G. Kamińska

Kinetics and equilibrium of the sorption of bisphenol A by carbon nanotubes from wastewater

The aim of this study was to determine the sorption potential of carbon nanotubes (CNTs) to bisphenol A (BPA) contained in synthetic wastewater whose composition corresponds to biologically treated effluents. These nanotubes differed in their outer diameter, the number of graphene layers and the presence of modifying functional groups. Based on the nitrogen adsorption-desorption isotherms, mensuration of the specific surface area and pore size distribution was undertaken. The porous structure of the CNTs was bidispersive; the majority consisted of micropores, there was an average fraction of mesopores, and macropores did not occur. On the basis of common kinetics models (pseudo-first-order and pseudo-second-order models), a trial of modelling the kinetics of BPA sorption onto nanotubes was undertaken. The experimental data were well fitted only to the pseudo-second-order models. The kinetics study indicated that adsorption of BPA on CNTs proceeded very fast, with the majority of the adsorbate being adsorbed in the first few seconds. The sorption capacity of nanotubes to BPA was the highest for single-walled CNTs. A decrease in the sorption potential of the nanotubes for higher pH values occurred as a result of the deprotonation of the BPA and formation of bisphenolate anions, consequently leading to a decrease of π-π (hydrophobic) interaction and enhancing electrostatic repulsion. Overall, these results unequivocally confirm the ideal performance and potential of nanotubes for removal of micropollutants from synthetic wastewater. Replicating the conditions occurring in real wastewater allows us to expect a high sorption of BPA in real competitive sorption systems.

Polyacrylonitrile membranes modified with carbon nanotubes: characterization and micropollutants removal analysis

AbstractThe phase inversion method was used to prepare polyacrylonitrile membranes modified with single-walled carbon nanotubes. The influence of the amount and the kind of carbon nanotubes (CNTs) (pristine and functionalized with carboxyl groups) were determined analysing the structure of membranes, hydrophobic–hydrophilic characteristics, zeta potential, and transport-separation properties. Based on the microscopic analysis, it was established that their structure changed depending on the amount of nanotubes added. The membranes with the highest content of CNTs were characterized by the highest membrane capacity. Those membranes were used in low pressure filtration in order to remove micropollutants from synthetic wastewater. The effectiveness of micropollutants removal was dependant on the kind of membrane—in the range 15–65% for bisphenol A, and 25–87% for nonylphenol. The key mechanism in separation of low molecular organic compounds was the sorption phenomenon intensified by the presence of CNTs.

Chromatographic determination and toxicological potential evaluation of selected micropollutants in aquatic environment—analytical problems

AbstractIn this study, the analytical procedures for the improved extraction and determination of the selected micropollutants (anthracene, pentachlorophenol, octylphenol, benzo(a)pyrene, and diclofenac) in aqueous environment are proposed. These methods were based on application of gas chromatography coupled with mass spectrometry and solid phase extraction for isolation of tested analytes from water samples. Compared to standard procedures currently used in the range presented in this paper, the authors’ modifications of analytical procedures allowed increasing the recovery rate of analytes. Within modification of procedures, hyamine, methanol were used. The substances increase solubility of analytes in water, for instance. Toxicological potential of samples containing tested micropollutants in different environmental matrix was evaluated. Proposed analytical procedures allow the quantitative determination of five different compounds in aquatic environment with satisfactory repeatability and precision o...

INFLUENCE OF INORGANIC COMPOUNDS ON THE PROCESS OF PHOTOCATALYSIS OF BIOLOGICALLY ACTIVE COMPOUNDS

Constant increase in concentration of organic micropollutants in the water environment influences the development of methods for their effective elimination from various matrices released into aquatic ecosystems. One of widely described in literature processes for the decomposition of hardly-biodegradable pollutants is the process of heterogeneous photocatalysis. The paper presents the influence of inorganic substances on the decomposition of polycyclic aromatic hydrocarbons (anthracene and benzo[a]pyrene), industrial admixtures – octylphenol and pharmaceutical compounds – diclofenac in the photocatalysis process conducted in the presence of TiO2. It has been shown that the presence of Cl– ions did not affect the photochemical reaction of the micropollutant decomposition. Whereas, the presence of CO3, SO4 and HPO4 ions inhibited the decolonization of octylphenol and diclofenac, while the degradation efficiency of anthracene and benzo[a]pyrene was reduced only by the presence of CO3 and HCO3 anions. The photooxidation of micropollutants in solutions containing Al3+ oraz Fe3+ cations proceeded with a much lower efficiency than that for solution without inorganic compounds. The analysis of the kinetics of the photocatalytic decomposition of selected micropollutants show a decrease in the reaction rate constant and an increase in their half-life due to the blocking of theactive semiconductor centers by inorganic compounds. In addition,the toxicological analysis inducated the generation of micropollutant oxidation by-products, which aggravate the quality of treated aqueous solutions.

REMOVAL OF ANTROPOGENIC ORGANIC MICROPOLLUTANTS FROM DIFFERENT WATER STREAMS IN THE FK/UF/NF SEQUENTIAL SYSTEM

A significant number of anthropogenic organic micropollutants are classified as hardlyor non-biodegradable compounds, which may adversely affect the living organisms, including human health. Municipal wastewater and wastewater from various industry sectors are considered as the main source of this type of pollutants. The aim of the conducted study was to develop a method for the removal of selected micropollutants such as diclofenac, octylphenol, anthracene and benzo[a]pyrene from various water streams, based on advanced oxidation processes and membrane filtration techniques. The research was carried out on solutions prepared on the basis of deionised water as well as a model and actual effluent from a mechanical-biological wastewater treatment line. The concentration of micropollutions was 0.5 mg/dm3. Photocatalytic oxidation was applied in the presence of TiO2 in a batch reactor equipped with a 150 W UV lamp. The post-processing solutions ware subjected to the ultrafiltration process, which allowed for the separation of catalyst particles and retention of high molecular weight organic compounds occurring in the treated water streams. The membrane filtration process was operated in a dead-end mode at a transmembrane pressure of 0.2 MPa. For their complete elimination, the second stage of membrane filtration using a nanofiltration membrane was applied. The chromatographic analysis, performed to determine the removal Received: 2017.04.30 Accepted: 2017.06.15 Published: 2017.08.01

SKUTECZNOŚĆ USUWANIA WYBRANCYH SUBSTANCJI AKTYWNYCH BIOLOGICZNIE PODCZAS MECHANICZNO-BIOLOGICZNEGO OCZYSZCZANIA ŚCIEKÓW

This study presents the results of monitoring some of the priority emerging substances (anthracene, benzo[a]pyrene, octylphenol, nonylphenol) in raw, primary treated and secondary treated wastewater from 3 WWTPs located in Silesia. The assay procedure of the compounds included the separation of substances from sewage samples by solid phase extraction and chromatographic analysis with GC-MS. Based on calculated concentration of given compounds, their total removal degree was determined. Among studied compounds the highest concentration in raw sewage was reported for anthracene and benzo[a]pyrene, while concentration of nonylphenol and octylphenol was 15 times lower. This trend was observed for all three studied WWTPs. It was also found that wastewater from the WWTPs of highest capacity was about 2 times higher in relation to the wastewater collected from smaller plants. The total removal efficiency of the studied compounds during two stage treatment was in the range of 17.5 to 100%.