Decomposition Of Organic Compounds Research Articles

The Role of Hydrocarbons in the Genesis of Mississippi-Valley-Type (MVT) Zn–Pb Deposits: Insights from In Situ Sulfur Isotopes of Sphalerite from the Southwestern Margin of the Yangtze Block, SW China

The coexistence of numerous Mississippi-Valley-type (MVT) Zn–Pb deposits and (paleo) oil/gas reservoirs in the world suggests a close genetic relationship between mineralization and hydrocarbon accumulation. Xuequ–Shandouya middle MVT Zn–Pb deposits are mainly hosted in the Lower Cambrian Maidiping Member siliceous dolostone on the southwestern margin of the Yangtze Block, accompanied by large amount of bitumen in the orebodies. Therefore, this type of Zn–Pb deposit is a natural laboratory for studying the relationship between the mineralization and the accumulation of paleo-oil/gas reservoirs. The deposit is characterized by spheroidal and concentric banded sphalerite. In situ sulfur isotope studies are carried out to determine the sulfur sources, sulfate reduction mechanisms, and role of hydrocarbons in the zinc–lead mineralization process. According to the mineral paragenesis and relative temporal relationship, two mineralization stages (1 and 2) are identified. An in situ sulfur isotope analysis of spheroidal and concentric banded sphalerite particles from Stage 2 shows that there are the two following types of sulfur isotopes in the sphalerite: one with relatively invariable δ34S values in the core (+8.31 to +9.30‰), and the other with a gradual increase from the core margin (core) to the rim (+0.39 to +16.18‰). These two types reflect that they may have formed in different times, with first type forming in the early period of Stage 2, while the second type was formed in the late period of Stage 2. The sulfur isotopic data suggest the sulfur source of evaporated sulfate minerals and multiple formation mechanisms for reduced sulfur (H2S). In the early period of Stage 2 mineralization, the sulfate reduction mechanism is mainly a mixture of bacterial sulfate reduction (BSR) and/or thermochemical sulfate reduction (TSR), while a very small amount may come from the thermal decomposition of organic compounds (DOCs). In the late period of Stage 2, TSR is dominant, and the gradual increase in the δ34S value may be related to Rayleigh fractionation. The oil/gasreservoir not only acts as a reducing agent to provide the required hydrogen sulfide for zinc–lead mineralization through TSR or BSR, but also provides reduced sulfur for mineralization through the thermal decomposition of organic compounds directly.

Synergetic effect of Fe decorated MnO2 nanocatalyst application in propane and benzyl alcohol oxidation

In heterogeneous catalysis, one of the key challenges is to develop inexpensive and abundant materials. Herein, spherically shaped α–Fe2O3 nanoparticles decorated over MnO2 nanorods surface (Fe/MnO2NRs) was synthesized via hydrothermal followed by co–precipitation methods. Experimental results indicated that the inclusion of Fe in MnO2NRs promotes a strong interaction that increases the reducibility of Mn4+ to Mn3+ and surface adsorbed oxygen (Oads.), which in turn increases the activation of surface oxygen on MnO2NRs. The 10 wt% Fe–loaded catalyst (10Fe/MnO2NRs) exhibited the highest catalytic activity. It was observed that oxidizing 10 % (T10), 50 % (T50), and 90 % (T90) of propane required temperatures of 140 °C, 180 °C, and 220 °C, respectively. This catalyst showed stability in H2O atmospheres and apparent activation energy as low as 52.54 kJ mol−1. In addition, the vapour phase oxidation of benzyl alcohol (BnOH) over different Fe–loaded MnO2NRs catalysts is investigated. The rate of BnOH oxidation over 10Fe/MnO2NRs catalyst is 1.71 times greater than bare MnO2NRs at 240 °C. The increased oxygen vacancies can improve the oxidation activity of propane and BnOH by facilitating the adsorption and activation of O2 to produce reactive oxygen species. This work offers a novel approach to increase manganese oxides surface oxygen activity, which can be used to create efficient catalysts for the low–temperature decomposition of volatile organic compounds (VOCs) and other organic functional group transformations via oxidation reaction.

Evaluating the efficacy of microalgal-bacterial granular sludge system in lake water remediation.

