A simple method to prepare anion exchange membrane by PVA/EVOH/MIDA for acid recovery by diffusion dialysis.

Given the substantial environmental pollution from industrial expansion, environmental protection has become particularly important. Nowadays, anion exchange membranes (AEMs) are widely used in wastewater treatment. With the use of polyvinyl alcohol (PVA), ethylene-vinyl alcohol (EVOH) copolymer, and methyl iminodiacetic acid (MIDA), a series of cross-linked AEMs were successfully prepared using the solvent casting technique, and the network structure was formed in the membranes due to the cross-linking reaction between PVA/EVOH and MIDA. Fourier transform infrared spectrometer, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy were used to analyze the prepared membranes. At the same time, its comprehensive properties which include water uptake, linear expansion rate, ion exchange capacity, thermal stability, chemical stability, and mechanical stability were thoroughly researched. In addition, diffusion dialysis performance in practical applications was also studied in detail. The acid dialysis coefficient (UH+) ranged from 10.2 to 35.6 × 10-3 m/h. Separation factor (S) value ranged from 25 to 38, which were all larger than that of the commercial membrane DF-120 (UH+: 8.5 × 10-3 m/h, S: 18.5). The prepared membranes had potential application value in acid recovery.

In situ potassium and hydrogen ion exchange into a cubic zirconium silicate microporous material.

The selective separation of ions from aqueous systems, and even in the human body, is a crucial to overall environmental management and health. Nanoporous materials are widely known for their selective removal of cations from aqueous media, and therefore have been targeted for use as a pharmaceutical to treat hyperkalemia. This study investigated the detailed crystallographic molecular mechanisms that control the potassium ion selectivity in the nanoporous cubic zirconium silicate (CZS) related materials. Using time-resolved in situ Raman spectroscopy and time-resolved in situ X-ray diffraction, the selectivity mechanisms were determined to involve a synchronous cation-cation repulsion process that serves to open a favorable coordination bonding environment for potassium, not unlike the ion selectivity filter process found in potassium ion channels in proteins. Enhancement of ion exchange was observed when the CZS material was in a partial protonated state (≈3:1 Na:H), causing an expansion of the unit-cell volume, enlargement of the 7 member-ring window, and distortion of framework polyhedra, which allowed increased accessibility to the cage structures and resulted in rapid irreversible potassium ion exchange.

Cutting-edge technologies and relevant reaction mechanism difference in treatment of long- and short-chain per- and polyfluoroalkyl substances: A review.

Per- and polyfluoroalkyl substances (PFAS) are emerging contaminants. Compared with short-chain PFAS, long-chain PFAS are more hazardous. Currently, little attention has been paid to the differences in reaction mechanisms between long-chain and short-chain PFAS. This pressing concern has prompted studies about eliminating PFAS and revealing the mechanism difference. The reaction rate and reaction mechanism of each technology was focused on, including (1) adsorption, (2) ion exchange (IX), (3) membrane filtration, (4) advanced oxidation, (5) biotransformation, (6) novel functional material, and (7) other technologies (e.g. ecological remediation, hydrothermal treatment (HT), mechanochemical (MC) technology, micro/nanobubbles enhanced technology, and integrated technologies). The greatest reaction rate k of photocatalysis for long- and short-chain PFAS high up to 63.0 h-1 and 19.7 h-1, respectively. However, adsorption, membrane filtration, and novel functional material remediation were found less suitable or need higher operation demand for treating short-chain PFAS. Ecological remediation is more suitable for treating natural waterbody for its environmentally friendly and fair reaction rate. The other technologies all showed good application potential for both short- and long-chain PFAS, and it was more excellent for long-chain PFAS. The long-chain PFAS can be cleavaged into short-chain PFAS by C-chain broken, -CF2 elimination, nucleophilic substitution of F-, and HF elimination. Furthermore, the application of each type of technology was novelly designed; and suggestions for the future development of PFAS remediation technologies were proposed.

Selective adsorption in ion exchange membranes: The effect of solution ion composition on ion partitioning.

