Publications
260 results found
Kia A, Wong H, Cheeseman C, 2018, High strength porous cement-based materials, P120039GB
Kiventerä J, Sreenivasan H, Cheeseman C, et al., 2018, Immobilization of sulfates and heavy metals in gold mine tailings by sodium silicate and hydrated lime, Journal of Environmental Chemical Engineering, Vol: 6, Pages: 6530-6536, ISSN: 2213-3437
Gold mining produces hazardous tailings wastes with elevated sulfur content and high levels of heavy metals including oxyanion elements such as V and As. This research investigated activation of these tailings with calcium hydroxide and sodium hydroxide/sodium silicate as a way to stabilize the material and limit leaching of harmful components. The effects of thermal treatment on the reactivity of the tailings and the use of different activating solutions on the physical properties, microstructure and leaching of harmful components are reported. The effect of adding ground granulated blast furnace slag to the tailings is also assessed. The use of 5 wt % Ca(OH)2 activating solution produces optimum performance increasing the immobilization efficiency of sulfates, arsenic and the other harmful elements. Heat-treating mine tailings at 900 °C slightly improves the reactivity but did not improved the immobilization efficiency. Microstructural analysis by TEM and XRD confirmed that stabilization is based on calcium sulfate and/or ettringite formation during alkali-activation. All materials achieved reasonable compressive strength after 28 days of curing and the potential for using alkali activation as a method to treat tailings from mining is discussed.
Cheeseman C, Kumar S, Arya S, 2018, Solid waste management in Nagpur, India: The bin-free city, Waste Management, Vol: 80, Pages: III-IV, ISSN: 1879-2456
Kumi-Larbi A, Yunana D, Kamsouloum P, et al., 2018, Recycling waste plastics in developing countries: Use of low-density polyethylene water sachets to form plastic bonded sand blocks, Waste Management, Vol: 80, Pages: 112-118, ISSN: 0956-053X
In many developing countries low-density polyethylene (LDPE) sheets, bags and water sachets are a major waste problem because local collection and recycling systems do not exist. As a result, LDPE has no value and is dumped causing aesthetic, environmental and public health issues. A relatively simple technology has been developed in the Cameroon that produces LDPE-bonded sand blocks and pavers. The application of this technology is an example of a community-driven waste management initiative that has potential to impact on the global plastics waste crisis because it can transform waste LDPE and other readily available types of plastics into a valuable local resource. In this research, waste LDPE water sachets have been melted and mixed with sand to form LDPE-bonded sand blocks. The effect of sand particle size and sand to plastic ratio on density, the compressive strength and water adsorption are reported. Optimum samples have been further characterised for flexural strength and thermal conductivity. LDPE-bonded sand is a strong, tough material with compressive strengths up to ∼27 MPa when produced under optimum processing conditions. The density and compressive strength increase as the particle size of the sand decreases. The potential for using this simple technology and the materials it produces to transform LDPE plastic waste management in developing countries is discussed.
Dieckmann E, Dance S, Sheldrick L, et al., 2018, Novel sound absorption materials produced from air laid non-woven feather fibres, Heliyon, Vol: 4, Pages: 1-13, ISSN: 2405-8440
This research has investigated the use of feather fibres to produce sound absorption materials as an alternative to the oil derived synthetic plastics that currently dominate the sound absorption materials market. In this paper we show that clean and disinfected waste feathers from the poultry industry can be processed into fibres and air laid using commercial pilot plant facilities to form non-woven feather fibre composite mats. By varying the composition and processing conditions, materials with a range of different properties such as thickness and density were produced. The sound absorption coefficients of samples was determined using the impedance tube method (BS EN ISO 10534-2: 1998), using normal incidence sound between 80 and 1,600 Hz. The data reported shows that air laid non-woven feather fibre mats have improved sound absorption coefficients compared to other natural materials used for sound absorption for a given thickness, particularly in the problematic low frequency range between 250 to 800 Hz. We conclude that air laid non-woven feather fibres have high potential to be used as effective and sustainable sound absorption materials in aerospace, automotive, buildings, infrastructure and other applications where sound absorption is required.
