Effect of Fe3+ on the sludge properties and microbial community structure in a lab-scale A2O process

Synchronous vanadium bio-reduction/detoxification/recovery and nitrogen attenuation in a membrane aerated biofilm reactor

The presence of both pentavalent vanadium [V(Ⅴ)] and nitrogen in wastewaters from vanadium smelting poses significant environmental challenges. However, it remains little in the way of continuous flow biological reactor to concurrently eliminated V(Ⅴ) and nitrogen in wastewaters. Herein, membrane-aerated biofilm reactor (MABR) system was designed to achieve simultaneous nitrification and denitrification (SND) alongside biological reduction, detoxification, and recovery of vanadium. Vanadium and nitrogen removal performances, solid-state characterization, microbial compositions and functional genes, and the mechanism related to the metabolism of vanadium and nitrogen were illuminated. Notably, we identified a potential role for biofilm-derived "secretion" in the transformation of V(Ⅴ) and nitrogen. Our findings revealed that the system achieved SND efficiency of 98.00 ± 0.57 % and removed 91.10 ± 3.60 % of total vanadium (TV) even at high influent V(Ⅴ) concentrations in continuous flow stage. Batch experiments implied that the conversion of NH4+-N was the limiting process of nitrogen removal in MABR system, and the extracellular polymeric substances (EPS) might play an important role in the conversion of V(Ⅴ) and nitrogen. V(Ⅴ) was reduced to V(Ⅳ), which was immobilized to biofilm and "secretion" by microbial surface functional groups, including C-O, O-C=O and -OH. Acinetobacter, Dechlorobacter, Denitratisoma and Nitrospira were verified as microbes associated with V(Ⅴ) and nitrogen metabolism. The abundance of functional genes pertaining to electron donor, electron transport, and electron acceptor systems increased under high V(V) stimulation. Collectively, the cooperation of biofilm and "secretion" ensured the intensive removal of vanadium and nitrogen. This study provides new insights into the concurrent removal of heavy metal and environmental nutrient.

Microbial interactions elucidate the mechanisms of hydraulic retention time altering denitrification pathway in a sole pyrite-based electrochemical bioreactor (PEBR)

In the current context of low-carbon wastewater treatment, pyrite-based autotrophic denitrification (PAD) has gained attention as an energy-efficient and environmentally sustainable method for nitrogen elimination. However, the limited dissolution of pyrite and the associated slow autotrophic denitrification rate restrict its practical application. To tackle this, a pyrite-based electrochemical bioreactor (PEBR) was constructed and the microbial effect of hydraulic retention time (HRT) on denitrification efficiency and sulfide or iron oxidation in the PEBR system was investigated. It was found that upon the conclusion of phase V (HRT = 12 h), the nitrate removal efficiency (NRE) reached 92.53% ± 0.96%, and the concentration of NH4+-N in the effluent reached 2.63 ± 0.57 mg/L with a minimal accumulation of NO2--N (0.03 ± 0.05 mg/L) when the optimal treatment performance was obtained. As the HRT increased, the proportion of heterotrophic denitrification decreased substantially to 1%. Desulfobacterota, a sulfate-reducing bacteria (SRB), became dominant, with a relative abundance ranging from 0.04% to 19.44%. The PAD-related genera, such as Thiobacillus and Ferritrophicum, exhibited a positive correlation with HRT, indicating that PAD was enhanced with the extension of HRT. The functional genes related to Fe2+ intracellular oxidation (e.g., korA/B) positively correlated with HRT. The positive correlation of dsrA/B with HRT highlighted the role of dissimilatory sulfate reduction (DSR) as a primary contributor to reduced sulfate production. Furthermore, the variations in the relative abundance of aprA/B for sulfate reduction with the extension of HRT reflected that HRT affected sulfate reduction probably via the APS→SO32- process. This study might shed light on the optimization of HRT in PEBR for the treatment of nitrogenous wastewater.

Fe(III)-Aided Novosphingobium sp. ES2-1 Regulates Molecular Mechanisms of 17β-Estradiol Biodegradation

17β-estradiol (E2) is one of the strongest environmental estrogens threatening wildlife and human health globally. Microbial degradation is an alternative strategy to remediate E2-contaminated sites and may be regulated by ubiquitous Fe(III) in eco-environments. We have previously obtained a high-efficiency E2 degrader, Novosphingobium sp. ES2-1, and investigated its metabolic pathway in connection with monooxygenase EstO1-induced ring-B opening; however, the molecular mechanisms of ring-A cleavage in E2 are sorely lacking, especially under Fe(III)-aided regulation. Here, an extradiol dioxygenase EstN1 from strain ES2-1 involved in the ring-A cleavage of E2 was reported. It catalyzed the 4,5-seco reaction of 4-hydroxyestrone (4-OH-E1, a key E2-oxidized intermediate) with the support of the electron transport chain consisting of ferredoxin EstN2 and ferredoxin reductase EstN3, resulting in a ring-A meta-cleaved product. Interestingly, Fe(III)-assisted strain ES2-1 consolidated the opening of rings A and B in E2 by reinforcing the expression of estO1 and estN1 genes, consequently enhancing E2 metabolism. Compared to Fe(III) starvation, the biodegradation half-life of E2 was sharply reduced from 1.35 to 0.59 d after Fe(III) supplementation. Simultaneously, the transcription of estO1 and estN1 genes increased clearly from 4.3 to 47.5 times and 6.6 to 246.8 times after Fe(III) induction, respectively, accompanied by remarkable improvement in the abundance of ring-A/B cleavage products and their pyridine derivatives. These findings highlight the significance of Fe(III) in regulating the microbial remediation of environmental estrogens at the molecular level.

