Statistical analysis and optimization of photodegradation efficiency of methyl orange from aqueous solution using cellulose/zinc oxide hybrid aerogel by response surface methodology (RSM)

The photodegradation efficiency of cellulose-X/zinc oxide-Y (CA-X/ZnO-Y) aerogels was studied to degrade methyl orange (MO) as an organic dye pollutant from an aqueous solution under UV light irradiation. In this study, the initial pH of the solution (3, 7, and 11), the photocatalyst dosage (3, 6, and 9 g L^-1), the initial concentration of solution MO (10, 20, and 30 ppm), and the concentration of cellulose in CA-X/ZnO-Y hybrid aerogel (3, 6, and 9 wt%) were selected as four variable parameters, whereas the photoderadation performance was selected as the response. Moreover, the response surface methodology (RSM) analysis was carried out to investigate the influence of four various experimental factors at different times on the degradation of MO. The adequacy result of the proposed models displays that total of the proposed models can predict the photodegradation efficiency of MO by CA-x/ZnO-y aerogel. The optimization results of the process showed that pH = 3 and concentration of MO = 10 ppm, photocatalyst dosage (9 g L^-1), and MCC concentration (9 g) are the optimal level of the studied parameters. Also, the results showed that desirability of 0.96 confirms the acceptance and applicability of the model where the RSM model is a helpful technique for the optimum conditions design.     

Green extraction process of tannins obtained from Moroccan Acacia mollissima barks by microwave: Modeling and optimization of the process using the response surface methodology RSM

The effect of extraction conditions on polyphenols contents and condensed tannins by microwave-assisted extraction (MAE) was studied for the first time to our knowledge. Moroccan barks of Acacia mollissima was used to extract phenolic compounds. The variables studied are the following: power extraction, time extraction and solvent nature. Five powers extraction were tested: 150 W, 250 W, 300 W, 450 W and 600 W. A significant effect of power extraction on the extractable nature was proved by ANOVA and Student test. The yields were also affected by time extraction. Different solvent (water, ethanol, methanol and ethyl acetate) were tested to evaluate the best extraction solvent according to the extractable nature. Highest polyphenols contents were obtained with methanol. The proportion of this solvent, time extraction and power extraction were optimized using the response surface methodology (RSM). A face-centered composite design (FCCD) was applied to evaluate the effects of these variables on the polyphenols and condensed tannins contents. For each experiment, the extraction yield, the total polyphenolic contents and the condensed tannins contents were quantified using colorimetric essays. The extracts were characterized by their reactivity to formaldehyde and reverse phase high pressure liquid chromatography (RP-HPLC). The highest polyphenols content was obtained at 156 W using 80% of methanol during 5 min. For condensed tannins, the highest content of cyanidin was obtained at 182 W using 20% of methanol during 3.66 min. RSM applied in MAE, permitted to develop green extraction process of polyphenols and tannins extracted, using lower microwave power and methanol proportion with a shortest time extraction and in the same time improve the quantity of extractables obtained from renewable natural resource.     

Applying sequential injection analysis (SIA) and response surface methodology for optimization of Fenton-based processes

This work presents the use of sequential injection analysis (SIA) and the response surface methodology as a tool for optimization of Fenton-based processes. Alizarin red S dye (C.I. 58005) was used as a model compound for the anthraquinones family, whose pigments have a large use in coatings industry. The following factors were considered: [H₂O₂]:[Alizarin] and [H₂O₂]:[FeSO₄] ratios and pH. The SIA system was designed to add reagents to the reactor and to perform on-line sampling of the reaction medium, sending the samples to a flow-through spectrophotometer for monitoring the color reduction of the dye. The proposed system fed the statistical program with degradation data for fast construction of response surface plots. After optimization, 99.7% of the dye was degraded and the TOC content was reduced to 35% of the original value. Low reagents consumption and high sampling throughput were the remarkable features of the SIA system.     

