Solid Carbon Source Research Articles

Performance and mechanisms for V(v) bio-reduction by straw: key influencing factors.

A high concentration of vanadium [V(v)] in groundwater is extremely harmful for humans. Weak movability and low toxicity after microbial V(v) reduction have attracted remarkable attention, especially for using solid carbon sources. However, the influencing factors remain unclear. In this study, the initial V(v) concentration, inocula amount and straw dosage were examined to ascertain the mechanisms behind them. Increasing the initial V(v) concentration led to the decrease of the V(v) removal efficiency, which was also positively correlated with the straw dosage within a certain range. The initial sludge amount was not a main factor affecting microbial V(v) removal in this study. With the initial amount of 10 mg L−1 V(v), 25 mL initial inocula and 5 g straw, 88.2% of V(v) was removed. According to the dissolved organic matter (DOM) analysis results, microbial activity prevailed in groups with higher V(v) removal efficiency, indicating that the V(v) bio-reduction was attributed to the microbial activity, which was considered a major factor. Functional species as unclassified_f_Enterobacteriaceae presumably contributed to the V(v) bioreduction, with upregulated ABC transporter genes and enzymes.

Enhanced simultaneous removal of nitrate and phosphate using novel solid carbon source/zero-valent iron composite

Abstract Excessive discharge of nitrate and phosphate to aquatic environment can induce bad eutrophication phenomenon. Simultaneous removal of nitrate and phosphate is challenging for that the low C/N ratios and trace phosphate in wastewater concentration limit advanced nitrate and phosphate removal, respectively. In this study, a novel iron based solid carbon source composite namely solid carbon source/zero-valent iron was prepared by solid carbon sources and zero-valent iron for advanced simultaneous removal of nitrate and phosphate. The novel composite with 30% zero-valent iron weight ratio presented best simultaneous removal performance with 1.1 ± 0.1 mg NO3–N/(L·h) and 0.21 ± 0.07 mg PO43--P/(L·h). The initial pH effects on the removal performance of the novel composite showed that initial pH = 7 remarkably enhanced the nitrate removal (1.1 ± 0.1 mg NO3–N/(L·h)) and phosphate concentration declined fastest (0.14 ± 0.07 mg PO43--P/(L·h)) at initial pH = 5.5. Physical and chemical characterization of the composite confirmed the zero-valent iron oxidation and hydroxidation process after used and phosphate adsorption and precipitation were involved in this process. Microbial communities at genus level on the surface of the composite were identified to be capable of complex carbon hydrolysis and decomposition and denitrification, demonstrating the dominant role of microbial denitrification in nitrate removal. Interestingly, the observation of nitrate reducing Fe(II)-oxidizing bacteria suggested the synergistic effect of autotrophic and heterotrophic denitrification. The novel composite exhibited simultaneous removal of nitrate and phosphate effectively and can be applied in nutrients control in wastewater such as secondary effluent.

Initial Validation of a Replicated Field-scale Denitrifying Bioreactor Facility in a Boreal Environment

Denitrifying bioreactor technology, where a solid carbon source (woodchips) acts as a reactive medium to intercept agricultural tile drainage water, has been successfully used to convert N (NO3-) to di-nitrogen (N2) gas. Four replicated field-scale (24 m long x 3 m wide x 1 m deep), bioreactors were built and operated at the St. John’s Research and Development Centre and were successful at removing a notable amount of nitrate (N) from agricultural subsurface drainage water. The objective of this study was to investigate the internal flow dynamics of one of these field-scale bioreactors as a proxy for the others. The hydraulic conditions in the bioreactor system developed differently than expected; asymmetric flow rates led to long average hydraulic retention time (HRT) and a highly dispersed residence time distribution, which was revealed by a sodium chloride tracer test. To measure the internal flow a known amount of sodium chloride (salt) was added to water before it entered the bioreactor and samples were collected in 30 minutes intervals. The temperature of water samples taken from the inlet, outlet, and sample ports ranged from 14.5 to 18.4°C With a N removal of 62 to 66% the bioreactor proved at the same time to be very effective under the boreal environment of Newfoundland and Labrador (NL). Mass removal rate (MRR) was calculated to evaluate the performance of woodchip bioreactor. The average MRR was 3.87 gm-3day-1 and the highest was 7.19 gm-3day-1 respectively. The theoretical retention time was calculated to be approximately 10.64 h based on the active flow volume, the length and depth of the system. In comparison the observed retention was 18.18 h

