AbstractThe chitosan degradation in formic acid solution with the presence of hydrogen peroxide was investigated in this work. Temperature and reaction time had a significant effect on reducing the molecular weight of chitosan, and it is clear that it decreased the molecular weight faster at the first 15 minutes of reaction time. Therefore, the molar concentration of chitosan in the solution increased with temperature and reaction time. The reaction order was determined from the molar changes of chitosan on reaction time and found followed -0.1 reaction order to the molar concentration of chitosan. The Arrhenius equation was used to study the correspondence influence of reaction temperature on the degradation reaction rate constant. The results suggest that the values of degradation rate constant increased with higher reaction temperature. The value of activation energy was determined under the experimental operating conditions examined to be 99.8 kJ/mol. The FT-IR spectra demonstrated that there was no change in the chemical structure of chitosan before and after the degradation reaction.

This study shows that by-products obtained after cold-pressing oil production (flex oil cake, hemp oil cake, hull-less pumpkin oil cake) could be used as substrates for the sustainable and cost-effective production of lipase when cultivating Thermomyces lanuginosus under solid-state conditions (T = 45 °C, t = 9 days). Lipase showed optimum activity at T = 40 °C. The produced lipase extract was purified 17.03-folds with a recovery of 1% after gel chromatography. Three different batch experiments were performed in order to test the possibility of using the lipase in biodiesel production. Experiments were performed with a commercial, unpurified enzyme, and partially purified lipase with sunflower oil and methanol as substrates in a batch reactor at 40 °C. During the experiments, the operational stability of the enzyme was studied. The obtained results clearly showed that produced crude and purified lipase can be used for biodiesel production, but the process needs some additional optimization. As for operation stability, it was noticed that the commercial enzyme was deactivated after 30 h, while produced crude enzyme remained 8.25% of its activity after 368 h.

This study aimed to investigate the conversion of the pre-treated oil, which was originally extracted from grease trap waste (GTW), to biodiesel via a transesterification reaction. The pre-treated oil, which consists of approximately 80% free fatty acid ethyl esters (FAEEs) and 18% of glycerides, was obtained through the esterification of GTW reported in a previous study. Response Surface Methodology (RSM) based on Central Composite Design (CCD) was applied to determine the optimum conditions for the transesterification reaction through four process variables, these being: the molar ratio of ethanol to oil, reaction time, reaction temperature, and base catalyst loading. A set of 30 experiments were conducted in duplicate to study the interactive effects of the above parameters on the ester yield. A maximum ester yield of 96.7% was obtained at the optimum conditions, which were: 4:1 ethanol to oil molar ratio, 1 hr reaction time, 65 degrees C reaction temperature, and 1 wt% KOH loading per oil weight. In order to reduce the excess ethanol used, a modification was applied to the experimental design of the transesterification reaction, resulting in a 30% reduction in ethanol used, while the same ester yield could be obtained.

•Scale-up and economic analysis of grease trap waste derived biodiesel were studied.•Two production routes, esterification with and without co-solvent, were examined.•The lowest break-even price of biodiesel obtained was US$1337.5/t.•Environmental service providers are likely the potential biodiesel producers.

Grease trap waste (GTW) often has a very high content of free fatty acids (FFA) which requires a pre-treatment step before it can be converted to biodiesel via the transesterification reaction. In this study, the esterification reaction was performed to reduce the level of FFA in the GTW, utilizing ethanol as the reagent in the presence of the catalyst H2SO4. Response Surface Methodology (RSM) based on Central Composite Design (CCD) was applied to determine the optimal conditions for the esterification reaction through four process variables, these being: the molar ratio of ethanol to fats, oils, and grease (FOG), reaction time, reaction temperature, and catalyst loading. A set of 30 experiments were conducted in triplicate to study the interactive effects of the above variables on the reduction of the level of FFAs. An FFA% of 0.84% was obtained at the optimum conditions, which were 6:1 ethanol to FOG molar ratio, 3 hr reaction time, 75 degrees C reaction temperature, and 3 wt% H2SO4 loading per FOG weight.

