Mineralization Of Organic Compounds Research Articles

Nanoconfined catalytic membranes assembled by cobalt-loaded carbon nanotubes and graphene oxide for highly efficient water decontamination

This study presents a catalytic membrane based on cobalt-loaded carbon nanotubes and graphene oxide (Co@CNT-GO). Cobalt, serving as the active center, efficiently activates peroxymonosulfate for the degradation of organic compounds in transmembrane water. The uniform dispersion and firm loading of Co on CNT prevent the aggregation and leakage issues typically associated with conventional catalysts. The two-dimensional channels formed by the vacuum-assisted self-assembly of CNT and GO enhance the probability of contact between organic compounds and Co and prolong the contact duration thereby ensuring catalytic efficiency while maintaining a low water permeability resistance. The water flux of the catalytic membrane is 90 L/m2/h, and the atrazine removal efficiency is more than 92%, maintaining high stability even after continuous operation for 72 h. The generated active free radicals, including sulfate radicals, hydroxyl radicals, and singlet oxygen, synergistically facilitate the mineralization of organic compounds. Furthermore, the presence of oxygen vacancies on CNT accelerates the redox cycle of ≡ Co(II)/≡Co(III), sustaining the catalytically active center. Compared to the precursor catalytic membrane, Co@CNT-GO catalytic membrane possesses the characteristics of high removal efficiency and high flux, holding promise as a platform technology for the rapid and precise treatment of organic pollutants in contaminated water.

Advancing the eradication of harmful dyes through stereolithography-produced 3D floating photocatalysis: Exploiting the synergistic potential of graphene/MnO2/Fe3O4 hybrid nanomaterials

The utilization of heterogeneous photocatalysis for the breakdown of organic pollutants in wastewater has become increasingly popular as an alternative treatment method, offering rapid mineralization of organic compounds. However, the challenges lie in the recycling and recovery processes. To overcome this hurdle, a novel 3D-printed hybrid photocatalyst composed of graphene/MnO2/Fe3O4 was developed through an ex-situ approach. Comprehensive property evaluations were conducted, and the catalyst was employed in the creation of a 3D photocatalyst designed for MB dye removal under direct sunlight, facilitating the easy separation of the used catalyst. Further enhancement of its photocatalytic activity was achieved through carbonization, rendering it promising for wastewater treatment owing to its ordered structure and facile recovery. Notably, the developed 3D photocatalyst exhibited a significant improvement in MB dye degradation compared to powder samples. It showcased effective degradation of 10 ppm of MB dye within a mere 120 min of sunlight exposure. Radical trapping analysis indicated that the high photocatalytic degradation was predominantly attributed to the photogenerated superoxide radicals. Consequently, the 3D printed photocatalyst demonstrated exceptional reusability and sustained efficiency in MB dye degradation without any discernible decrease in catalytic activity. The augmented photocatalytic degradation was governed by the generation of photogenerated charge carriers through reduction and oxidation reactions. This research holds promise for the creation of an economical, user-friendly, and highly efficient 3D printed hybrid photocatalyst with synergistic applications in water purification.

Responses of soil bacterial and fungal community structure and functions to different plant species in a mixed forest plantation in a semi-arid region of China

