Adsorption Of Micropollutants Research Articles

Modelling competitive adsorption of organic micropollutants onto powdered activated carbon in continuous stirred tank reactors for advanced wastewater treatment

This work investigates the validation and application of a competitive model approach for full-scale wastewater treatment plants (WWTP) with external recirculation of partially loaded powdered activated carbon (PAC) for removal of organic micropollutants (OMP). It is based on the ideal adsorbed solution theory (IAST) for multisolute mixtures combined with calibration of fictive organic components and correction of single-solute model parameters for OMP by use of the tracer model (TRM). Adsorption kinetics are represented by a pseudo first order reaction (PFO) and compared to mass transfer calculated with the homogenous surface diffusion model (HSDM). Model validation with operational data from two different WWTPs showed a strong dependency of model results on the batch sample quality used for model calibration. In contrast, the kinetic approach is of less importance for predicting full-scale OMP removal with long PAC sludge retention times. Further model application demonstrated that external PAC recirculation significantly improves the OMP removal with regard to both adsorption capacity and compensation of competitive effects of Dissolved Organic Carbon (DOC).

Deciphering the role of extracellular polymeric substances in the adsorption and biotransformation of organic micropollutants during anaerobic wastewater treatment

Extracellular polymeric substances (EPS) participate in the removal of organic micropollutants (OMPs), but the primary pathways of removal and detailed mechanisms remain elusive. We evaluated the effect of EPS on removal for 16 distinct chemical classes of OMPs during anaerobic digestion (AD). The results showed that hydrophobic OMPs (HBOMPs) could not be removed by EPS, while hydrophilic OMPs (HLOMPs) were amenable to removal via adsorption and biotransformation of EPS. The adsorption and biotransformation of HLOMPs by EPS accounted up to 19.4 ± 0.9 % and 6.0 ± 0.8 % of total removal, respectively. Further investigations into the adsorption and biotransformation mechanisms of HLOMPs by EPS were conducted utilizing spectral, molecular dynamics simulation, and electrochemical analysis. The results suggested that EPS provided abundant binding sites for the adsorption of HLOMPs. The binding of HLOMPs to tryptophan-like proteins in EPS formed nonfluorescent complexes. Hydrogen bonds, hydrophobic interactions and water bridges were key to the binding processes and helped stabilize the complexes. The biotransformation of HLOMPs by EPS may be attributed to the presence of extracellular redox active components (c-type cytochromes (c-Cyts), c-Cyts-bound flavins). This study enhanced the comprehension for the role of EPS on the OMPs removal in anaerobic wastewater treatment.

Novel fibrous Ag(NP) decorated clay-polymer composite: Implications in water purification contaminated with predominant micro-pollutants and bacteria

Due to the potential harm caused by emerging micro-pollutants to living organisms, contaminating water supplies by micro-pollutants like EDCs, pharmaceuticals, and microorganisms has become a concern in many countries. Considering both microbiological and micro-pollutant exposure risks associated with water use for agricultural/or household purposes, it is imperative to create a strategy for improving pollutant removal from treated wastewater that is both effective and affordable. Natural clay minerals efficiently remove contaminants from wastewater, though the pristine clay has less affinity to several organic pollutants. Hydrophilic polymers, viz., poly(ethylene glycol) (PEG), improve the dispersion of particles, flocculation processes, and surface properties. In this study, PEG grafted with attapulgite, thereby providing a high-specific surface-area, mesoporous materials for the adsorption of micro-pollutants like ciprofloxacin (CIP) and 17α-ethinylestradiol (EE2) at high rates. A gentle washing process regenerates the clay-polymer material several times with no performance loss, and the natural water implications show fair applicability of solid in decontaminating the CIP and EE2 in an aqueous medium. Further, greenly synthesized silver nanoparticles in situ disperse with the clay polymer efficiently remove the gram-positive and gram-negative bacterium viz., Bacillus subtilis, and Pseudomonas aeruginosa, which are commonly persistent in aquatic environments. The clay polymer outperformed a modified clay composite to eliminate microorganisms and organic micro-pollutants in significant quantities quickly. These results clearly show the importance of fibrous clay-polymer composite for water purification technologies.

