Compressive strength and microstructure of alkali-activated mortars with high ceramic waste content

The present work investigated alkali-activated mortars with high ceramic waste contents. Tile ceramic waste (TCW) was used as both a recycled aggregate (TCWA) and a precursor (TCWP) to obtain a binding matrix by the alkali-activation process. Mortars with natural siliceous (quartz) and calcareous (limestone) aggregates, and with other ceramic waste materials (red clay brick RCB and ceramic sanitaryware CSW waste), were also prepared for comparison purposes. Given the lower density and higher water absorption values of the ceramic aggregates, compared to the natural ones, it was necessary to adapt the preparation process of the recycled mortars by presaturating the aggregate with water before mixing with the TCWP alkali-activated paste. Aggregate type considerably determined the mechanical behaviour of the samples cured at 65 °C for 3 days. The mortars prepared with the siliceous aggregate presented poor mechanical properties, even when cured at 65 °C. The behaviour of the limestone aggregate mortars depended heavily on the applied curing temperature and, although they presented the best mechanical properties of all those cured at room temperature, their compressive strength reached a maximum when cured at 65 °C, and then decreased. The mechanical properties of the mortars prepared with TCWA progressively increased with curing time (53 MPa at 65 °C for 28 days). An optimum 50 wt% proportion was observed for the limestone/TCWA mortars (≈43 MPa, 3 days at 65 °C), whereas the mechanical properties of that prepared with siliceous particles (10 MPa) progressively increased with the TCWA content, up to 100 wt% substitution (23 MPa). Limestone particles interacted with the binding matrix, and played an interesting beneficial role at the 20 °C curing temperature, with a slight reduction when cured long term (28 days) at 65 °C. The results demonstrated a potential added value for these ceramic waste materials.     

Production of alumino-borosilicate foamed glass body from waste LCD glass

A foaming process for waste LCD glass is presented, in which waste LCD glass is recycled to produce alumino-borosilicate foamed glass, which can eventually be used as a heat-insulating material, a light-weight aggregate for civil engineering applications, or a carrier for sewage treatment. The effects on waste LCD glass foaming of a variety of carbon foaming agents, metal salt foaming agents, and bonding agents are examined, as well as other factors such as chemical composition, foaming temperature, and grain size of the raw materials from the waste LCD glass. After examining all the variables that influence the foaming process, it was confirmed that the waste LCD glass is suitable as a raw material for producing alumino-borosilicate foamed glass. The alumino-borosilicate foamed glass has excellent physical properties, with density less than 0.14 g/cm³, heat conductivity less than 0.054 W/(mK) @20 °C, bending strength more than 35 N/cm², compressive strength more than 39 N/cm² and a coefficient of linear thermal expansion less than 4.5 × 10^?6 m/m °C. This clearly shows that the lightweight alumino-borosilicate foamed glass could be useful for various applications.     

The volatilization behavior of chlorine in coal during its pyrolysis and CO2-gasification in a fluidized bed reactor

The volatilization behavior of chlorine in three Chinese bituminous coals during pyrolysis and CO₂-gasification in a fluidized bed reactor was investigated. The modes of occurrence of chlorine in raw coals and their char samples were determined using sequential chemical extraction method. The Cl volatility increases with increasing temperature. Below 600 °C the Cl volatility is different, depending on the coal type and the occurrence mode of Cl. Above 700 °C, the Cl volatilities for the three coals tested are all higher than 80%. About 41% of the chlorine in Lu-an coal and 73% of that in Yanzhou coal are organic forms, and most of them are covalently-bonded organic chlorine, which shows high volatile behavior even at low pyrolysis temperatures (below 500 °C), while the inorganic forms of chlorine in two coal samples are hardly volatilized even at low pyrolysis temperatures (below 400 °C). The restraining efficiency of addition of CaO on chlorine volatility is greatly dependent on pyrolysis temperature. The optimal restraining efficiency can be obtained at temperature range from 450 to 650 °C during pyrolysis of Lu-an coal. The volatile behavior of Cl is mainly dependent on temperature. Above 700 °C high volatility of Cl is obtained in both N₂ and CO₂ atmospheres.     

