Methanol Degradation Research Articles

Using amino acid waste liquid as functional supplement to change microbial community in up-flow anaerobic sludge blanket treatment of methanolic wastewater.

In this study, amino acid waste liquid was employed as a functional supplement (designated as amino acid-rich FS) in the up-flow anaerobic sludge blanket (UASB) treatment of methanolic wastewater. The effect of amino acid-rich FS was evaluated through repeated batch tests, showing that a 0.5% and 1% dosage increased the maximum methane production rate by 93.60% and 123.04%, respectively, by promoting faster methanol degradation. Additionally, long-term operation of the UASB reactor was conducted with increased dosages of amino acid-rich FS, resulting in improved performance. Microbial community analysis demonstrated that the addition of amino acid-rich FS enhanced microbial diversity, with the abundance of Sporomusa increasing by 47.5 times. Beyond the original cooperative relationships, an additional synergy between Sporomusa and Methanosarcina was observed. These findings could address the key challenge of limited microbial diversity in the anaerobic treatment of methanolic wastewater.

In-situ FT-IR study of alcohols degradation in the gas phase using different TiO2 composites

Herein, we present an in-situ FT-IR study analysing the interactions and photocatalytic degradation of 1-butanol and methanol in the gas phase through the catalysts Hombikat-b (commercial) and EST-1023 (synthesised in lab), as well as composites of them in a range of pH between 5 and 9. Composite Homb@EST at neutral pH (Homb@EST-pH7) has presented a photocatalytic efficiency much higher than that of the separate catalysts in both the degradation of alcohols and carboxylates. Characterisation analyses have shown that EST-1023 exhibits low surface area and surface hydroxylation, which suggests practically no adsorption of alcohols at the initial stages of the process. Notwithstanding, we have determined a large concentration of surface electronic traps in EST-1023. On the contrary, Hombikat-b presents high surface area and surface hydroxylation, leading to high adsorption rates of the studied alcohols. Aggregate distribution, SEM, and HR-TEM studies have shown that neutral pH is the most appropriate condition to aggregate both catalysts, generating the so-called composite Homb@EST-pH7. The high photocatalytic capability of this composite is attributed to the transfer of photogenerated electrons from the Hombikat-b nanoparticles to the electron traps present in EST-1023, which implies a decrease in the recombination speed of the photogenerated electron-hole (e–/h+) pairs.

Inorganic carbon as a key factor governing competition between methanogens and acetogens in high-rate anaerobic treatment of methanol wastewater

The anaerobic treatment of methanolic wastewater has become a crucial issue. Sodium bicarbonate (NaHCO3), as a typical representative of inorganic carbon substances, not only provides alkalinity in the anaerobic treatment of methanol but also governs the competition between methanogens and acetogens. However, a suitable dosage has rarely been mentioned. In this study, we demonstrate the crucial role of NaHCO3 in the anaerobic treatment of methanol using a long-term operated up-flow anaerobic sludge blanket (UASB) reactor and batch tests. The UASB results revealed that by adding 3 to 5 g/L of NaHCO3 to the influent at a high organic loading rate of 50 gCOD/L/d, a significant accumulation of acetic acid was detected, with a maximum value of up to 1400 mg/L. In the context of microbial community evolution, this study profiled substrate competition between the acetogens Acetobacterium and Methanomethylovorans, which directly utilize methanol, as well as the synergistic effects of Acetobacterium and acetoclastic Methanosaeta. Abundance analysis of genes encoding relevant pathway enzymes also revealed that the acetic acid production pathway was significantly enhanced when more NaHCO3 was added. According to the dose–response mechanism in the batch test based on kinetic analysis, an acceptable threshold prediction scheme was beneficial in reasonably adding NaHCO3 to improve acid production capacity and rapid methanol degradation, and ensuring that the generated acetate could be rapidly degraded without inhibition, in the high-rate anaerobic treatment of methanolic wastewater.

Photoelectrocatalytic Activity of ZnO-Modified Hematite Films in the Reaction of Alcohol Degradation.

