Mineralization Capability Research Articles

Thermal cycling effect of dicalcium phosphate-reinforced composites on auto-mineralized dental resin

The mineralizing capabilities of surface-modified dicalcium phosphate anhydrous (DCPA), reinforced and treated with nanocrystals and capped with silane, in composite resins were analyzed via thermal cycling. We compared two light-curable composites that were mixed at filler-to-resin mass ratios of 30/70 and 50/50. The strengths, elastic moduli, and topographical structures of the samples were determined after thermal cycling between 5 and 55°C in deionized water for 600 and 2400cycles. Silane-capped particles decreased the strength but enhanced the mineralizing capability of the composites. Nanocrystal-treated filler surfaces significantly increased the strength and moduli of the composites after 600thermalcycles. However, these values declined after 2400thermalcycles. The nanocrystal-treated filler surfaces prevented the reduction in strength before and after 2400thermalcycles. Prior to silane capping, the nanocrystal-treated DCPA filler surfaces exhibited good mineralization capability without compromising strength. The potential for barrier generation through mineralization yielded positive effects and prevented micro-leakages.

Sunlight assisted photocatalytic mineralization of nitrophenol isomers over W6+ impregnated ZnO

The synthesis, characterization and sunlight photocatalytic activity of W6+ impregnated ZnO for the degradation of nitrophenol isomers (2-nitrophenol, 3-nitrophenol, and 4-nitrophenol) is reported. Compared to pure ZnO, the impregnated catalysts exhibited a relatively improved spectral response in the visible region. The significant decrease in luminescence intensity for W6+ impregnated catalysts, relative to pure ZnO, established the effective trapping of charge carriers by surface bonded W6+ states. The characterization of the impregnated catalysts by FESEM, XRD and XPS revealed the presence of impregnated W6+ entities at the surface without affecting the morphology of ZnO. The synthesized catalysts exhibited superior activity for the mineralization of three nitrophenol isomers under sunlight exposure. Based on HPLC analysis, ∼99% of 2- and 4-nitrophenol was degraded in a short span of 120min while a degradation of >80% was observed in 3-nitrophenol in the same period. Time scale TOC measurements ratified the mineralization capability of impregnated catalysts. The release of NO2−, NO3− ions in the solution, pH measurements and non-existence of hydroxylated aromatic intermediates revealed that superoxide anion radicals (O2−) are the major contributors in the degradation process. Besides the traces of coupling products, major intermediates identified by GC–MS analysis were either aliphatic dihydroxy alcohols, carboxylic acids or other oxygen containing species depicting that the degradation process proceeds through ring opening mechanism. The W6+ impregnated catalyst also furnished high activity in the visible portion of sunlight. Suitable kinetic models were applied to estimate the rate constants (k) of various processes involved in the degradation process. The stability of the photocatalyst against photocorrosion and the possible decrease in the activity of the catalyst in the successive use was also monitored.

Magnetic Induced Polarization - using new technology for greater detection capability of deep and elusive mineralization

The Magnetic Induced Polarization (MIP) method uses the measurement of magnetic fields to directly detect internal and external current flow from IP-generating targets, rather than the resultant surface currents as with conventional Electric Induced Polarization (EIP). Magnetometric Resistivity (MMR) measures the magnetic field produced by galvanic current flow to detect horizontal variations in resistivity. We focus primarily on the MIP method but since MIP and MMR data are collected simultaneously, we will treat them together where appropriate. MIP/MMR is insensitive to horizontal layering, and is especially suitable for regions with highly conductive cover where EIP and resistivity responses are sharply attenuated. Magnetic fields easily propagate through such conditions; therefore MIP/MMR is minimally impacted by conductive cover. The other major advantage of MIP/MMR, over traditional electrical IP and resistivity, is that it completely eliminates the need for measurement electrodes. Hence, it is effective in difficult ground contact conditions such as dry sandy soils, frozen ground, and rocky scree slopes. For inversion purposes, MIP has an additional benefit that magnetic fields can be measured in all three axes simultaneously, which provides significantly more information about target position and attitude. By using SQUID technology and remote referencing, we are able to improve the data quality and extract useful three component MIP and MMR data. We present a number of field trials using both frequency and time domain methods to analyze the MIP and MMR responses from porphyry copper, and unconformity uranium ore bodies.

