Concentration Of KOH Solution Research Articles

Mass transfer limitation phenomena across the separator in a zero-gap alkaline water electrolysis stack: Anion-selective polymer electrolyte membrane vs. Zirfon™ Perl UTP 500 case study

Endeavours to decrease the KOH concentration in a circulating medium represent an important target of today's research. They are connected with current efforts to increase the flexibility of alkaline water electrolysis and improve its efficiency with regard to renewable energy sources. This study reports on the impact of reduced KOH solution concentration on mass and charge transport in a laboratory alkaline water electrolysis stack with two separator types. The separators used are a homogeneous anion-selective polymer-electrolyte membrane based on chloromethylated polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene copolymer functionalised by 1,4–diazabicyclo[2.2.2]octane and a commercial composite porous Zirfon™ Perl UTP 500 diaphragm. The stack was assembled in zero-gap mode and a bipolar connection of the electrodes was used. Load curves were recorded for different KOH concentrations and operational temperatures to assess the performance of the stack. Surprisingly, mass transfer limiting behaviour of the stack was observed at KOH concentrations below 2 wt% KOH for the Zirfon™ Perl UTP 500 separator. This was not the case for the stack utilising an anion-selective membrane as a separator. A 1-dimensional, single cell, stationary mathematical model was developed and implemented to clarify this phenomenon and to understand the details of the mass transport across the different types of separators in this process. This information is crucial for understanding obstacles faced once the concentration of KOH approaches zero, i.e., the final target of research in this field.

Activated Carbon Nanofibers Derived from Thermally Rearranged Polyimides for Binder‐Free Supercapacitors

Supercapacitors (SCs) based on carbon nanofibers (CNFS) are being paid much attention due to their fast charge–discharge rate, high power density, and excellent cyclic stability. Herein, a kind of preferred hydroxyl‐containing poly(amic acid) solution is first synthesized by using 2,2‐bis(3‐amino‐4‐hydroxyphenyl)hexafluoropropane and pyromellitic dianhydride as monomers, and electrospun to prepare nanofiber membranes. Then, thermal imidization, thermally rearranged treatment, and carbonization are employed to successfully fabricate the corresponding hydroxyl‐containing polyimide (HPI)‐CNFs. Next, the activated CNFS are obtained through a simple activation treatment with KOH. After optimizing the concentration of KOH solution, the self‐standing and binder‐free CNF electrode A–HPI–CNFs–1/3 exhibits a maximum specific surface area of 2058 m2 g−1 and pore volume of 1.04 cm3 g−1, leading to a high specific capacitance of 387.7 F g−1 at 0.5 A g−1 and rate capability of 70% at 10 A g−1. In addition, the assembled symmetrical SC device shows outstanding cycle stability performance after 50000 runs of charge–discharge with a specific capacitance retention of 99.93% at 1 A g−1. Finally, the SC demonstrates a specific power of 12.7 Wh kg−1 at a specific energy of 250.0 W kg−1, suggesting potential application prospects in the field of SCs.

Si protected by metal-organic segments as anodes in Si-air batteries

Silicon-air batteries have attracted attention because of their high theoretical energy densities. However, the practical application of Si-air batteries is limited by the corrosion of silicon anodes. In this work, metal-organic segments (MOSs) coating was used for the first time to protect anodes in silicon-air batteries and the effects of MOS coating on the electrochemical performance of silicon-air batteries have been systematically investigated. The surface morphology of Si@MOS composites can be well-controlled by changing solution concentrations. The potentiodynamic polarization curves and the theoretical calculation prove that the corrosion rate of the silicon anodes can be effectively inhibited by the MOS coating. The critical KOH solution concentration can be reduced from 1.9 M for bare silicon to 1.3 M for Si@MOS composite anode. The Si@MOS composite anode also exhibits a longer discharge time of about 430 h at 0.9 V with a specific capacity 114 mAh g−1, which is much higher than that of bare Si (250 h with a specific capacity of 71 mAh g−1). This work not only demonstrates a surface modification method to protect the Si anode, but also provides a novel idea to improve the performance of Si-air batteries.

