Preparation of Cellulose Nanocrystals Using an Ionic Liquid

In this paper cellulose nanocrystals were prepared by treating microcrystalline cellulose with 1-butyl-3-methylimidazolium hydrogen sulphate ionic liquid. Cellulose nanocrystals, after separation from ionic liquid, were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), Field emission scanning electron microscopy (FESEM) Transmission Electron Microscope (TEM) and Thermogravimetric analysis. XRD results showed no changes in type of cellulose after the treatment with ionic liquid, however, high crystallinity index was observed in the ionic liquid treated sample. Cellulose nanocrystals, having length around 50–300 nm and diameter around 14–22 nm were observed in the ionic liquid treated sample under FESEM and TEM, and similar patterns of peaks as that of microcrystalline cellulose were observed for cellulose nanocrystals in the FTIR spectra. The thermal stability of the cellulose nanocrystals was measured low as compare to microcrystalline cellulose.     

A Novel Affinity Chromatographic Material for the Purification of Extracellular Polyhydroxybutyrate Depolymerases

A novel affinity chromatographic material, which is composed of silica matrix, coated with polyhydroxybutyrate (PHB) powder, suitable for the purification of PHB depolymerases, was developed. The surface morphology of the PHB-silica coated particles (silica-PHB composite particles) was examined by scanning electron microscopy and revealed a successful uniform coating of silica particles with PHB. Moreover, the complex of these materials retained its homogeneity even after incubation at 80 °C for 6 h, whereas the strong binding of PHB on silica surface was further verified by thermal gravimetric analysis and by PHB extraction- from silica surface- experiments. This novel material was demonstrated to be suitable for both, the one-step on-batch and on-column purification of Thermus thermophilus extracellular PHB depolymerase. The enzyme exhibited higher affinity against the composite of silica-PHB particles than PHB powder, since the one-step purification-fold and the overall recovery of the enzyme were 2.8 and 4 times higher respectively, in the first case. Reusability of the silica-PHB composites particles was examined by determining the recoveries of PHB depolymerase. The enzyme recoveries were ranged from 30 to 35% for the first five uses, whereas for further uses recoveries gradually dropped to 15–18% indicating that the particles could be used repeatedly for five times. This material could be also a suitable support for lipases or other proteins that exhibit strong affinity to hydrophobic materials.     

Decomposition of mixed plastics consisting of polypropylene and polyethylene terephthalate into oils over titania/silica catalysts

The catalytic decomposition of mixed plastics consisting of polypropylene (PP) and polyethylene terephthalate (PET) has been investigated over titania/silica catalysts at 698 K. The yield of oil produced was about 70%, and the large amounts of C₁₈₊ hydrocarbons this contained was from the aromatics in PET. Gas was also produced, including C₃–C₅ hydrocarbons. The carbon-number fractions in the oil was influenced by the PET/(PP + PET) ratios and the catalyst weight. The titania/silica catalysts could be used repeatedly, and after they had been fouled, could be regenerated. From the Fourier Transform Infrared (FT–IR) spectroscopic data of adsorbed pyridine on the catalyst surface, most of the acid sites of the titania/silica catalysts were found to be Lewis sites where the hydride abstracted from PP pyrolysates react with PET pyrolysates to form oil and gas. Received: July 19, 2000 / Accepted: October 20, 2000     

硅胶固载季鏻离子液体对CO_2的吸附

采用嫁接法制备了硅胶固载季鏻双三氟甲烷磺酰亚胺盐离子液体,并将其用于对CO2的吸附,考察了吸附剂的吸附等温线及循环使用性,并运用均相表面扩散模型(HSDM)研究了吸附动力学。采用FTIR和TG等技术对试样进行了表征。表征结果显示:离子液体已成功固载到硅胶上;煅烧活化硅胶对季鏻离子液体(C-Si O2-P4T)的固载量为5.39%(w);固载试样基本保持了硅胶的孔道特征。实验结果表明:C-Si O2-P4T具有较高的CO2平衡吸附量,且能显著提高CO2/N2吸附选择性,循环使用6次仍保持良好的吸附能力;HSDM可较好地拟合CO2在C-Si O2-P4T内的扩散行为,40℃下的扩散系数在10-7 m2/s数量级,与硅胶同级,优于纯季鏻离子液体。     

