Optimum conditions for testing N-nitrosamine formation potential (FP) through ozonation in wastewater samples

N-nitrosamines are potential carcinogens that are formed during disinfection by chlorination/chloramination or ozonation. In this study, the main objective was to optimize ozonation experimental conditions (pH and temperature) for the production of N-nitrosamines by using the CCD method in wastewater matrices. As the results, maximum NDMA FP_O3 (formation potential by ozonation) occurred at pH 8.96 and a temperature of 20.0 °C. Furthermore, attempts to reduce the concentrations of eight N-nitrosamines revealed that none was removed or reduced in concentration by ozonation using Milli-Q water for 2 h.     

Response surface methodological approach to optimize the coagulation-flocculation process in drinking water treatment

Performing jar tests often requires carrying out a time consuming iteration procedure to find out the right amount of chemical for coagulation-flocculation process in water treatment plants. Applying the response surface method (RSM) in jar tests as an alternative to the conventional methods was investigated in this study. The purpose is finding out the optimum combination of coagulant dose and pH with respect to the highest removal efficiency of turbidity and dissolved organic carbon (DOC). The results achieved using poly-aluminum chloride (PACl) were compared to those achieved using conventional coagulant such as alum. The quadratic models developed for the two responses (turbidity removal and DOC removal) indicated that the optimum conditions to be PACl concentration of 0.11 mM at pH 7.4 and alum concentration of 0.15 mM at pH 6.6. Compromising to simultaneously optimize the two responses resulted in 91.4% turbidity removal and 31.2% DOC removal using PACl whereas 86.3% turbidity and 34.3% DOC were removed using alum. Confirmation of experimental results was found to be close to the prediction derived from the models. This demonstrates the benefits of the approach based on the RSM in achieving good predictions while minimizing the number of required experiments.     

Response Surface Optimization of the Critical Media Components for the Production of Surfactin

Optimization of the fermentation media for maximization of surfactin production was carried out. The carbon source (glucose), the nitrogen source (ammonium nitrate) and the mineral salts ferrous and manganous sulphates were the critical components of the medium optimized. A 2⁴ full factorial central composite experimental design followed by multi-stage Monte-Carlo optimization was used in the design of experiments and in the analysis of results. This procedure limited the number of actual experiments performed while allowing for possible interactions between the four components. The optimum values for the tested variables for the maximal production of surfactin were (in g dm⁻³): glucose = 36·5; NH₄NO₃ = 4·5; FeSO₄ = 4×10⁻³ and MnSO₄ = 27·5 ×10⁻². Relative surfactant concentrations were expressed as the reciprocal of the critical micelle concentration (CMC⁻¹) and the maximum predicted yield of surfactin in terms of CMC⁻¹ was 45·5. © 1997 SCI.     

维生素C乳酸酯酶催化合成的响应曲面分析

以脂肪酶Novozym 435催化维生素C和乳酸乙酯转酯合成维生素C乳酸酯。采用基于四因素五水平的中心组合设计实验的响应曲面法,分析了温度(30~70℃)、酶量(10~30 mg)、维生素C质量浓度(9.36~28.07g/L)和反应时间(24~72 h)以及它们的交互作用对维生素C乳酸酯产率的影响。获得的最佳实验条件为:温度50℃,维生素C的质量浓度18.71 g/L,脂肪酶质量20 mg和反应时间48 h。在最佳条件下,维生素C乳酸酯的预计产率为71.20%,与实际产率71.12%符合较好。     

Application of Response Surface Methodology for Optimization of Bromelain Extraction in Aqueous Two-Phase System

Extraction of bromelain from pineapple fruit in an aqueous two phase system (ATPS) composed of polyethylene glycol (PEG) 1500 and potassium phosphate has been studied using response surface methodology. The various process variables such as PEG, potassium phosphate and NaCl concentration, and pH were optimized using a central composite rotatable design (CCRD) of response surface methodology (RSM) based on the partition coefficient, % yield, and purification factor of an enzyme. An optimized ATPS composed of 14% (w/w) PEG 1500, 17.66% (w/w) potassium phosphate and 1 mM sodium chloride at pH 7.5 was used to purify bromelain from a pineapple fruit. With this system, a maximum enzyme partition coefficient of 12.62 and %yield of 90.33 in the top PEG-rich phase with a purification factor of 2.4 was predicted. The enzyme partition coefficient, % yield, and purification factor obtained from experimentation are 12.22, 89.65, and 2.8, respectively, in the top PEG phase. The response model is validated by the closeness between the predicted and experimental results.     

