The adsorption of zinc from aqueous solutions on cassava peels (Manihot esculenta) modified with citric acid was studied. Cassava peels were modified with citric acid according to a fractional experimental design with central point, which had as independent variables: mixing time, drying time, reaction time, mixing temperature, reaction temperature, and biomass/acid ratio. In order to determine the best conditions to perform the chemical modification, removal experiments were carried out with the samples specified in the experimental design. Under these conditions, kinetic experiments were developed resulting in fast adsorption of zinc with equilibrium times within 20-30 minutes range, and adsorption capacities of 3.042 mg/g and 4.904 mg/g for zinc solutions of 30 and 50 mg/L, respectively. At these initial concentrations of zinc, the experimental data fit the kinetic pseudo-second order model.

With the increase in the world population, the needs for energy generation have increased, the biggest contribution for this production comes from fossil fuels, which causes significant negative impacts on the environment and sustainability, such as global warming and stock-outs. In this way, it is essential to develop renewable energy alternatives that gradually replace conventional sources. However, these kinds of sources mostly dependent on environmental conditions, so they have the disadvantage of being intermittent and fluctuating. It is considered that hydrogen can be an attractive option for energy storage maximizing the benefit of renewable energy sources. In the last decades, different technologies have been developed to the use of hydrogen as backup and a renewable energy source. This study provides an inspection of the hydrogen technologies that range from the ways to produce hydrogen from renewable energy sources to their different storage alternatives. It is also presented an outlook of available energy policies and development background in different Latin American countries for power generation using renewable sources. Finally, the analysis focuses its attention in the Colombian potential for several sources (solar, wind, biomass) combined with the use of production and storage technologies for hydrogen as an energy carrier.

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