Thin-film nanocrystalline hematite electrodes were fabricated by electrochemical deposition and loaded with electrodeposited zinc oxide in various amounts. Under visible light illumination, these electrodes demonstrate high activity in the photoelectrochemical degradation of methanol, ethylene glycol and, in particular, glycerol. Results of intensity-modulated photocurrent spectroscopy show that the photoelectrocatalysis efficiency is explained by the suppression of the electron-hole pair recombination and an increase in the rate of photo-induced charge transfer. Thus, zinc oxide can be considered an effective modifying additive for hematite photoanodes.

Thin-Film Nanocrystalline Zinc Oxide Photoanode Modified with CdO in Photoelectrocatalytic Degradation of Alcohols

Thin-film nanocrystalline zinc oxide electrodes were fabricated by electrochemical deposition of ZnO on FTO-coated glass slides. ZnO electrodes were promoted by CdO coating on top of ZnO in amounts corresponding to 0.8, 0.1, and 0.05 C cm−2 in electric units. Modification of ZnO by a small amount of CdO, corresponding to 0.05 C cm−2, shifts the photoactivity of the composite photoanode into the visible part of the solar spectrum. It is shown that the ZnO/(0.05C)CdO/FTO electrode demonstrates high efficiency in photoelectrochemical degradation of methanol, ethylene glycol, and glycerol when irradiated by a simulated sunlight. According to intensity-modulated photocurrent spectroscopy (IMPS), the effect is due to suppression of the electron–hole pairs recombination and increase in the rate of photo-induced charge transfer. Therefore, thin-film photoanodes based on zinc oxide modified by CdO can be used for photoelectrochemical degradation of byproducts of biofuel production glycerol, and of other alcohols.

Photo-stable, 1D-nanofilaments TiO2-based lepidocrocite for photocatalytic hydrogen production in water-methanol mixtures

•Scalable, cheap, one-pot, facile synthesis of titanium oxide-based nanofilaments •Our nanofilaments outperform commercial P25 in both activity and stability •Our discovery represents an important step for the large-scale production of green hydrogen from sunlight Water and sunlight are the cleanest, most renewable, and abundant resources on Earth. Developing inexpensive, scalable photocatalysts that are highly stable for hydrogen (H2) production has long been a cherished dream of humanity. Herein, we report on one-dimensional lepidocrocite-based sub-nanofilaments (NFs), ≈ 5 × 7 Å2 in cross-section, that generate H2 from 80:20 v/v water/methanol mixtures when illuminated by simulated sunlight. The NFs were stable in the mixtures for times >4,300 h, 300 h of which were under irradiation. Apparent quantum yields as high as 11.7% were obtained. Based on deuterated water results, we conclude that water is the H2 source. Further, no carbon dioxide (CO2) due to photocatalytic degradation of methanol was detected. Therefore, the NFs have strong green credentials and lucrative economic prospects for large scale up. We expect these NFs will lead to new lines for developing cheap and ultra-stable materials to produce H2 photochemically for a long time. Water and sunlight are the cleanest, most renewable, and abundant resources on Earth. Developing inexpensive, scalable photocatalysts that are highly stable for hydrogen (H2) production has long been a cherished dream of humanity. Herein, we report on one-dimensional lepidocrocite-based sub-nanofilaments (NFs), ≈ 5 × 7 Å2 in cross-section, that generate H2 from 80:20 v/v water/methanol mixtures when illuminated by simulated sunlight. The NFs were stable in the mixtures for times >4,300 h, 300 h of which were under irradiation. Apparent quantum yields as high as 11.7% were obtained. Based on deuterated water results, we conclude that water is the H2 source. Further, no carbon dioxide (CO2) due to photocatalytic degradation of methanol was detected. Therefore, the NFs have strong green credentials and lucrative economic prospects for large scale up. We expect these NFs will lead to new lines for developing cheap and ultra-stable materials to produce H2 photochemically for a long time.

