The Hydrothermal Synthesis Duration Influence on Calcium Phosphate and Hydroxyapatite Phase Composition

This paper reports the hydrothermal synthesis process duration influence on phase composition, crystallinity degree, morphology and dispersity of the hydroxyapatite powder. The calcium phosphate and hydroxyapatite were synthesized in precursor system Ca(NO[3])[2](NH[4])[2]HPO[4]-NH[4]OH. The obtained powders were characterized with X-Ray diffraction, Fourier Transform spectroscopy (FTIR) and Raman spectroscopy. The results demonstrate: the increasing of the synthesis time duration has no influence on the phase composition. However, the synthesis duration time growth from 12 to 48 hours make possible increase the crystallinity degree from 0.68 to 0.98

The Hydrothermal Synthesis Duration Influence on Calcium Phosphate and Hydroxyapatite Phase Composition

This paper reports the hydrothermal synthesis process duration influence on phase composition, crystallinity degree, morphology and dispersity of the hydroxyapatite powder. The calcium phosphate and hydroxyapatite were synthesized in precursor system Ca(NO[3])[2](NH[4])[2]HPO[4]-NH[4]OH. The obtained powders were characterized with X-Ray diffraction, Fourier Transform spectroscopy (FTIR) and Raman spectroscopy. The results demonstrate: the increasing of the synthesis time duration has no influence on the phase composition. However, the synthesis duration time growth from 12 to 48 hours make possible increase the crystallinity degree from 0.68 to 0.98

The pH Level Influence on Hydroxyapatite Phase Composition Synthesized with Hydrothermal Method

This paper reports the pH level influence on hydroxyapatite phase composition synthesized with hydrothermal method in Ca(OH)2-H3PO4, Ca(NO3)2-(NH4)2HPO4-NH[4]OH, Ca(OH)[2]-NH[4]H[2]PO[4].The obtained samples were studied with X-Ray diffraction, Fourier Transform Infrared (FTIR) and Raman spectroscopy. The one phase Ca[5]H[2]O[13]P[3] high crystallinity hydroxyapatite was synthesized with hydrothermal method at pH equal to 11. The crystallinity degree was calculated from the X-Ray diffraction pattern and became 0.96. The increasing pH level from 7 to 11 provides obtaining one phase hydroxyapatite at pH level 11 instead the two phase Ca[9.04](PO[4])6(OH)[1.68], CaHPO[4] at pH level 9 and CaPO[3](OH), Ca(OH)[2] at pH level 7

Physicochemical aspects of recycling tree leaf litter in the south of Western Siberia by the Eisenia fetida (Savigny) vermiculture

The utility of the compost worm Eisenia fetida (Savigny) for recycling mixed leaf litter of the tree species characteristic of the forests in the south of Western Siberia and used in the landscaping in the city of Tomsk has been demonstrated. The tree species that are the major contributors to the leaf litter in the examined area include the genera Populus, Salix, and Betula. Two-fraction substrates for leaf litter vermicomposting and conventional composting (decomposition with and without earthworms) were prepared of the harvested and dried leaf litter. The feeding fraction consisted of leaf litter moistened with distilled water and the absorbing fraction, of alluvial river sand. The physicochemical properties of the studied leaf litter were weakly acidic pH of aqueous extracts, a very low content of nitrate nitrogen, and a relatively low K + concentration. The prevalent cation in the assayed leaf litter was Ca 2+ . The leaf litter was partially decomposed on the surface of sand substrates during 35-day incubation under humid conditions; accumulation of inorganic ions in the sand was one of the signs indicating this decomposition. Ca 2+ was also prevalent among these ions

The effects of liquid-phase oxidation of multiwall carbon nanotubes on their surface characteristics

The development of new sorbents based on nanostructured carbon materials recently became a perspective field of research. Main topic of current study is to investigate the effect of different regimes of multiwall carbon nanotubes (MWCNT) surface modification process on their structural characteristics. MWCNT samples were treated with nitric acid at high temperature. Structural properties were studied using low temperature nitrogen adsorption and acid-base back titration methods. The study showed that diluted nitric acid does not affect MWCNT structure. Concentrated nitric acid treatment leads to formation of 2.8 carboxylic groups per 1 nm{2} of the sample surface

The pH Level Influence on Hydroxyapatite Phase Composition Synthesized with Hydrothermal Method