Soil microbial communities play important roles in biogeochemical cycles and ecosystem functioning. However, how tree and grass species affect soil microbial structure and functions in semi-arid regions is poorly understood. In this study, we used sequencing of representative genes and bioinformatic analysis to compare the soil bacterial and fungal communities and their functional groups among legume and non-legume broad-leaved plantations, conifer plantations, artificial grassland, and adjacent farmland in a semi-arid area of Northern China. We found that soil bacterial diversity and abundance were significantly increased by legume plantations, especially Robinia pseudoacacia, compared to farmland. Soil bacterial communities were dominated by K-strategists in plantation soils and by r-strategists in farmland and grassland soils. Soil fungal communities showed contrasting patterns between Ascomycetes and Basidiomycota across treatments, and the highest abundance of nutrient indicator taxa Mortierellomycota was observed in plantation soils. Functional analysis revealed that afforestation altered the capacity of soil bacteria for organic compound mineralization and C and N cycling, and that different plant species enriched different types of ectomycorrhizal and saprophytic fungi. Moreover, we found that plantations and grasslands formed more connected but less complex and stable bacterial co-occurrence networks than farmland, and that conifer plantations increased the closeness of soil fungal networks compared to broad-leaved plantations. Our results suggest that tree and grass species play a key role in shaping the soil microbial community structure and functional groups, and provide valuable information for choosing suitable tree and grass species for ecosystem restoration and management in semi-arid regions.

Soil Fertilization with Palm Oil Mill Effluent Has a Short-Term Effect on the Bacterial Diversity of an Amazonian Agricultural Land Area.

Palm oil derived from the fruits of Elaeis guineensis Jacq. has global economic importance and is largely produced in tropical regions. The palm oil production process leads to a highly polluting waste called palm oil mill effluent (POME). A strategy commonly used by producers to overcome environmental issues and to improve soil fertility is the reuse of POME as a fertilizer due to the chemical and biological characteristics of the effluent. In this research, three groups were analyzed: soil without POME application (control group) and soil samples after 4 and 9 days of POME application. An environmental DNA metabarcoding approach was used. eDNA was extracted, and the V4 region of the 16S rRNA gene was amplified and sequenced in the Illumina MiSeq platform. The abundance of Proteobacteria (48.1%) and Firmicutes (9.0%) was higher in fertilized soil, while Bacteroidetes (20.3%) and Verrucomicrobia (7.8%) were more abundant in control soil. Additionally, the effluent seemed to modify soil characteristics favoring taxa responsible for the mineralization of organic compounds and nitrogen fixation such as species of Gammaproteobacteria class. Our study highlights the influence of POME on soil biological components and contributes to the sustainable production of palm oil in the Amazon.

BOD/COD ratio as a probing index in the O/H/O process for coking wastewater treatment

Biodegradation of coking wastewater (CWW) containing high concentrations of toxic pollutants with nutritional imbalance is challenging. Biodegradability estimated as the ratio of 5-day biochemical oxygen demand (BOD5) to chemical oxygen demand (COD) was studied along with the influential operational factors in a full-scale oxic/hydrolytic & denitrification/oxic (O/H/O) plant for CWW treatment. The influential factors for the B/C ratio in each unit of the O/H/O provided by the experimental and theoretical BOD5 were elucidated. Batch experiment with various sludge inoculation settings showed that the B/C ratio of raw CWW increased from 0.38 ± 0.04 to 0.47 ± 0.05 after flocculation pretreatment due to the removal of sulfide and cyanide. In the O1 reactor, quickly depleted biodegradable pollutants resulted in a drastic decrease of the B/C ratio to 0.1 ± 0.02 together with a reduction in the CWW toxicity. In the H reactor, the B/C ratio increased to 0.28 ± 0.04 because of the hydrolysis of residual macromolecular organic matter and nitrite accumulation from the denitrification process. The B/C ratio in the O2 reactor dropped below 0.06 along with the complete nitrification. The relative abundance of organic pollutants, the structure and function of bacterial community were analyzed in each reactor to explain the changes in the B/C ratio. On the whole, the monitoring of the B/C ratio along different stages of the CWW treatment is an approach suitable to follow the efficacy of functional bacterial groups and their responses to the water characteristics. The B/C ratio thus becomes a marker of the extent of nitrogen transformations, CWW detoxification and mineralization of organic compounds. More broadly, the B/C ratio helps optimize the operation parameters of biological processes and indicate the functionality of each unit.