An optimization study on microwave irradiated decomposition of phenol in the presence of H2O2

BACKGROUND Removal of phenol from industrial waste waters involves basic techniques namely extraction, biodegradation, photocatalytic degradation, etc. Among the available processes, the oxidation of phenols using H₂O₂ is a suitable alternative because of low cost and high oxidizing power. The application of an oxidation process for the decomposition of stable organic compounds in waste water leads to the total degradation of the compounds rather than transferring from one form to another. Since oxidation using Fenton's reagent is more dependent on pH, in this present work it was proposed to use H₂O₂ coupled with microwave irradiation. The effects of initial phenol concentration, microwave power and the irradiation time on the amount of decomposition were studied. RESULTS: In the present work experiments were conducted to estimate the percentage degradation of phenol for different initial concentrations of phenol (100, 200, 300, 400 and 500 mg L^?1), microwave power input (180, 360, 540, 720 and 900 W) for different irradiation times. The kinetics of the degradation process were examined through experimental data and the decomposition rate follows first‐order kinetics. Response surface methodology (RSM) was employed to optimize the design parameters for the present process. The interaction effect between the variables and the effect of interaction on to the responses (percentage decomposition of phenol) of the process was analysed and discussed in detail. The optimum values for the design parameters of the process were evaluated (initial phenol concentration 300 mg L^?1, microwave power output 668 W, and microwave irradiation time 60 s, giving phenol degradation 82.39%) through RSM by differential approximation, and were confirmed by experiment. CONCLUSION: The decomposition of phenol was carried out using H₂O₂ coupled with microwave irradiation for different initial phenol concentrations, microwave power input and irradiation times. The phenol degradation process follows first‐order kinetics. Optimization of the process was carried out through RSM by forming a design matrix using CCD. The optimized conditions were validated using experiments. The information is of value for the scale up of the oxidation process for the removal of phenol from wastewater. Copyright © 2008 Society of Chemical Industry     

Utilization of response surface methodology to optimize the culture media for the production of rhamnolipids by Pseudomonas aeruginosa AT10

Pseudomonas aeruginosa AT10 produced a mixture of surface‐active rhamnolipids when cultivated on mineral medium with waste free fatty acids as carbon source. The development of the production process to an industrial scale included the design of the culture medium. A 2⁴ full factorial, central composite rotational design and response surface modelling method (RSM) was used to enhance rhamnolipid production by Pseudomonas aeruginosa AT10. The components that are critical for the process medium were the carbon source, the nitrogen source (NaNO₃), the phosphate content (K₂ HPO₄/KH₂PO₄ 2:1) and the iron content (FeSO₄·7H₂O). Two responses were measured, biomass and rhamnolipid production. The maximum biomass obtained was 12.06 g dm^?3 DCW, when the medium contained 50 g dm^?3 carbon source, 9 g dm^?3 NaNO₃, 7 g dm^?3 phosphate and 13.7 mg dm^?3 FeSO₄·7H₂O. The maximum concentration of rhamnolipid, 18.7 g dm^?3, was attained in medium that contained 50 g dm^?3 carbon source, 4.6 g dm^?3 NaNO₃, 1 g dm^?3 phosphate and 7.4 mg dm^?3 FeSO₄·7H₂O. © 2002 Society of Chemical Industry     

Experiment research on mix design and early mechanical performance of alkali-activated slag using response surface methodology (RSM)

To enhance the quality of alkali-activated slag (AAS) materials, scientific and efficient mix design method is preferred. This paper presents an optimization of AAS materials using Response Surface Methodology (RSM). Three factors related to early strength such as modulus (n), concentration of alkali activator (CAA) and liquid–solid ratio (LSR) were investigated. Specimens with different mix ratios were prepared based on RSM design. The early mechanical performance was assessed, after 2 or 3 h of curing. Then response surface models were established and the effect law of each factor was systemically analyzed. The result shows that both n and CAA have a significant effect on the early strength, while LSR affects slightly. By adjusting the mix design parameters, the early performance of AAS can be effectively improved. This study verifies that RSM is efficient in the preparation of AAS and it can control the early strength of AAS accurately.     

