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Reusability of two heterogeneous catalysts in ultrasound (US) assisted biodiesel production was investigated in comparison to each other. An ultrasound (US) generator (200 W, 20 kHz) equipped with a horn type probe (19 mm) was used. Regeneration experiments were planned according to second order central composite design (CCD) method. After the eighth use of the catalysts, biodiesel yield decreased from 99.1% to 90.4% for calcined calcite (CaO) and from 98.8% to 89.8% for calcined dolomite (CaO center dot MgO). Furthermore, regeneration of spent catalysts by calcination was investigated; optimum temperature and time were found as 750 degrees C and 90 min, lower than fresh catalyst preparation conditions. The regenerated catalysts were reused in a second process cycle; biodiesel yield was calculated as 97.2% for CaO and 96.5% for CaO center dot MgO. Finally, the process showed that calcination is an energetically favorable regeneration process of spent catalysts.

Microwave-assisted extraction (MAE) and solvent-free microwave extraction and Soxhlet extraction were applied to Ray Ruby grapefruit leaves (Citrus paradisi Macf.) to compare extract efficiency. Face centered composite designs were constructed via response surface methodology. Effects of factors of MAE were investigated on total phenolic content (TPC) and naringin content (NC). The optimized conditions were established as 1.4 kWL−1 for microwave power density, 20.00 gL−1 for solid/solvent ratio, 218.180 s for extraction time, while responses were calculated as 14.210 mg of gallic acid equivalent per g of the dried leaf (mg GAE g−1DL) and 13.198 mg of naringin per g of dried leaf (mg Ng−1DL) for TPC and NC, respectively. SFME and classical Soxhlet methods were also conducted for comparison reasons.

In recent years, a great deal of concentration has addressed the electronic and morphological characteristics of carbonaceous substances. Nowadays, particularly, graphene is one of the most popular materials in condensed-matter physics and materials science. It is used in different fields such as desalination of seawater, smartphones, computers, satellites, planes, cars, building materials, obtaining protective coatings and rust-free cars, nuclear clean up, transistors, sensors, electron microscopy, Li ion batteries, super capacitors, and bionics. Mechanical cleaving (exfoliation), chemical exfoliation, chemical synthesis, and thermal chemical vapor deposition (CVD) synthesis are the most commonly used methods today. Some other techniques are also reported such as unzipping nanotube and microwave synthesis. In graphene synthesis, starting material is usually graphite. On the other hand, different starting materials such as rice husks, fenugreek seeds, hibiscus flower petals, camphor, alfalfa plants, petroleum asphalt are used as a carbon source for graphene synthesis. In this study, alternative methods for graphene synthesis specially microwave irradiation and ultrasound energy were studied, and the performances of the final products were compared with the help of different characterization techniques. Advantages and drawbacks of these methods were clearly discussed for enhancing the understanding of the graphene synthesis phenomena.

Graphene is one of the most promising materials discovered in last years. It is usually synthesized by Hummers’ method requiring the usage of many chemicals. As an alternative to traditional methods, in this study a bottom-up synthesis method was developed from various saccharides such as starch, mannose, cellulose, fructose, arabinose, and xylose by carbonization at 600 °C to 800 °C in LiCl/KCl molten salt system. The proposed method is environmental friendly and economic. Graphene yields at 600 °C are higher than at 800 °C. Graphene products give peak at 2θ = 23° on the X-Ray Diffraction (XRD) patterns. As the temperature is increased, amorph structure is observed on the XRD patterns. Raman spectroscopy results show that intensity of D band peak over intensity of G band peak (ID/IG) values of graphene products synthesized from arabinose and cellulose at 600 °C, graphene from arabinose synthesized at 800 °C are 0.76, 0.65 and 0.85 respectively, which show that these products are few-layered. According to X-ray photoelectron spectroscopy (XPS) results, graphene products synthesized at 600 °C have higher carbon content than those synthesized at 800 °C.

A process-controlled synergistic solvent extraction (SSX) system consisting Mextral EOL (β-diketone derivative) and Cyanex 923 (mixture of four alkyl phosphine oxides) has been developed for the extraction of lithium from borate and sodium rich wastewaters induced by boron industry. In order to determine regression models and determine optimum conditions, a D-optimal experimental plan was created. Reduced cubic models were chosen for all lithium and sodium extraction studies. Accordingly, the most negative effect in lithium extraction was the aqueous phase/organic phase ratio (A/O), while the pH was the most positively effective parameter. Mextral EOL had no effect on sodium extraction. Notably, it was found that Mextral EOL and Cyanex 923 had up to 1.6 times synergistic effect on lithium extraction. In optimization, the sodium extraction efficiency is minimized while the lithium yield is maximized. Three different optimization criteria were determined in each wastewater and three different optimum alternatives were established. Accordingly, the highest lithium yield was predicted to be above 91.0% and sodium yield was below 4.70%. In back-extraction studies, water and different concentrations of HCl acid solutions were used as scrubbing and stripping agents. As a result, the Mextral EOL/Cyanex 923/Kerosene SSX system has been proven to be an effective method for maximizing lithium extraction from borate-rich wastewaters and for minimizing sodium extraction.

