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Dr. Oscar Jaime Restrepo Baena
Department of Materials and Minerals of the School of Mines, Universidad Nacional de Colombia, Bogotá D.C., Colombia

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Research Keywords & Expertise

0 Extractive Metallurgy
0 Materials Science
0 Mineral Processing
0 Sustainability in extractive process
0 Circular economy of minerals

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Circular economy of minerals

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Journal article
Published: 20 August 2021 in Sustainability
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The aim of this work is to explain the concepts of sustainability with respect to small artisanal gold mining. For this, a qualitative approach with a descriptive scope was used, for which the bibliographic review technique was conducted. In this sense, articles, theses, books and institutional documents, and any contribution related to the research topic were taken into consideration. Likewise, this documentation contributed to the delimiting aspects that allowed a contrast between the proposed definitions and small artisanal mining in the Northeast Antioquia region in Colombia. Based on the reviewed sources, different needs were recognized in artisanal small-scale gold mining in Northeast Antioquia that still need action. In conclusion, through the exposition of sustainability theories, three common factors were identified within the various positions that were raised—the environmental, economic, and sociocultural dimensions.

ACS Style

Óscar Jaime Restrepo Baena; Luis Enrique Martínez Mendoza. Sustainability of the Artisanal and Small-Scale Gold Mining in Northeast Antioquia-Colombia. Sustainability 2021, 13, 9345 .

AMA Style

Óscar Jaime Restrepo Baena, Luis Enrique Martínez Mendoza. Sustainability of the Artisanal and Small-Scale Gold Mining in Northeast Antioquia-Colombia. Sustainability. 2021; 13 (16):9345.

Chicago/Turabian Style

Óscar Jaime Restrepo Baena; Luis Enrique Martínez Mendoza. 2021. "Sustainability of the Artisanal and Small-Scale Gold Mining in Northeast Antioquia-Colombia." Sustainability 13, no. 16: 9345.

Journal article
Published: 28 July 2021 in Materiales de Construcción
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The substitution of the normalized aggregate by residual foundry sand (WFS) was studied on the physical properties of mortars by means of resistance to compression and capillary absorption tests. The aggregate was replaced by WFS in its natural state (WFS), washed residual foundry sand (WFSW) and heat treated residual foundry sand (WFST). The WFS had a percentage of bentonite, which was sought to be thermally activated. It was found that the physical behavior of the mortars containing WFS and WFSW was similar to that of the control sample. The clay recovered from the sand washing was evaluated for its pozzolanic potential, it was found that, with the thermal treatment, the montmorillonite acquires pozzolanic behavior. Mortars with WFST presented a drop in compressive strength. The pozzolanic effect achieved in the clay was not reflected in the compressive strength of the mortars with WFST.

ACS Style

B.A. Feijoo; J.I. Tobón; O.J. Restrepo-Baena. Substitution of aggregates by waste foundry sand: effects on physical properties of mortars. Materiales de Construcción 2021, 71, e251 -e251.

AMA Style

B.A. Feijoo, J.I. Tobón, O.J. Restrepo-Baena. Substitution of aggregates by waste foundry sand: effects on physical properties of mortars. Materiales de Construcción. 2021; 71 (343):e251-e251.

Chicago/Turabian Style

B.A. Feijoo; J.I. Tobón; O.J. Restrepo-Baena. 2021. "Substitution of aggregates by waste foundry sand: effects on physical properties of mortars." Materiales de Construcción 71, no. 343: e251-e251.

Journal article
Published: 31 May 2021 in Environmental Science & Policy
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Environmental remediation of polluted sites in developing communities often faces difficulties due to the misalignment of project objectives with the needs and interests of local communities, establishment of unrealistic expectations for the outcome of the project, and failure to account for the available resources in the community itself. Remediation decisions favor technical data and technical solutions as the main means of determining remediation options, requiring significant investment and local capacity that are often not found in developing communities. Often these systems fail to account for the social aspects in environmental management and remediation. In contrast, new approaches in local knowledge-based solutions focus on pre-existing environmental management initiatives to establish objectives that are meaningful to the community itself. “Positive deviance” – or the idea that there are solutions already in communities that are successful at addressing challenges despite the barriers that a community faces – are often overlooked during project design and implementation. Identifying examples of positive deviance and working with community members who are well versed in local challenges, available resources, and local capacity presents opportunities for community members to establish project objectives and provides the foundation for future environmental management projects in the area. We present a case study of artisanal and small-scale gold mining (ASGM) in the Andes municipality, Antioquia, Colombia and local initiatives to overcome community-identified environmental pollutants. Through a series of semi-structured interviews, surveys, and site visits, we identified community perception of environmental pollutants, management techniques for mining waste, and grassroots initiatives that were locally developed to address them. Through key communication and interaction between innovators with identified positive deviance projects, technical experts, and other miners facing similar challenges, innovative projects that account for the social, political, and economic realities of a developing community can become widespread, leading to improved environmental and social conditions.

