Thin Al2O3 Coatings Produced by Electrochemical Method, Subjected to Thermo-Chemical Treatment

The article presents the effect of the anodizing parameters, as well as the thermo-chemical treatment, of Al2O3 layers produced on an aluminum alloy on the characterization of structure, geometrical structure of the surface (SGS), the thickness of the oxide layers, the phase composition, and their microhardness. The oxide layers were produced by the method of direct current anodizing in a three-component electrolyte. Then, thermo-chemical treatment was carried out in distilled water and aqueous solutions of sodium dichromate and sodium sulphate. The anodizing parameters and compounds for the thermo-chemical treatment were selected on the basis of Hartley’s plans. The research showed the effect of anodizing parameters on the thickness of the Al2O3 layers and the increase in the thickness of the layers as a result of the thermo-chemical treatment. The research showed a significant increase in the microhardness of the layers as a result of thermo-chemical treatment and its influence on the phase composition of Al2O3 layers. A significant influence of the thermo-chemical treatment on the geometrical structure of the surface was also found.

SYNTHESIS OF CHROME TANNING AGENT IN PRESENCE OF OLIGO - AND POLYSACCHARIDES

The conditions for the synthesis of chrome tanning agent during the reduction of sodium dichromate with oligo - and polysaccharides have been investigated. The synthesis of the tanning agent is based on the reduction of hexavalent chromium Cr (VI) in the form of sodium dichromate with reducing agents from the class of vegetable oligo- and polysaccharides with a different sequence of their introduction into the reaction mixture in the presence of sulfuric acid. The introduction of sulfuric acid was carried out gradually to avoid overheating and splashing of the reaction mixture, since the reduction reaction is accompanied by a significant thermal effect. Glucose, maltodextrin and pectin were used as reducing agents. The properties of the obtained products were evaluated by spectrophotometry, conductometry, and analytical methods. It has been shown that the use of native pectin leads to the formation of a gel like mass due to the coordination of the functional groups of galacturonic acid, which is part of the pectin, with chromium atoms. Pretreatment of pectin with a citric acid solution and optimization of synthesis conditions made it possible to obtain a chromium tanning agent that does not contain unreduced chromium. The influence of oligosaccharides on the properties of chromium tanning agents, including their ability to dissolve, is considered. It is shown that the reduction of sodium dichromate with maltodextrin during the reaction results in the formation of incomplete oxidation products of the oligosaccharide, which cause the masking effect of the chromium complex and increase in the resistance of the tanning agent to the action of alkaline reagents used to increase in the basicity during tanning. Experimental samples of chrome tanning agent in dry form were obtained and their leatherprocessing characteristics were studied. The results of technological tests have confirmed the theoretical propositions, according to which the high hydrothermal stability of the leather semifinished product, the almost complete depletion of the processing solution and the required physical and mechanical properties of the finished leather are achieved by introducing the products of incomplete oxidation of oligosaccharides into the inner sphere of the chromium complex.

Resorcin[4]arene Schiff base derivatives: Synthesis, characterization, and extraction studies

Novel 2,6-dihydroxyacetophenone[4]arene derivatives with an electron-withdrawing group at the ortho-position are developed. The 2,6-dihydroxyacetophenone[4]arene derivatives are condensed with benzylamine in chloroform to give the Schiff base derivatives of resorcin[4]arene. The acetyl group of the 2,6-dihydroxyacetophenone[4]arenes is condensed with primary amine groups to form imines. The multifunctional target molecules are purified and isolated in good yields. The Schiff base derivatives are characterized by elemental analysis, 1H and 13C nuclear magnetic resonance spectroscopy, infrared spectroscopy, and mass spectrometry. All the Schiff base compounds are successfully used for the extraction of toxic metals including Ni2+, Mn2+, Hg2+, Co2+, and Na+ using a liquid–liquid solvent extraction process. Among these tested metals, the percentage extraction of Hg2+ is the highest. As sodium dichromate has greater oxidative stability to transfer the HCr2O7− anion from an aqueous a protonated ligand solution, an anionic extraction study of dichromate is tested at various pH values.