Growth of high-quality wafer-scale graphene on dielectric substrate for high-response ultraviolet photodetector

Growth of graphene on dielectric substrates is crucial for its use in various electronic and optoelectronic devices, which may avoid the additional extrinsic defects and residual pollution originating from the essential transfer process of graphene grown by chemical vapor deposition on metal foils. However, the growth of high-quality and wafer-scale graphene on dielectric substrates is now still a challenge. Herein, we report the growth of graphene from solid polymer carbon source on various substrates under the assistance of Nickel/SiO2 capping layer. The wafer-scale graphene with excellent uniformity and continuity was achieved on 2 inch sapphire substrates. The dynamics of the graphene growth were proposed, which mainly consist of polymer carbonization, carbon dissolution, segregation and precipitation. The graphene was also grown on undoped GaN to serve as the carrier transport channel of ultraviolet photodetectors, exhibiting a 4 A/W response. The growth of high-quality and wafer-scale graphene on dielectric substrates reported by present work would promote commercial application of the graphene-based electronic and optoelectronic devices.

Solubilization of Heavy Metals during Anaerobic Digestion of Sewage Sludge Using Acidogenesis

Sewage sludge produced by many municipal wastewater treatment plants contains various heavy metals that limit its use on agricultural land. The existing treatment processes for removing heavy metals are not cost-effective or eco-friendly due to the requirement of aeration or the use of various harmful leaching agents. This paper explores the solubilization of heavy metals present in the sewage sludge using the acidogenesis phase of the anaerobic digestion process without using any harmful compounds. To achieve this objective, an anaerobic batch reactor was used, in which sewage sludge was added with different solid concentrations and carbon source (glucose) concentrations. During this process, volatile fatty acids were produced, which decreased the pH of the system. The maximum decrease in the pH was observed in the reactor that had the maximum glucose concentration and the minimum total solid concentration. In this reactor, the pH dropped below 4.5. The solubilization of heavy metals was observed as Zn: 41% (333 mg/kg), Ni: 31% (8.5 mg/kg), Cr: 30% (13 mg/kg), Pb: 29% (11 mg/kg), Co: 28% (1.4 mg/kg), and Cd: 27% (0.5 mg/kg).

Effect of processing temperature on growing bamboo-like carbon nanotubes by chemical vapor deposition

The present article demonstrates a simple, eco-friendly route for the fabrication of carbon nanotubes (CNTs) with different morphologies, including the fascinating bamboo-like structures without complex catalyst/support preparation procedures. A thermal chemical vapor deposition (CVD) technique that utilized natural pozzolan supports and a solid carbon source, that is, a mixture of camphor and ferrocene in a weight ratio of 20:1, was carried out at different temperatures where the ferrocene played also the role of catalyst. The pozzolan chemical composition and mineral identification were determined by energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy. The morphology of the fabricated CNTs was studied via scanning and transmission electron microscopies (SEM and TEM). It was revealed that both conventional tubular and bamboo-like nanotubes grow at 750 °C while the bamboo-like morphology prevails at 850 °C. The better nanostructure uniformity at higher deposition temperature was accompanied by an improved nanotube graphitization degree that was verified by Raman spectroscopy. Yet, the reduction of the CNTs production yield was recorded by thermogravimetric analysis (TGA). The experimental data are interpreted and discussed as an interplay between the CNTs processing temperature, morphology and growth mechanism. Thus, the growth of either tubular or bamboo-like nanostructures is suggested to be ruled by the competitive surface and bulk diffusions of carbon onto and into the catalyst surface. The growth depends on the size of catalyst nanoparticles sintered at different temperatures. The favorable role of the pozzolan supporting materials in the formation of bamboo-like tubes is emphasized.

