Studies on biodegradation of phenol using response surface methodology

Biodegradation of phenol was studied using Pseudomonas pictorum (NCIM 2077) immobilized on alginate and activated carbon – alginate beads. Control experiments were also performed using free cells and non‐inoculated activated carbon – alginate beads. The entrapped alginate and activated carbon – alginate beads suffer from a concentration gradient for oxygen in the interior of the beads and hence free cells showed better degradation at lower concentrations of phenol. The results on entrapped alginate beads were modeled using response surface methodology which determines the dependency of the maximum percentage of phenol degraded as a function of the independent variables, namely initial phenol concentration, initial pH, temperature, and diameter of the immobilized beads. The predicted values are in close agreement with the experimental values with the coefficient of correlation equal to 0.9999 and 0.9993 for both P pictorum – alginate beads and activated carbon – P pictorum – alginate beads respectively. © 2002 Society of Chemical Industry     

Fabrication of basalt embedded composite fiber membrane using electrospinning method and response surface methodology

In this study, a novel basalt embedded fiber membranes was prepared by the electrospinning method. The effects of the feed rate, voltage, tip to collector distance, and the basalt content on the prepared composite fiber membranes were investigated and optimized using the response surface method. Four models were built to compare the fibers in terms of deionized water flux (DWF), activated sludge flux, chemical oxygen demand (COD) removal, and porosity of fiber membranes. All the developed models were significant and adequately precise. The maximum flux of DWF was obtained when the voltage was 17.25 kV, the tip to collector distance of 19 cm, and a basalt content in polymer of 1.25%. COD removal decreased at higher voltage values as the feed rate increased. The porosity, pore size, and the contact angle values decreased for basalt embedded fiber membrane. The increases in the basalt percentage in polymer increased the hydrophilicity of the fiber. The flux decline for the basalt embedded fiber membrane was compared with the pristine fiber membrane. The permeate fluxes of pristine and basalt embedded fiber membranes were 42.3 and 59.6 L/m²/h, respectively. The biofouling performances of pristine and basalt embedded fiber membranes were also examined. Irreversible fouling decreased from 42.9% to 8.0%, and reversible fouling increased from 56.5% to 91.1% after modification of the membrane with basalt powder. Scanning electron microscopy with energy dispersive X-ray analysis (SEM–EDX) analysis showed that basalt powder was successfully embedded into polyether sulfone polymer.     

Optimization of spark plasma sintering parameters of Si3N4-SiC composite using response surface methodology (RSM)

The Si₃N₄-SiC micro-nano composites were fabricated via the spark plasma sintering method using MgSiN₂ as an additive. Response surface methodology and central composite design were applied to optimize the spark plasma sintering process for the fabrication of Si₃N₄-SiC/MgSiN₂ with improved density. The relation between the three parameters of sintering including temperature, pressure, and holding time was modeled and the optimized parameters were obtained. The best sintering results obtained for the sintering temperature, holding time, and pressure are 1700 °C, 487 s, and 49 MPa, respectively. The addition of MgSiN₂ as an additive and SiC as a secondary phase were also investigated in the present work. The Si₃N₄−5 vol% SiC composite exhibited high hardness (19 GPa) and fracture toughness values (6.5 MPa m^1/2) at room temperature.     

Optimization of rotating-jet electrospinning process using response surface methodology

Rotating-jet electrospinning method is one of the efficient techniques for producing aligned nanofibers. This paper reports an accurate investigation on the influence of collector diameter (CD), voltage, polymer concentration (PC), and insulator length (IL) of spinneret on the degree of fiber alignment (DFA), production rate of fiber, and fiber diameter. The polymer solution was a mixture of polyacrylonitrile and N,N-dimethylformamide. The ranges of independent variables were 20–50 cm for CD, 10–22 kV for voltage, 13–19 wt% for PC, and 0.5–3 cm for IL. To minimize the number of required experiments for a complete evaluation, response surface methodology (RSM) and central composite rotatable design were applied by means of Expert Design Software. After defining the upper and lower bounds of the above independent variables in the software, 30 unique experiments were delivered. The recommended operating conditions by the software were exactly applied in the laboratory and the corresponding values for the DFA, production rate, and fiber diameter were measured. The nanofiber morphology was examined by scanning electron microscopy (SEM). By applying the least-squares method in the DX7.0.0 software, well-fitting polynomial correlations to the experimental results were obtained, and using these correlations, the influence of independent variables and responses was comprehensively studied. Finally, the best values of independent variables for optimizing the responses were determined using RSM.     