Liquid Phase Exfoliation (LPE) method has been gaining increasing interest by academic and industrial researchers due to its simplicity, low-cost, and scalability. High intensity ultrasound energy was exploited to transform graphite to graphene in the solvents of dimethyl sulfoxide (DMSO), N,N-dimethyl formamide (DMF), and perchloric acid (PA) without any surfactants or ionic liquids. The crystal structure, number of layers, particle size, and morphology of the synthesized graphene samples were characterized by X-ray Diffraction (XRD), Atomic Force Microscopy (AFM), Ultraviolet visible (UV–vis) spectroscopy, Dynamic Light Scattering (DLS), and Transmission Electron Microscopy (TEM). XRD and AFM analyses indicated that G-DMSO and G-DMF have few layers and G-PA has multilayers. The layer numbers of G-DMSO, G-DMF, and G-PA were determined as 9, 10, and 21, respectively. By DLS analysis, the particle sizes of graphene samples were estimated in a few micrometers. TEM analyses showed that G-DMSO and G-DMF possess sheet-like fewer layers and also, G-PA has wrinkled and unordered multilayers.

Green synthesis of graphene from graphite was carried out in molten salt mixture of LiCl-KCl, which is an environmentally friendly alternative to traditional methods using a large number of chemicals. The effect of carbonization temperature on the final properties of graphene products was investigated at a temperature range of 500-800°C. The layer numbers of graphene products were determined as a single layer and few layers by XRD and Raman analyses. The highest conductivity value of 1219 S/m was reached with the sample synthesized at 600°C (GGr600), which is 10-fold higher than that of commercial graphene (CG) (115 S/m). The percentage of carbon contents of GGr600 and sample synthesized at 800°C (GGr800) was determined as 86% and 73% by XPS. From the SEM analyses, it was observed that graphene products have sheet-like structures. A TEM image showed that GGr800 has the thickness changing from 5-9 nm, pointing out the graphene with few layers. AFM analysis demonstrated that GGr600 has a single-layer sheet-like structure.

In this study, Poly(l-lactic acid) (PLLA) synthesis was studied using direct melt condensation polymerization (DMP) method in an experimental microwave (MW) system where external cooling was applie...

The extraction of phenolic compounds from grapefruit leaves assisted by ultrasound-assisted extraction (UAE) was optimized using response surface methodology (RSM) by means of D-optimal experimental design and artificial neural network (ANN). For this purpose, five numerical factors were selected: ethanol concentration (0-50%), extraction time (15-60 min), extraction temperature (25-50 °C), solid:liquid ratio (50-100 g L-1 ) and calorimetric energy density of ultrasound (0.25-0.50 kW L-1 ), whereas ultrasound probe horn diameter (13 or 19 mm) was chosen as categorical factor.; Results: The optimized experimental conditions yielded by RSM were: 10.80% for ethanol concentration; 58.52 min for extraction time; 30.37 °C for extraction temperature; 52.33 g L-1 for solid:liquid ratio; 0.457 kW L-1 for ultrasonic power density, with thick probe type. Under these conditions total phenolics content was found to be 19.04 mg gallic acid equivalents g-1 dried leaf.; Conclusion: The same dataset was used to train multilayer feed-forward networks using different approaches via MATLAB, with ANN exhibiting superior performance to RSM (differences included categorical factor in one model and higher regression coefficients), while close values were obtained for the extraction variables under study, except for ethanol concentration and extraction time. © 2018 Society of Chemical Industry.; © 2018 Society of Chemical Industry.

In this study, the experimental optimization of ultrasound assisted biodiesel production in presence of heterogeneous catalyst was investigated. Three catalysts namely; CaO, calcined dolomite and calcium diglyceroxide (CaDG) were taken into account for comparative purpose. D-optimal experimental plan was applied to obtain regression models which were subsequently used for the detection of optimum process conditions. Maximum biodiesel yields were calculated as 98.7%, 95.9% and 86.3% for CaO, calcined dolomite and CaDG respectively. Furthermore, supplemental experiments were conducted around optimum process conditions to test the validity of the regression models and to refine the optimum results. Finally, in the case of CaO catalyst, maximum biodiesel yield (99.4%) was obtained at the following conditions; catalyst loading: 5.35% (wt.of oil), methanol/oil ratio: 7.48, ultrasonic power: 40 W, time: 150 min, and reaction temperature: 60 °C.

In this study, calcium carbonate has been produced continuously using synthetic soda ash industry liquid waste with different process variables. The effect of process variables such as gas flow rate (1000 to 4000 ml/min), waste liquid flow rate (80 to 280 ml/min), CO2 concentration (20% to 40%), ultrasonic probe area (2.83 to 4.90 cm2), ultrasonic probe immersion depth (2/3 h to 1/2 h), ultrasonic power (0% to 70%), and reaction temperature (30°C to 50°C) on product quality was investigated by using D-optimal design. According to the experimental results, precipitated calcium carbonate (PCC) having different particle sizes (D (4:3)) ranging from 2.9 µm to 8.7 µm was obtained. It was observed that crystal structure of product is highly dependent on the pH of reaction medium. While vaterite and aragonite crystal structure were formed at low pH values, calcite crystal structure was formed at higher pH values. Particle size decreases when ultrasound power applied at 35% when compared to silent reactions. Overall, precipitated CaCO3 with desired particle size and crystal type can be produced by controlling the process variables. The CaCO3 was produced in amounts ranging from 3.4 g to 11 g depending on the experimental conditions.