Fang L, Li JS, Donatello S, et al., 2018, Recovery of phosphorus from incinerated sewage sludge ash by combined two-step extraction and selective precipitation, Chemical Engineering Journal, Vol: 348, Pages: 74-83, ISSN: 1385-8947
The recovery of phosphorus (P) from acid extracts of incinerated sewage sludge ash (ISSA) is invariably complicated by the co-dissolution of metal(loid)s. An extra purification treatment step is thus needed, which reduces the efficiency of P recovery. This study developed a two-step extraction method which can produce highly purified P-extract where ISSA is treated first with ethylenediaminetetraacetatic acid (EDTA) and then with sulphuric acid. The recovery conditions of this two-step extraction method were optimized (pre-extraction by 0.02 mol/L of EDTA at a liquid to solid ratio (L/kg) of 20:1 during 120 min, then extraction by 0.2 mol/L sulphuric and at a liquid to solid ratio of 20:1 during 120 min). Compared with direct extraction by sulphuric acid (namely, single-step leaching), the two-step extraction method dissolved 2.34 mmol/kg ISSA less of P, but with 5.16 mmol/kg ISSA less of metal(loid) contamination. Furthermore, the potential for co-precipitation of P and the metal(loid) contaminates in the extracts (both single-step extraction and the two-step extraction methods) was examined from pH 2 to 12 (adjusted by addition of NaOH and Ca(OH)2). By applying Ca(OH)2and at the optimal pH of 4, the two-step extraction method could significantly increase Ca-P in the precipitate and notably decreased the metal(loid) contaminants by 50% compared to the single-step method.
Kia A, Cheeseman CR, Wong H, 2018, Control of clogging in conventional permeable concrete and development of a new high strength clogging resistant permeable concrete pavement, 38th Cement and Concrete Science Conference
Zhang T, Dieckmann E, Song S, et al., 2018, Properties of magnesium silicate hydrate (M-S-H) cement mortars containing chicken feather fibres, Construction and Building Materials, Vol: 180, Pages: 692-697, ISSN: 0950-0618
Fibres derived from waste chicken feathers have been used to reinforce magnesium silicate hydrate (M-S-H) cement mortars and Portland cement mortars using up to 5% of fibres by weight of dry binder. The properties of the feather fibre mortar composites including pH, density, flexural strength, compressive strength, toughness, thermal conductivity and microstructure are reported. Feather fibres bond very effectively into M-S-H cement mortars which has significantly lower pH (∼10.8) than Portland cement mortars (pH ∼ 12.6). Increasing the feather fibre content reduces the density, compressive strength, bending strength and thermal conductivity of samples but increases mortar toughness. The optimal feather fibre addition was determined to be 4 wt% by weight of dry binder content, based on ease of mixing the samples and the strength, toughness and thermal conductivity data. Potential applications for feather fibre reinforced M-S-H cement mortars boards are discussed.
Kia A, Wong HS, Cheeseman C, 2018, Defining clogging potential for permeable concrete, Journal of Environmental Management, Vol: 220, Pages: 44-53, ISSN: 0301-4797
Permeable concrete is used to reduce urban flooding as it allows water to flow through normally impermeable infrastructure. It is prone to clogging by particulate matter and predicting the long-term performance of permeable concrete is challenging as there is currently no reliable means of characterising clogging potential. This paper reports on the performance of a range of laboratory-prepared and commercial permeable concretes, close packed glass spheres and aggregate particles of varying size, exposed to different clogging methods to understand this phenomena. New methods were developed to study clogging and define clogging potential. The tests involved applying flowing water containing sand and/or clay in cycles, and measuring the change in permeability. Substantial permeability reductions were observed in all samples, particularly when exposed to sand and clay simultaneously. Three methods were used to define clogging potential based on measuring the initial permeability decay, half-life cycle and number of cycles to full clogging. We show for the first time strong linear correlations between these parameters for a wide range of samples, indicating their use for service-life prediction.
Vouk D, Nakic D, Stirmer N, et al., 2018, Influence of combustion temperature on the performance of sewage sludge ash as a supplementary cementitious material, Journal of Material Cycles and Waste Management, Vol: 20, Pages: 1458-1467, ISSN: 1611-8227
© 2018, Springer Japan KK, part of Springer Nature. The potential for using sewage sludge ash (SSA) as a supplementary cementitious material (SCM) has been investigated. Controlled combustion of sewage sludge collected in Croatia from two wastewater treatment plants produced SSA with different characteristics. These were used to substitute for cement in mortar samples. The chemical composition and physical properties of SSA depend on wastewater composition, the sludge treatment process and the combustion temperature. These factors influence the suitability of SSA to be used as a SCM. For three different combustion temperatures (800, 900 and 1000 °C), it was concluded that properties of fresh mortar were not affected while in the hardened state, the most favorable combustion temperature is 900 °C regarding mechanical properties. Regardless of combustion temperature, for all types of SSA used in mortars as cement replacement (up to 30%), the average decrease in both compressive and flexural strength values was less than 8% for every 10% of added SSA. The results presented indicate that using up to 20% replacement of cement by SSA produces mortars that meet the specific technical requirements analyzed in this work.