Alternative resources such as biomass and waste as feedstocks for the production of bioproducts and subsequently to the production of fuels and chemicals have attracted worldwide attention due to their biodegradability and low environmental impacts. One popular research field has attempted to produce commercial biodiesel that can substitute petrodiesel in transportation, power generation, industrial production and household activities. However, the popularization of biodiesel is still limited due to the lower price of petrodiesel. Most of these studies have lead to a success at lab scale, but researchers are still striving to develop a feasible economic and commercial production plant. Significant effort has been put into investigation of optimal operating parameters for the production of biodiesel from grease trap waste (GTW) but further research needs to be conducted to clarify the effect of process scale-up on the quality and quantity of biodiesel products. It is especially necessary to determine the appropriate techniques and reactor type and to synthesize process flow sheets that can maximize the product quality and product yield at acceptable price. Biomaterials: biological production of fuels and chemicals, edited by Rafael Luque and Chun-Ping Xu, provides comprehensive, to date research developments in biomaterials science and engineering. Two major topics have been addressed – namely (i) techniques for the utilization of biomass and raw materials for the production of fuels and chemicals from the chemical engineering point of view, and (ii) current industrial applications of alternative processes such as the application and production of chitin and the fermentation of food waste as a hydrogen source. This book consists of eight chapters. Chapter 1 provides an overview with clear comparison for the production of bioproduct from a range of low cost and large scale unit operations to the high cost and smaller scale unit operations from the varieties of biomass feedstocks. Detailed summaries of upand downstream bioprocesses that specifically relate to the selection of various equipment in unit operations are given. The use of life cycle analyses is also introduced in this chapter. Chapters 2–7 review the biological routes including metabolic pathways and catalytic conversions for the production of biofuels and chemicals from a variety of biomass sources. The importance of nanoparticle materials produced from polysaccharides for drugs and food delivery are discussed in the last chapter (Chapter 8). In conclusion, the international team of authors of this book have successfully provided an excellent and detailed overview of the following three concepts: (i) state-of-the-art in biomass conversion into valuable fuels, (ii) the challenges as well as the significant industrial applications of renewable biomaterials, and (iii) the potential of recycled biomass and waste into green energy and essential chemicals. The book is very diverse in topics and comprises some cutting-edge topics which are likely not to be accessible in a similar compilation in other books. Thus, the book manages to keep its own profile. The book is very readable and, overall, the references for all chapters were well cited. The book would be better had the subheadings been consistent. For example, some chapters use conclusions whilst other chapters refer to it as future perspective, outlook and in one chapter there was no conclusion. In addition, readability would be improved with more images. It is helpful that the subtitle of the book Biological production of fuels and chemicals was included, as the main title Biomaterials is commonly

A textural and kinetic investigation of the carbonatation of anhydrite in the presence of carbonate- and bicarbonate bearing solutions under static conditions was conducted. The replacement occurs via a coupled dissolution precipitation mechanism. Textural and kinetic evidence indicates that the rate-limiting step in the replacement reaction was the dissolution of anhydrite and that the dissolution rate was likely controlled by the diffusion of ionic species in the aqueous phase. Calcium carbonate polymorphism was sensitive to temperature and solution composition. Bicarbonate-bearing solutions up to 80 degrees C only produced calcite, but aragonite formed alongside calcite in carbonate-bearing solutions, occurring in trace amounts at 25 degrees C and becoming the dominant polymorph at temperatures >= 60 degrees C. Furthermore, within the carbonate-bearing solutions (high pH) at elevated temperature, kinetic and textural evidence indicates that competition between calcite and aragonite nucleation and growth plays a greater role in defining the mineralogy and textures of the products than an aragonite to calcite ripening process such as the one previously reported for the carbonatation of gypsum. A lack of crystallographic relationship between the aragonite and calcite that formed at elevated temperatures, along with an apparent stabilization of the calcite/aragonite ratio at the early stages of the replacement, highlight the importance of the kinetics of precipitation (via nucleation and growth) and the role temperature and solution composition can play in stabilizing metastable product phases during mineral replacement reactions.

