Reutilização de fios de poliamida na obtenção de membranas para o tratamento de efluentes contendo corantes têxteis

Abstract

This study addresses a new way of using a waste material, polyamide66, replacing it as a raw material in the production of membranes for treating textile effluents. Microfiltration membranes were prepared by phase inversion using polyamide66 (PA66) synthetic fiber residue from the automotive industry, and adding 1, 3, and 5% titanium dioxide (TiO2) to increase membrane porosity. The solutions and membrane films were evaluated with morphological characterization techniques and flux measurements. The viscosities of hybrid solutions increased with the increase in TiO2 content because it has a high surface available for adsorption in PA66 chains, promoting the formation of a mechanically stable suspension at a low shear rate. The AFM analysis showed that the pure and hybrid PA66 membranes have irregular surfaces confirmed by the roughness parameters, and this increase was directly proportional to the added content of TiO2. Field emission SEM analyses showed an increase in the porous surface of the membranes after TiO2 addition, confirmed in the porosity test, even though this addition has increased the density of the hybrid membranes. All the membranes with the addition of TiO2 showed lower values of contact angle when compared to the pure PA66 membrane, corresponding to higher hydrophilicity, due to the water absorption characteristic of the materials present. The tests of fluxes with water presented initially a decrease and then stability around 30 min, due to the compaction or swelling effects in the membranes, which followed until the end of the process, over 60 min. Given the above, it was possible to see that the introduction of TiO2 changed the rheological properties of the solutions and the morphology of the hybrid membranes. The roughness present in the hybrid membranes indicated a higher permeability, giving evidence of the existence of pores present on their surfaces. In addition, the inorganic load present provided an increase in permeate flux with water, with PA66/3% TiO2 membrane standing out. Effluents with the red dye at different concentrations were developed to evaluate the effect of particle loading on membrane flux on its removal efficiency. The results showed that as the concentration of red dye in the effluent increased, the permeate flux of the membrane decreased. However, the concentration of dye in the effluent did not affect the performance of the membranes in removing the dye, all compositions tested removed above 98% of dye from the produced permeate. In both tests, the best fluxes were produced at 1.5 bar pressure using the PA66/3% TiO2 membrane, and for the tests containing dye, all membranes made the highest permeate volume at 100 mg.L-1 red dye concentration. The permeate produced by all membranes met the tested water quality standards of color, pH, and turbidity. Therefore, hybrid membranes obtained present potential for post treatment effluents stage using textile dyes