Antibiotic-resistant organisms are crucial problems, which lead to ecological disasters and cause fatal damage such as in aquatic environments and human beings. Thus, researchers have sought an effective way to minimize this issue, and they stated that the photocatalytic reaction is an effective method for degrading antibiotics. In this study, an aqueous solution containing cefixime trihydrate (CFX) was exposed to UV-A irradiation. TiO2 was used as the principal compound of the photocatalyst, known as the state-of-the-art semiconductor material. In order to reduce its band gap, dopped-graphene oxide and chitosan were impregnated in TiO2 solution. The spectrum Two FT-IR spectrometer (FTIR), X-Ray diffraction method (XRD), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) and Scanning electron microscope with energy dispersive X-Ray analysis (SEM-EDX) and thermogravimetric analysis (TGA) were used to illuminate the structure of TiO2/GO/chitosan. d -optimal design of the experiments via response surface methodology (RSM) including both numerical and categorical factors to explore the synergistic effects of process variables. The results showed that TiO2/GO/chitosan exhibited good degradation efficiency (95.34%) under optimal conditions (catalyst dose: 0.327 gL−1, cefixime concentration: 20.29 mgL−1, pH:4.1 and UV-A irradiation: 60 W). Statistical analysis verified the accuracy of the regression model according to the empirical data. The recycling tests showed that the prepared photocatalyst has an outstanding performance for durability and stability under UV-A irradiation.

This study deals with the nitration of phenol in a multimode MW reaction system operating under continuous microwave (MW) irradiation. Reactions were carried out with two nitric acid (HNO3)/phenol ...

Ultrasound (US) assisted transesterification of canola oil in presence of heterogeneous catalysts calcined dolomite and CaO was investigated in comparison to each other. An US generator (200 W, 20 kHz) equipped with an horn type probe (19 mm) was used to study the effect of catalyst amount (3–7 wt.% of oil), methanol/oil molar ratio (4/1–15/1), ultrasound power (30–50 W), temperature (25–60 °C) and time (60–120 min) on US assisted biodiesel synthesis. Biodiesel yield reached over 97.4% for calcined dolomite at the end of 90 min and 95.5% for CaO at the end of 75 min. According to the results, US improved the transesterification reaction by reducing necessary time for high biodiesel yield, using calcined dolomite as well CaO as heterogeneous catalyst.

This paper investigated the effects of extracellular polymeric substances (EPS) on the activated sludge rheology in a submerged membrane bioreactor (sMBR) operated at different sludge retention time (SRT) values and different carbon to nitrogen ratios (C/N) of feed wastewater. The C/N ratios of the feed were adjusted accordingly so that synthetic wastewaters prepared simulated municipal wastewater, non-toxic wastewater with high C/N ratio and non-toxic wastewater with low C/N ratio. A number of important operational parameters such as mixed liquor suspended solid (MLSS), protein fraction of EPS (EPSp), carbohydrate fraction of EPS (EPSc), protein fraction of soluble microbial product (SMPp), carbohydrate fraction of SMP (SMPc), apparent viscosity, critical flux and hydrophobicity in mixed liquor and their correlations were investigated in the sMBR systems operated. The statistical analysis indicated that the C/N ratio of feed, SRT, MLSS and SMPc were found to have positive effects on apparent viscosity at three different shear rates. On the other hand, a negative impact was detected between the apparent viscosities and the critical fluxes. It was also observed that there is a significant positive correlation between hydrophobicity and both EPSp and SMPp.

Today, considerable attention has been focused on the improved elimination of non-biodegradable pollutants through hybrid (combined) processes. In this study, a combination of electrocoagulation (EC) and photochemical oxidation (PCO) was proposed for the removal of hydroquinone (HQ) from aqueous solution. The experiments were carried out to investigate the effects of current density, HQ concentration, UV light power and different combination of both processes (EC and PCO recirculation loop process, only EC, only PCO with or without air supply) on the removal efficiencies of HQ and p -Benzoquinone (BQ). Furthermore, the adsorption capacity of aluminum hydroxide electrocoagulant flocs was calculated and the oxidation extent of HQ to BQ was investigated. According to the results, HQ removal efficiency increased nearly 40% owing to air supply in the reaction medium, while high removal extent of BQ by electrocoagulant flocs increased the performance of the EC–PCO process which allowed the removal extent of HQ to be as high as 91.5% at the following operating conditions; current density: 5 A/m 2 , UV light power: 24 W (37 W per dm 3 of the solution), operating time: 60 min.

In this study, an experimental system irradiated by Microwave (MW) energy was proposed, the main aim being to conduct experimental studies at isothermal conditions and under constant and continuous MW energy supply. For this purpose, a coil-cooled reactor was designed using a MW transparent coolant such as o-xylene circulated between a thermostat bath and the reactor. A dynamic thermal model of the system was derived to be used for selecting system operating parameters to ensure required MW power at isothermal conditions. To estimate unknown thermal parameters of the system, heating/cooling experiments were conducted using a viscous liquid (glycerine) as the reactor charge. Furthermore, the mathematical model was tested with experimental data. The correction factors for the amount of MW power supplied to the system calculated from the model and standard calibration data were found to be consistent. The fit between the experimental and the model simulated data was fairly good with a value of 0.94 validation coefficient.