Kia A, Wong HS, Cheeseman CR, 2018, Development of clogging resistant permeable concrete, 13th International Symposium on Concrete Roads
Kia A, Wong HS, Cheeseman CR, 2018, Development of clogging resistant permeable concrete, Proceedings of the 9th International Workshop on Research and Innovations for Design of Sustainable and Durable Concrete Pavements
Zhang T, Zou J, Wang B, et al., 2018, Characterization of magnesium silicate hydrate (MSH) gel formed by reacting MgO and silica fume, Materials (Basel), Vol: 11, ISSN: 1996-1944
Magnesium silicate hydrate (MSH) gel was formed by reacting magnesium oxide (MgO) with silica fume (SF) in distilled water. The MSH was prepared using a MgO/SF molar ratio of 1.0 (40:60 weight ratio). Samples were analyzed during hydration process up to 300 days at room temperature. The MSH characterization has been carried out using a range of analytical techniques. Quantitative analysis was achieved using thermogravimetric analysis (TG/DTG) with a de-convolution technology. The structure of MSH gel was characterized using solid state nuclear magnetic resonance (29Si NMR) and Fourier transform infrared (FT-IR) spectroscopy. Transmission electron microscopy (TEM) was used to investigate MSH microstructure. Compared with natural magnesium silicate hydrate minerals, the structure of MSH gel is highly disordered and generates on the surface of particles, producing a shell structure with cavity. The molecular structure of MSH phase is layered. The results also show that the extent of polymerization of MSH gel is related to the solution pH during hydration.
Kia A, Wong HS, Cheeseman CR, 2018, Examining the clogging potential of permeable concrete and development of a high strength clogging resistant system, 4th Young Researcher’s Forum
Ayati B, Ferrándiz-Mas V, Newport D, et al., 2018, Use of clay in the manufacture of lightweight aggregate, Construction and Building Materials, Vol: 162, Pages: 124-131, ISSN: 0950-0618
Clay is used as a raw material for the production of lightweight aggregates because it is readily processed into suitable granules and forms low-density but high strength aggregate particles when sintered at relatively low temperatures. The use of waste clay generated by major infrastructure development projects to make lightweight aggregate has a positive environmental impact and contributes towards a more circular economy. This paper reviews the manufacturing process used to produce lightweight aggregates from clay and the influence of processing conditions on properties. It also reviews secondary materials that have been incorporated into clays to produce lightweight aggregates. Additional research is required to improve understanding of the effects of composition and production parameters on the pore structure, density, water adsorption and strength of clay derived lightweight aggregates.
Glymond D, Roberts A, Russell M, et al., 2018, Production of ceramics from coal furnace bottom ash, Ceramics International, Vol: 44, Pages: 3009-3014, ISSN: 0272-8842
Furnace bottom ash (FBA) is generated in significant quantities from coal fired power stations and is a problem when commercially viable reuse applications do not exist locally. Representative samples of FBA from the Kilroot power station in Northern Ireland have been milled, pressed and sintered at a range of temperatures to form new ceramic materials. The effect of adding recycled glass to the mix has been investigated. The optimum FBA ceramics were produced by sintering at 960 °C and these had a density of 2.388 g/cm3, zero water adsorption indicating minimal open porosity, and a Vickers hardness comparable to commercially available glass-ceramics. The addition of 20% by weight of glass reduced shrinkage during sintering, while the samples maintained high density and hardness. This glass addition allows greater dimensional control during sintering to form FBA ceramic tiles. The research demonstrates that FBA can be processed into ceramics for use in higher value products compared to conventional use as lightweight aggregate. Further research is required to optimize processing and fully characterize material properties. This novel approach to managing FBA has potential to transform a problematic waste in Northern Ireland into a valuable resource.
