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The green synthesis of nanoparticles using plant extracts plays an important role in the field of nanotechnology. The potential of biomolecules present in plant extracts in reducing metal ions to nanoparticles in a single step of green synthesis process is very important. In this study we report on synthesis of Chromium oxide nanoparticles (Cr2O3) by reduction of potassium chromate solution with Manihot esculenta leaf extract. The presence of water soluble carbohydrates which have an aldehyde group may lead the formation of Cr2O3 nanoparticles. The fabricated Chromium oxide nanoparticles were confirmed by UV–Vis spectroscopy, X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM).XRD and UV–Visible absorption studies. The images showed that the size of NPs of Cr2O3 varied with average crystalline size 85–100 nm of nanosized Cr2O3.

Single and co-doped chromium and sulfur TiO2 nanotubes appropriate for photoelectrochemical water splitting application have been prepared and characterized via anodization of titanium foil. The synthesis parameters were optimized by optimization of S and Cr precursor ratio in the anodization electrolyte composition. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy-dispersive spectrometer (EDS) were used to characterize the morphology, crystallinity, and elemental composition of the nanotube samples synthesized. Chromium and sulfur doping affect the morphological and photoelectrochemical properties of samples prepared, as the results indicate. S-doped, Cr-doped, and various Cr-S-co-doped TiO2 nanotubes have enhanced photoelectrochemical activity in comparison with the reference undoped TiO2 nanotube under irradiation by xenon light. Unlike single doped S-TiO2 and Cr-TiO2, Cr-S-co-doped samples show remarkably enhanced photoelectrochemical behavior under identical conditions. The best PEC water splitting performance was shown by sample Cr25S75 prepared by anodizing titanium in in an ethylene glycol solution, which contained 9 mM potassium disulfite and 3 mM potassium chromate, as the sulfur and chromium sources, respectively. This sample showed a photocurrent density of 202 µA/cm2, which is 4.5 times that of the corresponding value for pure and undoped TiO2 nanotube. In addition, the photoelectrochemical behavior of sample Cr25S75 has been investigated using various aliphatic alcohols as sacrificial agent. The trend in the photocurrent density of Cr25S75 was as follows: methanol > ethanol > 1-propanol > 1-butanol > 1-pentanol. The photocurrent density decreased as the number of carbon atoms of the alcohols increased.