Effect of super-absorbent polymer on swelling pressure of compacted bentonite infiltrated by alkaline solutions

The application of bentonite in geological disposal of radioactive waste is still under evaluation, especially concerning the decreased swelling pressure of pure bentonite exposed to alkaline groundwater. In this paper, in order to improve the chemical resistance of bentonite to alkaline solutions, super-absorbent polymer (SAP), a hydrophilic polymer with much higher swelling ability than that of bentonite, was dry-blended with Gaomiaozi (GMZ) bentonite and compacted into blocks of different dry densities. Swelling pressure of the bentonite-SAP composites infiltrated with deionized water, NaOH and KOH alkaline solutions were tested, accompanied with scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP) and X-ray diffractometer (XRD) tests conducted on the selected specimens. Results showed that, for the specimens hydrated by deionized water, the swelling pressure increased with increasing SAP content, dry density and concentration of NaOH solutions. With increasing concentration of KOH solutions, however, the swelling pressure decreased obviously and tended to undergo a slow long-term degradation. Results of SEM, MIP and XRD indicate that the SAP hydrogels swell extensively to clog the inter-aggregate pores and coat the aggregates (for high density specimens) or montmorillonite stacks (for low density specimens), while do not insert into the interlayer spaces. The swelling pressure was therefore mainly contributed by the crystalline swelling of montmorillonite and the osmotic swelling of SAP. The SAP chains could be associated with the montmorillonite crystallites, protecting them from chemical attack and thus improving the chemical resistance of bentonite to alkaline solutions.

Investigation of the Dependence of the Silicon Needle Shape on the KOH Solution Concentration during Anisotropic Wet Etching

Investigation of the Dependence of the Silicon Needle Shape on the KOH Solution Concentration during Anisotropic Wet Etching

Study on flue gas denitration method based on multistage high gravity technology

According to the mechanism of wet denitration, H2O2 solution and KOH solution are used as absorbents, and the two-stage countercurrent high-gravity rotating packed bed is used as the reaction equipment. The rotating speed, gas-liquid ratio, temperature, H2O2 solution concentration and KOH solution concentration are changed respectively to explore the impact of various factors on the denitration efficiency, and finally determine the best experimental conditions for flue gas denitration. The experimental results show that when the rotating speed reaches 900 rpm, the gas-liquid ratio is 12:1, and the temperature reaches 36 °C, using 0.20 mol/l of H2O2 solution and 0.10 mol/l of KOH solution as absorbents, the denitration efficiency can reach the best, and the best denitration efficiency is 95.71%.

An ecofriendly agar extraction strategy using KOH for boiling extraction and MgCl2 for alkali neutralization

In this study, a new strategy for extracting agar from Gracilaria was proposed to replace the traditional NaOH extraction, using low concentration of KOH solution and MgCl2 neutralization (KOH–MgCl2 method) under homogeneous conditions. The KOH–MgCl2 method was more convenient than the traditional NaOH method, with 84% less alkali consumption, 76.4% less water consumption, and 80% less wastewater. The physicochemical properties of the agar extracted by the KOH–MgCl2 method (KMA) at different alkali concentrations were compared with those of the agar extracted with the traditional NaOH extraction method (NA) under scale-up tests. The results showed that KMA3 had lower sulfate content and higher 3,6-anhydro-α-l-galactose content and molecular weight than NA, indicating that the KOH–MgCl2 method had better desulfurization and lower degradation effect. Thus, this new method has potential to replace the traditional NaOH extraction method.

Recovery and analysis of valuable materials from a discarded crystalline silicon solar module

Mechanical, thermal, and chemical treatments were employed on a discarded small-sized silicon solar module to recover valuable materials from it. Materials like glass, junction box, polymer back sheet, and aluminium frame were recovered without damage. Ethylene-vinyl acetate layer (EVA) was obtained through the treatment of the panel with toluene solution. Optimised solution of 2 M HCl was used for Pb and Sn stripping from connecting wires to recover Cu Strips. Pb was extracted as PbCl2 from the solution through precipitation in an ice bath. Sn was recovered as SnO2 and SnCl2 through electrolysis of the residual solution. Al from the back contact was recovered as Al(OH)3 through sequential treatment with KOH and H2SO4. The effect of the molar concentration of KOH solution on Al etching was also investigated, and it was found that the 2 M solution was optimal. An innovative and cost-effective approach was adopted for the recovery of silver. Ag extraction involved, the treatment of solar cell pieces with HNO3 acid followed by reduction of AgNO3 with the copper strips. As recovered Cu strips were reused for Ag recovery, it can be considered a cost-reducing step for the reported recycling process. At last, ARC coating was removed by employing an H3PO4 solution to get silicon wafer pieces. X-Ray Diffraction and Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS) were used for phase identification and purity of the recovered materials. An overall recovery rate of 92.4% is achieved. Environmental impact and revenue generation through the process is also discussed.

