Set Of Optimal Conditions Research Articles

Optimization of waste cork powder torrefaction to improve biofuel parameters and storage properties

Waste cork torrefaction was optimized in order to improve the properties of this material for its application as biofuel. A two-level factorial design involving three factors -torrefaction temperature, torrefaction time and heating rate- was proposed with two-responses -mass yield (MY) and high heating value (HHV)-. Factorial design results revealed that torrefaction time and especially temperature were the most influential factors. Using simultaneous optimization of the two variables MY and HHV, and giving them two different weights, two different sets of optimum conditions were obtained. The first one (246 ºC, 60 min and 5 ºC/min) led to a biofuel with similar HHV as the raw material, therefore it did not give any benefit in terms of biofuel upgrading. The second one (275 ºC, 60 min and 5 ºC/min) gave a biofuel with 10% more energy density than the raw material, which allowed to classify this biofuel as lignite. Both torrefied samples showed significant increase in hydrophobic character. Finally, ATR-FTIR results revealed the occurrence of carbonization reactions during torrefaction.

A green approach for depolymerization of chitosan: applications in hydrogels

Chitooligosaccharides (COS) are depolymerized chains produced from the natural polymer chitosan and has been determined to exhibit improved biological activities, high solubility in neutral to slightly alkaline pH, because of the lower molecular weight (MW). This makes COS more attractive in biomedical applications. However, earlier studies focused on depolymerization techniques that were either cumbersome or expensive. Here, a convenient two-stage, green synthesis approach was developed and optimized, where gamma irradiation and oxidative degradation with H2O2 were used to depolymerize chitosan to produce COS for biomedical applications. The gamma radiation dose level, H2O2 degradation reaction’s temperature, time and H2O2 concentration were varied to obtain the mildest combination of reaction conditions. The most optimum set of conditions (15 kGy, 25oC, overnight reaction with 2% H2O2) yielded COS that was soluble in physiological pH range (7–8.5). The COS had a MW of 12.8 ± 1.6 kDa (which was a 95% reduction in MW), a 62.3% degree of deacetylation, and a crystallinity index of 33%. A photopolymerized hydrogel using this COS cross-linked with polyethylene glycol diacrylate (PEGDA) and carboxymethyl cellulose (CMC) was also developed. The hydrogel exhibited high swelling ratio (6.44–10.24), a porous morphology, a compression modulus of 4.5 ± 2.7 kPa (similar to soft tissues), and more than 95% biocompatibility with mammalian cells. This newly developed COS hydrogel involves a simple and green approach for the production of COS and shows promise as a scaffold for artificial soft tissue.

Miscanthus-Derived Energy Storage System Material Production.

Carbon derived from various biomass sources has been evaluated as support material for thermal energy storage systems. However, process optimization of Miscanthus-derived carbon to be used for encapsulating phase change materials has not been reported to date. In this study, process optimization to evaluate the effects of selected operation parameters of pyrolysis time, temperature, and biomass:catalyst mass ratio on the surface area and pore volume of produced carbon is conducted using response surface methodology. In the process, ZnCl2 is used as a catalyst to promote high pore volume and area formation. Two sets of optimum conditions with different pyrolysis operation parameters in order to produce carbons with the highest pore area and volume are determined as 614 °C, 53 min, and 1:2 biomass to catalyst ratio and 722 °C, 77 min, and 1:4 biomass to catalyst ratio with 1415.4 m2/g and 0.748 cm3/g and 1499.8 m2/g and 1.443 cm3/g total pore volume, respectively. Carbon material produced at 614 °C exhibits mostly micro- and mesosized pores, while carbon obtained at 722 °C comprises mostly of meso- and macroporous structures. Findings of this study demonstrate the significance of process optimization for designing porous carbon material to be used in thermal and electrochemical energy storage systems.

Subcritical Water Hydrolysis of Fresh and Waste Cooking Oils to Fatty Acids Followed by Esterification to Fatty Acid Methyl Esters: Detailed Characterization of Feedstocks and Products.

