Optimal Acid Research Articles

Higher BTEX Aromatic Yield from Ethanol over Desilicated H,Zn-[Al]ZSM-5 Catalysts

The amount of BTEX aromatics from the conversion of ethanol (ETA) is increased by combining ZSM-5 catalysts of optimum acidity with desilication and zinc ion exchange. The latter modifies the...

The Influence of Trihaloacetic Acids on the Hydrogen Sorption Properties of Palladium Limited Volume Electrode in Aprotic Ionic Liquid: Towards Ionic Liquid-Based Electrolytes for Protonic Systems

Ever-rising energy demand will result in increased need for efficient energy storage. Over the past few decades, nickel-metal hydride (Ni-MH) batteries are becoming increasingly popular due to a good cycle life and as they are more environmentally friendly and safer than other rechargeable battery systems. However, the electrode material corrosion caused by water-induced side reactions occurring in aqueous electrolytes is a common problem in such type of batteries. To overcome this disadvantage, many strategies have been exploited. Nowadays, efforts are being made to develop non-aqueous electrolytes suitable for Ni-MH batteries. In recent years, ionic liquids (ILs) have been suggested for electrolyte applications as an alternative option due to their unique properties important for battery technology [1]. However, the significant drawback of ILs is their relatively high viscosity, and thus low conductivity. The increase in conductivity can be obtained by addition of organic solvent to IL and recently, mixtures of organic acids and ILs are of interest to the battery technology. Therefore, the focus of this study was to check the applicability of ILs and their mixtures with haloacetic acids as non-aqueous electrolytes through the investigation of hydrogen sorption in palladium limited volume electrode (Pd-LVE). Pd-LVE is a very good model system to carry out the preliminary study of hydrogen electrosorption in ionic liquids in view of the further research with the use of multicomponent hydrogen absorbing alloys [2].The electrochemical experiments were conducted in 1-ethyl-3-methylimidazolium methanesulfonate ([EMIM][MS]) under inert gas (Ar) using three-electrode system. Pd-LVE (ca. 0.5 μm thick) was a working electrode, Ag wire was a quasi-reference electrode, and Pt spiral was an auxiliary electrode. Pd-LVE were obtained electrochemically from the PdCl2 aqueous solution. To perform the electrochemical measurements cyclic voltammetry (CV), chronoamperometry (CA) and chronopotentiometry (CP) techniques were used.Physicochemical properties of IL-based electrolytes, i.e. dynamic viscosity, density, ionic conductivity, and water content were determined as they have crucial influence on electrochemical measurements results. The Pd-LVE was used as an indicative electrode to study the optimum concentration of acetic acid and its halogen derivatives allowing to obtain maximum hydrogen capacity. The capacity was expressed as hydrogen to palladium atomic ratio. The amount of hydrogen was determined based on hydrogen oxidation charge obtained by integration of oxidation peak in the CV curve, while Pd amount was calculated based on the Farraday’s law from the deposition charge. CV curves of Pd-LVE registered in selected binary mixtures of [EMIM][MS] with acetic acid and its halogen derivatives are presented in Fig. 1. As one can notice, an increase in hydrogen oxidation and reduction signals intensity is observed with increasing concentration of organic acid. The optimum acid concentration equals to 2 M in the case of mixtures of [EMIM][MS] with acetic acid, while for the mixtures of [EMIM][MS] with trifluoroacetic acid it is 0.5 M as trifluoroacetic acid is a stronger acid than acetic acid. Surprising were the results obtained for mixtures of [EMIM][MS] with trichloro- and tribromoacetic acid. In the case of trichloroacetic acid increasing acid concentration did not cause increased hydrogen capacity. In the case of tribromoacetic acid there is no visible peaks of hydrogen oxidation after gradual addition of acid to [EMIM][MS]. Moreover, dissolution of palladium were observed.To explain unusual behavior of samples and electrochemical results, 1H NMR was used as a supporting technique. In the 1H NMR spectra additional peaks compared to spectrum of pure [EMIM][MS] are visible at 7.336 and 6.682 ppm for trichloro- and tribromoacetic acid, respectively. They are assigned to chloroform and bromoform formed as a result of haloacetic acid decarboxylation after mixing with [EMIM][MS]. To explain this phenomenon, computational studies were performed. The observed energy barriers correlate with the experimental observations of no decarboxylation in the [EMIM]+[FAC]−[MS-H] system, and the more efficient decarboxylation observed for Br than for Cl derivative.Examined binary mixtures can be effectively used as electrolytes in the hydrogen sorption process. The maximum hydrogen capacity obtained for [EMIM][MS] mixtures with acetic and trifluoroacetic acid are similar (ca. 0.74) and comparable with those measured in aqueous solutions. The results of this research involving other haloacetic acids show that there is a need of synthesis of tailored ionic liquids suitable for the more efficient performance of the electrode material. Funding: This work was funded by National Science Centre (NCN, Poland), grant number 2021/41/B/ST5/04047.[1] M. Pająk et al. Energy Convers. Manag.: X 20 (2023) 100500[2] K. Hubkowska et al. J. Solid State Electrochem. 28 (2024) 1159–1169 Figure 1

