Mixed Acid Research Articles

Effects of dietary palmitic acid and oleic acid ratio on milk production, nutrient digestibility, blood metabolites, and milk fatty acid profile of lactating dairy cows

Adequate energy supply is a crucial factor for maintaining the production performance in early lactating cows. Adding fatty acids to diets can improve energy supply, while the effect could be related to the chain length and degree of saturation of fatty acids. This study was conducted to evaluate the effect of different ratios of palmitic acid (C16:0) to oleic acid (cis-9 C18:1) on the production performance, nutrient digestibility, blood metabolites and milk fatty acids profile in early lactating dairy cows. Seventy-two multiparous Holstein cows (63.5 ± 2.61 d in milk) blocked by parity (2.39 ± 0.20), body weight (668.3 ± 20.1 kg), body condition score (3.29 ± 0.06), and milk yield (47.9 ± 1.63 kg) were used in a completely randomized design. Cows were divided into 3 groups with 24 cows in every group. Cows in 3 treatments were provided iso-energy and iso-nitrogen diets, whereas the C16:0 to cis-9 C18:1 ratio was different: (1) 90.9% C16:0 + 9.1% cis-9 C18:1 (90.9:9.1); (2) 79.5% C16:0 + 20.5% cis-9 C18:1 (79.5:20.5); (3) 72.7% C16:0 + 27.3% cis-9 C18:1 (72.7:27.3). Fatty acids were added at 1.3% in dry matter basis. Although the dry matter intake fat-corrected milk yield and energy-corrected milk yield were not affected, the milk yield, milk protein yield and feed efficiency increased linearly with the increasing of cis-9 C18:1 ratio. The milk protein percentage and milk fat yield did not differ among treatments, whereas the milk fat percentage tended to decrease linearly with the increasing of cis-9 C18:1 ratio. The lactose yield increased linearly and lactose percentage tended to increase linearly with increasing cis-9 C18:1 ratio, whereas the percentage of milk total solids and somatic cell count decreased linearly. Though the changes of body condition score were not affected by treatments, the body weight loss decreased linearly with the increasing of cis-9 C18:1 ratio. The effect of treatment on nutrient digestibility was limited, except a linear increase in ether extract and neutral detergent fiber digestibility with the increasing of cis-9 C18:1 ratio. There was a linear increase in the concentrations of plasma glucose, whereas the triglyceride and nonesterified fatty acid concentration decreased linearly with the increasing of cis-9 C18:1 ratio. As the cis-9 C18:1 ratio increased, the concentration of de novo fatty acids decreased quadratically, while the mixed and preformed fatty acids increased linearly. In conclusion, increasing cis-9 C18:1 ratio could increase production performance and decrease body weight loss by increasing nutrient digestibility, and the ratio had the most powerful beneficial effect on early lactating cows suggested by 72.7:27.3.

Ultrathin Carbon Sheet Obtained by Self-Template Method toward Highly Effective Charge Transfer for Si-Based Anodes.

A dynamic and stable charge transfer process is the key to exerting lithium storage characteristics of the silicon anode with a large volume change. In this work, the composite with an ultrathin carbon sheet skeleton is prepared by freeze-drying and a copyrolysis process after uniformly mixing citric acid and hydroxylated Si NPs, which is different from traditional conformal carbon coating derived from citric acid. A flexible carbon sheet reduces internal particle (Si-OH@NC) slip and cooperates with interfacial Si-O-C bonding to buffer machinal stress in the electrode during cycling. More importantly, the carbon sheet network increases the point-to-surface contact area between the active material and the conductive agent, ensures continuous electrical connection from the current collector to the active material, and promotes a rapid and stable electron transfer process. Besides, the N-doped C structure with remarkable nucleophilicity guarantees fast ion transport, which is confirmed by theoretical calculation. In this way, the reaction reversibility of the Si-based electrode is further realized during cycles. As a result, the electrode delivers excellent cycle performance (reversible capacity of 1001.9 mAh g-1 at 1 A g-1 after 500 cycles) and rate performance (capacity retention of 86.8 and 65.8% at 1 and 3 A g-1, respectively, compared to 0.2 A g-1). The idea of constructing a highly efficient electrode conductive network through a doped-carbon sheet network is also applicable to other active materials with huge volume changes during lithium storage.

