Carbon Substrate Research Articles

The fate and biostimulant potential of metal lactates in silt loam soil

AbstractConventional farming practices have negatively impacted micronutrient fertility and overall soil health. Metal lactates are an organic micronutrient amendment that provide both a labile carbon substrate as well as mineral nutrition for plant and microbial growth. To determine the ability of metal lactates to provide readily available micronutrients, Zn, Cu, Mn, Ni, and Co in lactate and chloride salt form were amended to soils and incubated for 28 days. Operationally defined speciation was determined using sequential extraction on samples incubated for 1, 5, or 28 days. The results show a comparable distribution of metals in chloride and lactate form; however, differences were detected in water‐soluble and exchangeable Ni and Zn at each timepoint. For example, in the water exchangeable fraction, there was 2.6%–2.9% less Ni and 0.2%–0.3% less Zn in the metal lactate‐treated soil compared to soil treated with metal chlorides. Furthermore, carbonate‐bound Ni averaged 4.1% and 4% less in metal lactate‐treated soils as compared to metal chloride‐treated soils on days 1 and 5, and Cu decreased 2.9%–3.3% during the treatment period for the lactate‐bound form. Additionally, microbial phospholipid fatty acid (PLFA) was performed and found a stimulatory effect of metal lactates on bacterial biomass with an increase of 12%–18% relative to the metal chloride treatment. Results from this study support the use of metal lactates as a sustainable alternative to conventional fertilizers by providing bioavailable micronutrients for plant nutrition in addition to a labile carbon source to support the growth of microbial populations.

Carbon substrates promotes stress resistance and drug tolerance in clinical isolates of Candida tropicalis.

Candida tropicalis is a human pathogen and one of the most prevalent non-Candida albicans Candida (NCAC) species causing invasive infections. Azole antifungal resistance in C. tropicalis is also gradually increasing with the increasing incidence of infections. The pathogenic success of C. tropicalis depends on its effective response in the host microenvironment. To become a successful pathogen, cellular metabolism, and physiological status determine the ability of the pathogen to counter diverse stresses inside the host. However, to date, limited knowledge is available on the impact of carbon substrate metabolism on stress adaptation and azole resistance in C. tropicalis. In this study, we determined the impact of glucose, fructose, and sucrose as the sole carbon source on the fluconazole resistance and osmotic (NaCl), oxidative (H2O2) stress adaptation in C. tropicalis clinical isolates. We confirmed that the abundance of carbon substrates influences or increases drug resistance and osmotic and oxidative stress tolerance in C. tropicalis. Additionally, both azole-resistant and susceptible isolates showed similar stress adaptation phenotypes, confirming the equal efficiency of becoming successful pathogens irrespective of drug susceptibility profile. To the best of our knowledge, our study is the first on C. tropicalis to demonstrate the direct relation between carbon substrate metabolism and stress tolerance or drug resistance.

Submerged macrophyte restoration enhanced microbial carbon utilization in shallow lakes

Submerged macrophytes are integral to the functioning of shallow lakes through their interaction with microorganisms. However, we have a limited understanding of how microbial communities in shallow lakes respond when macrophytes are restored after being historically extirpated. Here, we explored the interactions between prokaryotic communities and carbon utilization in two lakes where submerged macrophytes were restored. We found restoration reduced total carbon in sediment by 8.9 %–27.9 % and total organic carbon by 16.7 %–36.9 % relative to control treatment, but had no effects on carbon content in the overlying water. Sediment microbial communities were more sensitive to restoration than planktonic microbes and showed enhanced utilization of simple carbon substrates, such as Tween 40, after restoration. The increase in carbon utilization was attributed to declines in the relative abundance of some genera, such as Saccharicenans and Desertimonas, which were found weakly associated with the utilization of different carbon substrates. These genera likely competed with microbes with high carbon utilization in restored areas, such as Lubomirskia. Our findings highlight how restoring submerged macrophytes can enhance microbial carbon utilization and provide guidance to improve the carbon sequestration capacity of restored shallow lakes.