ACS Style

Michelle Schwartz; Kathleen Smits; Jessica Smith; Thomas Phelan; Oscar Jaime Restrepo Baena. Incorporating positive deviance into comprehensive remediation projects: A case study from artisanal and small-scale gold mining in the municipality of Andes, Colombia. Environmental Science & Policy 2021, 123, 142 -150.

AMA Style

Michelle Schwartz, Kathleen Smits, Jessica Smith, Thomas Phelan, Oscar Jaime Restrepo Baena. Incorporating positive deviance into comprehensive remediation projects: A case study from artisanal and small-scale gold mining in the municipality of Andes, Colombia. Environmental Science & Policy. 2021; 123 ():142-150.

Chicago/Turabian Style

Michelle Schwartz; Kathleen Smits; Jessica Smith; Thomas Phelan; Oscar Jaime Restrepo Baena. 2021. "Incorporating positive deviance into comprehensive remediation projects: A case study from artisanal and small-scale gold mining in the municipality of Andes, Colombia." Environmental Science & Policy 123, no. : 142-150.

Journal article
Published: 30 December 2020 in Materiales de Construcción
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This work studies the effect of nanosilica (NS) on the rheology of cement paste by comparing it with two high specific surface area silicas: silica fume (SF) and pyrogenic silica (PS). Portland cement pastes were produced with different water-to-cementing material ratios and different solid substitutions of cement by silica. Water demand, setting time, and rheology tests were performed. Results showed that NS and SF decreased plastic viscosity, while PS increased it. Only PS was found to have an effect on yield stress. NS showed the most decreasing effect on viscosity, regardless of its higher water demand. It was concluded that the behavior of pastes containing NS and SF is governed by the “ball-bearing” effect from silica particles, by their agglomeration degree, and their impact on the solid volume fraction. The behavior of pastes containing PS is governed by its ability to absorb a portion of the mixing water.

ACS Style

J. I. Tobón; O. Mendoza; O. J. Restrepo; M. V. Borrachero; J. Payá. Effect of different high surface area silicas on the rheology of cement paste. Materiales de Construcción 2020, 70, 231 .

AMA Style

J. I. Tobón, O. Mendoza, O. J. Restrepo, M. V. Borrachero, J. Payá. Effect of different high surface area silicas on the rheology of cement paste. Materiales de Construcción. 2020; 70 (340):231.

Chicago/Turabian Style

J. I. Tobón; O. Mendoza; O. J. Restrepo; M. V. Borrachero; J. Payá. 2020. "Effect of different high surface area silicas on the rheology of cement paste." Materiales de Construcción 70, no. 340: 231.

Technical article
Published: 14 October 2020 in Mine Water and the Environment
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Several artisanal and small-scale gold mining (ASGM) sites in Colombia were located and sampled. At each ASGM site, tailings samples were collected and analyzed. Establishing rapport with mining stakeholders and analyzing the samples allowed our team to draw conclusions about the inefficiency of mercury-use in gold extraction and the superior efficiency of centrifugal and gravimetric methods for reprocessing the mining residues produced by artisanal gold miners.

ACS Style

Oscar Jaime Restrepo Baena; Gustavo Aristizábal; Mateo S. Pimentel; Cristian A. Flórez; Carlos E. Argumedo. Waste Management and the Elimination of Mercury in Tailings from Artisanal and Small-Scale Gold Mining in the Andes Municipality of Antioquia, Colombia. Mine Water and the Environment 2020, 40, 250 -256.

AMA Style

Oscar Jaime Restrepo Baena, Gustavo Aristizábal, Mateo S. Pimentel, Cristian A. Flórez, Carlos E. Argumedo. Waste Management and the Elimination of Mercury in Tailings from Artisanal and Small-Scale Gold Mining in the Andes Municipality of Antioquia, Colombia. Mine Water and the Environment. 2020; 40 (1):250-256.

Chicago/Turabian Style

Oscar Jaime Restrepo Baena; Gustavo Aristizábal; Mateo S. Pimentel; Cristian A. Flórez; Carlos E. Argumedo. 2020. "Waste Management and the Elimination of Mercury in Tailings from Artisanal and Small-Scale Gold Mining in the Andes Municipality of Antioquia, Colombia." Mine Water and the Environment 40, no. 1: 250-256.