Mineralization of fipronil using solar light-induced ZnO/Co3O4 photocatalyst@ceramic substrate: Optimization of parameters by RSM

Mineralization of organic compounds especially fipronil (FP) pesticide is a major concern, while its metabolites exhibit significant toxicity, which poses a significant threat to human health and the environment. Here, ZnO, Co3O4, nanoparticles and ZnO/Co3O4 nanocomposite thin films have been fabricated on ceramic plate by spray pyrolysis method. The central composite design (CCD) method under response surface methodology (RSM) is used to optimize operational parameters and 94.95% mineralization was achieved at optimum conditions. The photocatalytic mineralization of FP pesticide has been evaluated by FTIR and UV/Vis spectroscopic techniques, and the disappearance of the main characteristics peaks indicate the mineralization of the FP pesticide. Moreover, the fabrication of catalyst over CP imparted promising reusability and stability that maintained ∼ 100% performance for the first 3 cycles of FP pesticide treatment. However, after the 3rd cycle, it began to decline and dropped to 64.03% when the 26th cycle was administered.

Photocatalytic discoloration of methylene blue by TiO2 P25 under UV light using ISO 10678 standard as a guide

• TiO 2 is the most used semiconductor for photomineralization of organic compounds. • Discoloration of a dye is the most used technique for photocatalytic performance. • ISO 10678:2010 standard was used e for testing the performance of powdered P25 TiO 2 . • Time of exposure, dye concentration and intensity of the UV light were analyzed. • UV intensity was the only factor statistically significant for photocatalysis. In heterogeneous photocatalysis, TiO 2 is the most used semiconductor for mineralization of organic compounds. The most used technique to determine the photocatalytic performance of semiconductors is the discoloration of an organic dye. However, there is no consensus on the procedure for dye discoloration. In this work, the ISO 10678:2010 standard, applied for catalytic surfaces, was used as a guide for testing the performance of the TiO 2 (P25) for the discoloration of methylene blue under UV light. The time of exposure, dye concentration and intensity of the UV light were the parameters of the study. As a result, the UV intensity was the only factor affecting the photocatalysis.

A Critical Review of Photo-Based Advanced Oxidation Processes to Pharmaceutical Degradation

Currently, the production and consumption of pharmaceuticals is growing exponentially, making them emerging contaminants that cause hazards to the ecological environment and human health. These drugs have been detected in surface water and drinking water around the world. This indicates that the conventional treatments used are ineffective for the removal of these compounds from the water, since they are very complex, with high stability and have high persistence in aquatic environments. Considering this problem, several types of alternative treatments, such as advanced oxidative processes, have been studied. Of these, AOPs using irradiation have received increasing interest due to their fast reaction rate and the ability to generate oxidizing species, which leads to an efficient degradation and mineralization of organic compounds, thus improving the quality of water and allowing its reuse. Therefore, in this review, we focus on the advances made in the last five years of irradiated AOPs in the degradation of different classes of pharmaceutical compounds. The articles address different study parameters, such as the method of the synthesis of materials, oxidants used, treatment time, type of light used and toxicity of effluents. This review highlights the success of irradiated AOPs in the removal of pharmaceuticals and hopes to help the readers to better understand these processes and their limitations for removing drugs from the environment. It also sheds light on some paths that future research must follow so that the technology can be fully applied.

Assessing the Effects of Ozonation on the Concentrations of Personal Care Products and Acute Toxicity in Sludges of Wastewater Treatment Plants.

