Physiological responses and altered halocarbon production in Phaeodactylum tricornutum after exposure to polystyrene microplastics.

Oceanic emissions are a major source of atmospheric, very short-lived, ozone-depleting, brominated substances. These substances can be produced by marine microalgae, estimates of their current and future emissions are imperfect, because the processes by which marine microalgae respond to environmental changes are rarely account for environmental pollutants. Here, concurrent measurements of the potential effects of polystyrene (PS) microplastics with concentrations of 25-100 mg/L on the growth of Phaeodactylum tricornutum and their volatile halocarbons (VHCs) production were made over a 20-day culture period. The maximum inhibition rates (IR) due to 0.1 µm and 0.5 µm PS microplastics on cell density were 40.11 % and 32.87 %, on Chl a content were 25.89 % and 20.73 %, and on Fv/Fm were 9.74 % and 9.00 %, respectively. All IR showed dose-dependent effects with maxima occurring in the logarithmic phase. However, in the stationary phase, P. tricornutum exposed to PS microplastics exhibited improved attributes. Enhanced biogenesis of VHCs was induced by the excess reactive oxygen species in algal cells due to microplastics exposure, and their production rates were higher in the logarithmic phase than stationary phase. This represents that oxidative stress to cells plays a dominant role in determining the release of CHBrCl2, CHBr2Cl, and CHBr3. Hence, we suggest that the widespread microplastics in the ocean may be partly responsible for the increase in the emission of VHCs by marine phytoplankton, thereby affecting the ozone layer recovery in the future.

Reduction-Controlled Atomic Migration for Single Atom Alloy Library.

Picturing the atomic migration pathways of catalysts in a reactive atmosphere is of central significance for uncovering the underlying catalytic mechanisms and directing the design of high-performance catalysts. Here, we describe a reduction-controlled atomic migration pathway that converts nanoparticles to single atom alloys (SAAs), which has remained synthetically challenging in prior attempts due to the elusive mechanism. We achieved this by thermally treating the noble-metal nanoparticles M (M = Ru, Rh, Pd, Ag, Ir, Pt, and Au) on metal oxide (CuO) supports with H2/Ar. Atomic-level characterization revealed such conversion as the synergistic consequence of noble metal-promoted H2 dissociation and concomitant CuO reduction. The observed atomic migration pathway offers an understanding of the dynamic mechanisms study of nanomaterials formation and catalyst design.

EDTA-Na2 as a recoverable draw solute for water extraction in forward osmosis.

Regeneration and reuse of draw solute (DS) is a key challenge in the application of forward osmosis (FO) technologies. Herein, EDTA-Na2 was studied as a recoverable DS for water extraction by taking advantages of its pH-responsive property. The FO system using EDTA DS achieved a higher water flux of 2.22 ± 0.06 L m-2 h-1 and a significantly lower reverse salt flux (RSF) of 0.06 ± 0.01 g m-2 h-1, compared to that with NaCl DS having either the same DS concentration or the same Na+ concentration. The suitable pH range for the application of EDTA DS was between 4.0 and 10.5. A simple recovery method via combined pH adjustment and microfiltration was employed to recover EDTA DS and could achieve the recovery efficiency (at pH 2) of 96.26 ± 0.48%, 97.13 ± 1.03% and 98.56 ± 1.40% by using H2SO4, H3PO4 and HCl, respectively. The lowest acid cost for DS recovery was estimated from 0.0012 ± 0.0001 to 0.0162 ± 0.0003 $ g-1 by using H2SO4. The recovered EDTA DS could be reused in the subsequent FO operation and the overall recovery efficiency was 94.4% for four reuse cycles. These results have demonstrated the feasible of EDTA-Na2 DS and a potentially cost-effective recovery approach, and encouraged further exploration of using EDTA-based compounds as a draw solute for FO applications.

A Metallic Ion-Induced Self-Assembly Enabling Nanowire-Based Aerogels.

