Development and validation of a HPLC method for the determination of benzo(a)pyrene in human breast milk

A simple analytical procedure was developed for the quantitation of benzo(a)pyrene in human breast milk using solid phase extraction (SPE) combined with high performance liquid chromatography. Before the chromatographic process, SPE, including C18 functional groups in silicagel cartridges, was conducted for sample preparation. A C18 column (100×4.6 mm id, 3 μm particle size) was used with acetonitrile:water (80:20) as the mobile phase at a flow rate 1mL/min at 30°C. Fluorimetric detection was performed for excitation and emission at 290 and 406 nm, respectively. It was observed that the calibration curve was linear over the range of 0.5–80 ng/mL. The limit of detection and limit of quantitation were found to be 0.5 and 1.07 ng/mL, respectively. Intraday and interday relative standard deviation values were less than 5.15%. Moreover, the newly developed method provides a fast, simple, cost effective, and sensitive assay to detect an important carcinogen substance, benzo(a)pyrene, in human breast milk.     

Evaluation of continuous mesophilic anaerobic sludge digestion after high temperature microwave pretreatment

Effect of microwave pretreatment (MW) high temperature (175 °C) and MW intensity to waste activated sludge digested with acclimatized inoculum in single- and dual-stage semi-continuous mesophilic anaerobic digesters at different sludge retention times (SRTs) (20, 10 and 5 days) were investigated. MW pretreatment led to similar sludge stabilization at low SRTs (5 and 10 days). Although lowering MW intensity slightly improved sludge solubilization, it had a negative effect on digestion at low SRTs. Single-stage digesters with MW pretreatment surpass dual-stage digesters performances.     

Advanced oxidation of raw and biotreated textile industry wastewater with O3, H2O2 /UV‐C and their sequential application

The advanced chemical oxidation of raw and biologically pretreated textile wastewater by (1) ozonation, (2) H₂O₂ /UV − C oxidation and (3) sequential application of ozonation followed by H₂O₂ /UV − C oxidation was investigated at the natural pH values (8 and 11) of the textile effluents for 1 h. Analysis of the reduction in the pollution load was followed by total environmental parameters such as TOC, COD, UV–VIS absorption kinetics and the biodegradability factor, f_B. The successive treatment combination, where a preliminary ozonation step was carried out prior to H₂O₂ /UV − C oxidation without changing the total treatment time, enhanced the COD and TOC removal efficiency of the H₂O₂ /UV − C oxidation by a factor of 13 and 4, respectively, for the raw wastewater. In the case of biotreated textile effluent, a preliminary ozonation step increased COD removal of the H₂O₂ /UV − C treatment system from 15% to 62%, and TOC removal from 0% to 34%. However, the sequential process did not appear to be more effective than applying a single ozonation step in terms of TOC abatement rates. Enhancement of the biodegradability factor (f_B) was more pronounced for the biologically pretreated wastewater with an almost two‐fold increase for the optimized Advanced Oxidation Technologies (AOTs). For H₂O₂ /UV − C oxidation of raw textile wastewater, apparent zero order COD removal rate constants (k_app), and the second order OH· formation rates (r_i) have been calculated. © 2001 Society of Chemical Industry     

The development, validity and reliability of TPACK-deep: A technological pedagogical content knowledge scale

The purpose of this study is to develop a TPACK (technological pedagogical content knowledge) scale based on the centered component of TPACK framework in order to measure preservice teachers’ TPACK. A systematic and step-by-step approach was followed for the development of the scale. The validity and reliability studies of the scale were carried out with 995 Turkish preservice teachers. The sample was split into two subsamples on random basis (n1 = 498, n2 = 497). The first sample was used for Exploratory Factor Analysis (EFA) and the second sample for Confirmatory Factor Analysis (CFA). After the EFA, the TPACK-deep scale included 33 items and had four factors. These factors were design, exertion, ethics and proficiency. The Cronbach’s alpha coefficient for the whole scale was found to be .95, whereas the values of Cronbach’s alpha coefficient for individual factors of the scale ranged between .85 and .92. The CFA was conducted within the scope of the validity study of the scale. In this way, this structure of the 4-factor scale was confirmed. In addition, the test-retest reliability coefficient of the scale was calculated as .80. The findings revealed that the TPACK-deep scale was a valid and reliable instrument for measuring TPACK. Consequently, various suggestions were put forward regarding the use the TPACK-deep scale for applied research and for future studies.     