Biodegradation of low-ethoxylated nonylphenols in a bioreactor packed with a new ceramic support (Vukopor ® S10)

This work was aimed at studying the possibility of biodegrading 4-nonylphenol and low ethoxylated nonylphenol mixtures, which are particularly recalcitrant to microbial degradation, by employing a biofilm reactor packed with a ceramic support (Vukopor® S10). A selected microbial consortium (Consortium A) was used to colonize the support. 4-Nonylphenol and ethoxylated nonylphenol degradation and mineralization capabilities were studied both in batch and continuous mode. The results showed that Vukopor® S10 was able to be colonized by an active biofilm for the degradation of the target pollutants with the reactor operating both in batch and continuous mode. On the other hand, pollutant adsorption on the support was negligible. FISH showed equal proportion of Alphaproteobacteria and Gammaproteobacteria in the Igepal CO-520 degrading reactor. A shift towards high proportion of Gammaproteobacteria was observed by supplying Igepal CO-210. PCR-density gradient gel electrophoresis (DGGE) analyses also evidenced that the biofilm evolved with time by changing the mixture applied and that Proteobacteria were the most represented phylum in the biofilm. Taken together, the data obtained provide a strong indication that the biofilm reactor packed with Vukopor® S10 and inoculated with Consortium A could potentially be used to develop a technology for the decontamination of 4-nonylphenol and low ethoxylated nonylphenol polluted effluents.

Influence of Sampling Date on Soil Nitrogen Availability Indices

In spite of the great effort that has been devoted to the search for a chemical laboratory index to predict nitrogen (N) mineralization capability of soils, the results have not yet been fully satisfactory. A continued effort is still needed to increase the knowledge of the sources of variation that influence potentially available soil N. The time of sampling has received little attention, taking into account its potential to influence N-mineralization patterns. In this work, soil samples from three different agrosystems, consisting of a double-crop sequence of small grains and maize, an intensively grazed pasture, and a rainfed olive orchard, were collected at different dates. Several chemical extractions were performed, and the results were correlated with N uptake by turnip (Brassica campestris, L.) grown in a pot experiment. Kjeldahl N was the chemical test that best correlated (R 2 = 0.621) with N uptake by turnip. Kjeldahl N showed great versatility relative to the origin of the soil samples. However, it was not very sensitive to the time of sampling. It did not detect changes occurring in the soil over a short period of time. Soil inorganic N showed the second highest coefficient of correlation (R 2 = 0.483) with N uptake by turnip. In contrast to that observed with Kjeldahl N, soil inorganic N appeared as an index that can vary greatly over the short term. The hot saline potassium chloride (KCl) extractions gave generally fair results. The poorest, however, were obtained with the ultraviolet absorption of extracts of 0.01 mol L−1 sodium bicarbonate (NaHCO3) measured at 250- and 260-nm wavelengths.

Fabrication and electrochemical treatment application of a microstructured TiO2-NTs/Sb–SnO2/PbO2 anode in the degradation of C.I. Reactive Blue 194 (RB 194)

A microstructured Sb-doped SnO2/PbO2 electrode was synthesized and investigated for the treatment of C.I. Reactive Blue 194 (RB 194) in aqueous solution. An electrochemical method was employed for the electrodeposition of PbO2 on an ordered microstructured TiO2-NTs template to obtain a large specific surface area and high space utilization. The TiO2-NTs/Sb–SnO2/PbO2 electrode was characterized by XRD, SEM and cyclic voltammetry and the results showed that the predominant phase of the lead dioxide anode is β-PbO2. The decolorization and mineralization of dye RB 194 was investigated by UV–vis measurements and TOC analysis. The removal efficiency was studied as a function of several operation variables, such as current densities, initial dye concentration, initial pH values and chloride ions. It was found that the TiO2-NTs/Sb–SnO2/PbO2 electrode exhibited good decolorization and mineralization capability of RB 194 in neutral conditions at a current density of 150mA/cm2, with an initial dye concentration of 30mg/L. On the basis of the reaction products identified, a possible degradation pathway for the anodic oxidation of non-biodegradable organic dye RB 194 in aqueous solution is proposed.

