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This study evaluated the desorption of cadmium (Cd) from cocoa waste-derived flour using organic acids. Cocoa pods were collected from Antioquia and Casanare, Colombia, to analyze the geographical Cd content and its distribution within the pod tissues. Acid selection was performed using a multi-criteria decision-making (MCDM) matrix, and Cd desorption was assessed through a full factorial 23 experimental design, considering acid concentration, pulp density, and agitation speed. Additionally, the oxidation–reduction potential (ORP) was monitored as an indicator of the electrochemical dynamics of the process. The results indicated that pods from Casanare exhibited higher Cd concentrations (1.63 ± 0.20 ppm) compared with those from Antioquia (0.87 ± 0.22 ppm), with 49.31% of the metal being accumulated in the pod. Parameters of citric acid at 0.5 M, 5 g/L pulp density, and 120 rpm were found to be optimal for the Cd desorption process, achieving over 95% efficiency. Based on ORP monitoring, a heuristic was proposed to determine the contact time during leaching. This work outlines a scalable process for Cd desorption, adding value to cocoa industry waste for potential applications.

This study evaluates the preg-robbing effect on gold recovery through a carbon-in-leach process, comparing three reactor types: glass, stainless steel, and stainless steel coated with ceramic resin. Protonated activated carbon (PAcC) and anthracite carbon (PAnC) were used as adsorbents. The results show that PAcC achieved a significantly higher gold adsorption rate of up to 99.87%, compared to PAnC, which achieved a maximum of 66%, mitigating the preg-robbing effect. The stainless steel reactor performed best, with gold recovery rates exceeding 90%, as confirmed by a multi-criteria decision matrix evaluating factors like durability, mechanical strength, and corrosion resistance. A 24−1 fractional factorial design identified key variables for optimal recovery, with aeration of 9.31 L/min, a PAcC pulp density of 2.5 g/L, and the use of Puerto Berrío ore resulting in the highest gold recovery, reaching 18.38 ppm. The mass balance confirmed that gold adsorption on PAcC was the most efficient, leaving less than 0.13% gold in the leachate. These results demonstrate the superiority of PAcC and stainless steel reactors in mitigating the preg-robbing effect, offering an effective solution for scaling up gold recovery processes.

This case study presents a pioneering approach for in-situ immobilization of Chlorella sp. microalgae in photobioreactors, achieved through the synergistic combination of immobilization within a polymeric gel and adsorption on a Nylon mesh, termed the CIPGA system. By applying Buckingham's Pi theorem, correlations among governing variables of the CIPGA were established, and a comprehensive full factorial experimental design assessed the significance of light intensity, reactor diameter, and volumetric airflow. Optimal immobilization conditions for Chlorella sp. were determined: light intensity of 71 μmolm−2s−1, photobioreactor diameter of 0.15 m, and aeration air flow rate of 6.7 × 10−6 m3 s−1. A non-linear three-dimensional model utilizing dimensionless parameters was formulated, exhibiting strong accuracy in predicting scaling-up conditions. The CIPGA system demonstrated remarkable efficacy, forming extensive microalgal strands and a biofilm within a complex three-dimensional architecture. Characterization through FTIR spectra analysis revealed significant attributes, including proteins, polysaccharides, and lipid substances. Notably, the presence of exopolysaccharides emerged as a key factor driving microalgal adhesion to hydrophobic surfaces. The versatile applications of this innovative immobilization approach encompass various bioprocesses, including high-value product generation (biohydrogen, biodiesel, photopigments), nutrient and heavy metal ion removal, biosensors, and wastewater treatment processes.

In recent decades, the extensive use of synthetic dyes in dye-based industries, particularly the textile sector, has led to environmental contamination, raising concerns about water quality and human health. This study aimed to develop a sustainable approach for treating wastewater contaminated with indigo dye through a hybrid approach combining bioremediation and nanofiltration for reuse. In the first stage, two bioaugmentation strategies were compared: using native microorganisms in the wastewater (R-1) and activated sludge from a municipal wastewater treatment plant (R-2). Both strategies effectively reduced chemical oxygen demand (COD) to 200 mg/L and eliminated over 90% of the color. Statistical analysis showed no significant difference in COD removal efficiencies between R-1 and R-2. Correlation analysis revealed a strong association (>99%) between COD, suspended solids (SS) concentration, and color in the reactors, providing insights into sustainable monitoring for wastewater treatment, with potential cost reductions and environmental benefits. In the second stage, nanofiltration (NF) with organic membranes was employed to obtain high-quality permeate for reuse in denim washing. Permeability measurements for R-1 demonstrated similar membrane behavior (NF 270 and Alfa Laval NF) at various transmembrane pressures (TMPs). Both membranes achieved color rejection rates exceeding 96% and COD removal efficiency over 80% for all TMPs. NF tests with R-2 effluent revealed higher permeate flux of 23.71 L·h−1·m−2 at a TMP of 5 bar, with Alfa Laval NF membrane exhibiting superior COD and color rejection compared to NF 270 membrane. The techno-economic analysis showed the hybrid approach of biological treatment/NF to have a mean unit cost of 0.97 USD/m3, indicating economic feasibility and competitiveness against commercial purification processes for sustainable water reuse.