Advanced oxidation of a reactive dyebath effluent: comparison of O3, H2O2/UV-C and TiO2/UV-A processes

In the present study the treatment efficiency of different AOPs (O3/OH- H2O2/UV-C and TiO2/UV-A) were compared for the oxidation of simulated reactive dyebath effluent containing a mixture of monochlorotriazine type reactive dyes and various dye auxiliary chemicals at typical concentrations encountered in exhausted reactive dyebath liquors. A525 (color), UV280 (aromaticity) and TOC removal rates were assessed to screen the most appropriate oxidative process in terms of reactive dyebath effluent treatment. Special emphasis was laid on the effect of reaction pH and applied oxidant (O3, H2O2) dose on the observed reaction kinetics. It was established that the investigated AOPs were negatively affected by the Na2CO3 content (= 867 mg/L) which is always present at high concentrations in dychouse effluents since it is applied as a pH buffer and dye fixation agent during the reactive dyeing process. The ozonation reaction exhibited almost instantaneous decolorization kinetics and a reasonable TOC reduction rate. It appeared to be stable under the investigated advanced oxidation conditions and outranked the other studied AOPs based on the above mentioned criteria. Besides, the electrical energy requirements based on the EE/O parameter (the electrical energy required per order of pollutant removal in 1 m3 wastewater) was calculated for the homogenous AOPs in terms of decolorization kinetics. In view of the electrical energy efficiency, ozonation and H2O2/UV-C oxidation at the selected treatment conditions appear to be promising candidates for full-scale dyehouse effluent decolorization.     

COD, para-chlorophenol and toxicity removal from para-chlorophenol containing synthetic wastewater in an activated sludge unit

Chlorinated phenolic compounds present in some chemical industry wastewaters cause severe toxic effects on the organisms and often are resistant to biological degradation. Synthetic wastewater containing different concentrations of para-chlorophenol (4-chlorophenol, 4-CP) was biologically treated in an activated sludge unit for COD, 4-CP and toxicity removal. Effects of feed 4-CP concentration on COD, 4-CP, toxicity removals and on sludge volume index were investigated at a constant sludge age of 20 days and hydraulic residence time (HRT) of 25 h. Resazurin method based on dehydrogenase activity was used for determination of the toxicity of the feed and effluent wastewater. COD and 4-CP removals were not affected by the presence of 4-CP in the wastewater up to feed 4-CP concentration of 925 mg l(-1) because of almost complete degradation of 4-CP yielding lower than 50 mg l(-1) 4-CP in the aeration tank. Percent COD, 4-CP and toxicity removals decreased and the effluent COD, 4-CP and toxicity levels increased with further increases in the feed 4-CP concentrations above 925 mg l(-1) because of inhibitory concentrations of 4-CP in the reactor. Biomass concentration in the aeration tank decreased and the sludge volume index (SVI) increased with feed 4-CP concentrations above 925 mg l(-1) resulting in lower COD and 4-CP removal rates. The rates of COD and 4-CP removals indicated substrate (4-CP) inhibition for the feed 4-CP concentrations above 925 mg l(-1) corresponding to the reactor 4-CP of above 200 mg l(-1). The system should be operated at the feed 4-CP concentrations of less than 900 mg l(-1) (4-CP(R) < 200 mg l(-1)) in order to obtain high rates and extents of COD, 4-CP and toxicity removals at a sludge age of 20 days and HRT of 25 h.