Experimental Design Technique on Removal of Hydrogen Sulfide using CaO-eggshells Dispersed onto Palm Kernel Shell Activated Carbon：Experiment,Optimization,Equilibrium and Kinetic Studies

This study presents the use of chicken eggshells waste utilizing palm kernel shell based activated carbon（PKSAC） through the modification of their surface to enhance the adsorption capacity of H2S. Response surface methodology technique was used to optimize the process conditions and they were found to be： 500 mg/L for H2S initial concentration, 540 min for contact time and 1 g for adsorbent mass. The impacts of three arrangement factors（calcination temperature of impregnated activated carbon（IAC）, the calcium solution concentration and contact time of calcination） on the H2S removal efficiency and impregnated AC yield were investigated. Both responses IAC yield（IACY, %） and removal efficiency（RE, %） were maximized to optimize the IAC preparation conditions. The optimum preparation conditions for IACY and RE were found as follows： calcination temperature of IAC of 880 ℃, calcium solution concentration of 49.3% and calcination contact time of 57.6 min, which resulted in 35.8% of IACY and 98.2% RE. In addition, the equilibrium and kinetics of the process were investigated. The adsorbent was characterized using TGA, XRD, FTIR, SEM/EDX, and BET. The maximum monolayer adsorption capacity was found to be 543.47 mg/g. The results recommended that the composite of PKSAC and Ca O could be a useful material for H2S containing wastewater treatment.

Pseudomonas sp.ZXY-1,a newly isolated and highly efficient atrazine-degrading bacterium,and optimization of biodegradation using response surface methodology

Atrazine, a widely used herbicide, is increasing the agricultural production effectively, while also causing great environmental concern. Efficient atrazine-degrading bacterium is necessary to removal atrazine rapidly to keep a safe environment. In the present study, a new atrazine-degrading strain ZXY-1, identified as Pseudomonas, was isolated. This new isolated strain has a strong ability to biodegrade atrazine with a high efficiency of 9.09 mg/L/hr.Temperature, p H, inoculum size and initial atrazine concentration were examined to further optimize the degradation of atrazine, and the synthetic effect of these factors were investigated by the response surface methodology. With a high quadratic polynomial mathematical model（R^2= 0.9821） being obtained, the highest biodegradation efficiency of 19.03 mg/L/hr was reached compared to previous reports under the optimal conditions（30.71°C, pH 7.14, 4.23%（V/V） inoculum size and 157.1 mg/L initial atrazine concentration）.Overall, this study provided an efficient bacterium and approach that could be potentially useful for the bioremediation of wastewater containing atrazine.

Optimization of microwave-assisted extraction of wedelolactone from Eclipta alba using response surface methodology

An efficient microwave-assisted extraction tech- nique was used to extract wedelolactone from Eclipta alba. To optimize the effects of the microwave-assisted extraction （MAE） processing parameters on the yield ofwedelolactone, a response surface methodology with a central composite rotatable design was employed. Four independent variables were investigated： microwave power, ethanol concentration, extraction time and the solvent-to-solid ratio. The optimum conditions were： microwave power, 208 W; ethanol con- centration, 90%; extraction time, 26.5 min; and solvent-to- solid ratio, 33 mL.g-~. Under the optimal conditions, the extraction yield of wedelolactone was （82.67±0.16）%, which is in close agreement with the value predicted by the statistical model. MAE was also compared to other conventional methods, including ultrasonic assisted extrac- tion, extraction at room temperature and heat reflux extraction. MAE has distinct advantages for the extraction of wedelolactone in terms of both time and efficiency. Therefore, MAE is a reliable method for the extraction of wedelolactone from Eclipta alba.

Investigation of colloidal biogenic sulfur flocculation:Optimization using response surface analysis

The colloidal properties of biogenic elemental sulfur（S^0）cause solid–liquid separation problems,such as poor settling and membrane fouling.In this study,the separation of S^0 from bulk liquids was performed using flocculation.Polyaluminum chloride（PAC）,polyacrylamide（PAM）and microbial flocculant（MBF）were compared to investigate their abilities to flocculate S^0 produced during the treatment of sulfate-containing wastewater.A novel approach with response surface methodology（RSM）was employed to evaluate the effects and interactions of flocculant dose,pH and stirring intensity,on the treatment efficiency in terms of the S^0 flocculation and the supernatant turbidity removal.The dose optimization results indicated that the S^0 flocculation efficiency decreased in the following order PAC〉MBF〉PAM.Optimum S^0 flocculation conditions were observed at pH 4.73,a stirring speed of 129 r/min and a flocculant dose of 2.42 mg PAC/mg S.During optimum flocculation conditions,the S^0f locculation rate reached 97.53%.Confirmation experiments demonstrated that employing PAC for S^0 flocculation is feasible and RSM is an efficient approach for optimizing the process of S^0 flocculation.The results provide basic parameters and conditions for recovering sulfur during the treatment of sulfate-laden wastewaters.