Optimisation of dairy-based media using response surface modelling to increase yields of Lacticaseibacillus rhamnosus promoting an enhanced immune response

This study optimised biomass production of health-promoting bacteria by optimising cultivation media using design of experiments methodology. Screening of seven lactic acid bacteria were conducted, where Lacticaseibacillus rhamnosus LRH30 (L. rhamnosus LRH30) was selected as the most suitable candidate for further optimization. Response surface modelling was employed to optimise four dairy-based carbon sources: lactose, whey permeate (WP), demineralised whey (DW) and skim milk powder (SMP), in conjunction with yeast extract and peptone using a central composite design. SMP was identified as the best-suited carbon substrate for high biomass yields, with optimal media concentrations of 12.5 g L−1 lactose, 2.36 g L−1 yeast extract and 2.36 g L−1 peptone in shake flasks and later in batch bioprocess, resulting in biomass quantities of 6.5 g L−1. Additionally, the immunomodulatory effects of L. rhamnosus LRH30 were confirmed in an enzyme-linked immunosorbent assay (ELISA) that showed a significant reduction of tumour necrosis factor (TNF)-α.

Highly dispersed nickel-copper bimetallic catalysts prepared by monolayer NiCu-layered double hydroxide nanocomposites for CO2 electrocatalytic reduction

The design of novel electrocatalyst for CO2 reduction reaction to available chemical substance is a meaningful approach to mitigate the CO2 emission problem. However, it is challenging to achieve uniform dispersion of the metals in the carbon substrate to enhance catalytic performance. Surprisingly, layered double hydroxide nanosheets have uniform metal distribution, which are appropriate metal negative supports for CO2RR catalyst. Herein, we have successfully prepared a simple, green and efficient novel CO2RR metal catalyst using monolayer NiCu-LDH nanocomposites as precursor. Based on solid phase exfoliation, monolayer NiCu-LDH nanocomposite material was obtained, and then the ultra-thin two-dimensional carbon substrate with homogeneous metals dispersion was formed by in-situ nitridation. The obtained Ni2Cu1-CN shows excellent CO2RR performance with CO current density of 12.65 mA cm−2 and great CO faraday efficiency of 96.9 % at −0.8 V (vs. RHE). But metals formed nanoparticles due to vibration migration at high temperature, which caused active sites to be obscured. Surprisingly, introduction of Zn prevented Cu and Ni metals from agglomerating and exposed more active sites. The as‐prepared Ni2Cu1Zn1-CN shows excellent catalytic performance with the greatest CO faraday efficiency of 98.1 % and high CO current density of 16.6 mA cm−2 at −0.8 V (vs RHE) and remarkable stability.

Monosymmetric Fe-N4 sites enabling durable proton exchange membrane fuel cell cathode by chemical vapor modification.

The limited durability of metal-nitrogen-carbon electrocatalysts severely restricts their applicability for the oxygen reduction reaction in proton exchange membrane fuel cells. In this study, we employ the chemical vapor modification method to alter the configuration of active sites from FeN4 to the stable monosymmetric FeN2+N'2, along with enhancing the degree of graphitization in the carbon substrate. This improvement effectively addresses the challenges associated with Fe active center leaching caused by N-group protonation and free radicals attack due to the 2-electron oxygen reduction reaction. The electrocatalyst with neoteric active site exhibited excellent durability. During accelerated aging test, the electrocatalyst exhibited negligible decline in its half-wave potential even after undergoing 200,000 potential cycles. Furthermore, when subjected to operational conditions representative of fuel cell systems, the electrocatalyst displayed remarkable durability, sustaining stable performance for a duration exceeding 248 h. The significant improvement in durability provides highly valuable insights for the practical application of metal-nitrogen-carbon electrocatalysts.