Electrodialysis is a water desalination technology that enables selective separation of ions, making it a promising solution for sustainable water reuse. The selectivity of the process is mainly determined by the properties of ion exchange membranes that can vary depending on the composition of ions in water, such as water uptake and charge density. In this work, we studied selective adsorption of Na+ and K+ ions in various ion exchange membranes considering the effect of solution ion composition on membrane water volume fraction. For that purpose, we conducted membrane adsorption experiments using solutions with Na+ and K+ ions with different ion compositions including Li+, Ca2+ or Mg2+ ions at different concentrations (0.001 - 0.25 M). The experiments showed that with the total ion concentration and the amount of divalent ions in solution, the membrane water volume fraction decreases while the selective adsorption of the smaller (hydrated) K+ ions over the Na+ ions in the membrane increases. We developed a theoretical framework based on Boublik-Mansoori-Carnahan-Starling-Leland (BMCSL) theory to describe the effect of membrane water volume fraction on selective adsorption of the ions by including volumetric effects, such as size exclusion. The developed framework was used to describe ion partitioning results of the membrane adsorption experiments. In addition, the effect of solution ion composition on selective ion removal during electrodialysis operation was evaluated using experimental data and theoretical calculations. The results of this study show that considering volumetric effects can improve the ion partitioning description in ion exchange membranes for solutions with various ion compositions.

Evidence from experiments, modeling, and field observations for effects of increased salinization on re-distribution of sediment base cations in Taihu Lake, China.

Taihu Lake, the third largest freshwater lake in China, has experienced rapid salinization in the past decades; however, little is known about the impact of sodium (Na) on ion exchange in the lake environment. To explore the potential effect of increased Na on the migration of base cations (Ca and Mg) and resulting redistribution between the water and sediment, we used the adsorption-exchange experiment, MINTEQ modeling to explore the cation exchange induced by high Na input, and its impact on the redistribution of Ca and Mg in Taihu different media. The results indicated that exchanged quantity of Ca and Mg increased with time, and the exchange process reached 90% during 0-4 h and reached equilibrium after 24 h under 100 mg/L Na (the maximum Na concentration in Taihu sediment pore water). Our MINTEQ modeled result indicated that the exchanged quantity of Ca and Mg increased with the increasing Na concentration, with Ca being preferably exchanged over Mg at the same Na concentration. The MINTEQ model further predicted that, in the Taihu lake environment, the exchange adsorption would reach the equilibrium at the concentration of 6000 mg/L Na, with exchanged Ca2+ and Mg2+ accounting for 47% and 55% of the total exchangeable Ca and Mg in the sediment, respectively. Although current Na-induced exchange in the Taihu lake has been far from the equilibrium, the MINTEQ result confirmed the existence of this reaction and predicted the potential redistribution of base cations or Ca/Mg ratio in the lake sediment and water phase with further Na increase. Furthermore, our field observations not only confirmed the existence of Na-induced cation exchange in this lake environment but also were generally in agreement with our experimental and modeled results. The increased salinization-induced ion exchange would alter the re-distribution of base cations and the resulting potential ecosystem consequences should be given close attention in this large freshwater lake.

Mobility of Condensed Counterions in Ion-Exchange Membranes: Application of Screening Length Scaling Relationship in Highly Charged Environments.

Ion-exchange membranes (IEMs) are widely used in water, energy, and environmental applications, but transport models to accurately simulate ion permeation are currently lacking. This study presents a theoretical framework to predict ionic conductivity of IEMs by introducing an analytical model for condensed counterion mobility to the Donnan-Manning model. Modeling of condensed counterion mobility is enabled by the novel utilization of a scaling relationship to describe screening lengths in the densely charged IEM matrices, which overcame the obstacle of traditional electrolyte chemistry theories breaking down at very high ionic strength environments. Ionic conductivities of commercial IEMs were experimentally characterized in different electrolyte solutions containing a range of mono-, di-, and trivalent counterions. Because the current Donnan-Manning model neglects the mobility of condensed counterions, it is inadequate for modeling ion transport and significantly underestimated membrane conductivities (by up to ≈5× difference between observed and modeled values). Using the new model to account for condensed counterion mobilities substantially improved the accuracy of predicting IEM conductivities in monovalent counterions (to as small as within 7% of experimental values), without any adjustable parameters. Further adjusting the power law exponent of the screen length scaling relationship yielded reasonable precision for membrane conductivities in multivalent counterions. Analysis reveals that counterions are significantly more mobile in the condensed phase than in the uncondensed phase because electrostatic interactions accelerate condensed counterions but retard uncondensed counterions. Condensed counterions still have lower mobilities than ions in bulk solutions due to impedance from spatial effects. The transport framework presented here can model ion migration a priori with adequate accuracy. The findings provide insights into the underlying phenomena governing ion transport in IEMs to facilitate the rational development of more selective membranes.