The exponential growth of electronic waste (e-waste) has raised significant environmental concerns, with projections indicating a surge to 74.7 million metric tons of e-waste generated by 2030. Waste printed circuit boards (WPCBs), constituting approximately 10% of all e-waste, are particularly intriguing due to their high content of valuable metals and rare earth elements. However, the presence of hazardous elements necessitates sustainable recycling strategies. This review explores innovative approaches to sustainable metal nanoparticle synthesis from WPCBs. Efficient metal recovery from WPCBs begins with disassembly and the utilization of advanced equipment for optimal separation. Various pretreatment techniques, including selective leaching and magnetic separation, enhance metal recovery efficiency. Green recovery systems such as biohydrometallurgy offer eco-friendly alternatives, with high selectivity. Converting metal ions into nanoparticles involves concentration and transformation methods like chemical precipitation, electrowinning, and dialysis. These methods are vital for transforming recovered metal ions into valuable nanoparticles, promoting sustainable resource utilization and eco-friendly e-waste recycling. Sustainable green synthesis methods utilizing natural sources, including microorganisms and plants, are discussed, with a focus on their applications in producing well-defined nanoparticles. Nanoparticles derived from WPCBs find valuable applications in drug delivery, microelectronics, antimicrobial materials, environmental remediation, diagnostics, catalysis, agriculture, etc. They contribute to eco-friendly wastewater treatment, photocatalysis, protective coatings, and biomedicine. The important implications of this review lie in its identification of sustainable metal nanoparticle synthesis from WPCBs as a pivotal solution to e-waste environmental concerns, paving the way for eco-friendly recycling practices and the supply of valuable materials for diverse industrial applications.

Nanoparticle deposition on various substrates has gained significant attention due to the potential applications of nanoparticles in various fields. This review paper comprehensively analyzes different nanoparticle deposition techniques on ceramic, polymeric, and metallic substrates. The deposition techniques covered include electron gun evaporation, physical vapor deposition, plasma enriched chemical vapor deposition (PECVD), electrochemical deposition, chemical vapor deposition, electrophoretic deposition, laser metal deposition, and atomic layer deposition (ALD), thermophoretic deposition, supercritical deposition, spin coating, and dip coating. Additionally, the sustainability aspects of these deposition techniques are discussed, along with their potential applications in anti-icing, antibacterial power, and filtration systems. Finally, the review explores the importance of deposition purities in achieving optimal nanomaterial performance. This comprehensive review aims to provide valuable insights into state-of-the-art techniques and applications in the field of nanomaterial deposition.

This research presents an experience of post-digital learning of biotechnology in rural areas in Colombia by implementing a massive open online course (MOOC) for biotechnology education called Open Biotec. The objective was to improve Colombian rural development by creating learning communities around five topics: waste management, environmental biotechnology, bioprocesses, alternative energies, and bio-entrepreneurship. The study utilized various methods, including a socioeconomic diagnosis of a subregion of the department of Antioquia, Colombia, and the creation of MOOCs using the Action Research methodology. The pilot test of the training route in biotechnology involved the progressive development of the MOOC courses that comprise it. Around 918 students from rural areas were trained, and statistical analysis showed that the average grade of the students increased significantly from 6.13 to 7.53 and the median from 6.15 to 8.00. The study results demonstrate how the learning experience designed in the Open Biotec MOOC increases the degree of knowledge of students in this field of biotechnology, offering an opportunity to establish sustainable learning communities with participation and collaborative action mediated by virtual tools. The study concludes that rural education in Colombia could be strengthened with a training strategy for rural communities supported by MOOCs focused on the responsible use of local biodiversity from a biotechnological perspective.