The microalgal-bacterial granular sludge (MBGS) process is attracting attention as a green wastewater treatment technology. However, research on the application of MBGS in lake water remediation is limited. Thus, this experiment investigated the feasibility and the efficacy of the MBGS process for the treatment of natural lake water in a continuous-flow tubular reactor. The averageremoval efficiencies of COD, NH4+-N, NO3--N, NO2--N, TN, PO43--P, TP, and turbidity by MBGS system in the day/night cycles were 50.10/61.39%, 63.52/75.23%, 43.37/73.57%, 90.72/93.48%, 78.30/80.02%, 71.13/74.62%, 65.08/70.57%, 92.32/89.84%, respectively. As the experiment progressed, the total chlorophyll content in MBGS decreased as the granule size increased, while the extracellular polymeric substances content increased, suggesting that thelake water contributed to bacterial growth and favored the stability of MBGS. Moreover, the eukaryotic microorganisms were dominated by Chlorophyta and Rotifera, and prokaryotic microorganisms were dominated by Proteobacteria in MBGS. By promoting the decomposition of various organic compounds in the lake water and inhibiting sludge expansion, these microorganisms helpthe MBGS system tomaintain excellent granular characteristics and performance. Overall, the MBGS system proved to be a feasible option for the remediation of natural lake waters.

Enhanced TiO2-Based Photocatalytic Volatile Organic Compound Decomposition Combined with Ultrasonic Atomization in the Co-Presence of Carbon Black and Heavy Metal Nanoparticles.

Volatile organic compounds (VOCs) are representative indoor air pollutants that negatively affect the human body owing to their toxicity. One of the most promising methods for VOC removal is photocatalytic degradation using TiO2. In this study, the addition of carbon black (CB) and heavy metal nanoparticles (NPs) was investigated to improve the efficiency of a TiO2-based photocatalytic VOC decomposition system combined with ultrasonic atomization and ultraviolet irradiation, as described previously. The addition of CB and Ag NPs significantly improved the degradation efficiency. A comparison with other heavy metal nanoparticles and their respective roles are discussed.

The phosphate-solubilising fungi in sustainable agriculture: unleashing the potential of fungal biofertilisers for plant growth.

Phosphate-solubilising fungi (PSF) are beneficial microorganisms that play a pivotal role in plant growth by increasing the availability of phosphorus (P) in soil. Although phosphorus is an essential nutrient for plants, it often becomes inaccessible as it binds into insoluble forms. PSF effectively facilitate the release of this bound phosphorus through diverse mechanisms. Numerous fungal species demonstrate the ability to solubilise various types of phosphate compounds. Among the commonly researched PSF are Penicillium, Aspergillus, Rhizopus, Fusarium, Trichoderma, and Sclerotium. Moreover, yeasts such as Saccharomyces cerevisiae can potentially be leveraged as PSF. PSF secrete organic acids that chelate phosphate ions, thereby increasing their solubility in the soil. Moreover, PSF contribute to the decomposition of organic phosphorus compounds in soil by employing enzymes such as phosphatases, phytases, and phosphonatases. Furthermore, PSF can interact with other soil microorganisms, including nitrogen-fixing bacteria and arbuscular mycorrhizal fungi (AM-fungi), fostering synergistic effects that further enhance plant growth and nutrient absorption. The utilisation of PSF as biofertilisers offers numerous advantages over chemical fertilisers, including environmental friendliness, cost-effectiveness, and enhanced fertiliser utilisation efficiency. Furthermore, PSF can prove beneficial in challenging environments characterised by high phosphate sorption. Hence, this review serves as an updated study aimed at broadening the understanding of PSF and its potential applications in P solubilisation. This review also focuses on the diversity of PSF, the mechanisms underlying solubilisation, ecological roles of PSF in soil microbiome, and the benefits of sustainable agriculture. By delving into the ecological roles of PSF and their potential as biofertilisers, this study contributes to a deeper understanding of sustainable agriculture practices and addresses challenges in phosphate-scarce environments.