Li J-S, Chen Z, Wang Q-M, et al., 2018, Change in re-use value of incinerated sewage sludge ash due to chemical extraction of phosphorus, Waste Management, Vol: 74, Pages: 404-412, ISSN: 1879-2456
The potential of six different extractants to recover phosphorus (P) from incinerated sewage sludge ash (ISSA) was evaluated. Secondary effects such as the co-dissolution of Zn and Cu were also considered. The residual ISSA from each study was assessed in particular detail, focusing on the leachability of remaining Zn and Cu, major element composition, crystalline phases and overall degree of crystallinity and particle size distribution. The residual ISSA was also evaluated as a pozzolanic material using a Strength Activity Index (SAI) test with mortars containing Portland cement with a 20% substitution by ISSA. All results were compared to tests with untreated ISSA. Overall, the use of 3 of the 6 extractants could be ruled out due to poor P recovery potential and/or a serious compromise of the potential reuse of residual ISSA in Portland cement-based materials. The results highlight the added value of considering the potential reuse of residual ISSA when trying to optimize P recovery from ISSA by wet methods.
Zhou D, Wang R, Tyrer M, et al., 2017, Sustainable infrastructure development through use of calcined excavatedwaste clay as a supplementary cementitious material, Journal of Cleaner Production, Vol: 168, Pages: 1180-1192, ISSN: 0959-6526
Major infrastructure development projects in London produce large quantities of London clay and use significant volumes of concrete. Portland cement (CEM I) in concrete is normally partially replaced by supplementary cementitious materials such as ground granulated blastfurnace slag or pulverised fuel ash. The supply of supplementary cementitious materials is critical to the production of sustainable concrete. This study has investigated use of waste London clay as a supplementary cementitious material. The optimum calcined clay was produced at 900 °C and concrete made with 30 wt% of CEM I replaced by calcined clay had 28-day strengths greater than control samples. Compressive strengths of concrete containing calcined London clay were similar to concrete containing ground granulated blastfurnace slag and pulverised fuel ash. The production of calcined London clay emits ∼70 kg CO2/tonne and this is 91% lower than CEM I. 30 wt% replacement of CEM I by calcined London clay therefore produces concrete with ∼27% lower embodied carbon. London clay can be calcined to form a technically viable supplementary cementitious material and use of this in concrete would enable major civil infrastructure projects to contribute to a circular economy.
Colangelo F, Roviello G, Ricciotti L, et al., 2017, Mechanical and thermal properties of lightweight geopolymer composites, Cement and Concrete Composites, Vol: 86, Pages: 266-272, ISSN: 0958-9465
This research has investigated the properties of thermally insulating geopolymer composites that were prepared using waste expanded polystyrene as lightweight aggregate. The geopolymer matrix was synthetized using metakaolin and an alkaline activating solution. To improve its mechanical properties, this matrix was modified by the addition of an epoxy resin to form an organic-inorganic composite. Moreover, in order to reduce drying shrinkage marble powder was used as an inert filler. The materials obtained were characterized in terms of physico-mechanical properties, thermal performance and microstructure. The geopolymer expanded polystyrene composite have improved properties compared to Portland cement-based materials, with higher strengths and lower thermal conductivity. The research demonstrates the manufacture of sustainable lightweight thermally insulating geopolymer composites using waste expanded polystyrene.
Fang L, Li J-S, Guo MZ, et al., 2017, Phosphorus recovery and leaching of trace elements from incinerated sewage sludge ash (ISSA)., Chemosphere, Vol: 193, Pages: 278-287, ISSN: 0045-6535
Chemical extraction of phosphorus (P) from incinerated sewage sludge ash (ISSA) is adversely influenced by co-dissolution of metals and metalloids. This study investigated P recovery and leaching of Zn, Cu, Pb, As and Ni from ISSA using inorganic acids (sulphuric acid and nitric acid), organic acids (oxalic acid and citric acid), and chelating agents (ethylenediaminetetraacetic acid (EDTA) and ethylene diamine tetramethylene phosphonate (EDTMP)). The aim of this study was to optimize a leaching process to recover P-leachate with high purity for P fertilizer production. The results show that both organic and inorganic acids extract P-containing phases but organic acids leach more trace elements, particularly Cu, Zn, Pb and As. Sulphuric acid was the most efficient for P recovery and achieved 94% of total extraction under the optimal conditions, which were 2-h reaction with 0.2 mol/L H2SO4 at a liquid-to-solid ratio of 20:1. EDTA extracted only 20% of the available P, but the leachates were contaminated with high levels of trace elements under optimum conditions (3-h reaction with EDTA at 0.02 mol/L, pH 2, and liquid-to-solid ratio of 20:1). Therefore, EDTA was considered an appropriate pre-treatment agent for reducing the total metal/metalloid content in ISSA, which produced negligible changes in the structure of ISSA and reduced contamination during subsequent P extraction using sulphuric acid.
