Potassium Hydroxide Concentration Research Articles

Optimization of methyl ester synthesis using gas/liquid phase pulsed discharge plasma in a novel oscillatory slug flow reactor

In the present research, an innovative oscillatory slug flow reactor (OSFR) under the treatment of gas–liquid phase pulsed discharge plasma was developed for biodiesel production. The main goal was continuous production of high quality biodiesel at low temperature and pressure. Experimental tests were carried out under the influence of four main operating parameters including applied voltage, molar ratio, reactant flow rate, and catalyst concentration. The response surface method was employed to optimize experimental tests. The results showed that the proposed technology provided 94% production efficiency under the optimal conditions of voltage 19.4 kV, molar ratio 6.4, flow rate 2.7 ml/s, and catalyst 0.9 wt. %. According to the statistical analysis, increasing the applied voltage and reducing the flow rate have a strong effect on the Fatty Acid Methyl Ester yield, while the concentration of potassium hydroxide and methanol have less effect on the overall efficiency. In addition, the characteristics of the produced biodiesel were in accordance with ASTM D6751 standards. Surprisingly, the optimal energy consumption in this system was 95 kJ/l, which is more economically viable. In general, this study showed that the combined system of gas/liquid phase plasma in the OSFR reactor has a high synergistic potential for the transesterification reaction.

Anaerobic fermentation of poplar processing residue to produce methane by alkaline hydrogen peroxide (AHP) pretreatment

ABSTRACT The study evaluated the effects of alkaline hydrogen peroxide (AHP) pretreatment on poplar processing residue for methane production. The delignification of poplar processing residue was used as the basis for evaluation. The experiment considered the pretreatment time (0 h-24 h), the hydrogen peroxide (H2O2) concentration (0.5%-2.0%), and potassium hydroxide (KOH) concentration (1.0%-3.0%) at a temperature of 70°C. Subsequently, anaerobic fermentation experiments were conducted using the pretreated biomass with sludge as the inoculum under mesophilic temperature conditions (37 ± 1°C). The initial feedstock (poplar processing residue) contained 40.31 ± 0.06% cellulose, 31.17 ± 1.59% lignin, and 14.85 ± 0.38% hemicellulose. The AHP pretreatment caused changes in the lignocellulosic content of the feedstock, particularly affecting the lignin structure compared to cellulose and hemicellulose. At a pretreatment time of 18 hours, temperature of 70°C, and concentrations of 2.0% H2O2 and 1.0% KOH, the AHP pretreatment resulted in a higher methane production of 237.4 mL per gram. These findings demonstrate that AHP pretreatment is an effective strategy for enhancing methane production from poplar.

Experimental exploration of potassium compounds in the vicinity of a burning biomass pellet: From near-surface to downstream

The concentrations of gas-phase potassium hydroxide (KOH), potassium chloride (KCl) and atomic potassium (K(g)) were quantitatively measured from the near-surface to downstream area of burning pinewood pellets by a newly developed photofragmentation tunable diode laser absorption spectroscopy (PF-TDLAS) technique to reveal the original form of the released potassium. The novel arrangement of the PF-TDLAS system enabled a spatial resolution of ∼1 mm3, which made it possible to obtain temporal release profiles of K(g)/KOH/KCl at different heights above the burning pellet surface. Surface temperature and mass loss of the wood pellet as well as the gas temperature at measurement points were measured simultaneously. During the devolatilization stage, the release of all three potassium species was observed, with each of them accounting for ∼1/3; while in char oxidation stage, the release of KOH was dominant, but the release intensity was strongly influenced by the local oxygen content. The results from different measurement heights showed there was a notable difference in potassium release profiles of different potassium species over the near-surface area, where the detected potassium forms were the best representative of the originally released forms of potassium. For a period of time during the devolatilization stage, only K(g) was detected in the near-surface area, and the concentration was significantly lower than the downstream area where KOH and KCl coexisted. This suggested that a large amount of potassium might leave the pellet as organic-K, which cannot be detected by the PF-TDLAS method. During char oxidation stage, the total potassium concentration at the near-surface area was also lower than the downstream area, but it was due to the lack of oxygen at the measurement position. A potassium release mechanism during the devolatilization stage of biomass combustion was proposed based on the experimental measurements, and the results also indicated the importance of spatially resolved measurement.