Recovery of metal ion resources from waste lithium batteries by in situ electro-leaching coupled with electrochemically switched ion exchange.

A new green pathway of in situ electro-leaching coupled with electrochemically switched ion exchange (EL-ESIX) technology was developed for the separation and recovery of valuable metal ions from waste lithium batteries. By using the in situ electro-leaching, the leaching rates of Li+ and Co2+ from the prepared LiCoO2 film electrodes reached 100 % and 93.30 %, respectively, under the combined effect of the acidic microenvironment formed by the anodic electrolytic water and electrostatic repulsion. Subsequently, the Li+ in the electrolyte was further extracted by an electrochemically switched ion exchange (ESIX) process using LiMn2O4 as the film electrode, and Li+ was further enriched in the eluate by a cyclic adsorption and desorption process. The results indicate that the in situ electro-leaching has significant advantages over powder leaching, and for the recycling of waste lithium batteries, the final lithium recovery rate reached 94.51 % by using this in situ EL-ESIX technology.

Elucidating uranium interactions with synthetic Na-P1 zeolite/Ca2+-substituted alginate composite granules through batch and spectroscopic studies: Emphasizing the significance of ion exchange and complexation.

Uranium, a key member of the actinides series, is radioactive and may cause severe environmental hazards once discharged into the water due to high toxicity. Removal of uranium via adsorption by applying tailored, functional adsorbents is at the forefront of tackling such pollution. Here, we report the optimized functionalization of the powder coal fly-ash (CFA) derived Na-P1 synthetic zeolite to the form of granules by employing the biodegradable polymer-calcium alginate (CA) and their application to remove aqueous U. The optimized synthesis showed that granules are formed at the CA concentration equals to 0.5 % wt., and that application of 1% wt. solution renders the most effective U scavengers. The maximum U adsorption capacity (qmax) increases significantly after CA modification from 44.48 mgU/g for native, powder Na-P1 zeolite to 62.53 mg U/g and 76.70 mg U/g for 0.5 % wt. and 1 % wt. CA respectively. The U adsorption follows the Radlich-Peterson isotherm model, being the highest at acidic pH (pHeq∼4). The U adsorption kinetics reveals swift U uptake, reaching equilibrium after 2h for 1 % ZACB and 3 h for 0.5 % wt. ZACB following the pseudo-second-order (PSO) kinetic model. SEM-EDXS investigation elucidates that adsorbed U occurs onto materials as an inhomogenous, well-dispersed, and micrometer-scale aggregate. Further, XPS and µ-XRF spectroscopies complementarily confirmed the hexavalent oxidation state of adsorbed U and its altered distribution on ZACBs with varying CA concentrations. U distribution was probed "in-situ" onto materials while correlations between the major elements (Al, Si, Ca, U) contributing to U scavenging were calculated and compared. Finally, a real-life coal mine wastewater (CMW) polluted by 238U and 228,226Ra was successfully purified, satisfying WHO guidelines after treatment using ZACBs. These findings offer new insights on successful yet optimized Na-P1 zeolite modification using biodegradable polymer (Ca2+-exchanged alginate) aimed at efficient U removal, displaying a near-zero environmental impact.

Ion exchange synthesis of copper-based hydroxyapatite for the catalytic degradation of phenol.