The aim of this study was to understand the distribution of the personal care products nonylphenol (NP), triclosan (TCS), benzophenone-3 (BP-3), and caffeine in the sludges from three wastewater treatment plants (WWTP-A, -B, and -C) in southern Taiwan. The four compounds were analyzed from activated sludge and dewatered sludge samples, and then the samples were treated with pressure-assisted ozonation under different conditions and removal efficiencies. All four target compounds were detected, especially NP, which was detected in the highest concentrations in the activated sludges of WWTP-A and dewatered sludges of WWTP-C at 17.19 ± 4.10 and 2.41 ± 1.93 µg/g, respectively. TCS was dominant in dewatered sludges from WWTP-B, and the highest detected concentration was 13.29 ± 6.36 µg/g. Removals of 70% and 90% were attained under 150 psi at 40 cycles for NP and TCS, respectively, with 5 min of ozonation reaction time, a solid/water ratio of 1:20, and 2% ozone concentration. Ecological risk quotients (RQs) were calculated by the ratios of the 10-day Hyalella azteca (freshwater amphipod) LC50 to the environmental concentrations of the target compounds. High RQs were found to be >10 for NP, TCS, and BP-3 in untreated sludges, resulting in significant ecological risks to aquatic organisms when the sludges are arbitrarily disposed. However, the toxic effects on Hyalella azteca were not significantly different among ozone sludge treatments. The reason for this may be related to the formation of toxic oxidation by-products and incomplete mineralization of organic compounds. This could also be true for unknown intermediates. The relatively high detection frequencies of these emerging compounds in WWTP sludges requires further applications and treatments.

Decomposition rate and biochemical fate of carbon from natural polymers and microplastics in boreal lakes.

Microbial mineralization of organic compounds is essential for carbon recycling in food webs. Microbes can decompose terrestrial recalcitrant and semi-recalcitrant polymers such as lignin and cellulose, which are precursors for humus formation. In addition to naturally occurring recalcitrant substrates, microplastics have been found in various aquatic environments. However, microbial utilization of lignin, hemicellulose, and microplastics as carbon sources in freshwaters and their biochemical fate and mineralization rate in freshwaters is poorly understood. To fill this knowledge gap, we investigated the biochemical fate and mineralization rates of several natural and synthetic polymer-derived carbon in clear and humic lake waters. We used stable isotope analysis to unravel the decomposition processes of different 13C-labeled substrates [polyethylene, polypropylene, polystyrene, lignin/hemicellulose, and leaves (Fagus sylvatica)]. We also used compound-specific isotope analysis and molecular biology to identify microbes associated with used substrates. Leaves and hemicellulose were rapidly decomposed compared to microplastics which were degraded slowly or below detection level. Furthermore, aromatic polystyrene was decomposed faster than aliphatic polyethylene and polypropylene. The major biochemical fate of decomposed substrate carbon was in microbial biomass. Bacteria were the main decomposers of all studied substrates, whereas fungal contribution was poor. Bacteria from the family Burkholderiaceae were identified as potential leaf and polystyrene decomposers, whereas polypropylene and polyethylene were not decomposed.

Enhanced visible light driven photoelectrochemical degradation of tetracycline hydrochloride using a BiOI photoanode modified with MnO2 films.

Removal of pharmaceuticals in wastewater has been the focus of many research due to the recalcitrant nature and hazardous effects of these compounds. The photoelectrochemical degradation process has proven to be suitable to harness solar energy for the mineralization of organic compounds in wastewater. Herein, we report the application of BiOI/MnO2 heterostructured anode for the photoelectrochemical degradation of tetracycline hydrochloride in aqueous solution. The photoanode was prepared through electrodeposition technique and fully characterized through microscopic, spectroscopic and electrochemical techniques. The results showed that formation of p-n heterojunction between BiOI and MnO2 in the photoanode led to improved charge separation which was evident in improved optical and photoelectrochemical properties. The FTO-BiOI/MnO2 electrode attained a photocurrent density of 0.104mAcm-2 with applied potential of 1.0V (vs Ag/AgCl) which was almost double that of pristine BiOI suggesting efficient charge separation. The heterostructured photoanode achieved 94% removal of tetracycline hydrochloride after 120min through the PEC degradation process with 61% mineralization efficiency. The electrode showed good reusability and stability with 92% PEC removal after eight cycles. Hence, the FTO-BiOI/MnO2 has a great potential as anode for PEC wastewater treatments.