Environmentally Friendly Methodology for Preparation of Amino Acid Containing Polyamides

A short and green method for the preparation of optically active aromatic polyamides (PAs) using tetrabutylammonium bromide (TBAB) as a molten ionic liquid is reported. Polycondensation reactions of amino acid containing diacid (2S)-5-(4-methyl-2-phthalimidylpentanoylamino)isophthalic acid with various commercially available diisocyanates in molten TBAB as a green medium or in N-methylpyrrolidone as common organic solvent with or without dibutyltin dilaurate as a catalyst under microwave irradiation were carried out. Various PAs were obtained with high yields and moderate inherent viscosities in the rang of 0.30–0.57 dL/g. The obtained polymers were characterized by FT-IR, specific rotation measurements, and representative of them by ¹H NMR and elemental analysis techniques. Thermal properties of PAs were evaluated by thermogravimetric analysis and the results showed that the 10% weight loss temperature in a nitrogen atmosphere for four representative samples were more than 258 °C, which indicates that the resulting PAs have good thermal stability as well as excellent solubility.     

硅胶复合材料吸附重金属汞的研究进展

针对高毒性、易累积的重金属汞污染物,介绍了对硅胶基底材料进行化学改性的方法,从液相和气相两方面详述了硅胶复合材料(包括有机官能团改性硅胶材料和无机磁性硅胶复合材料)在汞吸附分离领域的研究和应用进展,分析了现有研究的不足之处,并对该领域未来的研究方向提出了建议。指出,研制出高效、高选择性、高稳定性、易回收的汞吸附剂是治理工业废水和燃煤烟气中汞污染的关键。     

Elemental Mercury Control by Novel Oxidant and Sorbent in an Entrained-Flow System

An entrained-flow system has been designed and constructed to simulate in-flight mercury capture by sorbents in ducts of coal-fired utility plants. The test conditions of 1.5 s residence time, 140°C temperature, 4.5 ppbv inlet Hg⁰ concentration, and 0–20 lb/MMacf sorbent injection rates were chosen to simulate conditions in the ducts. Novel oxidants developed in previous fixed-bed tests and novel sorbents derived from the novel oxidants were tested for their Hg⁰ capture in the entrained-flow system to examine the possibility of using those sorbents in a full-scale system. Darco-FGD and Darco Hg-LH served as benchmark sorbents with which mercury control capability of the novel oxidants and novel sorbents could be compared. The test results showed that the novel oxidants have remarkable Hg⁰ oxidation capability, and the novel sorbents showed a better performance in Hg⁰ removal than Darco Hg-LH.     

Photo-Stabilisation and UV Blocking Efficacy of Coated Macro and Nano-Rutile Titanium Dioxide Particles in Paints and Coatings

Surface treated macro and nanoparticle TiO₂ samples have been prepared, characterised and their efficiency as UV blockers evaluated in clear coatings and paints. The particle size of the ‘base’ TiO₂ has been optimised to block UV radiation and the surface treatment developed to deactivate the photocatalytic activity of the surface of the TiO₂ particles. The resultant UV blockers have been evaluated in both solvent and water-based clear coatings. Nanoparticle TiO₂ has been prepared from ‘seed’ and the particle size was controlled by calcination. It was found that the choice of particle size is a compromise between UVA absorption, UVB absorption, visible transmission and photoactivity. It has been demonstrated that TiO₂ with a crystallite size of 25 nm yields a product with the optimum properties. A range of dispersants was successfully used to disperse and mill the TiO₂. Both organic and inorganic dispersants were used; 2-amino-2-methyl-1-propanol and 1-amino-2-propanol (MIPA) and P₂O₅ and Na₂SiO₃ respectively. The surface of the nano-TiO₂ was coated with mixed oxides of silicon, aluminium, zirconium and phosphorous. Addition of the resultant coated nano-rutiles to an Isocyanate Acrylic clear coating prolonged the lifetime of that coating compared to the blank. Generally, a surface treatment based on SiO₂, Al₂O₃ and P₂O₅ was more successful than one based on ZrO₂, Al₂O₃ and P₂O₅. Higher addition levels of the surface treatment were beneficial for protecting the polymeric coating. The UV blocker products were also evaluated in a water-based acrylic, first a water-based dispersion of the UV blocker was prepared before addition to the acrylic. The dispersions and resultant acrylic thin films were evaluated using UV/Vis spectroscopy and durability assessed. The ratio of absorbance at 300:500 nm for the water-based dispersion was shown to be a good predictor of both the transparency of the resultant acrylic thin film and the durability of that film, in terms of weight loss. Macro grade titanium dioxide pigments were also prepared and coated with treatments of silica, alumina and siloxane and their photo-stabilising activity in alkyd paint film assessed and found to be directly related to the electron–hole pair mobility and trapping as determined by micro-wave spectroscopy.     