Special issue article
Published: 30 July 2020 in International Journal of Applied Ceramic Technology
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The reuse and reincorporation of waste generated in the production processes are becoming increasingly important in the world, due to the double effect that it has in terms of sustainability. The first one is the environmental factor, since the impact generated is reduced by reducing the amount of wastes. The second one is the financial factor, since new products are developed that companies did not initially have, generating financial profitability. Therefore, this research evaluates the possible reuse of waste from gravel and sand wash mud of an aggregate plant as a Supplementary Cementitious Material (SCM) after being thermally activated, seeking to promote the circular economy in the construction materials sector. The physical, chemical and mineralogical characterization of the waste is presented and its pozzolanic activity was evaluated by means of the SAI‐Strength Activity Index. It was found that despite its low content of clay minerals, the thermally activated waste had very good performance as SCM with SAI between 81 and 106 with a tendency to increase with the age of cure. Showing that this can be a very promising potential use for this kind of waste.

ACS Style

Oscar Restrepo‐Baena; Francisco Cabrera‐Poloche; Jorge I. Tobón; Sergio Escudero‐Restrepo; Stephanie Álvarez‐Zuluaga. Valorization of waste from sand wash muds of an aggregates plant: Evaluation as a supplementary cementitious material. International Journal of Applied Ceramic Technology 2020, 17, 2669 -2680.

AMA Style

Oscar Restrepo‐Baena, Francisco Cabrera‐Poloche, Jorge I. Tobón, Sergio Escudero‐Restrepo, Stephanie Álvarez‐Zuluaga. Valorization of waste from sand wash muds of an aggregates plant: Evaluation as a supplementary cementitious material. International Journal of Applied Ceramic Technology. 2020; 17 (6):2669-2680.

Chicago/Turabian Style

Oscar Restrepo‐Baena; Francisco Cabrera‐Poloche; Jorge I. Tobón; Sergio Escudero‐Restrepo; Stephanie Álvarez‐Zuluaga. 2020. "Valorization of waste from sand wash muds of an aggregates plant: Evaluation as a supplementary cementitious material." International Journal of Applied Ceramic Technology 17, no. 6: 2669-2680.

Journal article
Published: 11 May 2020 in Resources Policy
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This paper identifies the intersecting technical and social factors that have fueled a history of conflict between artisanal and small-scale mining (ASM) and large-scale mining, and more recently, their potential coexistence, in Marmato, Colombia. At Marmato, a vertically zoned ore body and corresponding vertically stacked land claims have in part fueled tensions between ASM and large-scale mining. These same characteristics have also given rise to a scenario which could facilitate the coexistence of both parties. The case of Marmato has implications for policy and decision-making around relations between ASM and large-scale mining elsewhere, notably: 1) how a politicization of natural hazards can exacerbate existing asymmetries in power, wealth, and risk; 2) some deposit types such as epithermal veins may be particularly suited to coexistence, but site-specific characteristics determine whether the technically feasible mining methods could facilitate or preclude coexistence; 3) how equity is central to successful coexistence; and 4) how approaches such as contract mining will need to integrate social and technical considerations.

ACS Style

Elizabeth A. Holley; Nicole M. Smith; Jeison Alejandro Delgado Jimenez; Isabel Casasbuenas Cabezas; Oscar Jaime Restrepo-Baena. Socio-technical context of the interactions between large-scale and small-scale mining in Marmato, Colombia. Resources Policy 2020, 67, 101696 .

AMA Style

Elizabeth A. Holley, Nicole M. Smith, Jeison Alejandro Delgado Jimenez, Isabel Casasbuenas Cabezas, Oscar Jaime Restrepo-Baena. Socio-technical context of the interactions between large-scale and small-scale mining in Marmato, Colombia. Resources Policy. 2020; 67 ():101696.

Chicago/Turabian Style

Elizabeth A. Holley; Nicole M. Smith; Jeison Alejandro Delgado Jimenez; Isabel Casasbuenas Cabezas; Oscar Jaime Restrepo-Baena. 2020. "Socio-technical context of the interactions between large-scale and small-scale mining in Marmato, Colombia." Resources Policy 67, no. : 101696.

