Sorption of boron by invasive marine seaweed: Caulerpa racemosa var. cylindracea

The sorption of boron from aqueous solution onto Caulerpa racemosa var. cylindracea (CRC), collected from Seferihisar/Izmir region in Turkey, was investigated as a function of pH, temperature, initial boron concentration, adsorbent dosage, contact time and ionic strength. Optimum conditions for the sorption of boron were obtained at pH 7.5, 318 K, 8 mg L⁻¹ initial boron concentration, 0.2 g of CRC, 2.5 h contact time and greater ionic strength (10⁻¹ M NaCl). As the temperature was increased the boron removal took place with higher percentages. In experiments conducted at optimum conditions, maximum boron sorption was determined to be about 63%. The experimental data were analyzed by Freundlich, Langmuir and Dubinin–Radusckevich (DR) equations. Freundlich and DR models provide best conformity with the experimental data. In order to describe kinetics of boron sorption onto CRC, first-order Lagergren equation, pseudo-second-order kinetic model and intraparticle diffusion model were used. It was seen that the first order Lagergren equation was better described than the pseudo-second-order kinetic model. Thermodynamic parameters of sorption process were also calculated. It was obtained that sorption process was not spontaneous. The characterization of CRC was carried out by Fourier transform infrared spectroscopy (FTIR) analysis.     

Improvement of the growth of Arthrospira (Spirulina) platensis from Toliara (Madagascar): Effect of agitation, salinity and CO2 addition

Arthrospira (Spirulina) platensis Toliara isolated from alkaline and salt lakes in the south-western area of Madagascar is a potential source of proteins that could efficiently fight against food deficiency in developing countries like Madagascar. Up to now, productivity in this country has been low, so a better understanding of the growth conditions of this species is needed to improve its production. Growth experiments were undertaken in bubble columns at laboratory scale. The influence of agitation of the culture, medium salinity (ranging from 13 to 35 g L⁻¹) and CO₂ addition (ranging from 0 to 2%, v/v) on growth and protein content was examined. Because Arthrospira cells are fragile, a bubble column without additional mixing gave the best growth. Arthrospira (Spirulina) platensis showed higher specific growth rate (μ_max) and protein content for lower salinity. Addition of 1% of CO₂ improved the productivity by near 60%. The feasability of semi-continuous culture was demonstrated and optimal culture conditions led to a mean productivity of 0.22 ± 0.03 g L⁻¹ d⁻¹, a mean specific growth rate of 0.015 ± 0.002 h⁻¹ and a protein content of 53 ± 2% of total dry weight.     

In vitro and in vivo release of cefuroxime axetil from bioactive glass as an implantable delivery system in experimental osteomyelitis

The aim of this study was to evaluate the characterisation, in vitro and in vivo biocompatibility and antimicrobial activity of bioactive glass (BG) impregnated with an antibiotic. The BG was prepared by normal glass melting procedures as a controlled release device to treat experimental osteomyelitis. The study design was for prospective in vivo experimental study. Two sets of porous bioactive glass ceramic blocks (9 mm × 4 mm × 4 mm and 20 mm × 9 mm × 9 mm) were fabricated using bioactive glass powder and subsequently antibiotic cefuroxime axetil (CFA) (55 and 125 mg on an average) was impregnated in these two sets of blocks, respectively. Osteomyelitis was produced in the right tibia of the rabbits according to the model of Norden. After thorough in vitro characterization of the porous blocks [including X-ray diffraction (XRD), Fourier-transformed infra-red spectroscopy (FTIR), thorough chemical analysis by inductively coupled plasma-atomic emission spectra (ICP-AES) and field-emission scanning electron microscopy (FESEM)] and in vitro elution of the said drug, in vivo test was carried out with rabbit species split into two groups: (a) animals treated with CFA impregnated bioactive glass and (b) parenteral [intra muscular (IM)] administration of CFA. Histological, radiological and drug concentration in bone and serum (measured by HPLC) in both groups were carried out. HPLC technique was used for determination of concentration both in vitro and in vivo. Fabricated porous struts showed amorphous microstructure without formation of any crystallite. The elution of said drug was stopped after 6 days in vitro. Histological studies at 3 and 6 weeks revealed formation of well-developed lamellar bone and havarsian canal. Radiological evaluation pointed out disappearance of sequestrum and existence of newly formed bony specules. Concentration of cefuroxime axetil in bone and serum showed highest value on day 21 which reduced marginally by day 42 and these values were higher than minimum inhibitory concentration (MIC) against Staphylococcus aureus (known pathogen for chronic osteomyelitis). It could be concluded that the biodegradable antibiotic carrier system developed in this study proved to be an effective therapeutic approach toward an experimental model of osteomyelitis. Based particularly on the in vivo results of the study, this cefuroxime axetil incorporated bioactive glass blocks can be successfully used in clinical cases of osteomyelitis in veterinary as well as human orthopaedic surgery.     