A determination of the composition and structure of the polysaccharides fractions isolated from apple cell wall based on FT-IR and FT-Raman spectra supported by PCA analysis

Generally in plants, cell wall polysaccharides are the main determinants of tissue properties and contents of an essential part of dietary fiber, prebiotics, or cosmetic ingredients. Therefore, evaluation of the content and structure of polysaccharides is crucial to understanding and controlling their functionality. Vibrational spectroscopy has already proven to be very useful in studying wall-based compounds. Here, it was proposed to use the FT-IR and FT-Raman spectra combined with PCA analysis to discriminate and distinguish pectic and hemicellulosic fractions isolated from apple parenchyma as an example. Reference measurements have been done on commercially available polysaccharides in order to identify relevant fingerprint bands. The similarities of different polysaccharide fractions from apple: water, imidazole, dilute alkali-soluble polysaccharides (WSP, ISP, DASP, respectively), and polysaccharides soluble in three potassium hydroxide concentration (KOHs) to the reference polysaccharides were found. In the case of both types of spectroscopy, the region below 1800 cm−1 was used to differentiate the samples. The results showed that the WSP, ISP, and DASP fractions have band patterns similar to the pectic polysaccharides, but also contain bands characteristic of polysaccharides containing arabinan and galactan. While the KOH fractions showed the greatest similarities to the hemicellulose polysaccharides, especially the glucomannan and xyloglucan. The results showed that FT-IR and FT-Raman spectra supported by PCA can be useful for studying the structure of polysaccharide fractions directly isolated from plant cell wall material.

Application of response surface methodology for optimization of the test condition of oxygen evolution reaction over La0.8Ba0.2CoO3 perovskite-active carbon composite

The Experimental Design was applied to optimize the electrocatalytic activity of La0.8Ba0.2CoO3 perovskite oxide/Active Carbon composite material in the alkaline solution for the Oxygen Evolution Reaction. After the preparation of La0.8Ba0.2CoO3, and structural characterizations, the experimental design was utilized to determine the optimal amount of the composite material and testing conditions. The overpotential was defined as the response variable, and the mass ratio of perovskite/active carbon, Potassium hydroxide (KOH) concentration, and Poly(vinylidene fluoride) (PVDF) amount were considered effective parameters. The significance of model terms is demonstrated by P-values less than 0.0500. The proposed prediction model determined the optimal amounts of 0.665 mg of PVDF, a KOH concentration of 0.609 M, and A perovskite/Active Carbon mass ratio of 2.81 with 308.22 mV overpotential (2.27% greater than the actual overpotential). The stability test of the optimized electrode material over 24 h suggests that it could be a good candidate electrocatalyst for OER with reusability potential.

Optimization of potassium hydroxide combined urea pretreatment and enzymatic hydrolysis of wheat straw using response surface methodology for improving sugar production

To improve sugar yields from wheat straw (WS), response surface methodology (RSM) was adopted to optimize potassium hydroxide combined urea pretreatment and enzymatic hydrolysis of WS. Glucose and xylose yields from the pretreated WS were used as responses during the whole optimization. Potassium hydroxide concentration, time and temperature during pretreatment were found to have significant effects on sugar yields. Sugar yields could be enhanced while WS was pretreated using 45 g/L potassium hydroxide solution containing 15 g/L urea with solid to liquid ratio of 1:5 (g/mL) at 74.0 °C for 50 min. Cellulose recovery, hemicellulose recovery, and lignin removal after optimization were 98.1%, 72.6%, and 75.8%, respectively. In addition, enzyme loading, biomass loading, and reaction time during enzymatic hydrolysis also had significant effects on sugar yields. Maximal yields of glucose (610.25 mg/gds, miligram per gram dry substrate) and xylose (221.26 mg/gds) could be achieved while hydrolysis was carried out at 50 °C for 32.8 h with 141 g/L of biomass loading, 8.1 FPU/gds (filter paper activity unit per gram dry substrate) of enzyme loading and 0.4% (w/v) of polysorbate 80. The corresponding cellulose conversion and hemicellulose conversion were 97.2% and 90.4%, respectively.

