysis of mandipropamid in different aquatic environments - evaluation of influencing factors.

The hydrolysis and photolysis of the chiral fungicide mandipropamid were investigated, and the potential enantioselectivity of mandipropamid in solutions was further assessed. The aqueous solutions were filtered and directly injected into the liquid chromatography with tandem mass spectrometry. In the hydrolysis experiments, mandipropamid enantiomers hydrolyzed slowly in aquatic solutions with half-lives > 200days; nevertheless, rise of the pH and incubation temperature could increase the hydrolysis rates more than 1.1 times (half-lives decreased from 495.1 to 216.6days). Compared with the hydrolysis results, photolysis was found to be the main degradation pathway for mandipropamid in different solutions (half-lives < 14h, except in pH = 5.05 buffer solution). Organic solvents were able to accelerate the photolysis of mandipropamid, but acidic solutions and the addition of flavonoids or inorganic salts significantly inhibited the photolysis of mandipropamid. During the hydrolysis and photolysis processes, the configuration of mandipropamid enantiomers was stable and five possible transformation products were identified by high resolution mass spectrometry. Due to the enantiomeric fraction values > 0.5, the hydrolysis and photolysis of mandipropamid were enantioselective, and S-( +)-mandipropamid preferentially disspated in certain aqueous solutions. The systematic evaluation of the hydrolysis and photolysis of mandipropamid enantiomers may provide more accurate data for better assessment of environmental and ecological risks in aquatic ecosystems.

Tuning Catalyst-Free Photocontrolled Polymerization by Substitution: A Quantitative and Qualitative Interpretation.

Catalyst-free photocontrolled reversible addition-fragmentation chain transfer (RAFT) polymerization avoids the side effects of photocatalysts but has the accompanying slow kinetics, thereby warranting more efficient photolysis and faster chain transfer. To understand the underlying mechanisms, both quantitative and qualitative interpretations are needed. Such a goal can be achieved by the iCAS (imposed automatic selection and localization of complete active spaces) approach [J. Chem. Theory Comput. 2021, 17, 4846], which maintains the same CAS and meanwhile provides localized orbitals along the whole reaction. Taking dithiobenzoate as a representative of RAFT agents, it is found here that electron-donating substitution (by methoxy) clearly outperforms both electron-standing (by methyl) and electron-withdrawing (by cyano) substitutions in facilitating photo-RAFT polymerization, by narrowing the gap between the π* and σ* orbitals, so as to facilitate the π* → σ* charge transfer dominating both the photolysis and chain transfer processes. Such findings are of general values.

Capability of copper-nickel ferrite nanoparticles loaded onto multi-walled carbon nanotubes to degrade acid blue 113 dye in the sonophotocatalytic treatment process.

In this study, copper-nickel ferrite (CuNiFe2O4) nanoparticles were successfully loaded onto multi-walled carbon nanotubes (MWCNTs) by using the coprecipitation method and used as new catalysts (MWCNT-CuNiFe2O4) in the sonophotocatalytic degradation process of the acid blue 113 (AB113) dye. The success of the MWCNT-CuNiFe2O4 synthesis and its properties were determined by analyzing it using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). A high efficiency of dye removal (100%), total organic carbon (93%), and chemical oxygen demand (95%) were achieved with the following conditions: pH of dye solution = 5, MWCNT-CuNiFe2O4 dosage = 0.6g/L, AB113 dye concentration = 50mg/L, UV light intensity = 36W, ultrasonic wave frequency = 35kHz, and treatment time = 30min. The kinetic results revealed that the efficiency of the sonophotocatalytic process using MWCNT-CuNiFe2O4 was higher than that of the sonolysis, photolysis, photocatalysis, and sonocatalysis processes. Scavenging studies demonstrated that the holes (h+) and hydroxyl radical (•OH) were the main reactive species for the AB113 dye degradation. The stability and recyclability of MWCNT-CuNiFe2O4 were confirmed with eight consecutive cycles for a maximum efficiency of more than 92%. The high rate of BOD5/COD indicated that the sonophotocatalytic process had the potential to degrade the dye into degradable compounds. The toxicity study with an Escherichia coli growth inhibition rate emphasized that MWCNT-CuNiFe2O4 in the sonophotocatalytic degradation process of the AB113 dye had a significant effect on reducing toxicity, when compared to processes of photolysis and photocatalysis. During the sonophotocatalytic process using MWCNT-CuNiFe2O4, the AB113 dye was mineralized into CO2, H2O, NH4+, NO3-, and SO42-. The results of the present study proved that the MWCNT-CuNiFe2O4-based sonophotocatalytic process was a promising dye degradation technology to protect the aquatic environment.

Influence of Storage Conditions on the Stability of Gum Arabic and Tragacanth.

Storage conditions should be chosen so that they do not affect the action and stability of the active pharmaceutical substance (API), and excipients used in pharmacy. UV irradiation, increased temperature, and relative humidity can decompose storage substances by photolysis, thermolysis, and hydrolysis process, respectively. The effect of physical factors may be the decomposition of pharmaceutical substances or their inappropriate action, including pharmacological effects. Polymers of natural origin are increasingly used in the pharmaceutical industry. With this in mind, we evaluated the effect of storage conditions on the stability of gum arabic (GA) and tragacanth (GT). The influence of higher temperature, UV irradiation, and relative humidity on GA and GT was tested. Thermogravimetry (TG, c-DTA), colorimetric analysis, UV-Vis spectrophotometry, and optical microscopy were used as research methods. The TGA and c-DTA examination indicated that decomposition of GA starts at a higher temperature compared to GT. This indicate that gum arabic is more resistant to higher temperatures compared to tragacanth. However, the conducted analysis showed that gum arabic is more sensitive to the tested storage conditions. Among the tested physical conditions, both polymers were most sensitive to conditions of increased relative humidity in the environment.

New insight into transformation of tetracycline in presence of Mn(II): Oxidation versus photolysis

Tetracycline (TC) and Mn(II) is a common antibiotic and metal ion respectively. Nevertheless, literatures involving in the effects of Mn(II) on TC transformation are still insufficient. In this study, the kinetic experiment, spectral analysis, complexation experiment and electrochemical analysis, theoretical calculation and products detection were carried out to probe into oxidation and photolysis of TC with Mn(II). Mn(II) greatly accelerated TC oxidation, preferably tending to complex with TC at O10 – O12 or O2 – O3 site. There were a TC-Mn(II)/TC-Mn(III) redox couple and electron transfer process. Conversely, Mn(II) inhibited photolysis of TC. The photolysis of excited TC could compete with energy dissipation reactions. The electron transfer and complexation reaction easily made excited TC energy transfer, thus slowing down photolysis process. During the TC transformation, the intensity of functional groups was significantly decreased. Simultaneously, the degradation pathways mainly included eight reactions. It is a very interesting and probably overlooked phenomenon, which identifies new transformation of TC with Mn(II). This study helps to further understand fate and environmental behavior of antibiotics and metal ion.