Showing papers in "Journal of Chemical Technology & Biotechnology in 2007"
TL;DR: In this article, the second-order transition temperature of binary copolymers is derived from the two secondorder transition temperatures of the pure polymers and their coefficients of expansion in the glassy and rubbery states.
Abstract: Theoretical and practical evidence is put forward to show that copolymers can be treated like solutions of small molecules in the interpretation of packing phenomena, and that ideal volume-additivity of the repeating units in copolymers is frequently realized. On this basis equations are derived for predicting θ, the second-order transition temperature, of binary copolymers from the two second-order transition temperatures of the pure polymers and their coefficients of expansion in the glassy and rubbery states. Previous mechanistic theories of the second-order transition temperature of such copolymers are thus superseded by a general reduction of the problem to the mechanism of thermal expansion. Practical applications to the choice of monomers in producing synthetic rubbers are outlined, and attention is drawn to the importance of second-order transitions in kinetic measurements on the reactions of polymers.
2,034 citations
TL;DR: Among the microorganisms that have been evaluated for lignocellulosic hydrolysate ethanol fermentation, the yeast Saccharomyces cerevisiae appears to be the least sensitive.
Abstract: During hydrolysis of lignocellulosic biomass, monomeric sugars and a broad range of inhibitory compounds are formed and released. These inhibitors, which can be organized around three main groups, furans, weak acids and phenolics, reduce ethanol yield and productivity by affecting the microorganism performance during the fermentation step. Among the microorganisms that have been evaluated for lignocellulosic hydrolysate ethanol fermentation, the yeast Saccharomyces cerevisiae appears to be the least sensitive. In order to overcome the effect of inhibitors, strategies that include improvement of natural tolerance of microorganism and use of fermentation control strategies have been developed. An overview of the origin, effects and mechanisms of action of known inhibitors on S. cerevisiae is given. Fermentation control strategies as well as metabolic, genetic and evolutionary engineering strategies to obtain S. cerevisiae strains with improved tolerance are discussed.
984 citations
TL;DR: In this paper, a method for calculating the pore size distribution from adsorption isotherms on porous solids is described, which is more exact and less tedious to use than some previously described methods.
Abstract: A method for calculating the pore size distribution from adsorption isotherms on porous solids is described, which is more exact and less tedious to use than some previously described methods. The method of compiling tables for calculation is shown and an example of such a calculation is given.
809 citations
TL;DR: In this paper, various applications of polyhydroxyalkanoates are discussed, covering areas such as medicine, agriculture, tissue engineering, nanocomposites, polymer blends and chiral synthesis.
Abstract: Increased and accelerated global economic activities over the past century have led to interlinked problems that require urgent attention. The current patterns of production and consumption have raised serious concerns. In this context, greater emphasis has been put on the concept of sustainable economic systems that rely on technologies based on and supporting renewable sources of energy and materials. Average UK households produce around 3.2 million tonnes of packaging waste annually whereas 150 million tonnes of packaging waste is generated annually by industries in the UK. Hence, the development of biologically derived biodegradable polymers is one important element of the new economic development. Key among the biodegradable biopolymers is a class known as polyhydroxyalkanoates. Polyhydroxyalkanoates (PHAs) are a family of polyhydroxyesters of 3-, 4-, 5- and 6-hydroxyalkanoic acids, produced by a variety of bacterial species under nutrient-limiting conditions with excess carbon. These water-insoluble storage polymers are biodegradable, exhibit thermoplastic properties and can be produced from renewable carbon sources. Thus, there has been considerable interest in the commercial exploitation of these biodegradable polyesters. In this review various applications of polyhydroxyalkanoates are discussed, covering areas such as medicine, agriculture, tissue engineering, nanocomposites, polymer blends and chiral synthesis. Overall this review shows that polyhydroxyalkanoates are a promising class of new emerging biopolymers.
784 citations
TL;DR: In this article, a method is given for estimating the cohesive energy densities of polymers from a set of additive constants, and good agreement is found between values so calculated and values obtained by swelling measurements.