EFFECT OF HOLDING TIME ON EXTRACTION OF NATURAL HYDROXYAPATITE FROM GOAT BONE WASTE FOR BIOMEDICAL APPLICATIONS

Hydroxyapatite (HAP) is a very essential biomaterial used in orthopedics and dentistry to support bone healing processes as it shares chemical similarities with natural human and animal bones. Extraction of hydroxyapatite has been done both synthetically and naturally from animal bones. However, extraction of HAP from natural sources is challenged by the appropriate choice of processing parameters such as holding time and temperature that will enable the production of hydroxyapatite that meets the standard. This work investigated the influence of varying holding time on the physico-chemical properties of HAP obtained from goat bone (GB) waste by heat treatment. GB femur was obtained; washed; dried; pulverized and sieved to obtain GB powder of ≤ 500 µm that was calcined at 900°C and 1000°C and soaked for 1hr., 2 hrs. and 3 hrs. The composition, structure and morphology of the uncalcined and calcined powders were studied using Fourier Transform Infra-Red Spectroscopy (FTIR), X-ray diffractometry (XRD) and scanning electron microscopy (SEM), respectively. The FITR result confirmed presence of associated functional groups consisting of phosphate ions (PO43−), hydroxyl ions (OH−) and carbonate (CO32- ) ions in the synthesized HAP, but the phosphate ions (PO43−) were most prominent. XRD analysis revealed similar crystallographic peaks of pure HAP. Increase in holding time led to decrease in crystallinity. SEM analysis revealed changes in the morphology of the samples with increase in holding time and temperature due to decomposition of organic compounds in calcined GB. The surface morphologies became finer with increase in holding time. Thus, holding time is an important parameter in extraction of HAP from goat bone waste.

Systematic Review of Poultry Slaughterhouse Wastewater Treatment: Unveiling the Potential of Nanobubble Technology

Aeration is crucial for the biological decomposition of organic compounds in wastewater treatment. However, it is a highly energy-intensive process in traditional activated sludge systems, accounting for 50% to 75% of a plant’s electricity consumption and making it a major cost driver for wastewater treatment plants. Nanobubbles (NBs), characterized by their tiny size with diameters less than 200 nm, have emerged as a potential alternative to the low efficiency of aeration and high sludge production in aeration systems. NBs proved effective in removing COD and other pollutants from wastewater. For example, when applied in flotation, aeration, and advanced oxidation, NBs achieved up to 95%, 85%, and 92.5% COD removal, respectively. Considering the recent advancements in wastewater treatment, a compelling need arises for a thorough investigation of the effectiveness and mechanisms of nanobubbles in this field. This systematic review summarizes recent advancements in understanding nanobubbles (NBs) and their unique properties that enhance physical, chemical, and biological water and wastewater treatment processes. Moreover, this study reviews various methods for generating NBs and provides an in-depth review of their applications in wastewater treatment, with a particular focus on poultry slaughterhouse wastewater (PSW) treatment.

Boosting visible-light response for the complete decomposition of volatile organic compounds on the Cu-oxide deposited WO3 photocatalyst by the synergistic effects of TiO2

The degradation of volatile organic compounds (VOCs) by photocatalytic systems is the most practical strategy due to its cost performance, simplicity, and environmental sustainability. To address such issues, the photocatalytic activities of tungsten trioxide (WO3) were developed by the deposition of various cocatalysts. In particular, the Cu-oxide (CuO/Cu2O)-deposited WO3 (Cu-WO3) photocatalyst could efficiently decompose acetic acid and acetaldehyde into CO2 under visible-light irradiation, although it exhibited low activity for the decomposition of benzene, toluene and xylene (BTX). Furthermore, a composite Cu-WO3/TiO2 photocatalytic system, which was fabricated by the simple physical mixing of Cu-WO3 with TiO2, was found to exhibit unprecedented reactivity for the complete decomposition of persistent BTX pollutants into CO2 under visible light irradiation. The synergistic effects of Cu-WO3 and the interfacial surface complex (ISC) formed by toluene-adsorbed TiO2 contribute to the efficient visible light response by excitation up to around 600 nm. The reaction mechanism for the enhancement of photocatalytic activity by the Cu-WO3/TiO2 composite photocatalyst is examined in this study.

Efficient biological treatment: Achieving exceptional reductions in pollutants and ensuring environmental compliance