Pyrolysis of two different biomass samples in a fixed-bed reactor combined with two different catalysts

Pyrolysis of Euphorbia rigida and sesame stalk biomass samples with two selected commercial catalyst, namely DHC-32 and HC-K 1.3Q, have been conducted in a fixed-bed reactor. The effect of different catalysts and their ratio (5, 10 and 20% w/w) and pyrolysis temperature (500 and 750 °C) on the pyrolysis product yields were investigated and the obtained results were compared with similar experiments without catalyst. Bio-oil yield was increased comparing with non-catalytic experiments, at final pyrolysis temperature of 500 °C for both biomass samples and catalysts. In the catalytic experiments; when the temperature reached to 750 °C, although bio-oil product yield was reduced, the gas product yield was increased comparing with non-catalytic experiments.The pyrolysis oils were examined using spectroscopic and chromatographic analyses and then fractioned by column chromatography. Although the aliphatic and aromatic fractions were decreased and polar fraction was increased with catalytic pyrolysis of E. rigida; an opposite trend was observed in the sesame stalk pyrolysis oil, comparing with non-catalytic results.Obtained results were compared with petroleum fractions and determined the possibility of being a potential source of renewable fuels.     

Possible use of waste serpentine from Abdasht chromite mines into the refractory and ceramic industries

There are approximately 20.5 million tons of waste rocks in Abdasht chromite mines which might cause considerable environmental problems in the near future. Serpentine is one of the most important rocks that can be abundantly found in this mine. In this work, the waste serpentine was processed by dry magnetic drum separator. Chemical analysis showed high content of MgO in the non-magnetic fraction (NMF) serpentine that reached to 47.85% after calcining at 1050 °C. The XRD result revealed that antigorite was the main phase of the NMF-serpentine while the major phase of the samples fired at 1050–1650 °C was forsterite. Considerable water absorption after 2 h dwell time at 1650 °C, indicated high refractoriness and high sintering temperature of the waste serpentine from Abdasht mines. These results proved the potential capability of waste serpentine from Abdasht mines as a raw material to be used in high temperature refractory and ceramic products.     

Study on the possibility of waste mushroom medium as a biomass resource for biorefinery

In order to investigate the possibility of waste mushroom medium as a biomass resource for biorefinery, characteristics of hydrolysate and pretreated biomass obtained from oxalic acid pretreatment were examined. The hydrolysate contained high glucose and low concentrations of inhibitors. The glucose concentration in the hydrolysate particularly increased when temperature gradient was used during pretreatment, compared with that of isocratic condition. The highest increase rate of glucose was 63.16% when pretreatment was performed at 140 °C for 25 min with 0.032 oxalic acid (g/g), and increased temperature to 170 °C. At the same time, ethanol production of Scheffersomyces stipitis using hydrolysate was 15.72 g/L after 48 h, which correspond to an ethanol volumetric productivity of 0.33 g L^?1 h^?1. Most of the lignin and some of the cellulose remained in the pretreated biomass. The total lignin content of the pretreated biomass, represent between 31.81 and 45.05%, compared to 28.8% of the raw material. The calorific value of the pretreated biomass ranged from 4940 to 5111 kcal/kg which represent increase of 3–6% compared to the raw material, due to higher contents of lignin in the pretreated biomass.     

Synthesis of large plate-like gypsum dihydrate from waste gypsum board

This paper reports the synthesis of large plate-like gypsum (calcium sulfate) dihydrate generated from waste gypsum board via a wet process. Gypsum hemihydrate was formed by dehydrating waste gypsum board in a sodium sulfate solution at 100 °C for 1 h to form needle-like crystals. The large gypsum dihydrate was formed by lowering the temperature of the gypsum hemihydrate suspension below 80 °C. The large plate-like gypsum dihydrate was obtained by adding seed crystals to a suspension cooled at 80 °C. When 40 μm seed crystals were added at 0.5 mass%, the large plate-like gypsum dihydrate crystals obtained from waste gypsum board had average dimensions of 250 μm length × 100 μm width × 35 μm thickness.     