This paper reports the pH level influence on hydroxyapatite phase composition synthesized with hydrothermal method in Ca(OH)2-H3PO4, Ca(NO3)2-(NH4)2HPO4-NH[4]OH, Ca(OH)[2]-NH[4]H[2]PO[4].The obtained samples were studied with X-Ray diffraction, Fourier Transform Infrared (FTIR) and Raman spectroscopy. The one phase Ca[5]H[2]O[13]P[3] high crystallinity hydroxyapatite was synthesized with hydrothermal method at pH equal to 11. The crystallinity degree was calculated from the X-Ray diffraction pattern and became 0.96. The increasing pH level from 7 to 11 provides obtaining one phase hydroxyapatite at pH level 11 instead the two phase Ca[9.04](PO[4])6(OH)[1.68], CaHPO[4] at pH level 9 and CaPO[3](OH), Ca(OH)[2] at pH level 7

Amino acids adsorption in differently aged and concentrated aqueous suspensions of ZnO and TiO[2] nanoparticles

Amino acids may be effectively used for preventing aggregation of engineered nanoparticles (NPs) in aqueous suspensions. This paper is primarily focused on the influence of exposure duration and particles content on adsorption coefficient (Ads) for ZnO and TiO[2] nanoparticles with an average size of 40-60 nm exposed to 2M aqueous solutions of glycine and L-glutamic acid. The value of Ads was estimated from surfactant concentration related to the intensity of infrared peak spectroscopy at 1300-1400 cm{−1}. It has been shown that in more concentrated suspensions (0.08-0.12 g/mL) Ads has ±5% fluctuation in measurement error' interval, whereas in less concentrated systems (0.02-0.04 g/mL) 3...20 h exposure of NPs may result in slight desorption of surfactant as shown for ZnO NPs or total desorption of surfactant as shown for TiO[2] NPs in glycine solutions. Six times decrease of 0.02 g/mL NPs concentration leads to Ads augmentation by 3-4 and 1.5{-6} times, respectively, on ZnO and TiO[2] nanoparticles. From a methodological view point, it has been concluded that in order to provide effective comparative study of NPs adsorption properties it is not reasonable to concentrate the NPs suspension more than 0.04 g/mL and it is better to expose them during 3 h in order to avoid surfactant desorption

Microwave treatment and pH influence on hydroxyapatite morphology and structure

This paper reports the influence of microwave treatment duration and pH conditions of initial precursors on the morphological and crystalline dispersity of the hydroxyapatite (HAp) synthesized by hydrothermal method.The obtained HAp samples were studied by scanning electron microscopy, X-Ray diffraction method and low nitrogen adsorption method. We have obtained nanostructured crystalline hydroxyapatite with 95% crystallinity, porous structure and average particles size in interval 17...46 nm consolidated in aggregates with size distribution of 0.5...25 [mu]m. The pH growth from 8 to 13 results in double increase of HAp specific area(from 69 up to 133 m{2}/g), meanwhile microwave irradiation brings to particles aggregation: HAp treated during 0... 10...30 min have specific surface are 112...67...41 m{2}/g, respectively. As a result at pH=13 and without microwave irradiation treatment we synthesized HAp with maximum surface compared to the surface of natural HAp that makes obtained HApto be promising material in biotechnological applications

Wastewater Treatment from Lead and Strontium by Potassium Polytitanates: Kinetic Analysis and Adsorption Mechanism

The reduction of heavy and radioactive metal pollution of industrial wastewater remains a vital challenge. Due to layered structure and developed surface, potassium polytitanate had potential in becoming an effective sorbent for metal extraction from wastewater in the presented paper. On the basis of the different sorption models, this paper studied the mechanism of Pb2+ and Sr2+ cation extraction from aqueous solution by non-crystalline potassium polytitanate produced by molten salt synthesis. The ion exchange during metal extraction from model solutions was proven by kinetic analysis of ion concentration change, electronic microscopy, and X-ray fluorescence analysis of sorbent before and after sorption, as well as by theoretical modeling of potassium, lead, and strontium polytitanates. The sorption was limited by the inner diffusion in the potassium polytitanate (PPT) interlayer space, as was shown using the Boyd diffusion model. The sorption processes can be described by Ho and McKay’s pseudo-second-order model compared to the Lagergren pseudo-first-order model according to kinetic analysis. It was found that the ultimate sorption capacity of synthesized sorbent reached about 714.3 and 344.8 (ions mg/sorbent grams) for Pb2+ and Sr2+ ions, respectively, which was up to four times higher than sorption capacity of the well-known analogues. Therefore, the presented study showed that potassium polytitanate can be considered as a promising product for industry-scaled wastewater purification in practice