Adsorptive removal of phenol from synthetic wastewater using hexadecyltrimethylammonium bromide-functionalized cellulose nanocrystal (HDTMA-Br/CNCs)

Phenol is nonetheless considered a major pollutant and, therefore should be treated to eliminate the phenol in wastewater to save the environment, people, and organisms from the negative impacts of phenol. This study, for the first time, investigates the synthesis and performance evaluation of hexadecyltrimethylammonium bromide-functionalized cellulose nanocrystals (HDTMA-Br/CNCs) adsorbent for removing phenol from synthetic phenol-containing wastewater. The CNCs were prepared from as-received cellulose, by mixed acid hydrolysis consisting of sulfuric acid, glacial acetic acid, and deionized water in a mass ratio of 1:7:2. The prepared CNCs were functionalized by adding 20 g of the produced CNCs to the HDTMA-Br solution and stirred for 120 min . The synthesized and HDTMA-Br-functionalized CNCs were characterized using different analytical techniques, such as Scanning Electron Microscopy (SEM-EDX) to examine the surface morphology and the elemental composition of the modified and unmodified adsorbents. Fourier Transform Infrared (FTIR) was used to examine the attachment of the functional group. X-ray diffraction (XRD) was used to analyze the crystalline structure of the adsorbent. To evaluate the performance of the synthesized adsorbent in batch mode, 1 g/L of phenol was used to prepare the synthetic phenol-containing wastewater. The analysis of the feed and permeate was done using pre-calibrated High-Performance Liquid Chromatography (HPLC). The multi-BET surface area of CNCs was 24.11 m2 g−1, meanwhile, fCNCs possessed a higher surface area of 201.4 m2 g−1 with a pore volume of 0.069 cm3 g−1. About ∼75 ± 1.4% phenol removal was obtained for the functionalized CNCs compared to the non-functionalized CNCs adsorbent having ∼43 ± 0.1% phenol removal at 35 °C reaction temperature. It could be observed that the spent adsorbent a shows percentage phenol removal of 70.0 ± 0.8% and 35.5 ± 1.4%, for fCNCs and CNCs at the 3rd cycle. The Langmuir and Freundlich isotherms best match the experimental data, while the pseudo-first-order kinetic model provided the greatest fit to the kinetic data. Thus far, the results suggest that modified CNCs may be an alternative adsorption material for phenol removal in wastewater.

Industrial-scale highly efficient nickel recovery from electroplating wastewater using resin adsorption followed by aeration mixing acid regeneration

Cation-exchange resins have been used to recover nickel from electroplating wastewater, but resin regeneration often consumes a large amount of acid and alkali, resulting in low Ni(II) concentrations in regenerating solution. In this study, the industrial-scale Ni(II) recovery from electroplating wastewater using resin adsorption and regeneration was investigated. Two cation-exchange resin tanks and one chelated resin tank in series effectively reduced the nickel concentrations to below 0.1 mg/L. The spent resin could be efficiently regenerated by a novel aeration mixing method, greatly reducing acid and alkali consumption in comparison with the traditional downstream regeneration method. The spent resin was successfully regenerated by 2 bed volume (BV) of 6 % HCl, and the acid utilization ratio was above 99 %. More than 60 g/L of Ni(II) ions in regenerating solution was stably obtained, which benefited the subsequent nickel recovery by electrodeposition. Similarly, H2SO4 was also effective for Ni(II) desorption from the spent resins. The adsorption and regeneration cost was calculated to be ¥ 5.5–9.5/m3 for the electroplating wastewater containing 200–800 mg/L Ni(II) ions, much lower than that by chemical precipitation. This study provided an effective resin regeneration method to consume less regenerants and obtain higher Ni(II) concentrations, making the Ni(II) recovery cost-effective.

Generation of long-chain fatty acids by hydrogen-driven bicarbonate reduction in ancient alkaline hydrothermal vents

The origin of life required membrane-bound compartments to allow the separation and concentration of internal biochemistry from the external environment and establish energy-harnessing ion gradients. Long-chain amphiphilic molecules, such as fatty acids, appear strong candidates to have formed the first cell membranes although how they were first generated remains unclear. Here we show that the reaction of dissolved hydrogen and bicarbonate with the iron-rich mineral magnetite under conditions of continuous flow, alkaline pH and relatively low temperatures (90 °C) generate a range of functionalised long-chain aliphatic compounds, including mixed fatty acids up to 18 carbon atoms in length. Readily generated membrane-forming amphiphilic organic molecules in the first cellular life may have been driven by similar chemistry generated from the mixing of bicarbonate-rich water (equilibrated with a carbon dioxide-enriched atmosphere) with alkaline hydrogen-rich fluids fed by the serpentinisation of the Earth’s iron-rich early crust.

