Box-Behnken Statistical Experiment Design Research Articles

Evaluation and optimisation of phenolic compounds extracted by supercritical carbon dioxide from the seeds of Plantago ovata and their comparison with conventional extraction

This study’s main objectives are to evaluate and confirm the effects of the extraction process, operating conditions, solvent type and solvent polarity on the yield and quality of the extracts. Supercritical carbon dioxide (scCO2) and Soxhlet were specially used in this study to extract bioactive chemicals from the seeds of a natural plant known as Plantago ovata. No studies have been published so far regarding the extraction from the seeds of this plant using scCO2.The effects of three operating parameters (pressure, temperature and particle size) on the extraction yield, total phenolic content, total flavonoid content (TFC), total tannin content (TTC) and antioxidant activity were assessed in this study using the Box–Behnken statistical experimental design (BBD). The chemical components in the extracts were separated and identified using gas chromatography mass spectrometry. According to the antioxidant activity results, scCO2 failed to produce bioactive compounds with interesting properties when operated within operating range conditions.

Optimization of the Hydrolysis Process of Microalgae Porphyridium cruentum Biomass with Variations of Hydrochloric Acid Concentration, Temperature, and Time using Response Surface Methodology (RSM)

Microalgae Porphyridium cruentum has potential as a raw material for bioethanol production because it has a high carbohydrate content. These carbohydrates can be broken down into reducing sugars through the hydrolysis process. The reducing sugar obtained will be used as a substrate in the production of bioethanol. This study aimed to produce a substrate with the best-reducing sugar indicator and to determine the optimum conditions for hydrolysis of P. cruentum microalgae biomass following the Box-Behnken statistical experimental design, using Response Surface Methodology (RSM). The parameters of the optimized hydrolysis process were HCl concentration (2 - 0.2 N), temperature (60 -120 ˚C), and hydrolysis time (30-180 min). The optimum conditions that have been achieved using RSM are an HCl concentration of 1.91 N, a temperature of 60 °C, and a hydrolysis time of 180 min were predicted a maximum total reducing sugar production of 810 mg/L. The experimental result of total reducing sugar obtained at optimum conditions was 895 mg/L, which was well close to the predicted value, verifying the appropriateness of the model.Abstract is informed about the statements of the problem, methods, scientific finding results and conclusion concisely

Optimizing biohydrogen production yields by employing locally isolated thermophilic bacteria from hot springs

A climate-neutral economy is anticipated to rely heavily on hydrogen because it enables emission-free transportation, heating, and manufacturing operations. Biohydrogen can be produced from various kinds of biological waste making the interest high. However, the yield and efficiency of the processes are still challenging. This study applied Box-Behnken statistical experimental design to investigate the influence of temperature (oC), pH, and CO volume (mL) together with the amount of Fe+2, Zn+2, and Ni+2 to enhance biohydrogen production yields from thermophilic cultures, both mixed and pure cultures isolated from hot springs in Izmir, Türkiye. The maximum H2 yields were reported as 0.13 mmolH2/mmolCO for mixed cultures, and the pure culture reached 2.5 fold higher yield (0.44 mmolH2/mmolCO). Bench-scale bioreactor with a custom-design micro sparger was successfully run for 7 days (highest 0.25 mmolH2/mmol CO). This is the first report in the literature with local isolates to demonstrate the optimization of H2 yields with a comparative approach, and scale-up in a 2 L bench scale bioreactor. The viability of using novel thermophilic isolates as biohydrogen producers was successfully proven.

Development and optimization of in-situ gels for vaginal delivery of metronidazole and curcumin via box-behnken design: In vitro characterization and anti-trichomonas activity

The aim of this study was to develop and optimize vaginal poloxamer in-situ gel formulations with metronidazole and curcumin combination for the treatment of infections caused by parasitic protozoa, Trichomonas vaginalis. Protozoan parasite infections cost the globe a colossal burden in terms of human and animal health. Lack of medication in low-income countries and rising drug resistance are posing substantial challenges in control and eradication of this infection. Today there is a tremendous drift in new alternative/synergic treatment strategies. Combination treatment, in particular, appear to be a promising approach against persistent, common, and infectious diseases like T. vaginalis. Poloxamer in-situ gels were prepared and optimized using the Box-Behnken statistical experiment design concept. The effect of critical parameters on critical quality features were evaluated by measuring the Tsol-gel transition temperature, solubilizing capacity of active substances in poloxamer bases, plastic viscosity, dynamic viscosity, and yield values. Optimized formulations (OPT-F1; F2; F3) were also tested for flow and mechanical properties, in-vitro release properties, cytotoxicity against the SK-HEP-1 cell line, and antiparasitic activity. The optimum formulations include properties that make them appropriate for vaginal administration and have been shown to be non-cytotoxic. The candidate gel formulation (OPT-F3) demonstrated statistically significant in-vitro activity against T. Vaginalis viability, demonstrating its antiparasitic effect. Stability studies conducted at 4 °C and 25 °C temperatures revealed that the ideal formulations retained their stability for 90 days. The study found that the gel containing metronidazole and curcumin is an effective and innovative approach to treating trichomoniasis and advances scientific research in this field.

