SPECIALIZED EVALUATION AT THE NATIONAL AND INTERNATIONAL LEVEL RELATED TO TECHNICAL, TECHNOLOGICAL AND PUBLIC POLICY CASE STUDIES ON WATER SCARCITY

Development of carbon-based materials from organic waste for application in wastewater treatment

In the project “Implementation of carbon-based materials for the removal of viruses from water,” biochar and hydrochar were synthesized using various raw materials and chemical modifications to remove microbiological contaminants ( e.g., bacteriophages). However, before the experimental part, as a first phase, a bibliographic analysis of the last ten years was carried out on the existing technologies for removing viruses from water and the information on these materials, their modifications, and current applications. As an adsorbent of microbiological, organic, and inorganic contaminants in water, to detect the state of the art of the materials, that is, at what maturity they are, the performances reported with the different modifications, and in terms of novelty, the materials to be synthesized at what point they were. As a second phase of the project, simulation experiments were carried out in which the physical characteristics that carbon materials should have, especially biochar, were determined to be able to remove viruses from water, taking COVID-19 in its various variants as a model virus. After that, the biochar material was synthesized and thermally modified at different time ranges to obtain the physical characteristics (i.e., functional groups) that demonstrated more significant interaction with the virus in the simulation. The materials produced were first tested for removing an organic compound from water (acetaminophen) to determine whether or not the materials were adsorbent. Once it was determined that the material was adsorbent, a bacteriophage virus isolated from wastewater was removed. These experiments were run in continuous flow in packed columns of different sizes and with other water flows. Microbiological experiments demonstrated that the material can be used as a bacteriophage absorbent, but the flow and time of the experiment would affect its yields. As a second phase, hydrochar material was synthesized to generate a material with the same characteristics as biochar but using a simple production method. To do this, materials were first produced using deionized water as a solution; later, this was used as an adsorbent for a dye (i.e., Reactive Orange 84). The results obtained from the said experiment showed a low adsorption capacity (i.e., >5%). However, they functioned as a baseline for the other chemical modifications. As a second phase of the project, the synthesis solution was with sulfuric and nitric acids (H2SO4 and HNO3, respectively) at various concentrations, and, like the materials synthesized with water, these were tested as adsorbents of the same dye. Like the control material, these had a low adsorption capacity because the best conditions of sulfuric acid and nitric acid barely reached 24 and 19% removal, respectively. Considering the above information and the bibliographic analysis, materials impregnated with iron were synthesized through ferrous sulfate heptahydrate. Using solutions with various concentrations of iron as a solvent (i.e., ferrous sulfate heptahydrate), new iron-impregnated materials were obtained, which, like the previous ones, were ineffective as adsorbents of the “RO84” dye. Based on this, the water treatment was changed; that is, this material, containing iron in its structure, can be a catalyst in Fenton-type reactions, which degrade the contaminant from the water instead of removing the contaminant. For the development of this reaction, potassium peroxymonosulfate (PMS) was used as an oxidant, and it was obtained that the best conditions for the degradation of the dye “RO84” were with the material with a 30 mM iron solution (30HC-Fe). at a load of 6g L-1 and a concentration of 9.9 mM of PMS because it achieved a degradation of 86%. Likewise, experiments using mimicked water with loads of carbonates, nitrates, and chlorides determined that the degradation efficiency is reduced by 50% by having all the ions in solution. Furthermore, it was identified that sulfate and hydroxyl are the free radicals that act in greater proportion. This was shown in the characterization tests using specific traps for each of the radicals involved in the reaction. Finally, a technical-economic analysis was carried out with the material that obtained the highest degradation efficiencies.