Evaluation of feeding molar rate in mini fixed bed reactor for methanol steam reforming with pre-optimized composition of CuO/ZnO/Al2O3 catalyst

Hydrogen gas is an ideal fuel due to its higher calorific value among fuels and minimal environmental impact on their energy applications. However, the high cost around high reactivity, explosion risks and extremely low energy density, make it unfeasible to be used as fuel in large quantities scale. There are some possibilities to circumvent these limitations, including obtaining and converting energy through fuel cells, which is very promising. Research in this field has been summarized in recent decades, motivated by the environmental problems faced due to the dependence on non-renewable energy matrices. From this, this study aimed to improve the steam methanol reforming using CuO/ZnO/Al2O3 catalyst. The catalyst was characterized by atomic absorption spectroscopy, N2 physisorption and XRD. Catalytic tests were carried out in a laboratory scale fixed bed reactor at 300°C, atmospheric pressure and in differential conditions (methanol conversion < 10%); a previous run for catalyst synthesis validation in relation to the results obtained in the literature for the same conditions was evaluated. Subsequently, it was found that the thermal degradation of methanol at 300°C without the presence of the catalyst was negligible, and then operational conditions were established to obtain methanol conversions lower than 10%. Then, the initial deactivation of the catalyst over 31h. Also identifying the stability after 7 h in reaction with average conversion into 9.7% of methanol, showing high stability, in addition to good reproducibility on the part of synthesis in optimal composition. Then, experiments were carried out for the molar ratios 2:1 and 4:1 with methanol conversions of 15.5% and 6.6%, respectively. Note that performing the average of the 4:1 and 2:1 methanol conversion in 14.6% obtained at indicating that the upper boundary molar ratios (4:1) compensates for the conversion reduction in 2:1, achieving a result superior to the reference 3:1.

Low-Temperature Catalytic Ozonation of Multitype VOCs over Zeolite-Supported Catalysts.

Volatile organic compounds (VOCs) are an important source of air pollution, harmful to human health and the environment, and important precursors of secondary organic aerosols, O3 and photochemical smog. This study focused on the low-temperature catalytic oxidation and degradation of benzene, dichloroethane, methanethiol, methanol and methylamine by ozone. Benzene was used as a model compound, and a molecular sieve was selected as a catalyst carrier to prepare a series of supported active metal catalysts by impregnation. The effects of ozone on the catalytic oxidation of VOCs and catalysts' activity were studied. Taking benzene as a model compound, low-temperature ozone catalytic oxidation was conducted to explore the influence of the catalyst carrier, the active metal and the precious metal Pt on the catalytic degradation of benzene. The optimal catalyst appeared to be 0.75%Pt-10%Fe/HZSM(200). The catalytic activity and formation of the by-products methylamine, methanethiol, methanol, dichloroethane and benzene over 0.75%Pt-10%Fe/HZSM(200) were investigated. The structure, oxygen vacancy, surface properties and surface acidity of the catalysts were investigated. XRD, TEM, XPS, H2-TPR, EPR, CO2-TPD, BET, C6H6-TPD and Py-IR were combined to establish the correlation between the surface properties of the catalysts and the degradation activity.

A metabolic puzzle: Consumption of C1 compounds and thiosulfate in Hyphomicrobium denitrificans XT

Many obligately heterotrophic methylotrophs oxidize thiosulfate as an additional electron source during growth on C1 compounds. Although two different pathways of thiosulfate oxidation are implemented in Hyphomicrobium denitrificans XT, a pronounced negative effect on growth rate is observed when it is cultured in the simultaneous presence of methanol and thiosulfate. In this model organism, periplasmic thiosulfate dehydrogenase TsdA catalyzes formation of the dead-end product tetrathionate. By reverse genetics we verified the second pathway that also starts in the periplasm where SoxXA catalyzes the oxidative fusion of thiosulfate to SoxYZ, from which sulfate is released by SoxB. Sulfane sulfur is then further oxidized in the cytoplasm by the sulfur-oxidizing heterodisulfide reductase-like system (sHdr) which is produced constitutively in a strain lacking the transcriptional repressor sHdrR. When exposed to thiosulfate, the ΔshdrR strain exhibited a strongly reduced growth rate even without thiosulfate in the pre-cultures. When grown on methanol, cells exhibit significantly increased NAD+/NADH ratios in the presence of thiosulfate. In contrast, thiosulfate did not exert any negative effect on growth rate or increase NAD+ levels during growth on formate. On both C1 substrates, excretion of up to 0.5 mM sulfite as an intermediate of thiosulfate (2 mM) oxidation was recorded. Sulfite is known to form adducts with pyrroloquinoline quinone, the cofactor of periplasmic methanol dehydrogenase. We rationalize that this causes specific inhibition of methanol degradation in the presence of thiosulfate while formate metabolism in the cytoplasm remains unaffected.

