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.     

Design of experiments for statistical modeling and multi-response optimization of nickel electroplating process

The central composite experimental design and response surface methodology have been employed for statistical modeling and analysis of the results dealing with nickel electroplating process. The empirical models developed in terms of design variables (current density J (A/dm²), temperature T (°C) and pH) have been found statistically adequate to describe the process responses, i.e. cathode efficiency Y (%), coating thickness U (μm), brightness V (%) and hardness W (HV). The graphical representations consisted of 2D contour plots and 3D surface plots have been used for exploring and analysis of response surfaces in order to identify the main, quadratic and interaction effects. The multi-response optimization of nickel electroplating process has been carried out by means of desirability function approach. To this end, a genetic algorithm has been used for mathematical optimization of the multi-response problem. The optimization algorithm has conducted to a set of equivalent solutions named Pareto optimal set. The confirmation runs have been employed in order to make a decision about the optimal solution approved by experiment. Thus, the optimum conditions of nickel electroplating has been defined in this work as J* = 5.35 (A/dm²), T* = 33.44 (°C) and pH* = 6.22 and respectively the responses confirmed by experiment were Y = 79.12 ± 0.18 (%), U = 52.77 ± 0.48 (μm), V = 26.12 ± 0.45 (%) and W = 371.6 ± 1.77 (HV). In such conditions the quality of nickel electroplating deposit was the best one in accordance with experimental results.     

Optimization of process variables for a biosorption of nickel(II) using response surface method

The biosorption of nickel(II) was studied by using crab shell particles of diameter (d _p =0.012 mm) under different initial concentrations of nickel(II) in solution (0.01–5.0 g/l), temperature (20–40 °C), pH (2–6.5), and biosorbent dosages (0.5–10 g/l). The maximum removal of nickel(II) occurred at pH 6.5 and temperature 40 °C for a biosorbent dosage of 6 g/l. The results were modeled by response surface methodology (RSM), which determines the maximum biosorption of nickel(II) as a function of the above four independent variables, and the optimum values for the efficient biosorption of nickel(II) were obtained. The RSM studies were carried out using Box-Behnken design and the analysis of variance confirms the adequacy of the quadratic model with coefficient of correlation R² to be 0.9999. The quadratic model fitted the data well with Prob>F to be <0.0001, indicating the applicability of the present proposed model.     

Simulation and optimization of the continuous tower process for styrene polymerization

The continuous tower process, a popular industrial process for the manufacture of polystyrene, was simulated and optimized. A kinetic model for the thermal polymerization of styrene, which takes into account the Trommsdorff effect and the volume change accompanying the reaction, was developed. This was used to formulate model equations for the continuous flow stirred tank reactor (CSTR) and plug flow reactor (several sections) in the tower process. The model can predict monomer conversion, number‐ and weight‐average molecular weights, polydispersity index (PDI), and temperature at various locations in the unit, under specified operating conditions. Multiobjective optimization of this process was also carried out, for which an adaptation of a genetic algorithm (GA) was used. The two objectives were maximization of the final monomer conversion and minimization of the PDI of the product. The conversion in the CSTR was constrained to lie within a desired range, and polymer having a specified value of the number‐average molecular weight was to be produced. The optimal solution was a unique point (no Pareto sets were obtained). The optimal solutions indicated that the tower process is operated under near‐optimal conditions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 775–788, 2004     

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.     

Production and optimization of sustainable cement brick incorporating clay brick wastes using response surface method

This paper aims to fabricate and optimize eco-sustainable cement brick using different sizes of clay brick waste (CBW). The prime input factors of mixtures were clay brick powder (CBP) as a binder, fine-clay brick (FCB) as a fine aggregate, and coarse-clay brick (CCB) as a coarse aggregate, whereas the compressive strength was the main response of the generated eco-sustainable bricks. This was accomplished by utilizing the central composite design (CCD) and Response Surface Methodology (RSM) with Minitab-19. Twenty mixtures with CBW were generated and experimentally evaluated utilizing CCD concept in RSM. A multi-objective optimization approach was applied to obtain the optimum results for the input parameters. Based on an experimental program, the optimum mixtures were selected to investigate the physical and durability properties of the produced brick. The SEM test was also performed to determine the effect of the CBW particles on the microstructure of the brick. The life cycle assessment of mixtures is also performed in terms of global warming potential. The optimization showed that the input components CBP, FCB, and CCB had average optimum values of 21%, 0%, and 9.09%, respectively. The experimental results showed that employing CBW yields a durable and high freeze-thaw resistance of the eco-sustainable brick despite its high porosity and absorption. Furthermore, using cement brick with CBW particles is acknowledged as a more environmentally beneficial combination. The proposed models can speed up the process of mix design by using different sizes of brick waste to get the optimum eco-friendly cement brick properties.     