Effect of KOH concentration on the properties of ZnO nanoparticles

Of late, ZnO nanoparticles have been regarded as favourable material for designing highly sensitive and selective gas sensors owing to their striking and multifunctional features. A facile sol–gel process chemical technique was used in this study for the preparation of undoped ZnO nanoparticles. By deploying x-ray diffraction (XRD), transmission electron microscopy (TEM), UV–visible near infrared and photoluminescence spectroscopy (PL), we examined the optical attributes and structural characterisation of the undoped ZnO nanoparticles through a change in the concentration of the KOH solution. The typical peaks inspected in the XRD spectrum corroborate the wurtzite hexagonal arrangement in the undoped ZnO nanoparticles. Moreover, ZnO nanoparticles possess a non-agglomerated crystalline with spherical morphology, as acquired by TEM. In addition, the vibrational modes in FTIR spectra vary with the change of concentration of KOH solution in ZnO NPs. The Raman spectroscopic techniques were used to characterise the ZnO nanoparticles, which revealed their nanocrystalline nature.

Photocatalytic hydrogen production of Melon/Azodiphenylamine polymers

Hydrogen is one of the most attractive energy sources at present for its excellent properties, such as high energy density, clean and non-pollution energy. Photocatalytic hydrogen evolution is one of the ideal strategies to obtain hydrogen energy. This work aimed to improve the visible-light absorption ability of the structure similar to g-C3N4 by anchoring azo groups into the structure. By this, the photocatalytic hydrogen production rate of the resulting product was improved apparently. We use melamine as starting material to prepare Melon, which was further reacted with KOH, PCl5 and 4, 4-Diaminoazobenzene to get the target Melon/4, 4-Diaminoazobenzene polymer. The condition influencing on the reaction was investigated, such as reaction temperature, the ratio of reactants and concentration of KOH solution. The structure of the as-synthesized polymer was determined IR, XRD, SEM, TGA and EIS. At the same time, its photocatalytic property was investigated.

Studi Konsentrasi Larutan KOH dan Arah Orientasi Serat Rami terhadap Kekuatan Impak Komposit dengan Matrik Polyester

The development of increasingly advanced technology, especially in the health sector, can lead to an increase in the need for composite materials used. This study aims to describe the results of the concentration of KOH solution and the orientation of the ramie fiber on the impact strength of composites with a polyester matrix. This research is an experimental study with the manipulation variables are the concentration of the KOH solution and the orientation of the fiber direction by determining the value of the impact strength as the dependent variable of ramie fiber as a control variable of this study. This study obtained the optimum impact test result of 0.0711 J/mm2 with 5% KOH solution concentration and located at 0o/45o/90o fiber direction orientation. While the results of the lowest impact test resulted in a value of 0.0101 J/mm2 without soaking the KOH solution and located at 90o/0o/90o fiber direction orientation.