Micropollutants Removal from Water and Activated Carbon Regeneration by Combining Adsorption and Electro-Fenton

The presence of micropollutants in municipal wastewater effluents is a topic of major concern, as these pollutants end up in surface and ground waters. Currently, adsorption on activated carbon (AC) is used to remove these recalcitrant compounds. When saturated, the AC is generally either thermally regenerated or disposed of. Thermal regeneration is expensive and negatively affects the structure and adsorptive properties of the AC.Over the last decade, considerable attention has been directed towards the electrochemical advanced oxidation processes (eAOPs), due to their ability to remove a large range of organic pollutants from water even at very low concentrations [1]. eAOPs rely on the in-situ generation of powerful oxidants, such as HO• by electron transfer at the anode surface. However, these processes are limited by mass transfer and require high energy consumption.In this study, combined adsorption on granular activated carbon (GAC) and electro Fenton process (EF) is applied. The purpose of this coupled process is to overcome the mass transfer issue by pre-concentrating the compounds on AC and proposing a new AC regeneration method. During the EF the AC can directly be used as a cathode. Due to the electrostatic repulsions and oxidation process, the compounds are desorbed from the AC and oxidized by the HO• generated in the bulk. Material and Methods The adsorption cycles and EF experiments were performed in batch mode using deionized water (DW) and simulated wastewater (SWW) with caffeine as a model compound. Similar experimental steps and conditions as described in [2] are followed, using 1g of GAC, with pH=3, Fe2+= 0.15 mM, Na2SO4= 50mM, and a current intensity of 200 mA. To assess the degradation and mineralization of the caffeine, HPLC and TOC measurements were used, respectively. The regeneration efficiency was calculated by comparing the adsorption capacity of the AC after each regeneration cycle with its initial adsorption capacity. Results and Conclusions The efficiency of the process was discussed as regards (i) desorption of organic compounds and regeneration efficiency in DW and SWW, (ii) degradation and mineralization of organic compounds, and (iii) stability of GAC for several successive regeneration cycles. During the regeneration, over 80% of desorbed caffeine was degraded and 75% was mineralized due to the formed HO• by Fenton reaction and at the BDD anode surface (Fig.1). Furthermore, a recovery of the AC adsorption capacity by up to 50 % in PW and 37% in SWW was observed. These regeneration percentages decreased to 25% during the second cycle and then remained stable during the third and the fourth cycle. The incomplete regeneration is most likely due to remaining caffeine molecules at the AC [3], or a blockage of the carbon adsorption sites by formed degradation molecules. Hence, a longer treatment time might lead to higher efficiency. These hypotheses will be taken into consideration in future work to draw a clear conclusion on the regeneration phenomenon. The similar regeneration efficiencies and mineralization rates obtained during the 2nd,3rd, and 4th cycles indicate the stability of the GAC electrode.In conclusion, the results from this study illustrate that combined adsorption and EF is a suitable process for the removal of caffeine and regeneration of AC. The advantage of such a process is that part of the AC can be regenerated while over 75% of the desorbed compounds from the AC are mineralized, thus avoiding toxic effluents. This process is currently implemented as a continuous e-cell for sequential adsorption and EF regeneration.

A review on recent progressions of Bismuth ferrite modified morphologies as an effective photocatalyst to curb water and air pollution

