Equilibrium partition of polycyclic aromatic hydrocarbons in a cloud-point extraction process

Vertical distribution of polycyclic aromatic hydrocarbons in the brackish sea water column: ex situ experiment

Background

Oil spills can cause severe damage within a marine ecosystem. Following a spill, the soluble fraction of polycyclic aromatic hydrocarbons is rapidly released into the water column. These remain dissolved in seawater over an extended period of time, even should the insoluble fraction be removed. The vertical distribution of the aromatic hydrocarbon component and how these become transferred is poorly understood in brackish waters. This study examines the vertical distribution of polycyclic aromatic hydrocarbons having been released from a controlled film of spilled oil onto the surface of brackish water.

Methods

The study was undertaken under controlled conditions so as to minimize the variability of environmental factors such as temperature and hydrodynamics. The distribution of polycyclic aromatic hydrocarbons was measured in the dissolved and suspended phases throughout the 1 m water column with different intensity of water sampling: 1, 2, 4, 7, 72, 120, 336, 504 and 984 h.

Results

The total concentration of polycyclic aromatic hydrocarbons ranged from 19.01 to 214.85 ng L^–1 in the dissolved phase and from 5.14 to 63.92 ng L^–1 in the suspended phase. These hydrocarbons were released immediately following a controlled spill attaining 214.9 ng L^–1 in the dissolved phase and 54.4 ng L^–1 in the suspended phase near the cylinder bottom after 1–2 h. The 2–3 ring polycyclic aromatic hydrocarbons dominated in the dissolved phase (60–80%), whereas the greater amount of 4–6 ring polycyclic aromatic hydrocarbons (55–90%) occurred in the suspended phase. A relatively low negative correlation (r_S = –0.41) was determined between the concentration of phenanthrene and suspended matter, whereas a high negative correlation (r =  − 0.79) was found between the concentration of pyrene and suspended matter. Despite the differences in the relationships between the concentration ratio and amount of suspended matter the obtained regressions allow roughly to predict the concentration of polycyclic aromatic hydrocarbons.

Easy Removal of Methylparaben and Propylparaben from Aqueous Solution Using Nonionic Micellar System

This study aimed to investigate the simultaneous removal of methylparaben (MePB) and propylparaben (PrPB) from effluents (each one at 16 mg/L) using a nonionic micellar system containing Triton X-114. Response surface methodology (RSM) has been carried out. Extraction results using nonionic surfactant two-phase system were considered as a function of surfactant concentration and temperature variation. Four responses were investigated: MePB and PrPB extraction yield (E), solute (Xs,w) and surfactant (Xsf,w) concentrations in the aqueous phase and the volume fraction of micellar phase (ϕC) at equilibrium. Very high extraction efficiencies (99 % for PrPB and 84 % for MePB) were achieved at optimal conditions. Thereby, the amounts of PrPB and MePB were reduced 80 and 5 times, respectively. The extraction improvement using sodium sulfate was also shown. Finally, the solute stripping from micellar phase by pH change was proved.

Cloud point extraction of parabens using non-ionic surfactant with cylodextrin functionalized ionic liquid as a modifier

A cloud point extraction (CPE) process using non-ionic surfactant (DC193C) to extract selected paraben compounds from water samples was investigated using reversed phase high performance liquid chromatography (RP-HPLC). The CPE process with the presence of β-cyclodextrin (βCD) functionalized ionic liquid as a modifier (CPE-DC193C-βCD-IL) is a new extraction technique that has been applied on the optimization of parameters, i.e., pH, βCD-IL concentration and phase volume ratio. This CPE-DC193C-βCD-IL method is facilitated at 30 °C, showing great losses of water content in the surfactant-rich phase, resulting in a high pre-concentration factor and high distribution coefficient. The developed method CPE-DC193C-βCD-IL did show enhanced properties compared to the CPE method without the modifier (CPE-DC193C). The developed method of CPE-DC193C-βCD-IL gives an excellent performance on the detection of parabens from water samples with the limit of detection falling in the range of 0.013-0.038 µg mL-1. Finally, the inclusion complex formation, hydrogen bonding, and π-π interaction between the βCD-IL, benzyl paraben (ArP), and DC 193C were proven using 1H NMR and 2D NOESY spectroscopy.

