Physical characteristics of sintered fly ash aggregate containing clay binders

A comprehensive research has been conducted to explore the influence of sintering on the properties of fly ash aggregate containing clay binders (bentonite and kaolinite). Fly ash aggregate containing clay binders, have been subjected to various sintering temperatures at different durations of 700?C1400?°C and 15?C120?min, respectively. The variation in aggregate properties, viz strength, water absorption, density and shrinkage during sintering, have been determined and discussed. In addition to these, the uniformity of sintering and rate of water absorption of sintered aggregate were also determined. No significant changes in aggregate properties were observed for aggregate sintered up to 900?°C, due to the insufficient sintering temperature range. However, the aggregate properties substantially enhanced for temperature above 1000?°C, which is attributed to the activation of liquid phase sintering. For temperatures between 1000 and 1300?°C, the aggregate with bentonite shows significant increase in shrinkage (30?%), density (density ratio 0.70), higher ten percent fines value (TPFV) (6.13?tonne), reduction in porosity (35?%), and water absorption of 4?%. However, at 1400?°C, the aggregate properties degraded due to the decomposition of mineral phases in bentonite. For aggregates with kaolinite, highest TPFV of 8.5?tonne with lowest water absorption of 2?% have been observed at 1400?°C. The presence of a higher amount of interconnected pores for aggregates sintered between 700 and 1000?°C leads to a higher rate of water absorption and then reduces to 30?% for temperatures between 1200 and 1300 and 1200 to 1400?°C for bentonite and kaolinite aggregates, respectively. This reduction is due to the reduced interconnected pores. Duration of sintering has no impact on the aggregate properties for temperatures up to 800 and 1000?°C for aggregates with bentonite and kaolinite, respectively. However, between 1000 and 1400?°C, there has been considerable improvement in the aggregate properties for increasing duration up to 60?min. In comparison, during sintering, aggregates with bentonite possessed better properties for temperature less than 1000?°C, whereas aggregates with kaolinite exhibited superior properties between 1100 and 1400?°C.     

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.     

Evaluation on the property of sewage sludge cake by thermal treatment

The sewage sludge cake (SSC) used in this study was provided by a K-wastewater treatment plant in Kyonggi-Do, Korea. The characteristics of the SSC, such as particle size, water content, and composition were analyzed. Both the Korea extraction test (KET) and the toxicity characteristic leaching procedure (TCLP) were used to estimate whether the SSC was hazardous. In thermal experiments, the temperature was varied in the range 400° to 900°C and the heating time was varied from 1 to 6 h. The effects of thermal treatment temperature and time were evaluated by turbidity tests on the resultant SSC. On a dry basis, SSC mainly consisted of combustible content (60.2%) and phosphorous (25.9%). The turbidity of SSC was initially estimated in terms of the sedimentation time. The turbidity of SSC decreased exponentially from 9873 FAU at 0 h to 986 FAU at 6 h, so that the sedimentation time of SSC was established as 6 h. From the results of the thermal treatment at 600°C, thermal time can be determined by 2h because the turbidity of SSC is decreased dramatically within 1h and is stabilized after 2h. The turbidity of SSC decreased when the thermal treatment temperature increased from 400° to 900°C. The turbidity after thermal treatment at 400°C for 2 h was 29 FAU and this became almost 10 FAU at 600°C. The SSC was not hazardous, because KET and TCLP analysis produced values that were smaller than the regulatory levels. Hence, it was concluded that SSC can be stabilized by thermal treatment and can be used as a recycled material.     

Dechlorination of polyvinyl chloride in NaOH/ethylene glycol solution by microwave heating

This study investigated the dehydrochlorination of flexible polyvinyl chloride (PVC) containing 59.2% PVC, 29.7% dioctyl phthalate (DOP), and approximately 12% stabilizers. Flexible PVC was treated with NaOH/ethylene glycol (NaOH/EG) solutions at NaOH concentrations in the range 0.5–4 mol/l and was heated in a microwave heater at a temperature between 100° and 160°C for 0–30 min. All chlorides were completely eliminated by internal heating at 160°C using microwaves for 10 min in a 1 mol/l NaOH/EG solution, and the residue was made up of hydrocarbons. The weight loss rate reached a maximum of 74.7% at a temperature of 160°C. It was discovered that the use of microwaves significantly shortened the reaction time compared to using conventional electric heaters or other external heating systems and also allowed the use of lower concentrations of NaOH. Chemical Feedstock Recycling & Other Innovative Recycling Techniques 6     