In this present work, the hydrolysis of a sample of rapeseed oil (RSO) and two waste cooking oil (WCO) samples in subcritical water has been carried out in a stirred batch stainless-steel reactor to produce fatty acids. Using RSO as a model triglyceride, the effects of reaction parameters on the yields of fatty acids were investigated to determine the optimum set of hydrolysis conditions to be a temperature of 300 °C, a reaction time of 60 min, and a vegetable oil-water mass ratio of 1:2. The set of optimum conditions was applied to the hydrolysis of the WCOs. Oleic acid was the dominant fatty acid with yields of 74.4 wt % from RSO and 57.5 and 72.4 wt % from the two WCOs, respectively, while palmitic acid was the second most abundant fatty acid with yields of up to 31 wt %. The feedstocks and fatty acid products were characterized by acid-base titration and thermogravimetric analysis (TGA). Thereafter, the hydrolysis products from the optimum conditions were esterified to their fatty acid methyl esters (FAMEs), which were further characterized by gas chromatography-mass spectrometry (GC/MS) and TGA. With RSO at the optimum hydrolysis conditions, acid-base titration gave a fatty acid yield of 97.2 wt %, while TGA gave 86 wt %. Under the same conditions, the yield of FAMEs from GC/MS analysis was 88.6 wt %, while TGA gave a FAMEs' yield of 91 wt %. This study showed that the simple TGA method provided detailed and complete characterization of lipid feedstocks and their conversion products. In addition, subcritical water hydrolysis can be used to valorize WCOs to fatty acids, with little or no extensive feedstock purification, for various applications including biodiesel production.

Radical scavenging capacity, antibacterial activity, and quantum chemical aspects of the spectrophotometrically investigated iridium (III) complex with benzopyran derivative.

A comprehensive aqueous phase spectrophotometric study concerning the trace level determination of iridium (III) by its reaction with benzopyran-derived chromogenic reagent, 6-chloro-3-hydroxy-7-methyl-2-(2′-thienyl)-4-oxo-4H-1-benzopyran (CHMTB), is performed. The complexing reagent instantly forms a yellow complex with Ir (III) at pH 4.63, where metal is bound to the ligand in a ratio of 1:2 as deduced by Job’s continuous variations, mole ratio, and equilibrium shift methods. The complex absorbs maximally at 413–420 nm retaining its stability for up to 4 days. An optimum set of conditions have been set with respect to the parameters governing the formation of the complex. Under the set optimal conditions, the Ir (III)-CHMTB complex coheres to Beer’s law between 0.0 and 1.5 µg Ir (III) mL−1. The attenuation coefficient and Sandell’s sensitivity are, respectively, 1.18×105 L mol−1 cm−1 and 0.00162 μg cm−2 at 415 nm. The correlation coefficient (r) and standard deviation (SD) were 0.9999 and ± 0.001095, respectively, whereas the detection limit as analyzed was 0.007437 μg ml−1. The interference with respect to analytically important cations and complexing agents has been studied thoroughly. It is found that the majority of the ions/agents do not intervene with the formation of the complex, thus adding to the versatility of the method. The results obtained from the aforesaid studies indicate a simple, fast, convenient, sensitive, and versatile method for microgram analysis of iridium (III) using CHMTB as a binding ligand. Furthermore, the studied complex is subjected to the evaluation of antibacterial and antioxidant capacity by employing the Agar Diffusion assay and DPPH. radical scavenging method, respectively. The results obtained from the mentioned assays reveal that the investigated complex possesses significant potency as an antibacterial and antioxidant agent. Finally, the computational approach through DFT of the formed complex confirmed the associated electronic properties of the studied complex.

Eco-Friendly Coagulant versus Industrially Used Coagulants: Identification of Their Coagulation Performance, Mechanism and Optimization in Water Treatment Process.

The evaluation of complex organic and inorganic coagulant’s performances and their relationships could compromise the surface water treatment process time and its efficiency. In this work, process optimization was investigated by comparing an eco-friendly chitosan with the industrially used coagulants namely aluminum sulfate (alum), polyaluminum chloride (PAC), and aluminum chlorohydrate (ACH) in compliance with national drinking water standards. To treat various water samples from different treatment plants with turbidity and pH ranges from 20–826.3 NTU and 5.21–6.80, respectively, 5–20 mg/L coagulant dosages were varied in the presence of aluminum, ferum, and manganese. Among all, 10 mg/L of the respective ACH and chitosan demonstrated 97% and 99% turbidity removal in addition to the removal of the metals that complies with the referred standard. However, chitosan owes fewer sensitive responses (turbidity and residual metal) with the change in its input factors (dosage and pH), especially in acidic conditions. This finding suggested its beneficial role to be used under the non-critical dosage monitoring. Meanwhile, ACH was found to perform better than chitosan only at pH > 7.4 with half dosage required. In summary, chitosan and ACH could perform equally at a different set of optimum conditions. This optimization study offers precise selections of coagulants for a practical water treatment operation.