Investigation of the enrichment-purification process and electrochemical performance of kish graphite in dust from blast furnace tapping yard

Kish graphite is a typical byproduct of steel production, and its enrichment and purification are essential prerequisites for its high value and comprehensive utilization. To solve the problem of recovery and application of difficult-to-treat kish graphite with a small particle size obtained from metallurgical dust, kish graphite in blast furnace tapping yard dust was effectively enriched and purified by a comprehensive flotation-acid leaching treatment process in this study. The influence of the flotation agents on the flotation process was explored. The results showed that the optimized flotation agent dosage was 500.0 g·t−1 (collector) and 120.0 g·t−1 (frother), respectively. Based on the optimized flotation scheme, a graphite concentrate (FG) with 79.12 % carbon content and 93.5 % carbon recovery was obtained. After the leaching treatment with a HCl-HF mixed acid solution, the carbon content of the graphite concentrate increased to 95.55 %. The ID/IG value of the graphite concentrate was 0.145, and the average lattice spacing was approximately 0.3354 nm. The SEM results showed that the leaching-treated graphite concentrate (AFG) had a loose, fragment-like structure. When used as an anode material for lithium-ion batteries, The AFG still provided a high reversible capacity of ∼370 mAh·g−1 and excellent coulombic efficiency of 99.6 % after 350 cycles. In addition, an industrial-grade recycling and utilization path for kish graphite based on a circular supply chain strategy was proposed. The results of this study may serve as a conceptual basis for the recovery and application of kish graphite from metallurgical dust.

Optimization of photofermentative biohydrogen production in a mixed volatile fatty acid medium by Rhodobacter sp. MAY2: A response surface methodology (RSM) approach

Biohydrogen production through photofermentation has gained significant attention as it provides a sustainable solution for clean energy supply and addresses wastewater concerns by utilizing volatile fatty acids (VFA) which are produced in dark fermentation. In this study, response surface methodology via a Face-centered Central Composite Design (FCCD) was employed to optimize buffer solution pH, ferric citrate concentration, sodium glutamate concentration to maximize biohydrogen production by Rhodobacter sp. MAY2 with mixed VFA (acetate, propionate, butyrate) as substrates. Results showed that the concentrations of ferric citrate, sodium glutamate, and buffer solution pH positively impact the biohydrogen production of Rhodobacter sp. MAY2. The optimal conditions were shown to be 0.36 mM ferric citrate, 11 mM sodium glutamate, and buffer solution of pH 7. The predicted hydrogen production potential (HPP) at these conditions (661.1 mL/L) was within 2 % of the actual HPP (647.7 mL/L). Kinetic parameters using the modified Gompertz equation showed that the predicted values for maximum potential cumulative H2 production (P), maximum hydrogen production rate (Rm), and lag time (λ) are comparable to those reported in literature. Overall, the study highlighted the potential of a local isolate, Rhodobacter sp. MAY2, for biohydrogen production and the suitable fermentation conditions for its growth.

Improving oil and gas flowability in tight carbonates with a novel solid delayed acid

The economic development of tight carbonate reservoirs requires hydraulic or acid fracturing stimulation. Acid fracturing better activates natural fractures, resulting in increased stimulated reservoir volume and improving oil and gas flowability. In order to solve the problem of excessive acid-rock reaction due to high temperature, this paper screened four kinds of solid forms of acid with the maximum quantity of acid and reaction rate as the index and formed a high temperature-resistant mixed solid acid system with solid organic acid as the main part and inorganic solid acid as the auxiliary part. The maximum quantity of acid produced and effective acid concentration of the system were greater than 50%, and no residue was precipitated after the complete reaction. Dynamic acid-rock rate tests were performed on different types of retarded acid at 140 °C. The test results show that the solid acid dissolves to form a low-viscosity acid solution, and the reaction rate is one order of magnitude lower than that of gelled and cross-linked acids at the same hydrogen ion concentration, and it is little affected by temperature. Moreover, the paper compares the treatment effect of micro-proppants and solid acids on micro-fractures. The results show that the core permeability improvement multiples up to 900 times under low dissolution of solid acid and the formation of oil and gas flow channels with the same scale as micro-proppants. The experimental results demonstrated the ability of solid delayed acid to transport the fracture leading edge at high temperatures and effectively activate micro-fractures.