Pillared bentonite from Al-Fe-Cu polymeric precursor in solid state for the catalytic oxidation of amoxicillin

A Colombian bentonite is successfully pillared with Al, Al-Fe, Al-Cu and Al-Fe-Cu polyhydroxications in solid state. The effect of the Fe and Cu content on the physicochemical properties of the pillared bentonite was evaluated using characterization techniques such as X-ray fluorescence (XRF), X-ray diffraction (XRD) and textural analysis (nitrogen physisorption). The Box-Behnken statistical experiment design was used to determine the optimal parameters of the independent variables hydrogen peroxide (0.120–0.144 M), catalyst load (0.5–1.5 g/L) and type of catalyst (PILC FeCu1, FeCu5, FeCu10) in the catalytic oxidation (CWPO) of amoxicillin. The optimized conditions of hydrogen peroxide (0.137 M) and catalyst loading (0.7 g/L) were used to compare the catalytic performance of the catalysts with 1%, 5% and 10% Al-Fe, Al-Cu and Al-Fe-Cu reaching a removal between 91% and 100% of amoxicillin at T and ambient pressure. The rate constants determined allowed the identification of the best catalyst of each series to study the degree of mineralization and choose the best catalyst: the pillared clay with AlFeCu10, with a TOC removal of 24.6% after 2 h of reaction. After three cycles of reuse, the catalyst maintained its catalytic activity in removing amoxicillin without leaching any metal.

Optimization of Coagulation-Flocculation Process in Efficient Arsenic Removal from Highly Contaminated Groundwater by Response Surface Methodology.

Elevated arsenic (As) contamination in water, especially groundwater, has been recognized as a major problem of catastrophic proportions. This work explores As(V) removal via the coagulation-flocculation process by use of ferric chloride coagulant and polyacrylamide k16 co-coagulant as a first time. The effects of major operating variables such as coagulant dosing (50, 125 and 200 mg/L), co-coagulant dosing (5, 12.5 and 20 mg/L), pH (6, 7and 8), fast mixing time (1, 2 and 3 min), and fast mixing speed (110, 200 and 300 rpm) on As(V) removal efficiency were investigated by a Box-Behnken statistical experiment design (BBD) and response surface methodology (RSM). According to factors F values, coagulant dosing, rapid mixing speed, pH, and co-coagulant dosing showed the most effect on As(V) removal efficiency, and the rapid mixing time factor indicated the slightest effect. The proposed quadratic model was significant with a p value < 0.0001 and has satisfactorily described the experimental data with R2 and adjusted R2 values of 0.9855 and 0.9738, respectively. Predicted model optimal conditions with target of complete As(V) removal were coagulant dosing = 197.63 ppm, co-coagulant dosing = 19.55 ppm, pH = 7.37, fast mixing time = 1.43 min and fast mixing speed = 286.77 rpm. The treatment of Nazarabad well water sample with an initial As(V) concentration of 5 mg/L under the optimal conditions removed 100% As(V) with the volume of produced sludge of 10.7 mL/200 mL. Increasing coagulant dosing, co-coagulant dosing, fast mixing time and fast mixing speed operation parameters from low-level to high-level values indicated 78%, 20%, 10.52% and 9.47% increases in volume of the produced sludge, respectively. However, a reduction of 13.63% in volume of the produced sludge resulted via pH increases.

Application of hybrid electrocoagulation and electrooxidation process for treatment of wastewater from the cotton textile industry.