Journal article
Published: 23 March 2020 in Solid State Sciences
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The aim of this work is to find the effect of the cation M (Zn2+, Co2+, Cu2+, and Mg2+) on the optical properties of MFe2(P2O7)2 synthesized by solution combustion. The crystal structure of the powders was determined by X-ray diffraction (XRD), Infrared spectroscopy (IR), and Raman spectroscopy. The presence of Fe2+ and Fe3+ ions in the pigments was studied using Mössbauer spectroscopy (MS), these spectra showed at 298 K three well-defined Mössbauer doublets belonging to octahedral S1 site and S3 site of Fe3+ and trigonal prismatic S2 site of Fe2+, confirming the formation of ZnFe2(P2O7)2, CoFe2(P2O7)2 and MgFe2(P2O7)2 structures, while in CuFe2(P2O7)2 there is no presence of trigonal prismatic S2 site of Fe2+ ion. Therefore, the mechanism of color on the ZnFe2(P2O7)2, CoFe2(P2O7)2, and MgFe2(P2O7)2 structures are due to intervalence charge transfer between Fe2+ and Fe3+ ions. In contrast, on the CuFe2(P2O7)2 structure is due to d-d electronic transitions of the Cu2+ ion, these evidences can also be observed in their UV–Vis diffuse reflectance spectra. Moreover, the inorganic blue pigment MgFe2(P2O7)2, which is free of cobalt, copper, and zinc could be used as a pigment in applications of low temperatures.

ACS Style

E.A. Chavarriaga; A.A. Lopera; T.B. Wermuth; S. Arcaro; A. Gómez; Oscar Jaime Restrepo-Baena; J. Alarcón; C.P. Bergmann. Synthesis by solution combustion of inorganic blue pigments MFe2(P2O7)2: Influence of the cation M (Zn2+, Co2+, Cu2+, and Mg2+) on their optical properties. Solid State Sciences 2020, 103, 106180 .

AMA Style

E.A. Chavarriaga, A.A. Lopera, T.B. Wermuth, S. Arcaro, A. Gómez, Oscar Jaime Restrepo-Baena, J. Alarcón, C.P. Bergmann. Synthesis by solution combustion of inorganic blue pigments MFe2(P2O7)2: Influence of the cation M (Zn2+, Co2+, Cu2+, and Mg2+) on their optical properties. Solid State Sciences. 2020; 103 ():106180.

Chicago/Turabian Style

E.A. Chavarriaga; A.A. Lopera; T.B. Wermuth; S. Arcaro; A. Gómez; Oscar Jaime Restrepo-Baena; J. Alarcón; C.P. Bergmann. 2020. "Synthesis by solution combustion of inorganic blue pigments MFe2(P2O7)2: Influence of the cation M (Zn2+, Co2+, Cu2+, and Mg2+) on their optical properties." Solid State Sciences 103, no. : 106180.

Research article
Published: 13 March 2020 in ACS Omega
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The application of phosphonium-based ionic liquids (ILs) on the selective extraction of cobalt is presented. The extraction mechanism is established, and different parameters of the process are evaluated. It has been found that it is possible to extract cobalt from aqueous solutions in sulfate media, with the addition of sodium chloride, using phosphonium ILs. The cobalt extraction was selective with respect to nickel and strongly dependent on the chloride concentration in the aqueous solution. The cobalt extraction is given by an anion exchange mechanism through an endothermic process. Cobalt extractions greater than 98% were obtained using the proposed methods. Cobalt stripping from the loaded IL phase using water was proved. Therefore, an alternative extraction process to traditional organic solvents is proposed. This alternative has additional advantages such as easy handling, lower costs in reagents and equipment, and risk reduction.

ACS Style

Dairo E. Chaverra; Oscar Jaime Restrepo-Baena; María C. Ruiz. Cobalt Extraction from Sulfate/Chloride Media with Trioctyl(alkyl)phosphonium Chloride Ionic Liquids. ACS Omega 2020, 5, 5643 -5650.

AMA Style

Dairo E. Chaverra, Oscar Jaime Restrepo-Baena, María C. Ruiz. Cobalt Extraction from Sulfate/Chloride Media with Trioctyl(alkyl)phosphonium Chloride Ionic Liquids. ACS Omega. 2020; 5 (11):5643-5650.

Chicago/Turabian Style

Dairo E. Chaverra; Oscar Jaime Restrepo-Baena; María C. Ruiz. 2020. "Cobalt Extraction from Sulfate/Chloride Media with Trioctyl(alkyl)phosphonium Chloride Ionic Liquids." ACS Omega 5, no. 11: 5643-5650.

Discussion
Published: 19 December 2019 in The Extractive Industries and Society
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Using a creative capacity building (CCB) framework, co-design workshops among artisanal and small-scale gold miners, government officials, NGO representatives, and academics can provide an effective mechanism to identify pressing needs and desires of miners and operators towards formalization. As recently implemented in Peru, one of these workshops identified the need for a single forum (association) to allow artisanal and small-scale miners to represent their voice in front of government and large-scale mining operations and the need for a streamlined simple process for formalization that included mining, environment, health, safety, and employment considerations. A first step towards the single forum was taken with the creation of a social media outlet that allows participants to voice their concerns and share information. Future workshops are needed to cement the creation of the forum and provide specific recommendations for the streamlining of the formalization process.