Decolorization of Brilliant Blue G dye mediated by degradation of the microbial consortium of Galactomyces geotrichum and Bacillus sp.

A consortium-GB containing two microorganisms Galactomyces geotrichum MTCC 1360 and Bacillus sp. VUS was able to degrade sulfur-containing dye Brilliant Blue G, optimally at pH 9 and temperature at 50 °C. The ability of consortium-GB to work at higher temperature and pH ranges will help in using this consortium for removal of the dye from textile effluent. Malt extract, peptone and beef extract were found to be the best additional carbon and nitrogen sources. Brilliant Blue G caused enhancement of the riboflavin reductase among the enzyme activities studied. Biodegradation was confirmed by analyzing the product using UV–vis, HPLC, and FTIR. The GC–MS study revealed a pathway of Brilliant Blue G with release of (4-ethoxy-phenyl)-phenyl-amine and 3-ethylaminomethyl-benzenesulfonic acid as final metabolites formed by the consortium-GB. GC–MS analysis indicated the formation of 3-{[ethyl-(3-methyl-cyclohexa-2,5-dienyl)-amino]-methyl}-benzenesulfonic acid as a product by G. geotrichum MTCC 1360 alone and (4-benzylidene-3-methyl-cyclohexa-2,5-dienylidene)-methyl-amine by Bacillus sp. VUS alone. Phytotoxicity revealed nontoxic nature of the metabolites. These results indicate the high potential of the consortium-GB to serve as an excellent biomass for the use in Brilliant Blue G dye removal.     

Bioleaching of iron from highly contaminated Kaolin clay by Aspergillus niger

Kaolin is a clay mineral that has a wide application in the industry specially, in paper, ceramic, and porcelain manufacturing. One of the most important factors that affects the value of this raw material is its brightness. Unfortunately, with the iron oxides deposit on mineral particles during kaolin formation, much of this clay has become unusable for industries. So, several chemical methods have been applied in mineral processing plants to reduce these contaminants, but finding a more sustainable approach like biological methods have always attracted a great attention. In this work bioleaching of iron from a highly contaminated kaolin sample was carried out using two different strains of Aspergillus niger, and the effects of strain type, pulp density, and time of clay addition on the iron removal were investigated by employing a 2³ full factorial design. Finally, it is concluded that strain type has the most significant effect on the response; also, the highest removal extent was 42.8% that was obtained by using the strain isolated from pistachio shell, and at the pulp density of 20 g/l when the clay was added at the beginning of the experiments.     

Insights into the formation of microporous materials by in situ X-ray scattering techniques

Here we demonstrate the power of in situ scattering techniques in the understanding of formation of nanoporous aluminosilicate and aluminophosphate materials. We utilised a number of X-ray techniques, in particular, in situ energy dispersive X-ray diffraction (EDXRD) and small angle and wide angle X-ray scattering (SAXS/WAXS) techniques for this purpose. The in situ SAXS measurements show the formation of homogeneous precursors in the size of ca. 10 nm, prior to the crystallization of LTA. The crystal size is estimated by fitting the SAXS patterns with an equation for a cubic particle, and it is revealed that the final crystal size of the LTA depends on the synthesis temperature. Whereas, the crystallisation of CoAlPO-5, occurs through the formation of poly-dispersed particles with an average size of the precursor particle of ca. 50 nm. Also shown the effect of temperature and structure directing organic cations on the production of CoAlPO-5 materials.     

