Title: Synthesis of high-purity precipitated calcium carbonate during the process of recovery of elemental sulphur from gypsum waste
Authors: De Beer, M; Doucet, FJ; Maree, JP; Liebenberg, L
Abstract: We recently showed that the production of elemental sulphur and calcium carbonate (CaCO3) from gypsum waste by thermally reducing the waste into calcium sulphide (CaS) followed by its direct aqueous carbonation yielded low-grade carbonate products (i.e. 99 mass% as CaCO3) or precipitated calcium carbonate (PCC). The process used an acid gas (H2S) to improve the aqueous dissolution of CaS, which is otherwise poorly soluble. The carbonate product was primarily calcite (99.5%) with traces of quartz (0.5%). Calcite was the only CaCO3 polymorph obtained; no vaterite or aragonite was detected. The product was made up of micron-size particles, which were further characterised by XRD, TGA, SEM, BET and true density. Results showed that about 0.37 ton of high-grade PCC can be produced from 1.0 ton of gypsum waste, and generates about 0.19 ton of residue, a reduction of 80% from original waste gypsum mass to mass of residue that needs to be discarded off. The use of gypsum waste as primary material in replacement of mined limestone for the production of PPC could alleviate waste disposal problems, along with converting significant volumes of waste materials into marketable commodities.
Description: Copyright: 2016 Elsevier. Due to copyright restrictions, the attached PDF file only contains the abstract of the full text item. For access to the full text item, please consult the publisher's website. The definitive version of the work is published in the Waste Management, vol. 46, pp 619-627
Synthesis of high-purity precipitated calcium carbonate during the process of recovery of elemental sulphur from gypsum waste
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Efficiency of ball milled South African bentonite clay for remediation of acid mine drainage
Title: Efficiency of ball milled South African bentonite clay for remediation of acid mine drainage
Authors: Masindi, V; Gitari, MW; Tutu, H; De Beer, M
Abstract: The feasibility of using vibratory ball milled South African bentonite clay for neutralization and attenuation of inorganic contaminants from acidic and metalliferous mine effluents has been evaluated. Treatment of acid mine drainage (AMD) with bentonite clay was done using batch laboratory assays. Parameters optimized included contact time, adsorbent dosage and adsorbate concentration. Ball milled bentonite clay was mixed with simulated AMD at specific solid: liquid (S/L) ratios and equilibrated on a table shaker. Contact of AMD with bentonite clay led to an increase in pH and a significant reduction inconcentrations of metal species. At constant agitation time of 30 min, the pH increased with the increase in dosage of bentonite clay. Removal of Mn(sup2+), Al(sup3+), and Fe(sup3+)was greatest after 30 min of agitation. The adsorption affinity obeyed the sequence: SO(sub4)(sup2-)(221.8 mg g(sup-1) > Mn (30.7 mg g(sup-1) > Al (30.5 mg g(sup-1) > Fe(30.2 mg g(sup-1). The pH of reacted AMD ranged from ˜3 to 6. Bentonite clay showed high adsorption capacities for Al and Fe at concentration 50%. Adsorption kinetics revealed that the suitable kinetic model describing data was pseudo-second-order hence confirming chemisorption. Adsorption isotherms indicated that removal of metals fitted the Langmuir adsorption isotherm for Fe and sulphate and the Freundlich adsorption isotherm for Al and Mn, respectively. Ball-milled bentonite clay showed an excellent capacity in neutralizing acidity and lowering the levels of inorganic contaminants in acidic mine effluents.
Description: Copyright: 2015 Elsevier. Due to copyright restrictions, the attached PDF file only contains the abstract of the full text item. For access to the full text item, please consult the publisher's website. The definitive version of the work is published in the Journal of Water process Engineering, Volume 8, pp 227-240.
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Bilge dump detection from SAR imagery using local binary patterns
Title: Bilge dump detection from SAR imagery using local binary patterns
Authors: Mdakane, LW; Kleynhans, W; Schwegmann, CP
Abstract: Accidental or deliberate bilge dumping presents a major threat to the sea ecosystem. We present a semi automatic approach to detect bilge dumping in synthetic aperture radar (SAR) images. The approach consist of three main parts. Firstly, areas with high probability of being bilge dumps are detected using Local Binary Patterns (LBP) with an adaptive threshold. Secondly, features are extracted from the detected dark spots and lastly, the features are analysed using bilge dump database to discriminate dark spot as bilge or not bilge. The automated approach was investigated on nine visually inspected images of SENTINEL 1A and ENVISAT Advanced Synthetic Aperture Radar (ASAR) images. The performance was measured by comparing the number of detected bilge dumps using the automated approach with the visually detected database. The automated detection approach showed to be a good alternative of the labour intensive manual inspection of bilge dumps, particularly for large ocean area monitoring.