The study assessed the effectiveness of treatment processes in removing organic matter, biogenic compounds and suspended solids at the subsequent treatment stages one of the Polish municipal wastewater treatment plant. In a comprehensive mechanical-biological treatment, for all tested pollution indicators, i.e. biochemical oxygen demand (BOD5), chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP) and total suspended solids (TSS), outstanding results, surpassing regulatory standards, were obtained. The achieved average percentage reduction was from 87 % for TN (standard deviation of 2.7 %) to average 99 % for BOD5 (standard deviation of 0.3 %). The observed average BOD5/COD ratio of 0.45 aligned with typical values reported, and the decrease in the ratio to 0.13 after biological treatment underscored the efficacy of these processes in organic compounds decomposition and managing difficult-to-degrade substances. The BOD5/TN values emphasized the effectiveness of the treatment, maintaining well-balanced proportions between organic carbon and nitrogen compounds. Moreover, raw sewage showed notable susceptibility to nitrogen removal, indicated by the highest average BOD5/TN ratio of 6.72, suggesting a high propensity for biodegradation. This study highlighted that the average BOD5/TP value of 56 in raw sewage indicated a significant susceptibility to phosphorus compound removal. The treated sewage consistently adhered to environmental regulations, demonstrating minimal variability in pollution indicators. That underscored the effectiveness of treatment processes in meeting stringent standards and achieving significant reductions in pollutants. Effective sewage treatment is even more significant, because it is possible to reuse treated sewage e.g. for irrigation in agriculture, what contributes to the sustainable water management.

Soil nitrogen and phosphorus regulate decomposition of organic nitrogen compounds in the rothamsted experiment

The effects of long-term N and P fertilisation on soil organic nitrogen (SON) turnover are unclear. We sampled soils fertilised by N and/or P since 1843 at Rothamsted Research to investigate the effects of long-term N and P fertilisation on high- or low-molecular-weight SON decomposition and gross N mineralisation. Short-term assays with added 14C-labelled proteins, peptides, and amino acids and gross organic N mineralisation were measured, and the microbial communities and functions were also assessed in parallel. Long-term N fertilisation increased the contents of soil extractable organic N and peptides but decreased organic N-hydrolysing enzyme activities (N-acetyl-β-D-glucosaminidase and leucine aminopeptidase). Fertilisation with P and N accelerated and reduced the decomposition of 14C-labelled organic N compounds, respectively. The decomposition of peptides and amino acids, as labile SON components, was mainly regulated by soil P content because microbial biomass and activity were more sensitive to P fertilisation than to N fertilisation. Gross NH4+/NO3− production and consumption were accelerated by 41%–60% under N fertilisation but remained unchanged under P fertilisation compared to the unfertilised treatment. Metagenomic sequencing showed that N fertilisation increased microbial diversity and enriched functional genes associated with organic N decomposition, compared to the unfertilised treatment. P fertilisation had no effect on the abundance of these functional genes. In agricultural practices, it is essential to comprehensively consider the interaction between N and P fertilisation to optimise the cycling and utilisation of SON.

Aerobic composting characteristics of corn straw and pig manure under dynamic aeration

ABSTRACT The conventional aeration method is compulsorily continuous ventilation or aeration at equal intervals, and a uniform aeration rate does not vary during composting. A dynamic on-demand aeration approach based on the diverse oxygen consumption of microorganisms at different composting stages could solve the problems of insufficient oxygen supply or excessive aeration. This study aims to design an aerobic composting system with dynamic aeration, investigate the effects of dynamic aeration on the temperature rise and physicochemical characteristics during the aerobic composting of corn straw and pig manure, and optimise the control parameters of oxygen concentration. Higher temperatures and longer high-temperature durations were achieved under dynamic aeration, thereby accelerating the decomposition of organic compounds. Dynamic aeration effectively reduced the aeration frequency, the convective latent heat and moisture losses, and the power consumption in the middle and later stages of composting. The dynamic aeration regulated according to the oxygen concentration of 14%–17% in the exhaust was optimum. Under the optimal conditions, the period above 50 ℃ lasted 8.5 days, and the highest temperature, organic matter removal, and seed germination index reached 65.82 ℃, 37.59%, and 74.59%, respectively. The power consumption was decreased by 33.58% compared to the traditional intermittent aeration. Dynamic aeration would be a competitive approach for improving aerobic composting characteristics and reducing the power consumption and the hot exhaust gas emissions, especially in the cooling maturation stage, which was of great significance for realising the low-cost production of composting at scale and promoting the blossom of the organic fertiliser industry.