Hydroxyapatite (HAP) is a material renowned for its exceptional capabilities in adsorbing and exchanging heavy metal ions, making it a widely employed substance within the environmental domain. This study aims to present a novel material, namely copper-HAP (Cu-HAP), which was synthesized via an ion exchange method. The resulting material underwent comprehensive characterization using scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and Brunauer-Emmett-Teller (BET) analysis. Subsequently, based on the principle of the Fenton-like oxidation reaction, the material was used for the degradation of phenol. The outcomes of the investigation revealed that the optimal preparation conditions for the catalyst were achieved at a temperature of 40 °C, a pH value of 5, and a relative dosage of Cu-HAP at 100 mg/g. Under the reaction conditions of a catalyst dosage of 2 g/L, a 30% hydrogen peroxide concentration of 30 mM, a phenol concentration of 20 mg/L, a pH value of 6, a temperature of 40 °C, and the degradation rate of phenol impressively reached 98.12%. Furthermore, the degradation rate remained at 42.31% even after five consecutive cycles, indicating the promising potential of Cu-HAP in the treatment of recalcitrant organic compounds within this field.

Using selectivity to evaluate aqueous- and resin-phase denitrification during biological ion exchange.

An increased fertilizer application for agricultural purposes has resulted in increased nitrate (NO3-) levels in surface water and groundwater around the globe, highlighting demand for a low-maintenance NO3- treatment technology that can be applied to nonpoint sources. Ion exchange (IEX) is an effective NO3- treatment technology and research has shown that bioregeneration of NO3- laden resins has the potential to minimize operational requirements and brine waste production that often prevents IEX application for decentralized treatment. In this work, batch denitrification experiments were conducted using solutions with low IEX selectivity capable of supporting the growth of denitrifying bacteria, while minimizing NO3- desorption from resins, encouraging resin-phase denitrification. Although only 15% of NO3- was desorbed by the low selectivity solution, this initial desorption started a cycle in which desorbed NO3- was biologically transformed to NO2-, which further desorbed NO3- that could be biotransformed. Denitrification experiments resulted in a 43% conversion rate of initially adsorbed NO3-, but biotransformations stopped at NO2- due to pH limitations. The balance between adsorption equilibria and biotransformation observed in this work was used to propose a continuous-flow reactor configuration where gradual NO3- desorption might allow for complete denitrification in the short retention times used for IEX systems.

Optimization of the chemolithotrophic denitrification of ion exchange concentrate using hydrogen-based membrane biofilm reactors.

A H2-based membrane biofilm reactor (MBfR) was used to remove nitrate from a synthetic ion-exchange brine made up of 23.8 g L-1 NaCl. To aid the selection of the best nitrate management strategy, our research was based on the integrated analysis of ionic exchange and MBfR processes, including a detailed cost analysis. The nitrate removal flux was not affected if key nutrients were present in the feed solution including potassium and sodium bicarbonate. Operating pH was maintained between 7 and 8. By using a H2 pressure of 15 psi, a hydraulic retention time (HRT) of 4 h, and a surface loading rate of 13.6 ± 0.2 g N m-2 d-1, the average nitrate removal flux was 3.3 ± 0.6 g N m-2 d-1. At HRTs of up to 24 h, the system was able to maintain a removal flux of 1.6 ± 0.2 g N m-2 d-1. Microbial diversity analysis showed that the consortium was dominated by the genera Sulfurimonas and Marinobacter. The estimated cost for a 200 m3/h capacity, coupled ion exchange (IX) + MBfR treatment plant is 0.43 USD/m3. This is a sustainable and competitive alternative to an IX-only plant for the same flowrate. The proposed treatment option allows for brine recycling and reduces costs by 55% by avoiding brine disposal expenses.

The effect of calcium removal from skim milk by ion exchange on the properties of the ultrafiltration retentate.