Metagenomic analysis reveals the mechanisms of biochar supported nano zero-valent iron in two-phase anaerobic digestion of food waste: microbial community, CAZmey, functional genes and antibiotic resistance genes

The mechanisms of biochar supported nano zero-valent iron (BC/nZVI) on two-phase anaerobic digestion of food waste were investigated. Results indicated that the performance of both acidogenic phase and methanogenic phase was effectively facilitated. BC/nZVI with the amount of 120 mg/L increased methane production by 32.21%. In addition, BC/nZVI facilitated direct interspecies electron transfer (DIET) between Geobacter and methanogens. Further analysis showed that BC/nZVI increased the abundance of most CAZymes in acidogenic phase. The study also found that BC/nZVI had positive effects on metabolic pathways and related functional genes. The abundances of acdA and ackA in acidogenic phase were increased by 151.75% and 36.26%, respectively, and the abundances of pilA and TorZ associated with DIET were also increased. Furthermore, BC/nZVI mainly removed IMP-12, CAU-1, cmeB, ErmR, MexW, ErmG, Bla2, vgaD, MuxA, and cpxA from this system, and reduced the antibiotic resistance genes for antibiotic inactivation resistance mechanisms.

Development of a novel three-dimensional biofilm-electrode system (3D-BES) loaded with Fe-modified biochars for enhanced pollutants removal in landfill leachate

Different mass ratio iron (Fe)-loaded biochars (FeBCs) were prepared from food waste and used in the three-dimensional biofilm-electrode systems (3D-BES) as particular electrodes for landfill leachate treatment. Compared to the unmodified biochar (BC), specific surface area of Fe-loaded biochars (FeBC-3 with a Fe: biochar of 0.2:1) increased from 63.01 m2/g to 184.14 m2/g, and pore capacity increased from 0.038 cm3/g to 0.111 cm3/g. FeBCs provided more oxygen-containing functional groups and exhibited excellent redox properties. Installed with FeBC-3 as particular electrode, both NH4+-N and chemical oxygen demand COD removals in 3D-BESs were well fitted with the pseudo-first-order model, with the maximum removal efficiencies of 98.6 % and 95.5 %, respectively. The batch adsorption kinetics experiments confirmed that the maximum NH4+-N (7.5 mg/g) and COD (21.8 mg/g) adsorption capacities were associated closely with the FeBC-3 biochar. In contrast to the 3D-BES with the unmodified biochar, Fe-loaded biochars significantly increased the abundance of microorganisms being capable of removing organics and ammonia. Meanwhile, the increased content of dehydrogenase (DHA) and electron transport system activity (ETSA) evidenced that FeBCs could enhance microbial internal activities and regulate electron transfer process among functional microorganisms. Consequently, it is concluded that Fe-loaded biochar to 3D-BES is effective in enhancing pollutant removals in landfill leachate and provided a reliable and effective strategy for refractory wastewater treatment.

Biochar-Associated Free Radicals Reduce Soil Bacterial Diversity: New Insight into Ecoenzymatic Stoichiometry

The toxicity of environmentally persistent free radicals (EPFRs), often generated during biochar production, on soil bacteria is still not truly reflected when considering the conditions in real soil. Herein, the influence of free radicals within biochar on soil bacteria was investigated from the perspectives of enzyme activity, community structure, and ecoenzymatic stoichiometry. Biochar addition enhanced the contents of EPFRs and derived hydroxyl radicals (•OH) in the soil, while it reduced bacterial alpha diversity by 5.06-35.44%. The results of redundancy analysis and inhibition experiments collectively demonstrated the key role of EPFRs and •OH in reducing the bacterial alpha diversity. Specifically, EPFRs and •OH increased the stoichiometric imbalance by promoting the release of dissolved organic carbon and ammonium N, thus aggravating the P limitation in soil. This was further confirmed by increased alkaline phosphatase activity from 702 to 874 nmol g-1 h-1. The P limitation induced by EPFRs and •OH decreased the bacterial alpha diversity, as evidenced by the negative correlation between P limitation and bacterial alpha diversity (r2 = -0.931 to -0.979, P < 0.01) and the structural equation model. The obtained results demonstrate a ubiquitous but previously overlooked mechanism for bacterial toxicity of biochar-associated free radicals, providing scientific guidance for safe utilization of biochar.

Enhanced denitrification of the AO-MBBR system used for expressway service area sewage treatment: A new perspective on decentralized wastewater treatment

Decentralized wastewater treatment warrants considerable development in numerous countries and regions. Owing to the unique characteristics of high ammonia nitrogen concentrations and low carbon/nitrogen ratio, nitrogen removal is a key challenge in treating expressway service area sewage. In this study, an anoxic/oxic-moving bed biofilm reactor (A/O-MBBR) and a traditional A/O bioreactor were continuously operated for 115 days and their outcomes were compared to investigate the enhancement effect of carriers on the total nitrogen removal (TN) for expressway service area sewage. Results revealed that A/O-MBBR required lower dissolved oxygen, exhibited higher tolerance toward harsh conditions, and demonstrated better shock load resistance than traditional A/O bioreactor. The TN removal load of A/O-MBBR reached 181.5 g‧N/(m3‧d), which was 15.24% higher than that of the A/O bioreactor. Furthermore, under load shock resistance, the TN removal load of A/O-MBBR still reached 327.0 g‧N/(m3‧d), with a TN removal efficiency of above 80%. Moreover, kinetics demonstrated that the denitrification rate of the A/O-MBBR was 121.9% higher than that of the A/O bioreactor, with the anoxic tank biofilm contributing 60.9% of the total denitrification rate. Community analysis results revealed that the genera OLB8, uncultured_f_Saprospiraceae and OLB12 were the dominant in biofilm loaded on carriers, and OLB8 was the key for enhanced denitrification. FAPROTAX and PICRUSt2 analyses confirmed that more bacteria associated with nitrogen metabolism were enriched by the A/O-MBBR carriers through full denitrification metabolic pathway and dissimilatory nitrate reduction pathway. This study offers a perspective into the development of cost-effective and high-efficiency treatment solutions for expressway service area sewage.

