Modificação de carvão ativado comercial: remoção de corantes catiônicos e aniônicos, fluoreto, cromo(VI) e mercúrio(II)

Abstract

Activated carbon is a component with a high surface area due to its amount of pores and mainly micropores, which makes it an important absorbing agent when it is necessary to remove contaminants from effluents. In granular form it is usually used in filters, while in powder form it is used in treatment stages, thus requiring post-filtering. To improve the activated carbon adsorption processes, many types of physical and/or chemical treatments are often carried out in the pre- or post-synthesis stages. In the present work, chemical modifications were made using Nitric Acid and Ammonium Hydroxide to obtain Surface Modified Activated Carbons (CASM) with acidic and basic characteristics. To carry out this step, the Rotational Composite Central Design (DCCR) method was used to obtain variations in concentration and contact time with the modifying solutions, in order to evaluate the efficiency of the modified material in terms of removing the pollutants Mercury(II), Fluoride, Chromium(VI), Methyl Orange and Methylene Blue, which are substances of environmental relevance in view of the degree of pollution and require advanced treatment methods for their decontamination. The use of CASM samples in which their modifications varied were tested to then analyze their adsorptive capacities to remove these pollutants from the aqueous medium and thus obtain the sample that presented the best performance for each of the pollutants. Different values were obtained for each of the tests performed, and it was found that the CASM-10N sample (55% of acid kept for 18 hours) had a greater adsorption capacity compared to the commercial activated carbon (CAC) used as a parameter, and obtained superior results in resolving all pollutants, Mercury (6%), Fluoride (123%), Chromium (603%), Methyl Orange (17%) and Methylene Blue (3%). However, all the CASM analyzed with the contaminants showed promising results, with the CASM-7N being the one that best adsorbed methyl orange and the others showing values always higher than the CAC, with the exception of the tests with mercury, where only the CASM-10 showed an increase in your ability. Thus, it turned out that modifications using Nitric Acid and Ammonium Hydroxide improve the performance of the CAC in adsorbing the pollutants studied in the vast majority of cases, becoming a way to carry out the advanced treatment of contaminants.