Extraction of polybrominated diphenyl ethers contained in waste high impact polystyrene by supercritical carbon dioxide

A new recycling process for the supercritical CO₂ (sc-CO₂) extraction of polybrominated diphenyl ethers from waste high impact polystyrene (HIPS) was developed in this paper. HIPS was first dissolved in d-limonene. The remaining decabromo diphenyl ether (decaBDE) particles in solution were then removed by centrifugation, and the PBDEs in the centrifugate solution were further extracted by sc-CO₂. The influence of temperature and pressure, the volume ratio of sc-CO₂ to plastic solution, and the concentration of decaBDE in the solution on the separating efficiency were investigated. The decaBDE particles in 20 % of the HIPS solution can be removed by centrifugation at a speed of 10,000 r/min at 30 °C. The suitable sc-CO₂ fluid conditions were 65 °C and 20 MPa, and the optimum volume ratio of the sc-CO₂ to the HIPS solution was 2:1. More than 97 % of the PBDEs were successfully removed, and the concentration of PBDE residues in the recycled HIPS was reduced to lower than 0.1 % (dry) by this recycling process.     

The Properties of Poly(<Emphasis Type="SmallCaps">l</Emphasis>-Lactide) Prepared by Different Synthesis Procedure

Different synthesis methods were applied to determine optimal conditions for polymerization of (3S)-cis-3,6-dimethyl-1,4-dioxane-2,5-dione (l-lactide), in order to obtain poly(l-lactide) (PLLA). Bulk polymerizations (in vacuum sealed vessel, high pressure reactor and in microwave field) were performed with tin(II) 2-ethylhexanoate as the initiator. Synthesis in the vacuum sealed vessel was carried out at the temperature of 150 °C. To reduce the reaction time second polymerization process was carried out in the high pressure reactor at 100 °C and at the pressure of 138 kPa. The third type of rapid synthesis was done in the microwave reactor at 100 °C, using frequency of 2.45 GHz and power of 150 W at the temperature of 100 °C. The temperature in this method was controlled via infrared system for in-bulk measuring. The solution polymerization (with trifluoromethanesulfonic acid as initiator) was possible even at the temperature of 40 °C, yielding PLLA with narrow molecular weight distribution in a very short period of time (less than 6 h). The obtained polymers had the number-average molecular weights ranging from 43,000 to 178,000 g mol⁻¹ (polydispersity index ranging from 1 to 3) according to the gel permeation chromatography measurements. The polymer structure was characterized by Fourier transform infrared and NMR spectroscopy. Thermal properties of the obtained polymers were investigated using thermogravimetry and differential scanning calorimetry.     

The mild hydrothermal synthesis of hydrogrossular from coal ash

In this study, an attempt was made to synthesize hydrogrossular, a group of garnet minerals, under hydrothermal conditions at temperatures below 180°C, using coal ash, which is the solid waste from thermal power plants, as a starting material. A single phase corresponding to hydrogrossular was found at around 120°C, and the hydrogrossular coexisted with 11-Å tobermorite above 140°C. The hydrogrossular phase decreased with increasing reaction temperature, while that of 11-Å tobermorite increased concurrently. The physicochemical properties of the hydrogrossular obtained from the hydrothermal synthesis was characterized by X-ray diffraction thermogravimetry/differential thermal, analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray fluorescence spectroscopy. Received: September 4, 2000 / Accepted: March 7, 2001     

Feature of Dust Particles in the Spring Free Troposphere over Dunhuang in Northwestern China: Electron Microscopic Experiments on Individual Particles Collected with a Balloon-borne Impactor