The effect of varying levels of potassium hydroxide-treated false Yam seed meal on growth performance, haematology and serum biochemistry of male broiler chickens

This study was carried out to evaluate sequential treatment of false yam seeds as substitute for maize in broiler chicken diets on their growth, carcass, haematology and serum biochemistry. Ripped fruits of false yam plants growing in the wild were harvested by hand picking. The fruits were partially sun-dried to reduce their moisture content and facilitate cracking to obtain the false yam seeds (FYS). The fresh FYS were crushed with a stone to reduce size, increase surface area and facilitate processing. The freshly crushed false yam seeds were subjected to multiple-stage processing where seeds were first soaked in ordinary water (i.e., addition of fresh seeds in ordinary water at a ratio of 1:2, wt/vol) for 12 days with water being changed every 3 days. After the 12 days of soaking, the seed sample was washed with clean ordinary water. In the second stage of processing, soaked FYS was soaked in a solution of 1M concentration of potassium hydroxide at a ratio of 1:2 (wt/vol) for 24 hours, after which the sample was washed thoroughly with clean ordinary water. The last stage of processing involved blanching of potassium hydroxide-treated seeds, firstly by immersing the sample in hot water (900C) for 20 minutes and then transferring it into cold water (40C) for 40 minutes. The treated seed sample was then washed with clean water, sun-dried to approximately 12% moisture on a cement floor and ground into gritty flour using a hammer mill. The treated false yam seed meal was labeled as KOH_T FYSM. At 21 d of age, 128 birds were individually weighed and then randomly assigned to one of four dietary treatments in quadruplicate lots. Each replicate had 8 male broilers. The mean live-weight of birds in each replicate was 883 g (±0.05). The four treatments included the control without KOH_T FYSM; treatments 2, 3 and 4 contained 100, 300 and 500g/kg KOH_T FYSM respectively replacing maize (wt. /wt. basis) in a completely randomized design. The birds were fed various diets for 35 d. The growth response of male broiler chickens fed diets supplemented with varying levels of KOH_T FYSM revealed no significant (P<0.05) difference in all growth parameters measured. Carcass dress weight and carcass dressing showed no significant (P>0.05) difference at 500g/kg. However, the relative weight of organs revealed a significant (P<0.041) increase in the heart weight and a reduction in the weights of the liver and the spleen. Haematological parameters evaluated revealed a significant (P<0.05) decrease in the haemoglobin, mean corpuscular volume, mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration as KOH_T FYSM was increased in the diets. The economics of replacing maize with KOH_T FYSM in the diets of male broilers revealed that price per kg of feed reduces as the test material was increased in the diets. Inclusion of KOH_T FYSM up to 500g/kg in the diets of male broilers had no adverse effect on their growth performance. However, its inclusion influenced internal organ weights such as the liver, spleen and heart. Economics of feeding KOH_T to broilers did not increase cost of feeding, suggesting that, There is an economic value for using this product for broiler chickens as an alternative to maize during periods of scarcity and can be recommended for use by farmers where this plant is available.

Synthesis and characterization of pH-responsive deep eutectic solvent followed by HPLC for trace determination of bisphenol A in water samples.

A microextraction based on pH-responsive deep eutectic solvent combined with high-performance liquid chromatography was developed for the separation, preconcentration, and determination of bisphenol A in water samples. Five deep eutectic solvents were prepared using thymol (hydrogen bond acceptor) and 6-, 8-, 9-, 10-, and 12-carbon carboxylic acids (hydrogen bond donor), and were used as extraction solvent. Herein, by alkalinizing the environment, phase transition takes place, and by adding acid, phase separation and extraction of analytes occur simultaneously. Some important parameters on the extraction such as deep eutectic solvent type, molar ratio of deep eutectic solvent components, deep eutectic solvent volume, potassium hydroxide concentration, hydrochloric acid volume, extraction time, and salt addition were optimized. Under the optimum conditions, intra- and interday precisions of the method based on seven replicate measurements of 10μg L-1 of bisphenol A in water samples were 2.2% and 4.3%, respectively. The analytical performance of the method showed linearity over the concentration of 0.05-50μg L-1 with the detection limit of 0.02μg L-1 . The accuracy of the method was confirmed by spiking different concentrations of bisphenol A in real water samples and obtaining relative recoveries in the range of 92.5%-105.2%.