Abstract: The solubility of a polymer in a non-polymeric liquid depends mainly on the heat of mixing. When no polar forces are concerned, the cohesive energy densities of polymer and solvent must be close; a method is given for estimating the cohesive energy densities of polymers from a set of additive constants, and it is shown that good agreement is found between values so calculated and values obtained by swelling measurements. The effects of dipole interactions and hydrogen bonding are also discussed. The solubility of polyvinyl chloride in a number of solvents is considered, and correlated with both the cohesive energy density of the solvent and its ability to form hydrogen bonds.
767 citations
TL;DR: In this paper, it is shown that there are three components in a mixing process: convection, diffusion and shear, and a statistically satisfactory expression evolved for the state of a mixture.
Abstract: It is shown that there are three components in a mixing process: convection, diffusion and shear. The concepts involved in analysing complete and partial mixtures are examined and a statistically satisfactory expression evolved for the state of a mixture. A number of theories of mixing rate are examined and compared with the few published experimental results, and a new theoretical treatment is offered based on diffusion theory. This is shown to be in at least as good agreement with fact as existing theories, and to provide a better basis for extension to more complex cases.
560 citations
TL;DR: In this paper, the relative humidity maintained over saturated and unsaturated salt solutions and of some salt hydrate mixtures have been collated from the literature over a wide range of temperature.
Abstract: The relative humidities maintained over saturated and unsaturated salt solutions and of some salt hydrate mixtures have been collated from the literature over a wide range of temperature. Results are presented for 38 saturated salt solutions, and details listed for salts which are recommended as suitable for humidity control. The control of humidity in the laboratory by the use of salt solutions is critically discussed.
515 citations
TL;DR: The capacitance method can be used for routine testing of the water-uptake of paints only on a type of paint known to give good agreement between the two methods; where applicable, it has decided advantages over gravimetric methods as discussed by the authors.
Abstract: An electrical capacitance method of estimating the water-uptake of paint films on metal immersed in sea-water has given, for many paint formulations, values agreeing with those obtained by a gravimetric method. For a few paints, however, pronounced disagreement was shown between values obtained by the two methods.
Theoretical considerations show that such differences indicate, in general, a type of water distribution within the film departing considerably from the random, uniform distribution assumed in calculating the ‘capacitance’ values. Several types of distribution are discussed.
The capacitance method can be used for routine testing of the water-uptake of paints only on a type of paint known to give good agreement between the two methods; where applicable, it has decided advantages over gravimetric methods.
488 citations
TL;DR: Metals and organic contaminants, present in the water-column, sediment or food, are readily accumulated by aquatic organisms and should be used as part of an integrated programme of pollution monitoring, involving also general measurements of biological damage and animal health, and analysis of chemical contaminants in the biota and environment.
Abstract: Metals and organic contaminants, present in the water-column, sediment or food, are readily accumulated by aquatic organisms Exposure to and toxic effects of contaminants can be measured in terms of the biochemical responses of the organisms—so-called molecular biomarkers The applications, advantages and limitations of such diagnostic and prognostic tests are discussed The hepatic biotransformation enzyme cytochrome P4501A in fish and other vertebrates is specifically induced by organic contaminants such as aromatic hydrocarbons, PCBs and dioxins, and is used as a biomarker of exposure to organic pollution Its induction is involved in chemical carcinogenesis via catalysis of the covalent binding of organic contaminants to DNA (DNA-adducts) P4501A-induction, measured as enzyme activity, enzyme amount, or mRNA, has been successively used in many field studies, involving some 27 fish species, in USA and Europe Metallothioneins (MTs) bind and are specifically induced by metals such as Cd, Hg, Ag and Cu, and are used in both vertebrates and invertebrates as a biomarker for metal exposure Bulky, hydrophobic DNA-adducts are used as a biomarker for organic contaminant damage MTs (measured at protein and mRNA levels) and DNA-adducts (32P-postlabelling method) have been applied less extensively in the field than P4501A, but the results are similarly encouraging Biomarkers should be used as part of an integrated programme of pollution monitoring, involving also general measurements of biological damage and animal health, and analysis of chemical contaminants in the biota and environment Commercial availability of antibodies and mRNA probes will accelerate the widespread application of these molecular biomarkers
395 citations
TL;DR: Bioremediation has become a major method employed in restoration of oil-polluted environments that makes use of natural microbial biodegradative activities and the success of seeding oil spills with microbial preparations is ambiguous.