Description: IGARSS 2015: Remote Sensing: Understanding the Earth for a Safer World, Milan, Italy, 26-31 July 2015. Due to copyright restrictions, the attached PDF file only contains the abstract of the full text item. For access to the full text item, please consult the publisher's website
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Removal of arsenic from wastewaters by cryptocrystalline magnesite: complimenting experimental results with modelling
Title: Removal of arsenic from wastewaters by cryptocrystalline magnesite: complimenting experimental results with modelling
Authors: Masindi, V; Mugera Gitari, W
Abstract: Availability of arsenic in waterbodies has posed devastating impacts to terrestrial and aquatic organisms. As such, prudent and pragmatic technologies need to be developed to troubleshoot and solve the problem of arsenic in aquatic ecosystems. This study was designed to investigate the potential use of cryptocrystalline magnesite for removal of arsenic from aqueous solution. Removal of arsenic was done in batch laboratory procedures. Parameters optimized include: Contact time, adsorbent dosage, arsenic concentration and supernatant pH. Modelling was applied to complement experimental results. Experimental results revealed that the optimum conditions for removal of arsenic are 15 min of agitation, 1 g of dosage, 20 mg L(sup-1) of arsenic concentration. Contact of magnesite with aqueous solution led to an increase in pH (pH > 10) which is suitable for removal of arsenic as an oxyanion. PH redox equilibrium (in C language) (PHREEQC) indicated that arsenic existed as an oxyanion at alkaline medium. It also predicted that arsenic is adsorbed by magnesite and precipitate out of solution as Mg(sub3)(AsO(sub4))(sub2)·4H(sub2)O. Adsorption isotherms fitted well to Freundlich adsorption isotherms than Langmuir adsorption isotherm hence proving multisite adsorption. Adsorption kinetic fitted well to pseudo-second-order kinetic hence proving that chemisorption is the rate limiting step. Magnesite has attenuated the concentration of arsenic to below prescribed water quality guidelines. This comparative study proved that magnesite can be used as an adsorbent with higher adsorption capacity for removal of arsenic in contaminated waterbodies. This novel technology will go a long way in curtailing the impacts of arsenic in contaminated waterbodies emanating from industrial activities
Description: Copyright: 2016 Elsevier. The attached PDF file only contains the abstract of the full text item. For access to the full text item, please consult the publisher's website. The definitive version of the work is published in the Journal of Cleaner Production, Vol. 113, pp 318-324
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A novel technology for neutralizing acidity and attenuating toxic chemical species from acid mine drainage using cryptocrystalline magnesite tailings
Title: A novel technology for neutralizing acidity and attenuating toxic chemical species from acid mine drainage using cryptocrystalline magnesite tailings
Authors: Masindi, V
Abstract: The present study was developed with the aim of beneficiating two waste materials by converting them into a resource. Magnesite tailings, which is the by-product of magnesite mining, was used to remediate acid mine drainage (AMD) which is the by-product of gold mining. This will go a long way in minimizing the use of virgin resources and thus fostering the process of sustainable development. AMD was reacted with magnesite tailings at an optimum equilibration time of 30 min and 1 g of magnesite tailings dosage. Contact of AMD with magnesite tailings led to an increase in pH (pH > 10) and a drastic reduction in inorganic contaminants (>99%), except for sulphate that achieved >80% for sulphate removal efficiency. Kinetic studies showed that ·adsorption of chemical species by magnesite tailings fitted well to pseudo-second-order adsorption kinetics hence confirming chemisorption. Pore diffusion was also determined to be one of the principal mechanisms acting as a major rate governing step. Ph Redox Equilibria (PHREEQC, in C language) geochemical modelling predicted that Fe removed as Fe(OH)3,goethite (FeOOH), and jarosite (KFe3(SO4)2(OH)6), Al as basaluminite (Al4(SO4)(OH)10·5(H2O)), boehmite (AlO(OH)), jurbanite (AlSO4(OH)·5H2O, and Al(OH)3 as gibbsite and diaspore. Al and Fe also precipitatedas iron (oxy)-hydroxides and aluminium (oxy)-hydroxides. Mn precipitated as rhodochrosite (MnCO3) and manganite (MnOOH). Ca was removed as gypsum (CaSO4·2H2O) and dolomite (CaMg(CO3)2). Sulphate was removed as gypsum and Fe, Al hydroxyl sulphate minerals. Mg was removed as brucite(Mg(OH)2) and dolomite (CaMg(CO3)2). This would explain the reduction in the chemical species con-tents in the treated water. Based on the above, it was concluded that magnesite tailings can neutralize and attenuate elevated concentrations of chemical species in AMD to within prescribed legal frameworks for water use in agricultural and industrial sectors in South Africa.