Roles of catalytic ozonation by bimetallic Fe/Ce loading sludge-derived biochar in amelioration of sludge dewaterability: Performance and implementation mechanisms

In this study, an environmentally friendly alternative was developed using catalytic ozonation by sludge-derived biochar loaded with bimetallic Fe/Ce (O3/SBC-FeCe) for enhanced sludge dewatering. The results indicated that the lowest capillary suction time (CST) of 20.9 s and water content of dewatered sludge cake (Wc) of 64.09% were achieved under the dosage of 40 mg O3/g dry solids (DS) and 0.4 g SBC-FeCe/g DS which were considered as the optimum condition. In view of excellent electron exchanging capacity of SBC-FeCe with rich Lewis acid sites and conversions of valence sates of Fe and Ce, more O3 were decomposed into reactive oxygen species under the catalytic action of SBC-FeCe, which strengthened oxidizing capacity. Enhanced oxidation rendered sludge cells inactivation and compact network structure rupture releasing intracellular water and organic substances. Subsequently, hydrophilic organic matters were attacked and eliminated lessening sludge viscosity and colloidal forces and intensifying hydrophobicity and flowability. In addition, changes of sludge morphology suggested that sludge roughness was alleviated, structural strength and compressibility were raised and porous and retiform structure was constructed providing channels for water outflow by adding skeleton builder of SBC-FeCe. Overall, the synergistic interaction of strengthened oxidation and skeleton construction improved sludge dewaterability.

Enhancement of sludge dewaterability by repeated inoculation of acidified sludge: Extracellular polymeric substances molecular structure and microbial community succession

Improving the dewatering performance of sewage sludge is of great scientific and engineering significance in the context of accelerated urbanization and increasingly strict environmental regulations. Acidified sludge (AS) can improve sludge dewatering performance, but the dewatering effect of repeated inoculation is unclear. The effects of long-term repeated inoculation of AS on the sludge dewaterability were investigated. The molecular structure and microbial community succession of extracellular polymeric substances (EPS) are emphasized. The results revealed that increasing the inoculation ratio of AS reduced the pH, absolute value of sludge zeta potential, and sludge particle size, and the decreasing trend was more evident with prolonging treatment time. Under the conditions of 30% and 50% AS inoculation, the dewatering performance of the sludge was significantly improved (p < 0.05). Compared with the raw sludge, the specific resistance of filtration (SRF) and capillary suction time of 30% inoculation were reduced by 64.3% and 50.1% after 30 cycles, respectively. Excluding loosely bound (LB)-EPS, soluble (S)-EPS and tightly bound (TB)-EPS exhibited a visible decrease, the protein in TB-EPS was significantly related to sludge dewaterability (p < 0.05). The fluorescent components of aromatic protein and fulvic acid-like substances in TB-EPS were significantly associated with SRF, with a correlation coefficient 0.99 (p < 0.05). Both the increase in the percentages of random coil and decrease in α-helix in TB-EPS contributed to improving dewaterability. Increasing Firmicutes and decreasing Chloroflexi levels improved the sludge dewatering capacity. Repeated inoculation did not disrupt the dewatering effect of AS rather increased the feasibility of the engineering application of AS. Considering the dewatering performance and cost synthetically, 30% AS inoculated ratio is feasible for practical applications.

Changes of nitrogen and phosphorus removal pattern caused by alternating aerobic/anoxia from the perspective of microbial characteristics

The purpose of this study was to compare the impact of different numbers of alternating aerobic/anoxic (A/O) cycles on pollutant removal. Three sequential batch reactors (SBRs) with varying numbers of alternating A/O cycles were established. Under the tertiary anoxic operating conditions, the removal efficiencies of chemical oxygen demand (COD), ammonia nitrogen (NH₄⁺-N), total nitrogen (TN), and total phosphorus (TP) were 88.73%, 89.56%, 72.15%, and 77.61%, respectively. Besides, alternating A/O affected the dominant microbial community relative abundance (Proteobacteria and Bacteroidetes) and increased microbial richness and diversity. It also increased the relative abundance of aerobic denitrifying, heterotrophic nitrifying, and denitrifying phosphorus removal bacteria to change N and P removal patterns. Furthermore, the abundance of carbohydrate metabolism and amino acid metabolism was improved by alternating A/O to improve organic matter and TN removal.

Effect of Fe3+ on the nutrient removal performance and microbial community in a biofilm system

In this study, the influence of Fe3+ on N removal, microbial assembly, and species interactions in a biofilm system was determined. The results showed that maximum efficiencies of ammonia nitrogen (NH4+-N), total nitrogen (TN), phosphorus (P), and chemical oxygen demand (COD) removal were achieved using 10 mg/L Fe3+, reaching values of 100, 78.85, 100, and 95.8%, respectively, whereas at concentrations of 15 and 30 mg/L Fe3+ suppressed the removal of NH4+-N, TN, and COD. In terms of absolute abundance, the expression of bacterial amoA, narG, nirK, and napA was maximal in the presence of 10 mg/L Fe3+ (9.18 × 105, 8.58 × 108, 1.09 × 108, and 1.07 × 109 copies/g dry weight, respectively). Irrespective of Fe3+ concentrations, the P removal efficiency remained at almost 100%. Candidatus_Competibacter (10.26–23.32%) was identified as the most abundant bacterial genus within the system. Determinism (50%) and stochasticity (50%) contributed equally to microbial community assembly. Co-occurrence network analysis revealed that in the presence of Fe3+, 60.94% of OTUs in the biofilm system exhibited positive interactions, whereas 39.06% exhibited negative interactions. Within the OTU-based co-occurrence network, fourteen species were identified as key microbes. The stability of the system was found to be predominantly shaped by microbial cooperation, complemented by competition for resources or niche incompatibility. The results of this study suggested that during chemical P removal in wastewater treatment plants using biofilm methods, the concentration of supplemental Fe3+ should be maintained at 10 mg/L, which would not only contribute to P elimination, but also enhance N and COD removal.

