Vol 38, No 1 (2016)

Investigated are processes of sorption–desorption of Cr(IV) on model to the efficiency of desorption of Cr(VI) from the sorbent reagents are arrange in the series (NaOH: Na₂CO₃) > NaOH > Na₂CO₃ ≥ H₂CO₃ ≥ H₂SO₄. Calcined Zn/Al–hydrotalcite has been proposed for concentration of Cr(VI) and its spectrophotometric determination in natural waters.

The article addresses a practicable and economic low-temperature method of TiO₂ synthesis, which allows us in a specific manner to influence structure-sorption characteristics and photocatalytic activity of samples not at the expense of the change of temperature of finite treatment, but rather by way of varying additions of the precipitant and modifier. This method helped obtain nanodisperse TiO₂ with a developed specific area of the surface and high photocatalytic activity with respect to dyes of the anionic and cationic types. Individually obtained TiO₂ samples display activity even higher than commercial products.

The pathway of phenol degradation by electrochemical oxidation was studied in an aqueous solution using AISI 304 stainless steel electrodes. The increase in pH due to the generation of NaOH in the aqueous solution was found to be critical for the proposed degradation mechanism since the deprotonation of phenol occurs at pH 10. The phenoxy anion produced as a result of deprotonation is resonance stabilized. The Fe⁺³ ions (Lewis catalyst) released from the stainless steel anode and the chlorine gas formed by the electrolysis of sodium chloride are found to be responsible for the chlorination of phenoxy anion ensuing the formation of 2-, 4-, 6-substituted chlorophenols. The mechanism was proposed for elucidating the possible degradation pathway of phenol under the above specified conditions.

Pyrocarbon modification of microfiltration ceramic membrane from aluminum oxide by carbonization of polyisocyanate has been carried out. The structure of pyrocarbon was regulated by means of water, glycerin and nickel chloride. Water of purified of dyes by pressure-driven method at the pressure in the range 0.5–1.1 MPa. The retention coefficient and specific capacity of modified membranes for direct scarlet varies respectively from 84.3 to 99.99% and from 0.8 to 32.5 dm³/(m²•h) and brilliant green—from 45 to 99.99% and from 2.5 to 8.8 dm³/(m²•h) and they are determined not only by working pressure, but the structure of pyrocarbon too.

Investigated are working characteristics of reverse-osmotic membranes of low pressure ESPA-1 and TFC-75 in purifying aqueous solutions of phosphates in the range of their concentrations 10–490 mg/dm³. It is shown that at minor difference of selectivity of studied membranes with respect to phosphate–ions the specific capacity of the membrane ESPA-1noticeably exceeds such of the membrane TFC-75.

Experiments on bacterial leaching of heavy metals from aerobically stabilized surplus activated sludge at the Bortnichi aeration plant in Kiev have been conducted with addition of FeSO₄ • 7H₂O as a stimulant of iron-oxidizing bacteria. The mechanism of heavy metal leaching involving the ferrous iron oxidation by bacteria with subsequent formation of Fe(OH)₃ was confirmed. This process is accompanied by the reduction of pH level of wastewater sludge that results in leaching of heavy metals.

The use of biotesting for quality assessment of different waters. This method consists in determining the action of toxicants on specially selected organisms under standard conditions with registration of changes at behavioral, physiological, cellular and subcellular levels. A micronucleus test and Arneth’s formula as a biomarker were proposed for an optimal set used to determine specific structural and functional changes in the cell genome caused by toxic effects. A particular attention was paid to assessing the risk to human health of those factors and substances, the genotoxicity and cytotoxicity of which can be identified by using biomarkers of plant and animal cells.