Statistical Optimization of Tween-80-Assisted Potassium Hydroxide Pretreatment and Enzymatic Hydrolysis for Enhancing Sugar Yields from Corn Cob

With the addition of Tween 80, potassium hydroxide pretreatment and enzymatic hydrolysis were statistically optimized to maximize sugar yields from corn cob (CC). The results indicated that the sugar yields from CC could be influenced significantly by the potassium hydroxide concentration, temperature and time during pretreatment. The optimized pretreatment conditions were as follows: potassium hydroxide, 46 g·L−1; Tween 80, 3.0 g·L−1; solid dose, 200 g·L−1; temperature, 78 °C; and time, 50 min. After optimization, the lignin reduction and recoveries of cellulose and hemicellulose were 89.7%, 97.8% and 68.0%, respectively. In addition, sugar production could also be influenced by the biomass loading, enzyme loading and reaction time. A maximal glucose production (518.48 mg·gds−1, milligrams per gram of dry substrate) and xylose production (351.14 mg·gds−1), 97.2% cellulose conversion and 82.9% hemicellulose conversion from CC could be obtained when the biomass loading was 195 g·L−1 and the enzyme loading was 8.9 FPU·gds−1 (filter paper activity units per gram of dry substrate) and when the Tween 80 concentration was 3.0 g·L−1 at 50 °C for 30.4 h during hydrolysis. This is the first systematic study of combined Tween 80 pretreatment of CC by potassium hydroxide and hydrolysis of CC by cellulase preparation to increase sugar production.

Enhancing alkaline water electrolysis through innovative approaches and parametric study

The objective of this study is to examine how different parameters impact the effectiveness of alkaline water electrolysis (AWE) in producing hydrogen. Multiple experimental innovative approaches have been examined, namely, mechanically induced electrolyte flow, induction heating of electrodes, and pulsating voltage power mode. In addition, multiple parameters that have been experimentally investigated, including concentration of potassium hydroxide (KOH) solution, input current density, electrode spacing, electrode thickness, cell temperature, electrode coating material, and electrode morphology. The results obtained from these tests show significant improvements in AWE performance and efficiency. A better understanding of the behavior of AWE and the factors that influence its performance has been presented through a detailed discussion of the experimental results. The results have shown that reducing the gap size between electrodes improves AWE efficiency, however this relation is not monotonic and after a critical gap size the performance starts deteriorating. Furthermore, the localized induction heating has shown an improvement in the overall efficiency by approximately 8 % accompanied by a marginal increase in the global system temperature of around 4.2 °C.

EFFECT OF POTASSIUM HYDROXIDE CONCENTRATION AS A CATALYST ON THE YIELD OF COCONUT OIL (Cocos nucifera) TRANSESTERIFICATION

Research has been carried out on the effect of potassium hydroxide catalyst concentration on the yield of coconut oil (Cocos nucifera) transesterification and continued to characterize the reaction results. The concentration of potassium hydroxide used was 1, 2, and 3% by weight of coconut oil with ethanol as the reactant. The data processing used was the one-way analysis of variation and its characterization from a physicochemical perspective, followed by the analysis of gas chromatography-mass spectroscopy (GCSM) and infrared spectrophotometry. Based on the data processing results, potassium hydroxide concentrations of 1, 2, and 3% did not affect the yield of the transesterification reaction of coconut oil, and the results were 74.5264%, 71.9330%, and 69.0420%. The characterization results show that the physicochemical properties of the reaction products, such as acid number, density, and viscosity, comply with the Indonesian National Standard (SNI) for biodiesel. The results of the GCMS analysis showed that nine peaks were dominated by ethyl laurate.