The hybrid electrocoagulation-electrooxidation (EC-EO) process was evaluated for its capability to remove color, total organic carbon (TOC), and chemical oxygen demand (COD). Aluminum (Al/Al) and iridium dioxide-coated onto titanium (IrO2/Ti) electrodes were selected as anode/cathode for EC and EC-EO experiments, respectively. The box-Behnken statistical experimental design was used to optimize different operating conditions of the processes. The selected EC operating parameters are the concentrated dye concentration, applied current density, electrolysis time, and pH. The three chosen operating conditions for hybrid EC- EO processes are applied current density, pH, and electrolysis time. The results were evaluated based on the interaction effects of operating parameters of the treatment methods on the percentage of COD, TOC, and color removal. The EC process achieved 89% color and 76% COD removal rate at the optimum operating conditions. Likewise, the hybrid EC-EO process obtained 97% COD and color removal efficiency. FT-IR and 1H and 13C NMR spectroscopy combined approach was employed to analyze the dye degradation extent. Both analysis results confirm the complete degradation of the organic contaminants into carbon dioxide and water. Thus, this study discloses that the treatment method using mesh IrO2/Ti electrodes is a promising technology that could reach the discharge limit for industrial effluents. In addition, the optimum operating conditions are tested for real industrial wastewater effluents and show excellent performance in removing pollutants. Furthermore, the treatment method's mineralization study and economic analysis were performed and compared to other studies.

Use of aluminum-based water treatment sludge as coagulant for animal farm wastewater treatment

Unlike other studies of artificial wastewater treatment, this study aims to use the aluminum-based water treatment sludge (Al-WTS) as a substitute for traditional chemicals as coagulant in the coagulation-flocculation process for a real animal farm wastewater treatment. The study was designed for a lab-scale trial to explore the optimum conditions of coagulation and flocculation process so that the removal efficiencies of the total suspended solids (TSS), total organic carbon (TOC) and PO43− concentration of the wastewater can be maximized. The experiments were conducted in a series jar-test apparatus to simulate the coagulation-flocculation process. The effects of initial pH and the dosage of liquid Al-WTS on the removal efficiencies of the animal farm wastewater were examined and discussed. Moreover, a Box-Behnken statistical experimental design (BBD) by Design expert 8.0 was used to optimize the experimental conditions. At the optimum initial pH value of 7.0 and Al-WTS dosage of 1588 mg/L, the removal efficiencies of TSS, PO43−, and TOC were 87.8 ± 2.2%, 96.9 ± 2.9%, and 62.1 ± 1.8%, respectively. It is concluded that the Al-WTS could be used for the treatment of animal farm wastewater with considerable removal efficiencies, thus opening a cost-effective way for using a “waste” for wastewater treatment.

AQbD Driven Development of an RP-HPLC Method for the Quantitation of Abiraterone Acetate for its Pharmaceutical Formulations in the Presence of Degradants

Abiraterone acetate is a well-known anticancer drug and a steroidal derivative of progesterone for treatment of patients with hormone-refractory prostate cancer. Chemometrics-assisted reverse phase high performance liquid chromatography (RP-HPLC) development of the drug abiraterone acetate has been employed in this study using an analytical quality by design (AQbD) approach. Drug separation was performed using a Princeton Merck-Hibar Purospher STAR (C18, 250 mm × 4.6 mm) i.d., 5 μm particle size) with ultraviolet detection at 235 nm. A Box-Behnken statistical experimental design with response surface methodology was executed for method optimization and desired chromatographic separation from its formulation with a few numbers of experimental trials. The impact of three independent variables, namely, composition of the mobile phase, pH, and flow rate, on response retention time and peak area was studied by constructing an arithmetic model from these variables. Optimized experimental conditions for the proposed work include the mobile phase acetonitrile and phosphate buffer (10 mM KH2PO4) (20:80 %v/v). At the concentration range of 2-100 μg/mL, a linear calibration curve was found. Recovery was performed at three concentrations and was foun to be between 98% and 102%. The 3D response surface curves revealed that mobile phase composition and flow rate were the most substantial critical factors affecting desired responses. An attempt has been made to develop and validate an economical, precise, robust, stability-indicating AQbD-based RP-HPLC method that can be employed successfully for the routine analysis of abiraterone acetate in quality control labs.