High performance, cost-effective and ecofriendly flocculant synthesized by grafting carboxymethyl cellulose and alginate with itaconic acid

Natural polymer flocculant possesses an exciting prospect in water treatment due to its non-toxicity, wide source, low cost and biodegradability. In this work, we have successfully synthesized the anionic terpolymer of carboxymethyl cellulose-itaconic acid‑sodium alginate (CIS) by microwave-assisted copolymerization. By studying the flocculation properties towards cationic dye of crystal violet (CV), the optimum synthesis conditions were determined. The maximum removal rate of 100 mg/L CV simulated wastewater was 92.2 % with CIS concentration of 30 mg/L. The flocculation kinetic results showed the rapid dye removal rate and the dye decolorization ratio of 89.8 % could be obtained at 75 s. Moreover, the CIS flocculant showed excellent flocculation effects in ambient pH of 4-10, flocculation temperature of 10-40 °C, and various inorganic salts. In general, the anionic CIS flocculant shows excellent cost effectiveness, where the predicted operation cost of as-prepared CIS is about 60 % of conventional polyacrylamide flocculant. It also has the advantages of excellent ecofriendliness and rich raw material source, indicative its potential applications of wastewater treatment.

Anode Modification with Fe2O3 Affects the Anode Microbiome and Improves Energy Generation in Microbial Fuel Cells Powered by Wastewater

This study investigated how anode electrode modification with iron affects the microbiome and electricity generation of microbial fuel cells (MFCs) fed with municipal wastewater. Doses of 0.0 (control), 0.05, 0.1, 0.2, and 0.4 g Fe2O3 per the total anode electrode area were tested. Fe2O3 doses from 0.05 to 0.2 g improved electricity generation; with a dose of 0.10 g Fe2O3, the cell power was highest (1.39 mW/m2), and the internal resistance was lowest (184.9 Ω). Although acetate was the main source of organics in the municipal wastewater, propionic and valeric acids predominated in the outflows from all MFCs. In addition, Fe-modification stimulated the growth of the extracellular polymer producers Zoogloea sp. and Acidovorax sp., which favored biofilm formation. Electrogenic Geobacter sp. had the highest percent abundance in the anode of the control MFC, which generated the least electricity. However, with 0.05 and 0.10 g Fe2O3 doses, Pseudomonas sp., Oscillochloris sp., and Rhizobium sp. predominated in the anode microbiomes, and with 0.2 and 0.4 g doses, the electrogens Dechloromonas sp. and Desulfobacter sp. predominated. This is the first study to holistically examine how different amounts of Fe on the anode affect electricity generation, the microbiome, and metabolic products in the outflow of MFCs fed with synthetic municipal wastewater.

A hormesis-like effect of FeS on heterotrophic denitrification and its mechanisms

To alleviate the insufficiency of carbon source in sewage, many sulfur-containing inorganic electron donors were added into traditional heterotrophic denitrification process. However, the effects of extraneous inorganic electron donors on heterotrophic denitrification were still largely unknown. In this study, a hormesis-like effect of ferrous sulfide (FeS, a representative inorganic electron donors) on Paracoccus denitrificans was observed. Total nitrogen (TN) removal efficiency of P. denitrificans rose by 15% with the increase of FeS dosage from 0 to 0.3 g L^-1 (low level), whereas the TN removal significantly decreased to 53% as the dosage of FeS mounted up to 5.0 g L^-1 (high level). Furthermore, the impacts of FeS on glucose utilization and bacterial growth exhibited hormesis-like effects. A subsequent mechanistic study revealed that above influences were caused by its released ions (Fe²⁺, Fe³⁺, and S^2-) rather than particle size. Further study illustrated that low dosage of FeS released a small amount of Fe²⁺ and Fe³⁺, which provided sufficient electrons via promoting glucose utilization, then improved denitrification. Conversely, FeS with high dosage inhibited denitrification via its released S^2-, which suppressed the activity of key denitrifying enzymes rather than influenced glucose metabolism and electron provision. Our results provide an insight into improving denitrification efficiency of the mixotrophic process coexisting with autotrophic and heterotrophic denitrifiers.

Nitrogen removal performance and microbial characteristics during simultaneous chemical phosphorus removal process using Fe3

To evaluate the effect of Fe³⁺ on nitrogen (N) removal and associated microbial characteristics during simultaneous chemical phosphorus (P) removal, a sequencing batch reactor was used to analyze the changes in the microbial community and metabolic pathways caused by Fe³⁺ addition. Results demonstrated that Fe³⁺ promoted ammonia nitrogen (NH₄⁺-N) removal and inhibited denitrification process, and increased the sludge particles (D50) and the biomass per sludge particle size. Furthermore, the abundances of denitrifying bacteria (Haliangium and Terrimonas) and biological phosphorus removing bacteria (Halaingium, norank_f_Saprospiraceae and SM1A02) were decreased. On the contrary, the increase of nitrifying bacteria abundance and the coding genes of nitrification-related enzymes confirmed the promotion for nitrification with Fe³⁺ addition. Besides, Fe³⁺ inhibited the interspecific relationship between denitrifying bacteria genera and other genera to reduce denitrification efficiency.