Photo-enhancement of Cr(VI) reduction by fungal biomass of Neurospora crassa

Various organisms such as fungus are capable of reducing Cr(VI) to less toxic Cr(III). However, light-induced Cr(VI) reduction by fungus is less reported and needs to be explored since anthropogenic or natural activities may bring these two reactants into a sunlit environment. In this study, the interactions and reaction mechanisms of Cr(VI) on a model fungus, Neurospora crassa, were evaluated in the presence or absence of light. The influence of ferric ion, a widely distributed metal, on Cr(VI) reduction by the fungus was also investigated under illumination. The results show that 20–54% of added Cr(VI) (96.2 μM) was removed by 1 g of dead fungal biomass (i.e., 1–2.7 mg Cr(VI) reduction by 1 g biomass) at pH 1–3, after 6 h reaction in the dark. However, 96.2 μM Cr(VI) disappeared completely (i.e., 5 mg Cr(VI) reduction by 1 g biomass) under the same reaction time and experimental conditions when light was present. The rapid disappearance of Cr(VI) in solution was due to the reduction of Cr(VI) by the excited biomass upon light absorption, and the rates of redox reactions increased with a decrease at pH. Cr(VI) reduction could be further increased with the addition of 89.5 μM Fe(III) because the formation of Fe(II) from the photolysis of Fe–organic complexes enhanced Cr(VI) reduction. Spectroscopic studies indicated that the amide, NH, and carboxyl groups of N. c.-biomass may be responsible for initiating Cr(VI) reduction; comparatively, the cyclo-carbons of chitin, glucan, and their derivatives were more persistent to the oxidation by Cr(VI). Accordingly, fungi containing high amount of carboxyl, amide, and NH groups may be preferable as efficient reductants for scavenging Cr(VI) from environment. Upon the absorption of a renewable light source, Cr(VI) could be converted rapidly by the biomaterials to the less toxic Cr(III).     

Adsorption characteristics of metal ions by CO2-fixing Chlorella sp. HA-1

Single and binary metal systems were employed to investigate the removal characteristics of Pb²⁺, Cu²⁺, Cd²⁺, and Zn²⁺ by Chlorella sp. HA-1 that were isolated from a CO₂ fixation process. Adsorption test of single metal systems showed that the maximum metal uptakes were 0.767 mmol Pb²⁺, 0.450 mmol Cd²⁺, 0.334 mmol Cu²⁺ and 0.389 mmol Zn²⁺ per gram of dry cell. In the binary metal systems, the metal ions on Chlorella sp. HA-1 were adsorbed selectively according to their adsorption characteristics. Pb²⁺ ions significantly inhibited the adsorption of Cu²⁺, Zn²⁺, and Cd²⁺ ions, while Cu²⁺ ions decreased remarkably the metal uptake of Cd²⁺ and Zn²⁺ ions. The relative adsorption between Cd²⁺ and Zn²⁺ ions was reduced similarly by the presence of the other metal ions.     

Preparative separation and purification of rosavin in Rhodiola rosea by macroporous adsorption resins

Rosavin is one of the main bioactive components in Rhodiola rosea L. with known pharmacological effects. In this study, a simple method for preparative separation and purification of rosavin from R. rosea L. was developed with macroporous adsorption resins. The adsorption isotherms and desorption performances of some resins have been determined and compared. Depending on its hydrophobic force, HPD-200 resin, a styrene-divinylbenzene (SDVB) copolymer, offers the best adsorption and desorption properties for rosavin based on the research results, its adsorption data fit best to the Langmuir adsorption model. Dynamic adsorption and desorption was performed on HPD-200 resin packed in a glass column to obtain optimal parameters for the separation of rosavin. The optimum conditions were as follow. The volume, concentration, bed height and flow rate of loading sample were 4 bed volumes (BV), 0.24 mg/mL, 30 cm and 2 BV/h, respectively, at 25 °C; desorption was performed successively with 30% ethanol of 4 bed volumes, 40% ethanol of 2.5 bed volumes and 60% ethanol of 3 bed volumes. After one run treatment with HPD-200, the rosavin content in the product was increased from 0.69% to 11.02% with a recovery of 82.46%. In this case, the process throughout is 1.34 g rosavin/L adsorbent/day, solvent usage is 7.14 L ethanol/g rosavin. The simple purification scheme avoids toxic organic solvent and thus, increases the safety of the process with a potential industrial application prospect.     

