Water Coagulation Research Articles

Analysis of the Interrelationship between Water Color and Coagulant Dose and the Possibility of Taking it into Account in Mathematical Modeling

The character of water chromaticity change in a water source, which is the main one for organizing water supply of a large urban agglomeration, is analyzed. It is shown that the correlation analysis characterizes the interrelationship between the coagulant dose and water chromaticity as noticeable (on the Cheddock scale), which predetermines the necessity to take into account water chromaticity as a parameter influencing the choice of coagulant dose. Variation series were constructed, empirical and theoretical functions of water chromaticity distribution by months were obtained. The possibility of modeling the reagent dose on the change of chromaticity taking into account specific conditions of practically constant influence of seasonal and random factors in the selected periods has been achieved. It is concluded that the chromaticity index makes a significant contribution to the value of the predicted value of coagulant dose.

The effect of immunosuppressive agent FTY-720 on coagulation, nitroxidergic lung activity and water balance in experimental antiphospholipid syndrome

Antiphospholipid syndrome (APS) is a systemic acquired autoimmune thrombophilia that leads to impaired non-respiratory lung functions due to the circulation of antiphospholipid antibodies, shifting the balance between the coagulation link of hemostasis and the anti-coagulation system towards hypercoagulation. The research examines the modulating effect of FTY-720 on the water balance, coagulation and NO-activity of the lungs under conditions of experimental APS. The functional activity of FTY-720 is largely due to its ability to bind to S1P1 receptors and block signaling pathways mediated by the interaction of the mediator sphingosine-1-phosphate with them. The main effect of FTY-720 is immunosuppression, which develops as a result of the drug’s receptor interaction predominantly with S1P1 receptors, resulting in the retention of autoreactive lymphocytes in lymph nodes, and prevents further spread of inflammation and damage. The experiments were conducted on 85 male rats, divided into groups as follows: The first group of animals (n = 30) was injected with cardiolipin antigen every other day for three weeks for APS modeling; the rats of the second group (n = 25), which served as a control group, were similarly injected with 0.9% NaCl; APS modeling and FTY-720 injection were combined on the remaining animals (n = 30). Three weeks later, arterial (art) and venous (ven) blood was taken, in which APTT and PT were determined using a hemocoagulometer CGL 2110 “Solar” and the corresponding coefficients of APPT of ven/art, PT of ven/ art were calculated. NO-activity was assessed by the content of plasma NO and NO bronchoalveolar lavage obtained by washing the extraction of the bronchopulmonary complex in anesthetized animals. To study the water balance of the lungs, the mass of moist and dried lungs was measured, were determined the total, extra- and intravascular fluid of the lungs. In APS, an increase in APTT and PT of arterial and venous blood was observed, an increase in the level of NO in bronchoalveolar lavages against the background of worsening nitroxidergic activity of the lungs – the NO index of ven/art decreased. There was a positive effect of FTY- 720 on the restoration of non-respiratory lung functions in APS.

In-situ manganese-aluminum-iron biochar derived from waste flocs for enhanced peroxymonosulfate oxidation: Role of Fe/Mn drives active species based on aluminum adsorption and synergistic promoted electron transfer

Conventional coagulation or enhanced coagulation water treatment produced mass floc sludge, which contained plenty of metals and organic matter. Floc sludge disposal and resource recycling was vital relevance and urgently needed. Here, we reported on the waste flocs recycling through in-situ manganese-aluminum-iron biochar (MAFBC) synthesized via one-step pyrolysis using potassium permanganate (KMnO4) oxidation- aluminum-iron composite flocculant coagulation for humic acid removal floc sludge as raw material. Compared with ex-situ loaded or similar types of biochar, MAFBC showed faster and efficient activation effect of peroxymonosulfate (PMS) to degrade tetracycline (TC). TC was rapidly removed within 1 min in MAFBC/PMS system with degradation rate constant Kobs was 1.825 min−1, which mainly attributed to the multiple promoting effects of manganese-aluminum-iron. Aluminum oxides facilitated TC adsorption and synergistic Fe/Mn further significantly promoted electron transfer on the surface of the MAFBC. Additionally, bimetallic structure of Fe/Mn and the CO functional group on MAFBC accelerated the formation of reactive species. The redox cycles of Fe2+/Fe3+ and Mn2+/Mn3+/Mn4+ promoted the formation of free radicals OH and SO4−. Moreover, O2– and 1O2 also assumed an important role for TC removal during active species evolution drived by Fe/Mn. This research provides a new perspective for in-situ design of economical and stable metal carbon-based water treatment activator, and make contributions to the utilization of waste flocs in water treatment.