Biogeochemical traces and microbe-mineral interactions in the hyperarid core of the Atacama Desert

Life found various ways to thrive in hostile desert environments. Common adaptation mechanisms are protection against desiccation and UV radiation in biofilms and biocrusts as well as the hypolithic and endolithic colonization of rocks. One of those hostile regions is the Atacama Desert in Northern Chile with its hyperarid core, counted among the most arid places on Earth. Besides the aridity, life faces severe restrictions in these surroundings, e.g. extremely high UV radiation, scarce nutrient supply, and immense salt concentrations. Still, microbial communities and soil organic matter are crucial for the stability of soils and surface sediments in arid ecosystems. Combining molecular mass spectrometry for lipid biomarkers, scanning electron microscopy, and nuclear magnetic resonance spectroscopy, we individually investigated two factors that are of particular importance for the stability of dryland landscapes now and in the future: 1) We studied biogeochemical traces (organic remnants) in surface sediments along an aridity gradient with regard to possible decomposition and/or sequestration of organic compounds. 2) We investigated the interaction of lithobiontic and endolithic microbial communities with the mineral surface with special regard to the stability of soil and surface sediment structures in different areas of the Atacama Desert: in the region of the Salar Grande, Pisagua, and the Quebrada da Aroma. We analyzed halite- and calcium sulfate-dominated evaporitic crusts with and without visible microbial colonization. Organic traces were present in all investigated samples. Following an aridity gradient along the Quebrada de Aroma from an annual precipitation of about 20 mm to the hyperarid core with approx. 2 mm, we found a decrease in functionalized molecular compounds and plant-derived biomarkers (long-chain fatty acids, sterols) as well as an increase in aromatic hydrocarbons, indicating strongly decomposed remnants of plants and microorganisms. The investigation of halite- and calcium sulfate-dominated evaporitic crusts from the Salar Grande, Pisagua, and Aroma region revealed tight interactions of microorganisms with the mineral substrate. Indications of recent bacterial activity were ubiquitous (e.g. short-chain membrane fatty acids, carbohydrates of extracellular polymeric substances (EPS)). Scanning electron microscopy revealed that especially the microbial EPS within evaporites seems to biochemically stabilize mineral aggregates by agglutination. Moreover, fungal biomarkers showed that fungi and fungal parts of lichen were not only present at the surface of physical soil crusts but form widespread networks in the crusts and thereby contribute significantly to the physical stabilization of soils and surface sediments and erosion protection.

Novel nanostructure approach for antibiotic decomposition in a spinning disc photocatalytic reactor

Conventional wastewater treatment processes are often unable to remove antibiotics with resistant compounds and low biological degradation. The need for advanced and sustainable technologies to remove antibiotics from water sources seems essential. In this regard, the effectiveness of a spinning disc photocatalytic reactor (SDPR) equipped with a visible light-activated Fe3O4@SiO2-NH2@CuO/ZnO core–shell (FSNCZ CS) thin film photocatalyst was investigated for the decomposition of amoxicillin (AMX), a representative antibiotic. Various characterization techniques, such as TEM, FESEM, EDX, AFM, XRD, and UV–Vis-DRS, were employed to study the surface morphology, optoelectronic properties, and nanostructure of the FSNCZ CS. Key operating parameters such as irradiation time, pH, initial AMX concentration, rotational speed, and solution flow rate were fine-tuned for optimization. The results indicated that the highest AMX decomposition (98.7%) was attained under optimal conditions of 60 min of irradiation time, a rotational speed of 350 rpm, a solution flow rate of 0.9 L/min, pH of 5, and an initial AMX concentration of 20 mg/L. Moreover, during the 60 min irradiation time, more than 69.95% of chemical oxygen demand and 61.2% of total organic carbon were removed. After the photocatalytic decomposition of AMX, there is a substantial increase in the average oxidation state and carbon oxidation state in SDPR from 1.33 to 1.94 and 3.2, respectively. Active species tests confirmed that ·OH and ·O2− played a dominant role in AMX decomposition. The developed SDPR, which incorporates a reusable and robust FSNCZ CS photocatalyst, demonstrates promising potential for the decomposition of organic compounds.

Effect of substitution on thermal decomposition of formaldehyde: A theoretical study

Unimolecular decomposition of organic compounds is strongly influenced by substituted functional group. The present work focusses to explore the energetics and kinetics of unimolecular decomposition of formaldehyde and chloro- substituted formaldehydes. Dissociation of molecular systems are observed to compete between molecular elimination reaction and bond dissociation reaction. It is observed that degradation of formaldehyde and formyl chloride ruled by 3-centered concerted mechanism produced H2 and HCl fragments respectively. On the other hand, Cl2 elimination reaction is generated via formation of isohalon structure. Despite of presence of isohalon intermediate, molecular elimination in phosgene required higher energy as compared to formyl chloride. Ease of molecular elimination in case of formyl chloride is attributed to favourable electrostatic interaction between hydrogen and chlorine atom, which assist in lower activation barrier. Further, the kinetic analysis suggested the applied temperature and pressure play a key role in formation of dominant elimination channel during decomposition reaction.