Abstract: Bioremediation has become a major method employed in restoration of oil-polluted environments that makes use of natural microbial biodegradative activities. Bioremediation of petroleum pollutants overcomes the factors limiting rates of microbial hydrocarbon biodegradation. Often this involves using the enzymatic capabilities of the indigenous hydrocarbon-degrading microbial populations and modifying environmental factors, particularly concentrations of molecular oxygen, fixed forms of nitrogen, and phosphate to achieve enhanced rates of hydrocarbon biodegradation. Biodegradation of oily sludges and bioremediation of oil-contaminated sites has been achieved by oxygen addition—e.g., by tilling soils in landfarming and by adding hydrogen peroxide or pumping oxygen into oiled aquifers along with addition of nitrogen- and phosphorous-containing fertilizers. The success of seeding oil spills with microbial preparations is ambiguous. Successful bioremediation of a major marine oil spill has been achieved based upon addition of nitrogen and phosphorus fertilizers.
364 citations
TL;DR: In this article, the ability of activated carbon to remove dyestuffs from aqueous solutions has been investigated, and several factors have been studied, namely, agitation, initial dye concentration, adsorbent concentration, ad-size range, dye solution temperature, pH of solution and salt concentration.
Abstract: The ability of one activated carbon to remove dyestuffs from aqueous solutions has been investigated. The range of dyestuffs includes acidic, basic, disperse and direct dyes, and several factors have been studied, namely, agitation, initial dye concentration, adsorbent concentration, adsorbent particle-size range, dye solution temperature, pH of solution and salt concentration.
TL;DR: In this article, an acid-promoted direct methanolysis of cellular biomass of oleaginous yeasts and filamentous fungi was used to achieve up to 98% yield with reaction conditions of 70 degrees C, under ambient pressure for 20h and a dried biomass to methanol ratio 1:20 (w/v).
Abstract: Biodiesel is a renewable fuel conventionally prepared by transesterification of pre-extracted vegetable oils and animal fats of all resources with methanol, catalyzed by strong acids or bases. This paper reports on a novel biodiesel production method that features acid-promoted direct methanolysis of cellular biomass of oleaginous yeasts and filamentous fungi. The process was optimized for tuning operation parameters, such as methanol dosage, catalyst concentration, reaction temperature and time. Up to 98% yield was reached with reaction conditions of 70 degrees C, under ambient pressure for 20h and a dried biomass to methanol ratio 1:20 (w/v) catalyzed by either 0.2 mol L-1 H2SO4 or 0.4 mol L-1 HCl. Cetane numbers for these products were estimated to range from 56 to 59. This integrated method is thus effective and technically attractive, as dried microbial biomass as feedstocks omits otherwise tedious and time-consuming oil extraction processes.
TL;DR: In this paper, the rates of adsorption of a basic dye, Astrazone Blue, and an acidic dye, Telon Blue, on wood have been studied, and the diffusion coefficients vary from 6×10−13 cm2 s−1 to 18×10 − 13 cm2 S−1 for AstrazONE Blue at 18°C and from 3 × 10−13cm2 s −1 to 8 × 10 −13 cm 2 s− 1 for Telon blue at 18 °C.
Abstract: The rates of adsorption of a basic dye, Astrazone Blue, and an acidic dye, Telon Blue, on wood have been studied. The rate controlling step is mainly intraparticle diffusion, although a small resistance due to a boundary layer is experienced. The activation energies for the adsorption of Astrazone Blue and Telon Blue on wood are 16.8 kJ mol−1 and 9.6 kJ mol−1, respectively. The diffusion coefficients vary from 6×10−13 cm2 s−1 to 18×10−13 cm2 s−1 for Astrazone Blue at 18°C and from 3 × 10−13 cm2 s−1 to 8 × 10−13 cm2 s−1 for Telon Blue at 18°C. The variation in diffusivities is attributed to boundary layer effects.
TL;DR: In this article, the deformation of bitumens can be calculated as a function of stress, time and temperature, by means of a nomograph, which enables the average behaviour of a given grade to be calculated with an accuracy sufficient for engineering purposes.