The controlled assembly of nanowires is one of the key challenges in the development of a range of functional 3D aerogels with unique physicochemical properties for practical applications. However, the deep understanding of the dynamic assemble process for fabricating nanowire aerogels remains elusive. Herein, a facile strategy is presented for the metallic ion-induced assembly of nanowires into macroscopic aerogels via a solution-based process. This method enables the interconnecting between polymer-decorated nanowires via metallic coordination, resulting in plenty of nanowire bundles with the same orientation. Besides, the coordinated binding strength of nanowires with different metallic ions is also discussed. The assembly mechanism that the metallic ions induced dynamic behavior of nanowires is revealed via molecular dynamics theoretical evaluation. These findings benefit for constructing nanowire-based aerogels with unique structural features and multi-function, which pave new opportunities for other material systems.

Effect of Capecitabine Maintenance Therapy Using Lower Dosage and Higher Frequency vs Observation on Disease-Free Survival Among Patients With Early-Stage Triple-Negative Breast Cancer Who Had Received Standard Treatment: The SYSUCC-001 Randomized Clinical Trial.

Importance: Among all subtypes of breast cancer, triple-negative breast cancer has a relatively high relapse rate and poor outcome after standard treatment. Effective strategies to reduce the risk of relapse and death are needed. Objective: To evaluate the efficacy and adverse effects of low-dose capecitabine maintenance after standard adjuvant chemotherapy in early-stage triple-negative breast cancer. Design, Setting, and Participants: Randomized clinical trial conducted at 13 academic centers and clinical sites in China from April 2010 to December 2016 and final date of follow-up was April 30, 2020. Patients (n = 443) had early-stage triple-negative breast cancer and had completed standard adjuvant chemotherapy. Interventions: Eligible patients were randomized 1:1 to receive capecitabine (n = 222) at a dose of 650 mg/m2 twice a day by mouth for 1 year without interruption or to observation (n = 221) after completion of standard adjuvant chemotherapy. Main Outcomes and Measures: The primary end point was disease-free survival. Secondary end points included distant disease-free survival, overall survival, locoregional recurrence-free survival, and adverse events. Results: Among 443 women who were randomized, 434 were included in the full analysis set (mean [SD] age, 46 [9.9] years; T1/T2 stage, 93.1%; node-negative, 61.8%) (98.0% completed the trial). After a median follow-up of 61 months (interquartile range, 44-82), 94 events were observed, including 38 events (37 recurrences and 32 deaths) in the capecitabine group and 56 events (56 recurrences and 40 deaths) in the observation group. The estimated 5-year disease-free survival was 82.8% in the capecitabine group and 73.0% in the observation group (hazard ratio [HR] for risk of recurrence or death, 0.64 [95% CI, 0.42-0.95]; P = .03). In the capecitabine group vs the observation group, the estimated 5-year distant disease-free survival was 85.8% vs 75.8% (HR for risk of distant metastasis or death, 0.60 [95% CI, 0.38-0.92]; P = .02), the estimated 5-year overall survival was 85.5% vs 81.3% (HR for risk of death, 0.75 [95% CI, 0.47-1.19]; P = .22), and the estimated 5-year locoregional recurrence-free survival was 85.0% vs 80.8% (HR for risk of locoregional recurrence or death, 0.72 [95% CI, 0.46-1.13]; P = .15). The most common capecitabine-related adverse event was hand-foot syndrome (45.2%), with 7.7% of patients experiencing a grade 3 event. Conclusions and Relevance: Among women with early-stage triple-negative breast cancer who received standard adjuvant treatment, low-dose capecitabine maintenance therapy for 1 year, compared with observation, resulted in significantly improved 5-year disease-free survival. Trial Registration: ClinicalTrials.gov Identifier: NCT01112826.

Mitigation of Salinity Buildup and Recovery of Wasted Salts in a Hybrid Osmotic Membrane Bioreactor-Electrodialysis System.