The extraction of phenolic compounds from grapefruit leaves assisted by ultrasound-assisted extraction (UAE) was optimized using response surface methodology (RSM) by means of D-optimal experimental design and artificial neural network (ANN). For this purpose, five numerical factors were selected: ethanol concentration (0-50%), extraction time (15-60 min), extraction temperature (25-50 °C), solid:liquid ratio (50-100 g LThe optimized experimental conditions yielded by RSM were: 10.80% for ethanol concentration; 58.52 min for extraction time; 30.37 °C for extraction temperature; 52.33 g LThe same dataset was used to train multilayer feed-forward networks using different approaches via MATLAB, with ANN exhibiting superior performance to RSM (differences included categorical factor in one model and higher regression coefficients), while close values were obtained for the extraction variables under study, except for ethanol concentration and extraction time. © 2018 Society of Chemical Industry.

MW-assisted emulsion polymerization of styrene (M) is examined in this study. Six process variables namely, H 2 O/M, SDS/M, KPS/M, temperature ( T ), reaction time ( t ) and MW power density ( P ) were investigated in comparison with the conventional heating (CH) method to assess their effects on the polymerization yield and the specific MW energy consumption. An experimental system was designed to keep both T and P continuous and constant during the polymerization. Based on a systematic study, it is found that MW power accelerates the polymerization rate, especially in the initiation step of the polymerization. While 95% conversion was achieved in 40 min under P = 0.8 kW dm −3 , 90 min was necessary for CH method to reach the same conversion level. Polymers obtained by MW and CH methods under the same process conditions were found to have the same structural and thermal characteristics.

This study deals with the experimental investigation of compositional changes of various liquid/gas streams during mid-term (3 h) continuous operation of an active direct methanol fuel cell (DMFC). A test system is equipped with various sensors and with sampling ports to collect liquid samples to measure off-line methanol, formaldehyde, and formic acid concentrations by means of high pressure liquid chromatography (HPLC) and UV spectroscopy. Initially, polarization study is performed to select suitable operating ranges to be considered in an experimental plan according to which runs are performed to collect process data from the system. Then, the experimental data is fitted using regression analysis for the statistical evaluation of the impacts of operating variables on the compositions of methanol tank solution and cathode gas by means of response surface plots. The cathode gas composition is further discussed in the context of methanol crossover and catalytic chemical reactions on the cathode side. Experiments show that methanol, formaldehyde, and formic acid concentrations may exceed their safe limits of exposure depending on the operating conditions. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 1847–1855, 2017. © 2017 American Institute of Chemical Engineers Environ Prog

In this work, the effect of the solvent type on microwave (MW)-assisted decomposition of 2,2′-azobis(isobutyronitrile) was investigated by online monitoring of the reaction kinetics in various solv...

In this paper, various physical and chemical characteristics of electro-coagulated (ECC) and chemical-coagulated (CC) aluminum hydroxide flocs were explored comparatively in the context of their impacts on the pollutant removal performance of the processes. First, the sedimentation rate, floc size and zeta potential of the flocs at different pH values were measured in solution. Furthermore, flocs dried at 105 °C were characterized by various techniques such as TGA,FT-IR, SEM, XRD, BET and XPS as well as by chemical analysis. It was found that ECC flocs were bigger in size, faster in sedimentation and better pressed, while they had higher BET area, less water and higher isoelectric pH than CC flocs. Furthermore, pollutant removal tests using various chemicals such as benzoquinone, hydroquinone and a reactive dye showed that ECC flocs outperformed CC flocs, due to superior physical-chemical characteristics.

In this study, the ceramic powders of Ce 1− x Gd x O 2− x /2 and Ce 1− x Nd x O 2− x /2 ( x =0.05, 0.10, 0.15, 0.20 and 0.25) were synthesized by ultrasound assisted co-precipitation method. The ionic conductivity was studied as a function of dopant concentration over the temperature range of 300–800 °C in air, using the impedance spectroscopy. The maximum ionic conductivity, σ 800 °C =4.01×10 −2 Scm −1 with the activation energy, E a =0.828 kJmol −1 and σ 800 °C =3.80×10 −2 Scm −1 with the activation energy, E a =0.838 kJmol −1 were obtained for Ce 0.90 Gd 0.10 O 1.95 and Ce 0.85 Nd 0.15 O 1.925 electrolytes, respectively. The average grain size was found to be in the range of 0.3–0.6 μm for gadolinium doped ceria and 0.2–0.4 μm for neodymium doped ceria. The uniformly fine crystallite sizes (average 12–13 nm) of the ultrasound assisted prepared powders enabled sintering of the samples into highly dense (over 95%) ceramic pellets at 1200 °C (5 °C min −1 ) for 6 h.

Optimal design of shell and tube heat exchangers (STHE) has a crucial role in terms of the energy efficiency of plants. Therefore, it is currently one of the research topics of interest. In this study, a rigorous STHE design model strictly following TEMA standards and including various crucial constraints was established. Ten design variables of various kinds (continuous, integer, discrete, binary, and type) were selected for MINLP task. The handling of noncontinuous variables was attempted by means of three approaches including GA, PSO, and hybrid branch and bound methods over three case studies. Comparisons of the algorithms were performed using various performance criteria. Besides, the presence of noncontinuous variables in MINLP was analyzed. As a brief result, when type/binary/integer variables were included as optimization variables, very poor results were obtained, and hybrid PSO exhibited performance in each case superior to the others in terms of objective function value.