Physical-chemical characterisation of an alum-based water treatment sludge in different raw water turbidity scenarios

Characterisation of the water treatment sludge (WTS) generated in drinking water treatment plants (DWTPs) is crucial to define alternatives for its adequate management, including potential reuse options. To define these alternatives, it is necessary to evaluate rainfall seasonality effect on WTS production and its physical and chemical characteristics. This study assessed the production and characterisation of four types of alum-based WTS. The WTS was generated in a pilot-scale system from different raw water turbidities (i.e., low: <5 NTU, medium: 5–10 NTU, high: ≥10 NTU, and very high turbidity: ∼300 NTU) and coagulant doses. To estimate WTS production, mathematical models based on variables such as raw water turbidity, coagulant dosage, and organic matter removed were used. The WTS characterisations included physical (solids and particle size distribution), chemical (metallic oxides, pH, mineral phases), and surface properties (functional groups and zero-charge point pH). The modified Kawamura model presented the best fit (R2 = 1.0, RMSE = 0.1062 and the lower Akaike Information Criterion) for the estimation of WTS production, indicating that at the DWTPs, it is possible to make sludge production projections using only two simple variables: coagulant dose and the raw water turbidity. The four types of WTS consist mainly of amorphous materials (45–65 %), featuring some mineral phases and exhibiting high contents of Al (Al2O3: 30–34 %), Si (SiO2: 21–26 %) and Fe (Fe2O3: 11–13 %). Nevertheless, very high turbidity WTS shows variations in its characteristics, notably a heightened content of clays. As a result of the high concentrations of Al and Fe, the WTS has the potential to be used as coagulants or for the recovery of coagulants, especially low turbidity WTS, which is produced from water with low turbidity and organic matter. The presence of aluminium–silicate clays and the surface functional groups of the silica network suggest that WTS, particularly very high turbidity WTS, also has the potential to be raw materials for generating adsorbents. The potential applications of WTS in coagulation and adsorption can be leveraged in wastewater treatment, promoting the circular economy in the water sector.

Modelling the predictive analysis of turbidity removal efficiency in the in-line coagulation and flocculation process

Coagulation and flocculation processes are commonly used in conventional water treatment plants to remove suspended solids from water. However, these methods often suffer from drawbacks such as high chemical consumption, sludge generation, and the need for huge areas, leading to high construction costs. To address these limitations, this study investigated the performance of in-line coagulation and flocculation processes as an alternative to conventional methods. The objectives were to determine the efficiency of in-line coagulation and flocculation, understand the underlying mechanisms, establish optimal operating conditions and design criteria, and to develop theoretical models for predicting turbidity removal efficiency in the in-line coagulation-flocculation process. Experiments were conducted using a continuous setup consisting of a static mixer and a 35-m helically coiled hydraulic tube flocculator.Various operating parameters, including water flow rate (100 – 800 L/hr), initial turbidity (20 – 200 NTU), and coagulant types (aluminum sulfate, poly aluminum chloride, aluminum chlorohydrate, and ferric chloride), were examined. The results demonstrated that aluminum sulfate was the appropriate coagulant for the water characteristics studied, and the in-line coagulation and flocculation processes achieved turbidity removal efficiencies of approximately 91 % under all operating conditions, with a notable 97 % removal efficiency achieved at a liquid flow rate of 600 L/hr, with a Gt value of 21,715 and an overflow rate of 2 m/hr. A prediction model of turbidity removal efficiency was developed, showing good agreement between experimental and predicted removal efficiency model, with an average deviation of about 20 %. This model can aid in determining optimal operating conditions and serve as a hybrid process in future water treatment systems, potentially applicable to other separation processes as well.