Mechanical properties and biomineralization of multifunctional nanodiamond-PLLA composites for bone tissue engineering

Multifunctional bone scaffold materials have been produced from a biodegradable polymer, poly(l-lactic acid) (PLLA), and 1–10% wt of octadecylamine-functionalized nanodiamond (ND-ODA) via solution casting followed by compression molding. By comparison to pure PLLA, the addition of 10% wt of ND-ODA resulted in a significant improvement of the mechanical properties of the composite matrix, including a 280% increase in the strain at failure and a 310% increase in fracture energy in tensile tests. The biomimetic process of bonelike apatite growth on the ND-ODA/PLLA scaffolds was studied using microscopic and spectroscopic techniques. The enhanced mechanical properties and the increased mineralization capability with higher ND-ODA concentration suggest that these biodegradable composites may potentially be useful for a variety of biomedical applications, including scaffolds for orthopedic regenerative engineering.

Comparative characterization of stem cells from human exfoliated deciduous teeth and dental pulp stem cells

ObjectiveThis study focused on the characterization of stem cells from human exfoliated deciduous teeth (SHED) in comparison with dental pulp stem cells (DPSCs) to certify SHED as a key element in tissue engineering. MethodsIn the present study, SHED and DPSCs were assayed for their cell surface antigens and proliferation by measuring the cell cycles, growth rates, Ki67-positive efficiencies, and colony-forming units (CFUs). The evaluation of multi-differentiation was performed using alizarin red and oil red O and real-time PCR in vitro. The mineralization capability of the cells was examined in vivo by implanting with ceramic bovine bone (CBB) into subcutaneous of immunocompromised mice for 8weeks. A three-dimensional pellet cultivation system is proposed for SHED and DPSCs to recreate the biological microenvironment that is similar to that of a regenerative milieu. ResultsSHED showed a higher proliferation rate and differentiation capability in comparison with DPSCs in vitro, and the results of the in vivo transplantation suggest that SHED have a higher capability of mineralization than the DPSCs. The mRNA expression levels of inflammatory cytokines, including matrix metalloproteinase-1 (MMP1), tissue inhibitors of metalloproteinase-1 (TIMP1), matrix metalloproteinase-2 (MMP2), tissue inhibitors of metalloproteinase-2 (TIMP2) and interleukin-6 (IL-6) were higher in SHED than that in DPSCs. In addition, the expression levels of Col I and proliferating cell nuclear antigen (PCNA) in SHED sheets were significantly higher than those in DPSCs sheets. ConclusionsThis study systematically demonstrated the differences in the growth and differentiation characteristics between SHED and DPSCs. Consequently, SHED may represent a suitable, accessible and potential alternative source for regenerative medicine and therapeutic applications.

Efficient adsorption and visible-light photocatalytic degradation of tetracycline hydrochloride using mesoporous BiOI microspheres

A novel microsphere-like BiOI hierarchical material was successfully synthesized by a one-step solution method at room temperature using polyvinylpyrrolidone (PVP) as structure directing reagent, its morphology, structure, surface area, photoabsorption were characterized, and the removal of tetracycline hydrochloride (TC) was evaluated under dark adsorption and visible light irradiation. It was shown that the BiOI microspheres formed in the precursor solution with PVP exhibit a mesoporous surface layer, 28.1m2g−1 surface area, 1.91eV band gap energy (Eg value), and twofold removal ability to tetracycline hydrochloride (TC), i.e. adsorptive separation and visible light photocatalytic degradation. The adsorption process of TC on BiOI microspheres can be described by pseudo-second-order kinetics model and both Freundlich and Langmuir equations well described the adsorption isotherm but the former is better. More importantly, the BiOI microspheres exhibit an excellent photocatalytic degradation and mineralization capability to TC under visible light irradiation, which comes from its electronic band structure, high surface area and high surface-to-volume ratio. In addition, the BiOI microspheres are stable during the reaction and can be used repeatedly, showing promising prospect for the treatment of TCs in future industrial application.