Non-uniform current density distribution at a rde. Observation by means of photographing electrochemiluminescence

Equations for the current at a rde have been derived with the presumption that equal accessibility for any place on the electrode surface. An example of non-homogeneous current density distribution at the Pt-rde was observed in photographs of electrogenerated chemiluminescence (ECL) where the intensity of emission changes with the distance from the centre and depends on the type of the process and on the rotation velocity.     

Influence of montmorillonite on cadmium accumulation in carp, Carassius auratus

The present study was designed to test the influence of montmorillonite (MMT) on cadmium accumulation in different tissues of Carassius auratus. 180 normal healthy C. auratus were randomly divided into four groups. They were fed with normal diet, normal diet supplemented with MMT (0.5%), high-cadmium (cadmium chloride, 120 mg/kg) diet and high-cadmium diet supplemented with MMT (0.5%). After 60 days, cadmium concentration in several tissues were measured by eletrothermic atomic absorption spectrophotometry, metallothionein contents were determined using the Cd-chelex assay and histopathological alterations of kidney were observed. MMT inhibited cadmium accumulation in kidney, intestine, liver, spleen, blood, gills, spermary, ovary, brain, bone and muscles of C. auratus. Metallothionein levels in liver, intestine and muscle decreased and pathological changes of kidney were reduced by MMT addition. Thus, MMT protected tissues of C. auratus from cadmium accumulation and damage.     

Numerical study of co-firing coal and Cynara cardunculus in a 350 MWe utility boiler

In this work, a CFD numerical study of co-firing coal and cynara in a 350 MWe utility boiler is presented. The most influent operational factors related to the biomass feeding conditions such as biomass mean particle size, level of substitution of coal by biomass and feeding location in the furnace, are analyzed, determining their influence in the combustion process. Validation of the simulations is performed using measurements gathered at the plant. Results from the study show interesting conclusions for their implementation in the power plant, suggesting recommendable limits in the maximum biomass substitution level and particle size in order to keep a reasonable boiler efficiency, and pointing out the outstanding influence of the biomass injection location discussing thermal and fluid-dynamic implications and the possibility of introducing retrofitted or specific biomass burners.     

Deactivation handling in a high-throughput kinetic study of o-xylene hydrogenation

The objective of the study is to develop an HT methodology to enable kinetic modeling of diverse catalysts. The reaction of o-xylene hydrogenation is selected as a probe reaction to evaluate the “metallic” features of a library of about 80 diverse bimetallic catalysts. A major issue to overcome is deactivation phenomena which are catalyst dependent and which cannot a priori be predicted. A prerequisite is therefore to handle correctly deactivation processes for accessing intrinsic kinetic parameters. For this purpose, an adapted screening strategy is developed, using a proprietary 16 channels multi-tubular reactor which enables to test catalysts at the same time-on-stream. Original data treatment procedures are implemented in order to correct observed data from deactivation phenomena for the calculation of kinetic parameters. Effects of metal nature, dopants and supports on deactivation rate are analyzed using a statistical approach, and a tentative classification of deactivation processes based on coke analyses performed on aged materials is provided.     

Electrochemical insight into the mechanism of electron transport in biofilms of Geobacter sulfurreducens

Electroactive bacterial biofilms can be produced on a polarized electrode by forcing its use as the final electron acceptor for bacterial respiration. This strategy offers the researcher the unique possibility to control the respiration process with extreme precision. The production of current, the accumulation of charge and the conducting properties of electroactive biofilms has been interrogated in this work through very basic electrochemical techniques including chronopotentiometry, chronoamperometry and cyclic voltammetry. Presented results indicate that charge can be accumulated in the biofilm conductive network, that network conductivity does not represent a limit for current production and that both the steady state current and the amount of accumulated charge depend on the redox state of cytochromes wiring the cells to the electrode. A model of biofilm conduction is presented as well.     