Comparing the adsorption of micropollutants on activated carbon from anaerobically stored, organics-depleted, and nitrified urine

Separate collection and treatment of urine optimizes nutrient recovery and enhances micropollutant removal from municipal wastewater. One typical urine treatment train includes nutrient recovery in three biological processes: anaerobic storage, followed by aerobic organics degradation concurrently with nitrification. These are usually followed by activated carbon adsorption to remove micropollutants. However, removing micropollutants prior to nitrification would protect nitrifiers from potential inhibition by pharmaceuticals. In addition, combining simplified biological treatment with activated carbon adsorption could offer a cheap and robust process for removing micropollutants where nutrient recovery is not the first priority, as a partial loss of ammonia occurs without nitrification. In this study, we investigated whether activated carbon adsorption could also take place between the three biological treatment steps. We tested the effectiveness of micropollutant removal with activated carbon after each biological treatment step by conducting experiments with anaerobically stored urine, organics-depleted urine, and nitrified urine. The urine solutions were spiked with 19 pharmaceuticals: amisulpride, atenolol, atenolol acid, candesartan, carbamazepine, citalopram, clarithromycin, darunavir, diclofenac, emtricitabine, fexofenadine, hydrochlorothiazide, irbesartan, lidocaine, metoprolol, N4-acetylsulfamethoxazole, sulfamethoxazole, trimethoprim, venlafaxine, and two artificial sweeteners, acesulfame and sucralose. Batch experiments were conducted with powdered activated carbon (PAC) to determine how much activated carbon achieve which degree of micropollutant removal and how organics, pH, and speciation change from ammonium to nitrate influence adsorption. Micropollutant removal was also tested in granular activated carbon (GAC) columns, which is the preferred technology for micropollutant removal from urine. The carbon usage rates (CUR) per person were lower for all urine solutions than for municipal wastewater. The results showed that organics depletion would be needed when micropollutant removal was the sole aim of urine treatment, as the degradation of easily biodegradable organics prevented clogging of GAC columns. However, CUR did hardly improve with organics-depleted urine compared to stored urine. The lowest CUR was achieved with nitrified urine. This resulted from the additional organics removal during nitrification and not the lower pH or the partial conversion of ammonium to nitrate. In addition, we showed that the relative pharmaceutical removal in all solutions was independent of the initial pharmaceutical concentration unless the background organics matrix changed considerably. We conclude that removal of micropollutants in GAC columns from organics-depleted urine can be performed without clogging, but with the drawback of a higher carbon usage compared to removal from nitrified urine.

Comparing different versions of the Yoon-Nelson model in describing organic micropollutant adsorption within fixed bed adsorbers.

The Yoon-Nelson model serves as a widely used tool for describing the breakthrough behavior of organic micropollutants within fixed bed adsorbers. This study aims to augment its modeling efficacy through two proposed refinements found in the literature: a logarithmic transformation and the incorporation of steric hindrance effects. We systematically evaluated the original Yoon-Nelson model alongside the modified versions, using breakthrough data associated with micropollutant adsorption on solid materials. Three distinct cases were scrutinized: (1) caffeine adsorption on activated carbon; (2) tetracycline adsorption on hierarchical porous carbon; and (3) diclofenac adsorption on organoclay. While all three models demonstrated comparable performance with highly symmetric breakthrough data in case 1, their efficacy diverged significantly when confronted with strongly asymmetric breakthrough data in cases 2 and 3. The original Yoon-Nelson model and the logarithmically modified version fell short in accurately representing these intricate breakthrough curves. In contrast, the version incorporating steric hindrance effects showcased substantial accuracy, outperforming other models in capturing the complexities of asymmetric breakthrough data. This advancement markedly enhances the modeling accuracy and versatility of the Yoon-Nelson model, particularly in assessing the dynamic behavior of organic micropollutants within fixed bed adsorbers.

Interplay of the forces governing steroid hormone micropollutant adsorption in vertically-aligned carbon nanotube membrane nanopores

Vertically-aligned carbon nanotube (VaCNT) membranes allow water to conduct rapidly at low pressures and open up the possibility for water purification and desalination, although the ultralow viscous stress in hydrophobic and low-tortuosity nanopores prevents surface interactions with contaminants. In this experimental investigation, steroid hormone micropollutant adsorption by VaCNT membranes is quantified and explained via the interplay of the hydrodynamic drag and friction forces acting on the hormone, and the adhesive and repulsive forces between the hormone and the inner carbon nanotube wall. It is concluded that a drag force above 2.2 × 10−3 pN overcomes the friction force resulting in insignificant adsorption, whereas lowering the drag force from 2.2 × 10−3 to 4.3 × 10−4 pN increases the adsorbed mass of hormones from zero to 0.4 ng cm−2. At a low drag force of 1.6 × 10−3 pN, the adsorbed mass of four hormones is correlated with the hormone−wall adhesive (van der Waals) force. These findings explain micropollutant adsorption in nanopores via the forces acting on the micropollutant along and perpendicular to the flow, which can be exploited for selectivity.

