Utilização da cápsula do kapok (Ceiba pentandra (L.) Gaerth) para remoção adsortiva de rodamina B em solução aquosa

Abstract

Irregular disposal of waste from human activities has caused several environmental problems, therefore, there has been a strong trend in the development of research and processes that minimize negative impacts. Adsorptive methods have gained prominence in the treatment of effluents, since this technique presents high efficiency in the removal of harmful pollutants to the environment; such contaminants have low biodegradability, resistance to conventional treatments and often appear in low concentrations. The use of biomass as adsorbent material tends to reduce the costs of the adsorptive process due to its availability and abundance. Among the persistent pollutants, there is the compound Rhodamine B, which is a cationic dye, which, in addition to being difficult to remove, presents a health risk. From the biomasses from agricultural activities, we can mention the kapok capsule, which is considered one of the few residues originating from Paineira, since this is one of the only items that do not have application described in the literature. Therefore, making use of this solid waste as an adsorbent provides the recovery of a material that was previously seen only as waste. In this context, the objective was to evaluate the kapok capsule as an adsorbent material for the removal of Rhodamine B in aqueous solutions. Through the characterization techniques employed, such as SEM (Scanning Electronic Microscopy), FTIR (Fourier Transform Infrared Spectroscopy), XRD (X-Ray Diffractometry), zero-load pH and TGA/DTG (Thermogravimetric Analysis) it was possible to know the chemical and morphological characteristics of the adsorbent. To analyze the adsorptive performance, kinetic studies, variations in adsorbent mass, adsorbate concentration, aqueous matrix and pH influence were performed. In view of the analyses, it was observed that the kapok capsule has a morphological structure composed of characteristics that suggest a high adsorptive potential due to its high surface area, presence of vacancies, several pores and characteristic groups of lignocellulosic material. The thermogravimetric analysis showed thermal stability of the natural material. In the hearing tests, it was possible to verify a strong interaction in all applied pH ranges. At natural pH, the minimum percentage of dye removal was 71% in batch tests. In the test in real water, low retention was observed between the adsorbent and the adsorbate, due to the reduction of the adsorptive capacity in salt water, but still presenting a percentage of removal greater than 59%, in more diverse conditions. In the kinetic study, it was observed that in 240 min about 80% of the adsorptive capacity of the material was reached. In the adsorption column tests, great potential for treating colored effluents in continuous flow was observed, with a minimum overall percentage of removal greater than 54 %. The hydrochar produced from the residual adsorbent showed a high adsorptive capacity with a minimum removal of 92 % at natural pH, presenting itself as an excellent alternative to its destination. Such results corroborate the use of this material as an environmentally friendly alternative in a two-way, both in terms of valorization of solid waste and its potential in processes of removing pollutants in the aqueous phase.