Description: Copyright: 2016 Elsevier. Due to copyright restrictions, the attached PDF file only contains the abstract of the full text item. For access to the full text item, please consult the publisher's website. The definitive version of the work is published in the Journal of Water Process Engineering, Vol. 10, pp 67-77
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Synthesis of cryptocrystalline magnesite–bentonite clay composite and its application for neutralization and attenuation of inorganic contaminants in acidic and metalliferous mine drainage
Title: Synthesis of cryptocrystalline magnesite–bentonite clay composite and its application for neutralization and attenuation of inorganic contaminants in acidic and metalliferous mine drainage
Authors: Masindi, V; Gitari, MW; Tutu, H; De Beer, M
Abstract: The primary aim of this study was to synthesize cryptocrystalline magnesite–bentonite clay composite by mechanochemical activation and evaluate its usability as low cost adsorbent for neutralization and attenuation of inorganic contaminants in acidic and metalliferous mine drainage. The composite was synthesized at 1:1 weight to weight ratio. The capacity of the composite to neutralize acidity and remove toxic chemical species from synthetic and field AMD was evaluated at optimized conditions. Interaction of the composite with AMD led to an increase in pH (pH > 11) and lowering of metal concentrations. The removal of chemical species was optimum at 20 min of equilibration and 1 g of dosage. The composite removed ≈99% (Al3+, Fe3+, and Mn2+) and ≈90% (SO4 2−) from raw mine effluent. Adsorption kinetics fitted better to pseudo-second-order kinetic than pseudo-first-order kinetic hence confirming chemisorption. Adsorption data fitted better to Freundlich adsorption isotherm than Langmuir hence confirming multisite adsorption. Gibbs free energy model predicted that the reaction is spontaneous in nature for Al, Fe and sulphate except for Mn. Geochemical model indicated that Fe was removed as Fe(OH)3, goethite, and jarosite, Al as basaluminite, boehmite and jurbanite, Al(OH)3 and as gibbsite and diaspore. Al and Fe precipitated as iron (oxy)-hydroxides and aluminium (oxy)-hydroxides. Mn precipitated as rhodochrosite and manganite. Ca was removed as gypsum. Sulphate was removed as gypsum, and Fe, Al hydroxyl sulphate minerals. Mg was removed as brucite and dolomite. It was concluded that the composite has the potential to neutralize acidity and attenuate potentially toxic chemical species from acidic and metalliferous mine drainage.
Description: Copyright: 2015 Elsevier. Due to copyright restrictions, the attached PDF file only contains the abstract of the full text item. For access to the full text item, please consult the publisher's website. The definitive version of the work is published in the Journal of Water Process Engineering, 2015, doi.org/10.1016/j.jwpe.2015.11.007
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Synthesis of porous magnesite-bentonite clay composite and its application for neutralisation and attenuation of inorganic contaminants in acidic and metalliferous mine drainage
Title: Synthesis of porous magnesite-bentonite clay composite and its application for neutralisation and attenuation of inorganic contaminants in acidic and metalliferous mine drainage
Authors: Masindi, V; Mugera, GW; Hlanganani, T; De Beer, M
Abstract: This paper evaluated the application of cryptocrystalline magnesite-bentonite clay composite for treatment of acid mine drainage (AMD). Bench laboratory studies were used to evaluate the treatment of AMD.
Description: 5th International Conference on Environment (ICENV 2015), Penang, Malaysia, 18-19 August 2015. Due to copyright restrictions, the attached PDF file only contains the abstract of the full text item. For access to the full text item, please consult the publisher's website.
