Statistical modeling and optimization of pretreatment of Bombax ceiba with KOH through Box–​Behnken design of response surface methodology

Bioethanol is considered the cleanest liquid fuel used as a substitute for depleting fossil fuels. Various technologies have been introduced to form bioethanol from lignocellulosic biomass. Seed pods of Bombax ceiba, which are produced and wasted in large amount annually, were used as a source of cellulose. In this study, response surface methodology was used to explore the effects of KOH concentrations, substrate loading, and residence time on cellulose exposure and liberation of reducing sugars (RS), total sugars (TS), and total phenolic compounds from seed pods of B. ceiba. Box–Behnken design with three variables and three levels showed maximum release of total phenolic compounds (394.04 mg/ml) and RS (50.06 mg/ml) corresponding to 3% KOH concentration, 15% substrate level with residence time of 8 h at 121°C, and maximum cellulose exposure (64%), and TS (206.65 mg/ml) liberation was observed at 5% KOH concentration and 10% substrate level at same temperature for same soaking time. While at room temperature maximum cellulose exposed (46%), TS (146.1480 mg/ml), total phenol (300.3901 mg/ml), and RS (9.0075 mg/ml) were observed at 3% KOH, 15% substrate concentration, and 8-h residence time. These results suggested that thermochemical pretreatment is more effective than chemical pretreatment alone. The second-order polynomial equation using analysis of variance was employed for analyzing the results.     

KOH碱化处理对Fe3N纳米颗粒电催化制氢性能影响

采用KOH溶液在通电条件下对Fe₃N纳米颗粒表面改性的方法, 探究了碱化处理对Fe₃N纳米颗粒电催化性能的影响。采用XRD、TEM、EDX、XPS、拉曼光谱和傅立叶变换红外光谱对碱化前后的Fe₃N样品进行形貌和成分的表征, 采用时间电流曲线、LSV曲线、Tafel斜率、交流阻抗法和CV曲线对碱化前后的Fe₃N样品进行电催化制氢(HER)性能的分析。结果表明, 用KOH处理的Fe₃N样品, 平均晶粒尺寸由(80±10) nm缩小为(70±10) nm, 形状由破碎的链状结构变为椭圆形结构, 物相由ε-Fe₃N相部分转变为α-Fe₂O₃相; 尺寸、形貌和成分的改变, 使得碱化后的样品有更多的电催化活性位点暴露。由电流密度为10 mA/cm²的过电位0.429 V降为0.204 V, Tafel斜率由103 mV/dec降为95 mV/dec。过电势降低, 交流阻抗变小, 电化学活性面积增大, 表明KOH碱化处理后的样品电催化制氢的能力得到大大提高。     

Preparation of activated carbon dots from sugarcane bagasse for naphthalene removal from aqueous solutions

ABSTRACT

The synthesis of cheap and environmental friendly adsorbent from residual sugarcane bagasse was done for the removal of naphthalene from aqueous solution. The activated carbon dot was obtained by KOH chemical activation of carbon dots. The characteristics of carbon dots and activated carbon dots were determined using field emission scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and thermogravimetric analysis. A series of experiments were conducted in a batch system to assess the effect of the system variables, i.e., initial pH, initial naphthalene concentration, adsorbent dosage, and contact time. The kinetic data showed better fit to the pseudo-second-order model. The equilibrium data were better fitted to Freundlich and Temkin isotherms.     

Corrosion of stainless steel grades in molten NaOH/KOH eutectic at 250 °C: AISI304 austenitic and 2205 duplex

The present paper focuses on the corrosion of an austenitic (AISI304) and a duplex (2205) stainless steel grade in molten KOH/NaOH 50 w/o eutectic at 250 °C. Experimental activities have been performed consisting in electrochemical measurements (linear sweep voltammetry and electrochemical impedance spectrometry) complemented by metallographic (in‐plane and cross‐sectional SEM micrography), structural (X‐ray diffractometry) and compositional (EDX line‐profiles) characterisation of the materials attacked under electrochemically controlled conditions. Electrochemical measurements have shown that AISI304 exhibits a passivating behaviour, characterised by two passivation peaks and a transpassive threshold, while duplex, does not yield a clear indication of passivation. AISI304 was found to fail by intergranular corrosion and to be covered in both passive and transpassive conditions, by an incoherent scale, containing electrolyte species. Duplex samples, instead tends to fail by homogeneous attack and exhibit a range of scale structures, depending on the applied potential.     

Statistical Optimization of the Biodiesel Production Process Using a Magnetic Core‐Mesoporous Shell KOH/Fe3O4@γ‐Al2O3 Nanocatalyst

A magnetic core‐mesoporous shell KOH/Fe₃O₄@γ‐Al₂O₃ nanocatalyst was synthesized using the Fe₃O₄@γ‐Al₂O₃ core‐shell structure as support and KOH as active component. The prepared samples were characterized by X‐ray diffraction (XRD), field‐emission scanning electron microscopy (FE‐SEM), energy‐dispersive X‐ray spectroscopy (EDS), Fourier transform infrared (FTIR), Brunauer‐Emmett‐Teller (BET), and vibrating sample magnetometry (VSM) techniques. Transesterification of canola oil to methyl esters (biodiesel) in the presence of the magnetic core‐mesoporous shell KOH/Fe₃O₄@γ‐Al₂O₃ nanocatalyst was investigated. Response surface methodology (RSM) based on the Box‐Behnken design (BBD) was employed to optimize the influence of important operating variables on the yield of biodiesel. A biodiesel yield of 97.4 % was achieved under optimum reaction conditions. There was an excellent agreement between experimental and predicted results.     