Kuenzel C, Zhang F, Ferrándiz-Mas V, et al., 2017, The mechanism of hydration of MgO-hydromagnesite blends, Cement and Concrete Research, Vol: 103, Pages: 123-129, ISSN: 0008-8846
The hydration of reactive periclase (MgO) in the presence of hydromagnesite (Mg 5 (CO 3 ) 4 (OH) 2 ·4H 2 O) was investigated by a variety of physical and chemical techniques. Hydration of pure MgO-water mixtures gave very weak pastes of brucite (Mg(OH) 2 ), but hydration of MgO-hydromagnesite blends gave pastes which set quickly and gave compressive strengths of potential interest for construction applications. The strengths of the blends increased with hydration time at least up to 28days, and were not significantly decreased by increasing the hydromagnesite content up to 30%. Raman spectroscopy suggests that an amorphous phase, of composition between that of brucite, hydromagnesite and water, may form. Small amounts of calcite also form due to CaO in the MgO source. Thermodynamic calculations imply that the crystalline phase artinite (MgCO 3 ·Mg(OH) 2 ·3H 2 O) should be the stable product in this system, but it is not observed by either XRD or FTIR techniques, which suggests that its growth may be kinetically hindered.
Kia A, Wong H, Cheeseman CR, 2017, CLOGGING POTENTIAL OF PERMEABLE CONCRETE, 37th Cement and Concrete Science Conference
Permeable concrete is used to reduce local flooding in urban areas. However, it is prone to cloggingby particulate matter and requires regular maintenance. This paper reports on the performance ofpermeable concrete exposed to different clogging test methods to further understand this complexphenomena. New methods were developed to study the clogging effect and to define a cloggingpotential. The tests involve applying flowing water containing sand and/or clay in cycles throughthe sample and measuring the change in flow rate. Clogging depends on the applied solution andexposure method used. Significant permeability reductions were observed in all samples,particularly when simultaneously exposed to sand and clay. This is because flocculated clayadhered to surface of sand particles and this caused increased clogging.
Lee MY, Tan J, Heng JYY, et al., 2017, A comparative study of production of glass microspheres by using thermal process, The 2nd International Conference on Materials Engineering and Nanotechnology, ISSN: 1757-8981
Microspheres are spherical particles that can be distinguished into two categories; solid or hollow. Microspheres typical ranges from 1 to 200 μm in diameter. Microsphere are made from glass, ceramic, carbon or plastic depending on applications. Solid glass microsphere is manufactured by direct burning of glass powders while hollow glass microspheres is produced by adding blowing agent to glass powder. This paper presented the production of glass microspheres by using the vertical thermal flame (VTF) process. Pre-treated soda lime glass powder with particle sized range from 90 to 125μm was used in this work. The results showed that glass microspheres produced by two passes through the flame have a more spherical shape as compared with the single pass. Under the Scanning Electron Microscope (SEM), it is observed that there is a morphology changed from uneven surface of glass powders to smooth spherical surface particles. Qualitative analysis for density of the pre-burned and burned particles was performed. Burned particles floats in water while pre-burned particles sank indicated the change of density of the particles. Further improvements of the VTF process in terms of the VTF set-up are required to increase the transformation of glass powders to glass microspheres.