An Effective Synthesis of Phosphated Silica (PO<sub>4</sub>/SiO<sub>2</sub>) Catalyst and its Performance for Converting Ethanol into Diethyl Ether (DEE)

Research on phosphated silica (PO4/SiO2) as a heterogeneous acid catalyst in the dehydration reaction of ethanol into diethyl ether has been carried out. The PO4/SiO2 was prepared from TEOS by a wet impregnation method with various concentrations of H3PO4 (1, 2, 3, 4 M) and calcination temperatures (400, 500, and 600 °C) to obtain it with an optimum acidity. Afterward, the catalysts were characterized by FTIR, XRD, SEM-EDX, SAA, and TG-DTA. Ethanol dehydration was run using a fixed-batch reactor with a flow of N2 gas, and GC determined the selectivity of diethyl ether. The PS-4-400 catalyst had the highest activity and selectivity in the ethanol dehydration to diethyl ether at a temperature of 225 °C, with a conversion of 58.00% and a DEE selectivity of 3.71%.

Enhancing the selectivity of light olefins through synergistic VOx/ZSM-5 composite in the oxidative cracking of hexane

Oxidative-aided cracking of n-hexane is studied in a gas-phase oxygen-free environment over VOx/ZSM-5. The catalysts were prepared by impregnation of VOx on ZSM-5. Characterization of the prepared samples using XRD, SEM, and BET showed smooth, fine, highly crystalline, and highly dispersed VOx on ZSM-5. Raman spectroscopy revealed the presence of isolated moieties on the 1.5 and 2.5 % vanadia loading while a small number of polyvanadate species are detected on the 5 % VOx sample. TPR confirmed the ZSM-5 support contains highly reducible vanadia species. The amount of VOx loading also affected the activity and product distribution. The olefin and COx selectivities are affected by reaction time/temperature and amount/availability of lattice oxygen. VOx/ZSM-5(1.5) showed 99.9 % n-hexane conversion and 91.39 olefin selectivity at 575 °C and 25 s time-on-stream. This superior performance is attributed to the intermittent release of oxygen, optimum acidity, microporosity, and mesoporosity.

Recycling Valuable Phenol from Polycarbonate Plastic Waste Via Direct Depolymerization and Csp2-Csp3 Bond Cleavage Under Mild Conditions.