The leaching processes for metals using organic substances represent a sustainable approach to recover precious minerals from solid matrices. However, the generation of organometallic species and the lack of thermodynamic diagrams make it difficult to advance the understanding of their behavior and optimize the process. In this work, a thermodynamically and stoichiometrically consistent mathematical model was developed to estimate the thermodynamic stability of organic substances during the leaching process, and iron leaching with oxalic acid was used as a case study. The Pourbaix and the global thermodynamic stability diagrams for the system were developed in this study. Using a Gaussian®, it was estimated that the Gibbs free energy formation for Fe(C2O4)22−, Fe(C2O4)21−, and Fe(C2O4)33− was −1407.51, −2308.38, and −3068.89 kcal/mol. A set of eleven independent reactions was formulated for the sixteen species involved in the leaching process, and its stability functions in terms of Eh and pH were calculated to generate a 3D global thermodynamic stability diagram. According to the Eh-pH diagrams for the leaching process, ferrioxalate was identified as the most stable and predominant species in the leaching process at pH above 6.6 under reductive conditions. The mathematical model developed in this work resulted in a thermodynamic tool for predicting leaching processes.

Colombia has a diverse range of marine ecosystems in the coastal and insular areas of the Caribbean Sea and the Pacific Ocean. Seaweed research has focused mainly on the identification and taxonomic distribution of 628 species identified so far, mainly in the Caribbean Sea. Among the most widely cultivated genera of seaweeds in open-sea pilot systems in Colombia are Hydropuntia, Gracilaria, Hypnea, Kappaphycus, and Eucheuma. These genera have shown low yields as a consequence of high tissue fragility, epiphytism, sedimentation, and nitrogen deficiency. In addition, the evaluation of the biological activity of selected seaweed compounds has advanced considerably, focusing on their composition and their use for direct consumption by humans and animals. Despite the diversity of seaweeds, as well as certain technical and scientific advances, Colombia is still lagging behind other countries in seaweed exploitation, both in Latin America and worldwide. This current status raises the need to increase research, technological (agro-tech) appropriation, and the adoption of effective public policies that will boost algal businesses. In addition, seaweed cultivation could support the current blue economy transition in Colombia, which could eventually allow the country to enter the global seaweed market.

Scaling up bioprocesses from the experimental to the pilot or industrial scale involves heuristics and scale relationships that are far from the specific phenomena and are usually not connected to the experimental data. In complex systems, the scaling-up methodology must connect the experimental data with the tools of engineering design. In this work, a two-stage gold bioleaching process was used as a case study to develop a mathematical model of bioprocess scaling that combines the design of experiments with dimensional analysis using the Buckingham Pi theorem to formulate a predictive model that allows scaling up bioprocesses. It was found that the C/N, C/K, and T/C ratios are dimensionless factors that can explain the behavior of a system. Using the Pearson Product–Moment bivariate analysis, it was found that the dimensionless factors C/N and C/K were correlated with the leaching potential of the fermented broth at 1060 cm−1. With these results, a non-linear logarithmic model based on dimensionless parameters was proposed to explain the behavior of the system with a correlation coefficient of R2 = 0.9889, showing that the optimal conditions to produce fermented broth comprised a C/N ratio close to 50 and a C/K ratio close to 800, which allows predicting the scaling of the bioprocess.

In this work, the production of biologically synthesized silica nanoparticles was proposed to prepare a nanosuspension as a thermal fluid in parabolic solar panels at the laboratory level. Silica nanoparticles were produced from construction sand in two stages. Biosynthesis broth was produced by Aspergillus niger aerated fermentation in a 1 L bioreactor for 9 days. Each supernatant was contacted with 18% construction sand in a 500 L reactor with mechanical agitation, at a temperature of 25 °C, and a contact time of 30 min. Subsequently, the separation process was carried out. For day 9, a pH value of 1.71 was obtained as well as acid concentrations of 15.78 g/L for citrus and 4.16 g/L for malic. The metal extraction efficiency of Si nanoparticles was 19%. The vibration peaks in the FTIR were characteristic of the presence of silica nanoparticles in wavenumbers 1020 cm−1 and 1150 cm−1. Finally, a prototype solar radiation test bench for parabolic systems was built and provided with a radiation source that falls on a translucent pipe that transports the nanoparticles, which has a pump and a series of thermocouples. The heat capacity of the biotechnologically produced silica nanoparticle suspension was 0.72 ± 0.05 kJ/kgK, using material and energy balances in the flow circuit.