The Sol-hydrothermal Synthesis of Potassium Bismuth Titanate Nanoparticles

Aims: To propose a method of KBT synthesis at a lower temperature to solve the volatility of the components. Background: Lead-based perovskite materials have long been employed in electroceramic industries due to their excellent piezoelectric, ferroelectric, and dielectric properties. The high toxicity of lead, however, leads to the replacement of the use of lead-based perovskite in devices with more environmentally friendly materials. KBT powders are traditionally prepared by solid-state reaction through the calcinations of K2CO3, Bi2O3 and TiO2 at high temperature. The high-temperature calcination process leads to serious particle agglomeration, grain growth and small surface area, which decrease the activity of the KBT powder. Instability of the KBT ceramic according to the high volatility of its component ions at elevated temperatures was the main concern for the application feasibility. Objective: This work was aimed to present the simplified method called “sol-hydrothermal” for the synthesis of KBT nanoparticles. Microstructure and phase evolution of the nanoparticles were investigated in detail. Method: The sol-hydrothermal method was performed in potassium hydroxide (KOH) solution at 140-200°C for 2-24 h. Result: The result showed that increasing hydrothermal temperatures from 140°C to 200°C, the crystal structure was changed from pseudo-cubic to tetragonal. At 200°C, phase separation was observed. Suitable hydrothermal time was found to be between 6-12 h, above which phase separation was also observed. Increasing the KOH solution concentration from 10 to 12 or 15 and finally, 20 M gave rise to greater KBT peak intensity, suggesting a more complete crystallization process when the concentration was increased. Tetragonal KBT nanoparticles with c/a ratio of 1.0620 were obtained under the synthesis condition of 180°C for 12 h in 20 M KOH solution. Sinterability of the synthesized KBT nano-particles was further investigated by varying the sintering temperatures from 1000°C to 1080°C; the highest relative density of 97% was obtained in the sample sintered at 1050°C. However, at this sintering temperature and beyond, the sublimation of the K-containing component occurred as evident by the appearance of Bi2O3 and Bi4Ti3O12 phases. Conclusion: In summary, KBT nanoparticles have been successfully prepared by the simple solhydrothermal method in a basic solution at low temperatures. Synthesis temperature, time and KOH concentration were found to affect the powder characteristics greatly. Increasing synthesis temperature was found to affect the phase development while increasing synthesis time resulted in the development of crystallinity of the KBT powder obtained. Increasing KOH concentration from 10 M to 20 M gave rise to different particle growth and agglomeration degrees. The optimum synthesis conditions were at 180°C for 24 h in 10 M KOH solution. At this condition, KBT powder with a uniform particle size distribution and tetragonal structure could be obtained. The synthesis powder showed excellent sinterability. Sintering at only 1020°C for 2 h gave rise to fine grain ceramics with 95% relative density. However, as potassium was prone to sublime, increasing sintering temperature to 1050°C and beyond resulted in K-deficient phases. Sintering of the KBT should be done in K-saturating atmosphere to suppress this sublimation.

Preparation of porous diatomite ceramics by an alkali treatment near room temperature

Porous diatomite ceramics were prepared by alkali treatment of the raw powder without any sintering procedure. The alkali treatment was carried out by dissolution of the surface by KOH solution to form solid crosslinking among the powder particles near room temperature. The effect of the amount and concentration of KOH solution on the properties of the porous diatomite ceramics was investigated. Variation of the treatment factors was found to be effective for controlling properties such as porosity, strength and thermal conductivity. Mixing a larger amount of high-concentration KOH solution with the raw powder could promote dissolution and the formation of thicker necks between particles by solid crosslinking. The resultant porous diatomite ceramics showed comparable compressive strength and thermal conductivity to those of sintered materials. The proposed method is therefore a useful tool for the preparation of high-performance porous ceramics near room temperature.

Corn stalk-based activated carbon synthesized by a novel activation method for high-performance adsorption of hexavalent chromium in aqueous solutions

A simple activation method involving treatment with KOH solution was used to synthesize activated carbon (ACs) with micro-meso pores from the agricultural waste of corn stalks. The activation reagent, KOH solution, was easily separated for recycling by centrifugation from the pre-treated corn stalks, and the pollution in the carbonization process was greatly reduced. The morphology and structure of the ACs were characterized by SEM, TEM, N2 adsorption, XRD, FT-IR and Raman analysis. The prepared carbon was applied as an adsorbent for the removal of Cr(VI) in a batch adsorption process. The effect of the concentration of KOH solution on the structure, morphology and Cr(VI) adsorption performance of the synthesized ACs was investigated. The characterization results revealed that some functional groups in the corn stalks were removed by pretreatment with KOH solution and micro-meso porous structures were generated. The ACs showed high adsorption performance for Cr(VI), and the maximum adsorption ability of the ACs prepared by activation with 4% KOH solution reached 89.5 mg g−1 at an adsorbent dosage of 2.5 g·L−1 and pH value of 4.5.

