Produção de membranas poliméricas com material de reuso e aplicações

Abstract

This study presents an innovative and sustainable approach to developing polymeric membranes from waste materials, aiming to combat the growing generation of solid waste. The research focused on producing membranes from residual cellulose acetate (AC) from unused cigarette filters and polyethylene terephthalate (PET) from plastic bottles. The AC membranes were modified with the addition of anionic and cationic resins, and the PET membranes were modified with the addition of biopolymers: gum arabic (GA) (1%, 3%, 5%, 7.5%, and 10%) and gum karaya (GK) (1%, 3%, 5%, and 7.5%). The produced AC membranes showed a porous morphology similar to non-residual AC membranes, but they had structural failure and ruptured during permeability tests, which made it unfeasible to continue the assays. Due to this limitation, the studies focused on using PET, which proved to be a more suitable material for the proposed soluble medium separation applications due to its higher mechanical resistance and greater availability as waste. The incorporation of the gums into the PET membranes had a significant effect on the material's properties. Scanning electron microscopy (SEM) analyses showed that adding 1% and 3% of GA preserved a well-defined porous structure, while higher concentrations (5%, 7.5%, and 10%) resulted in unfavorable morphological changes, with less interconnected pores and higher density. Micrographs of the membranes with GK revealed a less homogeneous and potentially more fragile structure, with many voids and low density, which was confirmed by the permeability analysis. The permeability of the PET membranes was enhanced with the addition of GA. The membrane with 5% GA (PGA5) reached a maximum of 157.70 L/h m2, but higher concentrations led to a decrease in permeability. The modification with both natural gums also reduced the PET membrane's hydrophobicity, with the contact angle of the pure membrane (94.00°) decreasing to 33.90∘ with the addition of 7.5% GA. Mechanical resistance was improved with the addition of GA, and the PGA3 membrane (3% GA) showed an elongation of 33%, surpassing that of pure PET (20.40%). The GA-modified membranes were more effective for the proposed application than the GK-modified ones. In hydraulic performance tests for water treatment, with a lignin contaminant solution rejection test at 100 mg/L, the PGA3 membrane showed a high flux recovery rate (between 93.55% and 97.30%) and a low irreversible fouling index (from 2.70% to 6.45%). In the rejection tests, the PGA3 membrane was able to retain between 85.34% and 93.10% of the turbidity, which was significantly higher than the pure PET membrane (65.52% to 74.14%). The electrical conductivity analysis confirmed that the separation occurred by ultrafiltration, retaining suspended solids and allowing the passage of low molecular weight species. In conclusion, modifying residual PET membranes with gum arabic is a promising strategy for developing materials with enhanced properties for liquid medium separation processes. The formulation with 3% gum arabic (PGA3) was the most balanced, ideally combining permeability, hydrophilicity, mechanical resistance, and performance in contaminant rejection. This approach contributes to the valorization of plastic waste, promoting the circular economy and offering a sustainable solution for water treatment and other environmental challenges.