In this work, the specific effect of microwave (MW) energy on chemical reactions was investigated by online monitoring of the decomposition kinetics of potassium persulfate (K2S2O8). Experiments conducted at constant temperature and constant MW power revealed that the rate constant was about 1.1–1.8 times higher than the rate constant of the thermally heated system at the same temperature, depending on the MW power. To model the dependence of the rate constant on the MW power as k = f(P) exp(−g(P)/T), various functional forms of MW power were envisaged for g(P) (activation energy Ea) and for f(P) (preexponential factor ko). Linear, quadratic, and cubic polynomial models were tried for both functions. Nonlinear regression analysis was performed and detailed statistical analysis was applied, and the best results were obtained with quadratic f(P) and cubic g(P) functions, with the highest R2adj (0.9975) and the lowest standard deviation (0.94 × 10–5). The mathematical model revealed that both the activation ...

Experimental and simulation studies were conducted to design a multiregional fuzzy logic controller (FLC) for a lab-scale pH process system. Scaled coefficients of the controller were optimized offline to obtain the best controller performance in terms of cost function and function evaluation number using two widely used global optimization methods; namely, Genetic Algorithm (GA) and Particle Swarm Optimization (PSO). Various tuning parameters of these optimization algorithms were investigated in detail to compare their performance on this subject. The cost functions obtained via two algorithms were very close to each other, but the function evaluation number was almost 4-fold due to complicated computation of the GA compared to the PSO. On the other side, working with the PSO was much easier owing to fewer adjustable parameters. In the second part of the study, the rule base of the controller was minimized using two different new methods. In this context, the number of rules was reduced by 43% and 56% us...

In the present study, Fenton's oxidation of a chromium complex disazo dye (Acid Blue 193) synthesis wastewater was evaluated, modeled and optimized by employing Central Composite Design. Within this context, the individual and interactive effects of critical process parameters such as Fe2 + , H2O2 concentrations, initial chemical oxygen demand (COD) and reaction time was assessed. The process response (output) variables were chosen as percent color, COD and total organic carbon (TOC) removal efficiencies. Optimum working conditions in terms of color and organic carbon removals were established to be Fe2 + = 3 mM; H2O2 = 25 mM; reaction time = 10 min at pH 3 and an initial COD content of 245 mg/L. Under these conditions, 96% color, 82% COD and 51% TOC removals were obtained. The established polynomial regression models describing color, COD and TOC removals satisfactorily fitted the experimental data and could be used to predict Fenton's treatment results at statistically significant rates. Optimized treatment results were compared with those obtained via electrocoagulation treatment under optimized conditions (applied current = 50 A/m2; reaction time = 15 min; initial pH = 7 for an initial COD content of 245 mg/L). The relative inhibition of heterotrophic oxygen uptake rate was measured to examine the inhibitory effect of azo dye synthesis effluent before and after Fenton's oxidation and electrocoagulation with respect to synthetic domestic wastewater. Untreated azo dye production wastewater exhibited a slightly inhibitory effect that was appreciably reduced but not entirely removed after Fenton's oxidation, whereas no inhibition of mixed bioculture was observed for azo dye synthesis effluent subjected to electrocoagulation treatment.

In the present investigation, treatment of metal cutting wastewater (MCW) using electrocoagulation (EC) process is designed and analyzed using response surface methodology (RSM). RSM is applied to optimize the operating variables viz. initial pH, current density, and operating time on the treatment of MCW in a batch mode by EC process using iron and aluminum electrodes. Quadratic models are developed for the responses such as chemical oxygen demand (COD), total organic carbon (TOC), and turbidity, and operating cost is calculated with respect to energy, electrode, and chemical consumptions. The actual COD, TOC, and turbidity removal efficiencies at optimized conditions are found to be 93.0%, 83.0%, and 99.8% for Fe electrode and 93.5%, 85.2%, and 99.9% for Al electrode, respectively, which agree well with the predicted response. The proposed model fits very well with the experimental data with R (2) adjusted correlation coefficients of 0.927 for COD, 0.924 for TOC, and 0.968 for turbidity removal for Al and 0.904 for COD, 0.976 for TOC, and 0.989 for turbidity removal for Fe electrodes, respectively. This study clearly shows that RSM is one of the suitable methods to optimize the operating conditions and maximize the COD, TOC, and turbidity removal efficiencies for both electrodes while keeping the operating costs to minimal (0.371 a,not sign/m(3) for Fe and 0.337 a,not sign/m(3) for Al electrodes).