Alkali Etching Induced CoAl‐Layered Double Oxides with Regulatable Cation and Oxygen Vacancy Defects to Promote the Photothermal Degradation of Methanol

AbstractBy controlling the alkali etching time, the cation and oxygen vacancies contents of CoAl‐LDHs were adjusted. Then CoAl‐layered double oxides catalysts (CoAl‐LDOs‐x) were prepared by calcination and applied to the photothermal catalytic degradation of methanol and acetone under the full spectrum simulated solar illumination. Compared with CoAl‐LDOs‐0 without alkali etching, CoAl‐LDOs‐9 with alkali etching for 9 h showed the most superior photothermal catalytic activity and excellent stability. A series of studies had suggested that the most superior activity of the catalyst could be ascribed to the cation vacancy produced by alkali etching, resulting in more Co3+ active sites on the surface. At the same time, alkali etching also produced oxygen vacancy, which accelerated the adsorption and conversion of surface reactive oxygen species (ROS). In addition, the activation effect of light on lattice oxygen and gas phase oxygen was proved by in‐situ DRIFTS, and the degradation path of methanol was clarified.

The nature of gas production patterns associated with methanol degradation in natural aquifer sediments: A microcosm study

With growing global use of methanol as a fuel additive and extensive use in other industrial processes, there is the potential for unintended release and spills into soils and aquifers. In these subsurface systems it is likely that methanol will be readily biodegraded; however, degradation may lead to the production of by-products, most importantly methane possibly resulting in explosion hazards and volatile fatty acids (VFAs) causing aesthetic issues for groundwater. In this study, the formation of these potentially harmful by-products due to methanol biodegradation was investigated in natural sand and silt sediments using microcosms inoculated with neat methanol (100%) ranging in concentration from 100 to 100,000 ppm. To assess the rate of degradation and by-product formation, water and headspace samples were collected and analyzed for methanol, volatile fatty acids (VFAs, including acetic, butyric, and propionic acid), cation (metal) concentrations (Al, Ca, Fe, K, Mg, Mn and Na), microbial community structure and activity, headspace pressure, gas composition (CH4, CO2, O2 and N2), and compound specific isotopes. Methanol was completely biodegraded in sand and silt up to concentrations of 1000 ppm and 10,000 ppm, respectively. Degradation was initially aerobic, consuming oxygen (O2) and producing carbon dioxide (CO2). When O2 was depleted, the microcosms became anaerobic and a lag in methanol degradation occurred (ranging from 41 to 87 days). Following this lag, methanol was preferentially degraded to acetate, coupled with CO2 reduction. Microcosms with high methanol concentrations (10,000 ppm) were driven further down the redox ladder and exhibited fermentation, leading to concurrent acetate and methane (CH4) generation. In all cases acetate was an intermediate product, further degraded to the final products of CH4 and CO2. Carbonates present in the microcosm sediments helped buffer VFA acidification and replenished CO2. Methane generation in the anaerobic microcosms was short-lived, but temporarily reached high rates up to 13 mg kg−1 day−1. Under the conditions of these experiments, methanol degradation occurred rapidly, after initial lag periods, which were a function of methanol concentration and sediment type. Our experiment also showed that methanol degradation and associated methane production can occur in a stepwise fashion.

Synergistic effect of tunable oxygen-vacancy defects and graphene on accelerating the photothermal degradation of methanol over Co3O4/rGO nanocomposites

A series of Co3O4/rGO (reduced graphene oxide) nanocomposites with tunable oxygen vacancy defect concentrations were synthesized via a simple alkali etching and applied for photothermal degradation of methanol. In the samples without alkali etching, the Co3O4/rGO nanocomposite showed higher photothermal catalytic performance than Co3O4 due to the thermal auxiliary effect of rGO. Among the Co3O4/rGO nanocomposites, the nanocomposite etched by 0.64 g NaOH (denoted as Co3O4/rGO-N0.64) exhibited the highest photothermal catalytic performance (methanol conversion of 96%, CO2 yield of 91%) as well as excellent durability under the solar irradiation. The superior activity was mainly attributed to the synergistic effect of the thermal auxiliary effect of rGO and the abundant oxygen vacancy defects. The reaction mechanism confirmed that both of gas phase oxygen and lattice oxygen were activated and participated in this reaction process. The enrichment of oxygen vacancy defects in Co3O4/rGO-N0.64 can boost the circulation of oxygen species, which played a crucial role in the continuous and effective photothermal catalytic oxidation of methanol.