Abstract: After dynamic and static experiments on the mechanical behaviour of bitumens an attempt was made to incorporate all the essential factors into a simple system. This was found to be possible in the form of a nomograph, by means of which the deformation of bitumens can be calculated as a function of stress, time and temperature. Origin or method of manufacture proved to be of less importance than hardness and rheological type. For correlation with standard test-methods, the ring-and-ball temperature and the penetration index were found to be suitable parameters. The nomograph enables the average behaviour of a given grade to be calculated with an accuracy sufficient for engineering purposes.
Another feature of the nomograph is that it creates the possibility of giving an interpretation of other routine tests. By way of example both penetration and Fraass breaking test are discussed.
TL;DR: Making chemical derivatives is a way to alter the metal interacting characteristics of chitosan, which possesses general coagulant/flocculant characteristics towards bio-molecules and surfaces.
Abstract: Chitosan is a natural polycationic polymer which possesses valuable properties as a metal recovering and water purifying agent. Applications are waste water treatment for heavy metal and radio isotope removal and valuable metal recovery, potable water purification for reduction of unwanted metals, agriculture--controlled release of trace metals essential to plant growth, food--complex binding of iron in precooked food to reduce 'warmed-over flavour'. The interactions of metals with chitosan are complex, probably simultaneously dominated by adsorption, ion-exchange and chelation. To study this it is of utmost importance to work with well characterized chitosans. This has been a problem as available characterizing methodology is limited. Degree of polymerization and deacetylation and the distribution of acetyl groups along the polymer chain is of crucial importance for chitosan metal interacting characteristics. Making chemical derivatives is a way to alter the metal interacting characteristics of chitosan. Chitosan possesses general coagulant/flocculant characteristics towards bio-molecules and surfaces.
TL;DR: In this article, a modification of the Winkler titration technique was used to determine the solubility of oxygen in pure and in saline water between 2°and 40°.
Abstract: The solubility of oxygen in pure and in saline water between 2°and 40°has been determined by using a modification of the Winkler titration technique. The values found have, in some cases, been lower than those generally accepted by as much as 4%. On applying these new solubilities to the determination of rates of solution in well mixed water, satisfactory agreement with the Adeney & Becker law of aeration is obtained.
TL;DR: In this article, the adsorption capacity of each dye-adsorbent system has been determined and the relative costs of dye removal were reported based on adsorptive capacity only.
Abstract: A number of low-cost materials (natural clay, bagasse pith and maize cob) have been used as adsorbents for dyestuffs (Astrazon Blue, Maxilon Red and Telon Blue) in aqueous solutions. The adsorption capacity for each dye-adsorbent system has been determined. The relative costs of dye removal were reported based on adsorption capacity only. The following results were found. First, the relative cost of the removal of Astrazon Blue using natural clay, bagasse pith and maize cob was found to be only 1·7%, 3·9% and 4·1% that of carbon respectively. Second, the relative cost of the removal of Maxilon Red using natural clay, maize cob and bagasse pith was found to be only 2·4%, 8·3% and 10·3% that of carbon respectively. Last, the relative cost of the removal of Telon Blue using maize cob, natural clay and bagasse pith was found to be only 2·9%, 3·0% and 5·2% that of carbon respectively.
TL;DR: The application of photocatalysis for the removal of pharmaceuticals and endocrine-disrupting compounds for wastewater is comprehensively surveyed in this article, where the assessment places emphasis on the process fundamentals, advantages, and disadvantages of the technology.
Abstract: Widespread concerns continue to be raised about the increasing presence of emerging contaminants in the environment. Such compounds include a wide range of persistent organic chemicals, including pharmaceuticals and endocrine-disrupting compounds whose effects are poorly known, often because they have only begun to enter the environment and are showing up in wastewater treatment plants. The occurrence and behavior of these compounds in wastewater are key issues with regard to water reclamation and reuse. Treatment plants are now faced with the challenge of removing the compounds from their effluent before they enter natural waterways. In this regard, photocatalysis is a promising technology for wastewater treatment that offers many advantages over conventional and some advanced treatment options. The application of photocatalysis for the removal of pharmaceuticals and endocrine-disrupting compounds for wastewater is comprehensively surveyed in this paper. This treatment technology is not intended to replace conventional systems but to supplement for higher-quality effluent. The assessment places emphasis on the process fundamentals, advantages, and disadvantages of the technology. It also focuses on the current limitations and future research needs. Copyright © 2007 Society of Chemical Industry
TL;DR: In this article, the binding of several metals by waste biomass of Streptomyces noursei was investigated and the binding capacity and selectivity of metal binding by biomass are important qualities for practical use.