ANALYSIS OF METABOLIC PATHWAY GENES OF STAPHYLOCOCCUS AUREUS ISOLATED FROM THE MILK OF THE COWS WITH MASTITIS

It is known that the bacteria of the genus Staphylococcus are among the most common bacterial pathogens in the pathogenesis of mastitis. Detailed and comprehensive knowledge of the metabolism of Staphylococcus is necessary to understand its pathogenesis. The aim of the study was to identify the metabolic pathways of S. aureus bacteria isolated from the milk of the cows with mastitis. A total of 88 metabolic pathways were identified for the studied S. aureus. Biosynthesis pathways were strongly dominated in bacteria, the most common of which were biosynthesis of 5-aminoimidazole ribonucleotides, biosynthesis of L-lysine, L-threonine and L-methionine II, biosynthesis of coenzyme A, biosynthesis of L-isoleucine and biosynthesis of uridine monophosphate. A pathway for the synthesis of Nacetylglucosamine has been found in S. aureus bacteria. This pathway may be important for bacterial virulence. The pathway of peptidoglycan III biosynthesis has been discovered. This pathway was previously described for Mycobacteriaceae. In addition, in the cells of S. aureus there have discovered mixed acid fermentation genes, which are more typical for representatives of Enterobacteriaceae. According to the sequencing results, it has been revealed that various folate metabolism pathways are widely represented in S. aureus cells, emphasizing its obvious great importance for this type of bacteria.

Research on how acidification affects the coal's microscopic pore structure in the Guizhou mining region

AbstractBy eliminating their minerals, acidification technology makes coal seams more permeable. Acidification technology were conducted in the Farr and Qinglong mining areas using a mixed acid solution to study the impact of acidification technology on increasing the permeability of primary structural coals in the Guizhou region, China. The microphysical and chemical structure of the coal samples before and after acidification transformation was compared using X‐ray diffraction, scanning electron microscope, mercury intrusion porosimetry, and Fourier transform infrared spectrometry experiments. The results show that after acidification, the volatile matter content is reduced by 4.2% and 16.25%, the carbon content is increased, the degree of coalification is deepened, the gas content of the coal seam is elevated, and the gas source is more abundant. The minerals on the surface are dissolved to different degrees, and the pores and cracks are dredged, so that the surface of the coal samples shows better connectivity, which is conducive to the diffusion and transport of coalbed methane. The volume and pore diameter of the macropore and mesopore in the Farr coal samples were improved after acidification, and the fractal structure was more prominent, the pore connectivity was good, and the pore diameter of the Qinglong coal samples was greatly increased. The content of oxygen‐containing functional groups increased by 11.2% and 2.1%, respectively, which is conducive to the desorption of coalbed methane after acidification, and with the increasing degree of metamorphism of the coal samples, the higher the content of oxygen‐containing functional groups was and the less pronounced the effect of acidification. Acidification technology can effectively remove the minerals in the coal body and has a good effect on penetration enhancement, and the results of the study can provide certain theoretical references for the penetration enhancement of coal seams in Guizhou mining areas.

The Impact of Surface Chemistry and Synthesis Conditions on the Adsorption of Antibiotics onto MXene Membranes.

MXene, a two-dimensional (2D) nanomaterial with diverse applications, has gained significant attention due to its 2D lamellar structure, abundance of surface groups, and conductivity. Despite various established synthesis methods since its discovery in 2011, MXenes produced through different approaches exhibit variations in structural and physicochemical characteristics, impacting their suitability for environmental application. This study delves into the effect of synthesis conditions on MXene properties and its adsorption capabilities for four commonly prescribed antibiotics. We utilized material characterization techniques to differentiate MXenes synthesized using three prevalent etchants: hydrofluoric acid (HF), mixed acids (HCl/HF), and fluoride salts (LiF/HCl). Our investigation of adsorption performance included isotherm and kinetic analysis, complemented by density functional theory calculations. The results of this research pinpointed LiF/HCl as an efficient etchant, yielding MXene with favorable morphology and surface chemistry. Electrostatic interactions and hydrogen bonding between MXene surface terminations and ionizable moieties of the antibiotic molecules emerge as pivotal factors in adsorption. Specifically, a higher presence of oxygen terminations increases the binding affinities. These findings provide valuable guidance for etchant selection in environmental applications and underscore the potential to tailor MXenes through synthesis conditions to design membranes capable of selectively removing antibiotics and other targeted substances.

Is the Invasive Plant Amaranthus spinosus L. More Competitive than the Native Plant A. tricolor L. When Exposed to Acid Deposition with Different Sulfur–Nitrogen Ratios?