Study of Temperature Effect on Ferric Chloride Performance in Water Coagulation

Temperature has an essential function and becomes an important parameter in a coagulation process as itinfluences metal ion hydrolysis reaction rate. In order to get further explanation, a research using ferric chloride as a coagulant has been performed. The research aims tofind out more about the effect of temperature on coagulation performance using turbidity, floc size, ferric, and water content parameter. The temperature 5℃ - 45℃ with an interval of 5ºC has been investigated to simulate field (i.e. outside) measurements in winter, spring and autumn, and summer, respectively. The result shows coagulation performance isaffected by temperature elevation. Turbidity gets lower for temperature between 5℃-40℃ and gets higher for temperature 45℃. Floc size becomes larger for temperature 5℃-40℃ and becomes smaller as temperature increase.At temperature between 5ºC and 15ºC, the higher the temperature, the lower the ferric residue produced in coagulation water. For floc water contents, there is no virtually link between temperature and floc water contents. Temperature correlated well with turbidity value (-0.876) and floc size (0.985) but not correlated with ferric residue (0.366)and floc water content (0.179).

Microstructure and performance modification of PVDF ultrafiltration membrane via adjusting the composition of coagulation Bath

AbstractIn this paper, the effect of the composition of a nonsolvent bath on the physicochemical properties of the polyvinylidene fluoride (PVDF) ultrafiltration membranes were comprehensively investigated using the nonsolvent‐induced phase separation method. Three additives (ethanol, glycerol, or NaCl) were added to the water coagulation bath respectively to obtain different membranes. It was found that the microstructure of the membranes changed from finger‐like structure to the sponge‐like structure with the increase of additives concentration, which successfully improved the retention and mechanical properties of the membranes. In addition, the membrane surface became smoother and more hydrophilic. The membrane fabricated in 30 wt% glycerol bath exhibited outstanding comprehensive properties of retention and anti‐fouling, with a water flux of 243.5 L/(m2 h), a bovine serum albumin rejection of more than 90%, and a flux recovery rate of 97%. From mechanism analysis, the addition of ethanol, glycerol, or NaCl to the coagulation bath altered the thermodynamic stability of the polymer system, and slowed down the rate of solvent and nonsolvent diffusion from a kinetic perspective. This research provides important clues for optimizing the membrane properties, such as flux, rejection, and strength.

Suitability of inorganic coagulants for algae-laden water treatment: Trade-off between algae removal and cell viability, aggregate properties and coagulant residue

Inorganic coagulants could effectively precipitate algae cells but might increase the potential risks of cell damage and coagulant residue. This study was conducted to critically investigate the suitability of polyaluminum (PAC), FeCl3 and TiCl4 for algae-laden water treatment in terms of the trade-off between algal substance removal, cell viability, and coagulant residue. The results showed that an appropriate increase in coagulant dosage contributed to better coagulation performance but severe cell damage and a higher risk of intracellular organic matter (IOM) release. TiCl4 was the most destructive, resulting in 60.85% of the algal cells presenting membrane damage after coagulation. Intense hydrolysis reaction of Ti salts was favorable for the formation of larger and more elongated, dendritic structured flocs than Al and Fe coagulants. TiCl4 exhibited the lowest residue level and remained in the effluents mainly in colloidal form. The study also identified charge neutralization, chemisorption, enmeshment, and complexation as the dominant mechanisms for algae water coagulation by metal coagulants. Overall, this study provides the trade-off analyses between maximizing algae substance removal and minimizing potential damage to cell integrity and is practically valuable to develop the most suitable and feasible technique for algae-laden water treatment.

Diffusion coefficients during regenerated cellulose fibers formation using ionic liquids as solvents: Experimental investigation and molecular dynamics simulation

