Removal of 17β-oestradiol and 17α-ethinyl oestradiol from water by activated carbons and hypercrosslinked polymeric phases

Study of the Potential of Water Treatment Sludges in the Removal of Emerging Pollutants

Presently, water quantity and quality problems persist both in developed and developing countries, and concerns have been raised about the presence of emerging pollutants (EPs) in water. The circular economy provides ways of achieving sustainable resource management that can be implemented in the water sector, such as the reuse of drinking water treatment sludges (WTSs). This study evaluated the potential of WTS containing a high concentration of activated carbon for the removal of two EPs: the steroid hormones 17β-estradiol (E2) and 17α-ethinylestradiol (EE2). To this end, WTSs from two Portuguese water treatment plants (WTPs) were characterised and tested for their hormone adsorbance potential. Both WTSs showed a promising adsorption potential for the two hormones studied due to their textural and chemical properties. For WTS1, the final concentration for both hormones was lower than the limit of quantification (LOQ). As for WTS2, the results for E2 removal were similar to WTS1, although for EE2, the removal efficiency was lower (around 50%). The overall results indicate that this method may lead to new ways of using this erstwhile residue as a possible adsorbent material for the removal of several EPs present in wastewaters or other matrixes, and as such contributing to the achievement of Sustainable Development Goals (SDG) targets.

Electrospun nanofibrous membranes of cellulose acetate containing hydroxyapatite co-doped with Ag/Fe: morphological features, antibacterial activity and degradation of methylene blue in aqueous solution

Cellulose acetate nanofiber membranes containing hydroxyapatite co-doped with Ag/Fe are effective towards the degradation of MB dye in aqueous solutions.

Steroid hormone micropollutant removal from water with activated carbon fiber-ultrafiltration composite membranes

Short activated carbon fibers (ACF) with high surface area were fabricated via carbonization in N₂ and activation in CO₂ at high temperatures, with cellulose fibers as the raw materials. The obtained ACF were subsequently deposited into the support layer of a polyethersulfone (PES) ultrafiltration membrane by a facile filtration process to obtain the sandwich structured ACF-PES composite membrane. The hormone (17β-estradiol, E2) adsorption kinetics and isotherm of ACF in static conditions, as well as E2 removal by filtration with the ACF-PES composite membrane were investigated. In static conditions, ACF rapidly and efficiently adsorbs E2 evidenced by a high removal of >97 %. The fitting of second order kinetics and linear (Henry) adsorption isotherm models indicated the availability of easily accessible adsorption sites. Besides, such efficient E2 adsorption was contributed by many interactions between E2 and ACF, namely hydrophobic interactions, hydrogen bonding and π-π stacking. The incorporation of ACF in a PES membrane resulted in a minor loss of filtration flux compared with the control membrane, but significantly improved E2 removal through adsorption pathway. With only 1.0 mg ACF incorporated (loading 2.0 g/m²), the composite membrane could reject 76 % of E2 from a 100 ng/L solution at a flux of 450 L/m²∙h, demonstrating that ACF-PES can overcome the permeability-selectivity trade-off of traditional UF membranes.

Adsorption of the harmful hormone ethinyl estradiol inside hydrophobic cavities of CTA(+) intercalated montmorillonite

Hydrophobic cavities produced by cetyltrimethylammonium cation (CTA(+)) exchanged and trapped in the interlayer space of montmorillonite were used to remove the harmful hormone contaminant ethinyl estradiol (EE2) from water. X-ray diffraction, thermogravimetry/derivative thermogravimetry, elemental analysis (carbon, hydrogen, nitrogen), Fourier transform infrared, scanning electron microscopy/energy dispersive spectroscopy, Brunauer-Emmett-Teller and contact angle analyses showed that the intercalation of 9, 16 and 34 wt% CTA(+) in the montmorillonite resulted in the d001 expansion from 1.37 to 1.58, 2.09 and 2.18 nm, respectively. EE2 adsorption experiments showed that the original clay montmorillonite does not remove EE2 from water whereas the intercalated composites showed high efficiency with adsorption capacities of 4.3, 8.8 and 7.3 mg g(-1) for M9CTA(+), M16CTA(+) and M34CTA(+), respectively. Moreover, experiments with montmorillonite simply impregnated with cetyltrimethylammonium bromide showed that the intercalation of CTA(+) to form the hydrophobic cavity is very important for the adsorption properties. Simple solvent extraction can be used to remove the adsorbed EE2 without significant loss of CTA(+), which allows the recovery and reuse of the adsorbent for at least five times.