Mineralization Potential of Electrospun PDO-Hydroxyapatite-Fibrinogen Blended Scaffolds

The current bone autograft procedure for cleft palate repair presents several disadvantages such as limited availability, additional invasive surgery, and donor site morbidity. The present preliminary study evaluates the mineralization potential of electrospun polydioxanone:nano-hydroxyapatite : fibrinogen (PDO : nHA : Fg) blended scaffolds in different simulated body fluids (SBF). Scaffolds were fabricated by blending PDO : nHA : Fg in the following percent by weight ratios: 100 : 0 : 0, 50 : 25 : 25, 50 : 50 : 0, 50 : 0 : 50, 0 : 0 : 100, and 0 : 50 : 50. Samples were immersed in (conventional (c), revised (r), ionic (i), and modified (m)) SBF for 5 and 14 days to induce mineralization. Scaffolds were characterized before and after mineralization via scanning electron microscopy, Alizarin Red-based assay, and modified burnout test. The addition of Fg resulted in scaffolds with smaller fiber diameters. Fg containing scaffolds also induced sheet-like mineralization while individual fiber mineralization was noticed in its absence. Mineralized electrospun Fg scaffolds without PDO were not mechanically stable after 5 days in SBF, but had superior mineralization capabilities which produced a thick bone-like mineral (BLM) layer throughout the scaffolds. 50 : 50 : 0 scaffolds incubated in either r-SBF for 5 days or c-SBF for 14 days produced scaffolds with high mineral content and individual-mineralized fibers. These mineralized scaffolds were still porous and will be further optimized as an effective bone substitute in future studies.

Surface characterization and biological response of carbon-coated oxygen-diffused titanium having different topographical surfaces

The materials (C-ODTi) with different topographical surfaces that possess interstitial oxygen atoms into the host titanium lattice and an upper nanometric surface layer of anatase-TiO(2) covered by a carbon thin layer were fabricated in this study. The carbon thin layer on the surface of C-ODTi was composed of amorphous carbon and nano-graphite crystals. In vitro tests, using human bone marrow-derived mesenchymal cells (hBMCs), were performed to check cytotoxicity, examining in particular cell morphology, cell proliferation, cell differentiation, and mineralization capability. After 10 days of culture a higher degree of cell viability was observed on the surface of C-ODTi with an abraded surface. We also observed that hBMCs cultured in direct contact with C-ODTi maintained their capability to express alkaline phosphatase activity (ALP) and formed mineralized nodules similar to the control cultures. Our results demonstrate that the carbon layer coating on the surface of C-ODTi possess better biological response than commercially pure titanium (cp Ti), which was evidenced by the higher proliferation rates of osteoblasts, higher osteo-differentiation and a higher mineralization capability.

Microbial Degradation of Soil-Aged 14C-Labeled Pyrene by an Environmental Mycobacterium sp. Strain S65 in Different Soil Environments