The enhanced strength and radiation efficiency of alumina reticulated porous ceramics via coal gangue addition

Al2O3 reticulated porous ceramics (ARPC) are widely selected for high-temperature porous media burners due to their excellent thermal stability. However, the relatively low mechanical property and infrared emissivity of ARPC led to a low lifespan and radiation efficiency of the burner, limiting its application in high-temperature porous burners. In this work, a novel strategy was proposed to synergistically improve mechanical and radiation properties of ARPC and recycle of coal gangue. ARPC with three-layered struts, including microporous alumina-mullite coating, alumina skeleton and filling layer, were prepared by polymer replica technique and vacuum infiltration method. The addition of coal gangue could obviously strengthen ARPC, because coal gangue was attributed to form mullite, as well as the generation of residual compressive stress in the coating of three-layered struts. The decomposition of organic compounds within coal gangue enhanced the degree of microporosity on the coating, thereby increasing infrared emissivity by 21.8%, which increased the surface temperature of porous burner from 857.4°C to 905.7°C.

Platinum-modified bismuth molybdate flake balls as visible-light-responsive photocatalyst

Solar photocatalysis is considered as one of the best methods for “green” purification of environment. Accordingly, efficient, stable, and low-price materials must be developed for possible commercial application. Herein, flower-like bismuth molybdate (Bi2MoO6) photocatalysts were successfully synthesized by CTAB-assisted hydrothermal process, and then surface modified with platinum by photodeposition. The obtained materials were characterized by various methods, including XRD, DRS, XPS, SEM, TEM, ESR, photoluminescence spectroscopy and photoelectrochemical tests. Photocatalytic activity was tested mainly for tetracycline (TC) antibiotic degradation under visible-light irradiation (λ > 420 nm), including scavenger tests and experiments for different operation conditions (TC concentration, photocatalyst dose, pH value, in the presence of inorganic salts, water taken from different reservoirs). It has been found that the best photocatalyst containing 0.5 wt% of platinum exhibits 94.2 % TC removal during 60-min visible-light irradiation, reaching the reaction rate constant of 0.0392 min−1 (exceeding the data reported up to now). It is proposed that exceptional photocatalytic performance is caused by the synergy between the uniform flower structure (efficient light harvesting and large specific surface area) and double function of platinum deposits, i.e., as a sink for electrons (hindering charge carriers’ recombination) and a plasmonic sensitizer (allowing energy transfer from excited platinum to oxygen). Superoxide radicals (•O2−) are the main oxidation species, as proven by the quenching experiments and EPR analysis. However, in the case of platinum-modified samples, singlet oxygen plays also an important role, and thus an energy transfer from plasmonic platinum to oxygen could be expected. Additionally, TC degradation pathways, elucidated by the detection of intermediates, and the toxicity data (TC and its degradation products), assessed by a quantitative structure–activity relationship (QSAR) method, have confirmed that photocatalytic degradation of TC is indeed an environmental-friendly method, highly recommended for the decomposition of persistent organic compounds.

Halotolerant Benzoic Acid-Degrading Bacteria of the Genus <i>Dietzia</i>

Six benzoic acid-degrading bacteria of the genus Dietzia were isolated from the saline ecotopes of the Verkhnekamskoe and Yakshinskoe salt deposits (Perm region, Komi Republic, Russia). Benzoic acid (BA) may accumulate in ecosystems through technogenic processes, as well as during the microbiological decomposition of complex organic compounds containing an aromatic ring. The strains studied here were found to be closely related to D. psychralcaliphila, D. kunjamensis subsp. kunjamensis, D. cercidiphylli, and D. maris. It was shown that they are halotolerant and able to thrive on BA as their sole carbon and energy source in the absence of salt or in the presence of 50–70 g/L NaCl. They also contain benA genes encoding the α-subunit of benzoate 1,2-dioxygenase, the key enzyme of BA degradation. The highest level of similarity (79.32–91.38%) was observed between the nucleotide sequences of the benA genes of the strains considered and the homologous sequences of Actinomycetes representatives from genera such as Dietzia, Mycolicibacterium, Geodermatophilus, Pseudonocardia, Corynebacterium, and Raineyella. The described active BA degraders belonging to the genus Dietzia have the potential to aid in the development of bioremediation techniques for environmental objects contaminated with mono(poly)aromatic pollutants and subject to salting.

