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Valorization of apatite mining flotation residues by the manufacture of artificial aggregates

https://doi.org/10.1016/j.resconrec.2021.105605Get rights and content

Abstract

Mining residues are usually stockpiled because of their understudied physico-chemical properties and of their abundance, which make their valorization challenging. In this work, a cold-bonding granulation apparatus was built in order to transform a mining residue sludge from an apatite ore, into artificial aggregates suitable for use in civil engineering. A 25 rpm rotation speed, 15° angle relative to horizontal, and an ideal feeding amount of the granulation drum, as such as the liquid (supernatant) distribution method, were preliminary determined. Effects of rotation speed, liquid content, and granulation time were then studied to evaluate the best combination for appropriate aggregate size distribution. Box-Behnken experimental designs were used to investigate the evolution of compressive strength of the individual aggregates when Portland cement is added to the mix, and when granulation time varies, around the critical liquid content of 14% of total weight. Thus, the possible parameters combinations which allow a maximization of compressive strength without exclusively increasing cement content, were determined and used to confirm the Box-Behnken predictions. Spherical aggregates were thus manufactured, with diameters mainly comprised between 5 and 40 mm, and compressive strength comparable to those of commercialized aggregates, up to 7 MPa and to 3 MPa for aggregates with diameters respectively below and above 10 mm. Paths for greater consolidation as prior homogenization, use of humid cure conditions, and use of other additives emerge from literature and from the results presented.

Introduction

As a political interpretation of an increasing global concern about climate change, a series of reports have been submitted as soon as 1987 by the Brundtland Commission, until Agenda 2030 in which the latest 17 Sustainable Development Goals (SDGs) have been defined (Brundtland et al., 1987; United Nations, 2015). Because of their historical and actual large-scale impacts on ecosystems, human health, socio-economic systems, and because of their capital-intensive nature (Pimentel et al., 2016; Sonesson et al., 2016), the mining industries initiated the Mining, Minerals and Sustainable Development Project in 2002 (Starke, 2002). Ten years later, Buxton (2012) outlined that even if technical advances have been realized in water management and waste toxicity mitigation, the mining companies were insufficiently proactive concerning the challenges of integrated approaches for both land use and mineral production and consumption (Franks et al., 2011). However, they are the largest waste producers, discharging 65 billion tons annually in 2010, with fine particle processing waste representing 14 billion tons per year (Jones and Boger, 2012). A circular economy approach can help to address waste management issues subsequent to global decreasing ore grades and increasing amounts of tailings (Mudd, 2010), considering wastes as potential resources for other processes, while promoting inter-enterprise partnerships (Balanay and Halog, 2016; Preston, 2012). The need for the diversification of research projects in this field is justified by the observation that the misunderstanding of the mineralogical properties and of the behaviour of mining residues is a major factor in the lack of industrial-scale beneficiation (Lottermoser, 2011; Kinnunen and Kaksonen, 2019). Wastes from mining and metallurgical processes have been yet valorized as backfill, components for the manufacture of tiles, bricks or ceramics, glass or rock wool, soil amendments or cement and geopolymer components (Lottermoser, 2011; Pappu et al., 2007; Clifton et al., 1980; Safiuddin et al., 2010). Given the mineralogical composition and the aggregate size of these wastes (below 75 µm and with a median size between 10 and 20 µm), their reuse as filler (Choudhary et al., 2018; Modarres and Rahmanzadeh, 2014; Mistry and Roy, 2016; Kandhal, 1993) or as a clinker substitute for cement production components could be interesting (Snellings et al., 2012; Part et al., 2015; Rana et al., 2015; Paris et al., 2016). Recovery can also be induced by the transformation of fine waste particles into aggregates suitable for civil engineering, as it has been successfully performed with a large number of different wastes, mainly fly ash, vegetal husks, municipal solid waste incineration ash (MSWI ash), coal wastes, cement kiln dust and different types of sludge (Colangelo and Cioffi, 2013a; Baykal and Döven, 2000; Ferone et al., 2013; Vasugi and Ramamurthy, 2014).