A comparative study of micropipe decoration and counting in conductive and semi-insulating silicon carbide wafers

Micropipes are considered to be one of the most serious defects in silicon carbide (SiC) wafers affecting device yield. Developing a method to count and map micropipes accurately has been a challenging task. In this study, the different etching behavior of conductive and semi-insulating wafers in molten potassium oxide (KOH) is compared. Micropipes and closed-core screw dislocations exhibit different morphology after etching and can be easily distinguished with a polishing process. Based on a new sample preparation procedure and a digital imaging technique, a novel method of efficiently and reliably mapping and counting micropipes in both conductive and semi-insulating SiC wafers is developed.     

Ethanolysis of Refined Soybean Oil Assisted by Sodium and Potassium Hydroxides

The ethanolysis of refined soybean oil was investigated through a 2³ experimental design that was carried out under the following levels: ethanol:oil molar ratios (MR) of 6:1 and 12:1, NaOH concentrations of 0.3 and 1.0 wt% in relation to the oil mass, and reaction temperatures of 30 and 70 °C. The ethanol:oil MR and the alkali concentration had an almost equivalent influence on the reaction yield, whereas the influence of increased reaction temperatures was very limited and higher catalyst concentrations led to greater yield losses due to the formation of soap. Ethyl ester yields of 97.2% were obtained at 70 °C, MR of 12:1 and 0.3 wt% NaOH. Replacement of 0.3 wt% NaOH by 1.0 wt% KOH under the same reaction conditions led to lower ester yields. Likewise the former, KOH provided the maximum ester yield (95.6%) at the highest molar ratio (12:1), with the reaction temperature having little influence on the catalyst performance. Ester yields beyond 98% were only achieved when a second ethanolysis stage was included in the process. In this regard, the application of 2 wt% Magnesol^® after the first ethanolysis stage eliminated the need for water washing prior to the second ethanolysis stage and helped to generate a final product with less contaminating unreacted glycerides.     

Enhanced the electrochemical performance of mesh nano composite based catalyst for oxygen evolution reaction: Recent development

The energy crisis globally has severely damaged the economy of the globe which forces researchers and scientists to provide a new promising technology. Also, the rapid depletion of fossil fuels leads to an energy crisis & environmental concern, because of this, economic stress is created for the people of the world. To overcome these, water splitting is sustainable and renewable energy, but it requires active electrocatalysts. The nanostructure material morphology characterization was investigated by the, XRD, EDS, SEM, HRTEM, EELS chemical composition maps through & XPS which properly reveal the nanocomposite materials morphology strongly aggregates. The materials exhibit outstanding OER response as compared to Co₃O₄ & manganese sulfide due to the synergetic effect produced in the composite materials including fast charge transport from MoSO_X, active sites & high density of Co₃O₄, which accelerates the OER kinetics. Between the composites, Co₃O₄-MoSO_X with the greatest amount of Co₃O₄ (S4 0.7g) content owns the lower overpotential to produce OER kinetics & having a 60 mV dec^?1 and Tafel slope of as compared to other material. Further, for the exchange of current density of 2.97 × 10^?3A/cm² & it is extremely durable for 45 h. The EIS ensure the fast charge transport for the extra addition of pristine S4 (0.7g) in the composite, which potentially enhanced the production of the OER kinetics activity. In this regard transition metal oxide especially, Co₃O₄ is promising material, but it requires certain strategies to improve its catalytic kinetics activity & stability for the full water splitting. Keeping these challenges, the proposed study is of great concern to economical and societal needs, which can lead to a boost in the electrochemical applications in particular oxygen evolution reaction (OER). Therefore, rapid efforts must be made to realize the nonprecious catalysts for water splitting and equality compete with the world in the hydrogen/electron economy.     

Electrochemical enhanced oxidative decomposition of chromite ore in highly concentrated KOH solution

A novel method which introduces an electrochemical field to enhance the oxidative decomposition of chromite in a KOH sub-molten salt medium was proposed and proven to be feasible and efficient. Under optimal reaction conditions (slot current density 750 A/m², alkali concentration 60 wt.%, reaction temperature 150 °C, alkali-to-ore mass ratio 6:1, and particle size <200 mesh), the extraction rate of chromium reached 99%, after reacting for 480 min. In comparison with the current liquid-phase oxidation technologies, the reaction temperature in the new approach is 150–250 °C lower, and the alkali concentration of the reaction medium is lower by more than 20%, showing substantial advantages in terms of energy efficiency, equipment corrosion alleviation and prospects for industrial application. The reaction kinetics study shows that the extraction process under optimal reaction conditions is jointly governed by surface chemical reaction and solid product layer diffusion with the apparent activation energy calculated to be 17.56 kJ/mol.     

Effect of Lard Quality on Chemical Interesterification Catalyzed by KOH/Glycerol

The effects of water content, acid value, and peroxide value on interesterification catalyzed by potassium glycerolate (in situ KOH/glycerol) were investigated using lard as a model fat. SEM analysis of KOH/glycerol powder showed that numerous 0.5‐ to 5‐μm porous structures were formed and may play an important role in the interesterification reaction. Water content (up to 10 %, oil weight) and peroxide value (4.29 and 7.11 mmol/kg) significantly extended the induction period of interesterification but complete randomization was still achievable. However, when the acid value reached 5.13 mg KOH/g, complete deactivation of the catalyst was observed at 1 % catalyst content (by oil weight). The sn‐2 fatty acid composition of fully randomized lard was similar to that of non‐randomized lard. Interesterification resulted in substantial rearrangement of the triacylglycerol species and alteration of thermal behaviors. The interesterified lard exhibited a predominant β′ polymorph, as opposed to the dominating β‐form crystals found in the original lard.