Biochars are emerging eco-friendly products showing outstanding properties in areas such as carbon sequestration, soil amendment, bioremediation, biocomposites, and bioenergy. These interesting materials can be synthesized from a wide variety of waste-derived sources, including lignocellulosic biomass wastes, manure and sewage sludge. In this work, abundant data on biochars produced from coconut-shell wastes obtained from the Colombian Pacific Coast are presented. Biochar synthesis was performed varying the temperature (in the range: 280 °C–420 °C) and O2 feeding (in the range: 0–5% v/v) in the pyrolysis reaction. Production yields and some biochar properties such as particle size, Zeta Potential, elemental content (C, N, Al, B, Ca, Cu, Fe, K, Li, Mg, Mn, Na, P, S, Ti, Zn), BET surface area, FT-IR spectrum, XRD spectrum, and SEM morphology are presented. This data set is a comprehensive resource to gain a further understanding of biochars, and is a valuable tool for addressing the strategic exploitation of the multiple benefits they have.

Utilization of UV LED light is trending in the development of photoreactors for pollutant treatment. In this study, two different geometries were studied in the degradation of methylenebBlue (MB) using high power UVA LED as a source of light. The dosage, initial concentration, electric power, and HO addition were evaluated in the two geometries: a mini CPC (Cilindrical Parabolic Collector) and a vertical cylindrical with external irradiation both coupled with LED UVA. Best degradation was obtained for 0.3 g L TiO, 40 min, and 15 ppm of MB of initial concentration in the standard batch reactor. It was found that the best system was a cpc geometry. Also, hydrogen peroxide was used as an electron acceptor and 97% degradation was obtained in 30 min with 10 mM HO and 0.4 g TiO/L. Power of the LEDs was also evaluated and it was found that 20 W m is the best operational condition to achieve the best MB degradation avoiding the oxidant species recombination.

Wet coal beneficiation in Colombia is prohibitive due to the high cost and scarcity of commonly used dense media. The practical value of this study is that it demonstrates for the first time that a common fertilizer, calcium nitrate, can be used in the beneficiation of low-grade Colombian coals. Three high-ash low-grade Colombian coals (Valle, Cundinamarca, and Antioquia) commonly used in Colombian sugar mill stoker furnaces were tested. Coal mineralogy and prevalence were analyzed before and after washing using mineral liberation analysis. The swelling potential of the coals was assessed using a novel application of thermal mechanical analysis (TMA) and an ash fusion oven (AFO). Calcium nitrate reduced ash levels across all size fractions, even for highash coals like Valle (29% to below 7%) to acceptable levels for coke manufacturing or pulverized fuel combustion. The novel use of TMA and AFO to analyze coal swelling demonstrated that swelling varies under constrained and unconstrained conditions and the small sample size allows for rapid testing of coal swelling. This study has demonstrated that the use of common fertilizers can allow beneficiation to become a processing option for low-grade coals in Official Development Assistance countries where conventional dense media is prohibitively expensive.

This study describes the development and formulation of a novel mathematical model for coal flotation kinetic. The flotation rate was considered as a function of chemical, operating and petrographic parameters for a global flotation order n. The equation for flotation rate was obtained by dimensional analysis using the Rayleigh method. It shows the dependency of flotation kinetic on operating parameters, such as air velocity and particle size; chemical parameters, such as reagents dosage and solids content; and mineral and maceral composition of coal. The flotation rate equation integrates the kinetic coefficient and the intrinsic characteristics of coal with dimensional consistency, and it is expressed by three dimensionless numbers which have physical chemical meaning. The model also exhibits similarities with traditional transport phenomena models represented by dimensionless numbers and predicts the flotation kinetic constant of a Colombian coal sample showing a good correlation between experimental and calculated values.Keywords: coal flotation; flotation rate; kinetic model. Un nuevo modelo matemático para la cinética de flotación de carbonesResumen Este estudio describe el desarrollo y formulación de un nuevo modelo matemático para la cinética de flotación de carbón. La velocidad de flotación se considera una función de parámetros químicos, operacionales y petrográficos para la flotación global de orden n. La ecuación de velocidad de flotación se obtuvo por análisis dimensional usando el método de Rayleigh. Este método muestra la dependencia de la cinética de flotación sobre los parámetros de operación tales como velocidad del aire y tamaño de partícula; parámetros químicos tales como dosis de reactivos y contenidos de sólidos; y composición mineral y maceral del carbón. La ecuación de velocidad de flotación integra el coeficiente cinético y las características intrínsecas del carbón con consistencia dimensional, y se expresa por tres números adimensionales que tienen significado químico físico. El modelo también muestra similitudes con los modelos tradicionales de fenómenos de transporte representados por números adimensionales y predice la constante cinética de flotación de un carbón Colombiano mostrando buena correlación entre los valores experimentales y calculados.Palabras clave: flotación de carbón; tasa de flotación; modelo cinético.

A test-rig closed-loop flotation column was used to observe the effect of diesel oil (collector) and Flomin F-425 (frother) on mass yield and ash content for two Colombian coals: Caypa (northern zone) and Guachinte (southwestern zone). The coal samples of less than 38 µm (-400 M) were processed in a collector concentration range of 0,32 to 1,60 kg/ton of coal, as well as a frother concentration range of 10 to 50 ppm. The response surface methodology was used for the experimental test runs. The results showed that the maximum mass yield obtained by Caypa coal was 98,39% at 1,28 kg of collector/ton of coal and 40 ppm of frother concentration, whereas Guachinte coal obtained a maximum mass yield of 94,71% at 0,96 kg of collector/ton of coal and 30 ppm of frother concentration. In general, for Caypa coal, the mass yield tends to increase (low ash removal) with the collector and frother concentration increase; while the mass yield tends to decrease (high ash removal) for Guachinte coal when the collector concentration increases (low ash removal) at high frother concentrations. It is worth highlighting that the ash content of 0,65% obtained for Caypa coal is the lowest value reported in the literature while employing a test-rig loop flotation column in a single stage, which is considered to be an ultra-clean coal obtained by a physical cleaning process.