Response of Anaerobic Granular Sludge Reactor to Plant Polyphenol Stress: Floc Disintegration and Microbial Inhibition

Plant polyphenols are potential inhibitors for the anaerobic treatment of wastewater from the wood processing, pharmaceutical, and leather industries. Tannic acid (TA) was selected as a model compound to assess the inhibitory effect of plant polyphenols in simulated wastewater in this study. The influences of TA on methanogenic activity, sludge morphology, and the microbial community were investigated under glucose and sodium acetate as carbon substrates, respectively. The results show that a threshold concentration of TA above 1500 mg·L−1 that triggers significant methanogenesis depression and volatile fatty acids (VFAs) accumulation. In addition, granules might be weakened by TA addition, reflected in changes in extracellular polymeric substances (EPS) within the granules and an increase in floc in the effluent. The anaerobic granular sludge (AnGS) fed with sodium acetate was more sensitive than the presence of glucose as the substrate when facing the challenge of TA. The concentration of the mcrA gene in granular sludge decreased markedly in response to TA stress, providing direct evidence that a high concentration of TA caused the inhibition of specific gene expressions. This study provides details about the adverse impacts of TA stress on methane production, the microbial community, and granule integrity, deepening our understanding of the anaerobic treatment of plant polyphenols contained in wastewater.

Revealing the origin of single‐atom W activity in H2O2 electrocatalytic production: Charge symmetry‐breaking

AbstractThe low‐energy electrochemical production of hydrogen peroxide (H2O2) has garnered significant attention as a viable alternative to traditional industrial routes, with the goal of achieving carbon neutrality. For their H2O2 selectivity in the two‐electron oxygen reduction reaction (ORR), the coordination environment of tungsten (W)‐based materials is critical. In this study, atomically dispersed W single atoms were immobilized on N‐doped carbon substrates by a facile pyrolysis method to obtain a W single‐atom catalyst (W‐SAC). The coordination environment of an isolated W single atom with a tetra‐coordinated porphyrin‐like structure in W‐SAC was determined by X‐ray photoelectron spectroscopy and X‐ray absorption spectroscopy analysis. Notably, the as‐prepared W‐SAC showed superior two‐electron ORR activity in 0.1 M KOH solution, including high onset potential (0.89 V), high H2O2 selectivity (82.5%), and excellent stability. By using differential phase contrast‐scanning transmission electron microscopy and density functional theory calculations, it is revealed that the charge symmetry‐breaking of W atoms changes the adsorption behavior of the intermediates, leading to enhanced reactivity and selectivity for two‐electron ORR. This work broadens the avenue for understanding the charge transfer of W‐based electrocatalytic materials and the in‐depth reaction mechanism of SACs in two‐electron ORR.

Habitat of the amphibious mudskipper Periophtalmodon schlosseri in Songkhla Lake, Thailand

Abstract. Pattaratumrong MS, Pompha T. 2024. Habitat of the amphibious mudskipper Periophtalmodon schlosseri in Songkhla Lake, Thailand. Biodiversitas 25: 1875-1881. This study aimed to investigate the preferred habitat of giant mudskippers, Periophtalmodon schlosseri Pallas 1770. It was conducted from August to October 2022 at six sampling stations in Koh Yoh, a small island in the Lower Songkhla Lake. Environmental parameters such as organic matter and organic carbon in sediment, temperature, salinity, dissolved oxygen, and substrate were observed. The results indicate that the density of giant mudskipper weak to moderate correlates with all studied environmental parameters (P<0.05). Within the study area, the highest population density of P. schlosseri was recorded in the mudflat habitat adjacent to mangroves, and the lowest density was recorded in the mudflat habitat with a seawall, absent with nearby mangroves. This study suggests that environmental conditions affect the abundance of giant mudskippers, but this does not reach the limiting threshold; the more influential factor for this species is the character of the habitat. The mangrove habitat should be conserved and protected from development and urbanization. These results provide insights into the preferred habitat and offer a better understanding of the ecology of these fishes in the estuarine lake.

