Real Water Matrices Research Articles

Photocatalytic hydrogen production and sulfamerazine degradation via a novel dual S-scheme photocatalyst: Nanocomposite synthesis, characterization and mechanism insights

Creating highly effective photocatalysts is crucial for harnessing solar energy to degrade pollutants and produce hydrogen (H₂). In this study, we successfully synthesized a novel dual S-scheme iron oxide (Fe₂O₃)/bismuth oxide (Bi₂O₃)/titanium dioxide (TiO₂) ternary photocatalyst using a straightforward method. This photocatalyst was employed for efficient photocatalytic water splitting and the degradation of the antibiotic sulfamerazine (SMZ) under visible light. Various characterization and photoelectrochemical techniques, including scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Brunauer–Emmett–Teller surface area analysis (BET), photocurrent measurements, Mott-Schottky analysis, photoluminescence (PL), electrochemical impedance spectroscopy (EIS), and electron spin resonance (ESR), were utilized to analyze the synthesized materials. Among the synthesized nanocomposites, the 15 wt% Fe₂O₃/Bi₂O₃/TiO₂ (15FeBi/TiO₂) composite demonstrated exceptional photocatalytic efficiency, achieving 98 % SMZ degradation and a hydrogen production rate of 590.36 μmol/g·h. Experimental results, including scavenging tests and ESR findings, highlighted the crucial role of hydroxyl radicals (•OH) and superoxide radicals (•O₂−) in the photocatalytic process. Moreover, liquid chromatography-mass spectrometry (LC-MS) results proposed three degradation pathways, and quantitative structure-activity relationship (QSAR) analysis showed that the toxicity of intermediates was effectively reduced. The 15FeBi/TiO₂ photocatalyst also exhibited excellent reusability, retaining about 85 % of its initial activity after five cycles, and proved effective against various pollutants and in real water matrices. This research contributes to the design and development of high-activity heterojunction photocatalysts for superior clean energy generation and pollutant degradation under visible light.

Efficient Electrocatalytic Hydrodechlorination and Detoxification of Chlorophenols by Palladium-Palladium Oxide Heterostructure.

Electrocatalytic hydrodechlorination is a promising approach for simultaneous pollutant purification and valorization. However, the lack of electrocatalysts with high catalytic activity and selectivity limits its application. Here, we propose a palladium-palladium oxide (Pd-PdO) heterostructure for efficient electrocatalytic hydrodechlorination of recalcitrant chlorophenols and selective formation of phenol with superior Pd-mass activity (1.35 min-1 mgPd-1), which is 4.4 times of commercial Pd/C and about 10-100 times of reported Pd-based catalysts. The Pd-PdO heterostructure is stable in real water matrices and achieves selective phenol recovery (>99%) from the chlorophenol mixture and efficient detoxification along chlorophenol removal. Experimental results and computational modeling reveal that the adsorption/desorption behaviors of zerovalent Pd and PdO sites in the Pd-PdO heterostructure are optimized and a synergy is realized to promote atomic hydrogen (H*) generation, transfer, and utilization: H* is efficiently generated at zerovalent Pd sites, transferred to PdO sites, and eventually consumed in the dechlorination reaction at PdO sites. This work provides a promising strategy to realize the synergy of Pd with different valence states in the metal-metal oxide heterostructure for simultaneous decontamination, detoxification, and resource recovery from halogenated organic pollutants.

Molecular insights into pilot-scale selective removal of emerging contaminants in hospital wastewater

Advanced oxidation processes (AOPs) are a promising technology for removing emerging organic contaminants (EOCs) from wastewater, while the coexisting dissolved organic matter (DOM) significantly hinders effective oxidative removal of EOCs. Understanding the effects of DOM on EOCs removal in real water matrices is crucial for designing more efficient AOPs. Herein, a pilot-scale integrated in-situ ozonation/ultrafiltration process was conducted to remove EOCs from hospital wastewater. Furthermore, the ozonation reactivity of DOM and EOCs was contrastingly analyzed at the molecular level. Our integrated process selectively removed 85 % of EOCs at a relatively low oxidant dosage of 0.44 mg O3 per mg dissolved organic carbon (DOC). Using Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS), we reveal that ozone selectivity for EOCs arose from their overall reductive characteristics of being more aromatic and unsaturated in molecular composition compared to DOM. Additionally, specific DOM compounds potentially facilitate EOCs removal. This work provides pilot-scale experience in EOCs removal from hospital wastewater and in-depth understanding of DOM’s role in the integrated process, guiding the development of effective AOPs for selective removal of emerging contaminants.