Study of Dielectric and Adsorption Properties of Activated Carbon Prepared from Water Hyacinth using KOH as an Activating Agent

Activated carbon can be produced from the combustion of a materials containing carbon that has been activated using activator substances. In this paper, potassium hydroxide (KOH) was selected as an activating agent. The influence of KOH concentration was investigated to determine the dielectric and adsorption properties of activated carbon derived from water hyacinth. Drying water hyacinth was carbonize in the furnace at a temperature of 400°C followed by chemical activation with variation concentration of KOH solution that used are 25%, 30%, and 35% (w/v) respectively. The results show that the best activated carbon derived from water hyacinth was obtained using 35% (w/v) KOH solution as an activating agent with the dielectric constant is 4,04 while iodine number of 514,6 mg/g.

Evolution of chemo-mechanical effects during single grit diamond scratching of monocrystalline silicon in the presence of potassium hydroxide

Efficiency and workability of silicon wafers for various applications depend on theirs surface integrity and damage free structures. Productivity of mechanical processing on silicon wafers is always limited by occurrence of cracks and brittle mode material removal at high depth of cut. This study presents a method of using controlled concentration of KOH solution during diamond micro-scratching of silicon and investigates the chemo-mechanical effects of KOH solution with respect to cutting speed. To establish the chemo-mechanical theory of cutting, responses of physical and material properties of silicon in presence of KOH solution are captured and correlated with mechanical responses during micro-scratching. Zeta potential and nanohardness are greatly reduced in KOH environment. Ductile mode is found to be extended by using 10 wt% KOH. Crack/chipping length is observed to be first increasing with increase in cutting speed at low range (0.6–20 mm/min) and then decreasing on further increase in the cutting speed (20–200 mm/min). Stability in cutting force signature and behavior of material flow along the scratch length is also found to be improved by using KOH. Adhesive wear and abrasive wear are found to be the main forms of single grit wear, which is significantly reduced in the presence of KOH. The experimental results on different mechanical and physical phenomena in this study are of great importance for establishing the theoretical insight into material removal behavior and selection of machining parameters during micro-machining of silicon wafer.

Electrochemical properties of amorphous metal alloys of Al-(Gd, Y)-Ni system in alkaline solution

The study of the chemical activity of amorphous Al-Ni metal alloys with various additives determines the feasibility of their operation in various fields of technology. This is a pressing scientific and applied problem, therefore, there is a need for electrochemical study of oxide-hydroxide films on the surface of amorphous alloys with variable composition of alloying elements, such as yttrium and gadolinium in 0.5‑5.0 M KOH aqueous solutions. The self-determination of the electrode potential of the AMA electrodes, ie without external influences, in particular polarization, was investigated potentiometrically. It is found that the introduction of nickel and RE stabilizes the corrosion resistance of aluminum alloys in alkaline environments, and the nature of RE practically does not affect the stable value of the potential of AMA electrodes, the value of which ranges from ‑0.75 to ‑0.79 V. Potentodynamic conditions produced polarization curves, which were the basis for studying the features of electrochemical processes on the surfaces of the studied materials in different media. A tenfold polarization of the AMA ‑ electrode into the region of positive potentials was performed. The anode polarization time was 540 s. AMA‑electrodes were polarized in aqueous KOH solutions of different concentrations. Electrochemical transformation of AMA electrodes in media of different concentration of KOH solution from 0.5 to 5 M was investigated by voltammetric analysis at their polarization within the potentials from ‑1.7 to + 1.0V. It is shown that yttrium doping reduces the passivity of the alloy surface, especially in 5 M KOH, and the replacement of yttrium by gadolinium, the combined presence of yttrium and gadolinium stabilizes the corrosion properties within concentrations from 1.0 to 5.0 M, in particular, the corrosion potentials acquire stable values. and ten ‑0.75 ± 0.05 V. It is shown that Y doping reduces the passivity of the alloy surface, especially in 5 M KOH, and the replacement of Y with Gd, the combined presence of Y and Gd stabilizes the corrosion properties within concentrations from 1.0 to 5.0 M, in particular, the corrosion potentials become stable. Values within the range from -0.75 to -0.78 V. However, due to the tenfold polarization of the AMA electrodes within the potentials from -1.7 to + 1.0 V, the corrosion potentials of the Al 87 Ni 8 Y 5 and Al 87 Ni 8 Gd 5 AMAs in the cathodic side shift approximately 0.03 V. Keywords: amorphous metal alloys, corrosion resistance, rare earth metals, aluminium.