Methanol degradation mechanisms and permeability phenomena in novolac epoxy and polyurethane coatings

On a global scale, methanol is one of the most important feedstocks and is used widely as solvent and co-solvent. However, due to the polar nature and associated ability to conduct current, the small molecule can take part in galvanic corrosion of metal storage tanks and degrade the barrier properties of protective coatings. In the present work, we investigated the degradation of two novolac epoxy coatings and a polyurethane (PU) coating exposed to methanol with the aim of quantifying the various degradation paths. Absorption and desorption rates were measured and the thermomechanical properties followed by dynamic mechanical analysis. For evaluation of the coating barrier properties (i.e., breakthrough time and steady state permeation rates of methanol), permeation cells were applied. During methanol absorption, simultaneous leaching of certain coating ingredients and bonding of methanol to the binder matrix via hydrogen bonds was evidenced. In terms of classification, the bonding of methanol took place by two types of mechanisms. In Type I, the methanol molecule forms a single hydrogen bond to the coating network, thereby acting as a plasticizer, which decreases the coating storage modulus and glass transition temperature. For Type II bonding of methanol, on the other hand, two hydrogen bonds to the coating network form per molecule, resulting in so-called physical crosslinking. The Type I mechanism boosted segmental mobility and contributed to the leaching of the plasticizer benzyl alcohol from the novolac epoxy coatings and residual solvents (i.e., naphtha and xylene) from the PU coating. Following the methanol desorption, and attributed to an increased effective crosslinking density from Type II bound methanol, the novolac epoxy and PU coatings exhibited significant increases in the glass transition temperatures. In addition, for the three coatings, a gradual decline in the permeability rate of methanol was observed over time. These enhanced (and unexpected) barrier properties result from a combination of effects ascribed to Type II bound methanol and the leaching process.

Physiological, genomic, and sulfur isotopic characterization of methanol metabolism by Desulfovibrio carbinolicus.

Methanol is often considered as a non-competitive substrate for methanogenic archaea, but an increasing number of sulfate-reducing microorganisms (SRMs) have been reported to be capable of respiring with methanol as an electron donor. A better understanding of the fate of methanol in natural or artificial anaerobic systems thus requires knowledge of the methanol dissimilation by SRMs. In this study, we describe the growth kinetics and sulfur isotope effects of Desulfovibrio carbinolicus, a methanol-oxidizing sulfate-reducing deltaproteobacterium, together with its genome sequence and annotation. D. carbinolicus can grow with a series of alcohols from methanol to butanol. Compared to longer-chain alcohols, however, specific growth and respiration rates decrease by several fold with methanol as an electron donor. Larger sulfur isotope fractionation accompanies slowed growth kinetics, indicating low chemical potential at terminal reductive steps of respiration. In a medium containing both ethanol and methanol, D. carbinolicus does not consume methanol even after the cessation of growth on ethanol. Among the two known methanol dissimilatory systems, the genome of D. carbinolicus contains the genes coding for alcohol dehydrogenase but lacks enzymes analogous to methanol methyltransferase. We analyzed the genomes of 52 additional species of sulfate-reducing bacteria that have been tested for methanol oxidation. There is no apparent relationship between phylogeny and methanol metabolizing capacity, but most gram-negative methanol oxidizers grow poorly, and none carry homologs for methyltransferase (mtaB). Although the amount of available data is limited, it is notable that more than half of the known gram-positive methanol oxidizers have both enzymatic systems, showing enhanced growth relative to the SRMs containing only alcohol dehydrogenase genes. Thus, physiological, genomic, and sulfur isotopic results suggest that D. carbinolicus and close relatives have the ability to metabolize methanol but likely play a limited role in methanol degradation in most natural environments.