Symplectic microstructures are abundant in copper-iron-sulfide minerals and are conventionally considered to form by solid-state diffusion processes. Here we experimentally demonstrate that coarsening of exsolution lamellae occurs similar to 1000 times faster in the presence of a fluid compared to the equivalent dry system. Bornite-digenite solid solutions (Cu5FeS4-Cu8.52Fe0.11S4.88) were synthesized hydrothermally via the replacement of chalcopyrite, and we compared the microtextures in the product subjected to different cooling histories: (i) dry annealing after synthesis; (ii) cooling to an annealing temperature immediately following hydrothermal synthesis; and (iii) annealing in a hydrothermal fluid following quenching to room temperature and then reheating. We interpret the rapid coarsening of the exsolution lamellae in the presence of a fluid phase to result from recrystallization associated with healing of the open porous microstructure in the parent phase. The porosity is a consequence of the synthesis of the parent bornite-digenite solid solutions via interface coupled dissolution reprecipitation. The texture coarsening is accompanied by the destruction of the transient open porous microstructure via coalescence of the pores and their migration to lamellae and grain boundaries. As a result, the final microstructure and the kinetics of textural coarsening depend upon the crystallization and cooling history of the parent mineral. Such fluid-driven textural evolution may be a major mode of reaction in ore systems, and is likely to affect oxide and silicate systems alike in the presence of aqueous fluids.

We report on the formation of powder by drying oil-in-water emulsions stabilized by silanised silica nanoparticles. Drying was achieved by spraying fine droplets (up to a hundred micrometres in diameter) of the emulsions into a chamber of hot, flowing air. We show that the surfaces of droplets of the emulsions become enriched with nanoparticles as the water evaporates in the drying chamber. Controlling the relative amounts of oil and particles in the droplets being dried is the key to encapsulating the oil drops within the powder. Dried Pickering emulsions containing up to 40 wt% encapsulated oil that could be dispersed in water as drops of the same size as in the original emulsion were produced. (C) 2017 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

Geologic samples are extremely diverse and share a tendency for both heterogeneity and complexity. This is especially true for ores, which commonly result from a complex interplay of processes in highly dynamic environments. In recent years, a number of tools allowing the chemical mapping of major (e.g., mineral liberation analysis, MLA), minor (e.g., electron microprobe, EPMA), and trace (e.g., laser ablation-inductively coupled plasma-mass spectrometry, LA-ICP-MS) elements in geologic samples at similar to 1- to 50-mu m resolution and over mm(2) areas have seen rapid development and have become readily available. To date, the application of synchrotron-based X-ray fluorescence (SXRF) mapping has been limited to addressing key questions because of low availability and high cost. This paper demonstrates how recent advances in X-ray fluorescence detector technology are bringing new possibilities to ore petrology. Millisecond dwell times allow collection of thin section size maps at resolutions of a few urn in hours, while improvements in data analysis software simplify the production of quantitative elemental maps.Based on the imaging of six samples representative of different commodities (Pt, U, Cu, Ge) and different geologic contexts (PGE deposit; sandstone-hosted U deposit; vein-type polymetallic hydrothermal deposit; iron oxide-copper-gold (IOCG) deposit), we demonstrate that megapixel SXRF (MSXRF) can efficiently provide the information necessary to understand metal speciation in the context of thin section-scale textural complexity. Image analysis revealed a number of new results for the studied deposits, for example, (1) the distribution of micrometer-sized Pt-rich grains and Ti mobility during the formation of schistosity at the Fifield Point prospect (New South Wales, Australia); (2) the presence of Ge contained in organic matter and of Hg minerals associated within quartzite clasts in the Lake Frome U ores (South Australia); (3) confirmation of the two-stage Ge enrichment in the Barrigao deposit, with demonstration of the presence of Ge in solid solution in the early chalcopyrite (Portuguese Iberian pyrite belt); and (4) the enrichment of U during late dissolution-reprecipitation reactions in the hornite ores of the Moonta and Wallaroo IOCG deposits (South Australia). These results illustrate that MSXRF is a powerful technique for locating nano- to microparticles of precious metals (Pt) and trace contaminants (e.g., Hg) that form distinct (micro) minerals. In addition, it is a powerful tool for understanding commodities with relatively low ore grades and complex distribution (100-1,000 ppm; e.g., U, Ge).

Nam Nghiep Tran, Cuong Phuoc Tran, Phong Quoc Ho, Tony Hall, Edward J McMurchie, Volker Hessel, Yung Ngothai

Water activity is generally considered to affect ionic association in aqueous electrolyte solutions; however, it is usually ignored when the association reactions or constants are discussed. In this work, the effect of water activity on the association reaction \( {\text{Ni}}_{{ ( {\text{aq}})}}^{2 + } + n{\text{Cl}}_{{ ( {\text{aq)}}}}^{ - } \rightleftharpoons {\text{NiCl}}_{{n{\text{ (aq)}}}}^{2 - n} \) was investigated by EXAFS and UV–Vis spectroscopy measurements on NiCl2 aqueous solutions at room temperature with constant Cl−/Ni2+ ratio (~66) and various water activities; the latter were adjusted by adding MgCl2 and Mg(ClO4)2. Both the EXAFS and the UV–Vis spectra measurements indicated that the extent of Ni–Cl association increases in decreasing water activity environments, independent on the Cl−/Ni2+ ratio. Thus, the effect of water activity on the ionic association should not be ignored and more emphasis should be paid on it, especially, when the water activity is very low.