Biomass hydrogels combined with carbon nanotubes for water purification via efficient and continuous solar-driven steam generation

Solar vapor generation is a promising, environmentally friendly solution for water purification. The development and design of new materials and supporting devices for efficient energy conversion and clean water production are essential for the practical application of solar-driven desalination and water purification. In this study, an environmentally friendly and economical biomass hydrogel-based solar evaporator with a controllable shape was developed in a simple method by integrating carbon nanotubes (CNTs) into a sodium alginate (SA) hydrogel network. The evaporator had a high solar absorption rate (94.3%) and satisfactory hydrophilicity and could effectively avoid salt crystallization during the desalination process. This study took advantage of the aforementioned merits, and a high evaporation rate of 1.699 kg m^-2 h^-1 and a conversion efficiency of 86% were achieved under 1.0 sun irradiation. The evaporator could efficiently remove Na⁺, K⁺, Ca²⁺, and Mg²⁺ from seawater with a removal rate of up to 99.3% and a good decolorization effect on methylene blue (MB) and methyl orange (MO) dye wastewater, whose colour could be completely removed. This study provides a simple, practical, and economical method to prepare hydrogel-based evaporators that utilize abundant solar energy for large-scale desalination and wastewater treatment.

A comprehensive study on simultaneous enhancement of sludge dewaterability and elimination of polycyclic aromatic hydrocarbons by Fe2+ catalyzing O3 process

Simultaneous removal of polycyclic aromatic hydrocarbons (PAHs) in the process of enhancement of sludge dewaterability via oxidation of hydroxyl radicals (•OH) and flocculation of Fe³⁺ by Fe²⁺-catalyzing O₃ were investigated as a novel research focus. The results showed that capillary suction time (CST) and water content of dewatered sludge cake (Wc) were reduced from 57.9 s and 85.1% to 13.6 s and 69.65% under the optimum usage of 60 mg/g dry solids (DS) O₃ and 80 mg/g DS FeSO₄, respectively. The relevant dewatering mechanism of Fe²⁺-catalyzing O₃ treatment was elucidated. It was found that extracellular polymeric substances-bound (EPS-bound) and intracellular water was dramatically released through destroying sludge cells and EPS gel-like structure by produced •OH. In addition, the results of X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) and ¹³C NMR spectroscopy revealed that •OH oxidized and mineralized hydrophilic organic matters intensifying hydrophobicity of sludge surface. Moreover, Fe³⁺ generated by oxidation of Fe²⁺ agglomerated fragmented fine particles into large aggregates and decreased exposure of hydrophilic sites by neutralizing negative charge, which promoted water-solids separation. Meanwhile, sludge surface roughness was decreased which was determined by material type upright confocal laser microscope (CLM). As a consequence, •OH and Fe³⁺ were mainly responsible for enhancement of sludge dewaterability. Moreover, more than 40% of removal rate of PAHs was accomplished by Fe²⁺-catalyzed O₃ treatment mitigating the environmental risks of PAHs spread.

The performance of electrode ultrafiltration membrane bioreactor in treating cosmetics wastewater and its anti-fouling properties

The membrane fouling problem of the membrane bioreactor (MBR) for wastewater treatment reduces the membrane flux and the pollutants removal efficiencies, which is the major obstacle limiting its application and should be properly solved. The combination of membrane and electricity can effectively slow down the membrane fouling rate due to electric repulsion between the pollutants and the membrane. In this study, the performance and the membrane fouling features of an electrode ultrafiltration membrane bioreactor (EMBR) fed with cosmetics wastewater were compared with a conventional ultrafiltration membrane bioreactor (UMBR). The results showed the COD removal efficiency increased by 4.43% and the transmembrane pressure (TMP) reduced by 50% in the EMBR as compared with the UMBR. The specific surface areas of electrode ultrafiltration membrane and conventional ultrafiltration membrane declined by 56.9% and 78.8% after 90 days of operation, respectively. The Protein (PN), polysaccharide (PS) and humic acids (HA) in the cake layer of EMBR were only 61.27%, 78.37% and 34.85% of that of UMBR, which contributed to its loose and porous structure and thus decreased the growth rate of TMP and extended the operation cycle. Extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory calculation proved that the energy barrier between the electrode ultrafiltration membrane and the pollutants was 50% higher than that between the conventional ultrafiltration membrane and the pollutants. Therefore, the strong anti-fouling property of the electrode ultrafiltration membrane could reduce the chemicals dosage and manpower consumption for membrane cleaning and could be preferred for the treatment of cosmetics or alike wastewater containing high concentrations of surfactants and fatty acids.

Chemical analysis of essential oil component, perfume and synthetic essential oil of narcissus and its harmful compounds

Within this work, tazetta, one of the fragrant narcissus species used in the perfume industry, was extracted by steam distillation. The extracts were chemically analyzed by gas chromatography coupled with a mass spectrometer (GC/MS). All substances of perfume, synthetic essence, and essential oil of narcissus flower were prepared and their constituents were identified and compared based on GC/MS results. Their harmful compounds were also identified using MSDS and LD50 methods. According to the obtained information of MSDS and LD50, essential oil of flower, perfume and synthetic essence all contain harmful compounds with many side effects to be considered with extra care for the human health.