Granulation is a size enlargement process which allows the formation of granular materials from fine powders, using liquid dispersion in fluidised beds, tumbling drums, discs or high shear granulators (Litster and Ennis, 2004). Several granulation methods exist to strengthen the physical structure of the aggregates, as cold-bonding pelletization with addition of lime and cement (Arslan and Baykal, 2006; Colangelo et al., 2015; Gesoğlu et al., 2007; Güneyisi et al., 2015), alkaline activators (Bui et al., 2012; Yliniemi et al., 2016) or foaming agents (Hwang and Tran, 2015). The main challenge in granulation process is to maximize the strength of the inter-particle bonds, formed by capillary pressure, viscous forces or surface tensions. Different growth regimes can qualify agglomeration processes within a granulation device but controlling factors for the performance of the aggregates are:

  • Binder and precursor properties as viscosity, size, specific surface and surface tension;

  • The proportions between all the materials introduced in the mix and the distribution method chosen;

  • Speed and intensity of the agitation for consolidation control.

The precursors, i.e. the materials composing the mix as wastes in the form of powder or sludge, dry or liquid binders, must have hydraulic or pozzolanic properties in order to create a solid matrix between the fine powder particles, by forming cementitious phases as calcium silicate hydrate (C-S-H) and calcium aluminate hydrate (C-A-H). Several factors that determine the reactivity of materials are:

  • (1)

    The amount of amorphous phases and selectively soluble SiO₂ and Al₂O₃ content, which is correlated to higher aggregates strength (Yliniemi et al., 2016; Snellings et al., 2012; Fernández-Jiménez and Palomo, 2003);

  • (2)

    Presence of a large number of nucleation sites thanks to material fineness and high specific surface (Toutanji et al., 2004; Bertos et al., 2004; Morone et al., 2014);

  • (3)

    C content must be limited below 6% to decrease water requirement and avoid mixture segregation and discoloration (Pedersen et al., 2008);

  • (4)

    Free MgO and free CaO contents must be examined to avoid volume expansion (Wang et al., 2010).

However, a large number of wastes required the addition of binders as lime, cement, fly ash, alkaline binders, geopolymers, or superplastifiers (Terzić et al., 2015; Yliniemi et al., 2017). Portland cement, well known as the main cohesive agent for concrete production can also be used as a preliminary binder for comprehension purposes in terms of mechanical consolidation, before substitution by other environmental-friendly binders. It consists in a mix of alite (3CaO.SiO2), belite (2CaO.SiO2), tricalcite aluminates (3CaO.Al2O3), tetracalcic aluminoferrites (4Cao.Al2O3.Fe2O3), and gypsum. After hydration, the main cohesive products are C-S-H, as well as aluminium and calcium hydroxides (Kosmatka et al., 2004).

Limiting factors for the addition of binders are the cost, and the environmental impact and management implied by their introduction. The interesting properties to define the quality of the aggregates mainly refer to aggregate size repartition, size and shape of the aggregates, bulk density, porosity and chemical content of organic matter and iron oxide (Canadian Standards Association, 2014). Some studies have shown that cold-bonded aggregates are suitable for use in concrete (Baykal and Döven, 2000; Tang et al., 2017; Ferone et al., 2013; Colangelo et al., 2015), exhibiting sufficient crushing strength values and good adhesion with the matrix of concrete or mortar specimens.

The work described here explores the possibilities of recycling 5.5 Mt/year of a flotation residue from an apatite ore, forecasted to be exploited for phosphate valorization in Sept-Îles (QC, Canada), during a period of time of 31 years (Roche-Itée, 2012). These processing wastes are currently intended to be disposed as tailings. However, this study focuses on the development of a cold-bonding granulation process to change the mining residues into valuable aggregates for civil engineering, this method being chosen because it is a cost and energy-effective solution for processing large amounts of materials. The regional context differs from the other tailings valorization projects currently undergone in Québec province, because it is located in a remote area, but in a key region for the transportation of goods, particularly from natural resources industries.