Knowledge of the structure and speciation of aqueous Ni(II)-chloride complexes is important for understanding Ni behavior in hydrometallurgical extraction. The effect of concentration on the first-shell structure of Ni(II) in aqueous NiCl2 and NiCl2-MgCl2 solutions was investigated by Ni K edge X-ray absorption (XAS) and UV-Vis spectroscopy at ambient conditions. Both techniques show that no large structural change (e.g., transition from octahedral to tetrahedral-like configuration) occurs. Both methods confirm that the Ni(II) aqua ion (with six coordinated water molecules at RNi-O = 2.07(2) Å) is the dominant species over the whole NiCl2 concentration range. However, XANES, EXAFS and UV-Vis data show subtle changes at high salinity (> 2 mol∙kg-1 NiCl2), which are consistent with the formation of small amounts of the NiCl+ complex (up to 0.44(23) Cl at a Ni-Cl distance of 2.35(2) Å in 5.05 mol∙kg-1 NiCl2) in the pure NiCl2 solutions. At high Cl:Ni ratio in the NiCl2-MgCl2-H2O solutions, small amounts of [NiCl2]0 are also present. We developed a speciation-based mixed-solvent electrolyte (MSE) model to describe activity-composition relationships in NiCl2-MgCl2-H2O solutions, and at the same time predict Ni(II) speciation that is consistent with our XAS and UV-Vis data and with existing literature data up to the solubility limit, resolving a long-standing uncertainty about the role of chloride complexing in this system.

Texture encompasses 'the overall appearance a rock has because of the size, shape, and arrangement of its constituent mineral grains'. Textural observations are crucial for deciphering the origin and geological history of rocks and their constituting minerals. In metamorphic and hydrothermal settings, textural observations hence serve to reconstruct the P,T path and the compositions and origins of the parent fluids. Over the past 13 years, a number of studies have emphasized the role of 'coupled dissolution reprecipitation reactions' (CDR) in geological systems. In these fluid-driven reactions, the replacement of one phase by another occurs via coupling between the dissolution of the parent and the precipitation of the product. In this paper we review the diversity of textures that arise from the CDR mechanism. The great diversity of textures relates to the diversity of mechanisms responsible for the coupling between dissolution and precipitation. Key parameters defining textures include volume change, the rate-limiting process, and the local composition at the mineral-fluid interface. In many of the reviewed examples, reaction mechanisms, rather than intensive properties such as P-T history, control the textures in the products, and far-from-equilibrium or local equilibriums at the mineral-fluid interface play a key role in controlling the final textures and mineral assemblages. These processes can also lead to the scavenging of trace elements from hydrothermal fluids. Because by nature CDR reactions are interface-controlled, many of the products are metastable, which further drives the reactions. These subsequent reactions can add to the textural complexity, or on the contrary obscure the original reaction mechanism.This review emphasizes the need to improve our understanding of reaction mechanisms, especially in systems containing even minor amounts of fluids (ore systems; metasomatic and metamorphic systems). Such a process-driven understanding is vital to supporting the petrological interpretation of textures. (C) 2015 Elsevier B.V. All rights reserved.

Interface coupled dissolution-reprecipitation reactions (ICDR) are a common feature of fluid-rock interaction during crustal fluid flow. We tested the hypothesis that ICDR reactions can play a key role in scavenging minor elements by exploring the fate of U during the experimental sulfidation of hematite to chalcopyrite under hydrothermal conditions (220-300 degrees C). The experiments where U was added, either as solid UO2+X(s) or as a soluble uranyl complex, differed from the U-free experiments in that pyrite precipitated initially, before the onset of chalcopyrite precipitation. In addition, in UO2+X(s)-bearing experiments, enhanced hematite dissolution led to increased porosity and precipitation of pyrite+magnetite within the hematite core, whereas in uranyl nitrate-bearing experiments, abundant pyrite formed initially, before being replaced by chalcopyrite. Uranium scavenging was mainly associated with the early reaction stage (pyrite precipitation), resulting in a thin U-rich line marking the original hematite grain surface. This "line" consists of nanocrystals of UO2+X(s), based on chemical mapping and XANES spectroscopy. This study shows that the presence of minor components can affect the pathway of ICDR reactions. Reactions between U- and Cu-bearing fluids and hematite can explain the Cu-U association prominent in some iron oxide-copper-gold (IOCG) deposits.