Applicability of innovative adsorbents in geogenic arsenic removal

Exposure to high concentrations of geogenic arsenic via well-waters is a worldwide health concern. The purpose of the present work was to search the experimental results of the behavior of raw Uspheres (RU), iron Uspheres (FeU), iron Uspheres 200 °C (FeU@200°C) in the removal of arsenic in accordance with some factors impacting the adsorption process. Some study parameters including initial pH (2–10), adsorbent amount (0.1–10.0 g), temperature (10–50 °C), and operating time (5–90 min) were examined. Under wanted conditions, maximum removal efficiencies of 90.36%, 98.04%, and 97.86% were obtained with RU, FeU, and FeU@200°C, respectively. The equilibrium adsorption was found to match the Langmuir isotherm model based on the collected data. The maximum adsorption capacity of RU, FeU, and FeU@200°C was 6.09, 6.61, and 6.46 mg/g, severally. The arsenic adsorption onto RU, FeU, and FeU@200°C was acknowledged by the pseudo-second-order. Electrostatic interaction and surface complexation mechanisms are involved in arsenic adsorption. The Box-Behnken statistical experiment design method was applied to specify the impact of pH, temperature, and the amount of RU, FeU, and FeU@200°C on the percentage of arsenic removal. All of the results showed that RU, FeU, and FeU@200°C were eco-friendly, affordable, and easily procured that could be used for removing geogenic arsenic from well-waters.

Synergetic Effect of Organic Flocculant and Montmorillonite Clay on the Removal of Nano-CuO by Coagulation-Flocculation-Sedimentation Process.

The widespread usage of nano-copper oxide particles (nano-CuO) in several industrial products and applications raises concerns about their release into water bodies. Thus, their elimination from drinking water is essential to reduce the risk to human health. This work investigated the removal of nano-CuO from pure water and montmorillonite clay (MC) suspensions using poly aluminum ferric chloride (PAFC) as well as cationic polyacrylamide (PAM) by the coagulation-flocculation-sedimentation (C/F/S) process. Moreover, the PAFC and PAFC/PAM flocculation performance for various nano-CuO particles concentrations, dosages, pH, settling times and stirring speeds were also investigated. The findings showed that the removal of nano-CuO and turbidity in MC suspension were higher as compared to pure water. Moreover, the combined effect of PAFC/PAM on the elimination of nano-CuO and turbidity was also substantially better than the individual use of PAFC or PAM. The efficient removal of CuO was observed in the solution containing higher mass concentration in the order (10 mg/L > 2.5 mg/L > 1 mg/L) with an increased coagulant dose. The improved removal performance of nano-CuO was observed in a pH range of 7–11 under various water matrices. The C/F/S conditions of nano-CuO were further optimized by the Box–Behnken statistical experiment design and response surface methodology. The PAFC/PAM dose resulted in the maximum removal of nano-CuO (10 mg/L) in both pure water (>97%) and MC suspension (>99%). The results of particle monitoring and Fourier transform infrared of composite flocs revealed that the main removal mechanism of nano-CuO may be the combined effect of neutralization, complexation as well as adsorption.

Enhanced oral bioavailability of rutin by a self-emulsifying drug delivery system of an extract of calyces from Physalis peruviana

The aim of this study was to develop and optimize a self-emulsifying drug delivery system (SEDDS) containing an extract of calyces from Physalis peruviana with high mucus permeating properties to increase the bioavailability and the hypoglycemic activity of the active metabolites of the extract. The oil, surfactant, and co-solvent were selected based on solubility studies. The formulation was optimized using Box-Behnken statistical experimental design (BBD). Optimized conditions were Labrafac as oil 10% (w/w), Solutol HS 15 as surfactant 45% (w/w), propylene glycol as co-solvent 32% (w/w) and PDMSHEPMS 13% (w/w). The extract was loaded into SEDDS to 45% (w/w). The optimized SEDDS exhibited a mean droplet size of 19.5 nm, PDI of 0.20, and negative zeta potential. Furthermore, SEDDS permeating properties were investigated in porcine intestinal mucus using the Transwell® method. Extract-loaded SEDDS showed a 2.6-fold increase in mucus permeation compared to the unformulated extract. A pharmacokinetic study showed a nearly 6-fold increase in rutin oral bioavailability in comparison with the unformulated extract. Moreover, the hypoglycemic activity of the extract-loaded SEDDS was higher than that of the unformulated extract. These results indicate that incorporating an extract of calyces from P. peruviana into SEDDS is a promising strategy to improve the oral bioavailability of the active flavonoids in the extract and the hypoglycemic activity.