A comparative study on the performance of different advanced oxidation processes (UV/O3/H2O2) treating linear alkyl benzene (LAB) production plant's wastewater

A detailed investigation on photooxidation of linear alkyl benzene (LAB) industrial wastewater is presented in this study. The process analysis was performed by varying four significant independent variables including two numerical factors (initial pH (3–11) and initial H₂O₂ concentration (0–20 mM)) and two categorical factors (UV irradiation and ozonation). The experiments were conducted based on a central composite design (CCD) and analyzed using response surface methodology (RSM). To assess the process performance, two parameters viz. TCOD removal efficiency and BOD₅/COD were measured throughout the experiments. A maximum reduction in TCOD was 58, 53, 51, and 49%, respectively for UV/H₂O₂/O₃, H₂O₂/O₃, UV/O₃ and UV/H₂O₂ processes at the optimum conditions (initial pH of 7, initial H₂O₂ concentration of 100 mM, and reaction time of 180 min). A considerable increase in BOD₅/COD ratio was obtained in the combined processes (0.46, 0.51, 0.53, and 0.55 for UV/H₂O₂, UV/O₃, H₂O₂/O₃ and UV/H₂O₂/O₃, respectively) compared to the single oxidant process (0.35). The results showed that mineralization of the LAB industrial wastewater in neutral pH is more favored than in acidic and basic pH. Gas chromatography–mass spectrometry (GC–MS) was applied to show the fate of organic compounds. In conclusion, the photooxidation process (UV/H₂O₂/O₃, H₂O₂/O₃, UV/O₃ and UV/H₂O₂) could be an appropriate pretreatment method prior to a biological treatment process.     

煤矸石浸渣制备白炭黑工艺优化及性能分析

为实现煤矸石固废的资源化高效综合利用,以煤矸石浸取Al、Fe、Ti等元素后的浸渣为原料,利用煤矸石浸渣-硫酸钠干法制备出水玻璃,然后采用碳化法制备白炭黑产品。借助邻苯二甲酸二丁酯(DBP)测定产品的吸油值,并通过比表面积测定(BET)、X射线衍射分析(XRD)、红外光谱分析(FTIR)、扫描电镜(SEM)以及热重-差热分析(TG-DSC)等对白炭黑进行了结构表征与性能测试;考察了水玻璃质量分数、反应温度、Na2CO3质量浓度、CO2通入速率对白炭黑DBP吸油值和比表面积的影响,在单因素实验基础上以比表面积为主要指标,利用正交实验设计与响应曲面法联合设计优化了制备工艺。结果表明:在水玻璃质量分数为10%、反应温度为77℃、CO2通入速率为147 mL/min、Na2CO3质量浓度为3 g/L条件下,实验结果与响应曲面预测结果基本吻合,制得比表面积为267.33 m2/g、DBP吸油值为2.77 mL/g的白炭黑产品。产品性能分析表明,所制白炭黑为由非晶态物质组成的无定形态产品,产品中基本无杂质出现,纯度较高,微观形貌较好,符合HG/T3061—2009中A类产品的要求。     

Adsorptive removal of fluoride from water by activated carbon derived from CaCl2-modified Crocus sativus leaves: Equilibrium adsorption isotherms,optimization, and influence of anions

A central composite design using response surface methodology was applied for the experimental design and optimization of fluoride adsorption on an activated carbon derived from calcium chloride-modified Crocus sativus leaves (AC-CMCSL). Fluoride removal efficiency as function of independent variables, such as initial fluoride concentration, pH, adsorbent dose, and time has been investigated. The maximum percentage removal of fluoride at optimum conditions (initial fluoride concentration?=?6.5?mg?L^?1, pH?=?4.5, adsorbent dose?=?15?g?L^?1 and time?=?70?min) was 85.43%. By comparing adsorption isotherm, the Freundlich model provided the best correlation (R²?=?0.99) for the adsorption of fluoride on AC-CMCSL. The maximum adsorption capacity from the Langmuir model (q_max) was 2.01?mg?g^?1. The influence of the co-existing anions on fluoride adsorption was in the following order: PO₄^3??>?SO₄^2??>?Cl^??>?NO₃^?. The results of the present study showed that activated carbon derived from the leaves of calcium chloride-modified Crocus sativus has a good potential for fluoride removal from aqueous solution.     