Cloud-point preconcentration and spectrophotometric determination of trace amounts of molybdenum(VI) in steels and water samples

A cloud-point extraction process using micelle of the cationic surfactant CTAB to extract Mo(VI) from aqueous solutions was investigated. The method is based on the color reaction of molybdenum with bromopyrogallol red in the presence of potassium iodide at pH 1.0 glycine/HCl buffer media and micelle-mediated extraction of complex. The optimal extraction and reaction conditions (e.g., surfactant concentration, reagent concentration and effect of time) were studied and the analytical characteristics of the method (e.g., limit of detection, linear range, preconcentration and improvement factors) were obtained. Linearity was obeyed in the range of 0.3-320.0 ng mL(-1) of molybdenum(VI) ion and the detection limit of the method was 0.1 ng mL(-1). The relative standard deviation (R.S.D.) and relative error for five replicate measurements of 65.0 ng mL(-1) Mo(VI) were 1.1% and 1.9%, respectively. The interference effect of some anions and cations was also tested. The method was applied to the determination of molybdenum(VI) in steels and tap water and well water samples.

Continuous-flow microextraction and gas chromatographic–mass spectrometric determination of polycyclic aromatic hydrocarbon compounds in water

A new method of the determination polycyclic aromatic hydrocarbons (PAHs) in water samples was developed by continuous-flow microextraction (CFME) coupled with gas chromatography-mass spectrometry (GC-MS). In this experiment, 15 mL sample solution with no salt-added was flowed at the rate of 1.0 mL min(-1) through 3 microL benzene as extraction solvent. Under the optimal extraction conditions, the developed method was found to yield a linear calibration curve in the concentration range from 0.05 to 15 ng mL(-1). Furthermore, the accuracy and repeatability of the method were good by calculating from water samples spiked at known concentrations of PAHs, and the recovery of optimal method was satisfactory. The results showed that CFME was an efficient preconcentration method for extraction of PAHs from spiked water samples.

Cloud point extraction coupled with HPLC-UV for the determination of phthalate esters in environmental water samples

A method based on cloud point extraction was developed to determine phthalate esters including di-ethyl-phthalate (DEP), di-(2-ethylhexyl)-phthalate (DEHP) and di-cyclohexyl-phthalate (DCP) in environmental water samples using high-performance liquid chromatography separation and ultraviolet detection (HPLC-UV). The non-ionic surfactant Triton X-114 was chosen as extraction solvent. The parameters affecting extraction efficiency, such as concentrations of Triton X-114 and Na2SO4, equilibration temperature, equilibration time and centrifugation time were evaluated and optimized. Under the optimum conditions, the method can achieve preconcentration factors of 35, 88, 111 and detection of limits of 2.0, 3.8, 1.0 ng/ml for DEP, DEHP and DCP in 10-ml water sample, respectively. The proposed method was successfully applied to the determination of trace amount of phathalate esters in effluent water of the wastewater treatment plant and the lixivium of plastic fragments.

Preconcentration and fluorimetric determination of polycyclic aromatic hydrocarbons based on the acid-induced cloud-point extraction with sodium dodecylsulfate

The acid-induced cloud-point extraction (CPE) technique based on sodium dodecylsulfate (SDS) micelles has been used for preconcentration of ten representatives of polycyclic aromatic hydrocarbons (PAHs) for the following fluorescence determination. The effect of the acidity of solution, SDS and electrolyte concentrations, centrifugation time and rate on the two-phase separation process and extraction percentages of PAHs have systematically been examined. Extraction percentages have been obtained for all PAHs after CPE ranged from 67 to 93%. Pyrene was used as a fluorescent probe to monitor the micropolarity of the surfactant-rich phase compared with SDS micelles and this allows one to conclude that water content in micellar phase after CPE is reduced. The spectral, metrological and analytical characteristics of PAH fluorimetric determination after acid-based CPE with sodium dodecylsulfate are presented. Advantages provided by using CPE in combination with fluorimetric determination of PAHs are discussed. The determination of benz[a]pyrene in tap water is presented as an example.