• The most recent advancement on BFO based Nanoparticles are summarized. • Present-day implementations of Bismuth Ferrite Nanoparticles in environmental remediations are discussed. • Structural properties and effect of doping is described in detail. • Future opportunities and research gaps are outlined. Fuel crisis and atmospheric pollution have been major environmental issues from the advent of the nuclear era of 1945. Photocatalysis for water splitting and organic contaminant degradation in presence of sunlight is a promising and recently in-trend for solving current environmental problems. Photocatalytic oxidation offers distinct advantages such as its extensive applicability of total mineralization of organic compounds without any secondary pollution. Bismuth Ferrite (BiFeO 3 ) and its doped materials have gained a lot of attention nowadays due to its very narrow band gap (≈2.1 eV), recycling nature, coexistence of magnetic and ferroelectric properties and distinctive crystal structure. Due to these elaborated properties, Bismuth Ferrite emerges as an interesting material as a photocatalyst. The focus of this article is to summarize BFO photocatalytic properties and how can it be used to remediate air pollutants and water pollutants multiple times. This review also broadly discusses about BiFeO 3 as a visible light photocatalyst and its present shape of work, research gaps and future scope.

A critical view of the contributions of photoelectrochemical technology to pharmaceutical degradation

The deterioration of water quality and its reuse has generated the necessity to develop water treatment processes with different qualities for industry, agriculture, and human consumption. The types of water contaminants have grown and diversified with different types of processes and activities such as urbanization, industrialization, agriculture, and livestock. In this sense, recalcitrant contaminants stand out, which are not easily removed by conventional water treatment methods. These recalcitrant compounds include pharmaceuticals, whose use has increased significantly, causing long-term danger to humans, animals, and the environment through cumulative exposure. Considering this aspect, it is not surprising that photoelectrochemical processes have become more popular in recent years due to the capacity to generate alternatively oxidizing species which lead to mineralization of organic compounds, improving the quality of water for reusing, even if such species are present in minimal concentrations. In this review, we highlight the main semiconductor materials used in photoelectrocatalysis for the degradation of pharmaceutical compounds, as well as their efficiency in degrading some drugs including antibiotics, analgesics, anti-inflammatories, antivirals, and antidepressants. The main semiconductors used are TiO2, WO3, ZnO, CuO, Cu2O, and BiVO4 photoelectrocatalysts pure or doped and in the presence of cocatalysts or heterostructures. Photocatalytic fuel cells (PFCs) were also investigated in relation to degradation and electricity generation. The system provides a double benefit to the environment: waste materials can be consumed, and solar radiation can be converted into useful energy sources, such as electricity, hydrogen, or fuel. Therefore, photoelectrochemical approaches are currently being considered as a viable method of degrading drugs in water.

Electrolysis catalyzed ozonation for advanced wastewater treatment

The prohibitive cost of advanced oxidation processes (AOPs) necessitates the development of innovative variations to increase their applicability. This investigation evaluated the combination of ozonation and electrolysis using iron electrodes as a catalytic ozonation AOP for the mineralization of organic compounds in water. The operating parameters of initial pH and current density were optimized using response surface methodology (RSM) to maximize total organic carbon (TOC) removal from a dextrose based synthetic wastewater. The process was most effective for TOC removal in alkaline conditions (initial pH of 9), although performance compared to ozonation alone was more significantly enhanced in acidic conditions (initial pH of 3). TOC removal was found to increase as current density increased from 4 to 12 mA/cm2, regardless of initial pH, primarily due to the increased rate of catalyst addition from the sacrificial anode. It was determined that the initial pH of the system presented a more statistically significant effect on TOC removal than current density, although both parameters were determined to be relevant. Under optimal conditions of 12 mA/cm2 and an initial pH of 9, 63% TOC removal was achieved after 60 min of treatment. Catalyst dosage using electrochemical and chemical approaches was compared, finding that electrochemical catalyst dosage was preferred for TOC removal, illustrated by the pseudo-first order rate constant of observed TOC removal, which was 51–76% higher using the electrochemical approach. Using an indirect measurement method involving tert-Butyl alcohol, hydroxyl radicals were detected during the combined ozonation and electrolysis treatment. Radical production was found to be linked to the conditions which favoured TOC removal. The results of this study have demonstrated the ability of an electrochemical catalytic ozonation process to enhance the removal of organic contaminants in wastewater compared to ozonation alone, established the advantages of harnessing an electrochemically generated catalyst, and characterized the effect of key operating parameters on TOC removal performance and hydroxyl radical production.