Upcycling plastic waste into commodity chemicals is recognized as an environmentally benign solution and beneficial for the sustained growth of humanity. Nevertheless, transition metal-free catalysts and energy-efficient conditions pose significant challenges due to the robust mechanical properties of plastics. Here, a strategy for selective production of phenol by upcycling polycarbonate waste via direct depolymerization and Csp2-Csp3 bond cleavage in an aqueous medium under mild conditions is reported. The commercial zeolites efficiently catalyze the depolymerization, Csp2-Csp3 bond hydrolysis, and direct Csp2-Csp3 bond scission at Cα of PC. Among all evaluated zeolites, HY (Si/Al=15) showed excellent catalytic performance, attributed to the ~75 % yield of phenol and ~15 % of acetone. The approach also employs different municipal waste PC for upcycling. Studies reveal that HY (15) exhibits high catalytic efficiency and phenol yield due to its optimum acid sites and textual properties. A scale-up experiment demonstrated that 3.1 g of phenol was produced from 5.0 g of PC, and the mass balance was 90 %. A combination of control experiments, NMR analysis, and DFT studies proposed the reaction pathway. Our findings present a sustainable avenue for upcycling PC waste and offer a new way to produce phenol, contributing to the advancement of a circular economy.

Impact of rock heterogeneity on reactive flow during acid stimulation process

Acid stimulation within carbonate rocks represents a crucial aspect of reactive flow applications in subsurface porous media and has been widely used in carbonate reservoir development attributed to its rapid effectiveness and cost-efficiency. This study is motivated to investigate further the impact of rock heterogeneity on the acid stimulation process. The two-scale continuum model is employed for capturing mass, momentum, and energy transfer during the acid stimulation process. The core-scale model is expanded to consider the specific composition of solid minerals, including reactive minerals such as calcite and dolomite and non-reactive ones like quartz and clay. A heterogeneity generator is developed by coupling with the open-source geostatistical program to produce different heterogeneous parameters using random seeds with varying spatial correlation lengths. Sensitive cases are performed to present an investigation into the influence of mineral composition and matrix heterogeneity on the acid stimulation process. Results show that the typical results of acid stimulation are closely tied to different heterogeneity conditions. The optimum conditions for acid stimulation are sensitive to the concentration of reactive components. The optimum acid injection rate declines as dolomite content increases, while the corresponding acidizing breakthrough volume reduces with higher calcite levels. The presence of mineral layers, especially in horizontal distributions, complicates acid fluid efficiency due to the competitive reaction between calcite and dolomite. Compared to the heterogeneous distribution of minerals, matrix heterogeneity plays a critical role in acid fluid consumption efficiency. Increasing heterogeneity leads to significant reductions in breakthrough volumes, largely governed by the correlation length.

Effects of Addition of Humic and Fulvic Acids on Soil Properties and Germination Percentage of Cucurbit Plants (Zucchini and Cucumber)

This research was conducted to study the effect of adding humic and fulvic acids to the irrigation water on soil properties and germination percentage of two cucurbit plants: zucchini and cucumber. The study was conducted in an open field in Sokhna District in the governorate of Zarqa (Jordan). The field soil was transported to calcareous sandy soil. In the beginning, the weeds and stones were removed, and the land was smoothed and plowed. Effort was made to control weeds and insects at all stages of plant growth. Then, an irrigation network was installed. The fulvic acid-humic acid (FA-HA) biostimulant mixture was incorporated with the irrigation water, and irrigation was practiced three days per week for four weeks. During this period, every irrigation round lasted for two to three hours. A mixture of humic acid (8.0%) and fulvic acid (8.0%) was added to the irrigation water. Three treatments were considered, corresponding to three acid mixture concentrations: 0.50 mL.L-1, 1.00 mL.L-1, and 1.50 mL.L-1. The acid mixtures were added continuously at all stages of plant growth until plant maturity and harvest. Four replicates of the experiment were made. The plant growth variables of interest were germination percentage, number of leaves, date of fruition, size of fruit, and overall mass of fruits. Meanwhile, the soil parameters of interest were soil pH and soil salinity (electric conductivity (EC)) before and after adding the FA-HA mixture. The study found that the 0.5 mL.L-1 acid mixture treatment led to the early growth of the zucchini plant seeds and that fruition took place 12 days after planting. In addition, the results showed an increase in plant germination under the 0.5 mL.L-1 acid mixture treatment in light of the increase in the number of male and female plant flowers, with fruiting taking place on time. In conclusion, the relationship between zucchini growth and yield with FA-HA mixture concentration is non-linear. It is also concluded that the optimum acid mixture concentration and application rate are crop-specific. Hence, for each crop, the most appropriate acid mixture concentration should be determined first before the broad-scale application of amendments to the soil to ensure the contribution of this environmentally friendly practice to sustainable agriculture.

