Abstract
A photoactive gel has been fabricated on the surface of polyethylene membranes for enhancing the fouling resistance during olive mill wastewater treatment. Light and pH responsive materials have been introduced in the membrane surface through the build up of a layer-by-layer pattern, which is formed by photocatalytic nanoparticles and ionic polyelectrolytes. The best working conditions to contrast foulants adsorption have been explored and identified. Repulsive interfacial forces and assisted transfer of foulants to catalytic sites have been envisaged as crucial factors for contrasting the decline of the flux during microfiltration. Tests in submerged configuration have been implemented for six continuous hours under irradiation at two different pH conditions. As a result, a worthy efficiency of the photoactive gel has been reached when suitable chemical microenvironments have been generated along the shell side of the membranes. No additional chemical reagents or expensive back-flushing procedures have been necessary to further clean the membranes; rather, fast and reversible pH switches have been enough to remove residues, thereby preserving the integrity of the layer-by-layer (LBL) complex onto the membrane surface.
Highlights
The olive oil keeps unrivalled nutritional properties and health benefits, since its high content of monounsaturated fatty acids is concerned to strongly reduce the risk of heart disease, high blood pressure, and stroke [1]
polyacrylic acid (PAA) in aqueous solutions has been prepared at pH 6.75 without adding salts and hasand beenhas successively successively patterned with a counter solution of PDDA
HPLC analyses reveal the presence of removed residues, such as phenols, i.e., catechol, hydroxtyrosol and tyrosol, in washing streams at pH 7 (Figure 9b), whereas no contaminants are detectable in solution at pH 1 (Figure 9c)
Summary
The olive oil keeps unrivalled nutritional properties and health benefits, since its high content of monounsaturated fatty acids is concerned to strongly reduce the risk of heart disease, high blood pressure, and stroke [1]. Within the frame of implementation of eco-sustainable strategies, integrated membrane processes play a key role in the recovery of water with high degree of purity and bioactive compounds [4,5]. In the logic of integrated membrane systems, MF represents a first important clarification step for an effective low-pressure filtration of suspended contaminants such as sediments, colloidal particles, macromolecular agglomeration, and by-products of microorganism growth. The adhesion of colloids and dissolved organic substances takes place rapidly, reaching a steady-state condition, which can degenerate in an irreversible fouling. To contrast this event, expensive practices, such as Membranes 2017, 7, 66; doi:10.3390/membranes7040066 www.mdpi.com/journal/membranes
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