New processes are needed to produce concentrated milk feedstocks with tailored calcium content, due to the direct link between calcium concentration and final product texture and functionality. Skim milk treatment with cation exchange resin 1% (w/v) or 2% (w/v) prior to ultrafiltration to a volumetric concentration factor (VCF) of 2.5 or 5 successfully decreased the calcium concentration by 20-30% and produced concentrates with solids content at ∼22-24 g 100 g-1 at a VCF of 5. Calcium reduction partially solubilized the casein micelles, increasing the concentration of soluble protein and individual caseins, leading to decreased turbidity but increased protein hydration and hydrophobicity. Decalcification (2% (w/v) resin treatment) reduced thermal stability, significantly decreasing the denaturation temperature of α-lactalbumin and ß-lactoglobulin in the milk by ∼3 °C and ∼1 °C respectively. Filtration was also altered, reducing permeation flux and the gel concentration and increased filtration time. When combined, calcium reduction and filtration altered functional properties including soluble calcium, soluble protein and sedimentable solids, with increased milk protein hydration also contributing to increased viscosity. This study provides a route to produce calcium-reduced milk concentrates with potential for use in retentate-based dairy products with tailored functionality.

Embedded Mo/Mn Atomic Regulation for Durable Acidity-Reinforced HZSM-5 Catalyst toward Energy-Efficient Amine Regeneration.

Metal-molecular sieve composites with high acidity are promising solid acid catalysts (SACs) for accelerating sluggish CO2 desorption processes and reducing the energy consumption of CO2 chemisorption systems. However, the production of such SACs through conventional approaches such as loading or ion-exchange methods often leads to uncontrolled and unstable metal distribution on the catalysts, which limits their pore structure regulation and catalytic performance. In this study, we demonstrated a feasible strategy for improving the durability, surface chemical activity, and pore structure of metal-doped HZSM-5 through bimetallic Mo/Mn modification. This strategy involves the immobilization of Mo-O-Mn species confined in an MFI structure by regulating MoO42- anions and Mn2+ cations. The embedded Mn/Mo species of low valence can strongly induce electron transfer and increase the density of compensatory H+ on the MoMn@H catalyst, thereby reducing the CO2 desorption temperature by 8.27 °C and energy consumption by 37% in comparison to a blank. The durability enhancement and activity regulation method used in this study is expected to advance the rational synthesis of metal-molecular sieve composites for energy-efficient CO2 capture using amine regeneration technology.

The significance of heterophasic ion exchange in active biomonitoring of heavy metal pollution of surface waters.

We have carried out studies to examine the possibility of using biosorbents: the epigeic mosses Pleurozium schreberi (Willd. ex Brid.) Mitt., and the epiphytic lichens Hypogymnia physodes (L.) Nyl. in active biomonitoring of heavy metal pollution of surface waters. The dried sea algae Palmaria palmata (L.) Weber & Mohr were used as the third biosorbent. The studies were conducted in the waters of the Turawa Reservoir, a dam reservoir with a significant level of eutrophication in south-western Poland. Incremental concentrations of Mn, Ni, Zn, Cu, Cd, and Pb were determined in the exposed samples. It was shown that a 2-h exposure period increases the concentration of some metals in the exposed samples, even by as much as several hundred percent. High increments of nickel concentrations in the algae Palmaria palmata (mean: 0.0040 mg/g, with the initial concentration of c0 < 0.0016 in the algae) were noted, with negligible increments in concentrations of this metal in mosses and lichens. In contrast, mosses and lichens accumulated relatively high amounts of Cd (mean: 0.0033 mg/g, c0 = 0.00043 mg/g) and Pb (mean: 0.0243 mg/g, c0 = 0.0103 mg/g), respectively.

Extreme Monovalent Ion Selectivity Via Capacitive Ion Exchange.