The osmotic membrane bioreactor (OMBR) is an emerging technology that uses water osmosis to accomplish separation of biomass from the treated effluent; however, accumulation of salts in the wastewater due to water flux and loss of draw solute because of reverse salt flux seriously hinder OMBR development. In this study, a hybrid OMBR-electrodialysis (ED) system was proposed and investigated to alleviate the salinity buildup. The use of an ED (3 V applied) could maintain a relatively low conductivity of 8 mS cm(-1) in the feed solution, which allowed the OMBR to operate for 24 days, about 6 times longer than a conventional OMBR without a functional ED. It was found that the higher the voltage applied to the ED, the smaller area of ion-exchange membrane was needed for salt separation. The salts recovered by the ED were successfully reused as a draw solute in the OMBR. At an energy consumption of 1.88-4.01 kWh m(-3), the hybrid OMBR-ED system could achieve a stable water flux of about 6.23 L m(-2) h(-1) and an efficient waste salt recovery of 1.26 kg m(-3). The hybrid OMBR-ED system could be potentially more advantageous in terms of less waste saline water discharge and salt recovery compared with a combined OMBR and reverse osmosis system. It also offers potential advantages over the conventional OMBR+post ED treatment in higher water flux and less wastewater discharge.

A novel approach to recycle bacterial culture waste for fermentation reuse via a microbial fuel cell-membrane bioreactor system.

Biochemical production processes require water and nutrient resources for culture media preparation, but aqueous waste is generated after the target products are extracted. In this study, culture waste (including cells) produced from a lab-scale fermenter was fed into a microbial fuel cell-membrane bioreactor (MFC-MBR) system. Electrical energy was generated via the interaction between the microbial consortia and the solid electrode in the MFC. The treated wastewater was reclaimed in this process which was reused as a solvent and a nutrient source in subsequent fermentation. Polarization testing showed that the MFC produced a maximum current density of 37.53 A m(-3) with a maximum power density of 5.49 W m(-3). The MFC was able to generate 0.04 kWh of energy per cubic meter of culture waste treated. The lab-scale fermenters containing pure cultures of an engineered Pseudomonas spp. were used to generate 2-pyrone-4,6-dicarboxylic acid (PDC), a high value platform chemical. When the MFC-MBR-treated wastewater was used for the fermenter culture medium, a specific bacterial growth rate of 1.00 ± 0.05 h(-1) was obtained with a PDC production rate of 708.11 ± 64.70 mg PDC L(-1) h(-1). Comparable values for controls using pure water were 0.95 ± 0.06 h(-1) and 621.01 ± 22.09 mg PDC L(-1) h(-1) (P > 0.05), respectively. The results provide insight on a new approach for more sustainable bio-material production while at the same time generating energy, and suggest that the treated wastewater can be used as a solvent and a nutrient source for the fermentation production of high value platform chemicals.

[Effects of Polyethylene Microplastics on Growth and Halocarbon Release of Marine Microalgae].

Volatile halocarbons (VHCs) are important trace greenhouse gases and ozone-destroying substances and play an important role in global climate change. As an important producer of VHCs, the release of VHCs by marine microalgae is affected by marine environmental factors. Microplastics are an important pollutant in the ocean; however, there are few studies on VHCs release from marine microalgae under the influence of microplastics. This study aimed to explore the effects of different concentrations of polyethylene (PE) microplastics on the growth, photosynthesis, oxidative stress, and release of VHCs by diatoms and dinoflagellates by measuring the density of algae, maximum photoquantum efficiency (Fv/Fm), reactive oxygen species (ROS), and concentration of VHCs. The results revealed that PE microplastics mainly inhibited the growth of Nitzschia closterium f. minutissima and promoted the growth of Prorocentrum donghaiense. The addition of 50 µm PE microplastics had a shielding effect on the growth of the two microalgae, resulting in the inhibition of Fv/Fm of two kinds of microalgae, and the inhibition effect of PE microplastics on P. donghaiense was more significant. Compared with that in the control group, PE microplastic stress stimulated the increase in ROS production in algal cells, which caused an oxidative stress response in these microalgae, thereby promoting the release of three types of volatile brominated halocarbons.

Effects of draw solutes on an integrated forward osmosis-Microbial fuel cell system treating a synthetic wastewater.