Preparation and properties of porous ceramic aggregates using electrical insulators waste

In this paper, porous ceramic aggregates were prepared by electrical insulators waste (EIW). Effects of sintering temperature and content of EIW on the aggregates’ properties such as bulk density, and apparent porosity, total porosity, and cold crushing strength were investigated. With increasing sintering temperature and content of EIW, bulk density and cold crushing strength of the aggregates increased, apparent porosity and total porosity decreased. Based on these results, total porosity of specimens in group B sintered at 1200 °C is 62.0%, cold crushing strength is 35.3 N, and thermal conductivity is 0.165 W/(m K) at 300 °C. Comprehensive properties of specimens can be optimized by adjusting sintering temperature. Meanwhile, strength variation resulted from the combined effects of phase transformation and matrix densification under different sintering temperatures.     

Microwave-enhanced formation of glucose from cellulosic waste

The conversion of cellulose and cellulosic waste to fermentable sugars has been successfully demonstrated. Using a novel microwave intensified hydrothermal depolymerisation of cellulosic materials in liquid hot water, at pressures below 300 psi, conversions of up to 40% of fermentable sugars were obtained with limited by-product formation. A high selectivity for glucose over other sugars has been observed. Temperature is the crucial parameter as limited conversion is observed below 180 °C and optimum conversion is attained around 220 °C.     

Effect of pyrolysis temperature on the pore structure evolution of polysiloxane-derived ceramics

Homogeneous silicon oxycarbide (SiOC) ceramic powders were prepared by pyrolysis of cross-linked polysiloxane at different temperatures (1250–1500 °C) under vacuum. The effect of pyrolysis temperature on the pore structure evolution was investigated by means of N₂ adsorption, SEM, XRD, IR and element analysis (EA). Studies showed that predominate mesoporous ceramics with the average pore size in the range of 2–13 nm were obtained after pyrolysis in this temperature range. The pore structure transformation is strongly correlated with the thermolytic decomposition process of the used precursor, such as phase separation and carbothermal reduction. At relatively lower temperature (1250–1350 °C), the ceramics had a relative small specific surface areas (35 m²/g) owing to the low degree of carbothermal reduction. However, as the carbothermal degree had an obvious augment at relative higher temperature (1400–1450 °C), the specific surface areas and total pore volume increased and reached to the maximum of 66 m²/g and 0.214 cm³/g, respectively, and subsequently decreased rapidly after 1500 °C for the reason of partial sintering of the nano-sized SiC derived from polysiloxane.     

Preparation and characterization of the one-piece wall ceramic board by using solid wastes

For the purpose of building energy-saving, a novel one-piece wall ceramic board was prepared by using fly ash and ceramic waste as the main raw materials for its matrix part and foam part, respectively. The effects of raw material composition, sintering temperature on the macro and micro properties were systematically investigated. The optimum parameter for the matrix part was obtained at 1220 °C with 70 wt% fly ash and 4 wt% quartz, while that for the foam part was 1220 °C with 97 wt% ceramic waste and 3 wt% silicon carbide. For the matrix sample, the highest rupture modulus reaches 53.97 MPa, and the corresponding water absorption capacity and thermal conductivity are 1.08% and 0.54396 W/(m K), respectively. For the foam part, the best bulk density and thermal conductivity are 443 kg/m³ and 0.10528 W/(m K), respectively. Subsequently, the optimal matrix and foam samples were introduced into the co-fired process (1220 °C), and the results show that the new method for the preparation of one-piece wall ceramic board was fully acceptable. Furthermore, the simulated results indicate that the proposed one-piece wall ceramic board can efficiently reduce the thermal bridges and exerts excellent energy conservation effect.     

Liquid fuels and chemicals from pyrolysis of motorcycle tire waste: Product yields,compositions and related properties

In this study, experiments have been conducted on the sample of solid motorcycle tire wastes to determine particularly the effect of temperature, feed size, and apparent vapor residence time on the pyrolysis product yields and their compositions. The maximum liquid yield of 49 wt.% was obtained at a final pyrolysis temperature of 475 °C, feed size 4 cm³, with a residence time of 5 s under N₂ atmosphere in a fixed-bed fire-tube heating reactor system. The pyrolysis liquid products were characterized by elemental analysis and various chromatographic and spectroscopic techniques. Chromatographic and spectroscopic studies on the liquids show that it can be used as liquid fuels and chemical feedstock, with a calorific value of 42.00 MJ/kg and empirical formula of CH_1.27O_0.025N_0.006.     