However, these waste differ from the alkaline materials (mostly ashes and slags) that are commonly studied for reuse purposes, or submitted to granulation process, both by their chemical composition and by their conditioning state (Gomes et al., 2016). In fact, preliminary flotation implies the use of surfactants that could affect the mineral surfaces and their ability to form interparticle bonds. When similar solid waste are used, there are combined with alkali activators to form geopolymers, which cost and long-term environmental impacts are not yet proven to be beneficial (Singh and Singh, 2019; Bouguermouh et al., 2018), or solidified and stabilised with higher binder proportions (Mesci et al., 2009). It is also current that the ore tailings are transformed into ceramics, but this implies sintering and completely modifies the mineralogy of the initial waste (Mymrin et al., 2020; Kinnunen et al., 2018; Matinde et al., 2018).

After characterization of the initial mining residues, the development of the granulation method for this apatite processing waste is detailed, emphasizing the influence of the experimental parameters on the consolidation of the aggregates. The second part of the results focuses on granulation with Portland cement, and on the variation of the humidity content for granulation. An experimental design using Box-Behnken Design (BBD) methodology is adopted to study in detail the differences on granulation behaviour around a critical humidity content. The last part of the work relates how the exploitation of the BBD results leads to the improvement of the aggregates quality.

Section snippets

Mining residues

The material used for granulation is a waste resulting from extraction and processing of an apatite ore, initially hosted in mafic layers, and essentially comprised of apatite, Fe and Ti oxides (magnetite and ilmenite), olivine, plagioclase and clinopyroxene (Tollari et al., 2008). After crushing, the magnetic fraction and the phosphate concentrate are respectively separated from the mineral matrix using low-intensity magnetic separation, and a flotation process operated with corn starch and

Characterization of the mining residues

Table 2 presents physical and chemical contents measured on the flotation residues, chemical contents expressed in terms of oxide contents. Si, Fe and Al are the predominant elements, but the relative CaO, SiO₂ and Al₂O₃ contents show the residues are different from waste commonly used, such as silica fume, fly ash or slag, particularly due to low Cao content and an unusual high Fe₂O₃ content (Lothenbach et al., 2011). XRD analyses, presented in Figure C of Appendix C, showed that the main

Conclusions

Aggregate size and mineralogy of Arnaud flotation residues make them suitable for production of aggregates by a cold-bonding granulation process, even if few pozzolanic or hydraulic activities has been noticed. Aggregate size distribution is appropriate for use in civil engineering as coarse aggregates, with diameter ranging between 5 and 40 mm. Addition of cement strengthens and sustains inter-particle bonds within the newly-formed aggregates. Within 45 min or 120 min, it is possible to

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

References (89)

  • M. Gesoğlu et al.

    Effects of fly ash properties on characteristics of cold-bonded fly ash lightweight aggregates

    Construction and Building Materials

    (2007)
  • H.I. Gomes et al.

    Alkaline residues and the environment: a review of impacts, management practices and opportunities

    Journal of Cleaner Production

    (2016)
  • B. Gonzalez-Corrochano et al.

    Production of lightweight aggregates from mining and industrial wastes

    J Environ Manage

    (2009)
  • E. Güneyisi et al.

    Utilization of cold bonded fly ash lightweight fine aggregates as a partial substitution of natural fine aggregate in self-compacting mortars

    Construction and Building Materials

    (2015)
  • P.J. Gunning et al.

    Production of lightweight aggregate from industrial waste and carbon dioxide

    Waste management

    (2009)
  • Y. Hiramatsu et al.

    Determination of the tensile strength of rock by a compression test of an irregular test piece

    International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts

    (1966)
  • C.-L. Hwang et al.