PM<Subscript>10</Subscript> and Ultrafine Particles Counts In-Vehicle and On-Road in the Athens Area

This work presents the first results of a study concerning on-road and in-vehicle exposure to particulate matter in the area of Athens. PM₁₀ concentration measurements were conducted by TSI DustTrak, while driving along routes with different characteristics of traffic density, during September 2003–March 2004. Concurrent measurements of the ultrafine particles (UFPs) number concentration were also conducted, by condensation particle counter during part of the days. Pedestrian exposure to PM₁₀ and UFPs was also studied through stationary measurements on the kerbside of selected roads on November 2003 and February 2004. A major avenue, a heavy-trafficked road across a children hospital and two central roads, one in a residential and one in a commercial area were selected for measurement. The results indicate that every day commuters are exposed to significant concentration levels. Higher exposures were observed in heavy-trafficked areas and during rush hours. Mean PM₁₀ in-vehicle and on-road concentrations ranged from 30–320 μg/m³ and 70–285 μg/m³, respectively. The ultrafine particles number concentrations were in the range of 5.0 × 10⁴–17.3 × 10⁴ particles/cm³ in-vehicle and 3.1 × 10⁴–7.3 × 10⁴ particles/cm³ on the kerbside of a central residential road. Both PM₁₀ and UFPs concentrations presented repeated short-term peak exposures. The results clearly point out the importance of the road microenvironment (in-vehicle and on kerbside) for population exposure in urban areas.     

Release Characteristics of Nutrients from Polymer-coated Compound Controlled Release Fertilizers

Reliable information regarding release characteristics of nutrients from a polymer-coated controlled release fertilizer (CRF) is essential for beneficial agronomic and environmental results. Significant knowledge regarding nitrogen release from polymer-coated urea was gained while the information regarding the release of the different nutrients contained in polymer-coated compound N–P–K CRF remains limited. An experiment in which major factors affecting the differential release of nutrients from two coated compound CRF was performed in free water, water saturated sand and sand at field capacity. In general, nitrate release was the fastest, followed by ammonium and potassium whereas phosphate was significantly slower, with a rate of linear release in free water 45–70% slower than that of nitrate. Little differences were obtained for the lag periods of nitrate, ammonium and potassium release (2–10 days) under the experimental conditions, whereas for P they were one order of magnitude larger. The main factor slowing the release was assumed to be the lower solubility of ions with P being the least soluble. Release into free water was, expectedly, somewhat faster than that into saturated sand and significantly faster as compared to sand at field capacity and particularly so for P. Raising the temperature from 20 °C to 40 °C increased the rate of linear release of the different nutrients. The energy of activation, EA_rel, estimated for the linear release, of the different nutrients, was narrow ranging between 37 to 46 (KJ mol⁻¹) whereas the mean values obtained for the two CRF, differing by 50% in coating thickness, was non-significant. However, EA_rel was significantly different in different media. The complex effect of temperature on the lag period and nutrient interactions during release deserve further investigation.     