ACS Style

Kathleen Smits; Libby McDonald; Nicole M. Smith; Fernando Gonzalez; Juan Lucena; Gerardo Martinez; Oscar Jaime Restrepo-Baena; Silvia Rosas. Voces Mineras: Clarifying the future of artisanal and small-scale mining collaborations. The Extractive Industries and Society 2019, 7, 68 -72.

AMA Style

Kathleen Smits, Libby McDonald, Nicole M. Smith, Fernando Gonzalez, Juan Lucena, Gerardo Martinez, Oscar Jaime Restrepo-Baena, Silvia Rosas. Voces Mineras: Clarifying the future of artisanal and small-scale mining collaborations. The Extractive Industries and Society. 2019; 7 (1):68-72.

Chicago/Turabian Style

Kathleen Smits; Libby McDonald; Nicole M. Smith; Fernando Gonzalez; Juan Lucena; Gerardo Martinez; Oscar Jaime Restrepo-Baena; Silvia Rosas. 2019. "Voces Mineras: Clarifying the future of artisanal and small-scale mining collaborations." The Extractive Industries and Society 7, no. 1: 68-72.

Journal article
Published: 25 May 2019 in Material Science Research India
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The Portland cement clinker consists of 95% calcium oxide, silicon, aluminium and iron and 5% impurities of magnesium, sodium, potassium, titanium, sulfur, phosphorus and manganese. From the combination of two or more of the main oxides, the constituents of the white clinker are formed, corresponding to alite(3CaO.SiO2 or C3S), belite (2CaO.SiO2 or C2S) and celite (Ca3Al2O6 or C3A), which give cement its characteristic properties. The fundamental properties of cement are its mechanical resistance, chemical resistance, the speed of reaction with water and the heat given off in hydration. In this work, the reactivity of an artificial mixture of white clinker, formed from alite, belite and celite prepared by flame spray pyrolysis was evaluated. The phases were characterized by X-ray diffraction, scanning electron microscopy and microcalorimetry, to evaluate their formation and reactivity. The characterization showed that during the synthesis of belite, a greater amount of the polymorph alpha was produced, with some impurities. On the other hand, the synthesis of celite allowed the production of the polymorph CII. The reactivity was evaluated by microcalorimetry.

ACS Style

Andrés Felipe Pinto; Jorge Iván Tobón; Natalia Betancur-Granados; Oscar Jaime Restrepo-Baena. Evaluation of the reactivity of artificial mixtures of Portland cement clinker obtained by flame spray pyrolysis. Material Science Research India 2019, 16, 110 -117.

AMA Style

Andrés Felipe Pinto, Jorge Iván Tobón, Natalia Betancur-Granados, Oscar Jaime Restrepo-Baena. Evaluation of the reactivity of artificial mixtures of Portland cement clinker obtained by flame spray pyrolysis. Material Science Research India. 2019; 16 (2):110-117.

Chicago/Turabian Style

Andrés Felipe Pinto; Jorge Iván Tobón; Natalia Betancur-Granados; Oscar Jaime Restrepo-Baena. 2019. "Evaluation of the reactivity of artificial mixtures of Portland cement clinker obtained by flame spray pyrolysis." Material Science Research India 16, no. 2: 110-117.

Journal article
Published: 23 April 2019 in Material Science Research India
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Cyanide is one of the most used reagents in the precious metal extraction process; as well as the most efficient from the point of view of the dissolution process, but it is also a toxic product that requires a lot of care in handling. Likewise, the residual solutions of the process must be followed because they can be a risk of contamination of water, animals and human health. In the artisanal processes of obtaining gold and silver, neutralization of the residual solutions is used to passivate the present cyanide. During this process ammonium cyanate is formed which decomposes rapidly in the presence of air and sunlight in carbon dioxide and ammonia gas, contributing to the greenhouse effect. In this work, the use of the ammonium cyanate obtained in the process of neutralization of the cyanide solutions as a reagent to obtain urea is proposed. Urea was obtained indirectly through the use of the reagent kit UREA/BUN-COLOR. The process is effective at pH ≤ 4.5 with a rapid increase in solution temperature and the addition of hydrogen peroxide. The urea crystals begin to form at 50°C. The cyanide/urea ratio obtained was 1/7.5.

ACS Style

Carlos Dario Lopez Ramirez; Dairo E. Chaverra; Oscar Jaime Restrepo Baena. Obtaining Urea from Effluents of Gold Cyanidation Process. Material Science Research India 2019, 16, 43 -47.

AMA Style

Carlos Dario Lopez Ramirez, Dairo E. Chaverra, Oscar Jaime Restrepo Baena. Obtaining Urea from Effluents of Gold Cyanidation Process. Material Science Research India. 2019; 16 (1):43-47.

