Depuración de efluentes industriales con carbón activo. Adsorción de contaminantes y regeneración del adsorbente

Resumen

[EN]The treatment of industrial wastewater is one of the main areas of growth for activated carbon. This is due to increasingly stringent environmental regulation, a greater emphasis on water reutilization, decontamination of effluents and the need for lower disposal costs. Treatment of industrial wastewater is also increasing in industrialized countries as industrial activity rises and the need to reuse water and reduce effluent pollution becomes greater. While the issue of textural characteristics of activated carbons has been widely studied by numerous studies and are reasonably well understood, works on elucidating the role of surface chemistry of activated carbons in the process of adsorption of organic compounds have not been so successful. This information may be useful for subsequent applications of activated carbon in industrial processes such as the manufacture of chemicals, pharmaceuticals and their intermediates, where activated carbon is used in purification and recovery processes, in order to enhance product quality and consistency. In short, adsorption on activated carbon and its regeneration seems to be a worthy area of study. In this work, the adsorption of phenol and salicylic acid was carried out on different activated carbons. It was found that their adsorptive capacities depend on both the textural characteristics of the activated carbons (densities, specific surface area and pore size distribution) and their chemical and structural properties. Oxidation of the adsorbents under different conditions showed that the surface chemistry of activated carbons plays an important role in phenol retention. On the other hand, salicylic acid retention seems to be related to the textural characteristics of the activated carbon rather than its surface chemistry. Oxidation treatments not only alter the surface chemical properties of the active carbons, but also their texture. It was found that the physical morphology of the activated carbon is affected by the strength of the oxidizing agent and the operating conditions. On the other hand, heating treatments applied to activated carbon enhance the basicity of the samples, by removing oxygenated functional groups on the carbon surface. Regeneration operating conditions have a substantial influence on the adsorption capacity of the activated carbons, not only because textural properties are modified during the regeneration step, but also because the desorption rate of the adsorbate retained is affected to a great extent by the regeneration conditions. Under a carbon dioxide atmosphere, a simultaneous activation step takes place in the carbonaceous adsorbent, facilitating the regeneration and subsequent adsorption on the activated carbon.