Evaluation of the performance of acids for effective stimulation of a sandstone formation

Optimum acid selection based on reservoir condition is one of the key elements in achieving a successful treatment in sandstone matrix acidizing. This work will investigate the effectiveness of several type of acid in sand stone reservoir stimulation. PROSPER well modeling package was utilized for the model development. Pre- acid job analysis was carried out to establish the well performance before acidization. Acid stimulation was implemented with Hydrochloric (HCl), Formic, Acetic, Propionic and ChloroAcetic acids. Thereafter, post-job analysis was done to ascertain the improvement in well productivity index for each of the acids. Result shows that the reservoir will deliver 11296.5 STB/day of liquid into the wellbore for a production index of 3-STB/day-psi without acid stimulation and the well will produce 6726.05 STB/day of liquid. Results reveals a decrease in productivity index as the treatment acid was change from HCl acid to formic acid, acetic acid and propionic acid. A productivity index values of 3.07074STB/day-psi, 3.0375 STB/day-psi, 3.01038 STB/day-psi, 3.00791 STB/day-psi were obtained when the formation was acidized with HCl acid, formic acid, acetic acid and propionic acid. A percentage increase of 15.1973%, 7.5731%, 1.95684% and 1.47001% in permeability was observed as the formation was treated with HCl acid, formic acid, Acetic acid and Propionic acid. Results reveals that HCl acid resulted in highest permeability increase. It was therefore concluded that the formation should be acidized with HCl acid since it gave the highest productivity index, percentage increase in permeability, porosity and the highest improvement in skin factor.

Waste to wealth: Facile activation of red mud waste and insights into industrial reactive dye removal from wastewater

Reactive dyes, widely applied in the textile industry for their vibrant colors, excellent fastness, and ease of application. Their presence poses multifaceted threats to aquatic ecosystems and health risks, including skin irritation, allergic reactions, respiratory problems, and increased cancer risk. In response to these challenges, this study explores the potential of acid-activated red mud, an industrial solid waste by-product from the aluminum industry, as an economical adsorbent for the removal of commercial reactive dyes from industrial wastewater. The robustness of the employed Box-Behnken design is evidenced by the high determination coefficient (0.997) and correlation coefficient (0.994) values. The optimum acid activation condition was determined to be 385 K activation temperature, 91 min activation time, and 2.5 N HCl acid concentration, resulting in a 99.24 ± 0.04 % removal efficiency for reactive dyes. Analysis of X-ray Diffraction and X-ray Fluorescence data revealed that the activation process significantly increased the composition of Al and Fe compounds. This enhancement was achieved by eliminating compounds that block active sites and improves the overall surface area from 37.35 m2/g to 173.81 m2/g. Detailed morphological analysis, conducted through high-resolution transmission electron microscopy and scanning electron microscopy, reveals profound transformation in the surface structure. The study primarily focuses on removing four commercial reactive dyes: Reactive Blue 2 (RBL-2), Reactive Black 5 (RBK-5), Reactive Red 24 (RR-24), and Reactive Yellow 15 (RY-15). These dyes demonstrate maximum adsorption capacities of 118.24 mg/g, 121.02 mg/g, 129.19 mg/g, and 142.64 mg/g, respectively. In order to comprehend the interactions between dye molecules and the adsorbent, a first principle based model was employed to simulate the adsorption kinetics.