Highly sensitive kinetic spectrophotometric method for tramadol trace level detection and process optimization using response surface methodology

Tramadol is a centrally acting analgesic‐anodyne agent of high oral bioavailability. The tramadol contains a weakly absorbing chromophore in its molecule and it was determined by kinetic spectrophotometric method in pharmaceutical, urine, and blood plasma. Response surface methodology and the central composite design was applied to study the influence of maximum sensitivity, reagents concentration, temperature, and time on the UV–Vis spectrophotometry analysis of tramadol. Analysis of variance showed a high coefficient of determination (R²) value for responses, confirming adjustment of the models with experimental data. The change in absorbance was followed spectrophotometrically at 478 nm. Under optimum experimental conditions, calibration curve was linear over the range 0.45–100.0 μg/L of tramadol. The limit of detection was 0.12 μg/L of tramadol. The developed method was successfully applied for the determination of tramadol in real samples.     

Optimization of extraction of linarin from Flos chrysanthemi indici by response surface methodology and artificial neural network

The extraction of linarin from Flos chrysanthemi indici by ethanol was investigated. Two modeling techniques, response surface methodology and artificial neural network, were adopted to optimize the process parameters, such as, ethanol concentration, extraction period, extraction frequency, and solvent to material ratio. We showed that both methods provided good predictions, but artificial neural network provided a better and more accurate result. The optimum process parameters include, ethanol concentration of 74%, extraction period of 2 h, extraction three times, solvent to material ratio of 12 mL/g. The experiment yield of linarin was 90.5% that deviated less than 1.6% from that obtained by predicted result.     

(CaO-Y2O3)@LiFe5O8 magnetic catalyst by doping yttrium for improving stability: Optimized by response surface methodology for biodiesel production

In this work, CaO@LiFe₅O₈ and (CaO-Y₂O₃)@LiFe₅O₈ solid base catalysts were synthesized using LiFe₅O₈ as the magnetic core to support the active centers. The as-prepared catalysts and commercial CaO were characterized using X-ray diffraction, scanning electronic microscope, and CO₂-temperature-programmed desorption techniques. The results indicated that CaO@LiFe₅O₈ and (CaO-Y₂O₃)@LiFe₅O₈ solid base catalysts, which could be recycled under the external magnetic field because of their strong magnetism, exhibited better dispersibility and higher total number of basic sites compared with commercial CaO. Additional water and oleic acid were added to the reaction system of palm oil with methanol, and the catalyst was exposed to air to detect its stability in the reaction process. The experiments showed that the (CaO-Y₂O₃)@LiFe₅O₈ solid base catalyst performed better and possessed not only good water resistance ability but also preferable tolerance to air exposure. In addition, response surface methodology based on the Box–Behnken design was used to optimize the process parameters for the synthesis of biodiesel from palm oil and methanol in the presence of (CaO-Y₂O₃)@LiFe₅O₈. The optimum process conditions were determined as follows: reaction temperature was 64.96°C, reaction time 4.36 hr, methanol: oil 13, catalyst amount 3.73%, and the highest biodiesel yield reached 96.21%.     

Optimisation of steam distillation extraction oil from onion by response surface methodology and its chemical composition

Oil extraction from onion was performed by steam distillation. Response surface methodology was applied to evaluate the effects of ratio of water to raw material, extraction time, zymolysis temperature and distillation times on yield of onion oil. The maximum extraction yield (1.779‰) was obtained as following conditions: ratio of water to raw material was 1, extraction time was 2.5 h, zymolysis temperature was 36° and distillation time was 2.6 h. The experimental values agreed well with those predicted by regression model. The chemical composition of extracted onion oil under the optimum conditions was analysed by gas chromatography-mass spectrometry technology. The results showed that sulphur compounds, like alkanes, sulphide, alkenes, ester and alcohol, were the major components of onion oil.     

Production of octyl levulinate biolubricant over modified H-ZSM-5: Optimization by response surface methodology

The present study highlighted the use of modified H-ZSM-5 (Meso-HZ-5) as heterogeneous catalyst for the synthesis of octyl levulinate biolubricant by catalytic esterification of biomass derived renewable levulinic acid (LA) with n-octanol. The process variables such as catalyst loading (X₁), n-octanol to LA molar ratio (X₂) and reaction temperature (X₃) were optimized through response surface methodology (RSM), using Box-Behnken model. Analysis of variance was performed to determine the adequacy and significance of the quadratic model. The yield of octyl levulinate was obtained to be 99% at optimum process parameters. The developed quadratic model was found to be adequate and statistically accurate with correlation value (R²) of 0.9971 to predict the yield of octyl levulinate biolubricant. The study was also extended on the validation of theoretical and experimental data, including catalyst reusability.     