Abstract We report the replacement of chalcopyrite by bornite under hydrothermal conditions in solutions containing Cu(I) and hydrosulfide over the temperature range 200-320 °C at autogenous pressures. Chalcopyrite was replaced by bornite under all studied conditions. The reaction proceeds via an interface coupled dissolution-reprecipitation (ICDR) mechanism and via additional overgrowth of bornite from the bulk solution. Initially, the reaction is fast and results in a bornite rim of homogeneous thickness. Reaction rates then slow down, probably reflecting healing of the porosity, and the reaction proceeds predominantly along twin boundaries of the chalcopyrite. The composition of the bornite product is generally Cu-rich, corresponding to the bornite-digenite (Cu5FeS4-Cu9S5; Bn-Dg) solid solution (bdss). The Cu and Fe contents were controlled principally by temperature, with solution pH having only a small effect. The percentage of Cu in bdss decreased and the percentage of Fe increased with increasing reaction temperature: at 200 °C a composition of Bn47Dg53 was obtained; at 300 °C the composition was Bn90Dg10 and at 320 °C it was near-stoichiometric bornite. The influence of temperature rather than solution chemistry on the composition of bdss, as well as the homogeneity of the bornite product grown both via replacement of chalcopyrite and from the bulk solution as overgrowth, are interpreted to reflect buffering of the bornite activity in bdss via solids (e.g., reaction chalcopyrite + 2 chalcocite = bornite). Only the end-member compositions of the bdss are found in nature, indicating that the products obtained are metastable, and illustrating the importance of reaction mechanism for controlling the chemistry of the mineral product. The unique features of the chalcopyrite to bornite reaction investigated here are related to interaction between a solution controlled ICDR reaction with solid-state diffusion processes driving porosity healing.

Chalcopyrite (CuFeS2) and bornite (Cu5FeS4) are the most abundant Cu-bearing minerals in hydrothermal Cu deposits, forming under a wide range of conditions from moderate-temperature sedimentary exhalative deposits to high-temperature porphyry Cu and skarn deposits. We report the hydrothermal synthesis of both chalcopyrite and bornite at 200-300 degrees C under hydrothermal conditions. Both minerals formed via the sulfidation of hematite in solutions containing Cu(I) (as a chloride complex) and hydrosulfide, at pH near the pK(a) of H2S(aq) over the whole temperature range. Polycrystalline chalcopyrite formed first, followed by bornite.Assuming that Fe behaves conservatively, the transformation of hematite to chalcopyrite involves a large increase in volume (similar to 290%). The reaction proceeds both via direct replacement of the existing hematite and via overgrowth around the grain. Chemical exchanges between bulk solution and hematite are enabled by a network of micrometer-size pores. However, in some cases the chalcopyrite overgrowth develops large grain sizes with few apparent pores and in these cases fluid transport may have been via a network of fractures. Similarly to the replacement of hematite by chalcopyrite, bornite forms via the replacement of chalcopyrite. The reaction has a large positive volume (similar to 230%), and proceeds both via chalcopyrite replacement and via overgrowth.This study shows that replacement reactions can proceed via coupled dissolution-reprecipitation even where there is a large volume increase between parent and product mineral. This study also provides further evidence about the controls of reaction pathways onto the final mineral assemblage. In this case, the host initial fluid was undersaturated with respect to Fe-bearing minerals. Upon slow release of Fe at the surface of hematite, a mineral assemblage of chalcocite, bornite, and finally chalcopyrite is expected. However, in practice chalcocite did not nucleate on the surface of hematite. Rather relatively slow nucleation of bornite enabled high concentrations of Fe to build up near the dissolving hematite, so that chalcopyrite (high-sulfidation experiments) or chalcopyrite+pyrite (low sulfidation) crystallized first.