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Co-operative good practice guide in the waste recycling sector: A guideline for co-operatives by co-operatives
Title: Co-operative good practice guide in the waste recycling sector: A guideline for co-operatives by co-operatives
Authors: Strydom, W; Godfrey, L
Abstract: For as long as South Africa continues to generate “waste”, that waste has value, and while there are businesses prepared to buy the waste, we will continue to find formal and informal collectors of recyclables. “There will always be work, the market exists, rubbish will not go away…” The types and quantities of waste generated in the larger towns and cities of South Africa has created opportunities for people to earn a living through the collection of recyclables, salvaging paper, plastic, glass or tins from waste bins at kerbside or from landfill sites. As a means of stimulating job creation in the formal waste economy, these collectors of recyclables are often advised by government or other stakeholders, to group together and register as a co-operative. This grouping of people into a co-operative is intended to provide several benefits which individuals would not be able to achieve on their own. While the co-operative model provides invaluable benefits to members, employees and communities, when implemented incorrectly it can result in opportunistic registrations in order to access funding; exploitation of co-operative members by corrupt individuals who are more informed of the current systems; conflict between co-operative members who have no previous association; and an overdependence on support which is difficult to outgrow to form sustainable businesses.
Description: Copyright 2016 CSIR.
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The consideration of non-anthropogenic emissions for air quality modelling in South Africa
Title: The consideration of non-anthropogenic emissions for air quality modelling in South Africa
Authors: Naidoo, M; Piketh, S
Abstract: Air quality modelling requires the identification of all relevant sources of emissions and the accurate calculation of the emissions rates. Many of these sources include anthropogenic activities that need to be accounted for in any emissions inventory to appraise their impact on air quality. Frequently the anthropogenic sources are the easiest to control through various emissions mitigation strategies. However emissions from natural sources can also contribute significantly to air pollution levels and are thus just as important to quantify to avoid underestimation in air quality in simulations. Biomass burning plays a key role in southern Africa's environmental concerns (highlighted by both the Southern African Regional Science Initiative field campaigns, SAFARI¿92 and SAFARI2000) as it is associated with land-cover change as well as the release of pollutants into the atmosphere within a relatively short period of time. Biomass burning emissions inclusion in any air quality modelling over southern Africa is necessary. Biogenic emissions can be considered as just as important, especially, if chemical transformation modelling is required. Biogenic Volatile Organic Carbon (BVOC) emissions as well as NOx from the soil may contribute significantly (depending on vegetation and soil types) within a model domain. Together, biomass burning and biogenic emissions establish a baseline emissions inventory onto which anthropogenic emissions can be added. This paper provides a description of various models and data sources for deriving model ready emissions inventories for biomass burning and biogenic emissions. The results from these models are also presented and discussed.
Description: 2015 National Association for Clean Air Conference, President Hotel, Bloemfontein, Free State, 1 - 2 October 2015. Due to copyright restrictions, the attached PDF file only contains the abstract of the full text item. For access to the full text item, please consult the publisher's website
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Recycling of post-consumer waste in South Africa: Prospects for growth
Title: Recycling of post-consumer waste in South Africa: Prospects for growth
Authors: Oelofse, SHH; Godfrey, L; Nahman, A; Strydom, WF
Abstract: Recent statistics on recycling of post-consumer packaging suggest that South Africa recycled 50.5% of all post-consumer packaging waste in 2012 (BMI, 2013). As with most developing countries, these encouraging recycling figures would not have been achieved without an active informal sector (DST, 2013; Wilson et al., 2013, SAPRO, 2014). An estimated 70-90% of packaging waste recycled in South Africa, is sourced by the informal sector (BMI, 2013), while only 3.3% of urban households are reported to recycle a fair amount of recyclables on a regular basis (Strydom, 2012). This conference poster explains the recycling of post-consumer waste in South Africa: Prospects for growth.
Description: 22nd Waste Management Conference and Exhibition, Somerset West, Western Cape, South Africa, 6-10 October 2014
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Composition and Value of waste in landfills in SA
Title: Composition and Value of waste in landfills in SA
Authors: Oelofse, SHH
Abstract: This paper presents the presentation on Composition and Value of waste in landfills in SA.
Description: IFAT Environmental Technology Forum, NASREC, Johannesburg, 16 September 2015
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The formal South African Waste Sector: Its contribution to the economy, employment and innovation
Title: The formal South African Waste Sector: Its contribution to the economy, employment and innovation
Authors: Godfrey, L; Strydom, W; Muswema, A; Oelofse, S; Roman, H; Mange, M
Abstract: The South African waste sector survey for 2012 was undertaken by the CSIR on behalf of the Department of Science and Technology (DST), and provides a good understanding of the ‘core’ of the formal waste sector (waste companies), and insight into the peripheral sector players. The aim of the survey has been to establish a baseline of the sector from which growth can be monitored and which will inform future investment in waste R&D, innovation and HCD. The focus of the survey has been on organisational information (employment, skills, financial size, innovation activity, etc.) and has not addressed quantities of waste. This report present the conference poster on the formal South African Waste Sector: Its contribution to the economy, employment and innovation.