Interaction of alkaline and acid treatment on the removal of proteinaceous mineral-enriched dairy fouling from UHT treatment

CIP processes in milk processing plants are frequently oversized to reliably meet hygienic and safety requirements. Cleaning follows a fixed protocol, but the exact mechanisms and intermediate products are often unknown. This study presents an experimental approach to elucidate the interaction between alkaline and acidic treatment with special regard to the impact of acid on proteinaceous deposits. The protein containing fouling layers become yellowish in colour by acidic treatment; this is attributed to the xantho-proteic reaction and no efficient removal is thereby achieved. In contrast, the removal is efficient if an efficient initial alkaline treatment step is performed. An efficient initial alkaline treatment step was identified as crucial for the further course of cleaning and a short alkaline treatment soaked the entire soil, which enabled an efficient subsequent acidic removal. Lower concentrations of HNO3 demonstrate more efficient cleaning than higher ones, suggesting an optimum acid concentration during CIP.

Characterization of Nanocellulose from Orange Peel Waste

Orange peel is a commercially available natural fiber with an increasing interest in using it as a raw material in a variety of applications due to its high cellulose concentration in the plant. This research aims to determine the preparation of nanocellulose from orange peel waste (OPW) by using chemical treatment of acid hydrolysis method. In order to provide the optimum conditions of nanocellulose of OPW which are possessed high crystallinity in their crystal structure by using acid hydrolysis method and the effects of various acid concentrations on the crystallinity index, crystallite size and morphology of cellulose nanocrystals were studied. However, based on the previous study, using OPW there is limited study has been reported on type of acid and optimum acid concentration as a parameter of using hydrolysis method. Therefore, in this study, the process of preparation OPW nanocellulose by using acid hydrolysis method with the best type of acid used of sulphuric acid (H2SO4) and hydrochloric acid (HCl), optimum acid concentration (30-40 wt%), constant hydrolysis time (120 min) and constant temperature (45 °C) is comprehensively studied. Based on the achieved outcomes, the H2SO4 emerges as the most favorable approach for acid hydrolysis technique, effectively yielding finely dispersed crystalline cellulose while mitigating undesirable aggregation effects. The optimal acid concentration of 30 wt%, coupled with a 120 minute hydrolysis duration and a temperature of 45 °C, yields the most favorable results in terms of both crystallinity index and crystallite size, reaching remarkable values of 87.69 % and 3.19 nm, respectively. The nanocellulose derived from OPW holds significant potential as an environmentally sustainable material, aligning harmoniously with prevailing global trends in design and development for enhanced sustainability.

Valorizing biomass waste glycerol to fuel additive at room temperature using a nanostructured WO3/Nb2O5 catalyst

We developed a nanostructured catalyst consisting of WO3 nanoparticles and Nb2O5 nanorods for efficient glycerol acetalization to produce a fuel additive (solketal) at room temperature. Particularly, the WO3/Nb2O5 nanocatalyst calcined at 400 °C (WO3/Nb2O5–4) contains W5+ species and optimum acid sites, which enhanced glycerol conversion (92.3%) with 95.6% of solketal selectivity at room temperature. The structure stability of the WO3/Nb2O5–4 catalyst during the reaction is showcased by hot-filtration study and XRD/XPS characterization. However, the inadequate regeneration of the Brønsted acid sites led to a gradual decrease in the recyclable activity of the WO3/Nb2O5–4 catalyst.

Determination of purines in prepackaged food using optimum acid hydrolysis followed by high performance liquid chromatography.

