Preparo de membranas de ultrafiltração de polissulfona contendo carvão ativado obtido da pirólise do resíduo de abacaxi

Abstract

Pineapple (Ananas comosus) is one of the most widely consumed fruits globally, with Brazil producing 1.5 million tons in 2021. Approximately 50% of the fruit is converted into agro-industrial waste, including stem, crown, and peel, which contain valuable industrial components like the enzyme bromelain. Ultrafiltration is a process used in the food and pharmaceutical industries to concentrate macromolecules, but it has limitations due to fouling. The present research proposed the development of ultrafiltration membranes based on polysulfone incorporated with activated carbon, aiming to mitigate fouling during ultrafiltration of pineapple peel extract and improve both permeate flux and bromelain recovery. The activated carbon was obtained through the pyrolysis of the waste from pineapple peel, from which the extract was also obtained, employing CO2 for the physical activation of the carbon. The membranes were prepared with different contents of polysulfone (between 15 and 17 wt%) and activated carbon (up to 1 wt%), and were characterized in terms of chemical, morphological, and transport properties. The produced activated carbon exhibited an area of 220 m2.g-1, an average pore diameter of 1.43 nm, and an average particle diameter of 19 ± 3 µm, revealing a microporous structure. Scanning electron microscopy revealed high heterogeneity in the carbon particles, with a tendency to form clusters, possibly as a way to reduce surface energy. Energy-dispersive X-ray spectroscopy analysis identified the presence of various elements in the activated carbon, with higher levels of carbon and oxygen. Regarding the membranes, the main results of the study indicated that the addition of 1% activated carbon in the membranes resulted in a significant increase in the molecular weight cut-off, reduction in protein interaction and fouling, and improvement in pure water flux recovery. The membranes showed high selectivity for bromelain, with recoveries above 81% and pure water flux recovery above 70%. It is worth noting that membrane M5, which contains 15% polysulfone and 1% activated carbon, achieved a recovery of the enzyme bromelain above 91%, with a loss of activity of 15.52% and a recovery of hydraulic flux of 95%, demonstrating the effectiveness of adding activated carbon to membranes with low polymer content in improving the selectivity and efficiency of the ultrafiltration process.