Mycobacterium (designated Mycobacterium sp. strain S65 in Genbank), previously isolated and characterized from a jet-fuel contaminated site at the Sept-Iles, Quebec, Canada airport, was found to be competent in mineralizing selected recalcitrant polycyclic aromatic hydrocarbon (PAH) compounds of minimal water solubility and low bioavailability in soils, when grown in yeast extract-tryptone-soluble starch medium. In aerobic liquid microcosms, strain S65 was capable of 61% cumulative mineralization of pyrene over 14 days. Based on 14CO2 evolution, the mineralization capability and capacity of this organism for soil-aged 14C-labeled pyrene was assessed. Gamma-ray sterilized farm soil microcosms were spiked with 1.0 105 dpm 14C-labeled pyrene and allowed to age for up to 360 days. The experimental design consisted of a factorial combination of two types of soil (clay and sandy), two levels of soil organic matter (high and low), and two concentrations of pyrene (1000 and 500 mg L-1) with six replicates per treatment (48 microcosms per inoculation date). One set of 48 aged microcosms was inoculated after each aging period (0, 30, 180, or 360 days) with three replicates per treatment (i.e., 24 microcosms) each receiving 1.0 107 cfu of live Mycobacterium sp. strain S65 (i.e., treatment) and a further three replicates per treatment receiving heat-killed Mycobacterium (i.e., negative control) for an overall total of 192 microcosms. The 14CO2 that evolved over 1, 3, 6, or 9 days and was trapped in a KOH solution was measured by scintillation counter, and cumulative mineralization was calculated as a percent of initial pyrene. As a further basis of comparison, mineralization of un-aged pyrene in culture broth was also measured (i.e., positive control) over the same incubation period. Serial dilution and spread-plate techniques served to assess the possible presence of a viable culturable microorganism population (CFU g-1) in different sterile soils for a total of 4 4 3 = 48 (i.e., soils aging time replicate) microcosm bottles (i.e., sterile control). No microbial colonies were observed on solid media, indicating no culturable competitive microbial strain that might contribute to the mineralization of 14C-labeled pyrene, at any time during the aging process. Un-aged pyrene in soil (day 0) was utilized by Mycobacterium sp. strain S65 without any lag phase, and pyrene mineralization proceeded thereafter. Cumulative mineralization of pyrene added at concentrations of 1000 and 500 mg L-1 reached 19% and 18.5%, respectively, after 24 h and 21% and 20%, respectively, after 96 h in sand-loam, low organic matter soil. At 96 h, cumulative pyrene mineralization in clay-loam, high organic matter soil was only 15.5% and 14.5%, respectively, distinctly less than in the sandy, low organic matter soil. Sampling continued until no further mineralization occurred (i.e., cumulative mineralization reached a plateau). Soil-aged pyrene was metabolized at a moderate rate by Mycobacterium sp. strain S65, whereas un-aged pyrene was mineralized at a greater rate (61% cumulative mineralization) in an aerobic liquid microcosm. For initial additions of 1000 and 500 mg L-1 pyrene, followed by 30 days of aging, Mycobacterium sp. strain S65 showed a maximum cumulative mineralization of 14% and 13.25%, respectively, in sand-loam, low organic matter soil but only 12.5% and 11.5%, respectively, in clay-loam, high organic matter soil. For 180-day and 360-day aged pyrene, cumulative pyrene mineralization was less than 10%, a significant drop from less-aged pyrene-soil microcosms. This suggests that as the aging proceeds in the soil medium, the pyrene becomes less accessible for degradation. Nonetheless, this study supports the idea that Mycobacterium sp. strain S65 has the potential to be useful in bioremediation and biodetoxification of high molecular weight PAH-contaminated sites.

Amino acid derivative-mediated detoxification and functionalization of dual cure dental restorative material for dental pulp cell mineralization

Current dental restorative materials are only used to fill the defect of hard tissues, such as dentin and enamel, because of their cytotoxicity. Therefore, exposed dental pulp tissues in deep cavities must be first covered by a pulp capping material like calcium hydroxide to form a layer of mineralized tissue. However, this tissue mineralization is based on pathological reaction and triggers long-lasting inflammation, often causing clinical problems. This study tested the ability of N-acetyl cysteine (NAC), amino acid derivative, to reduce cytotoxicity and induce mineralized tissue conductivity in resin-modified glass ionomer (RMGI), a widely used dental restorative material having dual cure mechanism. Rat dental pulp cells were cultured on untreated or NAC-supplemented RMGI. NAC supplementation substantially increased the percentage of viable cells from 46.7 to 73.3% after 24-h incubation. Cell attachment, spreading, proliferative activity, and odontoblast-related gene and protein expressions increased significantly on NAC-supplemented RMGI. The mineralization capability of cells, which was nearly suppressed on untreated RMGI, was induced on NAC-supplemented RMGI. These improved behaviors and functions of dental pulp cells on NAC-supplemented RMGI were associated with a considerable reduction in the production of intracellular reactive oxygen species and with the increased level of intracellular glutathione reserves. These results demonstrated that NAC could detoxify and functionalize RMGIs via two different mechanisms involving in situ material detoxification and antioxidant cell protection. We believe that this study provides a new approach for developing dental restorative materials that enables mineralized tissue regeneration.