Free tropospheric aerosol particles were collected using a balloon-borne particle impactor in August of 2002 and March of 2003 at Dunhuang in northwestern China (40°00′N, 94°30′E), and the morphology and elemental composition of the aerosol particles were analyzed in order to understand the mixing state of coarse dust particles (diameter >1 μm) over the desert areas in the Asian continent in spring. Electron microscopic experiments on the particles revealed that dust particles were major constituents of coarse mode particles in the free troposphere over the Taklamakan Desert in spring and summer. Si-rich or Ca-rich particles are major components of dust particles collected in the free troposphere over dunhuang and the values of [number of Ca-rich particles]/[number of Si-rich particles] differs markedly between spring and summer, being about 0.3 in the spring of 2003 and about 1.0 in the summer of 2002 at heights 3–5 km above sea level. It is likely that the condition of the ground surface and the strength of vertical mixing in source areas of Asian dust are potential factors causing the difference in the chemical types of dust particles. Comparison of the elemental compositions of these particles with those of particles collected over Japan strongly suggests that these particles were chemically modified during their long-range transport in the free troposphere. Analysis of wind systems shows that both the predominating westerly wind in the free troposphere and the surface wind strongly controlled by the geographical structure of the Tarim Basin are important in the long-range transport of KOSA particles originating in the Taklamakan Desert.     

Modification of Thermo-Mechanical Properties of Recycled PET by Vinyl Acetate (VAc) Monomer Grafting Using Gamma Irradiation

Vinyl acetate (VAc) monomer of different percentage was grafted onto the recycled polyethylene terephthalate (r-PET) films using gamma irradiation. The properties of these modified films were characterized by Fourier transform infrared spectroscopy (FTIR), mechanical properties testing (Tensile strength, Elongation at break), dynamic mechanical analysis (DMA) and thermo-gravimetric analysis (TGA). The Tensile Strength (TS) of the modified PET film increased by 132.25?% to the highest value of 50.12 MPa at 15% VAc monomer concentration at 3 kGy gamma dose, while the elongation at break (EB) decreased by 31.83?%. FTIR was used to investigate the molecular interaction of the modified films. TGA revealed that curve of the modified PET film shifted toward higher temperature region by 95?°C, which is very close to that of PET film made from virgin flakes. The results indicate that modified PET films of better mechanical and thermal properties were successfully prepared using VAc monomer grafting by gamma irradiation technique.     

A research note on the assessment of optimum conditions for preparing soils for bioremediation feasibility testing

In this applied study, the effects of short‐term storage at 22°C, 6°C, and ?25°C on the numbers of microorganisms enumerated were examined with soils collected from a petrochemical contaminated soil containing multiple contaminants including phenol, polycyclic aromatic hydrocarbons, and petroleum hydrocarbons. Short term storage of soils at refrigerator temperature did not significantly change the number of microorganisms compared to those in the fresh soil (0 days of storage); however, at ?25°C there was a slight decrease in the phenol utilizers and total viable count (TVC). Long‐term storage caused a significant decrease in the number of phenol utilizers in the petrochemical‐contaminated soil samples. Chemical dispersing agents were used in an attempt to increase the extraction of microorganisms from naphthalene contaminated soil which were predominantly clay soils. These did not significantly change the enumeration of naphthalene utilizers or TVC. While these results are not unexpected from current research and knowledge of microbial community succession in laboratory environments, the results from the applied nature of this study confirm that it is best practice to keep soil samples designated for bacterial enumeration for the shortest possible time, and not longer than 1–2 weeks, and at refrigerated temperature (6°C) in preference to room (22°C) or deep freezer (?18°C) temperatures.     

Debromination of flame-retarded TV housing plastic waste

The thermal stability and degradation kinetics of TV housing plastic and brominated flame retardants were studied by means of thermogravimetry. The effects of the treatment temperature on the removal rate of Br were investigated using a tube furnace reactor under isothermal and vacuum conditions. The results showed that the weight loss of TV housing plastic was divided into two stages: the thermal degradation of brominated flame retardants mainly occurred at 290°–350°C, and the degradation of the high-impact polystyrene resin mainly occurred at 350°–455°C. Nearly 90% of Br can be removed from TV housing plastic when the treatment temperature exceeds 280°C.     

Techniques to separate metal from waste printed circuit boards from discarded personal computers

Waste printed circuit boards contain valuable metals such as Au, Pd, Ag, and Cu that can be reutilized and harmful elements such as Pb, Br, and Cr that must be removed from the viewpoint of environmental conservation. In this research, we examined a method that separates the materials from printed circuit boards contained in discarded personal computers. After cutting the printed circuit boards to a size of 20 × 20 mm, they were heated at 873 K under an Ar atmosphere to remove organic resins containing elements such as C, H, and N. After heat treatment, the printed circuit boards were crushed using a planetary ball mill and the pulverized powders were filtered. The fraction with a granularity of greater than 250 μm was separated into magnetic and nonmagnetic materials by a magnetic field. Because the fraction with a granularity of less than 250 μm contained 39 mass% of C, it was heated at 1273 K in an atmosphere of 95% Ar and 5% O₂ to allow carbon combustion to take place, followed by metal reduction processing at the same temperature in an atmosphere of 97% Ar and 3% H₂. The basicity of the resulting powder was adjusted and the powder was heated at 1773 K under an Ar atmosphere. The proposed method separated the slag and metal, and 80% of the valuable metals contained in printed circuit boards could be collected.     