Boron-doped g-C3N4 supporting Cu nanozyme for colorimetric-fluorescent-smartphone detection of α-glucosidase

BackgroundDue to that the higher activity of nanozymes would bring outstanding performance for the nanozyme-based biosensing strategies, great efforts have been made by researchers to improve the catalytic activity of nanozymes, and novel nanozymes with high catalytic activity are desired. Considering the crucial role in controlling blood glucose level, strategies like colorimetric and chemiluminescence to monitor α-glucosidase are developed. However, multi-mode detection with higher sensitivity was insufficient. Therefore, developing triple-mode detection method for α-glucosidase based on great performance nanozyme is of great importance. ResultsIn this work, a novel nanozyme Cu–BCN was synthesized by loading Cu on boron doped carbon substrate g-C3N4 and applied to the colorimetric-fluorescent-smartphone triple-mode detection of α-glucosidase. In the presence of H2O2, Cu–BCN catalyzed the generation of 1O2 from H2O2, 1O2 subsequently oxidized TMB to blue colored oxTMB. In the presence of hydroquinone (HQ), the ROS produced from H2O2 was consumed, inhibiting the oxidation of TMB, which endows the possibility of colorimetric and visual on-site detection of HQ. Further, due to that the fluorescence of Mg-CQDs at 444 nm could be quenched by oxTMB, HQ could also be quantified through fluorescent mode. Since α-glucosidase could efficiently hydrolyze α-arbutin into HQ, the sensitive detection of α-glucosidase was realized. Further, colorimetric paper-based device (c-PAD) was fabricated for on-site α-glucosidase detection. The LODs for α-glucosidase via three modes were 2.20, 1.62 and 2.83 U/L respectively, high sensitivities were realized. SignificanceThe nanozyme Cu–BCN possesses higher peroxidase-like activity by doping boron to the substrate than non-doped Cu–CN. The proposed triple-mode detection of α-glucosidase is more sensitive than most previous reports, and is reliable when applied to practical sample. Further, the smartphone-based colorimetric paper-based analytical device (c-PAD) made of simple materials could also detect α-glucosidase sensitively. The smartphone-based on-site detection provided a convenient, instrument-free and sensitive sensing method for α-glucosidase.

Regulation of fiber surface nucleation kinetics via ordered nitrogen-rich carbon dots

Three dimensional (3D) carbon-based current collectors have attracted much attentions as host for Li metal anodes (LMAs) owing to their lightweight, flexible, and wide sources etc. However, the lithiophobic nature of carbon makes it difficult to achieve low nucleation overpotential and dendrite-free Li deposition. Herein, carbon dots (CDs) with nitrogen (N)-rich were introduced to modify carbonized cotton fiber (CCF) coated by reduced graphene oxide (CD@RGCCF). Coating graphene oxide (GO) increases the active site of cotton fiber (CF), which facilitates the growth of CDs on the surface of CF fiber. The introduction of ordered structure CDs drives fast migration of Li+ in the “highway-like” channels and induces the uniform nucleation of Li in the initial stage. As a result, the obtained CD@RGCCF decreases the nucleation overpotential of Li, and achieves dendrite-free Li deposition. the CD@RGCCF|Li half cells exhibit extending cycling life over 5000 h with a voltage hysteresis of 10.5 mV at 2 mA cm−2. As coupled with the LiFePO4 (LFP), the Li@CD@RGCCF||LFP composite anode enables a high reversible specific capacity and improved cycle stability. This work provides a low-cost modification method for carbon substrate to realize dendritic-free LMAs.

Elucidating deposition process of calcium carbonate and mechanical properties of precipitation via molecular dynamics simulation

Brittle cracking is a critical issue affecting the load bearing capacity and service life of concrete. Microbially induced calcium carbonate precipitation can heal concrete cracks, but the relation between its microscopic morphology and macroscopic mechanical properties remains poorly understood. This study employs molecular dynamics simulations to investigate the deposition processes of calcite and aragonite unit cells on calcium carbonate substrates. The deposition process of a single unit cell can be divided into two stages: collision rebound and adsorption. The deposited unit cells combine to form amorphous calcium carbonate. Local disordering of substrate upper-surface caused by unit cell collision reduces the tensile strength of the substrates, while the ductility of amorphous precipitations enhances its failure strain. The deposition velocity significantly impacts the mechanical properties of the precipitations. At higher temperature, greater molecular mobility enhances cohesive strength within the precipitations. Aqueous environments can weaken the collisional impacts of deposited unit cells on the substrate. Matching the substrate and deposited unit cell types facilitates ordered structures and strengthens precipitations. This work deepens the understanding of deposition process of calcium carbonate on the substrate and the mechanical properties of precipitations.