Determining the Best Composition of a Ni–Fe/Al2O3 Catalyst used for the CO2 Hydrogenation Reaction by Applying Response Surface Methodology

Response surface methodology (RSM) with central composite design (CCD) was applied to determine the composition of an alumina-supported nickel-iron (Ni–Fe) catalyst that provided the highest CH₄ yield for the CO₂ hydrogenation reaction. This involved synthesis of alumina-supported Ni–Fe catalysts of compositions that were specified by CCD. The catalysts were then tested for the CO₂ hydrogenation reaction, and a model equation was developed that related the catalyst composition to the CH₄ yield. The model equation was validated by analysis of variance, and it was found to adequately represent the experimental data. The model equation predicted that the alumina-supported Ni–Fe catalyst containing 32.8% Ni and 7.7% Fe would provide the highest CH₄ yield. A catalyst with this specific composition and the same metal deposition method and two other catalysts of the same composition but different metal deposition metal were also synthesized, characterized, and tested for the CO₂ hydrogenation reaction. The three catalysts did show activities similar to those predicted by the model equation. Furthermore, characterization and reaction studies revealed that the three catalysts were similar, suggesting that the metal deposition methods do not have any effect on the catalytic activity.     

Photocatalytic oxidation of treated municipal wastewaters for the removal of phenolic compounds: optimization and modeling using response surface methodology (RSM) and artificial neural networks (ANNs)

BACKGROUND: TiO₂ heterogeneous photocatalysis should be optimized before application for the removal of pollutants in treated wastewaters. The response surface methodology (RSM) and artificial neural networks (ANNs) were applied to model and optimize the photocatalytic degradation of total phenolic (TPh) compounds in real secondary and tertiary treated municipal wastewaters. RESULTS: RSM was developed by considering a central composite design (CCD) with three input variables, i.e. TiO₂ mass, initial concentration of TPh and irradiation intensity. At the same time a feed‐forward multilayered perceptron ANN trained using back propagation algorithms was used and compared with RSM. Under the optimum conditions established in experiments ([TPh]₀ = 3 mg L^?1; [TiO₂] = 300 mg L^?1; I = 600 W m^?2) the degradation for both TPh and total organic carbon (TOC) followed pseudo‐first‐order kinetic model. Complete degradation of TPh took place in 180 min and reduction of TOC reached 80%. A significant abatement of the overall toxicity was accomplished as revealed by Microtox bioassay. CONCLUSIONS: It was found that the variables considered have important effects on TPh removal efficiency. The results demonstrated that the use of experimental design strategy is indispensable for successful investigation and adequate modeling of the process and that ANNs gave better modelling capability than RSM. Copyright © 2012 Society of Chemical Industry     

Development and optimization of cultured goat cream butter

A central composite design 2²+star based on response surface methodology was used for development and optimization of a cultured goat cream butter formulation (cultured). The goat milk cream was inoculated with freeze-dried mesophilic aromatic lactic cultures and showed an increase in acidity and a aromatic lactic cultures and showed an increase in acidity and a decrease in lactose content when the concentration of lactic cultures was increased. An optimized temperature of 28°C was chosen for fast acid production in the goat milk cream. The lactic culture concentration significantly affected flavor, sensory texture, and overall quality, but the fermentation process were an inoculum dosage of 8.8 U/100 L and a fermentation time of 7 h at 28°C. This cultured formulation achieved optimal sensory quality in the attributes appearance, flavor, texture, and overall quality. At refrigerator temperature (4°C) the cultured formulation behaved as a solid and lacked spreadability, whereas it had ideal spreadability at 15°C when the solid fat content (SFC) was around 18.0%. At room temperature (18–25°C) the SFC was between 11 and 8%, respectively.     