    A study of the properties of foamed lightweight aggregate for self-consolidating concrete

    Construction and Building Materials

    (2015)
  • S.M. Iveson et al.

    Nucleation, growth and breakage phenomena in agitated wet granulation processes: a review

    Powder technology

    (2001)
  • P. Kapur et al.

    Balling and granulation kinetics revisited

    International Journal of Mineral Processing

    (2003)
  • P. Kinnunen et al.

    Recycling mine tailings in chemically bonded ceramics–a review

    Journal of cleaner production

    (2018)
  • P.H.-M. Kinnunen et al.

    Towards circular economy in mining: Opportunities and bottlenecks for tailings valorization

    Journal of Cleaner Production

    (2019)
  • N.U. Kockal et al.

    Effects of lightweight fly ash aggregate properties on the behavior of lightweight concretes

    Journal of hazardous materials

    (2010)
  • P.K. Le et al.

    A microscopic study of granulation mechanisms and their effect on granule properties

    Powder technology

    (2011)
  • B. Lothenbach et al.

    Supplementary cementitious materials

    Cement and Concrete Research

    (2011)
  • J. Mellmann

    The transverse motion of solids in rotating cylinders—forms of motion and transition behavior

    Powder technology

    (2001)
  • R. Mistry et al.

    Effect of using fly ash as alternative filler in hot mix asphalt

    Perspectives in Science

    (2016)
  • A. Modarres et al.

    Application of coal waste powder as filler in hot mix asphalt

    Construction and Building Materials

    (2014)
  • M. Morone et al.

    Valorization of steel slag by a combined carbonation and granulation treatment

    Minerals Engineering

    (2014)
  • G.M. Mudd

    The environmental sustainability of mining in Australia: key mega-trends and looming constraints

    Resources Policy

    (2010)
  • A. Pappu et al.

    Solid wastes generation in India and their recycling potential in building materials

    Building and environment

    (2007)
  • J.M. Paris et al.

    A review of waste products utilized as supplements to Portland cement in concrete

    Journal of Cleaner Production

    (2016)
  • W.K. Part et al.

    An overview on the influence of various factors on the properties of geopolymer concrete derived from industrial by-products

    Construction and Building Materials

    (2015)
  • K.H. Pedersen et al.

    A review of the interference of carbon containing fly ash with air entrainment in concrete

    Progress in Energy and Combustion Science

    (2008)
  • B.S. Pimentel et al.

    Decision-support models for sustainable mining networks: Fundamentals and challenges

    Journal of Cleaner Production

    (2016)
  • A. Rana et al.

    Sustainable use of marble slurry in concrete

    Journal of Cleaner Production

    (2015)
  • K.V. Sastry et al.

    Investigation of the layering mechanism of agglomerate growth during drum pelletization

    Powder technology

    (2003)
  • I. Sims et al.

    16 - Concrete Aggregates

  • J. Singh et al.

    Geopolymerization of solid waste of non-ferrous metallurgy–a review

    Journal of environmental management

    (2019)
  • P. Tang et al.

    Employing cold bonded pelletization to produce lightweight aggregates from incineration fine bottom ash

    Journal of cleaner production

    (2017)
  • A. Terzić et al.

    Artificial fly ash based aggregates properties influence on lightweight concrete performances

    Ceramics international

    (2015)
  • N. Tollari et al.

    Trace element concentrations in apatites from the Sept-Îles Intrusive Suite, Canada — Implications for the genesis of nelsonites

    Chemical Geology

    (2008)
  • H. Toutanji et al.

    Effect of supplementary cementitious materials on the compressive strength and durability of short-term cured concrete

    Cement and Concrete Research

    (2004)
  • V. Vasugi et al.

    Identification of design parameters influencing manufacture and properties of cold-bonded pond ash aggregate

    Materials & Design (1980-2015)

    (2014)
  • G. Wang et al.

    Use of steel slag as a granular material: volume expansion prediction and usability criteria

    Journal of Hazardous Materials

    (2010)
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