Supported ZnO film photocatalysts are prepared on glass and ceramic substrates by zincate method. Prepared ZnO films are seen rather strongly durable. They resist to chemical dissolution in a broad range of pH from 3 to 10. Various physical tests are conducted to measure the relevant characteristics of the films. Band gap of ZnO film is Calculated as 3.24eV. SEM analysis shows that the ZnO film has granular morphology with uniform particle size about 300-400 nm. The film thickness is calculated as 1.41 mu m after twenty coating cycles and the thickness of the thin film per cycle was approximately 70 turn. Photochemical activity tests are performed by measuring photodecolorization rate of methyl orange solution. First order rate constants are correlated to principal process parameters. The results show that ceramic is the preferable supporting material with high activity. According to simulation study, the photocatalytic activity of film coated on ceramic ring of 8 mm diameter is nearly equal to the activity of powder ZnO slurry of 120 mg/dm(3) density. It carried out about decolorization 65% in 3 h. The calculations show that it is possible to prepare ZnO film on ceramic ring with similar activity as powder ZnO. (C) 2009 Elsevier B.V. All Fights reserved.

Effluent iron concentration is an important water quality criterion used for the assessment of the performance of rapid sand filters, in addition to other criteria. This study deals with the prediction of effluent iron concentrations by adaptive neuro-fuzzy (ANFIS) model with input parameters including filter hydraulic loading rate, influent iron concentration, bed porosity and operation time. With trying various types of membership functions, two rule base generation methods, namely subtractive clustering and grid partition were used for a first order Sugeno type inference system. Models were evaluated using root mean squared error (RMSE), index of agreement (IA) and R2 as statistical performance parameters. The fit between experimental results and model outputs showed good agreement for tap water and deionized water; testing RMSE values were 36.33 and 7.66 µg/L, the IA values were 0.996 and 0.971, and R2 values were 0.99 and 0.89, respectively. It was concluded that neuro-fuzzy modeling may be successfully used to predict effluent iron concentration in sand filtration. © 2009 Elsevier Ltd. All rights reserved.

Central composite design was used to optimise electrocoagulation of CI Acid Blue 193 production wastewater. By applying a response surface quadratic model, the main process manipulators (effluent chemical oxygen demand, initial pH, electrical current density and treatment time) were optimised to achieve maximum colour, chemical oxygen demand and total organic compound removals. Analysis of variance indicated that the established polynomial regression models were significant and fitted the experimental data satisfactorily.

This study focused on the removal of nickel ions from aqueous solution using a surfactant-enhanced (SE) powdered activated carbon (PAC)/microfiltration (MF) hybrid membrane process. The main objective of the research is to investigate the technical performance of the process under the influences of all relevant process variables namely process time, recycling time, pH, temperature, PAC concentration, surfactant concentration, nickel concentration, cross-flow velocity, and transmembrane pressure, thus to reveal its applicability to water problems involved in heavy metal pollution. The concentrations of PAC, surfactant, metal, and H+ ion were determined as significant process stream variables, while transmembrane pressure and temperature came into prominence as significant operating variables. ANOVA calculations indicated that the total influences of these six variables on process performance realized in a range of about 93−98%. Nickel concentration and PAC amount in the feed were established as the most in...

Breakthrough and terminal head loss are the main parameters that determine the performance of rapid sand filters. Carman-Kozeny and Ergun equations can be applied to estimate head loss, but can only be applied to clean filter beds. Elaborated models are needed to predict head loss in dirty filters. In this study, a neuro-fuzzy modeling approach was proposed to estimate head loss in dirty filters. Hydraulic loading rate, influent iron concentration, bed porosity, and operating time were selected as input variables. Various types of membership functions were tried. Two rule-base generation methods - subtractive clustering and grid partition - were used for a first-order, Sugeno-type inference system. Using 11 rules and the grid-partition method, an optimum rule base set was developed and the lowest root mean squared error (RMSE) was obtained. Tap and deionized waters were used to obtain testing RMSE values of 1.094 and 0.926, respectively. The fit between experimental results and model outputs was excellent, with the multiple correlation coefficient (R2) greater than 0.99. Based on these findings, the authors conclude that neurofuzzy modeling may successfully be used to predict filter head loss.

The photocatalytic degradation of a commercial azo-reactive textile dye, Remazol Red F-3B, has been investigated in a batch slurry reactor using semiconductor catalysts like, ZnO and TiO2, and two UV sources emitting mainly at 254 and 365 nm. Non-irradiated catalysts and non-catalyzed UV irradiation have negligible effect on the dye degradation. Initial pH, dye concentration, light power and catalyst loading as well as the catalyst type and UV wavelength are considered as process variables. The results showed that decolorization and TOC removal efficiencies of ZnO are higher under 365 nm UV. On the other hand, when two photocatalysts are compared, the decolorization performance of ZnO is higher than TiO2 under 365 nm UV, while TiO2 performs better under 254 nm UV. Furthermore, from the TOC removal point, TiO2 performs better than ZnO irrespective of the UV wavelength. TiO2 irradiated under 254 nm UV degrades successfully both benzene and naphthalene derivatives.

Electrocoagulation (EC) technique is applied for the treatment of waste metal cutting fluids (WMCFs) characterized by high COD and TOC concentration, discharged from metal manufacturing facilities including automotive engine, transmission, and stamping plants. The effects of initial pH, current density and operating time on the performance of EC are investigated by using sacrificial Al and Fe electrodes. Upon treatment by EC, the COD of WMCF is reduced by 93% and the TOC is reduced by 78% for Al electrode at pH 5.0, current density of 60 A/m 2 and operating time of 25 min. For Fe electrode, the reduction in COD is 92% and reduction in TOC is 82% at pH 7.0, current density of 60 A/m 2 and operating time of 25 min. Under optimal operating conditions, the operating costs are calculated as 0.497 $/m 3 (0.023 $/kg removed COD or 0.144 $/kg removed TOC) for Fe electrode, and 0.768 $/m 3 (0.036 $/kg removed COD or 0.228 $/kg removed TOC) for Al electrode. Fe electrode is found to be more efficient than Al electrode in terms of parameters such as COD and TOC removal efficiencies and operating costs.