Submitted by Jeferson Carlos da Veiga Rodrigues (jveigar@unisinos.br) on 2022-12-07T19:13:50Z No. of bitstreams: 1 Gabriela Savicki_PROTEGIDO.pdf: 3062625 bytes, checksum: 768d687c3ff1d7097a4ffd724304bfd1 (MD5) Made available in DSpace on 2022-12-07T19:13:50Z (GMT). No. of bitstreams: 1 Gabriela Savicki_PROTEGIDO.pdf: 3062625 bytes, checksum: 768d687c3ff1d7097a4ffd724304bfd1 (MD5) Previous issue date: 2022-09-30 Nenhuma É crescente a busca por tecnologias de tratamento mais sustentáveis de resíduos industriais para evitar a disposição final destes em aterros, em especial os resíduos perigosos. O cromo (Cr) é um metal que pode trazer toxicidade a resíduos, dependendo da sua valência e concentração, tornando-os perigosos, sendo que diversos resíduos industriais possuem esse metal em sua composição. Uma tecnologia de tratamento utilizada para resíduos contendo metais é a estabilização por solidificação (E/S) destes resíduos em matriz de cimento Portland, sendo necessário avaliar a viabilidade técnica e ambiental da aplicação. Existem diversos estudos sobre a viabilidade da E/S para resíduos contendo Cr, porém poucos analisaram especificamente o processo de hidratação do cimento Portland. Essa pesquisa teve como objetivo avaliar a influência de compostos de Cr(III) insolúvel em água (Cr2O3) e de Cr(VI) solúvel em água (K2CrO4) na formação dos produtos de hidratação nas idades iniciais de pastas de cimento Portland, através da adição de 0%, 10%, 20% ou 30% desses compostos, separadamente. Foram executadas as análises de pH, difração de raios-X (DRX), calorimetria isotérmica, termogravimetria (TG/DTG) e resistência à compressão nas amostras produzidas. A partir dos resultados foi possível verificar que a incorporação do composto de Cr(III) insolúvel em água (Cr2O3) retardou o processo de hidratação da pasta de cimento Portland, porém não impediu a formação dos compostos de hidratação do material e apresentou resistência à compressão mais elevada do que a amostra de referência. Além disso, foi possível evidenciar a formação do composto chamado de “bentorita”, cuja fórmula química é Ca6Cr2(SO4)3(OH)12.26H2O. Já a incorporação de Cr(VI) solúvel em água (K2CrO4) resultou em um atraso mais significativo no processo de hidratação do material, não tendo sido possível verificar a formação dos produtos hidratados conforme a amostra de referência, além da resistência à compressão ter sido menor. Nessas amostras, também foi possível evidenciar a formação de um produto hidratado contendo Cr, chamado de cromato de cálcio hidratado (CaCrO4.H2O). Sendo assim, o tratamento de resíduos contendo Cr(III) através da E/S pode ser uma opção viável, mediante análises de viabilidade ambiental, por exemplo, enquanto a E/S para resíduos contendo Cr(VI) não é recomendada. The search for more sustainable treatment technologies for industrial waste to avoid their final disposal in landfills is growing, especially for hazardous waste. Chromium (Cr) is a metal that can bring the characteristic of toxicity to residues, depending on its valence and concentration, making it dangerous, and several industrial residues have this metal in their composition. The stabilization by solidification (S/S) is a treatment technology that uses residues containing metals in Portland cement matrix and it is necessary to evaluate the technical and environmental feasibility of the application. There are several studies on the feasibility of S/S for Cr waste, but few have specifically analyzed the Portland cement hydration process. This research aimed to evaluate the influence of water-insoluble Cr(III) compound (Cr2O3) and water-soluble Cr(VI) compound (K2CrO4) in the hydration products formation of Portland cement pastes in the initial ages, through the adding of 0%, 10%, 20% or 30% of these compounds separately. Analyzes of pH, X-ray diffraction (XRD), isothermal calorimetry, thermogravimetry (TG/DTG) and compressive strength were performed on the prepared samples. From the results, it was possible to verify that the incorporation of the water-insoluble Cr(III) compound (Cr2O3) delayed the hydration process of the Portland cement paste, but did not prevent the hydration compounds formation and got higher compressive strength than the reference sample. In addition, it was possible to evidence the formation of the compound called “bentorite”, whose chemical formula is Ca6Cr2(SO4)3(OH)12.26H2O. The incorporation of water-soluble Cr(VI) (K2CrO4) resulted in a more significant delay in the hydration process of the material and it was not possible to verify the formation of hydrated products according to the reference sample, besides the compressive strength was smaller. In these samples, it was also possible to evidence the formation of a hydrated product containing Cr, named hydrated calcium chromate (CaCrO4.H2O). The treatment of Cr(III) containing waste trough S/S could be a viable option with the application of other analysis such as environmental viability, while the S/S for Cr(VI) containing waste is not recommended.

We study the currentless diffusion saturation, metal-thermal reduction, and the electrochemical behaviors of chromium- and silicon-containing melts and establish the conditions of synthesis of chromium silicides in the form of superfine powders and coatings. It is shown that the role of limiting stage of the process of diffusion saturation of chromium, molybdenum, and tungsten with silicon in chloride-fluoride melts is played by the diffusion of silicon atoms in the solid phase. In the course of currentless transfer of silicon to metals of group VIB, silicide coatings are formed on their surfaces. The combined reduction of chromium (III) chloride and sodium fluorine-silicate by metallic sodium or magnesium makes it possible to obtain silicide powders. We formulate the conditions required for getting powders of chromium silicides by electrolysis of chloride-fluoride melts containing fluorine-silicate and potassium chromate. The oxidation resistance of the obtained silicide powders is explained by the formation of silicon-oxide layers on their surfaces.