How aromatic dissolved organic matter differs in competitiveness against organic micropollutant adsorption

Activated carbon is employed for the adsorption of organic micropollutants (OMPs) from water, typically present in concentrations ranging from ng L−1 to μg L−1. However, the efficacy of OMP removal is considerably deteriorated due to competitive adsorption from background dissolved organic matter (DOM), present at substantially higher concentrations in mg L−1. Interpreting the characteristics of competitive DOM is crucial in predicting OMP adsorption efficiencies across diverse natural waters. Molecular weight (MW), aromaticity, and polarity influence DOM competitiveness. Although the aromaticity-related metrics, such as UV254, of low MW DOM were proposed to correlate with DOM competitiveness, the method suffers from limitations in understanding the interplay of polarity and aromaticity in determining DOM competitiveness. Here, we elucidate the intricate influence of aromaticity and polarity in low MW DOM competition, spanning from a fraction level to a compound level, by employing direct sample injection liquid chromatography coupled with ultrahigh-resolution Fourier-transform ion cyclotron resonance mass spectrometry. Anion exchange resin pre-treatment eliminated 93% of UV254-active DOM, predominantly aromatic and polar DOM, and only minimally alleviated DOM competition. Molecular characterization revealed that nonpolar molecular formulas (constituting 26% PAC-adsorbable DOM) with medium aromaticity contributed more to the DOM competitiveness. Isomer-level analysis indicated that the competitiveness of highly aromatic LMW DOM compounds was strongly counterbalanced by increased polarity. Strong aromaticity-derived π-π interaction cannot facilitate the competitive adsorption of hydrophilic DOM compounds. Our results underscore the constraints of depending solely on aromaticity-based approaches as the exclusive interpretive measure for DOM competitiveness. In a broader context, this study demonstrates an effect-oriented DOM analysis, elucidating counterbalancing interactions of DOM molecular properties from fraction to compound level.

Aging microplastics enhances the adsorption of pharmaceuticals in freshwater

Plastic pollution is an increasing environmental concern. Pollutants such as microplastics (< 5 mm) and pharmaceuticals often co-exist in the aquatic environment. The current study aimed to elucidate the interaction of pharmaceuticals with microplastics and ascertain how the process of photo-oxidation of microplastics affected the adsorption of the pharmaceuticals. To this end, a mixture containing ibuprofen, carbamazepine, fluoxetine, venlafaxine and ofloxacin (16 μmol L−1 each) was placed in contact with one of six either virgin or aged microplastic types. The virgin microplastics were acquired commercially and artificially aged in the laboratory. Polypropylene, polyethylene, polyethylene terephthalate, polyamide, polystyrene, and polyvinyl chloride microparticles at two sizes described as small (D50 < 35 μm) and large (D50 95–157 μm) were evaluated. Results demonstrated that the study of virgin particles may underestimate the adsorption of micropollutants onto microplastics. For virgin particles, only small microparticles of polypropylene, polyethylene, polyvinyl chloride, and both sizes of polyamide adsorbed pharmaceuticals. Aging the microplastics increased significantly the adsorption of pharmaceuticals by microplastics. Fluoxetine adsorbed onto all aged microplastics, from 18 % (large polyethylene terephthalate) to 99 % (small polypropylene). The current investigation highlights the potential of microplastics to act as a vector for pharmaceuticals in freshwater, especially after aging.