Human urine electrolysis for simultaneous green hydrogen and liquid fertilizer production for a circular economy: A proof of concept

This study explores a novel process for hydrogen production and urine concentration using water electrolysis, employing a hydrophobic membrane and hydrogel electrolyte. The process utilizes a hydrophobic membrane to provide pure water from human urine, while simultaneously producing hydrogen through electrolysis, and concentrating urine for liquid fertilizer production. A suitable hydrogel electrolyte was developed, with polyvinyl alcohol (PVA)-based hydrogels and varying potassium hydroxide (KOH) concentration, showing efficient ion conductivity. The PVA-KOH 30 wt % hydrogel incorporating melamine exhibited promising performance in cell testing, achieving a current density of 204.35 mA/cm2 at 2 V. Long-term electrolysis tests indicated sustained efficiency, although a decline in current density during 96 h was attributed to hydrophobic membrane fouling. Nonetheless, the hydrogel electrolyte demonstrated minimal fouling, successfully concentrating the urine about 5 times. This concentrated urine serves as liquid fertilizer, while the produced hydrogen acts as an energy source, and the oxygen can be recycled for use in a membrane bioreactor (MBR), establishing a sustainable energy cycle system.

Electrochemical Analysis of Anion Exchange Membrane Water Electrolyzers (AEMWE)

The increase in deployment of renewable electricity has made green hydrogen production an attractive solution for decarbonizing energy systems. The prominent technologies currently deployed are the proton exchange membrane water electrolyzers (PEMWE) and alkaline water electrolyzers (AWE). The PEMWE technology uses platinum group material (PGM) catalysts, coated onto fluorinated Nafion® polymer membranes and needs specially treated titanium bipolar plates, reaching current densities of greater than 2 A cm-2. The AWE technology, in contrast, uses cheaper materials with a porous diaphragm separator, but the operating current density reaches only <0.5 Acm-2. The anion exchange membrane water electrolyzers (AEMWE) combine the advantages of both the PEMWE and AWE by using hydroxide (OH-) conducting, functionalized styrene-based membranes with non-PGM electrocatalysts, reaching current densities of >1 Acm-2.In this study, a membrane electrode assembly (MEA) consisting of Sustainion® X37-50 Grade RT membranes and non-PGM hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalysts are fabricated and analyzed for performance. NiFe2O4 (Merk) was chosen as the OER electrocatalyst and spray-coated on the sintered 316L stainless steel fibre (dioxide materials). On the counter side, NiFeCo (USnano) as HER electrocatalyst was spray coated on the molded graphite layer 370 (MGL370- fuelcellstore) porous transport layer. A catalyst loading of 3 mg cm-2 is obtained for both HER and OER electrodes. The fabricated MEA of 1x1cm2 is firstly tested for performance in a inhouse setup, using current density-voltage scans (j-V) using Zahner Zennium X electrochemical workstation. Consequently, electrochemical impedance spectroscopy (EIS) is performed in pseudo-galvanostatic mode. The perturbation amplitude is adjusted such that a linear region of the j-V curve is probed. The fuel electrode and air electrode contributions to the overall MEA performance are distinguishable due to the twin reference electrode configuration. The half cell-MEA contributions are further analyzed by performing parallel impedance measurements between the i) Reference electrode – cathode, ii) Reference electrode - Anode and iii) full-cell operation at predetermined current-density biases. These type of investigation gives deeper insight to the fuel electrode and the air electrode processes. The quality of the EIS spectra is analyzed using Kramers Krönig residual tests.A sensitivity analysis on the MEA is performed by changing impedance-effecting parameters such as temperature, operating current density and potassium hydroxide (KOH) concentration. Further, post-test characterization of the electrode substrates is performed to identify affected parameters through XPS, Raman spectroscopy, SEM-EDX and XRD techniques. The parallel impedance measurements confirms the presence of anodic, cathodic and low-frequency diffusion processes in real time.

Production of artificial humic acid from corn straw acid hydrolysis residue with biogas slurry impregnation for fertilizer application

This study investigated hydrothermal humification of corn straw acid hydrolysis residue with biogas slurry impregnation, aiming at producing water-soluble artificial humic acid fertilizer for fertilizer application and soil remediation. Hydrothermal humification parameters, including potassium hydroxide concentration (1–3 mol/L), retention time (2–6 h), and temperature (140–180 °C), were investigated using water as the liquid phase. The selected hydrothermal humification condition was 1.5 mol/L potassium hydroxide at 180 °C for 4 h. Moreover, biogas slurry impregnation (0–30 days) was evaluated to improve humic acid yield without introducing additional chemicals or energy input. Biogas slurry as the liquid phase increased the humic acid production by 73.24% with 5 days of impregnation compared to the control due to the alkalinity. The humic acid concentration was sufficient for China's national standard of water-soluble humic acid fertilizers in such conditions. The organic components in biogas slurry were involved in artificial humification as a precursor, forming C–N bonds with humic acid. The product with fortified nitrogen-containing functional groups enhanced the nutrient slow-release characteristics and water retention capabilities. The pot experiment further confirmed that artificial humic acid prepared in this study not only promoted the growth of plants but also achieved soil remediation.