Mechanistic insights into photogenerated electrons store-and-discharge in hydrogenated glucose template synthesized Pt: TiO2/WO3 photocatalyst for the round-the-clock decomposition of methanol

This study demonstrates the glucose-template assisted synthesis of hydrogen-treated Pt: TiO2/WO3 composites, and their round-the-clock photoactivity towards methanol (MeOH) degradation under light illumination and in dark. XRD indicated increasing rutile fraction in TiO2 as a function of template removal, WO3 crystallinity and H2 treatment process. The presence of oxygen vacancies in WO3 was confirmed by XPS. Lower recombination rate and higher surface area were observed in the optimized H2-Pt-G:TiO2/WO3 catalyst. The presence of oxygen vacancies and optical enhancements due to the synergistic interactions of the multi-system (TiO2, WO3 and Pt) extended the visible light absorption of the system, increasing photocatalytic activity, with 61 % of MeOH degradation in 2 h of irradiation and 33 % in dark in 6 h. The origin of the observed efficiency was further validated using photo-electrochemical investigations, which revealed appropriate interfacial contacts in Pt: TiO2/WO3 system, maximum charge separation and charge transfer thanks to oxygen vacancies.

Colony, morphological and biochemical characteristics of cotton phyllosphere bacteria and its antagonistic activity against the Alternaria leaf spot of cotton

Cotton crop is known to suffer from number of fungal, bacterial and viral diseases. Among them, Alternaria leaf spot caused by Alternaria spp. is predominant in causing economic losses to the cotton crop in the country. Phyllosphere inhabitants termed as epiphytes may consists of a variety of bacteria and filamentous fungi. They also play a key role in carbon and nitrogen cycling and help in important environmental processes such as methanol degradation and nitrification. So, bacterial phyllosphere cultures (P1 to P8) were isolated from the Bt and non Bt cotton by leaf imprint method and dilution method. The colony characters of isolates of bacteria pertaining to their shape, size, elevation, margin, texture, appearance and pigmentation were recorded. Gram’s staining and endospore staining revealed that P1, P2, P3, P5, P8 were Gram positive, P1, P2, P5 were showing endospore staining and P1, P4, P6, P7 were rod shaped. Biochemical tests revealed that the eight isolates Bt and non Bt cotton were differed in each test and showed positive for the catalase and oxidase test. The isolates P1, P5 and P6 showed positive results to Voges proskauer test. Isolates P2, P4 and P6 revealed positive results of phyllosphere bacteria to Indole test. Whereas, isolates P1, P2 and P8 showed negative reaction to methyl red test. The phyllosphere bacterial isolates P3, P5 and P7 recorded negative reaction to gelatin liquefaction. Screening of phyllosphere microflora against Alternaria macrospora was conducted following dual culture technique for all the isolates. Phyllosphere bacterial isolate P5 recorded maximum growth inhibition with 57.41 per cent followed by P4 isolate with 53.52 per cent growth inhibition over the test fungus Alternaria macrospora. Whereas least per cent growth inhibition was reported in isolate P6 with 45.63 per cent.

Removal of toluene in a biotrickling filter in the presence of methanol vapors: Experimental study, mathematical modeling, and kinetic parameters optimization

The performance of biotrickling filters (BTFs) has been significantly affected during the co-treatment of volatile organic compounds (VOCs) with different hydrophilicities. Removal of toluene vapor as a hydrophobic compound in the absence and presence of methanol as a hydrophilic pollutant was studied in a BTF. The inlet loading ranges were 18−36 g.m−3.h−1 for toluene and 0−225 g.m−3.h−1 for methanol at constant empty bed residence time (EBRT) of 60 s. The removal efficiency of toluene (RET) varied from 30 to 80 %, while RE of methanol (REM) remained almost constant at > 90 % within different phases of experiments due to the unlimited solubility in water. A comprehensive dynamic mathematical model consisting of mass transfer through gas, liquid, and biofilm phases with the kinetic of biodegradation in the BTF and accumulation of methanol in liquid was developed. The interaction parameters were optimized by genetic algorithm and validated by experimental data. Sensitivity analysis on the optimized parameters showed that biofilm thickness and methanol interaction parameter had the most effects on RET as 45 % and 38 %, respectively. Model simulation showed that 43–90 % of biofilm depth was active for toluene degradation at different inlet gas-phase concentrations, indicating a diffusion-limited condition in the process. In contrast, all depth of biofilm was fully active for methanol degradation, showing a kinetic-limited regime dominant for methanol removal in the BTF under all operating conditions. Results showed that the developed model could effectively predict the dynamics of VOCs removals along with the determination of kinetic constants.