The functional differences between invasive plants and coexisting native plants can affect the invasion process of the former because invasive plants and coexisting native plants are exposed to similar or even identical environmental pressures. Acid deposition is an important component of atmospheric pollution, and acid deposition with different sulfur–nitrogen ratios may affect the invasion process of invasive plants by shifting the functional differences and differences in the growth performance between the invasive and coexisting native plants. It is crucial to analyze the functional indices and growth performance of these plants when exposed to acid deposition with different chemical compositions to assess the ecological impacts of atmospheric pollution on the growth performance of invasive plants. This study aimed to evaluate the functional differences and growth performance between the invasive plant Amaranthus spinosus L. and the native plant A. tricolor L. in mono- and mixed culture when exposed to an acid deposition with different sulfur–nitrogen ratios, including sulfur-rich acid deposition (sulfur–nitrogen ratio = 5:1), nitrogen-rich acid deposition (sulfur–nitrogen ratio = 1:5), and mixed acid deposition (sulfur–nitrogen ratio = 1:1). The acidity of the three types of simulated acid deposition was set at pH = 5.6 and pH = 4.5, respectively, with distilled water as a control (pH = 7.0). The competition experiment between A. spinosus and A. tricolor was conducted in the greenhouse. Amaranthus spinosus exhibited a strong growth performance over A. tricolor in the mixed culture, mainly via the increased leaf photosynthetic capacity. The competitiveness for light acquisition, leaf photosynthetic capacity, and enzymatic defense capacity under stress of A. spinosus may be vital to its growth performance. The lower pH acid deposition had imposed a greater reduction in the growth performance of both Amaranthus species than the higher pH acid deposition. Sulfur-rich acid deposition was more toxic to the growth performance of both Amaranthus species than nitrogen-rich acid deposition. Amaranthus spinosus was more competitive than A. tricolor, especially when exposed to acid deposition, compared with just distilled water. Thus, acid deposition, regardless of the sulfur–nitrogen ratio, may facilitate the invasion process of A. spinosus via the stronger growth performance.

Use of Mixed Methanesulfonic Acid/Sulfuric Acid as Positive Supporting Electrolyte and the Study of Ion Crossover in Zn-Ce Redox Flow Battery

The development of a highly efficient and inexpensive energy storage technology is central to the operation of a sustainable smart grid and widespread utilization of intermittent renewable energy sources. An emerging and promising grid-scale technology for electrochemical energy storage is the redox flow battery (RFB). A unique and particularly valuable aspect of the design of RFBs is that their energy and power capacities can be scaled independently. Some of their other advantages include short response time, long life-cycles and no detrimental effects associated with being fully charged or discharged [1]. The Zn-Ce RFB, first developed by Plurion Inc (UK) in 2005 [2], has an open-circuit voltage as high as 2.4 V which is one of the highest among the various RBFs.To further improve the efficiency of Zn-Ce RBFs, the effect of different positive supporting electrolytes on the performance of a bench-scale Zn-Ce RFB has been studied. The effectiveness of mixed methanesulfonic/sulfuric acid, mixed methanesulfonic/nitric acid and pure methanesulfonic acid has been assessed and compared on the basis of the cyclic voltammetry response for the Ce(III)/Ce(IV) redox couple and galvanic charge-discharge of a bench-scale Zn-Ce RFB. We have observed the Ce(III)/Ce(IV) reaction to exhibit faster kinetics and the battery to attain higher coulombic efficiency and long-term performance over ~40 charge-discharge cycles in the mixed 2 mol/L MSA–0.5 mol/L H2SO4 electrolyte compared to that achieved in the commonly used 4 mol/L pure MSA electrolyte due to lower H+ crossover and the prevention of CeO2 precipitation. The coulombic efficiency fade rate in the mixed MSA-H2SO4 electrolyte is 0.55% per cycle over 40 charge-discharge cycles, while the fade rate is 1.26% in the case of 4 mol/L MSA. Furthermore, the positive electrode reaction is no longer the limiting half-cell reaction even at the end of long-term battery charge-discharge operation [3]. Our results show that a mixed MSA–H2SO4 acid electrolyte may be a better option for the positive side of a Zn-Ce RFB as a large-scale energy storage device.At the same time, undesired ion crossover is a practical issue that cannot be neglected since it decreases the concentrations of electroactive species in both negative and positive electrolytes and can cause battery self-discharge and thereby lower battery efficiency and longevity. The concentrations of electroactive species in both the positive and negative electrolytes after each charge-discharge cycle have been monitored as a function of cycle number. We have found that as much as 48.6% of the Zn(II) ions are transported through the Nafion 117 membrane from the negative to the positive electrolyte and 11.1% of Ce(III) ions are transported from the positive to the negative electrolyte by the end of 30 cycles (~55 hours of battery operation). A simple and efficient method to mitigate this problem is to add a certain amount of Zn(II) to the positive electrolyte and Ce(III) to the negative electrolyte at the outset of operation in order to reduce the concentration gradients between the two sides. From our cyclic voltammetry results, the addition of Zn(II) ions into the positive electrolyte has no deleterious effect on the Ce(III)/Ce(IV) redox couple and in fact appears to slightly reduce the separation between the reduction and oxidation peaks, suggesting better reversibility of the positive electrode reaction. In addition, experiments involving 30 cycles of battery charge-discharge have been conducted using Zn(II)-containing pure MSA positive electrolyte as well as Zn(II)-containing MSA-H2SO4 mixed acid electrolytes to analyze battery efficiency. Our results show that both the coulombic and voltage efficiencies are increased compared to that attained using the original electrolytes without Zn(II) initially added to the positive electrolytes. The energy efficiency increases by 19.7% in the case of the Zn(II)-containing pure MSA electrolyte and 6.1% for the Zn(II)-containing H2SO4-MSA mixed acid electrolyte (see Figure 1). Another benefit of adding Zn(II) ions to the MSA pure positive electrolyte is that it prevents the precipitation of CeO2 routinely observed to occur in MSA-only electrolytes after 10 – 15 charge-discharge cycles, which further enhances the energy density of the Zn-Ce RFB.References Nguyen, T. and R.F. Savinell, Flow Batteries. Electrochemical Society Interface, 2010. 19(3), 54.Clarke, R., B. Dougherty, S. Harrison, P. Millington, and S. Mohanta, US Patent 2004/0202925 A1. Cerium Batteries, 2004.Yu, H., M. Pritzker, and J. Gostick, Use of Mixed Methanesulfonic Acid/Sulfuric Acid as Positive Supporting Electrolyte in Zn-Ce Redox Flow Battery. J. Electrochemical Society, 2023. 170(2), 020536. Figure 1