Influence of Concentration of Potassium Hydroxide in Electrolyte on Formation of Hydroxyapatite Coatings on Titanium

Influence of Concentration of Potassium Hydroxide in Electrolyte on Formation of Hydroxyapatite Coatings on Titanium

Effect of a keratin coupling agent on the mechanical properties of a bovine hair-thermoplastic starch composite

A coupling agent (CA) was obtained through chemical modification of bovine hair. For that purpose, hair waste was treated using two concentrations of potassium hydroxide (KOH), 0.15 and 0.25 N. Treated and untreated hair waste was characterized. Fourier-transform infrared (FTIR) spectra showed that alkali treatment caused the formation of thiols (773 cm−1) and sulfonate groups (1063 cm−1 and 1041 cm−1) as a consequence of disulfide bond breakage. Furthermore, the keratin structure was disorganized (1697 cm−1), and functional groups –NH2 (1574 cm−1) were exposed. The vibrational analysis confirmed S–S bond cleavage to form S–H groups. Thermogravimetric analysis indicated an important disorganization of the keratin molecule. Additionally, differential scanning calorimetry (DSC) analysis corroborated the protein denaturation due to decomposition of the α-helix. Scanning electron microscopy (SEM) showed a clear effect on hair surface integrity, which promotes its interaction with the polymer matrix. Water absorption assays showed that alkaline treatment produces higher absorption due to a greater presence of polar functional groups. With the aim of assessing the CA's ability to act as a compatibilizer in a composite material, it was mixed with thermoplastic cornstarch (TPS) as a polymeric matrix and untreated hair fiber (UHF) as a reinforcing agent. The composites were processed by extrusion and injection molding. Young's modulus, tensile strength, and elongation at break were evaluated, showing higher values for the first two when the percentage of CA was increased.

Dynamics of Gas Generation in Porous Electrode Alkaline Electrolysis Cells: An Investigation and Optimization Using Machine Learning

This paper presents a systematic and comprehensive mathematical model for alkaline water electrolyzer cells, which can be used for simulation and analysis. The model accounts for factors such as gas evolution reactions, dissolution of gases in the electrolyte, bubble formation, and charge transport. It is based on a numerical two-phase model using the Euler-Euler approach, which has been validated against experimental data for various current densities. The study compares the impact of varying potassium hydroxide (KOH) concentration, separator porosity, and electrolyte flow rates on two-phase flow and bubble coverage. Therefore, the electrolyte in the cell consists of a solution of potassium hydroxide in water. The formation of gas bubbles at the electrodes decreases the electrolyte’s ionic conductivity. Additionally, the presence of these bubbles on the electrode surfaces reduces the available surface area for electrochemical reactions, leading to an increase in the overpotential at a given current density. Furthermore, this paper demonstrates how a neural network and ensembled tree model can predict hydrogen production rates in an alkaline water electrolysis process. The trained neural network accurately predicted the hydrogen production rates, indicating the potential of using neural networks for optimization and control of alkaline water electrolysis processes. The model has an average R-squared value of 0.98, indicating a good fit to the data. A new method of describing bubble transfer, “bubble diffusion,” is introduced to improve performance and reduce costs. The model is solved using COMSOL Multi physics 6.0. The machine learning models in this study were built, trained, and tested using MATLAB software R2020a.