Low-temperature synthesis of hetero-structures of magnetically separable iron oxide@Au-rGO nanocomposite for efficient degradation of organic dye under visible light irradiation

In the present study, Fe₃O₄@Au core-shell nanoparticles decorated on reduce graphene oxide (Fe₃O₄@Au/rGO) nanocomposite were synthesized using the reduction method by sodium citrate, Hummer's method, and hydrothermal method, respectively. The as-prepared nanostructures were characterized by X-ray diffraction (XRD), Energy Dispersive X-ray (EDX), transmission electron microscopy (TEM), scanning electron microscopy (SEM)to assess the surface features, crystallinity and morphological characteristics. These nanostructures were employed for photocatalytic degradation of crystal violet (CV), and amongst them, Fe₃O₄@Au/rGO nanocomposite offered the best results under the visible light irradiation and optimal conditions. The effect of the amount of nano-photocatalyst, initial CV concentration, the initial pH, temperature, stirring speed, and degradation time was evaluated individually. A 100% degradation was obtained after 1 min in the presence of 0.008 g nano-photocatalyst, and also 100% of degradation was achieved after 5 min in the presence of 0.005 g of the prepared nano-photocatalyst. After a few tests, its photocatalytic performance was retained, implying the superior stability of Fe₃O₄@Au/rGO nanocomposite. The kinetic study of photocatalytic degradation also indicated that the fit model for the kinetic reaction was the pseudo-second-order kinetic model. Finally, the photocatalytic degradation of real samples with synthesized nanocomposite showed promising results.

Quick and sensitive colorimetric detection of amino acid with functionalized-silver/copper nanoparticles in the presence of cross linker, and bacteria detection by using DNA-template nanoparticles as peroxidase activity

In this project, poly (citric acid) (PCA) functionalized on nano Ag/Cu was synthesized by chemical analysis method. The nano probe was applied to detection of cysteine by using the magnesium (II) ions as a cross linker. The characterization of Ag/Cu/PCA nano probe was studied by using the UV-visible, morphological microscopy, dynamic light scattering, and zeta potential analyzer. The zeta potential and size of Ag/Cu/PCA were -38.0 mV and 18.0 nm, respectively. The prepared nano probe shows rapid response for detection of cysteine. The detection limit of Ag/Cu/PCA nano probe was 0.07 nM. Additional, the Ag/Cu/PCA nanoparticles was applied to cysteine detection from real samples in the presence of amino acids compounds. Rapidly and sensitive determination of Streptococcus pneumoniae is substantial for food safety and human health. The DNA-Ag/Cu/PCA were prepared as a template in chemical method and experimented as a bio-receptor for the cell bacteria detection as peroxidase-like catalytic process. The DNA-Ag/Cu/PCA nano probe shows a linear dynamic concertation range of Streptococcus pneumoniae via detection limit about 65 CFU/mL. The project presents that the DNA-Ag/Cu/PCA could detect the biological and bacterial samples via high accuracy.

Evaluating an economic application of renewable generated hydrogen: A way forward for green economic performance and policy measures

Energy security and environmental measurements are incomplete without renewable energy; therefore, there is a dire need to explore new energy sources. Hence, this study aimed to measure the wind power potential to generate renewable hydrogen (H2), including its production and supply cost. This study used first-order engineering model and net present value to measure the levelized cost of wind-generated renewable hydrogen by using the data source of the Pakistan Meteorological Department and State Bank of Pakistan. Results showed that the use of surplus wind and renewable hydrogen energy for green economic production is suggested as an innovative project option for large-scale hydrogen use. The key annual running expenses for hydrogen are electricity and storage costs, which have a significant impact on the costs of renewable hydrogen. The results also indicated that the project can potentially cut carbon dioxide (CO2) pollution by 139 million metric tons and raise revenue for wind power plants by US$2998.52 million. The renewable electrolyzer plants avoided CO2 at a rate of US$24.9-36.9/ton under baseload service, relative to US$44.3/ton for the benchmark. However, in the more practical mid-load situation, these plants have significant benefits. Further, the wind-generated renewable hydrogen delivers 6-11% larger annual rate of return than the standard CO2 catch plant due to their capacity to remain running and supply hydrogen to the consumer through periods of plentiful wind and heat. Also, the measured levelized output cost of hydrogen (LCOH) was US$6.22/kgH2, and for the PEC system, it was US$8.43/kgH2. Finally, it is a mutually agreed consensus among environmental scientists that the integration of renewable energy is the way forward to increase energy security and environmental performance by ensuring uninterrupted clean and green energy. This application has the potential to address Pakistan's urgent issues of large-scale surplus wind- and solar-generated energy, as well as rising energy demand.

Potential of a mixed culture of microalgae for accumulation of beta-carotene under different stress conditions

Beta-carotene, a pigment found in plants, is mainly produced by microalgae. Nevertheless, this production has only been investigated in pure cultures. Beta-carotene production through mixed culture eliminates the costly procedure of sterilization and contamination prevention needed for pure cultures. In this study, for the first time, the growth, beta-carotene, and chlorophyll production of a mixed culture of microalgae from Caspian Sea was investiagted under different stress conditions. At the condition of tripled light intensity and nitrogen starvation, beta-carotene content increased from 18.03 to 43.8 and 46.5 mol beta-carotene g−1 protein, respectively. However, the salinity of 4 mol L−1 caused the beta-carotene content to fall to zero. The blank sample reached a constant value of 23 mol beta-carotene g−1protein. The comparable results with the specific monoculture species exhibit the high potential of a mixed culture of microalgae for beta-carotene production without need of the high sterilization cost. Nevertheless, more research is needed for where it can be a good substitute for pure culture.