Combined treatment based on synergism between hydrodynamic cavitation and H2O2 for degradation of cyanide in effluents

The main purpose of this research has been to evaluate and optimize the application of hydrodynamic cavitation (HC), combined with hydrogen peroxide, as a promising process for the effective degradation of cyanide in aqueous effluents. The experimental work was carried out using cavitation equipment with a venturi device connected to a tubular circuit which allowed a closed-cycle flow to run for 120 min, in which the effect of control parameters as inlet pressure, H2O2:CN─ ratio, pH, and temperature have been evaluated for the treatment of solutions with initial cyanide concentration in range 100 to 550 mg L─1.The results showed that in optimal conditions cyanide degradation using only HC reached 70% and, using solely H2O2 as oxidizing agent it reached 63%. Efficiency of the combined treatment process was evaluated on the basis of their synergetic effect as it turned out to be more effective showing a 99.9 % cyanide degradation in less than 120 min. The optimum set of conditions that produced the highest degradation rate and efficiency was: inlet pressure 4 bar; pH 9.5; and H2O2:CN─ ratio = 1.5:1. The process was also evaluated on the basis of cavitational yield and in terms of energy and chemical treatment costs. The results have demonstrated that the combined treatment technology of HC + H2O2 can be effectively used as a fast and highly efficient treatment of wastewater containing cyanide.

Limit analysis and frictional contact: formulation and numerical solution

The evaluation of structural integrity involves the determination of a limit state. If there is plasticity, limit analysis theory takes place. The aim of this paper is to present a limit analysis formulation considering friction at the contact interface. The deduction of this formulation involves the study of contact mechanics, unilateral conditions at normal direction and a slipping rule for the tangential direction. Concerning the contact between a rigid and a deformable body, at limit state there is permanent contact between the bodies and the contact length is supposed known. These hypotheses enable the development of a limit analysis formulation considering friction dissipation. The solution of a limit analysis problem is based on duality between the static, kinematic, mixed and the set of optimum conditions and its relation with the solution of a non-linear programming optimization problem with constraints. The solution is based on Newton method with contraction and relaxation techniques, associated with condensation technique to solve the linear complementarity problem at contact. As an application, the influence of friction coefficient at tool-specimen interface on the wedge indentation is evaluated.

Using a Taguchi DOE to investigate factors and interactions affecting germination in Miscanthus sinensis

The Miscanthus genus of perennial grasses is grown for bioenergy and biorenewable feedstocks. Most Miscanthus crop is M × giganteus which is rhizome propagated and therefore difficult to multiply at large scale. Seed-based propagation of new hybrids is being developed, but Miscanthus is difficult to establish from seed especially in the field. Miscanthus is often grown on marginal land adding to the challenge of successfully establishing the crop. Improved understanding of the limits and biology of germination in Miscanthus species is needed. Seed germination is affected by physical and chemical factors that impact germination differently depending on level of exposure. In this investigation of Miscanthus germination, four hormones plus water stress were investigated and the range over which these factors affect germination was determined. An efficient Taguchi experimental design was used to assess the five factors in combination with the effects of light and seed priming. This determined an example of a set of optimum conditions for Miscanthus germination and demonstrated how this could change based on fixing one condition. The experiment showed how environmental stress impacted germination and how treatments such as gibberellic acid could be used to mitigate stress.