Effects of the type of sintering atmosphere on the chromium leachability of thermal-treated municipal solid waste incinerator fly ash

The sintering process offers an opportunity to combine detoxification and resource recovery for the treatment of municipal solid waste (MSW) incinerator fly ash. However, the chromium (Cr) in the sintered fly ash becomes more readily leachable with increasing sintering time and temperature, thus posing severe threats to the environment and human health when the sintered ash is recycled or reused. This study investigated the enhanced leachability of fly ash containing Cr, by heating the chromium (III) oxide (Cr2O3)-spiked fly ash to 800 degrees C in atmospheres containing air, nitrogen gas (N2), and 5% H2 + 95% N2, respectively. The results indicated that trivalent chromium was converted to its soluble hexavalent form during sintering in the air atmosphere; whereas sintering in a nitrogen atmosphere significantly reduced the leachability of Cr due to lack of oxygen (O2) to oxidize. The effects of the sintering temperature on the total chromium content and the leaching concentration in the toxicity characteristic leaching procedure (TCLP) extract are also discussed.     

The leaching behavior of borate waste glass SL-1

Vitrification is an attractive approach for treatment of the borate waste from nuclear power plants. SL-1 glass is a suitable borosilicate glass form to solidify the borate waste containing relatively high quantities of B and Na. The leaching behavior of SL-1 glass in deionized water has been investigated. Compared to the HLW-glass, the network structure of SL-1 glass is weak. It was found that the ion-exchange reactions dominated the glass corrosion process with water in low temperature leaching conditions (⩽70°C). The ion-exchange and network hydrolysis reactions together controlled the glass dissolution in high temperature leaching conditions (>70°C). There was a peak in leach rate at about 70°C and a valley at about 110°C. The surface layer thickness was about 25 μm (MCC-1, 90°C for 28 days in deionized water). Na was almost totally depleted in the surface layer. At low temperature, the glass corrosion increases with leaching time. The glass corrosion remains about constant with leaching time at 90°C. The surface layer formed at 90°C is protective, which is less porous than the surface layer formed at 40 and 70°C.     

Biodegradation of Bloodmeal-Based Thermoplastics in Green-Waste Composting

Polymers that are compostable and manufactured from renewable resources have gained significant importance in recent years. The objective of this work was to assess the biodegradability of bloodmeal-based thermoplastics in a commercial green-waste composting situation. Materials plasticised with tri-ethylene–glycol lost about 45% of their original mass after 12 weeks composting while unplasticised samples lost 35%. Degradation appeared to have been in two phases; an initial loss of soluble, low molecular compounds in the mesophilic phase followed by degradation of high molecular compounds as the temperature exceeded about 40 °C in the thermophilic phase. It was found that as degradation proceeded materials became more soluble. In addition, plasticised and unplasticized samples contained about 60 wt% moisture after 4 weeks of composting conditioning at 50% relative humidity resulted in approximately 8–10 wt% moisture, unaffected by the extent of degradation. FTIR revealed that proteins underwent hydrolytic cleavage resulting in the formation of primary amines. A significant reduction in combustion temperature was observed, indicative of a reduction in covalent bonding, likely due to shorter chains lengths or less cross-linking.     