Using niobium/BDD anode-based multi-cell flow reactor for the electrochemical oxidation of methyl paraben in the presence of surfactants

This study reports the electrochemical oxidation of methyl paraben (MeP) in synthetic wastes in the presence of surfactants using boron-doped diamond (BDD) anode and the interfering effect of the surfactants in MeP removal. The selected surfactants (cationic, anionic, and neutral) were used at critical micellar concentrations (CMC) and below with measurements performed to evaluate the removal rates of MeP and total organic carbon (TOC). The effects of current density (15, 30, and 45 mA cm−2), surfactant concentration, and initial pH on the efficiency of the electrochemical oxidation process were analyzed. At low concentrations, the interfering effect of the anionic surfactant (sodium dodecyl sulfate - SDS) was greater than that of the cationic surfactant (hexadecyltrimethylammonium bromide - CTAB). The complete mineralization of MeP + SDS was achieved at 45 mA cm−2 in 2 h; this was attributed to the generation of persulfate radicals at current densities higher than 15 mA cm−2. Genapol C-100 (Genapol) exerted less interference during the mineralization of MeP + Genapol compared to the systems containing other surfactants at CMC. MeP removal was favored by the use of a basic medium. The increase in surfactant concentration decreased the efficiency of MeP and TOC removal due to the formation of micelles and the intensity of MeP-surfactant interactions, apart from the increase in organic load in the system. CTAB interacted more with the ionic form of MeP in the basic medium compared to the other surfactants. All these factors influenced the mineralization of organic compounds in the systems.

Methanogenic archaea use a bacteria-like methyltransferase system to demethoxylate aromatic compounds

Methane-generating archaea drive the final step in anaerobic organic compound mineralization and dictate the carbon flow of Earth’s diverse anoxic ecosystems in the absence of inorganic electron acceptors. Although such Archaea were presumed to be restricted to life on simple compounds like hydrogen (H2), acetate or methanol, an archaeon, Methermicoccus shengliensis, was recently found to convert methoxylated aromatic compounds to methane. Methoxylated aromatic compounds are important components of lignin and coal, and are present in most subsurface sediments. Despite the novelty of such a methoxydotrophic archaeon its metabolism has not yet been explored. In this study, transcriptomics and proteomics reveal that under methoxydotrophic growth M. shengliensis expresses an O-demethylation/methyltransferase system related to the one used by acetogenic bacteria. Enzymatic assays provide evidence for a two step-mechanisms in which the methyl-group from the methoxy compound is (1) transferred on cobalamin and (2) further transferred on the C1-carrier tetrahydromethanopterin, a mechanism distinct from conventional methanogenic methyl-transfer systems which use coenzyme M as final acceptor. We further hypothesize that this likely leads to an atypical use of the methanogenesis pathway that derives cellular energy from methyl transfer (Mtr) rather than electron transfer (F420H2 re-oxidation) as found for methylotrophic methanogenesis.

Photocatalytic efficiency of CuNiFe2O4 nanoparticles loaded on multi-walled carbon nanotubes as a novel photocatalyst for ampicillin degradation