Sulphate and Nitrate in Precipitation and Soil Water in Pine Forests in Latvia

The SO₄–S and NO₃–N concentrations and pH in bulk precipitation, throughfall, stemflow and soil water for the 1994–2004 period were studied in pine forests in Latvia (Rucava and Taurene Integrated Monitoring stations). The SO₄–S and NO₃–N concentrations decreased over the study period, simultaneously with a decrease of acidity in precipitation. The changes were more evident in the western part of Latvia, probably due to declining long-range air pollution from West Europe. The trend of decreasing sulphate concentrations and increasing pH in precipitation were not followed by respective changes in soil water. In the upper soil horizon sulphate ion concentrations and acidity increased in soil water. Over the observation period, nitrate concentrations also showed an increasing trend in soil water at Rucava and Taurene, but these changes were not statistically significant.     

Assessing Aerobic Biodegradability of Plastics in Aqueous Environment by GC-Analyzing Composition of Equilibrium Gaseous Phase

Testing biodegradability of plastics under varied conditions of the environment as well as under laboratory conditions in accordance with valid international standards is very laborious, lengthy and often also economically demanding. For this reason, applicability was verified of gas chromatography to analyze gaseous phase when investigating the biodegradation course of plastics in an aqueous environment as an alternative to customary employed methods. A mathematical model of acid–basic CO₂ equilibrium in a gas–liquid system was worked out, enabling to determine quantity of produced CO₂ through chromatographic analysis of gaseous phase, in dependence on ratio of liquid and gas phase volumes (V _l/V _g) and on actual pH of liquid phase. Experimental conditions for organizing the tests were optimized. A ratio that proved suitable was V _l/V _g ≅ 0.1 at pH ≈ 7.1 of liquid phase. Under these test conditions, biodegradability of model samples, PHB, Gellan gum and Xanthan gum, was explored; course of biodegradation was studied through produced CO₂ (values ) determined by analyzing gaseous phase through gas chromatography on the one hand, and through customary “titration” procedure on the other. With water-soluble polymers, the decrement in dissolved organic carbon (values D _DOC) was also studied. Difference between values does not exceed 5%. The procedures in question are alternative “substituting” procedures for observing course of aerobic biodegradation of substances in an aqueous environment.     

Synthesis of mesoporous silica materials from municipal solid waste incinerator bottom ash

Incinerator bottom ash contains a large amount of silica and can hence be used as a silica source for the synthesis of mesoporous silica materials. In this study, the conditions for alkaline fusion to extract silica from incinerator bottom ash were investigated, and the resulting supernatant solution was used as the silica source for synthesizing mesoporous silica materials. The physical and chemical characteristics of the mesoporous silica materials were analyzed using BET, XRD, FTIR, SEM, and solid-state NMR. The results indicated that the BET surface area and pore size distribution of the synthesized silica materials were 992 m²/g and 2–3.8 nm, respectively. The XRD patterns showed that the synthesized materials exhibited a hexagonal pore structure with a smaller order. The NMR spectra of the synthesized materials exhibited three peaks, corresponding to Q² [Si(OSi)₂(OH)₂], Q³ [Si(OSi)₃(OH)], and Q⁴ [Si(OSi)₄]. The FTIR spectra confirmed the existence of a surface hydroxyl group and the occurrence of symmetric Si–O stretching. Thus, mesoporous silica was successfully synthesized from incinerator bottom ash. Finally, the effectiveness of the synthesized silica in removing heavy metals (Pb²⁺, Cu²⁺, Cd²⁺, and Cr²⁺) from aqueous solutions was also determined. The results showed that the silica materials synthesized from incinerator bottom ash have potential for use as an adsorbent for the removal of heavy metals from aqueous solutions.     