Optimization of the n-hexane isomerization process using response surface methodology

Isomerization reactions on commercial zirconium sulfate catalyst are investigated in order to determine influence of hydrogen/feed ratio, space velocity and temperature on n-hexane conversion. Investigated range of inlet parameters includes values that are applied in the industrial practice of the isomerization process. Box–Behnken experimental design was carried out in order to optimize n-hexane isomerization process. Statistical analysis of experimental data was performed to obtain second order polynomial model and the optimum conditions were determined: hydrogen/feed ratio of 6, space velocity of 2 h⁻¹ and temperature of 170 °C. At optimum conditions conversion of n-hexane was 70 wt.%. In addition, temperature dependency of product composition was investigated at optimum values of hydrogen/feed ratio and space velocity. Obtained results show that methylpentanes greatly depend on temperature, unlike dimethylbutanes, in the studied range from 130 to 170 °C. Isomer that was produced in highest quantities was 2-methylpentane, while 3-methylpentane forms in somewhat smaller amounts. 2,2- and 2,3-dimethylbutanes, which contribute the most to the octane number value, are formed in relatively small quantities, amounting to less than 10 wt.% of the total amount of isomers formed.     

响应面法优化苦参碱粗品的结晶纯化过程

通过Box-Behnken试验设计,系统地考察了料液比、温度及结晶时间3个因素对苦参碱结晶收率的影响,并运用响应面法对建立的二次回归模型进行了综合分析。结果表明,当料液比为1∶28.78、温度为59.19℃、时间为30min时,苦参碱的结晶收率最大,其值为97.16%。     

Optimization of sulfamethoxazole degradation by TiO2/hydroxyapatite composite under ultraviolet irradiation using response surface methodology

A titanium dioxide/hydroxyapatite/ultraviolet (TiO₂/HAP/UV-A) system was used to remove sulfamethoxazole (SMX) from water in a second-order response surface methodology (RSM) experiment with a three-level Box-Behnken design (BBD) for optimization. The effects of both the primary and secondary interaction effects of three photocatalytic reaction variables were examined: the concentration of SMX (X₁), dose of TiO₂/HAP composite (X₂), and UV intensity (X₃). The UV intensity and TiO₂/HAP dose significantly influence the SMX and total organic carbon (TOC) removal (p<0.001). However, the SMX and TOC removal are enhanced with increasing TiO₂/HAP dose up to certain levels, and further increases in the TiO₂/HAP dose result in adverse effects due to hydroxyl radical scavenging at higher catalyst concentrations. Complete removal of SMX was achieved upon UV-A irradiation for 180min. Under optimal conditions, 51.2% of the TOC was removed, indicating the formation of intermediate products during SMX degradation. The optimal ratio of SMX (mg L^?1) to TiO₂/HAP (g L^?1) to UV (W/L) was 5.4145 mg L^?1 to 1.4351 g L^?1 to 18W for both SMX and TOC removal. By comparison with actual applications, the experimental results were found to be in good agreement with the model’s predictions, with mean results for SMX and TOC removal of 99.89% and 51.01%, respectively.     

Optimization of microwave-assisted synthesis of cyclodextrin nanosponges using response surface methodology

The reaction of polymerization of cyclodextrins with suitable polyfunctional agents leads to highly cross linked porous structures, referred to as cyclodextrin nanosponges. The conventional heating approach for the synthesis of nanosponges can lead to nonuniform reaction conditions caused by sharp thermal gradients in the bulk solution. In this work, we present a facile method for the synthesis of cyclodextrin nanosponges by microwave irradiation with significant reduction in reaction time. Response surface methodology and Box–Behnken design were used for the optimization of the process parameters including microwave power level (A), reaction time (B) and stirring speed (C). Two dependent variables practical yield and particle size were measured as responses. Mathematical equations and response surface plots were used to relate the dependent variables with independent variables. The optimization model predicted a yield of 96.5287 % and particle size of about 152.355 nm with A, B and C levels of 508.22, 83.55 and 1,471.55 respectively. The observed responses of the optimized process were in close agreement with the predicted values. Three confirmation batches of cyclodextrin nanosponges were synthesized under optimized conditions. The Fourier transformed infrared spectra of nanosponges showed a characteristic peak of the carbonate group at around 1,750 cm^?1 which confirms the formation of nanosponges. TGA revealed the stability of obtained nanosponges up to 325 °C. The nanosponges obtained by microwave irradiation exhibited a higher degree of crystallinity. Dimension of the crystal lattice was found to be equal to 0.70 nm. TEM image confirmed the spherical shape and the particle size range of about 153 nm. Compared to conventional heating method, microwave method resulted in four folds reduction in reaction time and provided with particles of homogeneous size distribution and uniform crystallinity.     