Modeling and multi-response optimization of machining performance while turning hardened steel with self-propelled rotary tool

There are many advanced tooling approaches in metal cutting to enhance the cutting tool performance for machining hard-to-cut materials. The self propelled rotary tool （SPRT） is one of the novel approaches to improve the cutting tool performance by providing cutting edge in the form of a disk, which rotates about its principal axis and provides a rest period for the cutting edge to cool and allow engaging a fresh cutting edge with the work piece. This paper aimed to present the cutting performance of SPRT while turning hardened EN24 steel and optimize the machining conditions. Surface roughness （Ra） and metal removal rate （rMMR） are considered as machining perfor- mance parameters to evaluate, while the horizontal incli- nation angle of the SPRT, depth of cut, feed rate and spindle speed are considered as process variables. Initially, design of experiments （DOEs） is employed to minimize the number of experiments. For each set of chosen process variables, the machining experiments are conducted on computer numerical control （CNC） lathe to measure the machining responses. Then, the response surface method- ology （RSM） is used to establish quantitative relationships for the output responses in terms of the input variables. Analysis of variance （ANOVA） is used to check the adequacy of the model. The influence of input variables on the output responses is also determined. Consequently, these models are formulated as a multi-response optimi- zation problem to minimize the Ra and maximize the rMMR simultaneously. Non-dominated sorting genetic algorithm-II （NSGA-II） is used to derive the set of Pareto-optimal solutions. The optimal results obtained through the pro- posed methodology are also compared with the results of validation experimental runs and good correlation is found between them.

Optimization and evaluation of fish oil rnicrocapsules

Fish oil microcapsules were prepared using two natural polysaccharides, alginate and chitosan, as the wall materials. A response surface methodology （RSM） was used to optimize the conditions for fish oil encapsulation efficiency （FOEE）. The FOEE was investigated with respect to three key-variables in the RSM： ratio of inner oil phase to aqueous phase （X1 w/w）; concentration of the aqueous phase （X2, wt%）; and ratio of the aqueous phase to outer oil phase （X3, v/v）. The optimal formulation obtained from the RSM model, i.e., 2.7：1 （X1）, 1.6 wt% （X2）, and 11.5：1 （X3）, gave a FOEE of 28%. The model was validated and the fish oil microcapsules prepared under the optimized conditions were characterized in terms of particle size, polydispersity index （PDI）, zeta potential, surface morphology, and in vitro release. The average droplet size, PDI, and zeta potential were 915 nm, 0.038, and ＋5.2 mV, respectively. The fish oil microcapsules were highly uniform microspheres, and had an accumulative release rate of 77.7% in 270 min in a gastrointestinal model, indicating their potential as an alternative carrier for the controlled release of fish oil. In conclusion, formulating optimal microencapsulation conditions by the RSM can be applied to the microencapsulation of various oil-soluble nutrients for food applications.

Optimized production of a novel bioflocculant M-C11 by Klebsiella sp. and its application in sludge dewatering

The optimized production of a novel bioflocculant M-C11 produced by Klebsiella sp. and its application in sludge dewatering were investigated. The optimal medium carbon source,nitrogen source, metal ion, initial pH and culture temperature for the bioflocculant production were glucose, NaNO3, MgSO4, and pH 7.0 and 25°C, respectively. A compositional analysis indicated that the purified M-C11 consisted of 91.2% sugar, 4.6% protein and 3.9% nucleic acids（m/m）. A Fourier transform infrared spectrum confirmed the presence of carboxyl, hydroxyl,methoxyl and amino groups. The microbial flocculant exhibited excellent pH and thermal stability in a kaolin suspension over a pH range of 4.0 to 8.0 and a temperature range of 20 to 60°C.The optimum bioflocculating activity was observed as 92.37% for 2.56 mL M-C11 and 0.37 g/L CaCl2 dosages using response surface methodology. The sludge resistance in filtration（SRF）decreased from 11.6 × 1012 to 4.7 × 1012m/kg, which indicated that the sludge dewaterability was remarkably enhanced by the bioflocculant conditioning. The sludge dewatering performance conditioned by M-C11 was more efficient than that of inorganic flocculating reagents,such as aluminum sulfate and polymeric aluminum chloride. The bioflocculant has advantages over traditional sludge conditioners due to its lower cost, benign biodegradability and negligible secondary pollution. In addition, the bioflocculant was favorably adapted to the specific sludge pH and salinity.

Optimized synthesis and photovoltaic performance of TiO_2 nanoparticles for dye-sensitized solar cell

This paper presents response surface methodology （RSM） as an efficient approach for modeling and optimizing TiO2 nanoparticles preparation via co-precipitation for dye-sensitized solar cell （DSSC） perfor- mance. Titanium （IV） bis-（acetylacetonate） di-isopropoxide （DIPBAT）, isopropanol and water were used as precursor, solvent and co-solvent, respectively. Molar ratio of water, aging temperature and calcina- tion temperature as preparation factors with main and interaction effects on particle characteristics and performances were investigated, Particle characteristics in terms of primary and secondary sizes, crys- tal orientation and morphology were determined by X-ray diffractometry （XRD） and scanning electron microscopy （SEM）. Band gap energy and power conversion efficiency of DSSCs were used for perfor- mance studies. According to analysis of variance （ANOVA） in response surface methodology （RSM）, all three independent parameters were statistically significant and the final model was accurate. The model predicted maximum power conversion efficiency （0.14%） under the optimal condition of molar ratio of DIPBAT-to-isopropanol-to-water of 1 ： 10：500, aging temperature of 36 C and calcination temperature of 400 ℃. A second set of data was adopted to validate the model at optimal conditions and was found to be 0.14 ± 0.015%, which was very close to the predicted value. This study proves the reliability of the model in identi（ving the optimal condition for maximum performance.