Produced water (PW)
constitutes a massive environmental issue due
to its huge global production as well as its complexity and toxicity.
Membrane technology could, however, convert this complex waste stream
into an important source of water for reuse, but new and more efficient
membranes are required. In particular, in the last few years, polyelectrolyte
multilayers (PEMs) established themselves as a very powerful method
to prepare hollow fiber-based nanofiltration (NF) membranes, and this
membrane type and geometry would be ideal for PW treatment. Unfortunately,
the presence of surfactants in PW can affect the stability of polyelectrolyte
multilayers. In this work, we investigate the stability of polyelectrolyte
multilayers toward different types of surfactant, initially on model
surfaces. We find that chemically stable multilayers such as poly(diallyldimethylammonium
chloride) (PDADMAC)/poly(sodium 4-styrenesulfonate) (PSS), based only
on electrostatic interactions, are substantially desorbed by charged
surfactants. For poly(allylamine hydrochloride) (PAH)/PSS multilayers,
however, we demonstrate that chemical cross-linking by glutaraldehyde
leads to surfactant stable layers. These stable PEM coatings can also
be applied on hollow fiber support membranes to create hollow fiber
NF membranes dedicated for PW treatment. Increased cross-linking time
leads to more stable and more selective separation performance. These
newly developed membranes were subsequently studied for the treatment
of synthetic PW, consisting of freshly prepared oil-in-water emulsions
stabilized by hexade-cyltrimethylammonium bromide (CTAB) and sodium
dodecyl sulfate (SDS) in the presence of a mixture of ions. For both
types of produced water, the membranes show excellent oil removal
(∼100%) and organics removal (TOC reduced up to ∼97%)
as well as good divalent ion retentions (∼75% for Ca2+ and up to ∼80% for SO4
2–). Moreover, we observe a high flux
recovery for both emulsions (100% for CTAB and 80% for SDS) and especially
for the CTAB emulsion a very low degree of fouling. These stable PEM-based
hollow fiber membranes thus allow simultaneous deoiling and removal
of small organic molecules, particles, and divalent ions in a single
step process while also demonstrating excellent membrane cleanability.
In this research, ethyl cellulose films were prepared by a simple, easy, controlled one-pot method using either ethanol or ethyl lactate as solvents, the films being formed at 6 °C. Titanium dioxide nanoparticles were incorporated to improve the oxygen transmission and water vapour transmission rates of the obtained films. This method used no plasticizers, and flexible materials with good mechanical properties were obtained. The resulting solvent-free and transparent ethyl cellulose films exhibited good mechanical properties and unique free-shapable properties. The obtained materials had similar properties to those reported in the literature, where plasticizers were incorporated into ethyl cellulose films with an elastic modulus of 528 MPa. Contact angles showed the hydrophobic nature of all the prepared materials, with contact angles between 80 and 108°. Micrographs showed the smooth surfaces of the prepared samples and porous intersections with honeycomb-like structures. The oxygen and water vapor transmission rates were the lowest for the ethyl cellulose films prepared in ethyl lactate, these being 615 cm3·m−2·day−1 and 7.8 gm−2·day−1, respectively, showing that the films have promise for food packaging applications.
Wound-dressing materials often include other materials stimulating wound healing. This research describes the first formulation of biodegradable hybrid aerogels composed of polylactic acid and pectin. The prepared hybrid material showed a highly porous structure with a surface area of 166 ± 22.6 m2·g−1. The addition of polylactic acid may have decreased the surface area of the pure pectin aerogel, but it improved the stability of the material in simulated body fluid (SBF). The pure pectin aerogel showed a high swelling and degradation ratio after 3 h. The addition of the polylactic acid prolonged its stability in the simulated body fluid from 24 h to more than one week, depending on the amount of polylactic acid. Biodegradable aerogels were loaded with indomethacin and diclofenac sodium as model drugs. The entrapment efficiencies were 63.4% and 62.6% for indomethacin and diclofenac sodium, respectively. Dissolution of both drugs was prolonged up to 2 days. Finally, sodium percarbonate and calcium peroxide were incorporated into the bioaerogels as chemical oxygen sources, to evaluate oxygen generation for potential wound healing applications.
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