The bench scale of an electrocoagulation (EC) unit requires a detailed study discerning the effects of continuous variables such as pH, current density and operating time, and type variables such as electrode material and connection mode. This paper presents the results of the treatment of a textile wastewater by EC process. Two electrode materials, aluminum and iron, were connected in three modes namely, monopolar-parallel (MP-P), monopolar-serial (MP-S), and bipolar-serial (BP-S). COD and turbidity removals were selected as performance criteria. For a high COD removal, acidic medium is preferable for both electrode materials. For a high turbidity removal, acidic medium is preferable for aluminum, and neutral medium for iron. High current density is favorable for both removals in the case of iron. In the aluminum case, the current density exhibits a pronounced effect on COD removal, depending strongly on the connection mode, but it has a negligible effect on the turbidity removal. MP-P with iron or MP-S with aluminum electrode are suitable configurations in regard with the overall process performance. Moreover, process economy is as important as removal efficiencies during the process evaluation task. Various direct and indirect cost items including electrical, sacrificial electrodes, labor, sludge handling, maintenance and depreciation costs have been considered in the calculation of the total cost. The results show that MP-P mode is the most cost-effective for both electrode types. Both electrodes show similar results in reducing COD and turbidity, but iron is preferred as a low cost material. Finally, a comparative study showed that EC was faster and more economic; consumed less material and produced less sludge, and pH of the medium was more stabilized than chemical coagulation (CC) for similar COD and turbidity removal levels. For CC, FeCl3 was the preferable salt in view of its techno-economic performance. On the other hand, iron was the preferred electrode material in EC with MP-P system in experimental conditions such as, 30 A m−2 of current density and 15 min of time, the treatment cost was $ 0.245 m−3. Consequently, the operating cost of CC was 3.2 times as high as the operating cost of EC.

This paper presents the comparative results with respect to electrode configurations on the economic performance of treatment of textile wastewaters by electrocoagulation (EC) process. Aluminum and iron electrode materials were used as sacrificial electrode in parallel and serial connection modes. Various direct and indirect cost items including electrical, sacrificial electrodes, labor, sludge handling, maintenance and depreciation costs were considered in the calculation of the total cost per m3 of wastewater taken from a textile plant with a capacity of 1000 m3 per day. The results showed that monopolar-parallel mode (MP-P) was the most cost-effective for Fe and Al electrodes. These electrodes showed similar results in removal efficiency of COD and turbidity, but Fe electrode was preferred due to its low cost. pH 7 for Fe electrode and pH 5 for Al electrode were found suitable in terms of removal efficiency of COD and turbidity from textile wastewater. Meanwhile, 30 A m−2 of current density and 15 min of operating time were found to be sufficient for Fe and Al electrodes. Finally, a comparative study showed that EC was faster and more economic; consumed less material and produced less sludge, and pH of the medium was more stabilized as compared to chemical coagulation (CC) for percentage removal efficiency of COD and turbidity from textile wastewater. The treatment cost of EC at optimum conditions was 3.2 times cheaper than that of CC.

Electrocoagulation (EC) is assessed by a preliminary technical and economic analysis for the treatment of poultry slaughterhouse wastewater (PSW). Chemical oxygen demand (COD) and oil-grease removal efficiencies, and total operating cost have been used for analysis purpose. Various direct and indirect cost items including electrical, sacrificial electrodes, labor, sludge handling, maintenance and depreciation costs have been considered in the calculation of the total cost. Iron and aluminum have been tested as sacrificial electrode material. Initial pH, current density and operating time were investigated as process variables. The experiments demonstrated the effectiveness of EC for the treatment of PSW. Aluminum electrode performed better in reducing the COD, with a removal efficiency as 93% in 25 at low initial pH, such as 3, and current density of 150 A/m 2 . On the other hand, iron electrode was more successful in removing oil-grease with 98% efficiency, irrespective of the initial pH. From economic point of view, iron electrode is clearly preferable; the total operating cost is between 0.3 and 0.4 $/m 3 , which is nearly half that of aluminum electrode. The total operating costs may also been calculated on the basis of $/kg COD removed, which are 0.015 and 0.027 for iron and aluminum electrodes, respectively.

Surface roughness is one of the most important requirements in machining process. The surface roughness value is a result of the tool wear. When tool wear increase, the surface roughness also increases. The determination of the sufficient cutting parameters is a very important process obtained by means of both minimum surface roughness values and long tool life. The statistical models were developed to predict the surface roughness. This paper presents the development of a statistical model for surface roughness estimation in a high-speed flat end milling process under wet cutting conditions, using machining variables such as spindle speed, feed rate, depth of cut, and step over. First- and second-order models were developed using experimental results of a rotatable central composite design, and assessed by means of various statistical tests. The highest coefficient of correlation (Radj2) (88%) was obtained with a 10-parameter second-order model. Meanwhile, a time trend was observed in residual values between model predictions and experimental data, reflecting the probable effect of the tool wear on surface roughness. Thus, in order to enhance the estimation capability of the model, another independent variable was included into the model to account for the effect of the tool wear, and the total operating time of the tool was selected as the most suitable variable for this purpose. By inserting this new variable as a linear term into the model, Radj2 was increased to 94% and a good fit was observed between the model predictions and supplementary experimental data. In this study, it was observed that, the order of significance of the main variables is as X 5 > X 3 > X 4 > X 1 > X 2 (total machining time, depth of cut, step over, spindle speed and feed rate, respectively).

