Development of water pre-filters from electrospun membranes of surface functionalized PVDF-HFP for Cr(VI) adsorption

Author(s)

Guilherme Dognani

• Document type: Doctoral Thesis
• Press: Presidente Prudente. 2020-10-27.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências e Tecnologia. Presidente Prudente
• Defense date: 2020-09-25
• Advisor: Aldo Eloizo Job; Deuber Lincon da Silva Agostini

Abstract

The world water consumption has been increasing about 1% per year since the 1980s due to the combination of rapid population growth, socioeconomic development and changes in the consumption patterns of the world population. Nowadays, about 2 billion people live in countries that suffer from high water stress without access to clean water, due to high levels of pollution. Thus, the current crisis is no longer just related to the quantity available and starts to occupy alarming levels in relation to the quality of the water consumed. In this sense, new materials are being developed in order to decontaminate/remediate water sources with different types of contaminants. In this study, porous membranes of PVDF-HFP were produced by electrospinning; the production parameters and the fibers density relationship were studied, then the adsorption tests were carried out. Initially the study of parameters was carried out in order to produce materials with properties to apply in distillation, filtration and adsorption membranes. The electrospun membranes were coated with polyaniline (PAni) by in situ polymerization in order to create a membrane capable of removing chromate ions from aqueous media. The morphology and structure of the membranes were evaluated before and after the polyaniline-coated surface, the results show the success of in situ polymerization process to deposit the PAni molecules in the PVDF-HFP nanofibers. The high porosity and surface area membranes were then tested for their ability to remove chromate and dichromate ions from aqueous medium in high and low concentrations. The static adsorption tests showed the efficiency in metal ions removal, finding an adsorption capacity of approximately 15 mg/g; the removal capacity was also evaluated according to the pH value and the contact time. Dynamic adsorption tests at different flows rate and volumes of chromium solutions were also performed. The desorption study confirmed the recyclability of the PVDF-HFP/PAni membrane, showing an efficiency over 70%, even after 5 cycles of use. When tested in low concentrations, which aim simulate an industrial effluents released in streams and rivers, the PVDF-HFP/PAni membrane had an efficiency of removing Cr(VI) species over 80% when in concentrations over to 0.3 mg/L of Cr(VI). For these low concentrations of contaminant, the adsorption process occurred spontaneously and by exotherm process. Finally, the membrane efficiency was evaluated through cell viability test on fish cells exposed to the Cr(VI) solution after the adsorption process, the cell viability increased about 19%. Given the characterizations carried out and the studies of adsorption, desorption and cell viability, it is concluded that the membrane developed in this work shows itself as a material of potential application in water decontamination, adsorbing anionic species of chromium present in aqueous medium, promoting an environment safer aquatic environment for species that live or use these waters in some way. According the characterizations and the studies of adsorption, desorption and cell viability, it is concluded that the membrane developed in this work proved to be a material with potential application in water decontamination, adsorbing anionic species of chromium present in aqueous medium, and promoting an safer aquatic environment for species that live or use these waters in some way. (AU)

• FAPESP's process: 15/21261-2 - Development of water pre-filters from PVDF electrospun membranes with functionalized surface for adsorption of CR6+
• Grantee: Guilherme Dognani
• Support Opportunities: Scholarships in Brazil - Doctorate