Gaseous mercury oxidation behavior in homogeneous reaction with chlorine compounds

Homogeneous oxidation reactions of gaseous elemental mercury were experimentally tested to study the behavior of mercury compounds that contribute to toxic emissions in combustion flue gas. Chemical equilibrium calculations and reaction kinetics analysis were also carried out to help explain the experimental results. In particular, the chemical forms of oxidized mercury and their reaction paths were verified in detail. Among the experimental results, molecular chlorine was confirmed to have a higher oxidizing ability toward elemental mercury than hydrogen chloride does. From the chemical equilibrium calculation, the final product of mercury compounds oxidized by chlorine was confirmed to be mercury chloride (HgCl₂). Numerical analyses of reaction kinetics were mostly consistent with the experimental results and the chemical equilibrium calculations. The ratio of mercury oxidization by chlorine increases with temperature from 473 K to 873 K, although it decreases at temperatures higher than 1000 K. Sensitivity analysis revealed the dominant reaction path of the mercury oxidation by chlorine. First, elemental mercury reacts with Cl radicals to form HgCl. Then, the HgCl reacts with Cl₂ to produce HgCl₂.     

Exposure Programme on Atmospheric Corrosion Effects of Acidifying Pollutants in Tropical and Subtropical Climates

Many national exposure programmes have been performed in tropical and subtropical climates during the last 50 years. However, ambitious programmes involving more than a few countries are scarce. In this paper a recently formed network of test sites is described involving 12 test sites in Asia (India, Vietnam, Thailand, Malaysia and China including Hong Kong) and four test sites in Africa (South Africa, Zambia and Zimbabwe). This effort is part of the 2001–2004 Swedish International Development Agency (SIDA) funded Programme on Regional Air Pollution in Developing Countries (RAPIDC). Corrosion attack after one (2002–2003) year of exposure (carbon steel, zinc, copper, limestone and paint coated steel) are presented together with environmental data (SO₂, NO₂, HNO₃, O₃, particles, amount and pH of precipitation, temperature and relative humidity) for all the test sites. The obtained corrosion values are substantially higher than expected for limestone, higher than expected for carbon steel and lower than expected for zinc compared to values calculated using the best available dose–response functions.     

Resurrection of the iron and phosphorus resource in steel-making slag

 This research focused on the treatment of steel-making slags to recycle and recover iron and phosphorus. The carbothermal reduction behavior of both synthesized and factory steel-making slag in microwave irradiation was investigated. The slags were mixed with graphite powder and heated to a temperature higher than 1873 K to precipitate a lump of Fe–C alloy with a diameter of 2–8 mm. The larger the carbon equivalent (C_eq, defined in the text), the higher the fractional reduction of iron and phosphorus. An increase in the SiO₂ content of slag led to a considerable improvement in the reduction for both iron and phosphorus because of the improvement in the fluidity of the slags and an increase in the activity coefficient of P₂O₅ in the slags. The extraction behavior of phosphorus from Fe–P–C_satd alloy was also investigated at 1473 K by carbonate flux treatment. For all the experiments with a processing time longer than 10 min, the phosphorus in the fluxes could be concentrated to more than 9% (w/w) showing that it could be used as a phosphorus resource. Compared with K₂CO₃ flux treatment, that using Na₂CO₃ was more effective for the extraction of phosphorus, and this was attributed to the lower evaporation of Na₂CO₃. Finally, a recycling scheme for steel-making slag is proposed. Received: March 16, 2001 / Accepted: November 12, 2001     

Effects of Nitrogen Deposition on Bryophyte Species Composition of Calcareous Grasslands

Regular additions of NH₄NO₃ (35–140 kg N ha⁻¹ yr⁻¹) and (NH₄)₂SO₄ (140 kg N ha⁻¹ yr⁻¹) to a calcareous grassland in northern England over a period of 12 years have resulted in a decline in the frequency of the indigenous bryophyte species and the establishment of non-indigenous calcifuge species, with implications for the structure and composition of this calcareous bryophyte community. The lowest NH₄NO₃ additions of 35 kg N ha⁻¹ yr⁻¹ produced significant declines in frequency of Hypnum cupressiforme, Campylium chrysophyllum, and Calliergon cuspidatum. Significant reductions in frequency at higher NH₄NO₃ application rates were recorded for Pseudoscleropodium purum, Ctenidum molluscum, and Dicranum scoparium. The highest NH₄NO₃ and (NH₄)₂SO₄ additions provided conditions conducive for the establishment of two typical calcifuges – Polytrichum spp. and Campylopus introflexus, respectively. Substrate-surface pH measurements showed a dose-related reduction in pH with increasing NH₄NO₃ deposition rates of 1.6 pH units between the control and highest deposition rate, and a further significant fall in pH, of >1 pH unit, between the NH₄NO₃ and (NH₄)₂SO₄ treatments. These results suggest that indigenous bryophyte composition may be at risk from nitrogen deposition rates of 35 kg N ha⁻¹ yr⁻¹ or less. These effects are of particular concern for rare or endangered species of low frequency.     