Sequential injection analysis (SIA) and response surface methodology: A versatile small volume approach for optimization of photo-Fenton processes

Optimization of photo-Fenton degradation of copper phthalocyanine blue was achieved by response surface methodology (RSM) constructed with the aid of a sequential injection analysis (SIA) system coupled to a homemade photo-reactor. Highest degradation percentage was obtained at the following conditions [H₂O₂]/[phthalocyanine] = 7, [H₂O₂]/[FeSO₄] = 10, pH = 2.5, and stopped flow time in the photo reactor = 30 s. The SIA system was designed to prepare a monosegment containing the reagents and sample, to pump it toward the photo-reactor for the specified time and send the products to a flow-through spectrophotometer for monitoring the color reduction of the dye. Changes in parameters such as reagent molar ratios, residence time and pH were made by modifications in the software commanding the SI system, without the need for physical reconfiguration of reagents around the selection valve. The proposed procedure and system fed the statistical program with degradation data for fast construction of response surface plots. After optimization, 97% of the dye was degraded.     

Treatment of CNC industry wastewater by electrocoagulation technology: an application through response surface methodology

ABSTRACT

Removal of COD, and several toxic heavy metals (Cu²⁺ and Ni²⁺) from CNC (metalworking fluid) wastewater was investigated using electrocoagulation method (EC) with Fe and Al electrodes. The interaction effects of the current density, reaction time and initial pH were analyzed and were correlated to assess the removal efficiencies for COD, copper, and nickel. Coefficient of determination (R²) and adjusted R² was found to be higher than 96.81% and 92.77; 99.01% and 89.94 for all responses at Fe and Al electrodes, respectively. Removal efficiencies were determined to be 95.72%, 96.03%, 95.22% and 97.11%, 98.51%, 92.49% for COD, copper and nickel at iron and aluminum electrodes, respectively under optimum operating conditions. The operational cost of the EC process for COD, copper, and nickel removal, were found to be 2.54, 3.36, 2.50 €/m³ for iron electrode and 7.16, 8.95, 8.50 €/m³ for aluminum electrode at optimum conditions, respectively. The results provide that The EC process seems to be an effective treatment method for removing COD and several trace heavy metals from the CNC machine (metalworking fluid) wastewater.     

Remarkable bismuth-gold alloy decorated on MWCNT for glucose electrooxidation: the effect of bismuth promotion and optimization via response surface methodology

In this study, the carbon nanotube supported gold, bismuth, and gold-bismuth(Au/MWCNT, Bi/MWCNT, and Au-Bi/MWCNT) nanocatalysts were prepared with NaBH₄ reduction method at varying molar atomic ratio for glucose electrooxidation (GAEO). The synthesized nanocatalysts at different Au: Bi atomic ratios are characterized via x - ray diffraction (XRD), transmission electron microscopy (TEM), and N₂ adsorption-desorption. For the performance of AuBi/MWCNT for GAEO, electrochemical measurements are performed by using different electrochemical techniques namely cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). Monometallic Au/MWCNT exhibits higher activity than Bi/MWCNT with 256.57 mA/mg (0.936 mA/cm²) current density. According to CV results, Au₈₀Bi₂₀/MWCNT nanocatalyst has the highest GAEO activity with the mass activity of 320.15 mA/mg (1.133 mA/cm²). For Au₈₀Bi₂₀/MWCNT, central composite design (CCD) is utilized for optimum conditions of the electrode preparation. Au₈₀Bi₂₀/MWCNT nanocatalysts are promising anode nanocatalysts for direct glucose fuel cells (DGFCs).     

Extraction optimization by response surface methodology: Purification and characterization of phytosterol from sugarcane (Saccharum officinarum L.) rind