A high performance liquid chromatography was established to determine purine content of prepackaged food. Chromatographic separation was performed on Agilent5 TC-C18 column. Ammonium formate (10mmol/L, pH=3.385) and methanol (99:1) were used as mobile phase. Purine concentration and peak area showed good linear relationships in the range from 1 to 40mg/L (guanine, hypoxanthine, adenine) and xanthine exhibited a good linear relationship ranged from 0.1 to 4.0mg/L. Recoveries of four purines ranged from 93.03% to 107.42%. Purine content in prepackaged food was following: animal derived prepackaged food: 16.13-90.18mg/100g; beans and bean products: 66.36-157.11mg/100g; fruits and fruit products: 5.64-21.79mg/100g; instant rice and flour products: 5.68-30.83mg/100g; fungi, algae, fungi and algae products: 32.57-70.59mg/100g. This proposed method had good precision and accuracy with a wide linear range for detection of purine. Animal derived prepackaged food was purine-rich food, purine content of plant derived prepackaged food varied greatly.

Efficient removal behaviors and correlation rules of Na from Zhundong coal with low concentration organic acids

The effects on the removal of Na from Zhundong coal were investigated systemically using ten organic acids including seven aliphatic saturated acids and three aromatic acids as well as two inorganic acids of low concentration. The results show that the structure and concentration of acids, leaching temperature and time are the main factors influencing Na removal from coal. The removal rate of Na, if only deionized water (DI) is used for leaching, is 52.03% resulting from water-soluble inorganic Na. When the acid concentration is 0.01 mol/L, the removal rate of total Na can reach 88.67–99.18% for aliphatic saturated acids, 85.26–89.38% for aromatic acids and 99.28–99.35% for HCl and H2SO4, indicating that the most organic Na can be removed by ion exchange between H+ and Na+ except for water-soluble inorganic Na. The removal amount of both total Na and organic Na increases basically linear with the increase of inorganic or organic acids until nearly the highest removal amount for different acids. The theoretical removal amount of Na and the optimum acid addition can be quantitatively calculated based on the correlation rules between the Na removal and the different acids, for example, ytotal Na(mmol/g) = 0.39xacid(mmol/g) + 0.099 for acetic acid (AA) and ytotal Na(mmol/g) = 0.56xacid(mmol/g) + 0.097 for HCl. The removal differences for various organic acids are mainly due to the difference in acidity and the molecular structure of organic acids. The Na2O content in coal ash decreases greatly from 6.21% for raw coal and 2.77% for water leaching coal to 0.22–0.95% for low concentration organic acids treated coal and ca. 0.21% for low concentration HCl and H2SO4 treated coal.

PROTON EXCHANGE MEMBRANE FUEL CELL; EMPIRICAL REVIEW ON THE DEGREE OF SULPHONATION

Empirical review on the degree of sulphonation of polymeric materials for proton exchange membrane fuel cell (PEMFC) was carried out. Fuel cell generally applies the principle of electrochemistry in which chemical energy is converted directly into electrical energy. Amongst the league of fuel cells, the proton exchange membrane fuel cell is the most promising. However, the central component of PEMFC is the ionic polymer membrane that must be rendered conductive. This study showed that the measure of sulphonation is pivotal in achieving conductivity of the polymer for fuel cell application. The study revealed that for an optimum conductivity to be achieved, optimum degree of sulphonation (DS) is needed. The recognized factors that affect the optimum degree of sulphonation were the type of sulphonating agent (as chlorosulponic acid achieved 39.04% and 50.21% differential increment over both sulphuric acid and fuming sulphuric acid, respectively), sulphur content (while the lowest Sc of 1.76% achieved 9.13% DS, the highest Sc achieved 20.04% DS), optimum acid concentration (as DS of 20.04 % was achieved with 1.6 mmol/g as against 2.0 mmol/g of 16.76 %), nature of the polymer base material (as more –SO3H groups attached to aliphatic polymers than aromatic), optimum time and stirring speed, optimum temperature, and optimum weight of the base polymer. The study was able to unravel that the degree of sulphonation can be determined via elemental sulphur analysis either by analytical or titrimetric method. The study also showed that the degree of sulphonation can be predicted correctly using a predictive model.

