Examinando por Autor "Rivas, Mariella"

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    Clays tailings flocculation using bio-based flocculants from Nannochloropsis gaditana
    (Springer, 2025) Huapaya, Katiuska; Grisales, Jeferson; Botero, Yesica; Salamanca, Alexandra; Lara, Paloma; Cisternas, Luis A; Jeldres, Ricardo; Jeison, David; Panico, Antonio; Zapata, Manuel; Rivas, Mariella
    In copper mining water recirculation is a crucial aspect, with approximately 70% used during the ore processing stage being recirculated. After extraction, the process water has a high concentration of clays, which exert a deleterious effect on mineral concentration, so the industry employs flocculation processes to remove them using chemical flocculants derived from polyacrylamide, which are toxic and persistent in the environment. The development of bio-based flocculants derived from microalgae represents a sustainable alternative for clay removal. Therefore, sedimentation tests were performed using the Jar-test method with Nannochloropsis gaditana to remove kaolinite-type clay. The sedimented flocs were subjected to various analyses, including zeta potential, Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). The zeta potential of N. gaditana is negative in deionized water across a pH ranging between 2 and 11, whereas in seawater only at pH between 7 and 9. Nannochloropsis gaditana was evaluated under different conditions (live cells, boiled cells, wet biomass, and freeze-dried biomass). Live and boiled cells were the most effective in kaolinite removal, as they instantly reduced turbidity to 76 FNU, achieving a sedimentation efficiency close to 97% at pH 7, which favored seawater clarification. Sedimentation efficiency was higher when using 10 g L−1 of live N. gaditana cells compared to the chemical flocculant used as a control. Finally, FT-IR was used to determine the degree of kaolinite absorption on the surface of microalgae, and showed that the presence of carboxylic functional groups and polysaccharide amides on the cell surface favors this interaction.
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    Investigation of the key factors favouring the biocementing effect of microbially induced calcite precipitation when applied to mine tailings
    (Elsevier, 2025) Zuñiga Barra, Hector; Velastegui, Edgar; Toledo-Alarcón, Javiera; Jorquera, Lorena; Rivas, Mariella; Jeison, David
    Recent research has suggested the applicability of microbially induced calcite precipitation (MICP) to improve wind erosion resistance across diverse media, from clay to sandy soils. While various factors influencing MICP performance have been investigated, comprehensive studies considering the synergistic interactions between biocementation media composition, dosages, available urease activity, and urea-calcium ratios are limited. Consequently, identifying key factors governing MICP during tailings biocementation remains crucial for optimizing treatment strategies. This is specially the case for MICP application for mine tailings biocementation, due to the limited available research dealing with this substrate. This research studied the effect of several factors, when biocementing mine tailings, using a factorial design. The results confirm the key role of the biocementation media dosage and the urea-calcium ratio, and their synergistic interaction during biocementation of tailings, as they determine the calcium and inorganic carbon available to produce calcium precipitates. Biocementation of tailings by applying MICP substantially improved surface strength, leading to a drastic reduction in wind erosion resistance. These results confirm the potential of MICP to become an interesting tool to reduce windblown dust emissions from tailings deposits.
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    Response to static magnetic field-induced stress in scenedesmus obliquus and nannochloropsis gaditana
    (MDPI, 2021) Serrano, Génesis; Miranda-Ostoijc, Carol; Ferrada, Pablo; Wulff-Zotelle, Cristian; Maureira, Alejandro; Fuentealba, Edward; Gallardo, Karem; Zapata, Manuel; Rivas, Mariella
    Magnetic fields in biological systems is a promising research field; however, their application for microalgae has not been fully exploited. This work aims to measure the enzymatic activity and non-enzymatic activity of two microalgae species in terms of superoxide dismutase (SOD), catalase (CAT), and carotenoids, respectively, in response to static magnetic fields-induced stress. Two magnet configurations (north and south) and two exposure modes (continuous and pulse) were applied. Two microalgae species were considered, the Scenedesmus obliquus and Nannochloropsis gaditana. The SOD activity increased by up to 60% in S. obliquus under continuous exposure. This trend was also found for CAT in the continuous mode. Conversely, under the pulse mode, its response was hampered as the SOD and CAT were reduced. For N. gaditana, SOD increased by up to 62% with the south configuration under continuous exposure. In terms of CAT, there was a higher activity of up to 19%. Under the pulsed exposure, SOD activity was up to 115%. The CAT in this microalga was increased by up to 29%. For N. gaditana, a significant increase of over 40% in violaxanthin production was obtained compared to the control, when the microalgae were exposed to SMF as a pulse. Depending on the exposure mode and species, this methodology can be used to produce oxidative stress and obtain an inhibitory or enhanced response in addition to the significant increase in the production of antioxidant pigments.
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    Sustainable biocementation of mine tailings: Reduction of urea requirements through bicarbonate-based MICP
    (Elsevier, 2025) Zuñiga Barra, Hector; Pardo-Vasquez, Camila; Velastegui, Edgar; Martinez-Ruano, Jimmy Anderson; Rivas, Mariella; Jeison, David
    Microbially induced calcite precipitation (MICP) has emerged as a promising technique to contribute to a more sustainable management of mine tailings deposits. While ureolytic activity has been the predominant driver of conventional MICP to date, the associated release of ammonia poses significant environmental hazards. This study explores a novel, environmentally friendly approach by replacing urea with sodium bicarbonate as the carbon source for MICP, with the aim of reducing urea requirements and thus ammonia release. Leveraging the principles of the MICP, it was observed that when urea concentration was reduced to 0.7 M, by replacing it with bicarbonate, surface strength was close to 400 kPa. Furthermore, wind tunnel testing showed a significant reduction in dust emission, where the mass loss rate of the biocemented sample was below 10 kg m⁻ 2 h⁻ 1 , which means a 9-fold reduction compared to untreated samples. So, it was demonstrated that bicarbonate can effectively replace urea, achieving a relevant reduction of up to 75 % in urea use without compromising the surface strength of the biocemented tailings and reducing the environmental hazards of ammonia release. These results highlight the potential of bicarbonate-based MICP as an innovative and sustainable approach to mitigate the environmental impacts associated with tailings deposits.