Regenerated cellulose fibers (RCFs) are an essential type of bio-based chemical fibers. The preparation of RCFs using ionic liquids (ILs) as solvents is an efficient utilization of ecological resources. Investigating the diffusion coefficients during RCFs formation using ILs as solvents is vital due to the potential impact of the interaction between ILs and coagulants on the morphology and properties of RCFs. The determination of diffusion coefficients during RCFs formation is challenging due to its instantaneous and simultaneous nature. For this research, the method and apparatus for measuring the diffusion coefficients during RCFs formation were established, and the diffusion coefficients of various IL and coagulant systems were also explored under different formation conditions. In addition, the relationship between the diffusion coefficient, the formation condition and the self-diffusion coefficient of ILs were investigated using numerical simulation and molecular dynamics simulation. The results demonstrated that the formation conditions, particularly the temperature and composition of coagulants, significantly impact the diffusion coefficient. Lowering the temperature of the coagulants and incorporating ethanol with lower polarity reduced the diffusion coefficient. The diffusion coefficient of 1-ethyl-3-methylimidazolium diethylphosphate ([Emim]DEP) in the ethanol coagulation bath was 0.79 × 10−9 m2·s−1 at 293 K, which was nearly twice as small as that in the water coagulation bath. These findings were validated by molecular dynamics simulations. Modifying the formation conditions can regulate the structure and properties of the RCFs by affecting the diffusion coefficients during RCFs formation.

Preparation of a Novel Lignocellulose-Based Aerogel by Partially Dissolving Medulla Tetrapanacis via Ionic Liquid.

A novel lignocellulosic aerogel, MT-LCA, was successfully prepared from MT by undergoing partial dissolution in an ionic liquid, coagulation in water, freezing in liquid nitrogen, and subsequent freeze-drying. The MT-LCA preserves its original honeycomb-like porous structure, and the newly formed micropores contribute to increased porosity and specific surface area. FT-IR analysis reveals that MT, after dissolution and coagulation, experiences no chemical reactions. However, a change in the crystalline structure of cellulose is observed, transitioning from cellulose I to cellulose II. Both MT and MT-LCA demonstrate a quasi-second-order kinetic process during methylene blue adsorption, indicative of chemical adsorption. The Langmuir model proves to be more appropriate for characterizing the methylene blue adsorption process. Both adsorbents exhibit monolayer adsorption, and their effective adsorption sites are uniformly distributed. The higher porosity, nanoscale micropores, and larger pore size in MT-LCA enhance its capillary force, providing efficient directional transport performance. Consequently, the prepared MT-LCA displays exceptional compressive performance and efficient directional transport capabilities, making it well-suited for applications requiring high compressive performance and selective directional transport.

Field Approach on the Effectiveness of Hydraulic Flocculator Followed By Sedimentation and Rapid Sand Filter

This research investigates the effectiveness of a hydraulic flocculator at the Kalanki Groundwater Treatment Project-Sipradi in Kalanki-Kathmandu. Hydraulic flocculation is a cost-effective alternative to mechanical flocculation, particularly beneficial for developing nations. The study involved determining the optimal Poly Aluminium Chloride (PACl) dosage through Jar Testing and assessing the flocculator's efficiency in the field with this dose. The research also analyzed other treatment units under various PACl doses to evaluate the Water Treatment Plant's operational conditions and the required PACl dose for efficient turbidity removal. The system included components like a deep well source, V-Notch weir tank, hydraulic flocculator, sedimentation tank, rapid sand filter (RSF), chlorinator, and clear water reservoir, with a 16-minute flocculator detention time. Baffle walls were strategically positioned at various intervals on-site. The study revealed that while sedimentation with coagulation achieved peak efficiency at a PACl dose of 80mg/l, it was less efficient than a 16-minute jar detention, likely due to sedimentation tank short-circuiting. Increasing the PACl dose from 20 mg/l to 80 mg/l improved overall unit efficiency, indicating the need for more mixing energy in the existing flocculator length for optimal results. The filter unit's efficiency remained consistent, whether with or without coagulation, at 57.69% and 54.10%, respectively. These results emphasize the importance of further investigation to enhance water treatment processes and coagulant dosages for improved effectiveness in this critical field.