A mixed blessing of influent leachate microbes in downstream biotreatment systems of a full-scale landfill leachate treatment plant

In landfill leachate treatment plants (LLTPs), the microbiome plays a pivotal role in the decomposition of organic compounds, reduction in nutrient levels, and elimination of toxins. However, the effects of microbes in landfill leachate influents on downstream treatment systems remain poorly understood. To address this knowledge gap, we collected 23 metagenomic and 12 metatranscriptomic samples from landfill leachate and activated sludge from various treatment units in a full-scale LLTP. We successfully recovered 1,152 non-redundant metagenome-assembled genomes (MAGs), encompassing a wide taxonomic range, including 48 phyla, 95 classes, 166 orders, 247 families, 238 genera, and 1,152 species. More diverse microbes were observed in the influent leachate than in the downstream biotreatment systems, among which, an unprecedented ∼30 % of microbes with transcriptional expression migrated from the influent to the biological treatment units. Network analysis revealed that 399 shared MAGs across the four units exhibited high node centrality and degree, thus supporting enhanced interactions and increased stability of microbial communities. Functional reconstruction and genome characterization of MAGs indicated that these shared MAGs possessed greater capabilities for carbon, nitrogen, sulfur, and arsenic metabolism compared to non-shared MAGs. We further identified a novel species of Zixibacteria in the leachate influent with discrete lineages from those in other environments that accounted for up to 17 % of the abundance of the shared microbial community and exhibited notable metabolic versatility. Meanwhile, we presented groundbreaking evidence of the involvement of Zixibacteria-encoded genes in the production of harmful gas emissions, such as N2O and H2S, at the transcriptional level, thus suggesting that influent microbes may pose safety risks to downstream treatment systems. In summary, this study revealed the complex impact of the influent microbiome on LLTP and emphasizes the need to consider these microbial characteristics when designing treatment technologies and strategies for landfill leachate management.

Understanding the light induced hydrophilicity of metal-oxide thin films

Photocatalytic effects resulting in water splitting, reduction of carbon dioxide to fuels using solar energy, decomposition of organic compounds, and light-induced hydrophilicity observed on surfaces of various metal oxides (MOx), all rely on the same basic physical mechanisms, and have attracted considerable interest over the past decades. TiO2 and ZnO, two natively n-type doped wide bandgap semiconductors exhibit the effects mentioned above. In this study we propose a model for the photo-induced hydrophilicity in MOx films, and we test the model for TiO2/Si and ZnO/Si heterojunctions. Experimentally, we employ a wet exposure technique whereby the MOx surface is exposed to UV light while a water droplet is sitting on the surface, which allows for a continuous recording of contact angles during illumination. The proposed model and the experimental techniques allow a determination of minority carrier diffusion lengths by contact angle measurements and suggest design rules for materials exhibiting photocatalytic hydrophilicity. We expect that this methodology can be extended to improve our physical understanding of other photocatalytic surface effects.

Detailed mechanism study of volatile organic compound decomposition and oxidation removal based on a ReaxFF MD method.

Volatile organic compounds (VOCs) are typical air pollutants as well as gaseous wastes that contain energy. Utilization and disposition of VOCs is currently an important research hotspot in the field of atmospheric environment. In this paper, the thermal cracking and oxidation reaction processes of typical VOCs components were modelled and analyzed by combining molecular dynamics and detailed reaction mechanisms, focusing on the effects of temperature, oxygen and other conditions on the conversion of VOCs. The results of molecular dynamics studies show that improving temperature and reaction time benefit the decomposition of VOCs. High temperatures under an inert atmosphere can sufficiently crack the VOCs themselves, but other by-products are generated, which in turn cause secondary pollution. The activation energies derived by ReaxFF-MD calculation are 328 kJ mol-1, 147 kJ mol-1 and 121 kJ mol-1 for toluene, styrene and benzaldehyde respectively, which is consistent with experimental results. Under the oxygen atmosphere, the conversion rate of VOCs is greatly increased and the reaction temperature is significantly reduced. Meanwhile, the oxidation reaction fully converts VOCs into non-polluting products such as CO2 and H2O. Detailed kinetic studies show that initial oxidation of toluene molecules raised by hydrogen abstraction reaction is the dominant step during toluene oxidation, which significantly improved the decomposition efficiency of toluene.