Microbial fuel cells (MFCs) and forward osmosis (FO) are both attractive and versatile wastewater treatment technologies that possess disadvantageous qualities that prevent their optimal performance. This study aimed to investigate how draw solute selection for FO treatment would affect MFC performance in a coupled FO-MFC system. Two types of draw solutes, NH4 HCO3 and NaCl, were studied, and it was found that 1.0 M NH4 HCO3 (FO-MFC-A) and 0.68 M NaCl (FO-MFC-B) had similar water fluxes of 6.04 to 3.39 LMH and 6.25 to 3.54 LMH, respectively. The reverse salt flux from the draw decreased the feed solution resistance for both draw solutes, but the FO-MFC-A system (0.32 W m-2 ) had a higher maximum power density than the FO-MFC-B system (0.26 W m-2 ). The current density for the FO-MFC-B system increased due to continuous solution resistance decrease, whereas it remained constant for the FO-MFC-A. The difference in Coulombic efficiencies (32.8% vs. 25.6%) but similar Coulombic recoveries (10.2% vs. 11.4%) between the FO-MFC-A and FO-MFC-B systems suggested that the FO-MFC-A might have the inhibited microbial activity by high ammonium/ammonia. The FO-MFC-A system had the lower energy consumption for nutrient removal (2.01 kWh kg-1 NH4 + -N) and recovery (8.87 kWh kg-1 NH4 + -N). These results have shown that NH4 HCO3 as a draw solute can have advantages of higher power density, higher Coulombic efficiency, and recoverability for draw regeneration, but its potential inhibition on microbial activity must also be considered. PRACTITIONER POINTS: Forward osmosis can be connected to microbial fuel cells for wastewater treatment. Water recovery by forward osmosis can greatly reduce the wastewater volume to microbial fuel cells. Ammonium draw solutes can result in lower volumetric energy consumption. Ammonia inhabitation of anode microbes will decrease organic removal.

Effects of polystyrene microplastic on the growth and volatile halocarbons release of microalgae Phaeodactylum tricornutum.

Volatile halocarbons (VHCs) are trace greenhouse gases that can damage the ozone layer. Trihalomethanes are one of the most common VHCs and play an important role in global climate change. Due to their steadily increasing abundance, microplastics pollutants have attracted growing concern from scientists. However, their impacts on the growth of marine microalgae and the release of VHCs remain unknown. The influence of polystyrene microplastic (PS, 0.1 µm) at different concentrations (25-200 mg/L) on the growth of P. tricornutum and their release of trihalomethanes were studied over 96 h. The results showed that PS can inhibit P. tricornutum growth. At 200 mg/L PS, cell growth, chlorophyll a concentration and photosynthetic efficiency of P. tricornutum were inhibited by 53.53%, 25.45% and 12.50%, respectively. PS concentrations of 25-50 mg/L promoted the release of the three trihalomethanes by P. tricornutum during the 96 h culture as a response to oxidative stress. However, 100-200 mg/L PS severely altered the physiological state of the P. tricornutum cells after 48 h, which reduced the release of trihalomethanes. Our study also demonstrated that the production and release of trihalomethanes served as a protective mechanism against oxidative stress and the toxic effects caused by PS.

Enhanced understanding of osmotic membrane bioreactors through machine learning modeling of water flux and salinity.

Mathematical modeling can be helpful to understand and optimize osmotic membrane bioreactors (OMBR), a promising technology for sustainable wastewater treatment with simultaneous water recovery. Herein, seven machine learning (ML) algorithms were employed to model both water flux and salinity of a lab-scale OMBR. Through the optimum hyperparameters tuning and 5-fold cross-validation, the ML models have achieved more accurate results without obvious overfitting and bias. The median R2 scores of water flux modeling were all over the 0.95 and the most of median R2 scores from total dissolved solids (TDS) modeling were higher than 0.90. During model testing, random forest (RF) algorithm presented the highest R2 score of 0.987 with the lowest root mean square error (RMSE = 0.044) for the water flux modeling, and extreme gradient boosting (XGB) algorithm exhibited the best results (R2 = 0.97; RMSE = 0.234) in the TDS modeling. The Shapley Additive exPlanations (SHAP) analysis found that the phosphorus concentration was a critical input feature for both water flux and TDS modeling. Finally, the selected ML models were used to predict water flux and salinity affected by two input features and the predication results confirmed the importance of the phosphate concentration. The results of this study have demonstrated the promise of ML modeling for investigating OMBR systems.