Capacitive deionization (CDI) is an emerging technology applied to brackish water desalination and ion selective separations. A typical CDI cell consists of two microporous carbon electrodes, where ions are stored in charged micropore via electrosorption into electric double layers. For typical feed waters containing mixtures of several cations and anions, some of which are polluting, models are needed to guide cell design for a target separation, given the complex electrosorption dynamics of each species. An emerging application for CDI is brackish water treatment for direct agricultural use, for which it is often important to selectively electrosorb monovalent Na+ cations over divalent Ca2+ and Mg2+ cations. Recently, it was demonstrated that utilizing constant-voltage CDI cell charging with sulfonated cathodes and short charging times enabled monovalent-selective separations. Here, we utilize a one-dimensional transient CDI model for a flow-through electrode CDI cell to elucidate the mechanisms enabling such separations. We report the discovery that an asymmetric CDI cell with a chemically functionalized cathode induces electric charges in the pristine anode at 0 V cell voltage, which has important implications for monovalent cation selectivity. Leveraging our mechanistic understanding, with our model we uncover a novel operational regime we term "capacitive ion exchange", where the concentration of one ion species increases while competing species concentration decreases. This regime enables resin-less exchange of monovalent cations for divalent cations, with chemical-free electrical regeneration.

A Nanomedicine-Enabled Ion-Exchange Strategy for Enhancing Curcumin-Based Rheumatoid Arthritis Therapy.

Curcumin (Cur) has been clinically used for rheumatoid arthritis treatment by the means of reactive oxygen species (ROS) scavenging and immune microenvironment regulation. However, this compound has a poor water solubility and moderate antioxidative activity, favoring no further broadened application. Metal complexes of curcumin such as zinc-curcumin (Zn-Cur) features enhanced water solubilities, while copper-curcumin (Cu-Cur) shows a higher antioxidant activity but lower solubility than Zn-Cur. Based on their inherent biological properties, this work proposes a nanomedicine-based ion-exchange strategy to enhance the efficacy of Cur for rheumatoid arthritis treatment. Copper silicate nanoparticles with hollow mesoporous structure were prepared to load water-soluble Zn-Cur for constructing a composite nanomedicine, which can degrade in acidic microenvironment of arthritic region, releasing Cu2+ and Zn-Cur. Cu2+ then substitute for Zn2+ in Zn-Cur to form Cu-Cur with a significantly enhanced antioxidative effect, capable of efficiently scavenging ROS in M1 macrophages, promoting their transition to an anti-inflammatory M2 phenotype. In addition, the silicate released after nanocarrier degradation and the Zn2+ released after ion exchange reaction synergistically promote the biomineralization of osteoblasts. This work provides a new approach for enhancing the antiarthritic effect of Cur via an ion-exchange strategy.

Effective removal of nitrate in water by continuous-flow electro-dialysis ion exchange membrane bioreactor (CF-EDIMB): Performance optimization and microbial analysis.

The use of nitrogen fertilizer has been causing nitrate pollution in groundwater, and there is an urgent need for efficient approach to remove nitrate from groundwater. In our job, a novel continuous-flow electrodialysis ion exchange membrane bioreactor system (CF-EDIMB) was set up to remove nitrate (NO3-) from water for the first time. Nitrate removal was positively dependent on water chamber HRT and voltage; voltage had significant effect on the water chamber effluent pH; acetate utilization efficiency was closely correlated with acetate dosage. The optimal conditions forecasted through response surface method (RSM) were given as follows: water chamber HRT was 20 h, biological chamber HRT was 24 h, voltage was 6.65 V and acetate dosage was 454.99 mg/L, dedicating to nitrate removal of 81.90% (83.70% in prediction), water chamber effluent pH of 7.10 (7.00 in prediction) and acetate utilization efficiency of 92.87% (96.51% in prediction). Meanwhile, microorganisms are crucial for nitrate removal, and the microbial community was not sensitive to the variation of acetate dosage. The microbial analysis results indicated that when CF-EDIMB system was operated for 20 d, the sulfate-reducing bacteria Sediminibacterium appeared in the biological chamber, and the effluent sulfate concentration of biological chamber was decreased. During the whole operation, Thauera was the dominant genus. Denitrifying functional genes nirS presented a better expression than the gene narG, and there was no accumulation of nitrite.

A multifunctional electrochemiluminescence and photoelectrochemical biosensor based on a quantum dot ion-exchange reaction for two-channel detection of thrombin.