Schaeffer N, Feng X, Grimes SM, et al., 2017, Recovery of an yttrium europium oxide phosphor from waste fluorescent tubes using a Brønsted acidic ionic liquid, 1-methylimidazolium hydrogen sulfate, Journal of chemical technology and biotechnology, Vol: 92, Pages: 2731-2738, ISSN: 0142-0356
BACKGROUNDSpent fluorescent lamps, classified as hazardous waste in the EU, are segregated at source. Processes for the recovery of critical rare-earth (RE) elements from the phosphor powder waste, however, often involve use of aggressive acid or alkali digestion, multi-stage separation procedures, and production of large aqueous waste streams which require further treatment.RESULTSTo overcome these difficulties phosphor powder pre-treated with dilute HCl was leached with a 1:1 wt. [Hmim][HSO4]:H2O solution at a solid:liquid ratio of 5%, at 80 °C for 4 h with stirring at 300 rpm to recover 91.6 wt% of the Y and 97.7 wt% of the Eu present. The yttrium-europium oxide (YOX), (Y0.95Eu0.05)2O3, recovered by precipitating the dissolved RE elements from the leach solution with oxalic acid and converting the oxalate to an oxide phase by heating, was characterised by FTIR, XRD and luminescence analysis. The analyses suggest the recovered oxide has the potential to be directly reused as YOX phosphor. Regeneration and reuse of the ionic liquid is achieved with only minor leaching efficiency losses found over four leaching/recovery cycles.CONCLUSIONThe recovery of yttrium europium oxide from waste fluorescent tube phosphor by a simple efficient low cost ionic liquid process has been developed.
Kumar S, Smith SR, Fowler G, et al., 2017, Challenges and opportunities associated with waste management in India, Royal Society Open Science, Vol: 4, ISSN: 2054-5703
India faces major environmental challenges associated withwaste generation and inadequate waste collection, transport,treatment and disposal. Current systems in India cannotcope with the volumes of waste generated by an increasingurban population, and this impacts on the environment andpublic health. The challenges and barriers are significant,but so are the opportunities. This paper reports on aninternational seminar on ‘Sustainable solid waste managementfor cities: opportunities in South Asian Association for RegionalCooperation (SAARC) countries’ organized by the Councilof Scientific and Industrial Research-National EnvironmentalEngineering Research Institute and the Royal Society. A priorityis to move from reliance on waste dumps that offer noenvironmental protection, to waste management systems thatretain useful resources within the economy. Waste segregationat source and use of specialized waste processing facilitiesto separate recyclable materials has a key role. Disposal ofresidual waste after extraction of material resources needsengineered landfill sites and/or investment in waste-to-energyfacilities. The potential for energy generation from landfill viamethane extraction or thermal treatment is a major opportunity,but a key barrier is the shortage of qualified engineers andenvironmental professionals with the experience to deliverimproved waste management systems in India.
Kia A, Wong HS, Cheeseman CR, 2017, Clogging in permeable concrete: a review, Journal of Environmental Management, Vol: 193, Pages: 221-233, ISSN: 0301-4797
Permeable concrete (or “pervious concrete” in North America) is used to reduce local flooding in urban areas and is an important sustainable urban drainage system. However, permeable concrete exhibits reduction in permeability due to clogging by particulates, which severely limits service life. This paper reviews the clogging mechanism and current mitigating strategies in order to inform future research needs. The pore structure of permeable concrete and characteristics of flowing particulates influence clogging, which occurs when particles build-up and block connected porosity. Permeable concrete requires regular maintenance by vacuum sweeping and pressure washing, but the effectiveness and viability of these methods is questionable. The potential for clogging is related to the tortuosity of the connected porosity, with greater tortuosity resulting in increased potential for clogging. Research is required to develop permeable concrete that can be poured on-site, which produces a pore structure with significantly reduced tortuosity.
Vouk D, Nakic D, Stirmer N, et al., 2017, USE OF SEWAGE SLUDGE ASH IN CEMENTITIOUS MATERIALS, Reviews on Advanced Materials Science, Vol: 49, Pages: 158-170, ISSN: 1605-8127
The potential for using sewage sludge ash (SSA) in cement mortars and concrete is reviewed. The chemical andphysical properties and pozzolanic activity of a range of different incinerated SSA samples indicates the potential toexploit the pozzolanic properties of this waste as a supplementary cementitious material (SCM). Using SSA as aSCM increases the water demand and reduces the workability, compressive strength and density of concrete mixes,although these adverse effects may be controllled by modifying the mix design. This represents a beneficial reuseapplication for a waste that is typically landfilled. However the use of SSA in cementitious materials must becarefully controlled because SSA varies significantly, depending on sludge production method and combustionconditions. Testing will therefore always be required to assess how a specific SSA behaves when incorporated incementitious materials.