响应面法优化微波辅助合成中碳链甘油三酯工艺

以对甲苯磺酸为催化剂,在微波环境下合成辛酸癸酸甘油三酯,并利用响应面法优化辛酸癸酸甘油三酯的合成过程条件。首先,通过单因素灵敏度分析法对催化剂的选择、酸/醇摩尔比、反应温度、微波功率、催化剂用量、反应时间6个因素进行实验考察,确定了酸/醇摩尔比、反应温度、催化剂用量3个关键因素的优化值及取值范围。采用中心组合设计原则对3个关键因素进行实验设计。以产品羟值为响应值,基于响应实验结果,利用响应面法对实验结果进行了方程回归,得到3个关键因素与响应值的二次关联模型。通过方差分析和平行实验,证明该模型准确可用。确定了中碳链甘油三酯（MCTs）最佳合成条件为：酸/醇摩尔比为3.33：1,反应温度为190℃,催化剂用量为甘油质量的4.30%,微波功率为500 W,反应时间为3 h,得到产品羟值为1.12 mg KOH·g^-1,酯化率高达99.7%,与理论预测值基本相符。与传统加热方式对比,微波辅助合成MCT大大缩短了反应时间。测定了精制提纯后MCT产品的各项物化性能指标,均已达到企业标准。通过红外光谱表征和GC/MS进一步表征产物结构和混合物油脂的组成,甘油三酯得率达到95.7%。     

响应面法优化水滑石吸附剂改性工艺

采用(NH4)2SO4对镁铝水滑石(MgAl-LDH)进行表面改性,制备改性镁铝水滑石吸附剂(ALDH)。应用响应面法对改性工艺进行优化,采用Design-Expert 8.0软件,设计3因素3水平的响应面分析方法,得到最优改性工艺参数。在温度60℃,(NH4)2SO4浓度18%和液固比0.15(mL/mg)的优化条件下改性4 h,得到的ALDH对Pb(II)吸附率为91.7%,非常接近预测值。     

响应面法优化凹凸棒土-CoFe2O4磁性复合材料的制备工艺

针对粉末状凹凸棒土在实际应用中难以固液分离的问题,在其表面负载CoFe_2O_4磁性颗粒,以单宁酸吸附量作为指标,借助响应面法优化了凹凸棒土-CoFe_2O_4磁性复合材料(ACMC)的制备工艺。结果表明,各因素对吸附量的影响程度顺序为:CoFe_2O_4与凹凸棒土质量比反应时间 pH值反应温度,最佳制备工艺条件是CoFe_2O_4与凹凸棒土质量比为1.07, pH值为11.66,反应温度为74.11℃,反应时间为4 h。所制备出的最优ACMC对单宁酸的吸附量可达140.54 mg/g,与系统预测值(143.96 mg/g)接近,说明响应面法优化结果可靠。     

响应面法优化煤焦油加氢脱氮工艺

在小型固定床加氢装置上,研究煤焦油加氢脱氮工艺过程各参数对脱氮效果的影响。通过单因素考察和响应面分析法得到了加氢脱氮的优化工艺条件为:反应温度704.4K,反应压力13.48MPa,氢油体积比1600︰1,液体体积空速0.20h-1,产品氮含量为90～100μg/g。由于煤焦油的氮含量较高,要达到较好的加氢脱氮效果必须在高温、高压和低空速下进行。研究结果对煤焦油加氢改质工艺的深入研究提供了一定的理论基础和参考。     

Optimization and characteristics of preparing chitosan microspheres using response surface methodology