Effect of HRT and BDPs types on nitrogen removal and microbial community of solid carbon source SND process treating low carbon/nitrogen domestic wastewater

A novel simultaneous nitrification and denitrification (SND) process using biodegradable polymers (BDPs) as the biofilm carrier and carbon source was developed to remove nitrogen from low-carbon sewage. The effects of BDPs types and hydraulic retention time (HRT) on nitrogen removal and microbial community composition were investigated. The results suggested that HRT parameters were tested in a range from 40h to 3h, and nitrogen removal performance was significantly worse with short HRT (13h to 3h). The NH4+-N and total nitrogen (TN) removal rates of the polycaprolactone (PCL) reactor reached to 98.40 % and 89.14 % at the optimal HRT (13h), respectively, and polybutylene succinate (PBS) reactor reached to 85.73 % and 81.64 %, respectively. When HRT was decreased from 13h to 3h, the NH4+-N removal rate of the PCL and PBS reactors were reduced to the lowest values of 55.43 % and 33.47 %, and the removal rate of TN also reduced to 55.53 % and 44.88 %. According to Illumina MiSeq sequencing and correlation analyses, the genera Methyloversatilis, Bdellovibrio, and Zoogloea were significantly, positively correlated with nitrogen removal rate and short HRT, and short HRT impacted TN removal through increasing the abundance of these genera. LEfSe analysis revealed that the differences observed between PCL and PBS reactors were dependent on differences in Methyloversatilis, ultimately resulting in differences in microbial communities related to nitrogen removal. KEGG analysis suggested that nitrification-related functional genes (amoA, amoB, amoC, and hao) had the greatest abundance in the 13h HRT condition, and denitrification-related functional genes (napA, napB, nasA, nirS, and nosZ) were generally more abundant in the PBS system than the PCL system.

Supplemental carbon sources applied in biofloc technology aquaculture systems: types, effects and future research

AbstractBiofloc technology (BFT) systems have been driven towards increased sustainability in the last decade. BFT depends on maintenance of the optimal carbon‐to‐nitrogen (C/N) ratio through supplementation with organic carbon sources. The types of carbon sources and addition strategies are critical considerations in BFT systems. Thus for the purpose of this review, a thorough search of the literature was conducted to gather relevant information from reliable sources, ranging from reputable journals to books and useful reports in the field of BFT. Keywords used for the literature search include: ‘biofloc technology systems’, ‘carbon sources’, ‘solid carbon sources’, ‘effects of carbons sources’, ‘carbon source addition strategies’, ‘nutritional quality of bioflocs’, ‘carbon sources and water quality’, ‘C/N ratio in BFT’, and ‘carbon sources and bacterial community’. Among the several peer‐reviewed articles, books and technical reports consulted, 147 (dated from 1987 to 2020) were relevant for the preparation of this review. The current review thus examines the subject of supplemental carbon sources in BFT systems and discusses the various effects of their application with respect to the culture organism, microorganisms, water quality and the nutritional quality of flocs. The benefits and challenges associated with the types of carbon sources used in BFTs are also presented. Suggested organic carbon sources and their addition strategies are provided, and further research directions are proposed.

Tellurium-assisted and space-confined growth of graphene single crystals

Low-temperature synthesis of large-area graphene films by chemical vapor deposition (CVD) method has attracted extensive research interests owing to their extraordinary potential applications. Current reports on the low-temperature graphene growth usually involve catalytic metal substrates, which exceedingly impedes the direct use of graphene in nanoelectronic fabrications. In this project, we design a space-confined growth chamber utilizing two SiO2/Si chips. The bottom chip loading pre-transferred graphene flakes accommodates the growth of second monolayer graphene, with a tellurium (Te) vapor assisted growth process. Polymethylmethacrylate (PMMA) residues introduced from the transferred graphene substrate is employed as the solid carbon source. Further, the numerical simulation results prove that the high concentration of active carbons in the confined space plays a vital role in this growth process. Density functional theory (DFT) calculations reveal that, Te atoms prefer to bond with the edge carbons of small graphene flakes and serve as an effective catalyst, which helps to grow small graphene flakes by reducing their energy of formation. The successful growth can provide the high-quality monolayer graphene grains at the low temperature (∼350 °C). This facile strategy promises the mass production of graphene at mild conditions and low costs, which contributes to the green chemistry in future.