Organic matter decomposition in mountain peatlands: effects of substrate quality and peatland degradation

Abstract Background and Aims Peatlands occupy only 3% of Earth’s terrestrial lands but store about one-third of global soil carbon. However, these large carbon stocks are currently under threat due to peatland degradation, where altered hydrological balance could enhance peat oxidation; thus releasing large amounts of CO2 into the atmosphere. We investigated the interactive effects of substrate quality, peat depth and peatland degradation on the decomposition rate of organic matter in peatlands by way of a field incubation experiment. Methods We incubated high-quality fresh peat and a lower-quality degraded peat substrate at three different depths (5, 15, and 30 cm) in two (intact and degraded) mountain peatlands for 18 months. Our results indicated that there is a significant interactive effect of substrate quality, peat depth, and peatland type on the peat decomposition rate. Results The fresh peat showed significantly higher decomposition rates than the degraded peat substrate, likely due to the high percentage of bioavailable carbon in the fresh moss substrate. In the degraded peatland, fresh peat at 30 cm showed no mass loss during the incubation period, likely due to the high-water table creating anaerobic conditions. The fresh peat incubated in the intact peatland showed a higher decomposition rate than the same substrate incubated in the degraded peatland due to the comparatively lower water table in the intact peatland. Conclusions Our findings indicate that the quality of the substrate being decomposed and the depth of the water table act as the main factors affecting the decomposition rate in mountain peatlands.

Flash heating process for efficient meat preservation

Maintaining food safety and quality is critical for public health and food security. Conventional food preservation methods, such as pasteurization and dehydration, often change the overall organoleptic quality of the food products. Herein, we demonstrate a method that affects only a thin surface layer of the food, using beef as a model. In this method, Joule heating is generated by applying high electric power to a carbon substrate in <1 s, which causes a transient increase of the substrate temperature to > ~2000 K. The beef surface in direct contact with the heating substrate is subjected to ultra-high temperature flash heating, leading to the formation of a microbe-inactivated, dehydrated layer of ~100 µm in thickness. Aerobic mesophilic bacteria, Enterobacteriaceae, yeast and mold on the treated samples are inactivated to a level below the detection limit and remained low during room temperature storage of 5 days. Meanwhile, the product quality, including visual appearance, texture, and nutrient level of the beef, remains mostly unchanged. In contrast, microorganisms grow rapidly on the untreated control samples, along with a rapid deterioration of the meat quality. This method might serve as a promising preservation technology for securing food safety and quality.

Heavy metal application of response surface optimized-lipopeptide biosurfactant produced by Pseudomonas aeruginosa strain CGA-02 in low-cost substrate

Cost-effective methods of biosurfactant production with minimal environmental impact are needed as global demand continues to increase. This study evaluated lipopeptide biosurfactant production in a Pseudomonas aeruginosa strain CGA-02 using a low-cost carbon substrate. The structural properties of the biosurfactant and applicability of the biosurfactant in heavy metal removal were evaluated. Response surface methodology (RSM) involving central composite design (CCD) was used to optimize process parameters to maximize biosurfactant production. The study identified sugar cane molasses and sodium nitrate as carbon and nitrogen sources of choice for bacterial growth and biosurfactant production, with a relatively 2.64-fold increase in biosurfactant yield under optimized conditions. Analysis of the biosurfactant measured a surface tension reduction of water from 72.2 ± 0.26 to 30.5 ± 0.2 mN/m at 40 mg/L critical micelle concentration. GC–MS and FTIR analysis revealed structural properties of the lipopeptide biosurfactant, with fatty acid components predominantly 9-octadecenoic acid (oleic acid), n-hexadecanoic acid, cyclotetrasiloxane and trimyristin, and infrared peaks belonging to amine, carboxyl, nitrile, alkanol, ether and carbonyl groups. Capture of heavy metals using the biosurfactant was evaluated in soil microcosms. Removal rates of 80.47, 100, 77.57, 100, and 97.57% were recorded for As, Pb, Hg, Cd and Cr respectively after 12 weeks of incubation. There was no significant difference (p < 0.05) in the removal efficiency of the biosurfactant and an analogous chemical surfactant, sodium dodecyl sulphate. First and second-order kinetic models described heavy metal removal rates by the biosurfactant. We demonstrate the production of a useful biosurfactant using low-cost waste carbon.