Determination of nitrous oxide, methane, and ammonia emissions from a swine waste composting process

The amounts of harmful gas emissions from the process of composting swine waste were determined using an experimental composting apparatus. Forced aeration (19.2–96.1 l/m³/min) was carried out continuously, and exhaust gases were collected and analyzed periodically. With weekly turning and the addition of a bulking agent in order to decrease the moisture content and increase air permeability, the temperature of most of the contents rose to 70°C and composting was complete within 3–5 weeks. NH₃, CH₄, and N₂O emissions were high in the early stage of composting. About 10%–25% of the nitrogen in the raw material was lost as NH₃ gas during composting. The emission rate of NH₃ mainly depended on the aeration rate, so that as the aeration rate rose, the level of NH₃ emissions increased. The CH₄ and N₂O emissions could be kept lower with adequate treatment at more than 40 l/m³/min aeration. N₂O may be mainly the result of the denitrification of NO _x -N in the additional matured compost used as a composting accelerator. Received: September 11, 1998 / Accepted: November 8, 1999     

Simple removal of dioxins by injecting combustion gas into water

A simple, low-cost method for suppression of dioxins/furans (hereinafter referred to as dioxins) is required because many middle- and, especially, small-scale incinerators have fallen into disuse or have been dismantled because of the high running and system costs of measures for the suppression of dioxins. Therefore, the purpose of the present study was to develop a simple removal method for dioxins from combustion gas and to evaluate the basic removal rate of dioxins. The removal method for suspended matter in a gas mixture (cold model) and dioxins in exhaust gases (hot model) has been investigated by means of gas injection into water, the mechanism of which is that the suspended matter in the gas gathers at the gas–liquid interface. In the cold model, the removal ratio of fine particles (R_P) by gas injection into water was reproduced well by the following equation: R_P (%) = 100 × {1−exp(−0.8 · S_S · t_C)}, where S_S (cm²/cm³) is the specific surface area of bubbles and t_C (s) is the residence time of bubbles in water. The removal ratio of fine particles increased as the product S_s · t_C increased. In a hot model using the exhaust gas from combustion experiments of polyvinyl chloride, the removal ratio of dioxins (R_D) by injecting the exhaust gas into water was estimated by the following equation: R_D (%) = 100 × {1−exp(−0.8 · S_S · t_C · C_D0 ^0.07)}, where C_D0 [ng/cm³ (at standard temperature and pressure)] is the dioxins concentration in the exhaust gas before injection into water. R_D depends greatly on the specific surface area of bubbles and the residence time of the bubbles in water, and only weakly on the dioxins concentration in the exhaust gas. Injection of the exhaust gas into water has been shown to be effective and was evaluated as a simple method for the removal of dioxins from exhaust gas.     

Organic–Inorganic Hybrid Coatings for the Modification of Barrier Properties of Poly(lactic acid) Films for Food Packaging Applications

Organic–inorganic hybrid coatings based on poly(ε-caprolactone), poly(ethylene oxide) or poly(lactic acid) as organic phase and silica from tetraethoxysilane as inorganic phase were prepared by the sol–gel approach. Coatings were applied onto poly(lactic acid) films for food packaging in order to improve its barrier properties towards oxygen and water vapour. All the prepared coatings were dense, homogeneous layers characterized by a good adhesion to the substrate. The permeance of the coating layers resulted one order of magnitude lower than that of the uncoated poly(lactic acid) (PLA) film. The hydrophilic character of the coating did not permit to gain a significant decrease in the water vapour permeance. The perfect visual transparency of the coatings allows their application without worsening of the esthetical properties of the substrate PLA film.