Chemical Engineering / Kimya Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/14
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Article Citation - WoS: 21Citation - Scopus: 23Activated Carbon Adsorption of Fuel Oxygenates Mtbe and Etbe From Water(Springer Verlag, 2009) İnal, Fikret; Yetgin, Senem; Aksu, Gülsüm T.; Şimşek, Selvi; Sofuoğlu, Aysun; Sofuoğlu, Sait CemilThe aqueous phase adsorption of fuel oxygenates methyl tertiary butyl ether (MTBE) and ethyl tertiary butyl ether (ETBE) onto commercially available granular activated carbon (GAC; Norit GAC 1240) was investigated in a batch system at 27°C. The oxygenate concentrations were determined by headspace gas chromatography/mass spectrometry analyses. The experimental data were used with four two-parameter isotherm models (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich) and two kinetic models (pseudo first-order and pseudo second-order) to determine equilibrium and kinetic parameters. Considering the correlation coefficient and root mean square error, Dubinin-Radushkevich isotherm showed better fit with the equilibrium data for MTBE. However, the performances of Langmuir and Dubinin-Radushkevich models were comparable for ETBE. The adsorption capacities were calculated as 5.50 and 6.92 mg/g for MTBE and ETBE, respectively, at an equilibrium solution concentration of 1 mg/L using Dubinin-Radushkevich isotherm. The differences between the model predictions and experimental data were similar for the pseudo first-order and pseudo second-order kinetic models. Gibbs free-energy changes of adsorption were found to be -22.59 and -28.55 kJ/mol for MTBE-GAC and ETBE-GAC systems, respectively, under the experimental conditions studied.Article Citation - WoS: 303Citation - Scopus: 336A Health Risk Assessment for Exposure To Trace Metals Via Drinking Water Ingestion Pathway(Elsevier Ltd., 2009) Kavcar, Pınar; Sofuoğlu, Aysun; Sofuoğlu, Sait CemilA health risk assessment was conducted for exposure to trace metals via drinking water ingestion pathway for Province of İzmir, Turkey. Concentrations of 11 trace metals were measured in drinking waters collected from 100 population weighted random sampling units (houses). The samples were analyzed in atomic absorption spectrometry for arsenic, and inductively coupled plasma-optical emission spectrometry for Be, Cd, Co, Cr, Cu, Mn, Ni, Pb, V, and Zn. Questionnaires were administered to a participant from each sampling unit to determine drinking water consumption related information and demographics. Exposure and risks were estimated for each individual by direct calculation, and for İzmir population by Monte Carlo simulation. Six trace metals (As, Cr, Cu, Mn, Ni, and Zn) were detected in >50% of the samples. Concentrations of As and Ni exceeded the corresponding standards in 20% and 58% of the samples, respectively. As a result, arsenic noncarcinogenic risks were higher than the level of concern for 19% of the population, whereas carcinogenic risks were >10-4 for 46%, and >10-6 for 90% of the population.Article Citation - WoS: 74Citation - Scopus: 89Seasonal Variation in Drinking Water Concentrations of Disinfection By-Products in Izmir and Associated Human Health Risks(Elsevier Ltd., 2008) Baytak, Derya; Sofuoğlu, Aysun; İnal, Fikret; Sofuoğlu, Sait CemilSeasonal variation in concentrations of two different disinfection by-product groups, trihalomethanes (THMs) and haloacetonitriles (HANs), was investigated in tap water samples collected from five sampling points (one groundwater and four surface water sources) in İzmir, Turkey. Estimates of previously published carcinogenic and non-carcinogenic risks through oral exposure to THMs were re-evaluated using a probabilistic approach that took the seasonal concentration variation into account. Chloroform, bromoform, dibromochloromethane and dichloroacetonitrile were the most frequently detected compounds. Among these, chloroform was detected with the highest concentrations ranging from 0.03 to 98.4 μg/L. In tap water, at the groundwater supplied sampling point, brominated species, bromoform and dibromoacetonitrile, were detected at the highest levels most probably due to bromide ion intrusion from seawater. The highest total THM and total HAN concentrations were detected in spring while the lowest in summer and fall. The annual average total THM concentration measured at one of the surface water supplied sampling points exceeded the USEPA's limit of 80 μg/L. While all non-carcinogenic risks due to exposure to THMs in İzmir drinking water were negligible, carcinogenic risk levels associated with bromodichloromethane and dibromochloromethane were higher than one in million.Article Citation - WoS: 104Citation - Scopus: 115An Exposure and Risk Assessment for Fluoride and Trace Metals in Black Tea(Elsevier Ltd., 2008) Sofuoğlu, Sait Cemil; Kavcar, PınarExposure and associated health risks for fluoride and trace metals in black tea were estimated. Fifty participants were randomly recruited to supply samples from the tea that they drink, and self-administer a questionnaire that inquired about personal characteristics and daily tea intake. Analyzed trace metals included