Au-Pd nanoparticles enfolded in coil-like TiO2 immobilized on carbon fibers felt as recyclable nanocatalyst for benzene oxidation under mild conditions

Carbon fiber felt (CFF) is considered as a stable carbonaceous support for different applications such as absorbents and catalysts. Herein, a novel method for preparation of Au-Pd/CFF@TiO2 catalysts is presented. Structure, morphology, and performance of the novel nano-catalyst were characterized during different stages of their fabrication by means of structural, chemical and optical techniques. The results demonstrated that, compared with the other products, the Au-Pd/CFF@TiO2 composite pyrolyzed at 450 °C had the highest thermal and mechanical stability, as well as better textural features. It showed good catalytic activity in oxidation of benzene-to-phenol by hydrogen peroxide (25%) as eco-friendly oxidant under mild thermal conditions. The influence of different parameters on the oxidation process, such as reaction temperature, amounts of catalyst, oxidant/substrate molar ratio and condensation temperature, was investigated to optimize the catalyst. At the optimum set of conditions, the Au-Pd/CFF@TiO2-450 showed the values of yield and selectivity for phenol as the main product as high as 46% and 100%, respectively. The catalyst maintained its activity after eight cycles and thus looks very promising for direct conversion of benzene to phenol under mild conditions.

Determination of carcinogenic herbicides in milk samples using green non-ionic silicone surfactant of cloud point extraction and spectrophotometry.

A new cloud point methodology was successfully used for the extraction of carcinogenic pesticides in milk samples as a prior step to their determination by spectrophotometry. In this work, non-ionic silicone surfactant, also known as 3-(3-hydroxypropyl-heptatrimethylxyloxane), was chosen as a green extraction solvent because of its structure and properties. The effect of different parameters, such as the type of surfactant, concentration and volume of surfactant, pH, salt, temperature, incubation time and water content on the cloud point extraction of carcinogenic pesticides such as atrazine and propazine, was studied in detail and a set of optimum conditions was established. A good correlation coefficient (R2) in the range of 0.991–0.997 for all calibration curves was obtained. The limit of detection was 1.06 µg l−1 (atrazine) and 1.22 µg l−1 (propazine), and the limit of quantitation was 3.54 µg l−1 (atrazine) and 4.07 µg l−1 (propazine). Satisfactory recoveries in the range of 81–108% were determined in milk samples at 5 and 1000 µg l−1, respectively, with low relative standard deviation, n = 3 of 0.301–7.45% in milk matrices. The proposed method is very convenient, rapid, cost-effective and environmentally friendly for food analysis.

A STATISTICAL APPROACH FOR OPTIMIZING THE HIGH YIELD GREEN PRODUCTION OF THE FLAVOR ESTER BUTYL BUTYRATE

Being the prevailing approach for producing esters such as butyl butyrate, the use of chemical route has been linked to numerous disadvantages. Hence, a green alternative method for higher yield production of butyl butyrate by esterification reaction utilizing Novozyme 435 as biocatalysts in a solvent-less system may prove useful. Such approach can be further improved by optimizing the relevant reaction parameters using the Response Surface Methodology by the Box-Benkhen Design attempted in this present study. The reaction parameters evaluated were: substrate molar ratio, time and temperature, and the response of each parameter was measured as percentage conversion yield. Using the Design Expert 7.1.6 optimization functions, the two sets of optimum conditions selected viz. [i] molar ratio butyric acid:butanol 1:3.93, 9.93 h at 56.09°C and [ii] molar ratio butyric acid:butanol 1:3.35, 9.79 h at 53.90°C had afforded the highest yield of butyl butyrate i.e. 99.62% and 99.55%, respectively. The ester product obtained from the reaction were confirmed as butyl butyrate by FTIR and GC. Therefore, the results substantiated the applicability of the RSM prediction technique as well as efficacy of Novozyme 435 as biocatalysts in the high yield solvent-less synthesis of butyl butyrate, adhering to the philosophy of Green Chemistry.

Aminoethanethiol-Grafted Porous Organic Polymer for Hg2+ Removal in Aqueous Solution

A highly porous organic polymer, CBAP-1, was synthesized from terephthaloyl chloride and 1,3,5-triphenylbenzene via the Friedel–Crafts reaction, and functionalized with either ethylenediamine (EDA) or 2-aminoethanethiol (AET) for Hg2+ removal from water. Both materials were characterized by X-ray diffraction, N2 adsorption–desorption isotherms, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, inductively coupled plasma and elemental analysis, and the stability of the porous polymers under different pH and temperature conditions was examined. The adsorption experiments were carried out by varying contact time, Hg2+ concentration, and system pH to study the adsorption equilibrium and kinetics. The Hg2+ ion-adsorption capacities of CBAP-1(EDA) and CBAP-1(AET) were 181 and 232 mg/g, respectively, at room temperature and pH 5, and the observed adsorption isotherms could be fitted well to the Langmuir model (correlation factor R2 > 0.99). Under the optimum set of conditions, the adsorp...