Evaluation of phenanthrene removal from soil washing effluent by activated carbon adsorption using response surface methodology

Soil washing is a promising technology for the remediation of polycyclic aromatic hydrocarbons (PAH)-contaminated sites, but surfactant needs to be recovered to reduce remediation cost and avoid secondary pollution. In this study, activated carbon (AC), prepared from waste walnut shells, was applied to the adsorptive removal of phenanthrene (PHE) from synthetic soil washing effluent with Tween 80 as a model surfactant. Box-Behnken statistical experiment design (BBD) and response surface methodology (RSM) were used to investigate the influence of AC dosage, Tween 80 concentration and adsorption time, and their potential interaction effect on PHE removal. A response surface model was established based on the BBD experimental results. The goodness of fit of the model was confirmed by determination coefficient, coefficient of variation (CV) and residuals analysis. The RSM model indicates that AC dosage or adsorption time had positive effect on PHE removal while Tween 80 concentration had negative effect. The interaction effect between AC dosage and Tween 80 concentration was significant but the other two interaction effects were not. The 3D response surface plots were developed based on the RSM equation. The RSM model was validated by an additional experiment and the obtained result of PHE removal was very close to the model prediction, indicating the RSM model can effectively predict the PHE removal from soil washing effluent with activated carbon adsorption.

Graphene oxide-iron modified clinoptilolite based composites for adsorption of arsenate and optimization using response surface methodology

In this study, graphene oxide and composites of graphene oxide-iron modified clinoptilolite were synthesized and used for arsenate removal from aqueous solution. All adsorbents were characterized using X-ray diffraction and specific surface area analysis. The specific surface areas of composites were found to be less than the iron modified clinoptilolite. The time required to reach equilibrium was determined as 3 hours for all adsorbents. The Box-Behnken statistical experiment design method was used to determine the effects of initial arsenate concentration, pH and the amount of adsorbent on the percent arsenate removal. Graphene oxide was not as effective as composites for arsenate adsorption from water. Arsenate adsorption on composites was showed good compatibility with the Freundlich isotherm. The maximum arsenate uptake was realized at pH 4 for graphene oxide and at pH 7 for composites. The maximum adsorption capacities obtained at the optimum points determined by using the Box-Behnken design method were calculated as 39.49, 117.98 and 124.64 µg.g−1 for graphene oxide and composites, respectively.

Optimization of Antimony Removal by Coagulation-Flocculation-Sedimentation Process Using Response Surface Methodology

Coprecipitation-adsorption plays a significant role during coagulation-flocculation-sedimentation (C/F/S) of antimony (Sb) in water. This work uses a Box–Behnken statistical experiment design (BBD) and response surface methodology (RSM) to investigate the effects of major operating variables such as initial Sb(III, V) concentration (100–1000 µg/L), ferric chloride (FC) dose (5–50 mg/L), and pH (4–10) on redox Sb species. Experimental data of Sb(III, V) removal were used to determine response function coefficients. The model response value (Sb removal) showed good agreement with the experimental results. FC showed promising coagulation behavior of both Sb species under optimum pH (6.5–7.5) due to its high affinity towards Sb species and low residual Fe concentration. However, a high dose of 50 mg/L of FC is required for the maximum (88–93%) removal of Sb(V), but also for the highest (92–98%) removal of low initial concentrations of Sb(III). Furthermore, BBD and RSM were found to be reliable and feasible for determining the optimum conditions for Sb removal from environmental water samples by a C/F/S process. This work may contribute to a better understanding and prediction of the C/F/S behavior of Sb(III, V) species in aqueous environments, to reduce potential risks to humans.

ABTS radical-based single reagent assay for simultaneous determination of biologically important thiols and disulfides

Both the total amount of biothiols and thiol/disulfide ratio are wellness indicators of oxidative balance that play an important role in antioxidant defense system. Oxidized biothiols in disulfide form cannot be determined by conventional ABTS assay due to the biphasic kinetic pattern of the reaction between biothiols and ABTS radical cation (ABTS•+), necessitating the initial reduction of disulfides to thiols prior to measurement. In this study, direct simultaneous determination of biothiols (RSH) and their disulfides (RSSR) by using a single reagent of ABTS•+ was achieved without preliminary chemical reduction. Thus, conventional problems of preliminary operations arising from direct borohydride reduction of disulfides to thiols, followed by formaldehyde removal of borohydride excess and complications caused by formaldehyde-thiol reactions were effectively overcome with the use of a single reagent (ABTS•+). Box-Behnken statistical experimental design was employed to specify the optimal incubation temperature and time as 60 °C and 60 min, respectively. The detection limits (LOD) of the proposed assay for biothiols were compared to those of the widely used DTNB (Ellman) reference assay known to be nonresponsive to disulfides, and were found to be much lower (4–70 times). The proposed biothiol assay was successfully applied to some pharmaceutical samples and synthetic serum without preliminary treatment, and the results were highly compatible with the HPLC findings. The proposed assay was demonstrated to have superior features such as simplicity, rapidity and higher sensitivity over the widely applied Ellman thiols assay.