Ammonia recovery from simulated anaerobic digestate using a two-stage direct contact membrane distillation process.

Ammonia is a key inorganic contaminant in wastewater and an important nutrient element for agriculture. Herein, a two-stage direct contact membrane distillation (DCMD) system was developed and investigated for ammonia recovery from a synthetic anaerobic digestate. In the 1st stage DCMD (DCMD-1), both ammonia and water moved across MD membrane to realize ammonia separation, while in the 2nd stage (DCMD-2), only water migrated and as a result ammonia was concentrated. It was found that increasing the initial feed solution pH could enhance ammonia removal in the DCMD-1 from 16.0 ± 2.0% (no pH adjustment) to 84.2 ± 1.9% (pH 12). A higher feed solution temperature increased both ammonia flux and water flux. The optimal condition was determined as an initial feed pH of 12, a feed temperature of 60°C, and the 0.6 M H2 SO4 adsorption solution. With the addition of the DCMD-2, the ammonia concentration was improved from 3 g L-1 to 7.8 ± 0.2 g L-1 , which was further enhanced to 26.3 ± 3.0 g L-1 after five batches of operation. These results have demonstrated the feasibility of a two-stage DCMD system for ammonia recovery from anaerobic digestate and warrant further investigation of several key issues that may advance this technology. PRACTITIONER POINTS: A two-stage membrane distillation system is developed to remove and recover ammonia from anaerobic digester effluents. The system uses ammonia/ammonium equilibrium to separate ammonia in the 1st stage and then concentrate it in the 2nd stage. A high initial pH of the feed solution plays a key role in achieving high ammonia removal. Minimizing the volume of permeate solution can increase the ammonia concentration.

Enhancing anammox resistance to low operating temperatures with the use of PVA gel beads.

Low temperatures, or a sudden decrease in operating temperature, can seriously inhibit anammox activity, it is, therefore, important to maintain anammox activities at a low temperature. In this study, the use of gel beads to enhance the resistance of anammox biomass to a low temperature was investigated. The performance of three reactors: R1 without gel beads; R2 with polyvinyl alcohol/chitosan (PVA/CS); R3 with PVA/CS/Fe, was studied and compared in a temperature transition from 35 to 8 °C. When the operating temperature was ≥25 °C, there was little difference in nitrogen removal among the three reactors. Decreasing the temperature to < 25 °C created obvious difference between R1 and R2/R3. R1 had a nitrogen removal efficiency (NRE) of 33.1 ± 25.3% at 10 °C, significantly lower than that of R2 (90.5 ± 2.5%) or R3 (87.7 ± 11.1%). Unclassified Candidatus Brocadiaceae was the dominant genus at 10 °C, with an abundance of 44.4, 56.5 and 58.7% in R1, R2 and R3, respectively. These differences were attributed to the use of gel beads, which promoted the granulation of both the non-immobilized sludge and the immobilized biomass, resulting in higher anammox activities in R2/R3. The non-immobilized sludge of R1 was dominated by small particles (<300 µm) at 10 °C, while in R2 and R3 large particles (1000-2000 µm) were the main components. Furthermore, the immobilized biomass on gel beads exhibited much higher anammox activity and maintained a relatively high level of nitrate reductase and nitrite reductase in response to the temperature decrease. The Fe2+/Fe3+ in the PVA/CS/Fe gel beads further promoted microbial aggregation and led to an improved performance in R3 compared to R2. The results of this study demonstrate an effective approach to increase anammox resistance at low operating temperatures.

A comprehensive review of nutrient-energy-water-solute recovery by hybrid osmotic membrane bioreactors.