Highly Transparent and Flexible Multiwalled Carbon Nanotube–Polyimide Films with Enhanced Electrical Performance as Promising Electrodes

AbstractTransparent and light films with high electrical conductivity are preferred for flexible electronic applications. Here, a film exhibiting high transparency, electrical conductivity, and flexibility is produced using a polyimide (PI) substrate and multiwalled carbon nanotubes (MWCNTs) through spray coating. Cost‐effective MWCNTs are used instead of other electrically conductive materials, including silver nanowire ink, single‐walled carbon nanotubes (SWCNTs), and other carbon materials. The average sheet resistance of the prepared MWCNT–PI film is 520.2 Ω □−1 (infinite for the bare PI film), which is lower than the sheet resistances of the SWCNT–PI film reported by another group. This can be attributed to the increase in electrical conductivity of the highly transparent PI film due to the use of MWCNTs. The transparency of the MWCNT–PI film is 71.834% at 550 nm. When MWCNTs and PI are combined, MWCNTs protrude from the surface of the PI film, creating networks and increasing electrical conductivity. Atomic force microscopy analysis reveals that MWCNT networks form on the surface of the MWCNT–PI film. This study suggests the possibility that MWCNTs can also be used as carbon materials for flexible and highly transparent films.

A Quick Joule‐Heating Coupled with Solid‐Phase Synthesis for Carbon‐Supported Pd–Se Nanoparticles Toward High‐Efficiency Electrocatalysis

AbstractWith respect to the potential of palladium (Pd)‐based nanomaterials in catalyzing typical electrochemical reactions, herein, a strategy that couples the quick Joule‐heating with a solid phase synthesis for producing carbon‐supported Pd–Se nanoparticles with welcome features is reported, e.g., fine sizes, clean surfaces, and controlled crystal phases toward electrocatalysis of oxygen reduction reaction (ORR) and ethanol oxidation reaction (EOR) in an alkaline medium. Principally, the introduction of Se into Pd alters its electronic properties and weakens the adsorption of key reaction intermediates on the Pd–Se nanoparticles during the ORR and EOR process, thus endowing them with better electrocatalysis for the same electrochemical reactions. Impressively, the carbon‐supported Pd–Se nanoparticles exhibit phase‐dependent electrocatalysis toward ORR and EOR. In particular, the cubic Pd17Se15 nanoparticles supported on carbon substrate show mass activity of 0.206 A mgPd−1 and specific activity of 0.546 mA cm−2 at 0.9 V for ORR in 0.1 m KOH electrolyte, while the orthorhombic PdSe2 nanoparticles show a mass activity of 3.79 A mgPd−1 for EOR, higher than that of their cubic counterpart and commercial Pd/C catalyst. The universality of this synthetic strategy in manufacturing carbon‐supported noble metal chalcogenide nanoparticles and highlighting its potential in designing highly efficient electrocatalysts are emphasized.

Methylotrophic bacteria from rice paddy soils: mineral-nitrogen-utilizing isolates richness in bulk soil and rhizosphere.

