Evaluation of alumina and activated carbon conjugated to silvernanoparticles as nanofiltration pre-treatments aiming at fouling reduction

ABSTRACT

The poor geographical distribution of water in the national territory combined with its waste, the pollution of watercourses close to urban and industrial centers, and the inadequate efficiency of conventional treatment processes make the treatment and reuse of water topics of increasing importance in Brazil. One of the advanced water treatment methods is membrane separation processes, such as nanofiltration. However, these processes are subject to fouling phenomenon, which causes a gradual decrease in the efficiency of the process. Therefore, the present work aims to evaluate different methods of pretreatment of water to mitigate the formation of biofilm in nanofiltration membranes. The adsorption processes on alumina particles and disinfection through activated carbon impregnated with silver nanoparticles were applied to a sample of a surface water body. Samples with and without pretreatment were nanofiltered and the propensity to fouling was evaluated. The efficiency of the adsorbents, used both separately and together, in removing organic compounds and the UV/Vis, scanning electron microscope, and Energy-dispersive X-ray spectroscopy analyses of the activated carbon impregnated with silver nanoparticles showed that the materials used in the pre-treatment were properly synthesized. It was also possible to identify the main functional groups of the biopolymers present in biofilms formed over time. Finally, it was observed that the adsorption of organic matter is more efficient for the control of rapid fouling while the bactericidal effect stands out in the long-term fouling control.

Keywords:
water treatment; nanofiltration; biofilm mitigation; silver nanoparticles; alumina; activated carbon