A review study on new aspects of biodemulsifiers: Production, features and their application in wastewater treatment

The effluent produced in refineries is in the form of an oil/water emulsion that must be treated. These emulsions are often stable and a suitable method must be used to separate the oil from the emulsion. Recently, biosurfactants or biodemulsifiers have received much attention to reduce the interfacial tension between two liquids. Biodemulsifiers are produced by microorganisms and have several benefits over chemical demulsifiers such as low-toxic, biodegradability, eco-friendly and easy synthesis. They can eliminate two phases by changing the interfacial forces between the water and oil molecules. Biosurfactants are categorized based on the molecular weight of their compounds (low or high molecular weight). Sophorolipids, lipopeptides rhamnolipids, trehalolipids, glycolipid, lipoproteins, lichenysin, surfactin, and polymeric biosurfactants are several types of biosurfactants, which are produced by bacteria or fungi. This review study provides a deep evaluation of biosurfactants in the demulsification process. To this end, different types of biosurfactants, the synthesis method of various biosurfactants using various microorganisms, features of biosurfactants, and the role of biodemulsifiers in the demulsification process are thoroughly discussed. Also, the impact of various efficient factors like pH, microorganism type, temperature, the oil content in the emulsion, and gravity on biodemulsificaion was studied. Finally, the mechanism of the demulsification process was discussed. According to previous studies, rhamnolipid biodemulsifier showed the highest biodemulsification efficiency (100%) in the removal of oil from an emulsion.

Role of education in poverty reduction: macroeconomic and social determinants form developing economies

Education is the basis for poverty eradication and economic growth. Education provides the aim of this research is to explore educational and other environmental, economic and social determinants on poverty. The aim of this study is to measure an econometric estimation to measure the role of education on poverty reduction. The model was estimated using time series data from 1980 to 2018, using the Engle-Granger two-step co-integration technique, to obtain the economic long-term and short-term dynamic characteristics of education in reducing poverty rate in this era. This model is used to test the hypothesis that how education can uplift the economic progress of the country. Education significantly reduces the level of poverty, whereas the role of higher education seems more significant tool for alleviating poverty. The public and monetary sectors incorporate institutional features with relevant policy actions, while foreign sectors, particularly the oil sector, represent interactions with the rest of the world. A series of policy scenarios influence the industry-wide model, which is used to evaluate the government's various options for increasing economic productivity, resulting in sustained acceleration of growth and poverty reduction in the South Asian economics.

Tribological characterization of graphene oxide by laser ablation as a grease additive

In this work, the structural and tribological behavior of graphene oxide samples as a grease addi-tive was studied. By Nd:YAG laser ablation system and using graphite target at two laser energy of 0.3 W and 0.6 W, graphene oxide (GO) samples were successfully prepared. GO samples were characterized using Raman spectroscopy, field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR) and energy dispersive X-ray spectroscopy (EDAX). Also, tribological behaviors of the lubricating grease, with and without the graphene oxide in grease, by the pin-on disc tribometer were determined. The Raman spectroscopy measurements showed D and G bound, which confirmed the successful synthesis of the graphene oxide sample and also the I D/I G, decreased by increasing laser power due to decreasing disorder in graphene oxide structure. FESEM images show that by ablating carbon atoms from graphite target in water, particles assemble to form a GO micro-cluster due to thermodynamically agglomeration with average size of about 3–4 µm, which the size of them depends on the laser pulse energy. Based on FTIR and EDAX analysis, GO sample which prepared at lower laser energy possessed the highest content of oxygen and oxygen functional groups. In addition, the results of tribological behavior showed that the friction-reducing ability and antiwear property of the grease can be improved effectively with the addition of GO. However, it is revealed that the small size GO has a better lubricating performance and therefore cluster size appears to play a role in the degree of wear protection due to its impact on the physical and chemical properties. The results of this study indicate that the GO sample prepared at lower laser energy (0.3 W) has a smaller size and the higher the oxygen content therefore provide better friction-reducing and anti-wear effect. Also, additive of graphene oxide in lubricating grease decreases coefficient of friction as well as wear. Based on our results, the application of GO as an additive in grease leads to increased performance of the lubricated kinematic machine.

Direct halosulfonylation of alkynes: an overview

The difunctionalization reactions of easily available and inexpensive alkynes have emerged as a reliable, powerful, and step-economical approach for the construction of highly substituted complex alkenes in a one-pot manner, without the need for isolation of intermediates. A wide variety of transformations based on this concept have been successfully achieved for the preparation of synthetically and biologically important β-halovinyl sulfone scaffolds. In this Review, we summarize the recent advances and developments in this field and present a comprehensive overview of halosulfonylation of alkyne substrates with emphasis on the mechanistic features of the reactions.

Design, preparation, and characterization of CS/PVA/SA hydrogels modified with mesoporous Ag2O/SiO2 and curcumin nanoparticles for green, biocompatible, and antibacterial biopolymer film

One of the most significant factors affecting the rapid and effective healing of wounds is the application of appropriate wound dressings. In the present study, novel antibacterial wound dressings are fabricated that consist of Chitosan (CS)/Polyvinyl alcohol (PVA)/Sodium Alginate (SA), which are all biocompatible, functionalized with mesoporous Ag2O/SiO2 and curcumin nanoparticles as reinforcements. In this research nanocomposites are fabricated (0 wt%, 5 wt%, 10 wt%, 15 wt%, and 20 wt% of Ag2O/SiO2). After the composition of nanocomposites using the cross-linked technique, Fourier Transform Infrared (FT-IR) spectroscopy is performed to confirm the functional groups that are added to the polymer at each step. X-ray diffraction (XRD) is done to show the crystallinity of Ag2O/SiO2. Field emission scanning electron microscopy (FE-SEM) studies are performed to demonstrate the morphology of the structure, Energy-dispersive X-ray spectroscopy (EDS) is done to examine the elements in the wound dressing and atomic force microscopy (AFM) study is performed to show surface roughness and pores. Then the nanocomposites with different weight percentages are cultured in three bacteria called Acinetobacter baumannii, Staphylococcus epidermidis, and Proteus mirabilis, all three of which cause skin infections. Finally, by performing the tensile test, the results related to the tensile strength of the wound dressings are examined. The results show that with the increase of Ag2O/SiO2, the mechanical properties, as well as the healing properties of the wound dressing, have increased significantly. Fabricating these nanocomposites helps a lot in treating skin infections.