Herein, a multifunctional electrochemiluminescence (ECL) and photoelectrochemical (PEC) biosensor based on exchange of Ag+ with CdTe QDs was developed for dual-mode detection of thrombin. First, CdTe QDs assembled on an electrode displayed superior ECL and PEC signals. At the same time, C-rich hairpin (HP) DNA linked to silicon spheres loaded a large amount of Ag+, and the specific binding of thrombin to an aptamer led to the release of DNA P; then, DNA P interacted with HP DNA to produce numerous Ag+ ions by an enzyme-digestion amplification reaction. Ag+ underwent ion exchange with CdTe QDs to generate AgTe/CdTe QDs, resulting in much reversed PEC and changed ECL signals for dual-mode detection of thrombin. This work takes advantage of outstanding multi-signals of QDs coupled with convenient ion exchange to achieve multi-mode detection of the target, avoiding false positive or false negative signals generated in the traditional detection process, and thus can be used for the rapid detection of various biomolecules in actual samples.

Green process for isolation and purification of poly(ß-L-malic acid) from Aureobasidium spp. by an integrated ion exchange and membrane separation.

Poly (ß-L-malic acid) (PMLA) is a biopolymer used in food and medical fields. However, the industrial processes are susceptible to the pollution of CaSO4 waste and organic solvent owing to the heavy use of CaCO3 in fermentation process and organic solvents in isolation process. This study developed an organic solvent and CaSO4 -free process for the industrial-scale production of PMLA. Firstly, calcium ion was removed at pH 9.2 by pH adjustment with Na2CO3, and the generated CaCO3 was reused in the fermentation process. Then, the D296 resin was selected to isolate the PMLA from the Ca2+-free broth, where the adsorption data were both primely described by the Freundlich and Langmuir equation, while Freundlich model better fit the process than Langmuir equation, indicating that it was non-monolayer adsorption of PMLA on the resin. Meanwhile, a three-step gradient elution with phosphate buffer (i.e., 0.2 mol/L, pH 7.0) containing 0.1, 0.2 and 1 mol/L NaCl was developed to recover PMLA. Finally, a PES15 membrane was selected to recover the PMLA from the elution solution, which could be reused in the next cycle. As a result, the PMLA with a purity of 98.89 % was obtained with the developed green process. In the developed process, it removed the pollution of organic solvent and calcium waste for the biosynthesis of PMLA on an industrial scale, which also offers a sustainable and green route for the biosynthesis of other carboxylic acids.

N-N(+) Bond-Forming Intramolecular Cyclization of O-Tosyloxy ß-Aminopropioamidoximes and Ion Exchange Reaction for the Synthesis of 2-Aminospiropyrazolilammonium Chlorides and Hexafluorophosphates.

Our research area is related to the spiropyrazolinium-containingcompounds, which are insufficiently studied compared with pyrazoline-containing compounds. Nitrogen-containing azoniaspiromolecules have also been well studied. In drug design and other areas, they are a priori important structures, since rigid spirocyclic scaffolds with the reduced conformational entropy are able to organize a closely spaced area. Azoniaspirostructures are currently of wide practical interest as ionic liquids, current sources (membranes), structure-directing agents in organocatalysis, and in the synthesis of ordered ceramics. Our goal was the synthesis of 2-aminospiropyrazolilammonium chlorides and hexafluorophosphates. Our methodology is based on the tosylation of ß-aminopropioamidoximes with six-membered N-heterocycles (piperidine, morpholine, thiomorpholine, and phenylpiperazine) at the ß-position. 2-Aminospiropyrazolilammonium chlorides and hexafluorophosphates were obtained by the reaction of double ion substitution in the reaction of toluenesulfonates of 2-aminospiropyrazolinium compounds with an ethereal solution of HCl in ethanol and with ammonium hexafluorophosphate in ethanol in quantitative yields of 55-97%. The physicochemical characteristics of the synthesized compounds and their IR and NMR spectra are presented. The obtained salts were additionally characterized by the single-crystal XRD analysis. The presence of both axial and equatorial conformations of spirocations in solids was confirmed. 2-Aminospiropyrazolilammonium chlorides and hexafluorophosphates have weak in vitro antimicrobial activity on Gram-positive and Gram-negative bacterial lines.