Photo-Fenton-like activity of Fe/ZnO structure applied as a heterogeneous catalyst for the methylene blue dye removal in aqueous matrices

This work developed efficient heterogeneous catalysts for the methylene blue (MB) dye degradation under photo-Fenton-like conditions. The material was modified to incorporate Fe(III) into ZnO, creating Fe/ZnO strucuture, and applied as heterogeneous catalysts at various pH levels. SEM analysis revealed an agglomerated and plate-like morphology of the synthesized catalysts. The enhanced structure facilitated a removal efficiency of 96.2% for MB dye when employing the photo-Fenton-based process using 5.0% Fe/ZnO catalyst. The high removal efficiency is attributed to the synergy between ≡Fe(III) and ≡Zn(II), which promotes the generation of photoradical species through the Fenton effect. Real water matrices served as a source of MB dye contamination, exhibiting minimal interference and achieving ∼100 % of removal. Scavenger studies indicate that •OH and e⁻ are the primary contributors to the high MB dye degradation efficiency. Additionally, the by-products formed after photo-Fenton process exhibit minimal toxicity towards Lactuca sativa L. No Fe(II) ions were leached at the end of the process. Eight cycles of degradation did not cause significant spectral changes in the FTIR analysis, as well as in the XRD patterns, indicating the material efficient and stable structure.

Photoactivation of sulfite by FeTiO3 for organic pollutant degradation: Performance and mechanism

In recent years, the exploration of sulfite (S(IV))-based advanced oxidation processes has attracted increasing attention due to its high performance in the degradation of aqueous organic contaminants. In this study, we investigated the activation of S(IV) by ilmenite (FeTiO3) under photo irradiation using phenol as a substrate. The FeTiO3/S(IV)/photo system demonstrated a remarkable phenol removal rate, achieving 81.4 % degradation within 30 min under optimal conditions. The photocatalytic mechanism involves the generation of electron-hole pairs in FeTiO3, with photogenerated holes activating the adsorbed S(IV) on the catalyst’s surface to produce various free radicals, among which SO4− is identified as the primary active species. Density functional theory calculations further suggest that electron transfer between ilmenite and S(IV) may occur via a Fe-O-S bridge. Additionally, the approach demonstrates satisfactory reusability of the photocatalyst and consistent effectiveness in real-water matrices. This study contributes to the development of more efficient, cost-effective, and environmentally friendly water treatment strategies by providing a deeper understanding of the proposed FeTiO3/S(IV)/photo system.

Reduced graphene oxide foams modified with caffeic acid for water decontamination: Capture and safe storage of Hg2+

Graphene-based materials are attractive adsorbents for water decontamination. In this work, we have produced eco-friendly reduced graphene oxide (rGO)-based sorbents by the hydrothermal reduction of graphene oxide (GO) in presence of caffeic acid (CA) and further modification with chitosan (CA_CS). Scanning electron microscopy observations show porous macrostructures that turn more compact after CA or CA_CS modification. The specific surface area achieves a maximum value of 293 m2 g−1 for the pristine rGO foam. The macropores are mainly distributed in a range between 1–170 µm. The Hg2+ removal efficiency of the rGO-based foams was investigated across several different parameters. The foam modified with caffeic acid exhibited the most promising performance, demonstrating the highest removal efficiency at pH 4–6, with a maximum sorption capacity of 2.79 mg/g as determined by the Sips equation. Kinetic analysis indicates that intraparticle diffusion and the sorption itself are the rate-limiting steps. The notable sorption efficiency, the low desorption rate, and the applicability in real complex water matrices, including tap water, position rGO_CA as a viable material for efficiently capturing Hg(II) from large volumes of water and securely storing it in a small solid volume.