Abstract: The binding of several metals by waste biomass of Streptomyces noursei was investigated. With respect to the binding capacity, the following order was observed: Ag > Cr > Pb > Cu > Zn > Cd > Co > =Ni. The sorption of metal ions increased with the increasing initial concentration of metal. The adsorption equilibrium of copper, lead and chromium sorption, and silver sorption at low concentration can be described by the Freundlich and Langmuir models. The possibilities for desorbing the metals from loaded biomass and the repeated use of biomass were investigated. The influence of various ions in water on metal sorption was tested. The metal capacity and selectivity of metal binding by biomass are important qualities for practical use.
TL;DR: In this article, the authors broadly review carbon allotropes, with emphasis on some recent results and applications, particularly in the field of high surface area amorphous carbons.
Abstract: Carbon offers unmatched versatility among the elements of the periodic table. Depending on its hybridization state and atomic arrangement, carbon forms the layered semiconductor graphite, the insulator diamond, with its unmatched hardness, the high surface area amorphous carbons, and the nano-sized fullerenes and nanotubes, among others. This paper broadly reviews carbon allotropes, with emphasis on some recent results and applications, particularly in the field of high surface area amorphous carbons. Copyright © 2007 Society of Chemical Industry
TL;DR: The chemical industry that underpins most industries needs to respond to these challenges The chemical manufacturing and user industries face an unprecedented range and intensity of drivers for change, the greatest of which, REACH (Registration, Evaluation and Authorisation of Chemicals) has yet to bite In order to address the key issues of switching to renewable resources, avoiding hazardous and polluting processes, and manufacturing and using safe and environmentally compatible products, we need to develop sustainable and green chemical product supply chains.
Abstract: The material needs of society are reaching a crisis point The demands of a growing and developing world population will soon exceed the capacity of our present fossil resource based infrastructure In particular, the chemical industry that underpins most industries needs to respond to these challenges The chemical manufacturing and user industries face an unprecedented range and intensity of drivers for change, the greatest of which, REACH (Registration, Evaluation and Authorisation of Chemicals) has yet to bite In order to address the key issues of switching to renewable resources, avoiding hazardous and polluting processes, and manufacturing and using safe and environmentally compatible products, we need to develop sustainable and green chemical product supply chains For organic chemicals and materials these need to operate under agreed and strict criteria and need to start with widely available, totally renewable and low cost carbon—the only source is biomass and the conversion of biomass into useful products will be carried out in biorefineries Where these operate at present, their product range is largely limited to simple materials (eg cellulose), chemicals (eg ethanol) and bioenergy/biofuels Second generation biorefineries need to build on the need for sustainable chemical products through modern and proven green chemical technologies such as bioprocessing, controlled pyrolysis, catalysis in water and microwave activation, in order to make more complex molecules and materials on which a future sustainable society will be based Copyright © 2007 Society of Chemical Industry
TL;DR: In this article, a batch test with SHARON sludge showed that ammonium is the actual substrate and nitrous acid rather than nitrite is an actual inhibitor of the ammonium oxidation in the SHARON process.