Optimization of photooxidative removal of p-nitrophenol in a spinning disc photoreactor using response surface methodology

In this article, response surface methodology (RSM) was used to obtain optimum conditions for removal of p-nitrophenol (PNP) by UV/H₂O₂ process using spinning disk photoreactor (SDP). For this purpose, the effect of five independent variables, the initial concentration of PNP, the initial concentration of H₂O₂, pH, solution volume, and irradiation time on the PNP removal percent, was investigated. Central composite design, one of the response surface techniques used for process optimization. The results showed a good agreement between the RSM predicted and experimental data with “R²” and “Adjusted R²” of 0.9692 and 0.9480, respectively. In addition, “Predicted R²” of 0.8909 is in reasonable agreement with “Adjusted R²” of 0.9488. At optimal conditions, that is, PNP concentration of 20.78?mg L^?1, H₂O₂ concentration of 1355.83?mg L^?1, solution volume of 566.08?mL, irradiation time of 12.30?min, and pH of 4.59 the removal percent predicted by RSM is 100% which has good correspondence with its experimental value (98.67%).     

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     

Multiobjective optimization of the continuous casting process for poly (methyl methacrylate) using adapted genetic algorithm

The nondominated sorting genetic algorithm (NSGA) has been used to optimize the operation of the continuous casting of a film of poly (methyl methacrylate). This process involves two reactors, namely, an isothermal plug flow tubular reactor (PFTR) followed by a nonisothermal film reactor. Two objective functions have been used in this study: the cross‐section average value of the monomer conversion, x̄_mf , of the product is maximized, and the length, z_f , of the film reactor is minimized. Simultaneously, the cross‐section average value of the number‐average molecular weight of the product is forced to have a certain prescribed (desired) value. It is also ensured that the temperature at any location in the film being produced lies below a certain value, to avoid degradation reactions. Seven decision variables are used in this study: the temperature of the isothermal PFTR, the flow rate of the initiator in the feed to the PFTR (for a specified feed flow rate of the monomer), the film thickness, the monomer conversion at the output of the PFTR, and three coefficients describing the wall temperature to be used in the film reactor. Sets of nondominating (equally good) optimal solutions (Pareto sets) have been obtained due to the conflicting requirements for the several conditions studied. It is interesting to observe that under optimal conditions, the exothermicity of the reactions drives them to completion near the center of the film, while heat conduction and higher wall temperature help to achieve this in the outer regions. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1439–1458, 2000     

Seawater desalination using PVDF-HFP membrane in DCMD process: assessment of operating condition by response surface method

Central composite design (CCD) was applied in this work to analyze the performance of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) flat sheet membrane in the seawater desalination using direct contact membrane distillation (DCMD) process. It is the most popular in response surface method (RSM). Development on Quadratic Regression model for membrane performance as a function of the operating conditions was studied. The ranges for each operating condition were selected as follows: feed temperature (T_f): 48–58?°C, feed flow rate (Q_f): 80–180?mL/min, permeate temperature (T_p):17–22?°C and permeate flow rate (Q_p): 80–180?mL/min. The model R-squared of 0.9759 (adjusted to degree-of-freedom), Lack-of-fit test (p?=?0.4764), predicted residual error sum of squared (PRESS) statistic of 10.3 suggest that the model is adequate to correlate the impact of operating conditions on permeates. ANOVA analysis showed that factors as feed flow rate, feed temperature, and permeate temperature have a valuable impact (p?≤?0.05) on the response variable. Additionally, the interaction among feed temperature-feed flow rate, feed flow rate-permeate flow rate, and the quadratic impact of feed temperature, permeate temperature, and permeate flow rate have shown an important impact (p?≤?0.05) on the permeate flux. Optimization of operating conditions to make the permeate flux and salt rejection high as possible was determined according to desirability function approach. A desirability of 0.969 was achieved at a feed temperature of 58?°C, feed flow rate of 180?mL/min, permeate temperature of 18.8?°C, and permeate flow rate of 145.3?mL/min in which a permeate flux of 12.56?kg/m²h and a salt rejection of 99.97% was obtained.     