Nitrogen-doped hollow carbon spheres synthesized from solid precursor and its application in lithium ions batteries

Hollow carbon spheres (HCSs) materials have been investigated extensively for various applications in energy storage, catalysis, electrochemical conversion. At present, template method using liquid or gaseous carbon sources is the dominant synthetic route for HCSs. Herein, HCSs with high nitrogen doping levels are synthesized by employing graphitic carbon nitride (g-C3N4) solid precursor as carbon and nitrogen sources with the presence of Zn templates. The successful synthesis of N-doped HCSs using solid g-C3N4 precursor is confirmed by a series of characterization technologies. Serving as the anode materials in lithium ions batteries, promising lithium ions storage performances are obtained for the resultant N-doped HCSs. Brilliant specific capacities of 1506.6 mAh g−1 at 0.1 A g−1 and 519.2 mAh g−1 at 5 A g−1 are recorded after 360 cycles. The promising lithium ion storage performances of the N-doped HCSs are ascribed to the unique hollow structure with large surface area, suitable nitrogen doping level and large inner pore volume. The presented work provides a new route to synthesize HCSs or heteroatoms doped HCSs materials using solid carbon sources.

Comparative analysis of denitrification performance, denitrifying community and functional genes to oxytetracycline exposure between single and hybrid biodegradable polymers supported solid-phase denitrification systems.

Biodegradable carrier are vital for the solid-phase denitrification (SPD) systems for treating nitrate-rich water. Two solid-phase denitrification reactors were developed with both 200g L-1 of single (polycaprolactone, PCL) (R1) and hybrid solid carbon sources (PCL/polylactic acid (PLA) /polyhydroxyalkanoates (PHA)) (R2) to examine the denitrification performance, denitrifying community and functional genes to various oxytetracycline (OTC) exposure in this study, respectively. Complete denitrification performance was achieved in the both SPD systems at low stress of OTC (1mg L-1), but then dramatically reduced to less than 20% of nitrate reduction efficiency after one-month high OTC stress (10mg L-1), and rapidly recovered to stable nitrate removal rates of 76.77 ± 5.48% (R1) and 40.68 ± 4.40% (R2) after the next day of no OTC stress. However, the reactor R1 with single PCL carriers acquired more efficient nitrate removal rate than that of reactor R2 at the high OTC stress and recovery phase with OTC stress, mainly due to the more organics availability from the single PCL carriers. The richness and diversity of nirK and nirS deintrifiers significantly declined at high OTC stress, and much more of those occurred in biofilm R1 with more organics availability. Besides, biofilm R1 achieved much more abundant periplasmic nitrate reductase, nitrite reductase genes and tetracycline resistance genes after high OTC stress, which explained the potential resistance to OTC and rapid recovery efficiency after no stress of OTC. Thus, the organics availability played an important role in assuring SPD system to be efficient under high OTC stress.

Primary sludge as solid carbon source for biological denitrification: System optimization at micro-level

Commercial carbon source (e.g. methanol) has been frequently used to enhance heterotrophic denitrification for nitrate removal. However, this is not sustainable due to the high cost of chemical purchasing and excessive sludge production. To address these issues, this study reports an integrated denitrification system using primary sludge as solid carbon source. Complete denitrification without any nitrite accumulation achieved at the primary sludge dosage of 6.0 g VSS/g N with the maximum specific nitrate reduction rate of 6.4 mg N/g VSS/h, which was comparable with the reported soluble carbon source. More importantly, as a solid “waste” in municipal wastewater treatment plants (WWTPs), the primary sludge was simultaneously reduced by 65.3%–85.1%, and this avoids the intensive denitrification biomass generation that generally occurs in using the commercial carbon source. Ammonium, phosphate, and recalcitrant organic matter were released meantime. Interestingly, the concentration of ammonium and phosphate declined during the denitrification process. The refractory dissolved organics mainly composed of aromatic protein and microbial by-products. The detailed cycle study suggests that an appropriate denitrification cycle/duration time would largely lower the effluent organics concentration, which can be achieved by monitoring the pH turning point. This study clearly demonstrates that primary sludge is a promising alternative carbon source for biological denitrification with great economic benefits and environmental sustainability.