Nickel-copper ferrite nanoparticles (CuNiFe2O4) were loaded onto multi-walled carbon nanotubes (MWCNTs) and used as a novel photocatalyst in the photodegradation of ampicillin (AMP) from aqueous solutions. Photocatalyst properties were characterized by scanning electron microscopy, transition electron microscopy, Fourier-transform infrared spectroscopy, Brunauer–Emmett–Teller analysis, and X-ray diffraction. The results showed that the MWCNTs-CuNiFe2O4 in the UV–photocatalytic process has high degradation efficiency for AMP molecules (100%), compared to adsorption (59.68%), and photolysis (38.41%) processes. At conditions: pH = 5, MWCNTs-CuNiFe2O4 dose = 0.5 g/L, reaction time = 60 min, and UV light intensity = 36 W, the suggested treatment provided a complete degradation rate of AMP, as well as 92.42% TOC removal and 93.32% COD removal. Formation of byproducts including ammonia (NH3), nitrate (NO3–) and sulfate (SO42-) during AMP photocatalytic degradation confirmed mineralization of organic compounds including nitrogen and sulfur compounds, in addition to CO2 and H2O. Scavenging experiments showed that superoxide (•O2–), hydroxyl radicals (•OH) and holes (h+) were produced in the photocatalysis process, however •OH and h+ were the main reactive species. The stability test demonstrated that the photocatalyst could be recycled 8 times with minimal performance reduction for AMP degradation. The energy consumption of the present process for different AMP concentrations was in the range of 5–33.33 kWh/m3, which indicates that the suggested treatment is energy-efficient. Toxicity assessment with E. coli and P. phosphoreum inhibition rates showed that MWCNts-CuNiFe2O4 under UV light has a significant effect on reducing the toxicity ratio of photolysis alone. According to the findings, the application of MWCNTs-CuNiFe2O4 in the UV–photocatalytic process of AMP degradation is an eco-friendly and has high application potential in AMP removal and mineralization.

Feasibility Study of Tetracycline Removal by Ozonation Equipped with an Ultrafine-Bubble Compressor

In this study, a combination of an ozone gas producer and an ultrafine-bubble compressor was used to degrade tetracycline, which is a well-known antibiotic and medicine commonly used in human and animal care, and effects of varying the reaction parameters were studied. Experiments indicate that each gram of introducing ozone can degrade 2.72 g of tetracycline at pH 3 and 1.48 g at pH 11. However, basic conditions contribute to increased mineralization of tetracycline because of the ·OH radical oxidation mechanism. Higher reaction temperatures and higher ozone dosages enhance the reactivity between the ozone molecules, ·OH radicals, and tetracycline, resulting in a decline in the toxicity of the tetracycline solution as measured by cell viability. The mineralization of organic compounds is the key to decreasing the toxicity of the solution. Ultrafine-bubble ozonation can provide homogeneity of gas bubbles in solution hence it not only reduces the requirement of ozone and thus the operational cost of the reaction, but also extends the efficacy of the method to the treatment of solutions with high tetracycline concentrations.

Assessment of diversity and composition of bacterial community in sludge treatment reed bed systems

Due to their low emission of odours and lack of the need to apply additional chemical agents, sludge treatment reed beds (STRBs) constitute an economically feasible and eco-friendly approach to sewage sludge management. Correctly designed and operated STRBs ensure effective reduction of the dry matter content coupled with the mineralisation of organic compounds. Successful operation of STRBs relies on complex interactions between the plants and microorganisms responsible for the decomposition of organic matter and nutrient cycling. While the biocenoses of wetland systems dedicated to wastewater treatment have been intensively investigated, in the case of sludge treatment applications, there is a deficit of available microbial data. The aim of this study was to explore the diversity and spatial distribution of the bacteria in three distinct STRBs which differ in maturation and feeding patterns. Analyses of the dry mass and organic matter content showed the general trend of the sludge stabilisation processes advancing through the bed depth, with the best performance in the Matured Continuous Feed (MCF) bed being noted. Samples from the MCF bed showed the statistically greatest biodiversity in relation to the other beds. Moreover, increased biodiversity of microorganisms was observed on the surface of the STRBs and the bottom zone of the MCF equipped with a passive aeration system, which proves the application of such solutions in order to enhance the performance of the process. The results of 16S rRNA gene sequencing revealed that Bacteroidetes, Proteobacteria and Firmicutes contributed approximately 80% of all identified sequences read. Network analysis revealed dominant role of Bacteroidetes in the formation of interspecies co-existence patterns. Nitrospira was the most abundant organism responsible for nitrogen metabolism in the STRBs.