Molecular level investigation of interactions between pharmaceuticals and β-cyclodextrin (β-CD) functionalized adsorption sites for removal of pharmaceutical contaminants from water

This study describes a novel application of the use of molecular modeling tools for investigating the adsorption of organic micropollutants (OMPs) from water by nanocomposites. The partitioning of pharmaceuticals onto β-Cyclodextrin (β-CD) functionalized adsorbents was investigated at the molecular level to explore the atomistic interactions of pharmaceutical contaminants in water systems with β-CD and to provide insight into possible approaches for removal of pharmaceuticals from water. Molecular electrostatic surface potential mapping of β-CD derivatives was employed to examine the impact of substitution degree of β-CD and type of grafting agent on host-guest complexation. The stability of the complexes of selected pharmaceuticals and β-CD derivatives were assessed via molecular dynamics simulations to evaluate competitive adsorption between organic micropollutants (OMPs) and between OMPs and fulvic acid, a representative natural organic material (NOM) component found in water systems. Molecular electrostatic surface potential maps showed that grafting agents with aromatic and amine functional groups were found to provide attractive interactions for negatively charged OMPs. In addition, optimization of substitution degree of β-CD is necessary to enhance adsorption of target OMPs. Furthermore, it was found that aromatic ring bearing grafting agents can provide additional electrostatic attractions by π-π interactions with the aromatic ring of the OMPs. The impact of common water quality characteristics on adsorption was assessed and it was revealed that the effect of pH and calcium on adsorption depends on the ionizable functional groups present on the grafting agent. Molecular dynamics simulations showed that adsorption of target OMPs does not solely depend on hydrophobicity but is affected by electrostatic interactions. The simulations revealed that fulvic acid which is commonly present in environmental waters can be a competitor with ibuprofen for the β-CD cavity. Ultimately, this study showed that molecular level simulation can be effectively employed to investigate adsorption of OMPs by β-CD functionalized adsorbents and could be employed to enhance their design and subsequent environmental applications.

Understanding and predicting the adsorption and rejection of pesticides and metabolites by hollow fiber nanofiltration membranes

Layer-by-layer Hollow fiber Nanofiltration (LbL HF-NF) membranes have shown great potential in the removal of micropollutants from water. Nonetheless, further research is required as the number of tested compounds remains limited. In this study, the adsorption and rejection of 164 micropollutants by two commercial HF-NF membranes with MWCO of 400 and 800 Da, were investigated. The investigation was conducted by evaluating the influence of 11 physicochemical micropollutants’ properties on the separation performances. Results showed that highly adsorbed compounds had average log D values above 3, while no or low adsorption was observed for compounds with negative log D values. Furthermore, adsorption was more frequently observed for neutral compounds compared to negatively charged ones. Micropollutants rejection results showed that steric exclusion plays the most important role in the rejection of micropollutants, and that the charge of micropollutants can also heavily influence their rejection. Likewise, negatively charged compounds were better rejected than neutral ones. Finally, the study demonstrated that adsorption and rejection of micropollutants can be predicted with good accuracy using the random forest algorithm. The prediction accuracy for adsorption was 80% and 73% for the 800 and 400 Da MWCO membranes, respectively. The RMSE for rejection predictions was 10.6% and 6% for the two membranes respectively.

Selective Adsorption of Organic Micro-Pollutants by Smectite Clays Revealed from Atomistic Simulations.

In this study, atomistic simulations were carried out to study the difference in the adsorption process between two similar molecules, diazepam and oxazepam, on Na+-montmorillonite. Kinetic and XRD measurements showed a contrasting adsorption mechanism of these two molecules, differing only by the presence/absence of methyl and hydroxyl groups, with a larger adsorption amount and intercalation for the oxazepam. The structural characterization of these molecules was investigated through DFT calculations and showed the vicinity of hydroxyl and carbonyl groups for only the chair conformation of oxazepam compared to the boat conformation. Classical molecular dynamics simulations of diazepam and the two forms of oxazepam on the external surface of Na+-montmorillonite highlighted the better coordination of the oxazepam-chair conformation, compared to its boat counterpart and diazepam. This has been confirmed through DFT calculations, from which a coordination energy that is greater by 10 kcal·mol-1 is observed. This strongly suggests that the experimentally observed intercalation of oxazepam occurs only in the chair form because of the strong coordination with the Na+ cation present in the Na-Mt interlayer. Classical MD simulations of the intercalated oxazepam chair molecule in the Na-Mt interlayer allowed the evaluation of the interlayer spacing d001, which was in very good agreement with the experimental XRD measurement.