Designing Poly[(R)-3-hydroxybutyrate]-Based Polyurethane Block Copolymers for Electrospun Nanofiber Scaffolds with Improved Mechanical Properties and Enhanced Mineralization Capability

Efforts to mineralize electrospun hydrophobic polyester scaffold often require prior surface modification such as plasma or alkaline treatment, which may affect the mechanical integrity of the resultant scaffold. Here through rational design we developed a series of polyurethane block copolymers containing poly[(R)-3-hydroxybutyrate] (PHB) as hard segment and poly(ethylene glycol) (PEG) as soft segment that could be easily fabricated into mineralizable electrospun scaffold without the need of additional surface treatment. To ensure that the block copolymers do not swell excessively in water, PEG content in the polymers was kept below 50 wt %. To obtain good dry and hydrated state mechanical properties with limited PEG, low-molecular-weight PHB-diol with M(n) 1230 and 1790 were used in various molar feed ratios. The macromolecular characteristics of the block copolymers were confirmed by (1)H NMR spectroscopy, gel permeation chromatography (GPC), and thermal gravimetric analyses (TGA). With the incorporation of the hydrophilic PEG segments, the surface and bulk hydrophilicity of the block copolymers were significantly improved. Differential scanning calorimetry (DSC) revealed that the block copolymers had low PHB crystallinity and no PEG crystallinity. This was further confirmed by X-ray diffraction analyses (XRD) in both dry and hydrated states. With short PHB segments and soft PEG coupled together, the block copolymers were no longer brittle. Tensile measurements showed that the block copolymers with higher PEG content or shorter PHB segments were more ductile. Furthermore, their ductility was enhanced in hydrated states with one particular example showing increment in strain at break from 1090 to 1962%. The block copolymers were fabricated into an electrospun fibrous scaffold that was easily mineralized by simple incubation in simulated body fluid. The materials have good potential for bone regeneration application and may be extended to other applications by simply coating them with other biologically active substances.

Effect of carbon coating on the biocompatibility of titanium—in vitro cytotoxicity evaluation using human bone marrow cells—

The in vitro biocompatibility of a novel carbon-coated titanium implant (CTi), fabricated by heating a poly(vinyl) alcohol (PVA)-coated titanium disk at 700°C in argon gas, was investigated. The obtained CTi possessed a surface layer of anatase–TiO2 covered by amorphous carbon about 20 nm thick. In order to establish the effectiveness of the CTi as one of the implant materials, in vitro tests using human bone marrow-derived mesenchymal cells (hBMCs) were performed to check cytotoxicity, by examining cell proliferation, cell differentiation and mineralization capability. After 10 days of culture a higher degree of cell viability was observed on the surface of CTi. On the other hand, hBMCs cultured in direct contact with CTi continued to show alkaline phosphatase activity (ALP) and showed mineralization similar to the control cultures. These results indicated that the titanium coated with carbon possessed better biological response than that without carbon, which was demonstrated by the higher proliferation rates of osteoblasts, higher osteo differentiation and higher mineralization ability.

Newly developed Sr-substituted α-TCP bone cements

New bone cements made of Sr-substituted brushite-forming alpha-tricalcium phosphate (alpha-TCP) were prepared and characterized in the present work. The quantitative phase analysis and structural refinement of the starting powders and of hardened cements were performed by X-ray powder diffraction and the Rietveld refinement technique. Isothermal calorimetry along with setting time analysis allowed a precise tracing of the setting process of the pastes. The pastes showed exothermic reactions within the first 10-15 min after mixing and further release of heat after about 1h. An apatitic phase formed upon immersion of the hardened cements in simulated body fluid for 15 and 30 days due to the conversion of brushite into apatite confirming their in vitro mineralization capability. The compressive strength of the wet cement specimens decreased with increasing curing time, being higher in the case of Sr-substituted CPC. The results suggest that the newly developed Sr-substituted brushite-forming alpha-TCP cements show promise for uses in orthopaedic and trauma surgery such as in filling bone defects.

Microbial Community Structure and Biodegradation Activity of Particle-Associated Bacteria in a Coal Tar Contaminated Creek