C. citratus, known as zacate de limón (lemongrass), is commonly used in Costa Rica for the treatment of "kidney diseases." Therefore, the activity as renal protector of an aqueous extract of this plant was evaluated after oral administration, in a model of acute kidney injury (AKI) in female Wistar rats. For this, an aqueous extract was characterized by thin layer chromatography and qualitative phytochemical tests. An AKI model induced by potassium chromate in female Wistar rats was carried out. The serum concentration of creatinine, sodium, potassium and glucose were determined, as well as the concentrations of creatinine, sodium, potassium, glucose and proteins in urine, together with the urinary flow determination. A histopathological analysis of the subjects' kidneys was performed, and the presence of kidney damage was identified. The characterization of the extract by thin layer chromatography, and ferric chloride, Shinoda and Wilson tests gave negative results for phenols, tannins and flavonoids. No positive changes were observed in renal function markers in urine. No histopathological evidence of nephroprotective activity of the aqueous extract of C. citratus was found. It is concluded that the aqueous extract of C. citratus obtained by infusion does not possess nephroprotective activity at a dose of 150 mg/kg evaluated by the AKI in female Wistar rats. UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias de la Salud::Instituto de Investigaciones Farmacéuticas (INIFAR)

The genotoxic potentials of two water-based oilfield chemicals on edible aroids were investigated. Five accessions of Colocasia eculenta and three accessions of Xanthosoma maffafa were exposed to graded concentrations of sodium azide and potassium chromate; while the accessions without any chemical additive were used as controls. Results revealed that the peak periods of cell division were recorded between 12:00 noon to 4:00 pm in both the treated and control accessions. Metaphase cells increased after prophase cells and continued mostly between 10.00 am and 4.00 pm. Variations observed with the treatments included: shifts of metaphase peaks, high percentages of prophase cells, high intensity of cytoplasmic staining and induction of micronuclei among others. Sodium azide was observed to be a stronger genotoxic substance than potassium chromate. Accession NCe 001 had the highest survival rate while NCe 002 recorded the least rate of survival. Statistical evidence revealed that the difference in various mitotic stages and time of harvest between different accessions and treatments was significant at both 5% and 1%. The study provides useful information that would be used to promote cytogenetic researches as well as the exploitation and improvement of this neglected and underexploited economic plant.

The applicability of radioactive species in high-temperature research as tracers was studied with KBr and an Nb-stabilised austenitic stainless steel. KBr-induced high-temperature corrosion was addressed by using radioactive [82Br]KBr and measuring the radioactivity of the sample surface with a high-resolution phosphor imaging device. Neutron activation by cyclotron proved to be a very cost-effective way to produce radioactive [82Br]KBr with a high radionuclidic purity and a negligible level of unwanted side products. KBr reacts rapidly with steel, forming potassium chromate and metal bromides, both of which are reducing the protective properties of the surface oxide through chromium depletion and increasing porosity.

In this work, the authors have presented a study on the variation in optical parameters that occur on doping Poly-methyl-metha crylate (PMMA) thin films with Potassium chromate (K2CrO4) by different weight percentages (1%,2%, 5% and 10%). These pure PMMA and its composite films are of thickness ∼100m and have been synthesized using the solution cast technique. The absorbance (A) and transmittance (T %) spectra of these films were recorded in the wavelength range (300-1100) nm using EI 2375 UV-VIS double beam spectrophotometer. From the obtained data, the optical parameters viz. absorption coefficient, extinction coefficient), finesse coefficient (F), refractive index (, real and imaginary parts of dielectric constant , optical conductivity and optical energy gap for indirect transition were evaluated and are found to show variation with increase of K2CrO4 concentration in the mentioned wavelength range.