Interfacial engineered, hierarchically porous, and underwater superelastic nanofibrous aerogels with rime-mimetic structure for superior micropollutant extraction

Developing nanofibrous aerogels with high surface area, nanoscale porosity, and robust underwater stability has been considered as one of the most promising strategies for designing the next-generation of high-efficiency extraction media, yet still facing great challenges. Herein, we report a size rearrangement of porous organic polymers (POPs) into superelastic rime-mimetic structured aerogels based on bacterial cellulose nanofibers (BCNs)-assisted interfacial engineering strategy. This strategy facilitates micro-interlocking between POP and BCN, significantly enhancing the attaching strength of POP particles at the POP/BCN interface. Thus, the optimized aerogels (PNAs) exhibit excellent underwater elasticity and compression fatigue resistance (∼0% plastic deformation after 500 compression cycles), as well as high BET surface area (305.44 m2/g) and hierarchical porosity (containing micro/meso/macropores), mainly due to the ultrahigh loading of POP particles (83.33 wt%). Given the possession of the abovementioned features and the careful selection of elution solvents guided by Hansen solubility parameter theory, PNAs exhibit a superior micropollutant adsorption capability (∼250 mg/g) and elution efficiency (concentrate sample volume by 50 times). The successful preparation of such material could inspire the development of next-generation hierarchically porous nanofibrous aerogel-based extraction media for water treatment.

Enhanced removal and stepwise recovery of inorganic and organic micropollutants from water using novel graphene oxide doped multifunctional β−cyclodextrin chitosan polymer

Herein, graphene oxide (GO) was successfully functionalized on the multifunctional β−cyclodextrin chitosan polymer through EDTA crosslinking (GO@CS−EDTA−β−CD) for the adsorption of toxic inorganic and organic micropollutants from water. This unique adsorbent possesses important adsorptive features from each component: chitosan works as a backbone of the polymer chain, β−CD cavities adsorb the organic micropollutants via the host-guest inclusion complexation, EDTA acts as a crosslinker and provides complexation sites for heavy metal ions and GO can interact with both organic and inorganic micropollutants. After complete characterization, the polymer were explored on the adsorption of inorganic micropollutants (i.e., Hg(II), Pb(II), Cu(II) and Ni(II)) and organic one (i.e., methylene blue, MB) under different experimental conditions. In monocomponent systems, the adsorption followed the pseudo-second order (PSO) kinetics for both heavy metals and MB dye. The adsorption isotherms of heavy metals and MB followed the Langmuir and Sips models, respectively. The maximum adsorption capacities were found to be 364.90 ± 15.20, 287.40 ± 10.0, 130.40 ± 6.50, 98.90 ± 3.10, 158.40 ± 5.10 mg g−1 for Hg(II), Pb(II), Cu(II), Ni(II) and MB, respectively. In binary component systems, dye adsorption was not affected by metal ions, while the adsorption efficiency for metal ions was increased by the MB presence: possibly due to synergism. Additionally, the prepared adsorbent showed good efficiency without any significant loss in adsorption capacity even after six continuous regeneration cycles, confirming its superior reusability and stability. In short, excellent removal efficiencies for the metal ions and MB at environmental levels in model textile effluent, synthetic acid mine water make the adsorbent promising in treating water contaminated by heavy metals and/or dyes.

Effects of organic matter in drinking water and wastewater on micropollutant adsorption to activated carbon

AbstractImproving the removal of micropollutants from wastewater effluent is crucial to protect surface water quality. This can be achieved by applying adsorption to granular activated carbon. However, activated carbon filters used for wastewater treatment have a shorter lifetime than filters used for drinking water production. It was assessed whether this is related exclusively to the higher organic matter concentration in wastewater effluent, compared to drinking water, or also to organic matter characteristics. Influent of activated carbon filters from a drinking water plant and wastewater effluent were used as organic matter sources, and their effect on micropollutant affinity for activated carbon and adsorption rate was compared at the same dissolved organic carbon concentrations. Organic matter characterization (excitation–emission matrices and parallel factor—PARAFAC—analysis) and fractionation methods, based on size and hydrophobicity, were combined to assess the relevance of specific components that affect micropollutant removal. The results show that both organic matter concentration and composition determine their effect on micropollutant affinity for activated carbon and adsorption rate. The affinity of micropollutants for activated carbon is more reduced in the presence of organic matter from wastewater effluent. Adsorption rate is lower in the presence of organic matter originating from drinking water plants at levels around 10 mg/L, compared to wastewater effluent. One PARAFAC component is more abundant in drinking water organic matter and is likely responsible for this effect. This knowledge supports the development of strategies to overcome bottlenecks on the application of activated carbon filters in water treatment.

Production and characterization of graphene oxide-engineered biochars and application for organic micro-pollutant adsorption from aqueous solutions.