In this study, response surface methodology (RSM) was employed to optimize preparation of chitosan microspheres (CMs). Firstly, Plackett–Burman design (PBD) was applied to screen out the factors, which influence preparation of CMs significantly. The results showed that the concentration of chitosan and acetic acid as well as the volume of toluene were the key factors. Then, steepest ascent experiment and Box–Behnken design were introduced to optimize the levels of the key factors. As a result, the appropriate conditions of preparing CMs were chosen as follows: 2% (w/v) chitosan, 1.7% (v/v) acetic acid, 7 mL span‐80, 488 mL toluene, 1100 rpm, 60 min (emulsification time), 10 mL formaldehyde, and 60 min (crosslinking time). Also, the morphology, size particle, and FTIR spectra of CMs were studied by scanning electron microscopy, small angle laser light scattering, and FTIR spectrometer. Results showed that CMs had quite smooth surface spherical and sharp size distribution, which indicated that the CMs were successfully prepared by W/O emulsification crosslinking method using RSM. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Optimization of oil extraction from locust bean using response surface methodology

Optimization of oil extraction from locust beans (Parkia biglobosa) using central composite rotatable design of RSM was carried out. Independent variables were roasting temperature (90, 100, 110, 120, 130°C) and roasting duration (5, 10 15, 20, 25 min), while the responses were oil yield (OY), free fatty acid (FFA), color (CO), stability, anisidine value (AV), and specific gravity (SG). Data obtained from this study were analyzed using ANOVA and regression analysis. OY, FFA, CO, oil stability, AV, and SG of the oil ranged between (19.0–22.5%), (0.65–3.1%), (37.9–199.9 mg/L), (3.6–6.4%), (11.4–59.9 mg/L), (0.7–0.9), respectively. Roasting conditions significantly influenced all dependent variables at p<0.05. Coefficients of determination (R²) of the generated models ranged from 0.49 to 0.98. Optimum roasting condition was 108°C for 10 min. This gave 22.3% OY, 1.7% FFA, 54.9 mg/L CO, 4.1% stability, 16.5 mg/L AV, and 0.9 SG. Desirability of 0.8 was obtained for optimum conditions. Practical applications: Generally, African locust bean is fermented to give condiment. It has not been used for commercial oil production despite its richness in oil, but soybean with a similar oil content of about 18–20% has been used both for condiment and commercial oil production. Research into the potential of locust bean as a source of edible oil is desirable. Roasting is among pre‐treatment methods employed in vegetable oil industry. Information on degree of influence of these parameters on quantity and quality of oil recovered oil from African locust benefits both entrepreneur and researchers. Also, the developed mathematical expression for OY, FFA, CO, oil stability, AV, and SG, as influenced by roasting temperature and duration is an effective tool in predicting these parameters. The research output has both immediate and potential application.     

响应面法优化微生物诱导碳酸钙沉积培养基

通过响应面法对微生物诱导CaCO3沉积的培养基组分进行优化。结果表明,最适宜培养基配方为葡萄糖30g/L、大豆蛋白胨10g/L、尿素50g/L、硝酸钙0.5mol/L、吐温80体积分数0.05%以及氯化镍250μmol/L。葡萄糖浓度和尿素浓度、葡萄糖浓度和硝酸钙浓度、葡萄糖浓度和吐温浓度、硝酸钙浓度和吐温浓度以及尿素浓度和氯化镍浓度,对微生物诱导CaCO3沉淀量的影响有着比较显著的双因子效应。沉淀物CaCO3含有少量有机质,形成方解石型或方解石和球霰石混合晶型的CaCO3,其形貌和堆积密度随外界条件改变而不同。     

Optimization and analysis of nickel adsorption on microwave irradiated rice husk using response surface methodology (RSM)

BACKGROUND: The removal of heavy metals using adsorption techniques with low cost biosorbents is being extensively investigated. The improved adsorption is essentially due to the pores present in the adsorbent. One way of improving the porosity of the material is by irradiation of the precursor using microwaves. In the present study, the adsorption characteristics of nickel onto microwave‐irradiated rice husks were studied and the process variables were optimized through response surface methodology (RSM). RESULT: The adsorption of nickel onto microwave‐irradiated rice husk (MIRH) was found to be better than that of the raw rice husk (RRH). The kinetics of the adsorption of Ni(II) from aqueous solution onto MIRH was found to follow a pseudo‐second‐order model. Thermodynamic parameters such as standard Gibbs free energy (ΔG°), standard enthalpy (ΔH°), and standard entropy (ΔS°) were also evaluated. The thermodynamics of Ni(II) adsorption onto MIRH indicates that it is spontaneous and endothermic in nature. The response surface methodology (RSM) was employed to optimize the design parameters for the present process. CONCLUSION: Microwave‐irradiated rice husk was found to be a suitable adsorbent for the removal of nickel(II) ions from aqueous solutions. The adsorption capacity of the rice husk was found to be 1.17 mg g^?1. The optimized parameters for the current process were found as follows: adsorbent loading 2.8 g (100 mL)^?1; Initial adsorbate concentration 6 mg L^?1; adsorption time 210 min.; and adsorption temperature 35 °C. Copyright © 2008 Society of Chemical Industry     