Microwave Processing of Electrode Active Materials for the Recovery of Cobalt, Manganese, and Lithium

The limited lifespan, ever-growing demand, and significant lithium and cobalt content are responsible factors for the immediate recycling of discarded lithium-ion batteries. Discharged batteries were dismantled, segregated, and size reduced to recover cathode and anode material. The active cathode material comprises LiCoO2 (65.8%) and LiMn2O4 (34.2%) and was carbothermal reduced with recovered graphite in a microwave furnace followed by water leaching and magnetic separation. A Box Behnken statistical experimental design is used for process optimization. Both cobalt and manganese report to magnetic fraction, whereas graphite and lithium carbonate report to non-magnetic fraction and solution crystal respectively. The final product comprises of cobalt 73% and manganese of 14% with process yield of 36% and saturation magnetization of 76 emu/g.

Prevention of substrate and product inhibitions by using a dilution strategy during dark fermentative hydrogen production from molasses

Substrate and product inhibitions have a significant effect on dark fermentative hydrogen gas production. Particularly, rapid formation of volatile fatty acids leads to fast pH decreases shifting the metabolic pathway. Therefore, controlling volatile fatty acid accumulation has great importance in maintaining effective hydrogen production. In this context, a dilution strategy was applied to regulate volatile fatty acids levels within the desired concentration range. A three-factor Box-Behnken statistical experiment design was established to assess the effects of dilution time, dilution percentage and initial COD concentration on hydrogen formation yield and rate. Highest hydrogen yield (7.7 mL H2/mLreactor) and rate (21. 47 mL H2/h or 9.38 mmol/Lreactor.h) were achieved when 85 gCOD/L containing fermentation media was diluted with a percentage of 130 of the initial working volume at the 3rd hour of the fermentation period. Moreover, this strategy enabled to start fermentation with 55 g glucose/L.

Using Box–Behnken experimental design to optimize the degradation of Basic Blue 41 dye by Fenton reaction

Degradation of a Basic Blue 41 dye using Fenton reagent was examined at laboratory scale in batch experiments using Box–Behnken statistical experiment design. Dyestuff, hydrogen peroxide (H2O2) and ferrous ion (Fe2+) concentrations were selected as independent factors. On the other hand, color and chemical oxygen demand (COD) removal were considered as the response functions. The value of coefficient of determination (R2) for both color and chemical oxygen demand removal with values 0.98 and 0.99 shows the best agreement between predicted value and experimental values. Perturbation plots indicated that iron dosage has the most effect on both color and COD removal. Normalized plot of residuals also indicated that the models were adequate to predict for both responses. Color and COD removal increased with increasing H2O2 and Fe2+ concentrations up to a certain level. High concentrations of H2O2 and Fe2+ did not result in better removal of color and COD due to hydroxyl radical being gradually consumed by both oxidant and catalyst. Percent color removal was higher than COD removal indicating the production of colorless compounds. The second-order polynomial model revealed optimal process factor ratio. The ratio of H2O2/Fe2+/dyestuff which gives a complete color removal and 95% COD removal was found to be 1195 mg/L/90 mg/L/255 mg/L.

Decolorization of methylene blue using Fe(III)-citrate complex in a solar photo-Fenton process: impact of solar variability on process optimization.

This study investigates the solar photo-Fenton based decolorization of a cationic dye methylene blue (MB) at circumneutral pH conditions. Water-soluble Fe(III)-citrate complex was used as a source of Fe(II) during the reaction by ligand-to-metal charge transfer under solar irradiation, and consequently, for the production of hydroxyl radicals. Solar decolorization of methylene blue was studied in sunny as well as cloudy weather, and further optimized using response surface methodology and Box-Behnken statistical experimental design. In this model, Fe(III) dose, citrate ion dose, and initial pH of the solution were used as independent parameters, and percentage decolorization of MB was used as a response. Better decolorization of MB was observed in sunny weather as compared to cloudy weather. A particular combination of parameters, i.e. pH of 7, Fe(III) of 0.5 mM, and citrate ion concentration of 10 mM, was found to achieve 89.19% and 51.22% decolorization in sunny and in cloudy weather respectively, which were the optimum/near-optimum performances for these weather conditions. Hence the process initiated with these parameters may potentially achieve better performance than any other parameter combination in all weathers, although the absolute removal would still depend on incident solar irradiation.