Hybrid osmotic membrane bioreactor (OMBR) takes advantage of the cooperation of varying biological or desalination processes and can achieve NEWS (nutrient-energy-water-solute) recovery from wastewater. However, a lack of universal parameters hinders our understanding. Herein, system configurations and new parameters are systematically investigated to help better evaluate recovery performance. High-quality water can be produced in reverse osmosis/membrane distillation-based OMBRs, but high operation cost limits their application. Although bioelectrochemical system (BES)/electrodialysis-based OMBRs can effectively achieve solute recovery, operation parameters should be optimized. Nutrients can be recovered from various wastewater by porous membrane-based OMBRs, but additional processes increase operation cost. Electricity recovery can be achieved in BES-based OMBRs, but energy balances are negative. Although anaerobic OMBRs are energy-efficient, salinity accumulation limits methane productions. Additional efforts must be made to alleviate membrane fouling, control salinity accumulation, optimize recovery efficiency, and reduce operation cost. This review will accelerate hybrid OMBR development for real-world applications.

Effects of operating parameters on salinity accumulation in a bioelectrochemically-assisted osmotic membrane bioreactor.

Salinity accumulation in osmotic membrane bioreactors (OMBRs) is one of the key challenges, which can be mitigated in situ by reverse-fluxed solute transport through integration of bioelectrochemical systems (BES). The effects of several key operating parameters on salinity accumulation were investigated. Salinity accumulation depended on balance between reversal solute flux (RSF) and reverse-fluxed ammonium (RFA) transport, which was driven by electrical migration and concentration diffusion. DS concentration was the primary factor influencing RSF, and the lowest DS concentration exhibited the minimum solute leakage. Aeration played a vital role in RFA transport, and a higher aeration helped to enhance RFA transport. Increased current generation (i.e., influent flow rate of 0.5 mL min-1 and external resistance of 5.0 Ω) contributed to RFA migration. The lack of electrolyte addition in catholyte contributed to RFA diffusion. These optimal parameters encourage the further development of an effective strategy for salinity mitigation in BES-based OMBR technology.

Mitigating nutrient accumulation with microalgal growth towards enhanced nutrient removal and biomass production in an osmotic photobioreactor.

Forward osmosis (FO) has great potential for low energy consumption wastewater reuse provided there is no requirement for draw solutes (DS) regeneration. Reverse solute flux (RSF) can lead to DS build-up in the feed solution. This remains a key challenge because it can cause significant water flux reduction and lead to additional water quality problems. Herein, an osmotic photobioreactor (OsPBR) system was developed to employ fast-growing microalgae to consume the RSF nutrients. Diammonium phosphate (DAP) was used as a fertilizer DS, and algal biomass was a byproduct. The addition of microalgae into the OsPBR proved to maintain water flux while reducing the concentrations of NH4+-N, PO43--P and chemical oxygen demand (COD) in the OsPBR feed solution by 44.4%, 85.6%, and 77.5%, respectively. Due to the forward cation flux and precipitation, intermittent supplements of K+, Mg2+, Ca2+, and SO42- salts further stimulated algal growth and culture densities by 58.7%. With an optimal hydraulic retention time (HRT) of 3.33 d, the OsPBR overcame NH4+-N overloading and stabilized key nutrients NH4+-N at âˆ¼ 2.0 mg L-1, PO43--P < 0.6 mg L-1, and COD < 30 mg L-1. A moderate nitrogen reduction stress resulted in a high carbohydrate content (51.3 ± 0.1%) among microalgal cells. A solids retention time (SRT) of 17.82 d was found to increase high-density microalgae by 3-fold with a high yield of both lipids (9.07 g m-3 d-1) and carbohydrates (16.66 g m-3 d-1). This study encourages further exploration of the OsPBR technology for simultaneous recovery of high-quality water and production of algal biomass for value-added products.

Bioelectrochemically assisted osmotic membrane bioreactor with reusable polyelectrolyte draw solutes.

The aim of this work was to study reverse solute flux (RSF) from osmotic membrane bioreactor (OMBR) and consequent solute buildup in the feed side. A polyelectrolyte (PAA-Na) served as a draw solute (DS) to minimize RSF in OMBRs. In addition, a bioelectrochemical system (BES) was employed to drive accumulated cations from the feed/anode side into the cathode compartment, subsequently achieving PAA-Na DS recovery with the aid of high catholyte pH. Compared to the 1 M NH4HCO3 DS, the 0.48 g mL-1 PAA-Na DS produced consistently stable water flux, enhanced water recovery and increased ammonium removal efficiency. Due to a dynamic balance between PAA removal and continuing RSF, the residual PAA concentration was 72 mg L-1 on the feed side (27.0% of TOC). These results demonstrate the advantages of integrating a PAA-Na DS with a BES to mitigate RSF and to support further development of OMBR technology.