Optimization of acrylonitrile removal by activated carbon‐granular using response surface methodology

A statistical Box–Behnken design of experiments was performed to evaluate the effects of individual operating variables and their interactions on the acrylonitrile (AN) removal of C₀ = 100 mg/L as fixed input parameter. The variables examined in this study included activated carbon‐granular (AC) dosage, w, temperature, T, and time of contact, t. The significant variables and optimum conditions were identified (w = 4 g/L, T = 30°C, and t = 120 min with AN uptake of 23.97 mg/g of AC) from statistical analysis of the experimental results using response surface methodology (RSM).     

Biodegradation of coffee pulp tannin by Penicillium verrucosum for production of tannase,statistical optimization and its application

Coffee pulp is a primary by-product produced during coffee processing and represents 30% of the coffee fruit on a dry-weight basis. A novel potential tannin degrading fungi was isolated from coffee by-products. Among the various fungi isolated, Penicillium sp. CFR303 was found to be potent with 66.5 ± 0.9% tannin degradation. The potent tannin degrader was identified as Penicillium verrucosum using internal transcribed spacer's (ITS) −5.8S rDNA analysis. Solid state fermentation was carried out on coffee pulp as a sole carbon source and yielded 28.173 ± 1.4 U/gds of tannase. Further, 3.93 fold increase in tannase production (115.995 U/gds) was achieved using central composite rotatable design, a statistical approach. Model validations showed excellent agreement between the experimental results and the predicted responses with a confidence level of 95%. Coffee pulp accounts to 8–10% tannin content and the present study demonstrates coffee pulp as an excellent substrate for production of value added products. Aonla and pomegranate juice were treated with partially purified tannase and the degradation of tannins was evident by changes in the physicochemical parameters of the juice. Thus, the present investigation signifies utilization of coffee pulp for production of tannase as value addition and its potential application in the food industry.     

Use optimization of natural antioxidants in refined, bleached, and deodorized palm olein during repeated deep-fat frying using response surface methodology

An optimization study on the use of oleoresin rosemary extract, sage extract, and citric acid added into refined, bleached, and deodorized (RBD) palm olein in deep-fat frying of potato chips was carried out using response surface methodology (RSM). Results showed that oleoresin rosemary extract was the most important factor affecting the sensory acceptability of potato chips. For taste and odor, its effects were highly significant (P<0.01), while for crispiness and overall acceptability, the effects were significant (P<0.05). As for sage extract, the level of this antioxidant had a highly significant (P<0.01) effect on appearance and taste and a significant effect (P<0.05) on odor and overall acceptability, but had no effect on crispiness. Although there was no significant synergistic correlation between citric acid and oleoresin rosemary extract or sage extract at the first order, its second order was significantly (P<0.05) related to taste, crispiness, and overall acceptability. An interaction between oleoresin rosemary and sage extracts also significantly (P<0.05) improved the score of overall acceptability of the potato chips. Contour maps of the sensory scores of potato chips indicated that the optimal points for appearance were achieved using 0.062% oleoresin rosemary extract, 0.066% sage extract, and 0.023% citric acid, while optimal task was achieved with 0.063% oleoresin rosemary extract, 0.075% sage extract, and 0.025% citric acid. With the same sequence of ingredients added into oil, the combinations required to achieve the optimal odor, crispiness, and overall acceptability scores were 0.058-0.046-0.026, 0.060-0.071-0.022, and 0.060-0.064-0.026%, respectively.     