Optimization of process conditions for biodiesel production over CaO–Al2O3/ZrO2 catalyst using response surface methodology

CaO–Al2O3/ZrO2 mixed oxide catalyst was prepared using free-solvent method. The catalyst was characterized using X-ray diffraction, BET surface area, acidity index (obtained by titration method), and scanning electron microscopy (SEM). With calcium aluminate and calcium zirconate been successfully formed, the mix exhibited small crystal size, high acidity, and large surface area, pore size, and pore volume, making it a catalyst of choice for biodiesel production. The activity of catalyst was evaluated in the course of esterification of oleic acid as well as transesterification of waste cooking oil (WCO) into biodiesel. Based on a four-variable central composite design (CCD), response surface methodology (RSM) was used to optimize effective variables on oleic acid conversion. The optimum yield of 94.68% was obtained at the following set of optimum conditions: reaction temperature of 120 °C, methanol/oleic acid molar ratio of 15.64, catalyst concentration of 2.94 wt%, and reaction time of 4 h; the result was in excellent agreement with the predicted values. Furthermore, under the optimum conditions, the catalyst succeeded to convert 93.48% of WCO into biodiesel.

Assessment of the Effect of Easily-metabolised Carbon Supplements on Xylanase Production by Newly Isolated Trichoderma asperellum USM SD4 Cultivated on Oil Palm Empty Fruit Bunches

Effect of lignocellulosic medium supplemented with selected easily-metabolised carbon sources on microbial xylanase production was assessed. A newly isolated oil-palm-waste-domesticated bio-agent-producing fungus, identified based on rRNA analysis as T. asperellum USM SD4 was used as a representative organism. The potential of T. asperellum for enhanced xylanase production was evaluated by the statistical optimization of important cultural parameters via response surface methodology (RSM). T. asperellum showed optimum xylanase activity at pH 7; temperature 27 °C; moisture content 4 mL growth medium (gm): 1 gram dried substrate (gds) and inoculum size 2 x 106 spores/mL. Xylanase activity (2,337 IU/gds) attained in this study was far higher than ever reported for T. asperellum. Using the set of optimum conditions, the mixture of supplementary sugars to the lignocellulosic medium initiated xylanase repression in a concentration-independent manner. However, the degree of repression depended on the nature and type of respectively added sugar. The repressive effect exerted by monosaccharides (xylose, glucose, and fructose) was greater than exerted by either of dimeric (cellobiose and sucrose) or polymeric (xylan) sugars. Of all added substrates, xylan exerted the least repressive effect. Using xylose as a representative sugar, mechanism of xylanase repression was decisively explained and supported with experimental data.

Improving the Analysis of Anthocyanidins from Blueberries Using Response Surface Methodology

Background: Recent interest in the health promoting potential of anthocyanins points to the need for robust and reliable analytical methods. It is essential to know that the health promoting chemicals are present in juices and other products processed from whole fruit. Many different methods have been published using a wide variety of conditions for the hydrolysis of anthocyanins to anthocyanidins. Objective: To investigate the factors influencing the hydrolytic conversion efficiency. The optimum set of conditions will maximize the recovery of anthocyanidins. Method: Extraction procedure (freeze drying vs. direct liquid extraction), heating method (reflux vs. sealed vial), nitrogen purging and acid type were investigated. Response surface methodology was then used to find the optimum combination of incubation time, acid concentration and incubation temperature. Results: Anthocyanidin recovery can be maximized using this procedure: Freeze-dry homogenized fruit and extract with methanol:water:TFA, place 1 mL extract or juice in a test tube and add 440 µL 37% HCl, purge the tube with N2, seal with a PTFE lined cap, vortex, then heat at 99°C for 6.4 minutes. Filter the hydrolysate into an autosampler vial and analyze by UPLC immediately. Conclusion: Maximizing the recovery of anthocyanidins (by manipulating conditions in order to maximize peak areas) leads to a more accurate measure of the anthocyanidins present in blueberries.