Schaeffer N, Grimes SM, Cheeseman CR, 2016, Use of extraction chromatography in the recycling of critical metals from thin film Leach solutions, Inorganica Chimica Acta, Vol: 457, Pages: 53-58, ISSN: 1873-3255
Phosphors and optoelectronic thin film electronic device layers contain critical metals including lanthanides and indium that should be recycled. Solvent impregnated resins (SIRs) containing (i) DEHPA (ii) DODGAA and (iii) DODGAA with the ionic liquid [C4mim][Tf2N] are investigated in extraction chromatography methodologies to recover and separate critical metals from dilute solutions that model those leached from thin films. Optimum adsorption of metals occurs at pH 1.5-3.5 but is highest on DODGAA-[C4mim][Tf2N]. The recovery and separation of adsorbed metal species on the DODGAA-[C4mim][Tf2N] SIR resin from solutions containing the glass matrix ions, Ca(II) and Al(III), along with In(III) and Sn(IV) or lanthanide ions is achieved by elution with HNO3. Ca(II) and Al(III) are completely eluted with 0.1M HNO3 retaining the target critical metal species on the resin. Separation of In from Sn is achieved by elution of In(III) with 2.5M HNO3 and Sn(IV) with 5M acid. La is separated from the other lanthanides by elution of La(III) with 2.5M HNO3 and the remaining lanthanides with 5M acid. The SIR resins can be reused over a series of at least five cycles of loading,stripping, and rinsing to reduce reagent costs and achieve economic critical metal recovery byextraction chromatography.
Soh WM, Tan J, Heng JYY, et al., 2016, Production of cenospheres from coal fly ash through vertical thermal flame (VTF) process, 4th Asia Conference on Mechanical and Materials Engineering, Publisher: Trans Tech Publications, Pages: 7-10, ISSN: 0255-5476
Coal fly ash is a complex mixture of anthropogenic materials produced during the combustion of pulverised coal in coal fired power plants. They pose environmental concerns that lead to air and water pollution. Effort has been done to reduce the production of coal fly ash or to extract potentially valuable products from coal fly ash, such as cenospheres. Cenospheres are light, low density, thin-walled hollow ceramic microsphere with unique properties. Conventional cenosphere production methods involve the separation of cenospheres from coal fly ash. Due to its small quantities in fly ash (1 % wt.), separation process results in low production of cenospheres. In this work, an attempt by applying a vertical thermal flame (VTF) process is done to produce cenospheres from coal fly ash. Particle size of coal fly ash 63 to 90 μm and 90 to 126 μm are selected to undergo the VTF process. Effect of size of precursor, number of passes through the thermal process, density, morphology and particles size of generated spheres are evaluated. The results show that different sizes of coal fly ash and number of passes through the VTF process affect the morphology of obtained spheres and the overall real density. Further optimization of the VTF process design in terms of heat source and the feeding mechanism are required to increase the transformation of coal fly ash to cenospheres.
Jia Y, Wang B, Wu Z, et al., 2016, Role of sodium hexametaphosphate in MgO/SiO2 cement pastes, Cement and Concrete Research, Vol: 89, Pages: 63-71, ISSN: 0008-8846
The extent of reaction between magnesium oxide (MgO) and silica fume (SiO2) is normally limited and mixes require high water contents to give suitable rheology. The use of considerably lower water contents and the formation of magnesium silicate hydrate (M-S-H) gel as a binding phase is made possible by adding sodium hexametaphosphate (Na-HMP) to the mix water prior to the addition of MgO and SiO2. This results in the formation of extensive reaction products and cured samples with high compressive strength and low porosity. In this work, the effect of Na-HMP on the hydration of MgO/SiO2 mixes is investigated using high water to solids ratio samples to allow monitoring of pH and the solution chemistry during hydration. It is shown that a relatively small amount of Na-HMP inhibits the formation of Mg(OH)2 when MgO is hydrolyzed. It is proposed that this is due to adsorption of phosphate species on the MgO which inhibits the nucleation of the Mg(OH)2. This gives rise to high Mg2 + species in solution and elevated pH (> 12) conditions relative to when Mg(OH)2 forms. In contrast, the phosphate does not suppress formation of M-S-H gel. In combination with the enhanced dissolution rate of SiO2 at high pH, M-S-H gel can form quickly without competition for Mg2 + ions by Mg(OH)2 precipitation. Incorporating the optimum concentration of Na-HMP into the mix water therefore transforms the properties of cement paste and mortar samples formed by reacting MgO and SiO2.
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