Scaling-up the use of macroscopic photo-CWPO La1-xTixFeO3/SiC alveolar foam catalyst for solar water treatment against micropollutants

Current wastewater treatment plants are not prepared for the removal of micropollutants like phenol, pharmaceuticals and pesticides in water. As their release into the environment has adverse consequences towards the living organisms of ecosystems, the engineering of novel sustainable processes able to ultimately remove the emerging organic contaminants is an objective of paramount importance. Hereby we report for the first time on the successful scale-up of a macroscopic photo-CWPO La1-xTixFeO3/SiC alveolar foam catalyst used at the pilot-plant scale inside a Compound Parabolic Collectors based photoreactor. The removal of a span of organic micropollutants in water matrices of different complexity was efficiently realized under natural solar radiation using H2O2 or persulfates as oxidizing agent. The water matrix composition affected the efficiency of the degradation process. Using H2O2, for a collected energy of ca. 27 KJ/mol, the rate of micropollutant removal ranged from 53 % to 95 % in distilled water depending on the micropollutant in a cocktail configuration. It was lowered to the 17–66 % range in tap water, and to the 8–42 % range in simulated urban wastewater. The results demonstrated the promise of using sodium persulfate as oxidant instead of H2O2, with a better efficiency towards the removal of most of the micropollutants tested. The use of the sodium persulfate oxidant allows for overcoming the drawbacks associated to the treatment of real water matrices observed using H2O2, as better performances were reached when increasing the water matrix complexity. Complete removal of carbamazepine and diclofenac micropollutants was reached in tap water and simulated urban wastewater for ca. 27 KJ/mol of collected energy. The degradation performances combined to the catalyst robustness make this water treatment technology promising for operating in a continuous way under natural solar light.

Removal of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) by coagulation: Influence of coagulant and dosing conditions

Per- and polyfluoroalkyl substances (PFAS) pose significant risks to the environment and human health. Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) are two of the most frequently detected PFAS in the environment. In most surface water drinking water treatment works (WTW), coagulation is the first processes exposed to a range of contaminants, including PFAS. While not designed to be a process for removal of micropollutants, it is important to understand the fate of PFAS in coagulation processes, intended or otherwise, to determine whether water treatment sludge can be a significant sink for this group of micropollutants. This work advances understanding of PFAS removal in coagulation processes by comparing the removal of PFOA and PFOS by four metal coagulants (Zr, Zn, Fe, and Al) from real water matrices. The coagulant performance followed the order Al > Fe > Zr > Zn. Al was taken forward for further evaluation, with significant removal of PFAS (>15 % for PFOA and > 30 % for PFOS) being observed when the pH<5.5 and the dose was > 5 mg Al·L-1. The adsorption of PFOA and PFOS onto flocs through hydrophobic interaction was the primary removal route. The impacts of background matrix on the mechanisms of coagulation for PFAS were explored using five organic compounds. Macromolecular organic compounds contributed to an increase in removal due to the sorption of PFAS and subsequent removal of the organic-PFAS aggregate during coagulation. Low molecular weight organic matter inhibited the removal of PFAS due to the ineffective removal of these compounds during coagulation.

Insight into the impact of environmental factors on heavy metal adsorption by sodium alginate hydrogel: Inspiration on applicable scenarios

Sodium alginate (SA) emerges as a promising adsorbent for the remediation of heavy metal-polluted wastewater. However, the systematic investigations on how and the extent to which the various compositions in real water matrices impact its performance were essential but rare when considering its use. Here, we explored the effect of common environmental factors on Cu(II) adsorption by an as-synthesized SA-based hydrogel (SAH). The result showed that high concentration of organics (above 10 mg L−1) had a negative influence on heavy metal removal (decreased by 9.45 % at least), while inorganic ion, turbidity and antibiotics at relatively low concentrations exhibited a negligible even promoting effect (increased by 9.8 % with the presence of 5 mg L−1 Nor). Based on above results and corresponding mechanism analyses, the possible applicable and unsuitable scenarios of SAH can be predicted. SAH could be a great candidate for treating heavy metal-polluted water such as river and lake water, while it is not a good option for electroplating or livestock wastewater which contains high concentration of organic matters. Besides, the operating conditions including pH (5.0 for Cu(II), 6.0 for Ni(II)), contact time (24 h), temperature (298 K) et al. were also determined. Overall, this work provides theoretical guidance and operational strategies for promoting the practical application of SA adsorbent in water treatment.