Tackle reverse solute flux in forward osmosis towards sustainable water recovery: reduction and perspectives.

Forward osmosis (FO) has emerged as a potentially energy-efficient membrane treatment technology to yield high-quality reusable water from various wastewater/saline water sources. A key challenge remained to be solved for FO is reverse solute flux (RSF), which can cause issues like reduced concentration gradient and loss of draw solutes. Yet no universal parameters have been developed to compare RSF control performance among various studies, making it difficult to position us in this "battle" against RSF. In this paper, we have conducted a concise review of existing RSF reduction approaches, including operational strategies (e.g., pressure-, electrolysis-, and ultrasound-assisted osmosis) and advanced membrane development (e.g., new membrane fabrication and existing membrane modification). We have also analyzed the literature data to reveal the current status of RSF reduction. A new parameter, mitigation ratio (MR), was proposed and used together with specific RSF (SRSF) to evaluate RSF reduction performance. Potential research directions have been discussed to help with future RSF control. This review intends to shed more light on how to effectively tackle solute leakage towards a more cost-effective and environmental-friendly FO treatment process.

Precise control of iron activating persulfate by current generation in an electrochemical membrane reactor.

Activated persulfate (PS) oxidation is promising for contaminant removal but a lack of controllable activation can lead to a loss of reagents and thus low contamination degradation. Herein, we have proposed and investigated an innovative method to control PS activation by introducing ion exchange membrane into electrochemically activated PS. This electrochemical membrane reactor (EMR) could precisely control PS activation by adjusting electrical current for slow release of Fe2+, and also avoid direct contact between PS and a sacrificial anode electrode (iron electrode)/an alkaline cathode solution. It was found that the PS decomposition rate constant was linearly increased by increasing the applied current (R2 = 0.988). The rate of the released Fe2+ also exhibited a linear relationship with the applied current (R2 = 0.995). Compared to one-time dosage of Fe2+, the EMR-based slow-release process had higher contamination degradation and better PS utilization (molar ratio of the decomposed PS to the migrated Fe, 1.04 ±â€¯0.01:1), thereby minimizing the waste of both reaction reagents and generated radicals. The EMR was also employed to degrade a representative dye contaminant in a controllable manner and achieved 95.7 ±â€¯0.7% removal percentage with PS dosage of 3.0 g L-1 within 20 min. This study is among the earliest to explore effective approaches for precisely controlling PS activation and subsequent oxidation of contaminants.

Mitigation of bidirectional solute flux in forward osmosis via membrane surface coating of zwitterion functionalized carbon nanotubes.

Forward osmosis (FO) has emerged as a promising membrane technology to yield high-quality reusable water from various water sources. A key challenge to be solved is the bidirectional solute flux (BSF), including reverse solute flux (RSF) and forward solute flux (FSF). Herein, zwitterion functionalized carbon nanotubes (Z-CNTs) have been coated onto a commercial thin film composite (TFC) membrane, resulting in BSF mitigation via both electrostatic repulsion forces induced by zwitterionic functional groups and steric interactions with CNTs. At a coating density of 0.97 g m-2, a significantly reduced specific RSF was observed for multiple draw solutes, including NaCl (55.5% reduction), NH4H2PO4 (83.8%), (NH4)2HPO4 (74.5%), NH4Cl (70.8%), and NH4HCO3 (61.9%). When a synthetic wastewater was applied as the feed to investigate membrane rejection, FSF was notably reduced by using the coated membrane with fewer pollutants leaked to the draw solution, including NH4+-N (46.3% reduction), NO2--N (37.0%), NO3--N (30.3%), K+ (56.1%), PO43--P (100%), and Mg2+ (100%). When fed with real wastewater, a consistent water flux was achieved during semi-continuous operation with enhanced fouling resistance. This study is among the earliest efforts to address BSF control via membrane modification, and the results will encourage further exploration of effective strategies to reduce BSF.