Methanol, the second most abundant volatile organic compound, primarily released from plants, is a major culprit disturbing atmospheric chemistry. Interestingly, ubiquitously found methanol-utilizing bacteria, play a vital role in mitigating atmospheric methanol effects. Despite being extensively characterized, the effect of nitrogen sources on the richness of methanol-utilizers in the bulk soil and rhizosphere is largely unknown. Therefore, the current study was planned to isolate, characterize and explore the richness of cultivable methylotrophs from the bulk soil and rhizosphere of a paddy field using media with varying nitrogen sources. Our data revealed that more genera of methylotrophs, including Methylobacterium, Ancylobacter, Achromobacter, Xanthobacter, Moraxella, and Klebsiella were enriched with the nitrate-based medium compared to only two genera, Hyphomicrobium and Methylobacterium, enriched with the ammonium-based medium. The richness of methylotrophic bacteria also differed substantially in the bulk soil as compared to the rhizosphere. Growth characterization revealed that majority of the newly isolated methanol-utilizing strains in this study exhibited better growth at 37°C instead of 30 or 45°C. Moreover, Hyphomicrobium sp. FSA2 was the only strain capable of utilizing methanol even at elevated temperature 45°C, showing its adaptability to a wide range of temperatures. Differential carbon substrate utilization profiling revealed the facultative nature of all isolated methanol-utilizer strains with Xanthobacter sp. TS3, being an important methanol-utilizer capable of degrading toxic compounds such as acetone and ethylene glycol. Overall, our study suggests the role of nutrients and plant-microbial interaction in shaping the composition of methanol-utilizers in terrestrial environment.

Using rice straw-augmented ecological floating beds to enhance nitrogen removal in carbon-limited wastewater

Agricultural biomass used as solid carbon substrates in ecological floating beds (EFBs) has been proven to be applicable in nitrogen removal for carbon-limited wastewater treatment. However, the subtle interactions among plants, rhizosphere microorganisms, and supplementary carbon sources have not been thoroughly studied. This study combined rice straw mats with different aquatic macrophytes in EFBs to investigate denitrification efficiency in carbon-limited eutrophic waters. Results showed that rice straw significantly enhanced the nitrogen removal efficiency of EFBs, while enriching nitrogen-fixing and denitrifying bacteria (such as Rhizobium, Rubrivivax, and Rhodobacter, etc.). Additionally, during the denitrification process in EFBs, rice straw can release humic acid-like fraction as electron donors to support the metabolic activities of microorganisms, while aquatic macrophytes provide a more diverse range of dissolved organic matters, facilitating a sustainable denitrification process. These findings help to understand the synergistic effect of denitrification processes within wetland ecosystems using agricultural biomass.

Effect of zirconia coating on Ti6Al4V at elevated substrate temperature on its wear, corrosion and hemocompatibility properties

Titanium and its alloys have been recognized as biocompatible materials since decades although these materials can at times show wear, corrosion and thrombosis leading to various health complications. Surface coating has been found to be one of the effective techniques to overcome this issue in-vitro as well as in-vivo. In this paper, thin film coating of zirconia (ZrO2) on Ti6Al4V is reported using pulsed laser deposition (PLD) technique at elevated substrate temperatures ranging from room temperature to 800 °C (TiZr800). The morphology, composition, wettability and average surface roughness of the samples were analyzed by scanning electron microscope, Raman spectrometer, water contact angle (WCA) and profilometer, respectively. Adhesion between film and substrate was qualified using Elcometer. The tribological studies were performed in ball-on-disc against ZrO2 counterpart, the electrochemical potential analysis was done in simulated body fluid to replicate body environment and the hemocompatibility test was evaluated on the basis of human whole blood adsorption and distribution of Red Blood Cells (RBCs) on the samples. The results revealed an increase in WCA and film adhesion with increased substrate temperature. At 800 °C, formation of zirconium carbide, a relatively harder material, was observed due to diffusion of substrate carbon into ZrO2 film, as confirmed by the Raman analysis. In comparison to pristine, TiZr800 sample showed a reduction in wear rate from 3.5 × 10−3 mm3/Nm to 1.1 × 10−3 mm3/Nm indicating improved resistance of the sample against abrasive wear. Further, drop in Icorr from 4.96 × 10−7 A/cm2 to 2.75 × 10−7 A/cm2 resulted in a 44 % increase in corrosion protective efficiency of the sample coated at 800 °C. Additionally, a 4.5 fold increase in RBC counts was observed on TiZr800 sample. Therefore, it is inferred that while ZrO2 coating can improve overall surface properties of Ti–6Al–4V, additional benefits can be obtained by performing PLD at higher substrate temperatures, more so when the temperature is such as to promote formation of ZrC in the coating.