Aluminum titanate based ceramics from aluminum sludge waste

This work aims at obtaining aluminum titanate-based ceramics (Al₂TiO₅: AT) composites from industrial wastes. Al-sludge waste and rutile ore were used as rich sources of alumina and titania instead of pure materials. Sludge-(0–40 wt%) rutile mixtures were mixed, formed and fired at 1350 °C for various times. Phase composition, microstructure, densification, mechanical and thermal behaviors of the obtained AT composites have been investigated. Complete conversion of the starting materials to AT with bulk density of 3.199 g/cm³, compressive strength and modulus of rupture of 326.425 MPa and 30.84 MPa, respectively and very low CTE (−0.927*10⁻⁶ K⁻¹) were achieved by firing the sludge-(30 wt%) rutile at 1350 °C for 4 h. These results suggest that the obtained AT-ceramics from Al-sludge waste-rutile ore are a promising and an ecofriendly route.     

Effects of thermal pretreatment in helium on the pyrolysis behaviour of Loy Yang brown coal

A wire-mesh reactor capable of multi-step heating/holding and minimising secondary reactions of volatiles was used to investigate the effects of thermal pretreatment in inert gas on the subsequent rapid pyrolysis behaviour of Loy Yang brown coal. Our results indicate that the presence of small amounts (<10 wt%) of moisture in brown coal has little influence on the tar and char yields from the pyrolysis of brown coal at 1000 K s⁻¹. While the hydrogen bonds between the moisture and the O-containing functional groups in the brown coal have little effects on its pyrolysis behaviour, the hydrogen bonds among the O-containing functional groups tend to induce cross-linking reactions to reduce the tar yields. Preheating the brown coal at >250 °C leads to reduced tar and increased char yields. However, the characterisation of tars using UV-fluorescence spectroscopy indicates that significant decreases in the release of larger aromatic ring systems are only observed after preheating at >380 °C for 30 min. The presence of ion-exchangeable cations (e.g. Ca²⁺) in the brown coal tends to stabilise the carboxylate groups and only preheating at >350 °C would result in changes in pyrolysis yields during the subsequent pyrolysis at 1000 K s⁻¹. These results may be explained by considering the formation of cross-links involving peripheral groups at low preheating temperatures and the formation of cross-links involving aromatic ring systems at elevated temperatures.     

Synthesis of Fe/Fe3C nanoparticles encapsulated in nitrogen-doped carbon with single-source molecular precursor for the oxygen reduction reaction

Ammonium ferric citrate (AFC) was used as a single-source molecular precursor to prepare Fe/Fe₃C nanoparticles encapsulated in nitrogen-doped carbon by pyrolysis in Ar atmosphere followed by acid-leaching. Comparative studies, using citric acid and ferric citrate as the precursors, indicated that the ammonia and ferric ion in AFC and the pyrolysis temperature affected the composition of iron species and the properties of carbon in AFC-derived materials. Above the pyrolysis temperature of 600 °C, the iron species were Fe/Fe₃C, and the carbon had a hollow graphitic nanoshell structure in AFC-derived materials. The specific surface area and content of nitrogen element decreased with increasing pyrolysis temperature. The AFC-derived material pyrolyzed at 600 °C had the optimal graphitization degree, specific surface area (489 m² g⁻¹) and content of nitrogen (1.8 wt.%), thus resulted in the greatest activity for oxygen reduction reaction among the AFC-derived materials pyrolyzed at different temperatures. The AFC-derived material pyrolyzed at 600 °C exhibited improved methanol-resistance ability compared with Pt/C catalyst.     