Ion Exchange Resins and their Applications in Water Treatment and Pollutants Removal from Environment: A Review

Ion exchange resin is a porous polymer with a high molecular weight. It has a few groups that can be exchanged into ions in the solution it comes into contact with. Ion exchange resins are available in different types and are widely employed in wastewater treatment. It removes unwanted ions from waste water, because it can exchange unwanted ions with its functional group. Until now, ions exchange mainly employed for the removal of different compounds from water, including dissolved organic matter and dissolved organic carbon, nitrate, copper, N-nitrosodimethylamine, fluoride, Nickel, boron, sulfamethazine, trihalomethanes (THMs) etc. In industry, various techniques are available for condensate water treatment, including flotation, membrane, sedimentation, coagulation, precipitation, chemical adsorption, filtration, catalytic oxidation, and electrochemical techniques. But existing techniques or processes are not feasible for water treatment in a confined place due to few advantages, including less efficiency in purification, being expensive, maintenance challenges, and high energy requirements. In contrast, ion exchange resins benefit from high separation selectivity, simple handling, and reusable resin. Few resins are too much costly, but being they are reusable, it makes them sustainable and cost-effective. Significant research is being conducted worldwide to uncover the potential effects of ion exchange resins. This review discussed their use in environmental cleanup, water treatment, and operational feasibility with multiple factors.

The comprehensive review of practical approaches of woe separation based on magnetic impact

The article presents an analytical review of magnetic oil treatment, which is an innovative method for preventing complications such as wax deposits and high viscosity of oil. It is concluded that the magnetic treatment of oil is associated with a change in the electrospin state and the evolution of radical pairs of asphaltenes, which are complex with ferromagnetic particles. This leads to an increase in intrinsic magnetic moments, structural rearrangement of supramolecular asphaltene structures and a change in the rheological parameters of oil. The destruction of the «armor shell» occurs due to the influence of the magnetic field on these complexes, which leads to the prevention of the formation of wax and salt deposits and the acceleration of water coagulation processes. The factors of effective magnetic treatment are oils with a high content of iron compounds, salt ions. The effective parameters of magnetic processing are generalized: high values of magnetic induction (up to 1 T), pulse repetition frequency from 5 to 30 Hz. The main advantages and disadvantages of permanent and alternating magnetic field devices are analyzed. A review of the results of industrial and laboratory studies on magnetic oil treatment is carried out. The maximum efficiency in reducing viscosity is 375%, reducing the deposition rate of paraffin is 87.5%, reducing the mass of wax deposits is 50%, reducing the corrosion rate is 45%. Keywords: magnetic treatment of crude oil; influence magnetic field on the oil; wax deposits; high-viscosity oil; heavy oil.

Removal of Per- and Polyfluoroalkyl substances by anion exchange resins: Scale-up of rapid small-scale column test data

Anion exchange (IX) is a readily implementable water treatment method that can effectively remove per- and polyfluoroalkyl substances (PFAS). The overarching objective of this research was to predict PFAS removal in full- or pilot-scale packed-bed IX resin contactors from rapid small-scale column test (RSSCT) data. Specific objectives were to (1) assess the effects of IX resin crushing on total anion exchange capacity and packed bed density, (2) determine the effects of initial PFAS concentration on PFAS uptake capacity, (3) determine the rate-limiting step controlling PFAS uptake kinetics, (4) determine the effects of hydraulic loading rate on PFAS uptake capacity, and (5) link constant diffusivity RSSCT data to pilot test data to develop a scale-up protocol. Experiments were conducted with two single-use IX resins and three water matrices, including coagulated surface water and groundwater.Crushing IX resin did not substantially change the bed density and total anion exchange capacity, but the morphology of particles changed from almost perfectly spherical to irregularly shaped. PFAS uptake capacity was independent of influent PFAS concentrations in the 30–300 ng/L range. This finding facilitated the development of an RSSCT scale-up approach because influent PFAS concentrations in RSSCTs and corresponding pilot tests often differ. Biot number values and data from interrupted RSSCTs demonstrated that film diffusion or a combination of film diffusion and intraparticle diffusion controls the rate of PFAS uptake by IX resins. From RSSCTs with identical empty bed contact times but different hydraulic loading rates (vf), PFAS uptake capacity was found to be a function of the square root of the product of Sherwood number and particle shape factor (Sh×ϕ). Using a constant diffusivity RSSCT design with a reduced vf, full- or pilot-scale PFAS breakthrough data can therefore be predicted by multiplying the bed volumes of water treated in the RSSCT by a factor of (Shpilot×ϕpilot)/(ShRSSCT×ϕRSSCT) . This research will support the design of future IX treatment processes in the context of PFAS remediation and drinking water treatment.