Description: 22nd Waste Management Conference and Exhibition, Somerset west, Western Cape, South Africa, 6-10October 2014
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Waste characterisation, determining the energy potential of waste
Title: Waste characterisation, determining the energy potential of waste
Authors: Oelofse, SHH
Abstract: The presentation on waste characterisation, determining the energy potential of waste.
Description: IWMSA Seminar, Midrand, 25 November 2015
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Food waste in South Africa: Opportunities and challenges
Title: Food waste in South Africa: Opportunities and challenges
Authors: Oelofse, S
Abstract: This presentation presents on the food waste in South Africa: Opportunities and challenges, Food loss by region and stage of the supply chain and estimated food waste.
Description: Copyright: 2015 CSIR
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In vitro screening for endocrine disruptive activity in selected South African harbours and river mouths
Title: In vitro screening for endocrine disruptive activity in selected South African harbours and river mouths
Authors: Truter, JC; van Wyk, JH; Newman, BK
Abstract: Various waterborne anthropogenic contaminants disrupt the endocrine systems of wildlife and humans, targeting reproductive pathways, among others. Very little is known, however, regarding the occurrence of endocrine disruptive activity in South African freshwater ecosystems, and coastal ecosystems have not been studied in this regard. In a first attempt to investigate endocrine disruptive activity in South African coastal waters, surface water samples collected from harbours, river mouths and estuaries in three metropolitan municipalities, eThekwini (which includes Durban), Nelson Mandela (specifically Port Elizabeth Harbour) and City of Cape Town, were screened for (anti) oestrogenicity and (anti)androgenicity using recombinant yeast bioassays. Moreover, levels of the female hormone 17ß-(o)estradiol (E2) were determined in all samples, as well as a selection of hydrocarbons in the eThekwini samples. A high proportion of samples collected from eThekwini were oestrogenic, whereas none from Port Elizabeth Harbour and only a single river mouth sampled in the City of Cape Town were oestrogenic. E2 was detected in all the samples tested, but at higher concentrations at the eThekwini and City of Cape Town localities than Port Elizabeth Harbour. In addition, the recombinant yeast assays revealed that anti-androgenicity was widespread, being detected in the majority of samples screened apart from those representing Port Elizabeth Harbour. Conversely, no anti-oestrogenic or androgenic activity was detected. Anti-androgenicity did not associate with hydrocarbon loads, providing evidence that other anti-androgens were responsible for the observed activity. The present data suggest potential reproductive disruption in marine and estuarine fauna inhabiting the eThekwini and City of Cape Town regions.
Description: Copyright: 2015 National Inquiry Services Centre (NISC). Due to copyright restrictions, the attached PDF file only contains the abstract of the full text item. For access to the full text item, please consult the publisher's website. The definitive version of the work is published in African Journal of Marine Science, vol, 37(4), p.p. 567-574
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Research: CSIR model to provide support to municipalities for household waste recycling
Title: Research: CSIR model to provide support to municipalities for household waste recycling
Authors: Nahman, A
Abstract: This article is about the CSIR model to provide support to municipalities for household waste recycling.
Description: Copyright: 2016 Department of Environmental Affairs.
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Towards tradable permits for filamentous green algae pollution
Title: Towards tradable permits for filamentous green algae pollution
Authors: De Lange, WJ; Botha, AM; Oberholster, PJ
Abstract: Water pollution permit systems are challenging to design and implement. Operational systems that has maintained functionality remains few and far between, particularly in developing countries. We present current progress towards developing such a system for nutrient enrichment based water pollution, mainly from commercial agriculture. We applied a production function approach to first estimate the monetary value of the impact of the pollution, which is then used as reference point for establishing a reserve price for pollution permits. The subsequent market making process is explained according to five steps including permit design, terms, conditions and transactional protocol, the monitoring system, piloting and implementation. The monetary value of the impact of pollution was estimated between R1887 and R2890 per hectare per year, which not only provide a “management budget” for filamentous green algae mitigation strategies in the study area, but also enabled the calculation of a reserve price for filamentous green algae pollution permits, which was estimated between R2.25 and R111 per gram algae and R8.99 per gram at the preferred state.