Post-calcination as an effective approach to enhance adsorption of arsenic and antimony anions by Mg/Al layered double hydroxide-decorated spent coffee ground biochars: Role of charge properties and active sites

This study evaluated the effects of post-calcination on the charge properties and active sites of Mg/Al layered double hydroxide-decorated spent coffee ground biochars (LDHMgAl@SCGB) governing adsorption behaviors and mechanisms of arsenic (AsV) and antimony (SbV) anions from aqueous phases. Post-calcinated LDHMgAl@SCGB (PLDHMgAl@SCGB) exhibited higher adsorption capacities for AsV and SbV compared to spent coffee ground biochars (SCGB) and LDHMgAl@SCGB as post-calcination of LDHMgAl@SCGB enhanced the charge properties (surface zeta potential at pH 7.0: SCGB = −21.8 mV, LDHMgAl@SCGB = 28.5 mV, and PLDHMgAl@SCGB = 34.4 mV) and increased active sites by eliminating the anions (i.e., Cl− ions) and water molecules at its interlayers. The calculated kinetic, intra-particle diffusion, and isotherm parameters indicated that the chemisorption and intra-particle diffusion were mainly responsible for the adsorption of AsV and SbV by SCGB, LDHMgAl@SCGB, and PLDHMgAl@SCGB. Moreover, post-calcination of LDHMgAl@SCGB enhanced its selectivity toward AsV and SbV by reinforcing the electrostatic surface complexation via its improvement of charge properties. Since PLDHMgAl@SCGB exhibited the excellent reusability for the adsorption of AsV (reuse efficiency >63.6%) and SbV (reuse efficiency >52.1%), it can be concluded that post-calcination of LDHMgAl@SCGB is a promising method for improving the adsorption capacities for AsV and SbV in real water matrices.

Current Challenges in Monitoring Low Contaminant Levels of Per- and Polyfluoroalkyl Substances in Water Matrices in the Field.

The Environmental Protection Agency (EPA) of the United States recently released the first-ever federal regulation on per- and polyfluoroalkyl substances (PFASs) for drinking water. While this represents an important landmark, it also brings about compliance challenges to the stakeholders in the drinking water industry as well as concerns to the general public. In this work, we address some of the most important challenges associated with measuring low concentrations of PFASs in drinking water in the field in real drinking water matrices. First, we review the "continuous monitoring for compliance" process laid out by the EPA and some of the associated hurdles. The process requires measuring, with some frequency, low concentrations (e.g., below 2 ppt or 2 ng/L) of targeted PFASs, in the presence of many other co-contaminants and in various conditions. Currently, this task can only (and it is expected to) be accomplished using specific protocols that rely on expensive, specialized, and laboratory-scale instrumentation, which adds time and increases cost. To potentially reduce the burden, portable, high-fidelity, low-cost, real-time PFAS sensors are desirable; however, the path to commercialization of some of the most promising technologies is confronted with many challenges, as well, and they are still at infant stages. Here, we provide insights related to those challenges based on results from ab initio and machine learning studies. These challenges are mainly due to the large amount and diversity of PFAS molecules and their multifunctional behaviors that depend strongly on the conditions of the media. The impetus of this work is to present relevant and timely insights to researchers and developers to accelerate the development of suitable PFAS monitoring systems. In addition, this work attempts to provide water system stakeholders, technicians, and even regulators guidelines to improve their strategies, which could ultimately translate in better services to the public.

Boosted photo-Fenton-like process for selective degradation of emerging contaminants by dehydrated Fe-based metal–organic framework with thermodynamically-favorable center metal electron density and confinement effect

The Heterogeneous Fenton reaction has long stood out as a highly effective technology for water purification. However, it is nowadays facing challenges such as low selectivity, sluggish Fe(III) reduction, and limited H2O2 conversion efficiency. Herein, dehydrated MIL-100(Fe)-250 was synthesized through thermal treatment, demonstrating superior efficiency in removing emerging contaminants, with a three-fold efficiency higher than undehydrated sample. The dehydrated MIL-100(Fe)-250 exhibited selective acceleration in the removal of quinolones and phenolic organics, rendering the system resistant to interference from coexisting matter. Through in-situ diffuse reflectance infrared Fourier-transform spectroscopy and density functional theory calculation, it was manifested that dehydration process regulates the steric hindrance and local electron density of Fe ions. This adjustment enhances charge transfer, thereby facilitating Fe(III) reduction and promoting the H2O2 activation and conversion efficiency. Moreover, the quasi-steady-state concentrations of hydroxyl radical in MIL-100(Fe)-250 were found to be 2.2 times higher than that those in undehydrated sample. Impressively, the dehydrated MIL-100(Fe)-250 displayed adaptability across a broad pH range of 5.0–9.0. The present study underscores the significant potential of porous MIL-100(Fe)-250 with spatial confinement, which imparts a clear size exclusion effect. As a result, this catalyst emerges as a promising candidate for eliminating contaminants in real water matrices, offering a viable strategy for water pollution control.