New method of producing a more efficient coagulant for the treatment of water from seeds of moringa oleifera

The coagulation is essential in raw water treatment. The most used coagulants are often of chemical origin and expensive and their use generates non-biodegradable residues. This is why innovative studies on the synthesis of natural coagulants based on plant extracts are very important. This study presents a new method of producing a coagulant for the treatment of water from seeds of moringa oleifera. The application of the new method is done in several steps: Harvesting moringa oleifera seeds, shelling, crushing the seeds, extracting oil from moringa oleifera powder, extracting salts from powder from moringa seeds oleifera, microfiltration with a 0.2 µm filter and lyophilization which gives the final product in dry form. We used the resulting product for coagulation of lake water with an initial turbidity of 40 NTU. This treatment reduced the turbidity of the water by almost 95 % when we used 0.7 mg of this coagulant per liter of water. Moringa has previously been used to produce coagulant but the peculiarity of this study is that it takes a very small amount of the synthesized product to effectively treat water.­The results of this research work have shown that the coagulant produced rom the seeds of Moringa oleifera can be used effectively for the treatment of surface water.­The residual turbidity obtained after the treatment of lake water with the coagulant produced was in accordance with the drinking water standard according to the World Health Organization (WHO) (less than 5 NTU).­The coagulant produced by this new method from moringa oleifera seed is an alternative to aluminum sulfate coagulant for water treatment.

A novel interfacial polymerization assisted phase inversion process for the facile fabrication of ion-selective nanofiltration membranes

Interfacial polymerization (IP) and non-solvent induced phase inversion (NIPS) are the two most commonly used mainstream technologies to fabricate separation membranes. Taking their advantages, we developed a simple, facile and scalable method to integrate the IP and NIPS processes together for the fabrication of ion-selective nanofiltration membranes. Herein, amphiphilic polysulfone block hyperbranched polyglycerol (PSf-b-hPG) copolymer was synthesized and blended with polyethylene imide (PEI) to prepare a polymer casting solution in organic solvents. After casted into the liquid film of PSf-b-hPG and PEI blending solution, it was then immersed into a cross-linking solution with 0.2 wt.% trimethylchloride (TMC) in n-hexane for the generation of the polyamide layer first on top of the liquid film, and finally transferred into a water coagulation bath for the formation of the porous matrix of PSf-b-hPG membrane. The fabricated membrane exhibited a high water permeance of 12.57 L m-2h−1 bar−1 and a high separation factor of 25.08 towards Mg2+ and Li+ ions, which is superior to the perm-selectivity of the most reported nanofiltration membranes. This novel and facile process can be directly applied to the NIPS manufacturing line, eliminating a separate IP production line and holding immense potentials and advantages in scale-up production.

Defect-free asymmetric Matrimid® gas separation membranes using dihydrolevoglucosenone (Cyrene™) as a greener polar aprotic solvent than traditional solvents

Industrial membrane manufacturing via nonsolvent-induced phase separation (NIPS) generates large volumes of solvent-contaminated wastewater. An effective solution is to reduce the inherent toxicity of NIPS casting solutions, or dopes, by substituting traditional polar aprotic solvents with potentially benign alternatives such as dihydrolevoglucosenone (Cyrene™). This study demonstrates the reproducible preparation of high-flux defect-free asymmetric Matrimid® gas separation membranes via dry/wet NIPS using Cyrene™ as a majority dope formulation component. Defect-free membrane performance, as benchmarked for pure gas H2/N2 and O2/N2 separations, is maximized with high loadings of Cyrene™ relative to the volatile co-solvent tetrahydrofuran (THF) in casting solutions (volume ratios up to 3.20:1), which exceed the value of 1.68:1 used for Udel® polysulfone in our previous study. Cyrene™'s poor thermodynamic compatibility with the water coagulant and ability to produce highly viscous dopes ensure minimization and/or elimination of sublayer macrovoids while enabling defect-free membrane preparation at low (i.e., 12–14 wt %) Matrimid® and THF concentrations. Defect-free H2 permeance values up to 164 ± 14 GPU were achieved with a combination of high Cyrene™:THF volume ratios, low Matrimid® concentrations, and short dry step times (i.e., <15 s). Membrane performance achieved in this study matches or exceeds other literature reports of defect-free asymmetric Matrimid® membranes prepared with traditional NIPS solvents.