Sintering behavior of waste serpentine from abdasht chromite mines Abdasht chromite mines and kaolin blends

The aim of this study is investigating on sintering behavior of Abdasht waste serpentine and kaolin blends. According to this, three formulations of dry milled waste serpentine with 25%, 50% and 75% high grade kaolin were wet milled. The slurries were then dried, sieved and uniaxially pressed at 100 MPa and fired for 2 h soaking time at temperatures between 1100 and 1400 °C. Sintered samples were investigated by bulk density, apparent porosity, water absorption, linear shrinkage and phase changes with raising temperatures in order to characterize their sintering process. It was revealed that all samples were starting to melt at 1350 °C and the sintering was completed for all specimens at 1300 °C. The only phases of fully sintered samples were cordierite and enstatite. Cordierite concentration, however, increased with enhancing kaolin percentage in composition. The results of this study can introduce Abdasht waste serpentine as magnesium silicate source into the ceramic industries and may help to solve environmental problems caused by several million tones wastes in Abdasht chromite mines.     

A small angle X-ray scattering and electrochemical study of the decomposition of wood during pyrolysis

The pyrolysis of nine wood samples (Basswood, Cherry, Pine, Walnut, Maple, Hickory, Paduak, Tigerwood and Ipe) between 30 and 1200 °C was investigated. Using Small angle X-ray scattering (SAXS), the thermal degradation of the cellular structure of wood followed by the onset and growth of graphene sheets and associated nanoporosity between the sheets, was observed as temperature increased. SAXS, wide angle X-ray scattering and electrochemical studies of Na insertion using Na batteries were used to study the wood samples pyrolyzed to 1100 °C. Regardless of the original wood precursor used during pyrolysis, the nanostructure and resulting electrochemical behaviour of all the wood samples were similar after heating to 1100 °C.     

Environmental aspects of gasification of Korean municipal solid waste in a pilot plant

Municipal solid waste was gasified in a 3 ton/day capacity pilot plant based on thermoselect process with oxygen at a temperature of around 1200 °C. CO and H₂ content of synthesis gas were about 27–40 and 36–40%, respectively with high heating value 8.0–10.2 MJ/N m³. Chlorinated compounds like furan, dioxin, and other organics in gaseous and liquid phase were effectively destroyed due to high temperature of high temperature reactor and shock cooling. Exhaust gases were also found to be satisfying the Korean emission standard. Leachable concentration of heavy metals in the vitrified mineral aggregate were much less than the Korean regulatory limit values due to high melting temperature (1600 °C). The vitrified slag of dark brown color was found to be glassy and non-hazardous in nature and seems to have the possibility to be used as natural raw material in cement and construction industry.     

Structural study of mullite based ceramics derived from a mica-rich kaolin waste

Mullite-based ceramics have been synthesized by reactive sintering of a mixture containing kaolin and a mica-rich kaolin waste. Samples fired in the temperature range from 1300 to 1500 °C were characterized by X-ray diffraction (XRD). The quantitative phase analysis and unit cell parameters of the mullite were determined by Rietveld refinement analysis of the XRD data. Mullite-based ceramics with 1.2 wt% quartz, 56.3 wt% glass (amorphous phase), 2.64 g/cm³ of apparent density, and 35±1.2 MPa of flexural strength were obtained after firing at 1500 °C. A liquid phase sintering mechanism activated by a total mica content of 13.3 wt% allowed to increase the mullite content to 47.6 wt% (2.3 wt% quartz and 50.1 wt% glass phase) and improve the flexural strength (70±3.9 MPa) after firing at 1400 °C.     

Biodiesel production from waste tallow

In the present investigation an attempt has been made to use waste tallow as low cost sustainable potential feed stock for biodiesel production. Effect of various process parameters such as amount of catalyst, temperature and time on biodiesel production was investigated. The optimal conditions for processing 5 g of tallow were: temperature, 50 and 60 °C; oil/methanol molar ratio 1:30 and 1:30, amount of H₂SO_4, 1.25 and 2.5 g for chicken and mutton tallow, respectively. Under optimal conditions, chicken and mutton fat methyl esters formation of 99.01 ± 0.71% and 93.21 ± 5.07%, was obtained after 24 h in the presence of acid. The evaluation of transesterification process was followed by gas chromatographic analysis of tallow fatty acid esters. A total of 98.29% and 97.25% fatty acids were identified in chicken and mutton fats, respectively. Both fats were found highly suitable to produce biodiesel with recommended fuel properties.