In this study, conventional and Graphene Oxide-engineered biochars were produced and thoroughly characterized, in order to investigate their potential as adsorptive materials. Two types of biomass, Rice Husks (RH) and Sewage Sludge (SS), two Graphene Oxide (GO) doses, 0.1% and 1%, and two pyrolysis temperatures, 400°C and 600°C were investigated. The produced biochars were characterized in physicochemical terms and the effect of biomass, GO functionalization and pyrolysis temperature on biochar properties was studied. The produced samples were then applied as adsorbents for the removal of six organic micro-pollutants from water and treated secondary wastewater. Results showed that the main factors affecting biochar structure was biomass type and pyrolysis temperature, while GO functionalization caused significant changes on biochar surface by increasing the available C- and O- based functional groups. Biochars produced at 600°C showed higher C content and Specific Surface Area, presenting more stable graphitic structure, compared to biochars produced at 400°C. Micro-pollutant adsorption rates were in the range of 39.9%-98.3% and 9.4%-97.5% in table water and 28.3%-97.5% and 0.0%-97.5% in treated municipal wastewater, for the Rice Husk and Sewage Sludge biochars respectively. The best biochars, in terms of structural properties and adsorption efficiency were the GO-functionalized biochars, produced from Rice Husks at 600°C, while the most difficult pollutant to remove was 2.4-Dichlorophenol.

Inhibition caused by adsorption of organic micropollutants (MPs) on PES@CoFe2O4 polymeric ultrafiltration membranes and the enhanced MPs degradation by a continuous pH regulation

In this work, catalytic membranes were fabricated by blending CoFe2O4 catalysts into polyethersulfone (PES) and then used to treat naproxen with the addition of peroxymonosulfate (PMS). It was found that the addition of PMS results in a decrease in pH, which increases the adsorption of naproxen. This often overlooked phenomenon is demonstrated here to have an important role since the adsorption of naproxen on the polymeric matrix and catalytic particles decreases the degradation efficiency of naproxen. To verify this hypothesis and rule out the decrease in pH after the addition of pH, two ways of controlling the pH of the naproxen solution were compared: adjusting pH before and after the addition of PMS, respectively. Our results indicate that in the batch experiment, adjusting the pH of naproxen solution after adding PMS led to a dramatic 23-fold increase in the kinetic constant of the naproxen oxidation (0.42/min, pH6) compared to when pH was adjusted before adding PMS (0.018/min, pH 6). This enhancement in the overall kinetics was attributed to the elimination of the inhibition caused by MPs adsorption at low pH. In a dead-end cell, the catalytic membranes with 2.0 % of CoFe2O4 achieved quantitative conversion of naproxen, bisphenol A, and atrazine, with values of 98 %, 97 %, and 74 %, respectively, demonstrating the efficacy of this approach to convert multitype of MPs in wastewater streams. In a reusability study, the naproxen removal of the catalytic membranes with 2.0 % of CoFe2O4 decreased by 81 % and 45 % after 5 rounds in the batch experiment and dead-end cell, respectively. However, with a chemical cleaning process between each round, the degradation efficiency can be effectively recovered, proving the negative effects of the adsorption of MPs or their intermediates during the SR-AOPs. Our work demonstrates that pH in SR-AOP-based catalytic membrane processes determined both the reaction rate and the adsorption of MPs or their intermediates on the membrane and its reactive sites. We envision that these results will be valuable in developing efficient catalytic membranes for the treatment of MPs in wastewater streams.

Adsorption of organic micropollutants on yeast: Batch experiment and modeling

Yeast is ubiquitous and may act as a solid phase in natural aquatic systems, which may affect the distribution of organic micropollutants (OMs). Therefore, it is important to understand the adsorption of OMs on yeast. Therefore, in this study, a predictive model for the adsorption values of OMs on the yeast was developed. For that, an isotherm experiment was performed to estimate the adsorption affinity of OMs on yeast (i.e., Saccharomyces cerevisiae). Afterwards, quantitative structure-activity relationship (QSAR) modeling was performed for the purpose of developing a prediction model and explaining the adsorption mechanism. For the modeling, empirical and in silico linear free energy relationship (LFER) descriptors were applied. The isotherm results showed that yeast adsorbs a wide range of OMs, but the magnitude of Kd strongly depends on the types of OMs. The measured log Kd values of the tested OMs ranged from −1.91 to 1.1. Additionally, it was confirmed that the Kd measured in distilled water is comparable to that measured in real anaerobic or aerobic wastewater (R2 = 0.79). In QSAR modeling, the Kd value could be predicted by the LFER concept with an R2 of 0.867 by empirical descriptors and an R2 of 0.796 by in silico descriptors. The adsorption mechanisms of yeast for OMs were identified in individual correlations between log Kd and each descriptor: Dispersive interaction, hydrophobicity, hydrogen-bond donor, and cationic Coulombic interaction of OMs attract the adsorption, while the hydrogen-bond acceptor and anionic Coulombic interaction of OMs act as repulsive forces. The developed model can be used as an efficient method to estimate OM adsorption to yeast at a low level of concentration.