Arylnaphthalene Lignans with Anti-SARS-CoV-2 and Antiproliferative Activities from the Underground Organs of Linum austriacum and Linum perenne.

Diphyllin (1) and justicidin B (2) are arylnaphthalene lignans with antiviral and antiproliferative effects. Compound 1 is also known as an effective inhibitor of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). To evaluate the in vitro antiviral and cytotoxic potency of both lignans in SARS-CoV-2 -infected cells and various cancer cell lines, respectively, 1 and 2 were isolated from the underground organs of Linum austriacum and Linum perenne. Two previously undescribed arylnaphthalene lignans, denominated linadiacin A and B (3 and 4), were also isolated and identified. In acidic media, 3 was converted by a two-step reaction into 2 via the intermediate 4. Optimum acid treatment conditions were determined to isolate lignans by one-step preparative high-performance liquid chromatography (HPLC). The results of the conversion, HPLC-tandem mass spectrometry, nuclear magnetic resonance spectroscopy, and molecular modeling studies allowed complete structure analysis. Compounds 1 and 2 were the most effective against SARS-CoV-2 with a 3-log reduction in the viral copy number at a 12.5 μM concentration. Ten human cancer cell lines showed sensitivity to at least one of the isolated lignans.

Selective extraction and separation of gallium(III) from indium(III) in chloride medium using di(2-ethylhexyl) (N, N′-di(2-ethylhexyl) amino methyl) phosphonate and stripping with water

An aminophosphonate extractant, di(2-ethylhexyl) (N, N′-di(2-ethylhexyl) amino methyl) phosphonate (abbreviated as L) was synthesized and applied for the extraction and separation of gallium and indium from chloride solution. The maximum separation factors SFGa/In reached 995, which is higher than those obtained with its analogues such as Cextrant 230 (SFGa/In = 471) and BEADP (SFGa/In = 201) at the optimum acidity conditions. The extracted complexes were determined to be HGaCl4L2 and InCl3L2. The extraction reactions of gallium and indium were both endothermic. The loading capacities of 30 vol% L for Ga and In were 32.9 g/L and 25.2 g/L, respectively. The loaded gallium and indium in organic phase can be effectively stripped by distilled water, H2SO4 and HNO3. A process was established for the separation and purification of gallium, by which the purity of Ga2O3 increases from 98.4% to 99.97% with a yield of 92.5%.

Neem-castor seed oil esterification modelling: Comparison of RSM and ANFIS

Even though the desirable fuel properties and enhanced engine characteristics of an IC engine have led to the adoption of hybrid second generational oily feedstock (HSGOF) over a mono-oily feedstock, the high FFA associated with the HSGOF remains a challenge. The Response Surface Methodology (RSM) and Adaptive-Network-based Fuzzy Inference System (ANFIS) were used to model the esterification of neem and seed crude oils (NCSO) with a high free fatty acid content (FFA). The RSM and ANFIS were used to model and optimize input: esterification variables such as NCSO ratio (20–40), catalyst dosage (1.0–2.0 wt%), retention time (1.5–2.5 h), and NCSO/methanol molar ratio (4.5–5.5) to achieve the lowest FFA for the NCSO esterification process and produce composite biodiesel. Optimum acid value (AV) of 2.1 mg KOH/g was attained at NCSO ratio of 20, catalyst dosage of 2 wt%, retention time of 2.0 h, and molar ratio of 4.5. A contrast of the developed models was accomplished by statistical norms such as coefficient of determination (R2), root mean square error (RMSE) with standard Error of Prediction (SEP). The R2 of 0.82522, RMSE of 0.68099, and SEP of 0.21729 for the RSM model (RM) related to the R2 of 0.9982, RMSE of 0.02434, and 0.01992 for the ANFIS model (AM). The AM seems more consistent than the RM in pre-treating and rendering high NCSO for composite biodiesel production. The key fuel properties of the neem-castor oil methyl ester (NCSOME) certified with those of biodiesel international standards.