Impacts of experimental parameters and natural water matrix on the elimination of ranitidine from water by emulsion liquid membrane

Ranitidine (RAN) is one of the most commonly recommended medications because it effectively reduces the amount of acid produced in the stomach, is persistent in aqueous solutions, and is nonbiodegradable. Hence, the goal of this study is to use emulsion liquid membrane (ELM), an advanced separation technique, to eliminate RAN from aqueous media. The components of the ELM system include sulfuric acid as the internal receiving solution, kerosene as the diluent, Span 80 as the emulsifier, and D2EHPA as the extractant. The effects of operating conditions were examined. A metastable emulsion with complete drug elimination, i.e., 100 %, from the aqueous contaminated phase was obtained after 60 min at an emulsifier concentration of 3 % (w/w), extractant concentration of 3.2 % (w/w), kerosene as diluent, internal receiving solution concentration of 0.2 N sulfuric acid, emulsification speed of 20,000, emulsification time of 4 min, stirring rate of 300 rpm, volume ratio of receiving solution to membrane of 1/1, volume ratio of emulsion to feed solution of 20/200 and initial RAN concentration ≤ 20 mg/L. Excellent extraction efficiency was achieved even at the initial RAN concentration interval of 5 −100 mg/L. The permeation of RAN from various real water matrices was also investigated. For the purpose of RAN extraction from water, the implemented ELM system provides an interesting advanced separation technique.

Acetaminophen removal by peroxymonosulfate catalyzed by C and O co-doped graphitic carbon nitride in synthetic secondary treatment effluent matrix

Catalytic oxidation using carbonaceous materials and peroxymonosulfate (PMS) has attracted attention because of high potential in pharmaceuticals removal. For successful field applications, it is essential to identify the components and characteristics in real water matrices affecting the performance, though it has hardly been elaborated. Therefore, acetaminophen (ACT) removal by C and O co-doped graphitic carbon nitride (COCN) and PMS was investigated in synthetic secondary treatment effluent (SSTE) and compared to that in deionized water (DIW). ACT removal was significantly suppressed in SSTE (20.33 %) compared to that in DIW (94.20 %) under 10 mg/L ACT, 100 mg/L COCN, and 0.5 mM PMS. However, it was enhanced greatly with increasing COCN and/or PMS dose. The reactive species were the same in SSTE and DIW, of which 1O2 from O2− dominantly contributed. However, the amount of them was considerably lower in SSTE than in DIW. ACT removal was slightly affected by the anions in SSTE, such as Cl−, SO42−, and NO3−, at 1.41 × 10−3–0.71 mM. But it was suppressed greatly by 0.71 mM phosphates and by 10 mg/L humic acid and natural organic matter, via consuming hydrophobic and aromatic fractions. It is strongly suggested that the reactivity of COCN/PMS in SSTE was dominantly affected by raised pH and scavenging O2− reducing DOM, which decreased 1O2 generation. The results would significantly contribute to successful practical applications of catalytic systems.

A high-flux atomically dispersed MIL-100 (Fe) incorporated PMS-based LDH catalytic membrane for the removal of micropollutants from secondary effluent wastewater

This study fabricated a CoFe layered double hydroxide (CoFeLDH) membrane incorporating the metal–organic framework (MOF) MIL(100)Fe, tailored for a peroxymonosulfate (PMS) based system. Among various combinations of MOF and LDH nanosheets on a PVDF substrate, the highest water flux, reaching 1900 L/m2/hr/bar, was achieved with an LDH/MOF ratio of 5:1 and an MOF concentration of 0.025 M. The optimized membrane exhibited exceptional performance, achieving 99 % degradation of ranitidine at 0.1 mM PMS. The LDH MOF catalytic membrane exhibited excellent treatment performance in real water matrices and demonstrated long-term operational efficiency. The effective removal of ranitidine by this catalytic membrane was attributed to a synergistic combination of radical (SO4− and OH) and non-radical (singlet 1O2 and electron transfer O2) oxidation pathways, with SO4− and singlet 1O2 playing a predominant role. Post-activation, 40 % of surface Co2+ and 65 % of Fe2+ in the LDH MOF membrane were found in the + III oxidation state, highlighting the significance of metal catalytic sites and the reusability potential of the membrane. The durability of the membrane was evident through 10 cycles, achieving a flux recovery ratio of 95 % in the first cycle and sustaining efficient performance across pH variations (3 to 9) and exposure to various anions. Importantly, negligible metal leaching was observed for the real water samples, ensuring suitability for large-scale applications.