Interactions of the surfaces of potassium chromate crystal nanoparticles with carbon nanotubes and graphene are computationally studied by the electronic structure calculations within the molecular cluster approach. Three types of carbon nanostructures were considered in calculations: single-walled (~ 0.7 nm in diameter) and multiwalled carbon nanotubes (~ 5 nm in diameter), fragments of graphene sheet. Potassium chromate crystal fragments of linear sizes ranging from ~0.5 to ~2 nm (chromate anion and potassium chromate clusters consisting of 1 – 32 formula units of the crystal) were modeled in calculations. The results of the calculations revealed the mechanism of bonding between oxide crystal fragments and carbon nanostructures. It was found that the graphene sheet most effectively interacts with such a surface of the potassium chromate crystal that contains the most possible number of potassium cations. It was shown that the interaction of single-layer graphene sheets with fragments of potassium chromate having linear dimensions of several nanometers leads to significant distortion (twisting) of the graphene sheet. Conclusions regarding the possibility of efficient adsorption of crystal nanoparticles by the surfaces of real carbon nanostructures were made.

A new method has been developed for determination of 210Pb and a simultaneous determination of 210Po and 210Pb was performed in solid samples. 210Po and 210Pb were sequentially leached at 250 °C with HNO3+HF, HClO4 and HCl. Twenty percent of the leaching solution was used for 210Po determination by α-spectrometry after 210Po spontaneous deposition on a silver disc from a weak HCl solution that containing hydroxylamine hydrochloride, sodium citrate and 209Po tracer. The remains of the leaching solution were used for determination of 210Pb, conducted by precipitation as PbCrO4 at about pH

Water fleas constitute major zooplankton population of fresh water aquatic ecosystem. Their population density is an indicative of well-being of aquatic bodies. Simocephalus vetulus (Crustacea - Cladocera) is a tailless water flea and is well suited lab model for environmental monitoring. Copper a Gray listed heavy metals despite being an essential micronutrient, becomes highly toxic when present in excess quantity in aquatic ecosystem thereby causing deleterious effects on aquatic flora as well as fauna. The water-flea exposed to acute 0.37 mg/l (96hr LC50), sub-acute 0.0925 mg/l (25% of 96hr LC50) value and chronic 0.037 mg/l (10% of 96hr LC50) value of copper sulphate and acute 0.16 mg/l (96 hr LC50), sub-acute 0.04 mg/l (25% of 96 hr LC50) value and chronic 0.016 mg/l (10% of 96 hr LC50) value of potassium chromate showed behavioural alterations like initial hyperactivity, fast appendage movements and in phototaxis, geotaxis and avoidance indices. At later stage erratic swimming and spinning, reduced activity, loss of balance, reduced feeding and darkening of cuticular coloration, reduced phototactic, geotaxis and avoidance indices were the major effects on its behaviour. The behavioural alterations of S. vetulus showed the most susceptible and foremost indication of potential toxic effects. Various behavioural parameters, used in present study may serve as better biomarkers about metal toxicity and monitoring of drinking water quality

Phyto-accumulation kinetics of chromium (Cr) was investigated using hydroponic experiments with excised roots or intact rice seedlings exposed to potassium chromate Cr(VI) or chromium nitrate Cr(III). Results showed that the accumulation kinetics was all described by Michaelis-Menten function, whereas very distinct half-saturation constant (KM) and maximal accumulation capacity (vmax) was obtained for the respective Cr species. The comparison of the results from intact rice seedlings to detached roots indicated that transpiration has a stronger influence on Cr(III) transport by rice seedlings. Rice seedlings exposed to Cr(III) showed significantly higher potential for Cr accumulation in plant tissues than these exposed to Cr(VI). Although roots were the major site for Cr accumulation in both Cr treatments, restriction of root-to-shoot Cr translocation was more evident in Cr(III) treatments than Cr(VI) treatments. A remarkable difference in subcellular distribution of Cr in plant materials was observed between the two Cr treatments. Cell walls of rice seedlings exposed to Cr(III) accumulated more Cr in both roots and shoots than organelles and cytosol, whereas cytosol fraction was the largest in roots from the Cr(VI) treatments. Our results suggest that significant differences in uptake, accumulation and translocation pathways for Cr(VI) and Cr(III) exist in rice seedlings.