Selection of a leaching system for the extraction of gold from the ore of the Byn’govskoye deposit

A theoretical substantiation of an environmentally friendly technology for extracting gold from mineral raw materials is presented. In terms of an alternative to conventional cyanide, the authors propose chlorine-bearing derivatives of organic isocyanuric acid (C3H3N3O3). In the studied process, this reagent combines the roles of a long-acting oxidant and complexing agent due to the resulting Cl– ion. For experimental purposes, the rotating disc technique was applied. Experimental results were evaluated by measuring the concentration of gold in solutions using the atomic adsorption method. The theoretical characteristics of gold dissolution using the proposed reagent were studied. In order to evaluate the applicability of the revealed regularities for practical purposes, comparative indicators for leaching gold from the ore of the Byn’govskoye deposit (Sverdlovsk Oblast) using the proposed reagent, cyanide and CYCAD cyanide substitute (China) were evaluated. The dependence of the gold disc dissolution rate on temperature, as well as leaching reagent and hydrochloric acid concentrations, were studied. In disc sample experiments, the exponential dependence of the dissolution rate on the concentration of the studied reagent was established. In this case, the maximum intensity of the process is achieved at a concentration higher than 50 g/dm3. The optimum acidity level comprises 0.3–0.4 g ion/dm3 of hydrochloric acid. Despite an increase in temperature being shown to accelerate the dissolution process, this appears to be technologically unjustified. Under optimal conditions, the gold disc dissolution rate reaches 0.5•10-3 g ion/(cm2•min), which is approximately one hundred times higher than during the dissolution by the cyanic solutions in conventional modes. Close gold extraction values were achieved in the solutions of cyanides and chlorine-bearing derivatives of isocyanuric acid during the leaching of gold from the ore under the comparable conditions. For CYCAD solutions, the same indicator is two times lower. The results of the performed studies demonstrate the high dissolution rate of gold using the proposed reagent along with the technological possibility of leaching gold from ores using this environmentally friendly reagent.

Bleaching of crude marula oil using activated bentonite and activated marula shells: A comparative analysis

Refining of edible and cosmetic oil consists of various steps which include bleaching process. Bleaching is an important step as it removes colour pigments resulting in improvement of taste of oil and appearance. In this work, activated bentonite and activated marula shells were used to refine crude marula oil. Fresh bentonite was activated using H2SO4 whilst marula shells were activated using both H2SO4 and KOH. Vacuum bleaching of crude marula oil was performed using both the activated bentonite and activated marula shells. Fresh, activated, spent bentonites and marula shells were analysed using X-ray Diffraction (XRD), Fourier transform infrared (FTIR), X-ray Florescence (XRF), Thermal gravimetric analysis (TGA) for phase identification, elemental composition of crystalline material, functional groups present and thermal decomposition of the materials. Analysis of β-carotene and chlorophyll was done using UV–visible spectrophotometer on bleached and crude marula oils. Acid values (AV) and free fatty acids (FFA) values in the oil were calculated using standard procedures. The effects of acid activation parameters were investigated namely, acid concentration and activation time. Acid and alkali activation improved the adsorption properties of fresh bentonite and fresh marula to remove colour pigments. Increase in acid concentration and activation time resulted in increase in bleaching capacity of adsorbent. Optimum acid concentrations for activation were 2 N and 15 N for bentonite and marula shells respectively and optimum activation times were 7 and 1.5 h for bentonite and marula shells respectively. The study indicated that activated bentonite and activated marula shells are effective and were successful in improving the appearance of crude marula oil to the required quality standards. Marula shells are a by-product waste in cosmetic oil processing and its use assists in waste utilization in-line with circular economy principles.