A green, simple, and effective method for the extraction of sugarcane lipids from sugarcane rind was investigated by response surface methodology. The optimum conditions of technological progress obtained through response surface methodology were as follows: liquid‐to‐solid ratio 7.94: 1 mL/g, extraction temperature 50°C and extraction time 5.98 h. The practical sugarcane lipids extraction yield was 6.55 ± 0.28%, which was in good consistence with the predicted extraction yield of 6.47%. The results showed that the sugarcane lipids extraction yield obtained in optimum conditions increased by 1.16～7.28‐fold compared to the yields obtained in single‐factor experiments. After saponification and SPE steps, the nonsaponifiable fraction of sugarcane lipids was analyzed by gas chromatography with mass spectrometry and high‐performance liquid chromatography. β‐Sitosterol, stigmasterol, and campesterol were the prevailing phytosterols in the sample, while fucosterol, gramisterol, stigmast‐7‐en‐3‐ol, (3β,5α,24S)‐, stigmasta‐4,6,22‐trien‐3α‐ol, and cholest‐8(14)‐en‐3β‐ol acetate were also identified as minor steroids. Furthermore, the content of β‐sitosterol and a mixture of campesterol and stigmasterol (quantified by high‐performance liquid chromatography) was 44.18 mg/100 g dry weight and 43.20 mg stigmasterol/100 g dry weight, respectively. Our results indicate that sugarcane rind is a good source of phytosterol.     

Optimization of keratinase production and enzyme activity using response surface methodology with streptomyces sp7

A two-step response surface methodology (RSM) study was conducted for the optimization of keratinase production and enzyme activity from poultry feather byStreptomyces sp7. Initially different combinations of salts were screened for maximal production of keratinase at a constant pH of 6.5 and feather meal concentration of 5 g/L. A combination of K₂HPO₄, KH₂PO₄, and NaCl gave a maximum yield of keratinase (70.9 U/mL) production. In the first step of the RSM study, the selected five variables (feather meal, K₂HPO₄, KH₂PO₄, NaCl, and pH) were optimized by a 2⁵ full-factorial rotatable central composite design (CCD) that resulted in 95 U/mL of keratinase production. The results of analysis of variance and regression of a second-order model showed that the linear effects of feather meal concentration (p<0.005) and NaCl (p<0.029) and the interactive effects of all variables were more significant and that values of the quadratic effects of feather meal (p<1.72e-5), K₂HPO₄ (p<4.731e-6), KH₂PO₄ (p<1.01e-10), and pH (p 7.63e-7) were more significant than the linear and interactive effects of the process variables. In the second step, a 2³ rotatable full-factorial CCD and response surface analysis were used for the selection of optimal process parameters (pH, temperature, and rpm) for keratinase enzyme activity. These optima were pH 11.0, 45°C, and 300 rpm.     

Optimization of methane conversion to liquid fuels over W-Cu/ZSM-5 catalysts by response surface methodology

The conversion of methane to liquid fuels is still in the development process. The modified HZSM-5 by loading with Tungsten （W） enhanced its heat resistant performance, and the high reaction temperature （800℃） did not lead to the loss of W component by sublimation. The loading of ZSM-5 with Tungsten and Copper （Cu） resulted in an increment in the methane conversion, CO2, and C5＋ selectivities. The high methane conversion and C5＋ selectivity, and low H2O selectivity are obtained by using W/3.0Cu/ZSM-5. The optimization of methane conversion over 3.0 W/3.0Cu/ZSM-5 under different temperature and oxygen concentration using response surface methodology （RSM） are studied. The optimum point for methane conversion is 19% when temperature is 753 ℃, and oxygen concentration is 12%. The highest C5＋ selectivity is 27% when temperature is 751 ℃. and oxwen concentration is 11%.     

The production of enantiomerically pure 1-phenylethanol by enzymatic kinetic resolution method using response surface methodology

As the enantiomers of 1-phenylethanol are valuable intermediates in several industries, the lipase catalyzed kinetic resolution of (R,S) -1-phenylethanol is a relevant research topic. In this study, the goal was to determine the optimum reaction parameters to produce enantiomerically pure 1-phenylethanol by lipase (Novozyme 435) catalyzed kinetic resolution using response surface methodology (RSM). Reactions were performed with 40–400 mM (R,S)-1-phenylethanol, 120–1200 mM vinyl acetate and 2–22 mg/mL biocatalyst concentrations (BC _L ), at 20–60 °C and with a stirring rate of 50–400 rpm for 5–120 min. The samples were analyzed using high performance liquid chromatography (HPLC) with a Chiralcel OB column. Optimum reaction parameters to reach 100% enantiomeric excess for the substrate ( ee _s ) were determined as follows: substrate concentration (C _s ): 240 mM, BC _L : 11 mg/mL, at 42 °C with a reaction time of 75 min. Model validation was performed using these conditions and ee _s was calculated as 100%, which indicates the predicted model was efficient and accurate. When compared to the literature, it was observed that the reaction time decreased significantly. This is an important result considering the industrial scale perspective.     