Chicago/Turabian Style

Carlos Dario Lopez Ramirez; Dairo E. Chaverra; Oscar Jaime Restrepo Baena. 2019. "Obtaining Urea from Effluents of Gold Cyanidation Process." Material Science Research India 16, no. 1: 43-47.

Journal article
Published: 13 October 2018 in Ceramics International
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Synthesis of dicalcium silicate (2CaO.SiO2 or C2S) through flame spray pyrolysis and a solution combustion method was investigated by the variation of flames and fuels. The synthesized powders were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and scanning electron microscopy (SEM). X-ray diffraction analysis revealed the formation of dicalcium silicate polymorphs with presence of calcium oxide, calcium carbonates and amorphous materials as impurities. Results suggest that some flames and fuels favor the formation of calcite during the synthesis process due to an excess of carbon atoms in the combustion. Fourier transform infrared spectra of all samples showed the main silicates reflections located near to 500 cm−1 and 1000 cm−1 and scanning electron microscopy showed the formation of spherical agglomerates of nanoparticles in both methods. By these two alternative methods of synthesis it was possible to obtain C2S with nanometric particle size.

ACS Style

Natalia Betancur-Granados; Juan Camilo Restrepo; Jorge I. Tobón; Oscar Jaime Restrepo-Baena. Dicalcium silicate (2CaO·SiO2) synthesized through flame spray pyrolysis and solution combustion synthesis methods. Ceramics International 2018, 45, 9589 -9595.

AMA Style

Natalia Betancur-Granados, Juan Camilo Restrepo, Jorge I. Tobón, Oscar Jaime Restrepo-Baena. Dicalcium silicate (2CaO·SiO2) synthesized through flame spray pyrolysis and solution combustion synthesis methods. Ceramics International. 2018; 45 (7):9589-9595.

Chicago/Turabian Style

Natalia Betancur-Granados; Juan Camilo Restrepo; Jorge I. Tobón; Oscar Jaime Restrepo-Baena. 2018. "Dicalcium silicate (2CaO·SiO2) synthesized through flame spray pyrolysis and solution combustion synthesis methods." Ceramics International 45, no. 7: 9589-9595.

Journal article
Published: 01 October 2018 in Journal of Materials in Civil Engineering
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In this work, the effect of pyrogenic silica and nanosilica on the properties of portland cement matrices is compared. Two chemically and mineralogically similar mineral additions (amorphous silica) with different particle size and specific surface area were used to prepare pastes and mortars with different solids substitutions of cement by silica. These samples were used to measure water and superplasticizer demand, setting time, hydration kinetics, water absorption by capillary suction, and compressive strength. It was found that specific surface area, rather than particle size, played a crucial role in the amount of water and superplasticizer necessary to obtain a desired workability in pastes and mortars. Such water and superplasticizer demands had a delaying effect on the setting time and hydration kinetics of pastes. Nevertheless, compressive strength results at different curing ages of mortars were found to have a direct correlation with the porous structure of the matrix, rather than with the specific surface area of the silica particles. It was concluded that regardless of its higher specific surface area and greater effect on the fresh state properties of pastes, pyrogenic silica was less efficient than nanosilica to increase the compressive strength of mortars, being considered a less efficient pozzolanic material.

ACS Style

Jorge I. Tobón; Oscar Mendoza Reales; Oscar Jaime Restrepo-Baena; María Victoria Borrachero; Jordi Payá. Effect of Pyrogenic Silica and Nanosilica on Portland Cement Matrices. Journal of Materials in Civil Engineering 2018, 30, 04018266 .

AMA Style

Jorge I. Tobón, Oscar Mendoza Reales, Oscar Jaime Restrepo-Baena, María Victoria Borrachero, Jordi Payá. Effect of Pyrogenic Silica and Nanosilica on Portland Cement Matrices. Journal of Materials in Civil Engineering. 2018; 30 (10):04018266.

Chicago/Turabian Style

Jorge I. Tobón; Oscar Mendoza Reales; Oscar Jaime Restrepo-Baena; María Victoria Borrachero; Jordi Payá. 2018. "Effect of Pyrogenic Silica and Nanosilica on Portland Cement Matrices." Journal of Materials in Civil Engineering 30, no. 10: 04018266.

Journal article
Published: 01 October 2018 in Dyes and Pigments
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ACS Style

E.A. Chavarriaga; A.A. Lopera; T.B. Wermuth; O.J. Restrepo; C.P. Bergmann. Synthesis by solution combustion and optical characterization of violet NASICON-type Mg0.45Co0.05Ti2(PO4)3 pigment. Dyes and Pigments 2018, 157, 1 -10.