Application of borophene as catechol sensor: a computational study

The efficacy of borophene (BP) as catechol (CC) sensor was explored using density functional theory (DFT) method. All calculations were performed at B3LYP level of theory and 6-31 + G(d) basis set employing the dispersion correction term of Grimme to consider dispersion interactions. The CC molecule is adsorbed on top of BP horizontally with the adsorption energy (E_ads) of about - 13.5 kcal·mol^-1. The HOMO and LUMO levels of nanosheet destabilize by about 0.36 and 0.14 eV, respectively, going from bare BP to BP-CC complex. Therefore, the E_g value decreases by about 10.5% upon adsorption process, which is a reasonable energy gap change for detection of CC. The negligible difference between the work function values (Φ, defined as the minimum amount of the energy needed to remove an electron from a solid to a point in the vacuum immediately outside the solid surface) of BP and its complex with CC indicates that the BP sheet is not an appropriate Φ-type sensor (in these sensors, adsorption of a chemical changes the gate voltage and produces an electrical signal that leads to the detection of chemical agent) for CC detection. The electrical conductivity of BP becomes 72 times higher after CC adsorption. The time needed for CC desorption from BP sheet is 7.6 ns, based on conventional transition state theory, showing that BP benefits from a short recovery time. The effect of CC concentration was explored by adsorption of 2 and 3 CC molecules on top of BP nanosheet and the results showed that the sensor response does not change by increasing the CC concentration. Also, the effect of lateral dimensions of BP on the adsorption energy was explored and it was shown that E_ads increases by enlargement of the nanosheet.

Direct synthesis of sulfenamides, sulfinamides, and sulfonamides from thiols and amines

Needless to say that organosulfur compounds with sulfur–nitrogen bonds have found various applications in diverse fields such as pharmaceuticals, agrochemicals, polymers, and so forth. Three major groups of such compounds are sulfenamides, sulfinamides, and sulfonamides which have been widely applied as building blocks in medical chemistry. Owing to their significant role in drug design and discovery programs, the search for and development of efficient, environmentally friendly, and economic processes for the preparation of the title compounds is of great importance in the pharmaceutical industry. Recently, oxidative coupling of thiols and amines, two readily available low-cost commodity chemicals, has emerged as a highly useful method for synthesizing structurally diverse sulfenamides, sulfinamides, and sulfonamides in a single step. Since this strategy does not require additional pre-functionalization and de-functionalization steps, it considerably streamlines synthetic routes and substantially reduces waste generation. This review will focus on recent advances and achievements in this attractive research arena.

This review provides a concise overview of the synthesis of biologically and synthetically valuable sulfenamide, sulfinamide, and sulfonamide derivatives through the direct oxidative coupling of readily available low-cost thiols and amines.

Biosynthesis of spinel nickel ferrite nanowhiskers and their biomedical applications

Greener methods for the synthesis of various nanostructures with well-organized characteristics and biomedical applicability have demonstrated several advantages, including simplicity, low toxicity, cost-effectiveness, and eco-friendliness. Spinel nickel ferrite (NiFe2O4) nanowhiskers with rod-like structures were synthesized using a simple and green method; these nanostructures were evaluated by X-ray diffraction analysis, transmission electron microscopy, scanning electron microscopy, and X-ray energy diffraction spectroscopy. Additionally, the prepared nanowhiskers could significantly reduce the survival of Leishmania major promastigotes, at a concentration of 500 μg/mL; the survival of promastigotes was reduced to ≃ 26%. According to the results obtained from MTT test (in vitro), it can be proposed that further studies should be conducted to evaluate anti-leishmaniasis activity of these types of nanowhiskers in animal models.

Application of micro and porous materials as nano-reactors

In general, nanostructured materials with specific size, shape and geometry have unique and different properties from bulk materials. Using reaction media with nanometer and micrometer dimensions, they can produce new nanomaterials with interesting and remarkable properties. In general, nano-reactors are nanometer-sized chambers in which chemical reactions can take place. of course, nanoreactors are somehow part of the reaction, and this is the main difference between them and micro-reactors. One of the useful solutions to achieve the environment of nanoreactors is the use of porous materials, so due to the importance of nanoreactors, porous structures of silicate and zeolite are among the most prominent and widely used compounds in this group.

Amphetamine Drug Detection with Inorganic MgO Nanotube Based on the DFT Calculations

In this study, the main challenge was to focus on the detection of amphetamine (AN) using a type of magnesium oxide nanotube (MgONT) sensor through density functional theory (DFT) calculations. Nowadays, due to the adverse effects of drug abuse, governments put all their efforts into detecting and managing illegal drugs such as AN. Therefore, the detection of AN in biological specimens is of great importance. In this study, through DFT calculations, the intrinsic sensing properties of MgONT were investigated for the detection of AN. We concluded that the MgONT considerably enhances the reactivity of the MgONT toward AN. Furthermore, the sensing response for the MgONT was 392.36. The results showed that there was a considerable change in the energy levels of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) and there was a drop in the band gap value (E_g). This decrease in the E_g value improved the electrical conductivity. Moreover, desorption of AN from the surface of the MgONT had a slight recovery time (~ 22.89 ms). This work illustrated that MgONT could be considered a proper candidate for electronic sensing and AN drug delivery in biological systems.