Detailed kinetic modeling of NOx adsorption and NO oxidation over Cu-ZSM-5

Detailed kinetic modeling was used in combination with flow reactor experiments to investigate the NO_x adsorption/desorption and NO oxidation over Cu-ZSM-5. NO oxidation is likely an important step for selective catalytic reduction (SCR) using urea and hydrocarbons, and thus was investigated separately. First the NO₂ adsorption on Brönstedt acid sites in H-ZSM-5 was modeled using an NO₂ temperature programmed desorption (TPD) experiment. These results, together with the results of the NO₂ TPD and NO oxidation experiments, were used in developing the model for Cu-ZSM-5. A substantial amount of NO₂ was adsorbed on the catalyst. However, the results from a corresponding NO TPD experiment showed that only very small amounts of NO were adsorbed on the catalyst and therefore this step was not included in the model. The model consists of reversible steps for NO₂ and O₂ adsorption, O₂ dissociation, NO oxidation and two steps for nitrate formation. The first nitrate formation step was disproportionation of NO₂ to form NO and nitrates. This step enabled us to describe the NO production during NO₂ adsorption. Further, in the reverse step the NO reacts with the nitrates and decreased their stability. Without this step the nitrates blocked the surface resulting in to low NO oxidation activity. However, we observe that nitrates can be decomposed also without the presence of NO and in the second reversible step were the nitrates decomposed to form NO₂ and oxygen on the copper. These steps enabled us to describe both the TPD and activity measurement results. NO oxidation was observed even at room temperature. Interestingly, the NO₂ decreased when increasing the temperature up to 100 °C and then increased as the temperature increased further. We suggest that this low-temperature NO oxidation occurs with species loosely bound on the surface and that is included in the detailed mechanism. An additional NO₂ TPD at 30 °C was also modeled to describe the loosely bound NO₂ on the surface. The detailed model correctly describes NO₂ storage, NO oxidation and low-temperature NO oxidation.     

Synthesis and characterization of per-substituted spermine-bridged cyclophosphazene derivatives: the first example of syn/anti conformational polymorphism in a bridged cyclophosphazene

The synthesis and characterization of a series of per-substituted spermine-bridged cyclophosphazene derivatives are reported based on the known compound [N₃P₃X₄(NHCH₂CH₂CH₂N)CH₂CH₂]₂, (1a) (where X = Cl), to give a number of new compounds (1b–1h) in which X = OPh, [spiro-O(CH₂)₃O]_0.5, OCH₂CF₃, NHPh, NC₄H₈, Ph and NHBu^t, respectively. Two synthetic routes were utilized: (i) using the chloro-precursor 1a in nucleophilic substitution reactions with a variety of anionic and neutral nucleophiles to give compounds 1b–1f and (ii) reaction of spermine with the appropriate di-gem tetrasubstituted cyclophosphazene to give compounds 1g and 1h. Bridged compounds such as 1a–1h may exist as syn or anti conformers in the solid state and the first example of syn and anti conformational polymorphism is reported for a bridged cyclophosphazene, viz. for compound 1a.     

Adsorption and antibacterial effect of copper-exchanged montmorillonite on Escherichia coli K88

Calcium montmorillonite (Ca-MMT), sodium montmorillonite (Na-MMT) and acid-activated montmorillonite (AAM), and their Cu²⁺-exchanged montmorillonites (Cu-MMT), Cu*Ca-MMT, Cu*Na-MMT and Cu*AAM, were used to study the antibacterial activity on Escherichia coli K₈₈. AAM, Na-MMT and Ca-MMT showed some ability to reduce bacterial plate counts by 37.4%, 13.4% and 14.2%, respectively. Exchanging the montmorillonite with Cu²⁺ enhanced the antibacterial activity. The Cu*AAM, Cu*Na-MMT and Cu*Ca-MMT reduced the bacterial plate counts by 98.6%, 97.5% and 95.6%. Attempts were made to study the desorption of Cu²⁺ by washing with sterile physiological saline solution for 24 h. The washing solutions did not show a significant reduction of the bacterial counts, while the washed Cu-MMT retained their full antibacterial activity. Results from time-depending studies showed that the reduction of the bacterial counts by Cu-MMT increased during 24 h. The ranking of antibacterial activity of the three Cu-MMT was as Cu*AAM > Cu*Na-MMT > Cu*Ca-MMT. E. coli thrived optimally in a pH range from 5 to 7. Beyond this range, the bacterial counts decreased as the pH reduced the viability of the bacteria. The ranking of antibacterial activity of Cu-MMT was not affected by pH. The mechanism by which bacterial counts are reduced may involve the enhanced affinity of Cu-MMT for E. coli K₈₈ and the antibacterial activity of Cu²⁺.     