Abstract: The SHARON (Single reactor High activity Ammonia Removal Over Nitrite) process is an innovative process that improves the sustainability of wastewater treatment, especially when combined with an Anammox process. It aims at ammonium oxidation to nitrite only, while preventing further nitrate formation. In order to optimize this process by means of modelling and simulation, parameters of the biological processes have to be assessed. Batch tests with SHARON sludge clearly showed that ammonia rather than ammonium is the actual substrate and nitrous acid rather than nitrite is the actual inhibitor of the ammonium oxidation in the SHARON process. From these batch tests the ammonia affinity constant, the nitrous acid inhibition constant and the oxygen affinity constant were determined to be 0.75mgNH3-N L −1 ,2 .04mgHNO2-N L −1 and 0.94mgO2 L −1 . The influence of pH and temperature on the oxygen uptake rate of SHARON biomass was determined, indicating the existence of a pH interval between 6.5 and 8 and a temperature interval from 35 to 45 ◦ C where the biomass activity is maximal. The kinetic parameters of the SHARON process were determined based on batch experiments. These parameters can now be implemented in a simulation model for further optimization of the SHARON process. 2007 Society of Chemical Industry
TL;DR: A spectra-structure correlation chart for phosphorus compounds is presented in this paper, and the existing evidence for these correlations is summarized in Table 1 : 1.1 The use of this data for qualitative identification is discussed, and examples of the use of the pressed disc technique for quantitative work.
Abstract: A spectra-structure correlation chart for phosphorus compounds is presented, and the existing evidence for these correlations is summarized
Powdered phosphate salts absorb in a number of discrete regions which are characteristic of the type of anion present The use of this data for qualitative identification is discussed, and examples are given of the use of the pressed disc technique for quantitative work
TL;DR: In this article, the authors studied the biosynthesis of ammonium lactate, a product of lactic acid fermentation, from corn and glucose at five different pH values of 5.4 to 7.8.
Abstract: The biosynthesis of ammonium lactate, a product of lactic acid fermentation was studied from corn and glucose at five different pH values of 5.4 to 7.8. In the glucose fermentations, a 100% conversion of substrate was obtained resulting in a maximum lactic acid production yield of 93.2%. The optimum pH for the maximum volumetric rate of lactic acid biosynthesis (1.56 g dm−3 h−1) was between 6.0 and 6.5. The corn fermentations were slower than the glucose fermentations with a resulting lactic acid yield of 67.5%. Hydrolysis of corn by enzymatic or chemical methods as well as the use of ammonium hydroxide for pH control increased both the final concentration and the rates of lactic acid production. An enhanced yield of more than 90% was finally obtained in the corn fermentations. A logistic model adequately described the kinetics of biomass growth, lactic acid production and sugar utilization in the glucose fermentations at different pH values. The dynamics of lactic acid formation in the corn fermentations were also successfully described by the developed model. The dependence of the model parameters on pH was investigated.
TL;DR: In this article, the optimal use of bio-ethanol in a longer perspective is discussed, and the question is: what will be the optimal application of bioethanol from a long-term perspective?
Abstract: Increasing amounts of bioethanol are being produced from fermentation of biomass, mainly to counteract the continuing depletion of fossil resources and the consequential escalation of oil prices. Today, bioethanol is mainly utilized as a fuel or fuel additive in motor vehicles, but it could also be used as a versatile feedstock in the chemical industry. Currently the production of carbon-containing commodity chemicals is dependent on fossil resources, and more than 95% of these chemicals are produced from non-renewable carbon resources. The question is: what will be the optimal use of bioethanol in a longer perspective? Copyright © 2007 Society of Chemical Industry
TL;DR: In this paper, the dissolution of mild steel by warm sulphuric acid with and without organic inhibiting additions has been studied by means of simultaneous measurements of corrosion rate and corrosion potential, and by the determination of true anodic and cathodic polarization curves in the neighbourhood of the natural corrosion potential.
Abstract: The dissolution of mild steel by warm sulphuric acid with and without organic inhibiting additions has been studied by means of simultaneous measurements of corrosion rate and corrosion potential, and by the determination of true anodic and cathodic polarization curves in the neighbourhood of the natural corrosion potential.
Quinoline, 2: 6-dimethylquinoline, α- and β-naphthoquinolines, N-ethylquinoline, thiourea, methyl-thiourea, ethylthiourea and o-, m- and p-tolylthioureas inhibit the dissolution of mild steel by 5% (w/v) sulphuric acid at 70° and 40°, being increasingly effective in the order given above. The quinolines are primarily anodic inhibitors, but at high concentrations they limit the cathodic reaction also; the thioureas inhibit both cathodic and anodic reactions, the cathodic the more at low concentrations, the anodic the more at high.