Adsorption and degradation of multiple micropollutants with trace concentrations by porous Zr-porphyrin metal-organic frameworks with missing linker defects in water

Metal-organic frameworks (MOFs) are effective photocatalysts with high surface area and excellent visible light absorption. In this study, a kind of Zr-porphyrin (PCN-134) and its derivatives PCN-134(Fe) and PCN-134 (Cu) were prepared for removing six structurally diverse micropollutants with extremely low concentrations (100 μg/L). The initial adsorption rates for five selected pharmaceuticals (antipyrine (AT), sulfadimethoxypyrimidine (SSM), clofibric acid (CA), diclofenac (DF), and ibuprofen (IBU)) ranged from 174.5 μg/(g • min) to 2256.5 μg/(g • min) over PCN-134 (Cu), which is 1.2–2.5 times higher than those of PCN-134. A series of optical and photoelectric properties were studied using Mott−Schottky plots, UV–Vis diffuse reflectance spectrum (UV-DRS), and transient photocurrent intensity analysis. PCN-134 (Fe) successfully extended the visible-light absorption edges at around 750 nm. PCN-134 and PCN-134 (Fe) were favorable for generating •O2− with ECB values calculated at −1.04 eV and - 0.55 eV by Mott−Schottky plots and UV–Vis diffuse reflectance spectrum (UV-DRS). The incorporation of metals enhanced the charge separation properties of PCN-134. The transient photocurrent intensity of PCN-134 (Fe) was 3.1 times higher than that of PCN-134 (Cu). The degradation efficiency for naproxen (NPX) over PCN-134 (Fe) for antipyrine (AT) and clofibric acid (CA) was 2.4 times and 11.3 times higher than those over the pristine PCN-134. •O2− and 1O2 could be the major ROS produced, confirmed by quenching experiments and electron paramagnetic resonance (EPR) technologies. This study offers useful guidance to improve the current materials for water purification.

Supramolecular Engineering of Amorphous Porous Polymers for Rapid Adsorption of Micropollutants and Solar‐Powered Volatile Organic Compounds Management (Adv. Mater. 50/2022)

Supramolecular Engineering of Amorphous Porous Polymers for Rapid Adsorption of Micropollutants and Solar‐Powered Volatile Organic Compounds Management (Adv. Mater. 50/2022)

Supramolecular Engineering of Amorphous Porous Polymers for Rapid Adsorption of Micropollutants and Solar-Powered Volatile Organic Compounds Management.

Freshwater shortage is becoming one of the most critical global challenges owing to severe water pollution caused by micropollutants and volatile organic compounds (VOCs). However, current purification technology shows slow adsorption of micropollutants and requires an energy-intensive process for VOCs removal from water. In this study, a highly efficient molecularly engineered covalent triazine framework (CTF) for rapid adsorption of micropollutants and VOC-intercepting performance using solar distillation is reported. Supramolecular design and mild oxidation of CTFs (CTF-OXs) enable hydrophilic internal channels and improve molecular sieving of micropollutants. CTF-OX shows rapid removal efficiency of micropollutants (>99.9% in 10s) and can be regenerated several times without performance loss. Uptake rates of selected micropollutants are high, with initial pollutant uptake rates of 21.9gmg-1 min-1 , which are the highest rates recorded for bisphenol A (BPA) adsorption. Additionally, photothermal composite membrane fabrication using CTF-OX exhibits high VOC rejection rate (up to 98%) under 1 sun irradiation (1kWm-2 ). A prototype of synergistic purification system composed of adsorption and solar-driven membrane can efficiently remove over 99.9% of mixed phenol derivatives. This study provides an effective strategy for rapid removal of micropollutants and high VOC rejection via solar-driven evaporation process.