Effects of Cadmium and /or Chromium on reproductive organs and semen profiles of male albino rats

Objective: To evaluate the potential hazards of cadmium and/or chromium on the reproductive system of adult male albino rat. Design: Randomized controlled study. Animals: Forty mature male albino rats weighing 260 ± 10 g. Procedures: Rats were allocated into four groups (ten animals each). Control group (group 1), group 2 received 4.4 mg kg-1 cadmium chloride, group 3 was given 2.5 mg kg-1 sodium dichromate and group 4 received combination of Cd (2.2 mg kg-1) and Cr (1.25mg kg-1) orally, once daily for 65 consecutive days. Results: Exposure to Cd or Cr, in particular their combination, caused a reduction in the index weights of testes, epididymis, seminal vesicle and prostate glands. They induced a reduction of sperm count and viability with an increase of abnormal sperm morphology. Interestingly, in the combination group (Cd and Cr together), the deleterious effects were more noticeable. Pathologically, both Cd and Cr produced degenerative changes in seminiferous tubules, necrosis of spermatogenic epithelium within the testis. Moreover, the interstitial tissue of epididymis showed marked edema and prostate showed necrosis and serous exudate of lining epithelium. In the interaction group, testis showed complete degenerative changes and necrosis of spermatogenic epithelium, with marked interstitial edema and hyperplastic epithelial lining of epididymal tubules. Conclusion and clinical relevance: The present results support the hypothesis that the testis is one of the most sensitive organs to Cd and/or Cr and that the exposure to any of them or to their combination lead to testicular damage and thereby male infertility.

STRUCTURAL-FUNCTIONAL REORGANIZATION OF SKIN AND ITS DERIVATIVES UNDER EXPERIMENTAL SUBACUTE OF INTOXICATION BY HEAVY METALS

There was executed an experimental study of the effect of salts of heavy metals (nickel, chromium, lead and zinc) entering the body by peroral route, on the morphology of the skin and its derivatives (hair follicles and sebaceous glands). The experiment was performed on C57BL / 6 mice with the use of the induction of hair follicle cycle by depilation. Under the subacute intoxication with salts of nickel, chromium and lead, there were revealed such signs of a dystrophic anagen as ectopia of granules of melanin in the dermal papilla and perifollicular tissue, enlarged channels of the hair. The duration of the anagen stage if compared with the control did not change. Under the intoxication with salts of nickel and lead there was revealed infiltration by mononuclear dermis and hypodermis. Lead acetate gave rise in the capillary congestion of the dermis, followed by diapedesis of erythrocytes and infiltration of the dermis by siderophages. In the course of the immunohistochemical study of the proliferative activity of keratinocytes of the skin integument derivatives with the use of antibodies to Ki-67, there was revealed a significant increase of proliferative activity of keratinocytes in comparison with the control under the use of a solution of zinc sulphate and sodium dichromate and its decrease with the use of lead acetate solution.

RATIO OF PROCESSES OF CELL PROLIFERATION AND APOPTOSIS IN THE SKIN UNDER EXPOSURE TO HEAVY METAL SALTS AND CHELATORS OF ESSENTIAL METALS

In the model experiment on C57BL /6 mice there were established features of the impact of heavy metals and chelators of essential metals on proliferation and apoptosis of epithelial skin cells (keratinocytes). For the execution of a study 40 test animals were divided into seven experimental and 1 control groups, each consisted of five animals. The proliferative and apoptotic activity of keratinocytes was determined by the immunohistochemical method and evaluated by calculating the proliferation index and the index of apoptosis in the cells of the surface epithelium and the epithelial cells of hair follicles in the late anagen stage. Comparative analysis of the proliferation index of the control group and experimental groups showed administration of zinc sulfate, sodium dichromate and zinc chelator (N, N, N`, N`-tetrakis (2-pyridylmethyl) ethylenediamine) to animals to give rise in a statistically significant increase in the proliferative activity of keratinocytes. The decline of proliferation index was detected in animals treated with lead acetate and copper chelator (ammonium tetrathiomolybdate). Introduction of an iron chelator (deferoxamine) had no effect on the proliferative activity of keratinocytes in experimental animals. Induction of apoptosis of epithelial cell was noted under the administration of nickel sulfate, sodium dichromate, lead acetate and zinc chelator (N, N, N`, N`-tetrakis (2-pyridylmethyl) ethylenediamine) to animals. In mice received deferoxamine zinc sulfate and apoptotic activity of keratinocytes has not changed. The use of cluster analysis allowed to classify substances administered to experimental animals, taking into account their simultaneous effect on the studied cellular processes. Lead acetate, iron chelator (deferoxamine) and copper chelator (ammonium tetrathiomolybdate) were shown to reduce the proliferative activity of keratinocytes and have little effect on apoptosis of the epithelial cells of the skin. Zinc sulfate, nickel sulfate, sodium dichromate and zinc chelator (N, N, N`, N`-tetrakis (2-pyridylmethyl) ethylenediamine) activate cell proliferation and induce apoptosis of keratinocytes.