AMA Style

E.A. Chavarriaga, A.A. Lopera, T.B. Wermuth, O.J. Restrepo, C.P. Bergmann. Synthesis by solution combustion and optical characterization of violet NASICON-type Mg0.45Co0.05Ti2(PO4)3 pigment. Dyes and Pigments. 2018; 157 ():1-10.

Chicago/Turabian Style

E.A. Chavarriaga; A.A. Lopera; T.B. Wermuth; O.J. Restrepo; C.P. Bergmann. 2018. "Synthesis by solution combustion and optical characterization of violet NASICON-type Mg0.45Co0.05Ti2(PO4)3 pigment." Dyes and Pigments 157, no. : 1-10.

Journal article
Published: 01 September 2018 in Revista Facultad de Ingeniería Universidad de Antioquia
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Lateritic nickel ores need to be reduced to obtain direct reduced iron and nickel alloy. During processing of lateritic nickel ores in rotary kilns, there is a great loss of fines of ores due to degradation during transport into the reactor. These fines contain substantial amounts of nickel and iron, which could be recovered if they are agglomerated and fed back to the process. It is important to note that the processing of minerals with smaller particle sizes yields more efficient reduction processes because there is more surface area for the reducing agent to react with the mineral particles. This work involves the agglomeration of lateritic ore with a nickel content of 1.78%. Briquettes of 10 g were manufactured with the addition of various carbonaceous materials, such as coal, molasses, and coke, with a ratio of carbon/oxygen = 1. These samples were subjected to temperatures of 1100 °C to reduce the iron and nickel oxides present. The reduction percentages were obtained and the products were analyzed by X-ray diffraction (XRD), atomic absorption, thermogravimetry, and scanning electron microscopy to observe the effectiveness of the reducing agent. The highest reduction percentages (95%) were obtained when molasses was used as the reducing agent.

ACS Style

Sandra Consuelo Díaz-Bello; Universidad Santo Tomás; Oscar Jaime Restrepo-Baena; Álvaro Hernando Forero-Pinilla; Universidad Nacional De Colombia; Universidad Pedagógica Y Tecnológica Colombia. Reduction process of low-grade nickel laterite agglomerates using different carbonaceous materials. Revista Facultad de Ingeniería Universidad de Antioquia 2018, 65 -73.

AMA Style

Sandra Consuelo Díaz-Bello, Universidad Santo Tomás, Oscar Jaime Restrepo-Baena, Álvaro Hernando Forero-Pinilla, Universidad Nacional De Colombia, Universidad Pedagógica Y Tecnológica Colombia. Reduction process of low-grade nickel laterite agglomerates using different carbonaceous materials. Revista Facultad de Ingeniería Universidad de Antioquia. 2018; (88):65-73.

Chicago/Turabian Style

Sandra Consuelo Díaz-Bello; Universidad Santo Tomás; Oscar Jaime Restrepo-Baena; Álvaro Hernando Forero-Pinilla; Universidad Nacional De Colombia; Universidad Pedagógica Y Tecnológica Colombia. 2018. "Reduction process of low-grade nickel laterite agglomerates using different carbonaceous materials." Revista Facultad de Ingeniería Universidad de Antioquia , no. 88: 65-73.

Journal article
Published: 01 June 2018 in Science of The Total Environment
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Cyanide leaching is the predominant process of gold extraction in large scale mining. Current initiatives for reducing the use of mercury in small scale and artisanal mining tend towards the cyanide technology as the only feasible alternative. Thus, the deliberate handling in consideration of the hazardous nature of cyanide compounds is an issue of particular importance. The hydrogen cyanide volatilised during the leaching process and from the tailings solutions after the gold extraction is reported to be destroyed by oxidation and photolysis from the surrounding atmosphere of gold mines and the sunlight. Cyanide solutions, drained into the surrounding waterbodies are stated to volatilise at a high rate, thus detoxifying them and releasing hydrogen cyanide to the air. In this study laboratory experiments and field tests were conducted to deliver basic data for the volatilisation and destruction of cyanide in the environment. In our laboratory tests we observed neither oxidation by the oxygen of air nor photolysis by UV-irradiation of cyanides after volatilisation from water. The whole amount of volatilised cyanide was found in the exhaust gas after absorption in a strong basic solution. Field experiments in Segovia (Colombia) could confirm these findings. Cyanide concentrations in a range 17 to 30 mg/L were measured in a local creek. Hydrogen cyanide amounts of 5 ppm were found in the atmosphere surrounding cyanide leaching facilities. With the findings of this study we want to point out that the concentrations of cyanide in the surrounding of cyanide leaching facilities exceed uncritical limits and a destruction via oxidation and photolysis is not detectable. These conclusions should result in initiatives to protect workers and the surrounding population of gold mines from contaminations of cyanide treatments.