Synergistic performance of mixed agro-waste-based amino acids as kinetic hydrate inhibitors for natural gas hydrate control

The formation of plugs and clogs in pipelines caused by low temperatures and high pressures during drilling and production of natural gas hydrates causes difficulties for the oil and gas sector. Different commercially available kinetic hydrate inhibitors (KHIs) are used to manage this problem; however, they have disadvantages such as toxicity, low biodegradability, and high cost. Through the use of microbiological techniques, this study attempted to synthesize mixed amino acids from agricultural waste to prevent the formation of natural gas hydrates. The performance of mixed agro-waste amino acids (MBL4) was compared to single amino acids (glycine, histidine, proline, and alanine that are major components of MBL4) and PVCap as a control group at dosage of 0.1 and 0.5 wt%. The onset temperature and subcooling were used to assess the performance of the inhibitors in this study, which used the constant cooling method in a stirred high-pressure autoclave at 100 bar. The addition of MBL4 at 0.5 wt% retarded the onset of hydrate formation and increased the subcooling significantly when compared to PVCap and the individual single amino acids, with onset temperature and subcooling of 7.20 °C and 11.67 °C, respectively. The performance of MBL4 is observed to increase from 0.1 to 0.5 wt% dosage concentration, and MBL4 outperformed individual amino acids and PVCap. Mixed agro-waste amino acids showed better performance when used as KHI due to synergism, and this finding can offer a long-lasting, cheaper, and more efficient way of controlling gas hydrate formation in the oil and gas industry.

Theoretical and experimental study of 5-ethoxymethylfurfural and ethyl levulinate production from cellulose

Theoretical simulations and experiments were taken to explore the mechanism of cellulose conversion into 5-ethoxymethylfurfural (EMF) and ethyl levulinate (EL) catalyzed by a mixed acid of Lewis acid and Brønsted acid. Up to 64.8 % total yield of EMF and EL can be obtained when the ratios of Lewis/Brønsted acid and water/ethanol (v/v) were 1:2 and 3:7 respectively. The results showed that Lewis acid and water could reduce the activation energy of EMF formation from 75.6 to 47.9 kJ mol−1, and mixed acids and water/ethanol system were beneficial to the accumulation of EMF. Moreover, the results of molecular dynamics (MD) simulation indicated that Lewis acid could promote the distribution of Bronsted acid around the β-1,4 glycosidic bond of cellobiose. The combination of DFT and frontier molecular orbital (FMO) calculation demonstrated that the breakage of the β-1,4 glycosidic bond was the main rate-limiting step of cellulose hydrolysis. Meanwhile, the mixed acid and water/ethanol system could accelerate the hydrolysis due to the reducing energy barrier and HOMO-LUMO gap. This study gave a deep insight into the mechanism of Lewis acid with Brønsted acid on cellulose conversion into EMF and EL.