Vermiculites intercalated with Al2O3 pillars and modified with transition metals as catalysts of DeNOx process

Vermiculites intercalated with alumina pillars and modified with transition metals (Cu, Fe) were studied as catalysts of selective reduction of NO with ammonia. Prior to the pillaring process, a raw vermiculite was treated with a solution of nitric acid and then citric or oxalic acid in order to reduce the overall charge of layers. This modification was necessary for a successful pillaring of the clay. Transition metals (Fe, Cu) were deposited on the surface of the modified vermiculites by an ion-exchange method. The obtained samples were characterized with respect to composition (EPMA), structure (XRD), texture (BET) and chemical nature of deposited transition metal species (UV–vis–DRS). The vermiculite based materials have been found to be active and selective catalysts of the DeNOx process. The Cu-containing samples were catalytically active at lower temperatures than the pillared clays modified with iron. A side reaction of ammonia oxidation by oxygen decreased the effectiveness of the DeNOx process in the high temperature range.     

Valorisation of Jatropha curcas L. plant parts: Nut shell conversion to fast pyrolysis oil

The biorefinery concept is a very powerful concept to optimise the conversion of biomass resources to value-added products with a minimum loss of energy and mass and a maximum overall value of the production chain. We here report our activities on the application of this concept to valorise the Jatropha curcas L. (JCL) shrub, a (sub)-tropical plant producing a high quality plant oil that may be converted to biodiesel in good yields. Within a research consortium of Dutch and Indonesian researchers, we are exploring high added value outlets for byproducts of the JCL plant (leaves, latex) and seed processing units (press cake). As an example, we here report fast pyrolysis experiments to convert the nut shells to fast pyrolysis oil, a promising second generation biofuel. The fast pyrolysis experiments were carried out in a continuous bench scale pyrolyser at a throughput of 2.27 kg/h at 480 °C and atmospheric pressure. The nut shell pyrolysis oil was obtained in 50 wt.% yield, the remainder being char (23 wt.%), gas (17 wt.%) and ash. Relevant product properties of the oil were determined and indicate that the oil is inhomogeneous in nature.     

Operando FTIR study of the photocatalytic oxidation of acetone in air over TiO2–ZrO2 thin films

Operando FTIR spectroscopy has been used to study the photocatalytic oxidation of acetone vapors over semiconductors films containing TiO₂ and ZrO₂. Preparation of these coatings was carried out by dipping a silicon wafer in stable sols containing particles of TiO₂, Ti_1−xZr_xO₂, or a mixture of ZrO₂ and TiO₂. These differences in chemical composition and phase homogeneity were selected in order to determine their effect on the photocatalytic performance. A transmission cell specifically designed for in situ studies of photocatalytic coatings was utilized for the FTIR experiments under reaction conditions. In contrast with investigations with powdered photocatalysts, the use of thin films guarantees that the whole semiconductor is irradiated, and for that reason purely photochemical reactions are monitored. Acetone adsorption takes place molecularly and is higher on the Ti_1−xZr_xO₂ coating. This fact is very likely related to the higher specific surface of the samples containing Zr. However, the maximum photocatalytic rate for acetone degradation corresponds to the films composed by a binary mixture of TiO₂ and ZrO₂. On the other hand, remarkable differences on the type and concentration of intermediates appearing as a result of the photocatalytic oxidation of acetone are found for the coatings studied. A simple kinetic model was applied to analyze the evolution of both gas phase and surface species. The parameters obtained indicate that each specific surface process is affected in a different way by the variation in the composition of the photoactive films.