Surface of AISI 316 as Electrode Material for Water Electrolysis Under Potassium Hydroxide for Hybrid Car Application

This study is to evaluate the surface of AISI 316 as an electrode material for water electrolysis under various potassium hydroxide (KOH) electrolyte concentrations. In the experimental method, AIS316 electrode and KOH solution put into the water electrolysis system. The electrolysis system was combined with the hybrid car engine system that consumed a combination of hydrogen and gasoline as the fuel source. KOH solution concentration was varied from 0 to 0.53M, which was then used to evaluate the surface of AISI 316 electrode as well as hybrid car performances. The experimental results showed that electrolyte solution concentration is an important parameter to maintain high-efficiency hydrogen generation. The more KOH added it gave benefits for creating the more hydrogen gas. However, it brought problems in the electrode surface corrosion. The optimum condition to get more hydrogen gas but with less corrosion damage was obtained when performing the process with 0.40 M of KOH. Indeed, the result also found that the more hydrogen gas being produced has a direct correlation to the reduction of fuel consumption and exhaust gas emission (e.g., CO2, CO, and NOx).

Hierarchical K/LTL zeolite as solid base for aqueous phase hydrogenation of xylose to xylitol

Abstract Post-synthesis modification by alkali treatment was employed for the synthesis of hierarchical K/LTL zeolites with varying degree of mesoporosity. For the alkali treatment, the concentration of aqueous KOH solution was changed from 0.3 to 2.8 M keeping the quantity per gram of zeolite fixed. The influence of the alkali concentration on the chemical composition, powder XRD crystallinity, morphology, basicity, and the textural properties of resultant hierarchical zeolites was investigated. Variation in the concentration of KOH solution was found to control the degree of preferential desilication with the preserved structural fingerprint of K/LTL zeolite. As a result, the generation of mesoporosity was observed along with 1) the decrease in the Si/Al ratio and percentage relative crystallinity, and 2) an increase in BET surface area and mesopore volume. 27Al MAS-NMR results showed that all the aluminum atoms present in the tetrahedral coordination after alkali treatment, which provides an elegant approach for significantly increasing the basic sites in the hierarchical zeolites. As a heterogeneous catalyst, the hierarchical K/LTL zeolites demonstrated the improved performance in the hydrogenation of xylose to xylitol as compared to the parent K/LTL zeolite. The different process parameters were assessed in order to maximize the hydrogenation activity. Among all the hierarchical zeolites, the enhanced catalytic activity was shown by the hierarchical K/LTL prepared by using 1.5 M KOH solution when it is used along with the 3.5 wt% platinum loaded γ-Al2O3 catalyst. This optimum activity may be attributed to the higher surface area, accessible basic sites, nano-sized Pt on γ-Al2O3, and the development of substantial intracrystalline mesoporosity for the enhanced molecular diffusion of reactant to and from the hierarchical zeolite with better-preserved crystallinity.

K+ trapped kaolinite (Kaol/K+) as low cost and eco-friendly basic heterogeneous catalyst in the transesterification of commercial waste cooking oil into biodiesel

Raw kaolinite mineral was modified by alkaline potassium hydroxide solution at 373.15 K for 8 h and calcinated at about 573.15 K to produce a new low cost and eco-friendly heterogeneous catalyst for efficient transformation of commercial waste cooking oil into biofuels (biodiesel). The synthetic catalyst was defined as K+-trapped kaolinite (Kaol/K+) and characterized by XRD, TEM, SEM, BET, and FT-IR in addition to the investigation of other properties as ion exchange capacity and total basicity. Different operating parameters were involved for the transesterification system for waste cooking oil in the presences of Kaol/K+ as a basic catalyst. 343.15 K temperature, 14:1 methanol-to-oil molar ratio, 180 min conversion time, and 15 wt% catalyst loading were defined as the best conditions for maximum production of biodiesel from waste cooking oil with yield percentage of 94.76%. The basicity and catalytic activity of kaolinite/K+ enhanced greatly with increasing the concentration of KOH solution up to 30% and then decreased again with the studied higher concentrations (35% and 40%). The catalyst can be reused for five runs using distilled water, methanol and acetone as washing reagents with clear preferences for organic solvents. The properties of the produced biodiesel in this study match the requirements of ASTM D-6571 specification and EN 14214 specification as the international standards for biodiesel in the world.