Experimental investigation of the impacts of supercritical carbon dioxide on acid-etching fracture morphology and conductivity in tight carbonate reservoir

Carbon dioxide (CO2) as energized fluid has been used for acid-fracturing in tight carbonate reservoir. CO2 is often pumped into the wellbore in liquid phase with acid systems, and transited into supercritical state under the high-temperature formation. While the effect of supercritical CO2 (SC-CO2) on acid-etched fracture morphology and conductivity have rarely been investigated. The acid-etching and conductivity experiments were conducted on the outcrops of the Ma5 sub-member of the Ordo Basin in China. The mixed phase reaction simulation device was developed firstly. These experiments involved the mixing of SC-CO2 with various fluids, including formation water and viscoelastic surfactant (VES) acid, as well as different SC-CO2 concentrations with VES acid. The results show that 100 % SC-CO2 is easy to activate natural fractures without dissolution. After 20%SC-CO2 mixed with formation water, the dissolution ability of the mixed solution and conductivity is only 11.8 % and 1 ∼ 2 % of VES acid respectively. Roughness of the morphology created by the mixture of SC-CO2 with VES acid, exhibits a reduction compared to VES acid-etching, accompanied by the presence of wormholes. Additionally, there is a decrease in conductivity and increase in its retention rate. With the increase of SC-CO2 concentration, the roughness of acid-etching fracture decrease and the injection pressure curve becomes more stable. While the reaction rate is also retarded nearly linearly as the SC-CO2 concentration increases. Especially, when the SC-CO2 concentration is up to 40 %, the acid-rock reaction rate reaches only 55 % of that of VES acid. The conductivity of mixed-acid-etched fracture exhibits a segmented characteristic. During the low-medium closure pressure stage, the acid-etched fracture by VES acid generates high conductivity, specifically when it is below 34.5 MPa. While the higher the SC-CO2 concentration in the mixed acid is, the greater the conductivity and retention rate are at pressures above 34.5 MPa during high closure pressure stage. The conductivity of SC-CO2 acid-fracturing fracture depends on the non-uniform etching of the acid solution. The increase in SC-CO2 concentration of the mixed acid not only enhances conductivity and retention rate under high closure pressure, but also reduces the acid volume required for acid-fracturing.

Preparation of high-purity SiO2 by S-HGMS coupled with mixed-acid leaching: A case study on hematite tailings from Ansteel, China

Hematite tailings (HTs) are rich in silica and are used as replacements for fine aggregates in the preparation of construction materials. However, there is scope for a more effective utilization of the valuable elements present in HTs. In this paper, a process for preparing high-purity SiO2 using HTs procured from Ansteel (China) is proposed. HTs were treated using the superconducting high-gradient magnetic separation (S-HGMS) technology, where the silica as part of the nonmagnetic fraction was obtained in the form of a high-silica concentrate, which was then subjected to mixed-acid leaching to dissolve impurities to achieve refined purification. The optimum process conditions for S-HGMS were determined, and the response surface methodology was applied to optimize the process parameters of the mixed-acid leaching process. The process indicators of the mixed-acid leaching step included the leaching time, leaching temperature, and molar ratio of the mixed acids. The optimum process conditions for S-HGMS were as follows: the magnetic strength-to-velocity ratio in the weak magnetic separation stage was set to 0.034 T·s/m whereas it was maintained at 0.076 T·s/m in the strong magnetic separation stage; the pulp concentration was 40 g/L, the pulp velocity was 500 mL/min, and the dispersant concentration was 1 mg/g. Under these conditions, the high-silica pulp was processed. The corresponding SiO2 grade increased from 71.788 % to 95.260 %, and its recovery and yield reached 56.330 % and 42.450 %, respectively. The SiO2 content in the sample increased from 95.260 % to 99.961 %. Further, the mechanisms of the S-HGMS and mixed-acid leaching were revealed. The proposed process is environmentally friendly and operationally inexpensive. It can reduce the amount of HTs by 42.450 %, and the obtained high-purity silica product has high economic value and good industrialization prospects.