The effect of potassium chromate (K2CrO4) compound on the inhibitive performance of type A513 mild steel was studied using linear and open circuit polarization technique with µAutolab PGstat101. The structural degradation tendency was observed with high resolution optical microscope. Data obtained from Tafel plot showed that the organic compound performed effectively in acid/chloride solution at all concentration of (K2CrO4) with average inhibitor efficiency above 60%. The outcome of the OCP showed a significant correlation with the LPR trend. The massive influence of the inhibitive compound on steel was seen as a chemisorption mechanism in which the corrosive anions and particulate were supressed significantly. The adsorption of the compound was determined and was found to obey the Langmuir isotherm model. The structural properties generally were affected with high aggressiveness of the acid/chloride ion mix with uniform corrosion propagation observed along the entire interface.

Concrete sludge is an industrial waste slurry containing hydrated cement, aggregates and water. The main components of concrete sludge are CaO, SiO2, Al2O3 and small amounts of metal oxides such as Fe2O3 and MgO. In this study, the calcium component of concrete sludge was used as a raw material for the synthesis of Ca-Al type layered double hydroxide (LDH). The chromate removal ability of the LDH was examined using a potassium chromate solution containing 180 mg/L chromate. The LDH showed a high chromate removal ability with a concentration decrease of up to 0.4 mg/L. The chromate is removed in the form of CrO42 − by anion exchange with NO3− in the Ca-Al NO3 LDH.

The interaction between two chromates [sodium chromate (Na2CrO4) and potassium chromate K2CrO4)] and bovine serum albumin (BSA) in physiological buffer (pH 7.4) was investigated by the fluorescence quenching technique. The results of fluorescence titration revealed that two chromates could strongly quench the intrinsic fluorescence of BSA through a static quenching procedure. The apparent binding constants K and number of binding sites n of chromate with BSA were obtained by the fluorescence quenching method. The thermodynamic parameters enthalpy change (ΔH), entropy change (ΔS) were negative, indicating that the interaction of two chromates with BSA was driven mainly by van der Waals forces and hydrogen bonds. The process of binding was a spontaneous process in which Gibbs free energy change was negative. The distance r between donor (BSA) and acceptor (chromate) was calculated based on Forster's non-radiative energy transfer theory. The results of UV-Vis absorption, synchronous fluorescence, three-dimensional fluorescence and circular dichroism (CD) spectra showed that two chromates induced conformational changes of BSA.

This work is directed for removal of the nondesired species (228Ra, 226Ra, 223Ra, 210Pb, Th(IV) and Fe(III)) in the rare earth chloride (RECl3) liquor before separation of Ln(III). The different factors affecting elimination of radium-isotopes, lead (210Pb), Th(IV) and Fe(III) from the RECl3 liquor, have been investigated and optimized. The results indicated that the activity concentration of radionuclides in RECl3 liquor was above the safe limits required during the separation process of Ln(III). Adjustment of pH 3±0.1 leads to eliminate 14±1% of radionuclides and Th(IV), and 40±3% of Fe(III), while 12±1% of Ln(III) was lost. The developed method shows that more than 95% of the nondesired species was selectively removed when the liquor was eliminated by potassium sulfate or sulfuric acid solutions in presence of Ba/Pb-carrier (1: 1). About 20-83% of Ln(III) was lost when the non-desired species removed by sodium or ammonium sulfate or potassium chromate solutions. Fe(III) interfered with Ln(III) when radionuclides and Th(IV) were eliminated by 2.6M H2SO4 in presence of Ba/Pb-carrier. Finally, use of 0.23M K2SO4 or 2.6M H2SO4 was efficient to reduce level of 228Ra, 226Ra, 223Ra and 210Pb to the safe limits in viewpoint of radiation protection. In addition, the interfered Th(IV) and Fe(III) were also eliminated efficiently from RECl3 liquor before the chemical processing of Ln(III).

A study was made of the effect of synthesis conditions on the properties of a magnetoactive compound obtained by the interaction of iron(II) sulfate with potassium chromate. It was found that, in the formation of the magnetoactive compound, chromium is almost completely coprecipitates with the solid phase. To produce the magnetoactive compound with high relative magnetic susceptibility, it is necessary to precipitate it from the initial solution in no less than 10 min after its preparation at a K2CrO4: FeSO4 molar ratio of 0.16–0.18.