aluminum, arsenic, barium, cadmium, cobalt, chromium, copper, manganese, nickel, strontium, and zinc. Fluoride and four metals (Al, Cr, Mn, Ni) were detected in all samples while barium was detected only in one sample. The remaining metals were detected in >60% of the samples. Fluoride and aluminum levels in instant tea bag samples were greater than in loose tea samples (p < 0.05) while the differences in elemental concentrations of loose and pot bag tea samples were not significant. Median and 90th percentile daily tea intake rates were estimated as 0.35 and 1.1 l/day, respectively. Neither fluoride nor aluminum levels in black tea were found to associate with considerable risks of fluorosis and Alzheimer's disease, respectively. However, carcinogenic risk levels for arsenic were high; R > 1.0 × 10-6 even at the median level. According to sensitivity analysis, daily tea intake was the most influencing variable to the risk except for arsenic for which the concentration distribution was of more importance.Article Citation - WoS: 31Citation - Scopus: 37Application of Artificial Neural Networks To Predict Prevalence of Building-Related Symptoms in Office Buildings(Elsevier Ltd., 2008) Sofuoğlu, Sait CemilArtificial neural networks (ANN) were constructed to predict prevalence of building-related symptoms (BRS) of office building occupants. Six indoor air pollutants and four indoor comfort variables were used as input variables to the networks. A symptom metric was used as the measure of BRS prevalence, and employed as the output variable. Pollutant concentration, comfort variable, and occupant symptom data were obtained from the Building Assessment and Survey Evaluation study conducted by the US Environmental Protection Agency, in which all were measured concurrently. Feed-forward networks that employ back-propagation algorithm with momentum term and variable learning rate were used in ANN modeling. Root mean square error and R2 value of the simple linear regression between observed and predicted output were used as performance measures. Among the constructed networks, the best prediction performance was observed in a one-hidden-layered network with an R2 value of 0.56 for the test set. All constructed networks except one showed a better performance than the multiple linear regression analysis.Article Citation - WoS: 39Citation - Scopus: 48The Indoor Environmental Index and Its Relationship With Symptoms of Office Building Occupants(Taylor and Francis Ltd., 2004) Moschandreas, Demetrios J.; Sofuoğlu, Sait CemilAn index for indoor environmental quality, the Indoor Environmental Index (IEI), was developed. This study aggregates the Indoor Air Pollution Index, an index found in the literature, and a new index: the Indoor Discomfort Index. The average of these two indices is the IEI, which is calculated using concentrations of eight pollutants and two comfort variables measured in 100 office buildings in the United States. The database used was developed for the U.S. Environmental Protection Agency Building Assessment Survey Evaluation study. A symptom index also is developed to denote persistent occupant symptoms. The IEI and the symptom index are used to investigate the relationship between indoor environmental quality and symptoms. Two simple linear regression models were formulated; these models explain 67 and 79% of the variation in the average symptom index, with the variation of the average IEI depending on the method of averaging used in the construction of the models. In addition, a conceptual explanation is provided for the empirical or regression models formulated. The IEI and the associated models relating indoor environmental quality with the office occupant symptom index may be used as management tools, as illustrated with an example.Article Citation - WoS: 37The Link Between Symptoms of Off Ice Building Occupants and In-Office Air Pollution: the Indoor Air Pollution Index(Blackwell Publishing, 2003) Sofuoğlu, Sait Cemil; Moschandreas, Demetrios J.The lack of an effective indoor air quality (IAQ) metric causes communication concerns among building tenants (the public),buildi ng managers (decision-makers),and IAQ investigators (engineers). The Indoor Air Pollution Index (IAPI) is developed for office buildings to bridge this communication discord. The index, simple and easily understood,employ s the range of pollutant concentrations and concentrations in the subject building to estimate a unitless single number,the IAPI,between 0 (lowest pollution level and best IAQ) and ten (highest pollution level and worst IAQ). The index provides a relative measure of indoor air pollution for office buildings and ranks office indoor air pollution relative to the index distribution of the US office building population. Furthermore,the index associates well with occupant symptoms,pe rcentage of occupants with persistent symptoms. A tree-structured method is utilized in conjunction with the arithmetic mean as the aggregation function. The hierarchical structure of the method renders not only one index value,but also several sub-index values that are critical in the study of an office air environment. The use of the IAPI for IAQ management is illustrated with