Modeling and Analysis of Drilling Induced Damages on Hybrid Composites

Background/Objectives: To investigate the damages that occurs during drilling on newly prepared hybrid composites. Methods/Analysis: Composites have been prepared by using randomly oriented steel wool and woven jute as reinforcements and polyester as the matrix resin. Drilling experiments have been carried out on the developed composite by adopting Box-Behnken methodology. Speed, feed rate, point angle and tool diameter are taken as the input factors and the damage at entrance and exit surfaces have been measured as output responses. Findings: The output factors have been analyzed and optimized to yield a set of optimum conditions on the basis of desirability approach. The results showed that speed, feed rate and tool angle have significant influence on the entrance and exit damages but tool diameter does not have any influence. A speed of 500 rpm-970 rpm, a constant feed of 0.1 mm/rev, a tool angle of 900-1200, and selection of 8 mm and 10 mm as tool diameter are found to be the optimum input conditions for drilling. Confirmatory experiments have been conducted for the set of optimum conditions and the responses have been measured. The developed model is validated by an error analysis between the model and confirmatory runs. The observed errors between the model and confirmatory runs are meagre and hence the optimization using Box-Behnken design is satisfactory. Novelty/Improvement: Machining associated failures must be resolved in order to improve the productivity. This research made an attempt to optimize drilling associated damages on new composites made by using metal and natural fibers as reinforcement.

Machinability of carbon/epoxy composites by electrical discharge machining

Through-thickness drilling of carbon/epoxy laminate by electrical discharge machining (EDM) was conducted using copper and graphite electrodes. Gap current and pulse-on time were varied and their effect on machinability of the composite laminate was assessed in terms of material removal rate, electrode wear, delamination factor, hole taper and deviation in hole size. It was found that the highest material removal rates were obtained with graphite electrode at the highest current and highest pulse-on time. On the other hand, these conditions also corresponded to the highest electrode wear rate, highest delamination damage and largest deviation in hole size. Hole taper was the least at these settings. An optimum set of conditions for EDM drilling could not be found within the ranges of parameters tested. However, due to the interaction between process parameters it is found that at intermediate levels of pulse-on time levels of delamination damage and deviation in hole size are the smallest. Therefore, effective EDM drilling with high MRR and low damage may be performed at high currents and intermediate pulse-on time.

Optimum conditions for the capture of carbon dioxide with a bubble-column scrubber

A continuous bubble-column scrubber, capturing CO2 gas for scrubber design purpose by using a NaOH solution under a pH-stat operation, is used to search for optimum parameters for a scrubber design by means of the Taguchi method. The parameters are the pH of the solution, gas-flow rate, liquid-flow rate and temperature, with four levels for each. A total of 16 runs are carried out by using a Taguchi experimental design. From the measured CO2 concentrations at the outlet, the absorption rate and overall mass-transfer coefficient can be determined with the support of a steady-state material balance, as well as a two-film model. According to an S/N ratio analysis, a significance sequence influencing the parameters and optimum conditions can be determined. The results show that the gas-flow rate and pH value are significant parameters, while the temperature and liquid flow rate are minor. A total of four sets of optimum conditions will be used to make further verification. The data determined here were found to be optimum. According to the analysis presented here, a policy for a scrubber design can be established. The results could be used to obtain an algae growth solution for biological carbon fixation in a pilot-scale study.

CO2 Capture Using Monoethanolamine in a Bubble‐Column Scrubber

AbstractA continuous bubble‐column scrubber, capturing CO2 gas by monoethanolamine (MEA) solution in a pH‐stat operation, is used to search for optimum process parameters by means of the Taguchi method. The process variables are the pH of the solution, gas flow rate, concentration of CO2 gas, and temperature. From the measured outlet CO2 gas concentrations, the absorption rate and overall mass transfer coefficient can be determined with the support of a steady‐state material balance equation as well as a two‐film model. According to the signal‐to‐noise ratio, the significance sequence influencing the parameters and optimum conditions can be determined. CO2 concentration and pH value proved to be decisive parameters, while temperature and gas flow rate were minor. Five sets of optimum conditions were obtained and could be further verified by empirical equations.