Optimization of the pollutant removal in partially unsaturated constructed wetland by adding microfiber and solid carbon source based on oxygen and carbon regulation

The partially unsaturated constructed wetland was demonstrated to be able to enhance the oxygen supplement for the microbial nitrification. However, the fast gravity flow of wastewater on the smooth surface of substrate in unsaturated zone led to a short contact time between wastewater and biofilm on the surface of substrate for the microbial pollutant oxidation process. While, the strengthened oxygen supplement also consumed organic carbon, intensifying the shortage of electron donator for the denitrification process. To further enhance the efficiency of both nitrification and denitrification processes, two strategies were conducted as follows: (1) adding microfiber in unsaturated zone to extend the hydraulic retention time (HRT) and improve the oxygenating efficiency; (2) adding slow-release carbon source (Poly butylenes succinate, PBS) as electron donor in saturated zone for denitrification. Results showed that the ammonia oxidation efficiency reached up to 97.0% in the microfiber-enhanced constructed wetland. Additionally, adding microfiber provided more sites for microbes and increased the total number of microbes in unsaturated zone. The addition of PBS in the saturated zone obviously improved the denitrification efficiency with the total nitrogen (TN) removal rate raising from 20.6 ± 4.0% to 90.4 ± 2.7%, which excellently solved the problem of poor denitrification efficiency caused by low ratio of carbon to nitrogen (C/N). In conclusion, the association of microfiber and PBS in partially unsaturated constructed wetland finally accomplished the thorough nitrogen removal.

Direct growth of CVD graphene on 3D-architectured substrates for highly stable tactile sensors

A novel method was developed for the direct chemical vapor deposition (CVD) synthesis of graphene on a 3D-architectured insulator substrate, with a conformal and uniform contact formed between the graphene and substrate and with this composite applied to the fabrication of a highly sensitive 3D-architectured sensor. The synthesis involved a UV/ozone treatment of a 1,2,3,4-tetraphenylnapthalene (TPN) solid carbon source film on a pre-patterned 3D-structured substrate to result in an enhancement of the surface adhesion at the interface between the TPN film and the substrate, with this enhancement having prevented the sublimation of the TPN from the substrate at the temperature used to grow the graphene. The substrate-adhered TPN was fully converted, with low defect density, to graphene on the 3D-architectured substrate. The graphene synthesized in this way showed both excellent surface adhesion and continuity even at the sloping edges of the substrate, and can thus be used as electrodes or interfacial passivation layers in highly stacked 3D-structured electronic devices. Also, it was shown to improve the electrical operational stability of a fabricated electronic tactile sensor. The proposed method for the synthesis of graphene directly on 3D-architectured substrates is expected to have wide applications in highly integrated 3D-structured electronics.

Amorphous carbon to graphene: Carbon diffusion via nickel catalyst

Graphene can be synthesized via metal catalysis using solid carbon source. In this paper, graphene was fabricated using amorphous carbon. We further elucidated the process of carbon diffusion and graphene formation at low temperatures using a comprehensive experimental and theoretical strategy. The diffusion barrier of carbon in nickel crystal is different from that of carbon along nickel grain boundaries, resulting in that the layer of graphene is uncontrollable. Based on our findings, we identified the causes of graphene heterogeneity and the process of carbon diffusion.

Strategies for Scalable Gas-Phase Preparation of Free-Standing Graphene

The preparation of graphene with high quality serves as a prerequisite for its usage. Traditional methods of graphene production, represented by liquid-phase exfoliation and chemical vapor depositi...

Recent developments in the synthesis of graphene and graphene-like structures from waste sources by recycling and upcycling technologies: a review

Among carbon-based nanomaterials, graphene and its derivatives have received remarkable attention due to their unique thermal, mechanical, and electronic properties and two-dimensional structure. The unique combination of graphene’s characteristics with the selected matrix exhibits extraordinary synergies in various fields such as energy, automotive, aerospace, and electronics. However, there are serious bottlenecks for the industrialization of graphene and increasing the number of graphene-based products in mass scale owing to high cost, harsh and toxic reaction conditions, agglomeration of nanosheets and limited production capacity. Therefore, the new trends focus on the usage of waste sources to produce value-added products in order to contribute waste management and circular economy. This review summarizes underlying and emerging trends for the development of recycling and upcycling methods for cost-efficient and mild synthesis of graphene and its derivatives from waste sources such as plastics, agricultural biomass waste, and cellulosic waste. The state of the research activities provides better understanding in the fabrication of graphene-like materials from waste products as solid carbon sources by using top-down and bottom-up approaches.