Investigations of the effects of temperature and initial sample pH on natural organic matter (NOM) removal with electrocoagulation using response surface method (RSM)

The removal of natural organic matter (NOM) from surface water by electrocoagulation (EC) was studied using response surface method (RSM). Factors used in the empirical model were electric charge per liter, initial pH and temperature. Relevant square and interaction terms of factors were studied. Based on analysis of variance (ANOVA), the model fitted well with dissolved organic carbon (DOC) reduction, aluminum dissolving and pH changes. UV 254 nm absorbance removal was moderately predicted. According to results, temperature affected significantly the dissolving rate of aluminum electrodes. Initial DOC concentration of the surface water was 18.35 mg/l. Maximum DOC removal of 80.4% was obtained when high electric charge per liter (144 C/l), low pH (4.3) and high temperature (295.15 K) were used. However, high DOC removal of 76.2% was predicted also when water temperature was only 275.15 K. Effect of temperature on NOM removal was minor as compared to the effects of electric charge per volume and the initial pH. EC neutralized pH during the EC treatment and had little impact on the conductivity of the water. According to the results, EC can be used for NOM removal during cold water period in Nordic countries.     

Modeling and optimization of an industrial hydrocracking unit to improve the yield of diesel or kerosene

Hydrocracking is used in the petroleum industry to convert low-quality feedstocks into highly-valued transportation fuels. This process is the best source of low-sulfur and low-aromatics diesel fuel as well as high-smoke point jet fuel. Many approaches have been proposed for solving optimization of hydrocracking units in the last decades, but they usually neglect the reaction in hydrotreater where hydrocarbon cracking often occurs, thus leading to suboptimal solutions in industrial problems. Unlike existing literature, this paper considers the hydrocarbon cracking reactions in hydrotreater and hydrocracker simultaneously. The models are based on energy balance, mass balance and a discrete lumped model approaches for kinetic modeling. Before optimization, the properties of feedstock are predicted with ASPEN PLUS by using laboratory data from the refinery, and then the model parameters are estimated with genetic algorithm (GA) based on industrial data and validated by comparing the simulating results with industrial data. To improve the yield of the lighter products, the operation conditions are optimized by GA and Sequential Quadratic Programming (SQP). The yields of the diesel or kerosene increase with the proposed approach.     

Optimization of biodiesel production from crude palm oil using ultrasonic irradiation assistance and response surface methodology

BACKGROUND: Production of biodiesel from crude palm oil (CPO) with 6 wt% of free fatty acid (FFA) using a low‐frequency ultrasonic irradiation (40 kHz) technique was investigated in the present work. The objective of this study was to determine the relationship between various important parameters of the alkaline catalyzed transesterification process to obtain a high conversion to biodiesel. Response surface methodology (RSM) was used to statistically analyze and optimize the operating parameters of the process. A central composite design (CCD) was adopted to study the effects of the methanol to oil molar ratio, the catalyst concentration, reaction temperature, and irradiation time on conversion to biodiesel. RESULTS: The result from the RSM analysis indicated that the methanol to oil molar ratio, catalyst concentration and irradiation time have the most significant effects on the conversion to biodiesel. Moreover, a coefficient of determination (R²) value of 0.93 shows the fitness of a second‐order model for the present study. Based on this second‐order model, the optimum conditions for alkaline catalyzed transesterification of CPO were found to be a methanol to oil molar ratio of 6.44:1, catalyst concentration 1.25 wt%, reaction temperature 38.44 °C and irradiation time 25.96 min. At the calculated optimum condition, the conversion to biodiesel reached 97.85%. Under these same conditions, the experimental value was 98.02 ± 0.6%. CONCLUSIONS: The mathematical model developed has been proven to adequately describe the range of the experimental parameters studied and provide a statistically accurate prediction of the optimum conversion to biodiesel. Copyright © 2011 Society of Chemical Industry     

星点设计-效应面优化法优化阿司匹林肠溶片的包衣工艺

目的：采用星点设计一效应面优化法优化传统包衣锅制备阿司匹林肠溶片包衣工艺,提高其包衣效率。方法：通过筛选雾化压力、蠕动泵转速及枪一床距离3个工艺参数确定各因素水平,安排实验,结果以包衣效率为指标考察。结果：优化后的包衣工艺可有效的进行包衣。结论：星点设计一效应面优化法可利用最少的实验次数得到优化后的包衣工艺。     

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.