Optimisation of extraction conditions for total saponins from Cynanchum wallichii using response surface methodology and its anti-tumour effects

Cynanchum wallichii Wight, is a traditional Chinese medicine herb, which is rich in saponins and has varieties of pharmacological activities. In this study, a standardized C. wallichii extract was established and the anti-tumor activity of the total saponins was evaluated by MTT assay. The extraction conditions of the standardized extract was optimized using response surface methodology. The experimental value was in good agreement (the yield 4.28%) with predicted values. The total saponins of the extract showed significant anti-tumor activity against three human tumor cell lines (A549, HepG2 and MCF-7), especially for MCF-7 (IC₅₀. 67.63 μg/mL) cells in vitro.     

Quantitative studies of rhubarb using quantitative analysis of multicomponents by single marker and response surface methodology

In this work, we developed a novel approach to evaluate the contents of bioactive components in rhubarb. The present method was based on the quantitative analysis of multicomponents by a single‐marker and response surface methodology approaches. The quantitative analysis of multicomponents by a single‐marker method based on high‐performance liquid chromatography coupled with photodiode array detection was developed and applied to determine the contents of 12 bioactive components in rhubarb. No significant differences were found in the results from the quantitative analysis of multicomponents by a single‐marker and the external standard method. In order to maximize the extraction of 12 bioactive compounds in rhubarb, the ultrasonic‐assisted extraction conditions were obtained by the response surface methodology coupled with Box–Behnken design. According to the obtained results, we showed that the optimal conditions would be as follows: proportion of ethanol/water 74.39%, solvent‐to‐solid ratio 24.07:1 v/w, extraction time 51.13 min, and extraction temperature 63.61°C. The analytical scheme established in this research should be a reliable, convenient, and appropriate method for quantitative determination of bioactive compounds in rhubarb.     

Optimization of cadmium adsorption from aqueous solutions by functionalized graphene and the reversible magnetic recovery of the adsorbent using response surface methodology

Novel functionalized graphene adsorbent was prepared and characterized using different techniques. The prepared adsorbent was applied for the removal of cadmium ions from aqueous solution. A response surface methodology was used to evaluate the simple and combined effects of the various parameters, including adsorbent dosage, pH, and initial concentration. Under the optimal conditions, the cadmium removal performance of 70% was achieved. A good agreement between experimental and predicted data in this study was observed. The experimental results revealed of cadmium adsorption with high linearity follow Langmuir isotherm model with maximum adsorption capacity of 502 mg g^?1, and the adsorption data fitted well into pseudo‐second order model. Thermodynamic studies showed that adsorption process has exothermic and spontaneous nature. The recommended optimum conditions are: cadmium concentration of 970 mg L^?1, adsorbent dosage of 1 g L^?1, pH of 6.18, and T = 25 °C. The magnetic recovery of the adsorbent was performed using a magnetic surfactant to form a noncovalent magnetic functionalized graphene. After magnetic recovery of the adsorbent both components (adsorbent and magnetic surfactant) were recycled by tuning the surface charges through changing the pH of the solution. Desorption behavior studied using HNO₃ solution indicated that the adsorbent had the potential for reusability.     

Chemometric tools in electroanalytical chemistry: Methods for optimization based on factorial design and response surface methodology

The aim of this paper is to give a brief overview of chemometric techniques based on factorial designs and response surface methodologies used in the optimization of electroanalytical methods. Chemometric techniques have several important advantages over one-way optimization for analytical applications, including a relatively low cost, a reduced number of experiments, and possibilities to evaluate interactions among variables. These techniques also enable the selection of optimal experimental conditions, helping to avoid trivial mistakes during optimization. Despite these facts, chemometric techniques have rarely been applied to electroanalytical data, especially in comparison with their use in spectroscopy. The application of chemometric methods in electroanalytical chemistry has been mostly used for solving overlapping signals, multivariate calibration methods, model identification and optimization of analytical procedures. This review is focused on the latter applications and overviews the role of full or fractional factorial designs (first-order designs), as well as second-order designs, such as central composite, Doehlert and Box-Behnken designs, for optimization of electroanalytical methods. A discussion of chemometric-related advantages is also given for stripping analyses, flow injection systems with amperometric detection, differential pulse voltammetry, square wave voltammetry and electrochemical sensor preparation.