Designing of MOF@COF with enhanced removal performance for parabens: Fast adsorption plus built-in heterojunction facilitated photocatalysis

With the widespread use of parabens as preservatives, their increasing environmental concentration and potential adverse heathy effects have drawn considerable concern. Photodegradation represents a sustainable approach for paraben removal; however, developing photocatalysts that exhibit both efficient visible-light absorption and effective separation of photocarriers remains a challenge. Herein, a MOF@COF core-shell structure was fabricated to utilize the heterojunction for charge-hole spatial separation, generating sufficient reactive species for the photodegradation process. Under visible light, TPTi-0.225 (i.e., 0.225 g NH2-MIL-125 was added during COF synthesis) catalyzed highly efficient removal (∼99 %) of propylparaben within two hours. The degradation performance of TPTi-0.225 over a wide pH range and various real water matrices was also satisfactory. Theoretic calculation along with key reaction intermediate identification revealed parabens were degraded into low-toxicity products. This study not only offers insight into the design of novel visible photocatalysts but also presents a viable approach for detoxifying parabens in environmental waters.

Achieving realistic ozonation conditions with synthetic water matrices comprising low-molecular-weight scavenger compounds

Ozonation is used worldwide for drinking water disinfection and increasingly also for micropollutant abatement from wastewater. Identification of transformation products formed during the ozonation of micropollutants is challenging due to several factors including (i) the reactions of both oxidants, ozone and hydroxyl radicals with the micropollutants, as well as with intermediate transformation products, (ii) effects of the water matrix on the ozone and hydroxyl radical chemistry and (iii) the generation of oxidation by-products. In this study, a simple approach to achieve realistic ozonation conditions in the absence of dissolved organic matter has been developed. It is based on composing synthetic water matrices with low-molecular-weight scavenger compounds (phenol, methanol, acetate, and carbonate) that mimic the chemical interactions of ozone and hydroxyl radicals with real water matrices. Synthetic waters composed of only four low-molecular-weight compounds successfully replicated two lake waters and two secondary wastewater effluents, matching instantaneous ozone demand, ozone and hydroxyl radical exposures in the initial phase, as well as the ozone evolution in the second phase of the ozonation process. The synthetic water matrices also reproduced the effects of temperature and pH changes observed in real waters. The abatement of two micropollutants, bezafibrate and atrazine, and the formation of the corresponding transformation products during ozonation were in agreement for synthetic and real waters. Furthermore, the kinetics and extent of bromate formation during ozonation in synthetic water were comparable to real lake water and wastewater. This supports the robustness of the proposed approach because bromate formation is very sensitive to the interplay of ozone and hydroxyl radicals. Furthermore, with the novel reaction system, a significant effect of hydroxyl radicals scavenging by carbonate on bromate formation was demonstrated. Overall, the herein-developed approach based on synthetic water matrices allows to perform realistic ozonation studies including both oxidants, ozone and hydroxyl radicals, without the constraints of using dissolved organic matter.

Perfluoroalkyl acid adsorption by styrenic β-cyclodextrin polymers, anion-exchange resins, and activated carbon is inhibited by matrix constituents in different ways