Experimental and modeling study for the removal of formic acid through bulk ionic liquid membrane using response surface methodology

Abstract

In this study, formic acid removal from its aqueous solutions through bulk ionic liquid membrane (BILM) was investigated. Tributyl phosphate (TBP) as a carrier in imidazolium-based ionic liquids was used. D-optimal design based on response surface methodology has been applied to investigate the effect of various operating factors. Initial formic acid concentration, TBP concentration, and NaOH concentration were selected as numerical factors, and ionic liquid type was chosen as a categorical factor. The model equations were obtained to determine BILM process behavior. The removal efficiencies, represented by the extraction and stripping efficiencies, were calculated from the experimental data. The highest removal efficiencies were determined at higher concentration values of TBP and NaOH. All ionic liquids studied in this study had good transport selectivity for the removal of formic acid. The design study showed that BILM is an effective method for the removal of formic acid from the water.     

盾叶薯蓣中水解原位提取薯蓣皂甙元

利用响应面优化法对盾叶薯蓣块茎中薯蓣皂甙元水解原位提取进行研究.实验采用CC0428中心组合设计考察了影响薯蓣皂甙元提取效果的四个重要因素:硫酸浓度、异丙醇浓度、水解时间和水解液用量.结果表明盾叶薯蓣块茎中薯蓣皂甙元水解原位提取最佳条件为1.50 g盾叶薯蓣块茎干粉加入25 mL 1.25 mol·L-1硫酸-70%异丙醇溶液加热回流水解提取7.5 h,薯蓣皂甙元理论产率为0.7220%; 实际产率为0.7034%.与传统盐酸水解法相比薯蓣皂甙元产率提高68%.提取的产物通过熔点测定、红外光谱和质谱分析,表明与薯蓣皂甙元标准品基本一致.水解原位提取法具有简便、高效特点.     

Bi_(1/2)Na_(1/2)TiO_3-BaTiO_3系无铅压电陶瓷制备工艺的优化及其结构分析

借助正交试验设计,通过对无铅压电陶瓷压电、介电性能的测试,研究了BaTiO3含量、预烧温度、烧结温度及保温时间对(1-x)(B i1/2Na1/2)TiO3xBaTiO3(简写为BNBT 100x)陶瓷性能的影响。研究结果表明制备BNBT系陶瓷的最优化工艺条件为:BaTiO3摩尔分数x=0.06、预烧温度850℃、烧结温度1 130℃、保温时间2 h。通过XRD分析了BNBT系压电陶瓷的晶体结构类型、晶胞参数及晶格畸变随着BaTiO3摩尔分数的变化,确定了该体系的三方四方的准同型相界在x=0.06~0.08之间。     

Retention Rate Enhancement of Antioxidant and Cyaniding 3-O-Glucoside Components of the Reconstituted Product from Spray-Dried Black Raspberry Juice by Optimizing Process Parameters

The effects of four operating parameters involved in the spray-drying process, including air inlet temperature (120–150°C), air flow rate (3.5–5.0 m³/h), feed flow rate (2–10 mL/min), and aspirator rate (50–70 m³/h), to produce black raspberry juice powders with the highest retention rate of healthy functional components were optimized using a response surface design. Second-order polynomial models with high R ² (0.955–0.972) values were developed using multiple linear regression analysis. Results showed that the most significant (p < 0.05) process conditions that affected the antioxidant activity and cyanidin-3-O-glucoside content (C3GLU) of powders respectively were the quadratic effects of air inlet temperature and air flow rate and quadratic terms of air and feed flow rates. Laser diffraction particle size analysis and scanning electron microscopy were used to relate the microstructure and quality features. The lowest EC₅₀ (0.0060 mL juice/g 1,1-diphenyl-2-picrylhydrazyl [DPPH]) and the highest C3GLU (4.721 mg/100 mL) values were achieved at an inlet temperature of 120.0°C, air flow rate of 4.20 m³/h, feed flow rate of 8.65 mL/min, and aspirator rate of 55.87 m³/h.