DFT Study of the Molecular and Electronic Structure of Metal-Free Tetrabenzoporphyrin and Its Metal Complexes with Zn, Cd, Al, Ga, In

The electronic and molecular structures of metal-free tetrabenzoporphyrin (H2TBP) and its complexes with zinc, cadmium, aluminum, gallium and indium were investigated by density functional theory (DFT) calculations with a def2-TZVP basis set. A geometrical structure of ZnTBP and CdTBP was found to possess D4h symmetry; AlClTBP, GaClTBP and InClTBP were non-planar complexes with C4v symmetry. The molecular structure of H2TBP belonged to the point symmetry group of D2h. According to the results of the natural bond orbital (NBO) analysis, the M-N bonds had a substantial ionic character in the cases of the Zn(II) and Cd(II) complexes, with a noticeably increased covalent contribution for Al(III), Ga(III) and In(III) complexes with an axial –Cl ligand. The lowest excited states were computed with the use of time-dependent density functional theory (TDDFT) calculations. The model electronic absorption spectra indicated a weak influence of the nature of the metal on the Q-band position.

Influence of the structure of titenium phosphate on sorption properties

The process of sorption of lead, zinc, cadmium and cobalt ions from aqueous solutions on titanium-containing sorbents of various compositions is studied. Langmuir, Freundlich and Temkin models were used to determine sorption equilibrium. It was found that the process of sorption of metal ions on sorbents is described with the maximum probability by the Langmuir equation. The data obtained made it possible to determine the affinity of the metal to the sorbent and to compose a selectivity series.

EFFECT OF LONG-TERM USE OF MINERAL FERTILIZERS FOR AGROCHEMICAL PROPERTIES SOD-PODZOLIC SOIL OF HAYFIELD

The effect of long-term use of mineral fertilizers on the accumulation of heavy metals in soils of various compositions is an urgent problem in the Non-Chernozem zone of Russia. The main objective of the research conducted at the Federal Williams Research Center of Forage Production and Agroecology was to determine the effect of long-term use of mineral fertilizers on agrochemical soil parameters and accumulation of heavy metals. Systematic application of mineral fertilizers on the sod-podzolic loamy soil of hayfield for 74 years has not had a negative impact on its agrochemical indicators. On the contrary, the organic matter content increased by 30-40% according to the experimental variants. The acidity of the soil decreased from a pH of 4.3 to 4.5–5.3. The effect of mineral fertilizers on the content of mobile forms of copper, zinc, cadmium, lead in the soil and their accumulation in plants is shown. Analysis of the soil by layers showed that 15–20% more humus, mobile macroelements, microelements – copper, zinc are concentrated in the 0–10 cm layer. The content of toxic elements – cadmium and lead – was characterized by their uniform distribution over the 0–20 cm horizon. An annual balance calculation of the use of microelements supplied with mineral fertilizers to plants is presented. The obtained results showed that the forage grasses during the growing season fully used the copper, zinc, cadmium, lead introduced with mineral fertilizers and additionally consumed from the soil: copper – 68, zinc – 268, cadmium – 0.2, lead – 3 g/ha.

Formation and characterization of acid mine drainage in the Madzharovo ore field, Southeastern Bulgaria

The formation of acid mine drainage (AMD) is a serious environmental problem in areas with mining and processing industries worldwide. Their generation is associated with chemical and biological processes of oxidation of sulfide minerals, mainly pyrite. Sources of AMD can be deposits of sulfide minerals and coal with a high content of pyrite sulfur, mining waste and some tailings. The impact of AMD on surface and groundwater in mining areas continues for decades after the cessation of extraction. An example of the negative impact of generated acid mine drainage on the state of surface waters is in the region of Madzharovo. Years after the cessation of mining, the waters at the discharge points "Momina Skala", "Harman Kaya" and "Pandak Dere" are characterized by low pH values and high concentrations of iron, copper, zinc, cadmium, lead and manganese.

PLANTS AND MAXIMUM PERMISSIBLE CONCENTRATIONS OF HEAVY METALS IN SOIL

The tentative permissible concentrations and the maximum permissible concentration of heavy metals do not always give a complete adequate assessment of the effect on plants. Plant growth inhibition can be at concentrations below the maximum permissible concentrations and tentative permissible concentrations. We studied the effect of copper, zinc, cadmium, and lead concentrations on plants. The object of the research is the lawn grass, the Agrostis stolonifera used in urban greening. According to the data obtained, Agrostis stolonifera showed a low degree of resistance to copper, lower than the tentative permissible concentration and the maximum permissible concentration. Consequently, the tentative permissible concentration and the maximum permissible concentration do not fully reflect the real phytotoxicity of copper. Plants of Agrostis stolonifera demonstrated a relatively high sensitivity to zinc in comparison with the maximum permissible concentration and the tentative permissible concentration. The content of cadmium and lead corresponding to the tentative permissible concentrations did not have a significant effect on the plants.