应用响应曲面优化交联淀粉微球的合成工艺

为了优化采用反相悬浮法合成的交联淀粉微球(CSM)的工艺,采用响应曲面法(RSM)分析了交联剂质量分数、反应温度和引发剂浓度对于CSM品质(溶胀度、平均粒径)的影响,并建立了相应的预测模型。方差分析的结果表明:交联剂质量分数、反应温度和引发剂浓度对于CSM溶胀度和平均粒径这2项指标都有着极为显著的影响。优化所得的较优工艺参数:交联剂质量分数为0.5%,交联温度为48℃,引发剂浓度为3.7 mmol/L。对应的CMS溶胀度及平均粒径的预测值分别为246%和16.5μm。经实验证明:应用响应曲面法所得到的CMS合成工艺参数是可行的。     

Optimization of solar-powered reverse osmosis desalination pilot plant using response surface methodology

A solar thermal and photovoltaic-powered reverse osmosis (RO) desalination plant has been constructed and optimized for brackish water desalination. The central composite experimental design of orthogonal type and response surface methodology (RSM) have been used to develop predictive models for simulation and optimization of different responses such as the salt rejection coefficient, the specific permeate flux and the RO specific performance index that takes into consideration the salt rejection coefficient, the permeate flux, the energy consumption and the conversion factor. The considered input variables were the feed temperature, the feed flow-rate and the feed pressure. Analysis of variance (ANOVA) has been employed to test the significance of the RSM polynomial models. The optimum operating conditions have been determined using the step adjusting gradient method. An optimum RO specific performance index has been achieved experimentally under the obtained optimal conditions. The RO optimized plant guarantees a potable water production of 0.2 m³/day with energy consumption lower than 1.3 kWh/m³.     

Optimization of simultaneous carotenes and vitamin E (tocols) extraction from crude palm olein using response surface methodology

In this study, response surface methodology was utilized to determine the optimal conditions for the extraction of carotenes (α- and β-carotene) and tocols (α-tocopherol, α-, γ-, and δ-tocotrienol) from crude palm olein using ethyl lactate (EL) and ethanol (EtoL) in a temperature-controlled mixer-settler system. Central composite design with four factors including temperature (X₁), mixing time (X₂), volume fraction (VF) of olein (X₃), and VF of EtOL (X₄) was used to investigate the multivariate relationship with the five responses including enrichment factor and recovery of both carotenes and tocols. The optimum extraction conditions were determined at 20°C, 10?min of mixing, 48% of crude palm olein, 31.2% of EL and 20.8% of EtoL (corresponding to 0.5 VF of olein and 0.4 VF of EtoL). The enrichment factors of carotenes and tocols were 0.88 and 2.56, respectively while 11.3% of carotenes and 31.2% of tocols were recovered.     

Cr(III) removal from simulated solution using hydrous magnesium oxide coated fly ash: Optimization by response surface methodology (RSM)

Hydrous magnesium oxide coated fly ash (MFA) has environmental remediation potential by providing a substrate for the adsorption of aqueous Cr(Ⅲ). Aqueous Cr(Ⅲ) adsorption onto MFA was examined as a function of MFA dosage, pH and initial Cr(Ⅲ) concentration with the Box-Behnken approach used for experimental design and optimization using response surface methodology (RSM). pH and dosage (dosage and concentration) have significant interactive effects on Cr(Ⅲ) adsorption efficiency. Analysis of variance shows that the response surface quadratic model is highly significant and can effectively predict the experimental outcomes. Cr(Ⅲ) removal efficiency of 98% was obtained using optimized conditions of MFA dosage, pH and initial Cr(Ⅲ) concentration of 1.57 g·L^-1, 4.11 and 126 mg·L^-1, respectively. Cr(Ⅲ) adsorption onto MFA is mainly attributed to the interaction between Cr(Ⅲ) and the functional group -OH of the hydrous magnesium oxide, in all probability caused by chemisorptions. The results of this study can conduce to reveal the interactions between Cr(Ⅲ) pollutant and MFA characteristics, posing important implications for the cost-effective alternative adsorption technology in the treatment of heavy metal containing wastewater.