The results are interpreted by a modified adsorption theory and are discussed in terms of recent fundamental views of electrode reactions. Some practical implications are pointed out.
TL;DR: In the case of amorphous iron(III) hydroxide hydrate, the main variable governing the rates at which these compounds form is pH and other important factors are temperature and the presence of additives as mentioned in this paper.
Abstract: Hydrolysis of ferric solutions leads initially to mono- and dinuclear species which interact to produce further species of higher nuclearity. These polynuclear species age eventually to either crystalline compounds or to an amorphous precipitate (amorphous iron(III) hydroxide hydrate).
Amorphous iron(III) hydroxide hydrate is thermodynamically unstable and gradually transforms to α-FeO(OH) and α-Fe2O3. These crystalline products form by competing mechanisms and the proportion of each in the final product depends on the relative rates of formation. The master variable governing the rates at which these compounds form is pH. Other important factors are temperature and the presence of additives.
Most additives retard the transformation and by suppressing formation of α-FeO(OH) lead to an increase in the amount of α-Fe2O3 in the product; some additives also directly promote formation of the latter compound. Metal ions can oftxen replace a proportion of Fe in the α-FeO(OH) and α-Fe2O3 lattices. At high enough concentrations they can induce formation of additional phases. Additives may also modify the morphology of the crystalline products.
TL;DR: The corrosion of aluminium at room temperature has been investigated in nine decinormal solutions over the pH range 2.0-12.0 in this article, and it is suggested that when aluminium, carrying its air-formed film, is immersed in a solution in the presence of oxygen, the film breaks down and a small corrosion current commences to flow.
Abstract: The corrosion of aluminium at room temperature has been investigated in nine decinormal solutions over the pH range 2.0–12.0. Corrosion was dependent more on the nature of the anion than on the pH of the solution.
The solubilities of hydrated and anhydrous aluminium oxide were examined and it was concluded that, except in the presence of chloride ions, corrosion was associated with the initial rate of solution of the anhydrous oxide.
Potential and anodic polarisation measurements indicated that whereas the normal anodic reaction is the formation of anhydrous oxide, in the presence of chloride, bromide and iodide ions soluble aluminium salts are formed.
It is suggested that when aluminium, carrying its air-formed film, is immersed in a solution in the presence of oxygen, the film breaks down and a small corrosion current commences to flow. In the absence of chlorides, and similar ions, film repair can take place and the behaviour of the aluminium is controlled by the relative rates of film repair and film breakdown. In the presence of chlorides film repair does not occur and once corrosion has been initiated by film breakdown it proceeds apace. If initiation is suppressed, by saturating the solution with aluminium oxide, corrosion is inhibited.
TL;DR: The concept of biotechnology is concerned with the production of new wonder drugs, such as interferon as discussed by the authors, however, another side to the subject is large-scale biotechnology concerned with biological processes for making many of the everyday bulk production on which society depends.
Abstract: Biotechnological research has witnessed enormous progress, particularly in the last decade The popular concept of biotechnology is that it is concerned with the production of new wonder drugs, such as interferon However, another side to the subject is large-scale biotechnology concerned with the biological processes for making many of the everyday bulk production on which society depends An industrial view of biotechnology is given with examples such as ammonia production, penicillin, single-cell protein, methanol and polyhydroxybutyrate
TL;DR: In this article, the removal of cupric ions from aqueous solution by a biosorption column in which the Rhizopus arrhizus fungal biomass was immobilized in reticulated foam biomass support particles was studied.
Abstract: The removal of cupric ions .from aqueous solution by a biosorption column in which the Rhizopus arrhizus fungal biomass was immobilized in reticulated foam biomass support particles was studied. Solution pH was found to be crucial to copper uptake, with the optimum range being 6.7-7.0. The removal eficiency was usually higher at low influent copper concentration and long residence time. The presence of other cations and anions inhibited copper uptake in the ,following order: for the cations, Mn2'>>Zn2'>Cd2+ >Mg2'>Ca2'; .for the anions, EDTA>>SO:->> C1- . The biosorption process was Jully reversible and regenerated columns showed undiminished perjormance.