Identification of white jewelry alloy based on silver and platinum for testing purposes

The procedure for the identification of white jewelry alloys based on precious metals, in particular, silver, platinum and platinum group metals with different contents of alloying components, by testing on an assay stone and by the method of X-ray fluorescence analysis has been considered. The methodology for assessing the compliance of silver and platinum fineness in white jewelry alloys of different component composition with the requirements of regulatory documents and the procedure for their identification has been improved. It has been established that the silver fineness in precious alloys of the AgCu, AgZnCu system, determined using the potassium dichromate reagent on the test stone, depends on the manifestation of the contrast of the qualitative reaction from the standard sample (assay needle). It has been proven that for testing silver alloys containing palladium, the "Acid reagent for gold 750" is effective, which works to determine the qualitative and approximate content of silver in alloys. It was determined that the reagent "Ferrous-cyanide potassium" is very sensitive to changes in the alloy composition of silver alloys and makes it possible to establish the silver content with an accuracy of 5 %. The presence in silver alloys of such impurities as zinc, cadmium, nickel, gold, palladium and others increases the error in determining the fineness of silver and forms a different color and shade. It has been proven that testing of silver alloys on an assay stone with silver nitrate is effective only for the СрМ system. The presence of zinc in 925 sterling silver alloys visually increases the color intensity of the sediment, which indicates a higher overestimated fineness. It has been found that the identification of the content of precious alloys based on platinum for the presence of ligature components is carried out with a potassium iodide reagent at t=120 °C by the color and shade of the sediment. The procedure for using potassium iodide during testing of precious platinum-based alloys has been optimized

Physicochemical and Heavy Metal Assessment of the Udu River, Delta State, Nigeria

The Udu River is a major source of commerce and provides water for agricultural and domestic use to the Udu people, hence we studied the physicochemical parameters (pH, electrical conductivity, TSS, TDS, turbidity, Salinity, DO, COD, BOD, chlorides, sodium, potassium, total hardness, alkalinity, nitrates, ammonium, sulphates) as well as the evaluation of the degree of metal contamination (iron, zinc, cadmium, nickel, copper and lead) present in the samples. The analyses carried out revealed water samples were acidic, pH below 7, temperature ranged from 29.5 oC - 32.7 oC which was above WHO permissible limit 25oC, low levels of Dissolve oxygen DO (DO: max = 6.5 mg/L below WHO limit of 7.5 mg/L) and BOD ranges did not exceed the suggested 4.5mg/L (WHO max. limit). Concerning the heavy metals, the examined results showed lead, nickel, copper and zinc all below the WHO max limit. A significant increase in the concentration of Iron was noticed in Ovwian sampling site, also there was also build of cadmium above WHO limit 0.003mg/L at Igbogidi.

Hysteresis of heavy metals uptake induced in Taraxacum officinale by thiuram

Dandelion (Taraxacum officinale) yields active substances frequently used in herbal medicinal preparations. Its plantations are exposed to fungal plagues which pose a threat to herbal crops. The aim of this study was to evaluate the long time effects of a fungicide thiuram on dandelion growth and photosynthesis. Additionally, the manganese, iron, copper, zinc, cadmium, and lead uptake and transport were also investigated. Plants were cultivated under greenhouse conditions by the pot method in a universal flowering soil. The elements content in soil and plants were determined by the HR-CS FAAS spectrometer. Thiuram concentrations were established by the HPLC. Those analyses showed that almost 80% of thiuram decomposed within two weeks of its application. The photosynthesis indicators suggested, that plants were in good conditions and the fungicide supplementation facilitated plant growth. The latter could be prompted by thiuram acting as a sulfur rich chemical micro fertilizer. The hypothesis, that thiuram significantly affects heavy metals interactions in dandelion was proved by the one-way analysis of variance. Notable, metals uptake did not completely recover after fungicide decomposition for all investigated elements except iron We suggest to define this chemically induced, time-dependent heavy metals migrations in the soil–plant system as hysteresis of heavy metals uptake.

Sorption of Co2+, Zn2+, Cd2+ and Cs+ ions by activated sludge of sewage treatment plant

Sludges are byproducts of sewage treatment process. Land application of sewage sludge is one of the final steps of waste water treatment, but solubilization of toxic metals restricts this method of sludge disposal. In our paper cobalt, zinc, cadmium and cesium sorption by suspension of non-treated activated sewage sludge (14 g/dm3, dry wt.) from waste water spiked with 60CoCl2, 65ZnCl2, 109CdCl2 or 137CsCl were determined in laboratory experiments at 20°C. Activated sludge supplied by the municipal sewage treatment plant in Zeleneč (Trnava region, Slovakia) showed high efficiency to sorb Co2+, Zn2+, Cd2+ and Cs+ ions from waste water pH 6-7. The process can be characterized by the concentration equilibrium (Csolid/Cliquid) typical for sorption processes. Efficiency of the sorption increased in the order Cs < Co < Zn < Cd. Metal sorption process was not inhibited by pretreatment of the sludge with 0.2% formaldehyde or thermal inactivation at 60°C, what confirms that the process was not dependent on metabolic activity of the sludge. Cobalt, zinc, cadmium and cesium were easily removable from the sludge by washing with diluted HCl, EDTA or water solutions of the corresponding metal ions, but with low efficiency by deionized water.