Electrospun Active Media Based on Polyvinylidene Fluoride (PVDF)-Graphene-TiO2 Nanocomposite Materials for Methanol and Acetaldehyde Gas-Phase Abatement

The abatement of organic pollutants by TiO2 photocatalysis has been established as one of the benchmark applications of advanced oxidation processes for both liquid and gas phase purification. Such solution is particularly suitable for indoor air pollution where volatile organic compounds (VOCs) represent a class of chemicals of high concern for their adverse effects on both environment and human health. However, different shortcomings still affects TiO2 photocatalytic performance in terms of weak adsorptivity and fast electron-hole recombination, limiting its applicability. As a result, different strategies have been investigated over the last years in order to promote a higher TiO2 photo-efficiency. In this study we used electrospun (PVDF) nanofibers as a support for the photo catalytic system obtained by coupling graphene based materials and TiO2 during solvothermal synthesis. The resultant nanostructured membranes have been tested for acetaldehyde and methanol degradation under UV light showing an increase in the photocatalytic activity compared to bare TiO2. Such results may be ascribed to the decrease of band-gap energy and to increased electron mobility in the photocatalytic nanocomposite.

Flow-mode water treatment under simultaneous hydrodynamic cavitation and plasma

Over the last two decades, the scientific community and industry have made huge efforts to develop environmental protection technologies. In particular, the scarcity of drinking water has prompted the investigation of several physico-chemical treatments, and synergistic effects have been observed in hyphenated techniques. Herein, we report the first example of water treatment under simultaneous hydrodynamic cavitation and plasma discharge with the intense generation of radicals, UV light, shock waves and charged particles. This highly reactive environment is well suited to the bulk treatment of polluted water (i.e. E. coli disinfection and organic pollutant degradation). We have developed a new prototype and have efficiently applied this hybrid technology to water disinfection and the complete degradation of methanol in water with the aim of demonstrating its scalability. We have analyzed the mechanisms of water disinfection under the abovementioned conditions and verified them by measuring cavitation noise spectra and plasma emission spectra. We have also used the degradation of textile dyes and methanol solutions as an indicator for the formation of radicals.

Enhanced hydrogen generation efficiency of methanol using dielectric barrier discharge plasma methodology and conducting sea water as an electrode

In this work, methanol decomposition method has been discussed for the production of hydrogen gas with the application of plasma. A simple dielectric barrier discharge (DBD) plasma reactor was designed for this purpose with two types of electrode. The DBD plasma reactor was experimented by substituting one of the metal electrodes with feebly conducting sea water which yielded better efficiency in producing hydrogen gas. Experimental parameters such as; discharge voltage and time were varied by maintaining a discharge gap of 1.5 mm and the plasma discharge characteristics were studied. Filamentary type micro-discharges were found to be formed which was observed as numerous streamer clusters in the current waveform. Gas chromatographic study confirmed the production of hydrogen gas with residence time around 3.6 min. Although, the concentration (%) of H2 was high (98.1 %) and consistent with copper electrode assembly, the rate of formation and concentration was found to be the highest (98.7 %) for water electrode for specific discharge voltage. The energy efficiency was found to be 0.5 mol H2/kWh and 1.2 mol H2/kWh for metal (Cu) and water electrodes respectively. The electrode material significantly affects the plasma condition and hence the rate of hydrogen production. Compositional analysis of the water used as electrode showed a minimal change in the composition even after the completion of the experiment as compared to the untreated water. Methanol degradation study shows the presence of untreated methanol in the residue of the plasma reactor which has been confirmed from the absorption spectra.