Fully biomass-derived polyurethane based on dynamic imine with self-healing, rapid degradability, and editable shape memory capabilities

In this study, a novel bio-based diol containing imine dynamic bonds (Vanp2) were synthesized using vanillin and bio-based 1,5-pentanediamine. Vanp2 was then introduced into the cross-linking network of betulin-based polyurethanes to obtain betulin-based polyurethanes containing covalent adaptive networks (CANs). Imine dynamic bonds within CAN endowed these betulin-based polyurethanes with self-healing, re-processability, degradability, and editable shape memory functionalities. Meanwhile, the mechanical and thermal properties of these fully bio-based polyurethane materials were characterized. The maximum tensile strength reached 9.5 MPa, while the maximum strain at break was 248 % and the maximum toughness was 13.2 MJ/m3. Thermal decomposition temperature was greater than 300 °C. Since the imine structure could be dissociated under acidic conditions, these polyurethanes could be rapidly degraded in a mixed acid solution at 50 °C in 4 h. This study demonstrated a strategy for synthesizing betulin-based polyurethane elastomers containing CAN using only bio-based feedstock.

The influence factors of dielectric barrier discharge plasma to production of syngas derived from H2S-CO2 acid gas

H2S and CO2, two harmful acid waste gases, often co-exist in important chemical production such as coal-chemical industry, natural gas chemical industry and petrochemical industry, causing corrosion of industrial equipment and pipelines, and must be treated innocuously. Co-conversion of H2S-CO2 mixed acid gas to syngas has been carried out using dielectric barrier discharge (DBD) plasma-catalysis, which renders the highly corrosive and toxic H2S and greenhouse gas CO2 harmless, and produces syngas. The effects of various parameters of the DBD plasma on the reaction of one-step conversion of H2S-CO2 to syngas were studied. Moreover, a comparative study of the different parameters of DBD plasma was carried out. The intrinsic correlation between the reaction performance of syngas production via H2S-CO2 conversion and these parameters, including specific energy input (SEI), discharge shape, discharge frequency, discharge gap and discharge length, was investigated and revealed. On this basis, a multi-tube parallel DBD plasma reaction system was designed and constructed.

Heavy metals, macro-minerals and human health risk assessment of spiced and unspiced tiger nut drink commercialized in Port Harcourt, Rivers State, Nigeria

The need for cheap, nutritional, refreshing and local content development has increased the demand and consumption of Tiger nut drink by residents of Port Harcourt and its environs in recent years. However, the inadequate nutritional information and without nutritional facts label has made it difficult for the Tiger nut consuming populace to ascertain its health benefits. Hence, the objective of this paper was to investigate the concentrations of selected heavy metals (Pb, Ni, Fe, Cu, and Zn), macro-minerals (Mg and Ca) and human health risk assessment of spiced and unspiced Tiger nut drink commercialized in Port Harcourt, Rivers State, Nigeria using standard analytical techniques after mixed acid digestion. The mineral elements were found in the order of Mg (79.87 mg/L) > Ca (50.79 mg/L) and Mg (96.82 mg/L) > Ca (68.18 mg/L) in unspiced and spiced tiger nut drinks respectively [< WHO: Mg (150 mg/L), Ca (200 mg/L)] while heavy metals concentrations in the samples analyzed were Fe (1.82 mg/L) > Zn (1.16 mg/L) > Cu (0.4160 mg/L) and Fe (2.12 mg/L) > Zn (1.51 mg/L) > Cu (0.45 mg/L) in unspiced and spiced tiger nut drinks respectively. Pb and Ni were undetected (< 0.00 mg/l) in both unspiced and spiced gingered tiger nut drinks studied. Only Fe and Cu concentrations exceeded WHO standards (0.3 and 0.02 mg/L). However, intake of these heavy metals is unlikely to pose any non-carcinogenic health risk to consumers (target hazard quotient (THQ) < 1, HI<1 for adults and children) in both spiced and unspiced tiger nut drink. Generally, results from this study showed higher concentrations of metals in spiced tigernut drink than in the unspiced tiger nut drink. This could be attributed to the combined bioaccumulated levels of heavy metals in the tiger nut tubers and in the spice used. Frequent consumption of spiced tiger nut drink may rapidly increase the levels of heavy metals in the human body and pose chronic risk to human health and also beneficially increase the levels of macrominerals in the body. Standard production processes and regulated spicing of tiger nut drink needs to be provided by regulatory agencies (NAFDAC) and made available to producers of tiger nut drink.