Liquefaction process for a hydrothermally treated waste mixture containing plastics

Most landfilled plastic waste is a mixture or is in the form of composites with incombustible wastes such as glass, metals, and ceramics. After hydrothermal treatment, including a steam-explosion process, the separation of mixed waste (MW) into organic and inorganic substances becomes easy. However, the effect of hydrothermal pretreatment on the subsequent liquefaction of organic substances from MW is not obvious. In this study, the effects on the liquefaction of polystyrene and high-density polyethylene are discussed. Moreover, optimum conditions for the liquefaction of organic substances from hydrothermally treated MW are identified. By means of this hydrothermal pretreatment, including the steam-explosion process, polystyrene and high-density polyethylene can be significantly converted to oil by liquefaction at 300°–400°C. In comparison with liquefaction of hydrothermally pretreated mixed waste (HMW) at 300°–400°C with a batch type reactor, the yield of oil increases significantly on liquefaction using a semi-batch type reactor. It is considered that the radical chain and termination reactions among the radicals from HMW were inhibited in the semi-batch type reactor. On liquefaction of HMW in a semi-batch reactor, the conversion of HMW to oil was enhanced on increasing the liquefaction temperature to 350°C and the holding time to 60 min. Chemical Feedstock Recycling & Other Innovative Recycling Techniques 6     

Comprehensive temperature monitoring in an in-vessel forced-aeration static-bed composting process

Comprehensive temperature monitoring was done in an in-vessel forced-aeration static-bed composting process using sewage sludge. The three layers that divided the compost pile horizontally showed different temperature distributions. The temperature of the top layer appeared not to be influenced by the ambient temperature. The temperature of the center area of the top layer was taken to be the representative temperature for evaluating composting start-up performance. The temperature of the bottom layer was strongly influenced by the ambient temperature, and the temperature of the center area of the bottom layer was taken to be the representative temperature for pathogen control as it was the minimum temperature in the reactor. Composting start-up performance was influenced by several factors when the ambient temperature was either below or above 20°C. When the ambient temperature was below 20°C, the time taken to reach 65°C (T ₆₅) was influenced by the temperature of inflowing air, but when the temperature was higher than 20°C, it was influenced by the ratio of sewage sludge to seed compost (F/S). T ₆₅ was least when F/S was 1–2. Received: January 9, 2001 / Accepted: October 10, 2001     

Preparation of biochar catalyst with saccharide and lignocellulose residues of corncob degradation for corncob hydrolysis into furfural

This paper presented a novel process for production of furfural by hydrothermal degradation of corncob over biochar catalyst, in which it was prepared with the recycling degradation solution and lignocellulosic solid residues. The biochar catalyst was papered by lignocellulose residues and concentrated saccharide solution, and then impregnated in 0.5 mol/L sulphuric acid at room temperature for 24 h assisted by the ultrasonic vibration. In the system of recycling, 8.8 % lignocellulose residues and 100 % concentrated saccharide solution from corncob hydrolysis have been recycled. Hydrolysis of corncob was carried out at 180 °C for duration of 170 min over the biochar catalyst. The experimental results have shown that the furfural yield of up to 37.75 % and overall corncob conversion rate of 62.00 % could be achieved under optimum operating conditions for the catalysts preparation and the corncob hydrolysis. It is believed that the acid density of 4.27 mmol/g of biochar catalyst makes the SO₃H groups cleave β-1,4 glycosidic linkages effectively and hydrolyze the cellulose and hemicellulose to water-soluble sugars, as well as to facilitate dehydration of xylose to give the product of furfural.     

Waste glass as absorbent for thin layer chromatography (TLC)

This study shows that glass powder of 200–300 mesh size range can be used as an absorbent for thin layer chromatography without adding any binder provided its uniformity is improved by a suitable thermal treatment. For this purpose TLC plates of the said mesh size range glass powder are heated thermally in a muffle furnace at a temperature of 650 °C for a period of 3 h.     

Ethoxylated Soybean Polyols for Polyurethanes

Soybean polyols prepared by ring opening reactions of epoxidized soybean oil with hydrogen active compounds (water, alcohols, organic or inorganic acids, thiols, hydrogen etc.) have a low reactivity in the reaction with isocyanates because the hydroxyl groups are secondary. This paper presents a simple and convenient method to increase the reactivity of soybean polyols with secondary hydroxyl groups by ethoxylation reactions with the preservation of triglyceride ester bonds. The method uses mild reaction conditions: low alkoxylation temperature of 35–45 °C, low pressure of 0.1–0.2 MPa (15–30 p.s.i.) and a superacid as catalyst (HBF₄). The new soybean polyols have a higher reactivity toward isocyanates in polyurethane formation due to the high percentage of primary hydroxyl groups. The primary hydroxyl content was determined by the second order kinetics of polyol reaction with phenyl isocyanate.