Self-supporting biocatalytic polyelectrolyte complex hollow fiber membranes via salt-dilution induced phase separation

The potential use of biocatalytic membranes in industries such as water treatment, pharmaceuticals, and medicine has attracted much interest in recent years. However, the use of organic solvents in traditional membrane fabrication techniques presents a challenge in the direct integration of enzymes during the membrane production. Thus, enzyme immobilization relies on consecutive modification steps (coating, binding, activation). Yet, recent progress in membrane fabrication using all-aqueous phase inversion of polyelectrolyte complexes (PEC) enables the direct incorporation of enzymes in the polymer solution. We present the fabrication of free-standing, defect-free and mechanically stable biocatalytic PEC hollow fiber membranes via the salt-dilution induced phase separation method. A polymer solution containing poly(sodium-4-styrenesulfonate) (PSS), poly(diallyldimethylammonium chloride) (PDADMAC), KBr, and the enzyme alkaline phosphatase (ALP) was extruded through a spinneret with a mixture of water and glycerol as lumen fluid into a water coagulation bath at 0 °C. The mechanical stability of the fibers is tuned by subsequent photo-induced cross-linking using 4,4’-diazidostilbene-2,2’-difulfonate tetrahydrate (DAS) and UV light. The resulting membranes have a molecular weight cut-off of 400Da, a pure water permeance of 1.5LMH/bar, and a burst pressure of 7bar. The immobilization of ALP proves successful, as the immobilized shows similar catalytic activity to that of the free enzyme, and both storage and thermal stability are improved. Moreover, the enzymes retain 70% of their initial activity after UV cross-linking with DAS and maintain their catalytic activity after repeated wash and filtration cycles. This work highlights the versatility of the fabrication of polyelectrolyte complex hollow fiber membranes via the salt-dilution induced phase separation, serving as a platform technology for the fabrication of porous, selective, and bioactive membranes.

Significance of ozonation on surfactant-polymer flooding produced water coagulation: Water quality deterioration inhibition, high-standard reinjection and mechanism

Surfactants and polymers are extensively being used to enhance oil recovery resulting in the generation of surfactant-polymer (SP) flooding produced water, which is more challenging to treat for reinjection compared with conventional produced water. Aiming at high-standard SP flooding produced water reinjection, this study investigated the coagulation-based treatment processes for the treatment of SP flooding produced water. The conventional coagulation process with two typical coagulants, poly-aluminum chloride (PAC) and poly-ferric sulfate (PFS), was applied. However, the effluent did not meet the reinjection requirements for suspended solids (SS) ≤ 2 mg/L, oil ≤ 6 mg/L and median diameter d50 ≤ 1.5 μm according to the water quality standard for oilfield injecting waters in clastic reservoirs (SY/T 5329–2012). The presence of adsorbed surfactant (betaine) and polymer (hydrolyzed polyacrylamide, HPAM) on oil and suspended solids increased the difficulties in agglomeration and charge-neutralization. In addition, water quality deterioration occurred within 5 h leading to increased turbidity, suspended solids and d50. X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis implied that water quality deterioration was caused by souring (producing sulfide), leading to the generation of suspended solids mainly containing sulfur and calcium carbonate (CaCO3). To address these challenges, the pre-ozonation coagulation (POC) and hybrid ozonation-coagulation (HOC) processes were compared. The effluent from both processes, using either PAC or PFS, met the reinjection requirements while inhibiting water quality deterioration. Additionally, higher removal efficiency and significantly reduced optimal ozone dosage were also achieved in the HOC process compared with the POC process. The enhanced generation of hydroxyl radicals (•OH) and polymeric hydrolysed coagulant species in the HOC process contributed to higher removal efficiency of HPAM, betaine and COD. Kinetics analysis revealed that •OH oxidation and coagulation played important roles in betaine and HPAM removal, respectively. The reaction pathways of betaine and HPAM in the ozonation and HOC processes were also analysed. Furthermore, the HOC process can effectively inhibit the accumulation of small molecular weight organic matter, facilitating the simultaneous coagulation.