Description: Copyright: 2016 Elsevier. This is a pre-print version. The definitive version of the work is published in the Journal of Environmental Management, 179, pp21-30
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Discussion of surface water and groundwater interaction in the Upper Crocodile River Basin, Johannesburg, South Africa: environmental isotope approach by Abiye et al.
Title: Discussion of surface water and groundwater interaction in the Upper Crocodile River Basin, Johannesburg, South Africa: environmental isotope approach by Abiye et al.
Authors: Hobbs, PJ
Abstract: The water resources downstream of the West Rand Gold Field (a.k.a. the Western Basin) have been the subject of considerable interest and discussion in both the media (e.g. Béga, 2010; 2012a; 2012b; 2013; Groenewald, 2010; Jordan, 2015; Kings, 2015) and scientific literature. At the root hereof is concern for the impact of acid mine drainage (AMD) on the receiving water resources environment shared in part by the Cradle of Humankind World Heritage Site (COH WHS), South Africa. Attention that is so acutely focussed on a sensitive environment of outstanding universal value (OUV) such as the COH property requires scientific reporting that is rigorous and devoid of sentiment and emotion. The contribution by Abiye et al. (2015) to this discourse suffers from similar flaws as have plagued earlier scientific literature (e.g. Abiye, 2011; Abiye et al., 2011; Abiye, 2014; Durand, 2012; Durand and Peinke, 2010; Durand et al., 2010) on the topic. Perhaps the most understandable (and excusable) of these is sentiment and emotion. Scientific contributions to the topic, however, can and must attract keen scrutiny from peers. Such scrutiny will necessarily extend to previous similar publications by the author(s). Against this background, serious misgivings are raised regarding various elements of the material presented by Abiye et al. (2015). These are set out and argued in this discussion.
Description: Copyright: 2016 Geological Society of South Africa
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The changing face of waste management – considerations when conducting a waste characterisation study
Title: The changing face of waste management – considerations when conducting a waste characterisation study
Authors: Oelofse, SHH; Muswema, A; Koen, R
Abstract: Changing the face of waste management in South Africa, includes waste diversion from landfill to alternative management options. There are a number of interventions to consider which may vary from very low tech, labour intensive solutions to extremely high tech, capital intensive technology options. Making an informed decision about the preferred technology choice will require a certain level of knowledge of the composition of the waste stream at hand. The level of detail that is required from the waste characterisation study will be determined by site specific conditions, and the level of change you want to achieve. In some instances, a mere screening exercise will do the trick, but if the envisaged change include high tech, capital intensive solutions, you may want to have a high level of confidence in the characteristics and volumes of waste that will be diverted to the particular solution in question. This paper will unpack the considerations to take into account when conducting or evaluating a waste characterisation study in support of changed waste management in South Africa.
Description: Proceedings of the 23rd WasteCon Conference, 17-21 October 2016, Emperors Palace, Johannesburg, South Africa
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Hydrothermal conversion of South African coal fly ash into pure phase Zeolite Na-P1
Title: Hydrothermal conversion of South African coal fly ash into pure phase Zeolite Na-P1
Authors: Gitari, MW; Petrik, LF; Musyoka, NM
Abstract: South African coal combustion power utilities generate huge amounts of coal fly ash that can be beneficiated into zeolitic products. This chapter reports on the optimization of the presynthesis and synthesis conditions for a pure-phase zeolite Na-P1 from selected South African coal fly ashes. The hydrothermal treatment time, temperature, and molar quantities of water during the hydrothermal treatment step were successfully optimized. The optimum hydrothermal treatment time and temperature were 48 h and 140°C, respectively. Pure-phase zeolite Na-P1 was obtained with a molar regime of 1 SiO(sub2):0.36 Al(sub2)O(sub3):0.59 NaOH:0.49 H(sub2)O at an aging temperature of 47°C for 48 h. The optimized conditions were applied to two fly ashes from two coa-L-fired power utilities, and high-purity zeolite Na-P1 was obtained. The third coal fly ash with a different chemical composition gave a low-quality Na-P1 under the optimized conditions. The cation exchange capacity for the high-purity zeolite phase was 4.11 mEq/g, indicating that the adjustment of reactant composition and presynthesis or synthesis parameters leads to yields of high-quality zeolite Na-P1. The results also show that conversion of the coal fly ash into high-purity zeolite also depends on the chemical and mineralogical composition of the coal fly ash.
Description: Copyright: INTECH, Rijeka, Croatia. Due to copyright restrictions, the attached PDF file only contains the abstract of the full text item. For access to the full text item, please consult the publisher's website.
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