Development of high efficiency silica coated β-cyclodextrin polymeric adsorbent for the removal of emerging contaminants of concern from water

This article reports the removal of several emerging contaminants (ECs) from water using novel adsorbent comprising of β-cyclodextrin (β-CD) coated on silica. Fourteen different adsorbents were synthesized under different experimental conditions using two different crosslinking agents (hexamethylene diisocyanate (HMDI) and epichlorohydrin (EPI)) and co-polymers (glycidoxypropyl trimethoxysilane (GPTS) and aminopropyl triethoxysilane (APTES). The adsorption capacities of the synthesized adsorbents were initially evaluated using 17β-estradiol, perfluorooctanoic acid (PFOA), and bisphenol-A (BPA) as adsorbates. The adsorbent prepared by using HMDI as crosslinking agent with DMSO as solvent was observed to perform the best, and removed more than 90% of 17β-estradiol, PFOA, and BPA. Furthermore, the β-CD loading on the ECs removal was studied which showed that the adsorbate removal increases with increase in loading of β-CD on the substrate. The best adsorbent was resynthesized in seven batches and its performance was reproducible for the removal of ten steroid hormones. The adsorbent showed very good regeneration potential for four successive adsorption-regeneration cycles to remove steroid hormones and PFOA. A plausible mechanism of adsorption is proposed. The synthesized best adsorbent is characterized using FTIR, HR-TEM, TGA and nitrogen adsorption analysis. The TGA results showed that the adsorbent has thermal stability of upto 300°C.

Efficient and versatile fibrous adsorbent based on magnetic amphiphilic composites of chrysotile/carbon nanostructures for the removal of ethynilestradiol

In this work, chrysotile was used as support to grow carbon nanotubes and nanofibers to produce fibrous amphiphilic magnetic nanostructured composites. Iron impregnated on the chrysotile surface at 1, 5 and 15 wt% was used as catalyst to grow carbon nanostructures by CVD (chemical vapor deposition) with ethanol at 800°C. Raman, TG/DTA, Mössbauer, XRD, BET, SEM, TEM, elemental analyses and contact angle measurements suggested the formation of a complex amphiphilic material containing up to 21% of nanostructured hydrophobic carbon supported on hydrophilic Mg silicate fibers with magnetic Fe cores protected by carbon coating. Adsorption tests for the hormone ethynilestradiol (EE), a hazardous water contaminant, showed remarkable adsorption capacities even compared to high surface area activated carbon and multiwall carbon nanotubes. These results are discussed in terms of the hydrophobic surface of the carbon nanotubes and nanofibers completely exposed and accessible for the adsorption of the EE molecules combined with the hydrophilic Mg silicate surface which allows good dispersion in water. The composites are magnetic and after adsorption the dispersed particles can be removed by a simple magnetic process. Moreover, the fibrous composites can be conformed as threads, screens and pellets to produce different filtering media.

Removal of ethinylestradiol (EE2) from water via adsorption on aliphatic polyamides

This study demonstrates the use of aliphatic polyamides (PAs) as efficient adsorbents for the removal of ethinylestradiol (EE2), a synthetic hormone and high-potency estrogenic contaminant, from water via strong adsorptive interactions. PA612 and PA12 showed significantly higher adsorption capacities than PA6 for EE2 adsorption from water. Isothermal adsorption studies showed that PA612 had an adsorption capacity for EE2 comparable to the benchmark macroreticular polymeric adsorbent, AMBERLTIE XAD4 (XAD4), despite its nonporous structure and far smaller surface area. The substantial adsorption of EE2 on PA612 is predominantly driven by Lewis acid-base interactions between EE2 and PA612 amide functionalities and facilitated by the hydrophobic partitioning of EE2 solutes in water. Rapid column adsorption tests demonstrated efficient removal of EE2 from water on a continuous flow basis. With an empty bed contact time of 0.8-1.0 min, the fixed-bed column with 1.0 g PA612 particles removed the EE2 from 24.1 L of 30 μg L(-1) EE2 spiked solution to non-detectable levels by HPLC analysis. Regeneration was readily effected by rinsing the exhausted column with 4 wt.% NaOH solution at room temperature. Regenerated PA612 particles showed consistent performance to fresh PA612 particles in subsequent batch and column adsorption studies.