The Chattanooga Creek Superfund site (Chattanooga, TN) is one of the most polluted waterways in the southeastern U.S. with high polycyclic aromatic hydrocarbon (PAH) concentrations in the sediments. PAHs associate with suspended solids in the water column, and may be redeposited onto the floodplain. These suspended particles represent an interesting but understudied environment for PAH-degrading microbial communities. This study tested the hypotheses that particle-associated bacterial (PAB) communities have genotypic potential (PAH-dioxygenase genes) and activity (naphthalene and pyrene mineralization), and can contribute to natural attenuation of PAHs in Chattanooga Creek. Upstream of the Superfund site, mineralization ranged from 0.2 to 2.0% of added 14C-naphthalene and 0 to 0.1% 14C-pyrene (after 40 h), with first order biodegradation rate constants (k1) ranging from 1.09 to 9.18 x 10(-5) h(-1) and 0 to 1.13 x 10(-6) h(-1), respectively. Mineralization was significantly greater in PAB communities within the contaminated zone, with 11.8 to 31.2% 14C-naphthalene (k1 5.34 to 14.2 x 10(-4) h(-1)) and 1.3 to 6.6% 14C-pyrene mineralized (k1 2.89 to 15.0 x 10(-5) h(-1)). Abundances of nagAc (naphthalene dioxygenase) and nidA (pyrene dioxygenase) genes indicated that PAB communities harbored populations with genetic potential for both low- and high-molecularweight PAH degradation, and quantification of Mycobacterium 16S rDNA genes indicated that PAH-degrading mycobacteria are also prevalent in this environment. Phylogenetic comparisons (T-RFLPs) between PAB and sediments indicated these microbial communities were taxonomically distinct, but shared some functional similarities, namely PAH catabolic genotypes, mineralization capabilities, and community structuring along a contamination gradient

Kinetic study and equilibrium isotherm analysis of Congo Red adsorption by clay materials

This study was to evaluate the adsorption capability of clay minerals of bentonite, kaolin and zeolite to remove Congo Red from aqueous solution. The experiments were carried out in a batch system to optimise operation variables: adsorbent dosage, Congo Red concentration, pH and temperature. Adsorption kinetic and equilibrium isotherm of the clay materials were studied using pseudo-first order and second order kinetic equations, and Freundlich and Langmuir models. The equilibrium data of kaolin was found to best fit to the Langmuir model, while bentonite and zeolite were best explained by the Freundlich model. The adsorption kinetic followed the pseudo-second order equation for the three adsorbents. Intra-particle diffusion studies revealed that the adsorption rates were not solely controlled by the diffusion step. Further thermodynamic investigations showed that the adsorption is an exothermic and spontaneous process. Sodium bentonite demonstrated the best adsorptive capacity followed by kaolin clay, and they can be employed as low-cost alternatives for recalcitrant dye removal from industrial wastewater.

Effect of Pyrolysis Intensity on the Reactivity of Coal Char

The effect of pyrolysis conditions on char reactivity was studied in this paper. The char samples were prepared in a N2 atmosphere from the vitrinite constituents of two bituminous coals (YX and JJ) and their demineralized samples at different temperatures (800−1200 °C) and for different residence times. The effect of pyrolysis intensity on the carbon microstructure in the resulting char was characterized by the X-ray diffraction (XRD) technique. The reactivity of the char samples prepared under different pyrolysis conditions was measured by isothermal thermogravimetric analysis methods in an air atmosphere. The results show that the reactivity of the coal char decreases with increasing pyrolysis intensity and, when the pyrolysis temperature is high enough, the reactivity of the chars prepared from two coals and their demineralized samples tend to be the same. With increasing pyrolysis intensity, the growth of the carbon microstructure, accompanied by diminishing catalytic capability of minerals, results in the decrease in char reactivity.

Preparation and in vitro characterization of novel bioactive glass ceramic nanoparticles

SiO(2)-CaO-P(2)O(5) ternary bioactive glass ceramic (BGC) nanoparticles with different compositions were prepared via a three-step sol-gel method. Polyethylene glycol was selected to be used as the surfactant to improve the dispersion of the nanoparticles. The morphology and composition of these BGC nanoparticles were observed by ESEM and EDX. All the BGC particles obtained in this method were about 20 nm in diameter. XRD analysis demonstrated that the different compositions can result in very different crystallinities for the BGC nanoparticles. Bioactivity tests in simulated body fluid solution (SBF), and degradability in phosphate buffer solution (PBS), were performed in vitro. SEM, EDX, and XRD were employed to monitor the surface variation of neat poly(L-lactic acid), PLLA, foam and PLLA/BGC porous scaffolds during incubation. The BGC nanoparticles with lower phosphorous and relative higher silicon content exhibited enhanced mineralization capability in SBF and a higher solubility in PBS medium. Such novel nanoparticles may have potential to be used in different biomedical applications, including tissue engineering or the orthopedic field.