Air pollution is a growing problem arising from domestic heating, high density of vehicle traffic, electricity production, and expanding commercial and industrial activities, all increasing in parallel with urban population. Monitoring and forecasting of air quality parameters in the urban area are important due to health impact. Artificial intelligent techniques are successfully used in modelling of highly complex and non-linear phenomena. In this study, adaptive neuro-fuzzy logic method has been proposed to estimate the impact of meteorological factors on SO2 and total suspended particular matter (TSP) pollution levels over an urban area. The model forecasts satisfactorily the trends in SO2 and TSP concentration levels, with performance between 75-90% and 69-80 %, respectively. © 2005 Elsevier Ltd. All rights reserved., 2002-45-10-16, This study was supported by Zonguldak Karaelmas University, research Grant no. 2002-45-10-16.

The decolorization of the levafix orange textile dye in aqueous solution by electrocoagulation using aluminum sacrificial anode has been investigated. The process performance is analyzed in terms of decolorization efficiency and the important cost-related parameters such as electrode and energy consumptions, as a function of initial pH, conductivity, current density, initial dye concentration and electrolysis time. The present study proves the effectiveness of electrochemical treatment for the textile dye solution. 95% decolorization efficiency may be obtained at suitable operating conditions such as; current density 100 A/m 2 , operating time 12 min and initial pH 6.4. The corresponding electrode and energy consumptions during the electrolysis were found to be 1.8 kg Al/kg dye and 35 kWh/kg dye.

This study takes aim at exploring the effectiveness of a surfactant-added powdered activated carbon/microfiltration (PAC/MF) hybrid process in the removal of nickel ions from water and wastewater a...

Electrocoagulation (EC) due to some advantages over chemical coagulation is becoming a popular process to be used for wastewater treatment. The aim of this paper is to investigate the effect of initial addition of a chemical coagulant such as polyaluminum chloride (PAC) or alum on the COD removal efficiency of EC treatment of textile wastewaters. The two salts exhibited the same performance in chemical coagulation, but in the combined electrocoagulation (CEC), PAC was found to significantly enhance the COD removal rate and efficiency, depending on the amount of the total aluminum supplied, by initial addition and electrochemical generation. A comparative operating cost analysis was also given and it was found that with the same operating cost per mass of COD removed, CEC performance was 80%, in contrast to 23% with EC, in 5 min of operation.

The photocatalytic degradation of aqueous solution of a commercial azo-reactive textile dye, Remazol Red F3B, has been investigated in a batch slurry reactor, in the presence of ZnO catalyst using two different UV light sources emitting at 254 nm and 365 nm. The effects of various process variables on degradation performance of the process have been investigated. The results showed that decolourization and total organic carbon (TOC) removal are both affected in the same manner by the solution pH in the pH range 6-10, showing maxima at pH 7 and pH 10. They are inversely related to the dye concentration, they increase in power-law with the light intensity. Decolourization is faster with 365 nm UV. TOC removal is not affected by UV wavelength in the initial period up to 20 min, after which it progresses faster under 365 nm UV radiation. These results indicate that the UV wavelength influences especially the degradation rate of the intermediate products generated during the initial period of the photocatalytic process. Finally, catalyst loading affects both efficiencies in the same trend, which are maximized at about 2 g/l catalyst loading.

Thiourea leaching of precious metals such as gold and silver from ores has several advantages when compared with conventional cyanidation process. In recent years, the use of ultrasound in leaching processes is becoming increasingly popular in hydrometallurgy. This paper deals with combining these two techniques for silver leaching from solid waste of a cyanidation leach plant located in Kutahya, Turkey. The primary aim of this research is to assess the technical performance of the method. To achieve maximum leaching yield, eight process variables have been selected to estimate optimum process conditions by means of statistical factorial design and steepest ascent techniques. Laboratory-scale experiments showed that complete leaching of silver may be achieved by this process.

The photocatalytic decolorization of aqueous solutions of Remazol Red RR, a commercial azo-reactive textile dye, in the presence of various semiconductor powder suspensions has been investigated in a quartz batch reactor with the use of artificial light sources (UV-C). ZnO and TiO2 have been found the most active photocatalysts; however ZnO indicated slightly higher efficiency. The effects of various process variables on decolorization performance of the process have been investigated. The results showed that the decolorization efficiency increases with increase in pH, attaining maximum value at pH 10 for ZnO. The zero-point charge for ZnO is 9.0 above which ZnO surface is negatively charged by adsorbed OH− ions, favoring the formation of strong oxidant OH radicals. The efficiency is inversely related to the dye concentration; increasing dye concentration enhances dye adsorption on the active sites of the catalyst surface, and consequently hinders OH− adsorption on the same sites, this results with a decreasing OH formation rate.