ACS Style

Andreas Brüger; Günter Fafilek; Oscar J. Restrepo B.; Lucas Rojas-Mendoza. On the volatilisation and decomposition of cyanide contaminations from gold mining. Science of The Total Environment 2018, 627, 1167 -1173.

AMA Style

Andreas Brüger, Günter Fafilek, Oscar J. Restrepo B., Lucas Rojas-Mendoza. On the volatilisation and decomposition of cyanide contaminations from gold mining. Science of The Total Environment. 2018; 627 ():1167-1173.

Chicago/Turabian Style

Andreas Brüger; Günter Fafilek; Oscar J. Restrepo B.; Lucas Rojas-Mendoza. 2018. "On the volatilisation and decomposition of cyanide contaminations from gold mining." Science of The Total Environment 627, no. : 1167-1173.

Journal article
Published: 01 May 2018 in Hydrometallurgy
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ACS Style

C.G. Perea; Oscar Jaime Restrepo-Baena. Use of amino acids for gold dissolution. Hydrometallurgy 2018, 177, 79 -85.

AMA Style

C.G. Perea, Oscar Jaime Restrepo-Baena. Use of amino acids for gold dissolution. Hydrometallurgy. 2018; 177 ():79-85.

Chicago/Turabian Style

C.G. Perea; Oscar Jaime Restrepo-Baena. 2018. "Use of amino acids for gold dissolution." Hydrometallurgy 177, no. : 79-85.

Journal article
Published: 01 May 2018 in Minerals Engineering
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ACS Style

A. Garces-Granda; Gretchen Lapidus-Lavine; O.J. Restrepo-Baena. The effect of calcination as pre treatment to enhance the nickel extraction from low-grade laterites. Minerals Engineering 2018, 120, 127 -131.

AMA Style

A. Garces-Granda, Gretchen Lapidus-Lavine, O.J. Restrepo-Baena. The effect of calcination as pre treatment to enhance the nickel extraction from low-grade laterites. Minerals Engineering. 2018; 120 ():127-131.

Chicago/Turabian Style

A. Garces-Granda; Gretchen Lapidus-Lavine; O.J. Restrepo-Baena. 2018. "The effect of calcination as pre treatment to enhance the nickel extraction from low-grade laterites." Minerals Engineering 120, no. : 127-131.

Journal article
Published: 04 March 2018 in Water
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Developing its large-scale mining industry is an economic priority for Colombia. However, national capacity to assess and manage the water resource impacts of mining is currently limited. This includes lack of baseline data, lack of suitable hydrological models and lack of frameworks for evaluating risks. Furthermore, public opposition to large scale mining is high and is a barrier to many proposed new mining projects mainly because of concerns about impacts on water resources. There are also concerns about impacts on the uplands that are important water sources, particularly the páramo ecosystem. This paper argues the case for a new framework for Strategic Assessment of Regional Water Impacts of Mining, aiming to support land use planning decisions by government for selected mining and prospective mining regions. The proposed framework is modelled on the Australian Government’s Bioregional Assessments program, converted into seven stages plus supporting activities that meet the Colombian development context. The seven stages are: (1) Contextual information; (2) Scenario definition; (3) Risk scoping; (4) Model development; (5) Risk analysis; (6) Database development; and (7) Dissemination by government to stakeholders including the general public. It is emphasised that the process and results should be transparent, the data and models publicly accessible, and dissemination aimed at all levels of expertise.

ACS Style

Neil McIntyre; Mario Angarita; Nicolas Fernandez; Luis A. Camacho; Jillian Pearse; Carme Huguet; Oscar Jaime Restrepo Baena; Juan Ossa-Moreno. A Framework for Assessing the Impacts of Mining Development on Regional Water Resources in Colombia. Water 2018, 10, 268 .

AMA Style

Neil McIntyre, Mario Angarita, Nicolas Fernandez, Luis A. Camacho, Jillian Pearse, Carme Huguet, Oscar Jaime Restrepo Baena, Juan Ossa-Moreno. A Framework for Assessing the Impacts of Mining Development on Regional Water Resources in Colombia. Water. 2018; 10 (3):268.

Chicago/Turabian Style

Neil McIntyre; Mario Angarita; Nicolas Fernandez; Luis A. Camacho; Jillian Pearse; Carme Huguet; Oscar Jaime Restrepo Baena; Juan Ossa-Moreno. 2018. "A Framework for Assessing the Impacts of Mining Development on Regional Water Resources in Colombia." Water 10, no. 3: 268.