Performance Advances of Industrial-Design Rechargeable Zinc Alkaline Anodes via Low-Cost Additives

Cost and safety are emerging as paramount considerations for grid-scale energy storage and often limit battery technology from practical deployment. Zinc alkaline is under renewed interest due to opportunity for lowered cost and improved fire safety. Nominal industrial-design zinc alkaline electrodes need improvement on their ∼100 cycle life when cycled at significant zinc utilization. Here, we analyze a collection of 72 practical paste Zn alkaline electrodes at 15 or 30% utilization of zinc’s 820 mAh/g Zn, with and without additives, and compare the resulting performance, industrial cost, and material evolution. Additives comprising calcium hydroxide [Ca(OH)2], bismuth oxide (Bi2O3), cetyltrimethyl ammonium bromide (CTAB), and/or a synthetic layered silicate (Laponite) were chosen to reduce shape change, mitigate gassing, reduce zincate migration, and alter the ionic environment, respectively. The concentration of potassium hydroxide (KOH) was also varied (10, 20, and 37 wt % KOH). We find performance that surpasses the best values in the literature for practical, real-world, industrially relevant zinc alkaline electrodes: Ca(OH)2 with Bi2O3 increased cycle life to ∼1200 cycles in 20% KOH (150 Ah/mL anode volume); CTAB with Bi2O3 and Laponite in 10 wt % KOH achieved slightly higher than ∼1200 cycles (∼210 Ah/mL anode volume) and pure-ZnO electrodes in 10 wt % KOH cycled ∼1000 times at 15% Zn utilization (240 Ah/mL anode volume). XRD, SEM, and EDS characterization reveals an altered microstructure when the additives are used. The first direct observation of calcium zincate cycling is collected by in situ XRD. The characterization data suggest that the mechanism for increased cycle life is capture and localization of the soluble zincate that forms during discharge, thereby reducing zinc material dispersal and shape change and increasing cycle life. Another important feature is pore geometry. When Bi2O3 is added, the electrode microstructure switches from a “closed cell” pore geometry with large ZnO flakes locking up pores to a more “open cell” geometry when small amounts of Bi2O3 are present.

Microwave-assisted desulphurization of coal in alkaline medium and conditions optimization by response surface methodology

Abstract The coal is an imperative source of energy, which on combustion, it emits sulphur dioxide, which cause air pollution. In the present study, microwave mediated desulphurization of coal was investigated and input variables were optimized by response surface methodology (RSM). The proximate analysis and ultimate analysis report indicate the sample belongs to subbituminous having sulphur (6.96%), volatile matter (34.5%) and calorific value (5099 kcal/kg). Under microwave irradiation, up to 68% of sulphur was leached in alkaline medium. The particle size of coal, concentration of potassium hydroxide (KOH), microwave exposure time and power of microwave radiation were systematically optimized for maximum desulphurization of the coal. Under optimum conditions of the process variables, 63.06% desulphurization of coal was achieved. The optimum levels of process variables are as, particle size 500 µm, irradiation time 8.54 min, radiation power 720 W and concentration of KOH 15% (w/v). Findings revealed that the microwave-assisted desulphurization under alkaline condition furnished promising efficiency, which can be employed for the desulphurization of coal.

Effect of KOH concentration on corrosion behavior and surface morphology of stainless steel 316L for HHO generator application

Hydrogen production could be enhanced by increasing the potassium hydroxide (KOH) concentration, but higher KOH concentrations result in higher corrosion rates. Therefore, a deep investigation of the electrochemical behavior of stainless steel (SS 316L) in the KOH solution is needed. This study investigates the influence of KOH concentrations on the electrochemical behavior, surface morphology, structure, and sample phases of SS 316L. The investigations were conducted by some electrochemical techniques, UV-vis, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and X-ray diffraction (XRD). The corrosion rate was found to increase, and solution resistance to decrease with increasing KOH concentration. Samples tested in 5, 30, and 50 g l-1 of KOH showed corrosion rates of 0.457, 2.362, and 5.613 µm year-1, respectively. A wide passive region and the noblest pitting potential were noticed for the sample with 5 g l-1 of KOH. Moreover, Mott-Schottky plots and characteristic wavelengths of UV-Vis suggest the formation of iron and chromium oxides by the passivation of samples. The SEM analysis showed a dynamic change of surface morphology from the lowest to the highest concentration with the intergranular corrosion found at the grain boundaries area. In conclusion, concentrations &lt; 50 g l-1 KOH could be recommended since they would support the optimum remaining life of SS 316 L plates in HHO generators.