Perfluoroalkyl acids (PFAAs) are ubiquitous environmental contaminants of global concern, and adsorption processes are the most widely used technologies to remove PFAAs from water. However, there remains little data on the ways that specific water matrix constituents inhibit the adsorption of PFAAs on different adsorbents. In this study, we evaluated the adsorption of 13 PFAAs on two styrene-functionalized β-cyclodextrin (StyDex) polymers, an activated carbon (AC), and an anion-exchange resin (AER) in the absence and presence of specific water matrix constituents (16 unique water matrices) in batch experiments. All four adsorbents exhibited some extent of adsorption inhibition in the presence of inorganic ions and/or humic acid (HA) added as a surrogate for natural organic matter. Two PFAAs (C5-C6 perfluorocarboxylic acids (PFCAs)) were found to exhibit relatively weak adsorption and five PFAAs (C6-C8 perfluorosulfonic acids (PFSAs) and C9-C10 PFCAs) were found to exhibit relatively strong adsorption on all four adsorbents across all matrices. Adsorption inhibition was the greatest in the presence of Ca2+ (direct site competition) and HA (direct site competition and pore blockage) for AC, NO3- (direct site competition) and Ca2+ (chemical complexation) for the AER, and SO42- (compression of the double layer) for the StyDex polymers. The pattern of adsorption inhibition of both StyDex polymers were similar to each other but different from AC and AER, which demonstrates the distinctive PFAA adsorption mechanism on StyDex polymers. The unique performance of each type of adsorbent confirms unique adsorption mechanisms that result in unique patterns of adsorption inhibition in the presence of matrix constituents. These insights could be used to develop models to predict the performance of these adsorbents in real water matrices and afford rational selection of adsorbents based on water chemistry for specific applications.

MOF-on-MOF-derived Fe[sbnd]Zr bimetal oxides supported on hierarchically porous carbonized wood to promote photo-Fenton degradation of ciprofloxacin

MOF-on-MOF derivatives have served as promising heterogeneous Photo-Fenton (hetero-PF) catalysts, but its self-aggregation instability and limited photocatalytic activity inhibit the effective ciprofloxacin (CIP) removal. In this study, a novel hetero-PF catalyst, dual MOF-derived FeZr bimetal oxide embedded in a wood-converted porous carbon skeleton (ZrO2@Fe3O4/WPC), was successfully synthesized via a straightforward in-situ growth strategy combined with co-pyrolysis. The as-prepared hybrid photocatalysts, featuring a large surface area, effective porous structures, efficient light absorption and a narrow band gap demonstrated superior photo-Fenton activity, accomplishing approximately 99.1 % degradation of CIP within 120 min under neutral conditions. Furthermore, the ZrO2@Fe3O4/WPC hetero-PF system showed satisfactory performance in treating real water matrices. It can be inferred that the abundant heterojunctions, resulting from the synergistic effect of FeZr mixed oxide and the porous carbonized wood substrate, contributed to the rapid separation and migration of photogenerated electron-hole pairs. Meanwhile, the FeZr site in the graphitized carbon framework activates H2O2 to accelerate the generation of the OH and O2− radicals, leading to a heightened degradation efficiency of CIP. Besides, the photodegradation pathway of CIP is obtained by liquid chromatography-mass spectrometry (LC-MS). This study indicates that combining porous carbonized wood and heterometallic MOF derived materials provides a promising method for realizing high-efficiency photo-Fenton degradation of antibiotic water pollutions.

Evaluating synergy of dual-wavelength deep-UV radiation (222 + 282 nm) for synchronous water decontamination and disinfection

This study is the first to explore a potential synergy of deep dual-wavelength ultraviolet (DWUV) radiation of KrCl (222 nm) and XeBr (282 nm) excilamps towards synchronous elimination of bacteria (105 CFU/mL E. coli and E. faecalis) and pharmaceutical (20 μM bezafibrate) from model and real (natural) water matrices at unadjusted pH. A time-based synergistic effect of DWUV photolysis and DWUV+H2O2 process in terms of 5-log (total) inactivation was found under all experimental conditions with synergistic indices in the range of 1.3–3.9. In the absence of bezafibrate, no inhibition effect of natural water matrix was found for inactivating bacteria by DWUV radiation with and without H2O2. Adding bezafibrate inhibited inactivation in natural water with keeping a synergistic effect and low dose requirements for complete inactivation (below 6 mJ/cm2). Despite the absence of synergistic effect towards degradation of bezafibrate, its synchronous degradation is achievable at higher doses. Unlike inactivation, the pseudo-first-order rate constants showed that degradation was inhibited by water matrix and bacteria (to a lesser degree) in DWUV+H2O2 mode, but not under DWUV photolysis. However, the DWUV+H2O2 process was more efficient than direct photolysis and provided faster decontamination and disinfection. Results show that this advanced oxidation process is applicable for treating real water matrices and represent a promising strategy in controlling microbial pathogens and pharmaceuticals in water.