an example. The decomposition of the index leads to the ranking of sampled pollutants by their relative contribution to the index and the identification of dominant pollutant(s). This information can be applied to design an effective strategy for reducing in-office air pollution.Article Citation - WoS: 10Citation - Scopus: 14Exposure and Risk Estimates for Arizona Drinking Water(John Wiley and Sons Inc., 2003) Sofuoğlu, Sait Cemil; Lebowitz, Michael D.; O'Rouke, Mary Kay; Robertson, Gary L; Dellarco, Michael; Moschandreas, Demetrios J.As part of the National Human Exposure Assessment Survey, a multistage sampling was used to estimate and compare exposures and risks associated with drinking water for two groups - the population of Arizona and that of border communities. There had been some concern that the border communities' exposures would be higher than those of other parts of the state because of their proximity to Mexico, where environmental quality may not be as high a priority as it is in the United States. The two study populations were further categorized by gender, age, ethnicity, education, income, and building structure type and year of construction. For these subgroups, the study estimated and compared risks for arsenic, 1,3-butadiene, chloroform, chromium, 1,2-dichloroethane, dichloromethane, lead, nickel, and toluene. For almost all of the sample subjects, residue concentrations were below the drinking water guideline values of both Arizona and the US Environmental Protection Agency. Of the metals studied, arsenic was the only one with a population carcinogenic risk above the acceptable level of 1.0E-6. Contrary to expressed concerns, average daily exposures and associated risks were estimated to be smaller in the border communities than in the Arizona population. For utilities, one finding deserving further study was that risks from tap water were estimated to be greater than risks from nontap water. Further research may be warranted to uncover the causes for these elevated risks.Article Citation - WoS: 65Overall Elemental Dry Deposition Velocities Measured Around Lake Michigan(Elsevier Ltd., 2001) Yi, Seung-Muk; Shahin, Usama; Sivadechathep, Jakkris; Sofuoğlu, Sait Cemil; Holsen, Thomas M.Overall dry deposition velocities of several elements were determined by dividing measured fluxes by measured airborne concentrations in different particle size ranges. The dry deposition measurements were made with a smooth surrogate surface on an automated dry deposition sampler (Eagle II) and the ambient particle concentrations were measured with a dichotomous sampler. These long-term measurements were made in Chicago, IL, South Haven, MI, and Sleeping Bear Dunes, MI, from December 1993 through October 1995 as part of the Lake Michigan Mass Balance Study. In general, the dry deposition fluxes of elements were highly correlated with coarse particle concentrations, slightly less well correlated with total particle concentrations, and least well correlated with fine particle concentrations. The calculated overall dry deposition velocities obtained using coarse particle concentrations varied from approximately 12 cm s−1 for Mg in Chicago to 0.2 cm s−1 for some primarily anthropogenic metals at the more remote sites. The velocities calculated using total particle concentrations were slightly lower. The crustal elements (Mg, Al, and Mn) had higher deposition velocities than anthropogenic elements (V, Cr, Cu, Zn, Mo, Ba and Pb). For crustal elements, overall dry deposition velocities were higher in Chicago than at the other sites.Article Citation - WoS: 20Dry Deposition Fluxes and Atmospheric Size Distributions of Mass, Al, and Mg Measured in Southern Lake Michigan During Aeolos(Taylor and Francis Ltd., 1998) Sofuoğlu, Sait Cemil; Paode, Rajendra D.; Sivadechathep, Jakkris; Noll, Kenneth E.; Holsen, Thomas M.; Keeler, Gerald J.In this study, which was a part of the Atmospheric Exchange Over Lakes and Oceans Study (AEOLOS) investigation, the dry deposition fluxes and atmospheric size distributions (ASDs) of mass and crustal metals (aluminum and magnesium) were measured over the southern basin of Lake Michigan (in Chicago, over Lake Michigan, and in South Haven, Michigan). Airborne crustal metals arise primarily from fugitive dust emissions and are associated with the coarse fraction of atmospheric aerosol. Consequently, they can serve as fingerprints for the atmospheric behavior of fugitive dust. The flux of these metals were substantially higher in Chicago than in either South Haven or over Lake Michigan. The measured average mass, aluminum, and magnesium fluxes were 138, 2.23, and 5.32 mg/m2-day in Chicago, 47.8, 0.24, and 0.28 mg/m2-day over Lake Michigan, and 37.4, 0.17, and 0.12 mg/m2-day in South Haven, respectively. The ASDs of crustal metals measured in Chicago had higher concentrations of coarse particles than ASDs measured over Lake Michigan and in South Haven. The calculated flux of metals using a multistep model and dry deposition velocities obtained from the Sehmel-Hodgson model were in general agreement with measured fluxes of crustal metals. Particles >10 μm were found to be responsible for the majority of the flux.