Microstructural Engineering of Flow Battery Electrodes with Non-Solvent Induced Phase Separation

Rising levels of greenhouse gases urge the decarbonization of human activities. Electrification of strategic sectors such as transport, industry, and heating necessitates affordable, safe, and dispatchable large-scale energy storage systems. Redox flow batteries (RFBs) stand as a promising long-duration and large-scale energy storage technology due to their design features[1]. Ongoing research focuses on engineering key cell components (e.g. membranes, electrodes, active materials) to improve cost competitiveness. This work focuses on the fabrication of novel porous carbon electrodes which strongly influence the performance and cost of the technology. The requirements for porous electrodes liquid-phase electrochemical reactors are contradictory: a large surface area is needed to overall exchange current density, but also minimal pressure losses to decrease pumping costs. Additionally, surface properties of the electrode dictate the reaction kinetics whereas its microstructure controls the mass transport of the reactants within the reactor area[2]. However, the current state-of-the-art porous electrodes for RFBs consists of carbon-fiber materials repurposed from other electrochemical technologies (e.g. polymer electrolyte fuel cells) which do not offer a favorable tradeoff between transport properties and surface area. Additionally, their production involves complex manufacturing processes resulting in high cost and limited morphological versatility. Therefore, there is a need to develop alternative synthetic platforms which offer tailorable microstructures and surface properties to match the requirements of emerging electrochemical applications, such as redox flow batteries. In this work, we draw inspiration from the membrane technology and employ non-solvent induced phase separation (NIPS) as a method to synthesize porous carbon electrodes for RFBs[3,4].Here, we present our latest efforts to develop a manufacturing route enabling the control of microstructural features of carbonaceous porous electrodes for RFBs. The microstructure of the carbon scaffold is determined by the nature and composition of the polymer blend used to cast the electrode precursor. We use polyacrylonitrile as scaffold precursor and polyvinylpyrrolidone as a pore forming agent, dissolved in an organic solvent (i.e., dimethylformamide, dimethylsulfoxide or N-methylpyrrolidone). The polymer blends were cast into a mold and immersed in a water coagulation bath prior to being stabilized (270 °C) and carbonized (1050 °C). Various process parameters (e.g. polymer concentration, bath temperature, solvent type) governing the final electrode properties were leveraged to control structural features, opening new opportunities for the fabrication of diverse microstructures (i.e., porosity gradient, isoporosity and with macrovoids). Electrochemical double layer capacitance and pressure drop measurements show an increased design space compared to carbon-fiber electrodes, confirming the versatility of the synthetic route. Microstructural analysis of the prepared NIPS electrodes reveals two porosity domains: large finger-like macrovoids (throat diameter >50 μm) and smaller interconnected microvoids (pore diameter 2-15 μm). Flow cell polarization and electrochemical impedance spectroscopy measurements in two common flow battery electrolytes, an Fe2+/Fe3+ single electrolyte and vanadium full cell, show improvements in performance compared to traditional electrodes. An increase in the polymer concentration of the polymer blend solution produced NIPS electrodes with smaller pores and resulted in better mass transport within the electrode. When the temperature of the coagulation bath was increased to 40 ºC, the electrode has higher electrochemically active surface area, producing a significant power increase in the sluggish vanadium electrolyte. Overall, the NIPS electrodes operate at significantly lower activation and mass transport overpotentials in all-vanadium RFBs, generating higher electrical power at the expense of a slight pressure drop increase. Although preliminary, we demonstrate the potential of NIPS to manufacture electrodes with tailorable microstructures for convection-enhanced electrochemical technologies.[1] T. M. Gür, Energy Environ. Sci. 2018, 11, 2696.[2] A. Forner-Cuenca, E. E. Penn, A. M. Oliveira, F. R. Brushett, J. Electrochem. Soc. 2019, 166, A2230.[3] R. R. Jacquemond, C. T.-C. Wan, Y.-M. Chiang, Z. Borneman, F. R. Brushett, K. Nijmeijer, A. Forner-Cuenca, Cell Reports Physical Science 2022, 3, 100943.[4] C. T.-C. Wan, R. R. Jacquemond, Y.-M. Chiang, K. Nijmeijer, F. R. Brushett, A. Forner-Cuenca, Adv. Mater. 2021, 10. Figure 1