Simultaneous nitrate and dissolved organic matter removal from wastewater treatment plant effluent in a solid-phase denitrification biofilm reactor

In the present study, an up-flow solid-phase denitrification biofilm reactor (US-DBR) was established for simultaneous nitrate and dissolved organic matter (DOM) removal from wastewater treatment plant effluent. After 100 days operation, the nitrate and COD removal efficiencies were high of 97% and 80%, respectively. According to EEM-FRI analysis, aromatic and tryptophan protein-like, humic-like and fulvic acid-like substances were identified in DOM. Additionally, protein-like substances in DOM components were much easier transformed as carbon source for denitrification. Moreover, protein secondary structure of DOM changed significantly due to the biodegradation and microorganisms metabolic process. High-throughput sequencing analysis implied that Simplicispira, Diaphorobacter, Hydrogenophaga, Pseudoxanthmonas and Stenotrophomonas were the dominate genera in the whole of US-DBR, that were responsible for the removal of nitrate, organics and degradation of solid carbon source, respectively. This study provided a further biological basis about practical application of solid-phase denitrification for simultaneously remove nitrate and organic matter.

Development of a denitrification system using primary sludge as solid carbon source – Potential to couple with anammox process

Heterotrophic denitrification is a robust and reliable process for nitrogen removal from wastewater. However, wastewater often faces the issue of lacking carbon source. In this study, the feasibility of using primary sludge, a by-product of wastewater treatment plants, to support denitrification of high-strength nitrite wastewater was investigated. Results suggest the desired performance can be achieved with the influent nitrite concentration of 400 to 1200 mg N/L, and the optimal primary sludge dosage for the complete nitrite removal was 3.6 g VSS/g N. Ammonium removal was also detected along with nitrite removal. Microbial analysis reveals various types of denitrifying bacteria and a large number of macromolecular organics degrading bacteria existed in the microbial community. Notably, anammox bacteria, Candidatus Brocadia, was also identified with an abundance of 0.1%. The slow kinetics of carbon source release from primary sludge was likely the reason for the existence of anammox process. This study developed a promising nitrogen removal process using an alternative carbon source for denitrification, and it shows great potential to couple denitrification with anammox to reduce ammonium residue.

Comparison of agricultural wastes and synthetic macromolecules as solid carbon source in treating low carbon nitrogen wastewater

This paper investigated the feasibility of using agricultural wastes and synthetic macromolecules as solid carbon sources and studied the effects of improvement of denitrification by the selected agricultural wastes. The carbon release capacity and denitrification performance of corncob (CC), peanut shell (PS), obsolescent rice (OR) and polycaprolactone (PCL), poly butylene succinate (PBS), polyvinyl alcohol sodium alginate (PVA-SA) were systematically analyzed. The results showed that for each carbon source, the first-order kinetic equation was basically followed during the carbon release process. PVA-SA, CC and PS had higher carbon release capacity with accumulative dissolved organic carbon (DOC) of 16.22–20.63 mg·g−1 and chemical oxygen demand (COD) of 100.86–134.10 mg·g−1. Correspondingly, they showed excellent denitrification performance with almost no residual NO3−-N, and the denitrification process well followed the Monod equation. PCL, PBS and OR had lower carbon release capacity with accumulative DOC of 2.06–3.14 mg·g−1 and COD of 13.29–24.13 mg·g−1, respectively. Nevertheless, these materials can also improve the denitrification performance, with the residual NO3−-N in the range of 6.02–6.36 mg·L−1, and the effluent DOC was in the range of 10–15 mg·L−1. Synthetic polymers are more suitable for nitrogen removal in groundwater treatment, while agricultural wastes are ideal carbon sources for secondary effluent treatment.