Liquid-liquid extraction (LLX) using thermo-responsive polymers is a promising low-energy alternative for concentrating hypersaline brines from reverse osmosis (RO). This study presents a comprehensive evaluation of a multistage crosscurrent LLX process, comparing poly(propylene glycol) 400 (PPG 400) and the nonionic surfactant Dehypon (R) LS54. The methodology includes determining liquid-liquid equilibrium (LLE) data, a theoretical graphical multistage countercurrent LLX analysis, four-stage crosscurrent batch experiments, solvent regeneration, and product purification via thermally induced phase separation (TIPS). LLE results revealed that PPG 400 possesses higher water over salt selectivity. Using ternary diagrams from LLE results, it was found that PPG 400 and Dehypon (R) LS54 require four and five theoretical stages, respectively, to increase the NaCl concentration from 7 to 20 wt%. In comparative four-stage crosscurrent experiments, PPG 400 achieved a higher final raffinate NaCl concentration (17.8 wt%) than Dehypon (R) LS54 (13.8 wt%). Using TIPS, for both polymers high recovery (>99.5%) was achieved at 80 wt% to 97 wt% polymer purity. TIPS was also proven to be an effective separation for the raffinate streams, reducing polymer contamination to as low as 0.3 wt% for PPG 400 and 0.04 wt% for Dehypon (R) LS54. The co-extracted salt in the extract yielded a secondary brine stream (1.3 wt% to 10.4 wt% NaCl) rather than clean water, showing that more sophisticated processing and/or downstream purification is necessary to obtain high quality potable water. This work elucidates the fundamental trade-offs between thermodynamic selectivity, solvent loss, and product purity that govern the design of LLX systems for brine concentration and valorization.

An extension of the equilibrium stage model to improve its applicability to reactive distillation is presented. The significant aeration of the liquid holdup on trays leads to the amount of clear liquid present being significantly less than the volume available. Tray hydraulic correlations are incorporated by leveraging the existing inside-out algorithm to rigorously calculate the liquid holdup on distillation trays, turning this parameter into an additional model output and eliminating the need to estimate this parameter beforehand. Application of this extended model shows that the aeration of the liquid holdup cannot be neglected for systems where the reaction kinetics limit the reactive productivity, and leads to column designs where additional reactive trays are needed to provide adequate reactive capacity. The workflow of this model provides a more robust path to obtaining reactive distillation column and tray designs that comply with liquid holdup requirements and tray hydraulic limitations.

Vapor-liquidequilibrium (VLE) data, essentialfor an accurate design of distillation columns, are not always readilyavailable. This work has systematically assessed the feasibility ofdetermining VLE data based on excess molar enthalpy(h ( E )) results. Twelvecubic Equation of State (cEoS) models combined with eight mixing rulesand the Perturbed Chain Statistical Associating Fluid Theory (PC-SAFT)have been assessed. cEoS models are robust and applicable to a significantnumber of solvent families, while the PC-SAFT model is typically appliedfor strongly nonideal systems exhibiting molecular association behavior. VLE predictions based on the Peng-Robinson cEoS withthe 2-parameter Stryjek-Vera-Margules-type mixing rule,one of the best cEoS-mixing rule combinations, was reasonablyaccurate, but less accurate than predictions based on the standardmodified (mod.) UNIFAC (Do) model. This makes the developed h ( E )-cEoS-VLE methodology relevant only for systems whose binaryinteraction parameters in UNIFAC (Do) and VLE dataare not available. For the most nonideal self-associating systemsevaluated, the PC-SAFT model parametrized with experimental h ( E ) data provided isobaric VLE results with similar or even higher accuracy than themod. UNIFAC (Do) model. This indicates the potential of the h ( E )-PC-SAFT-VLE model for accurately predicting VLE data for highly nonideal and associating systems. Therefore, thismethodology can be used as a quick evaluation method for the separationof complex systems, including ionic liquids and deep eutectic solvents,for which the mod. UNIFAC (Do) model does not provide sufficientlyaccurate VLE predictions.

A novel methodology for the techno-economic assessment of Reactive Distillation (RD) is presented. The developed methodology benchmarks reactive distillation (RD) to a conventional reactor + distillation train flowsheet (R+D) on a cost-optimized basis, with the optimization being performed on the process unit level (reactor sizing, number of stages, feed point(s)) and the internals level (reactive tray design). This methodology is applied to the ideal quaternary system A + B <-> C + D with the conventional boiling point order of T-C < T-A < T-B < T-D (alpha(AD) = 4, alpha(BD) = 2, alpha(CD) = 8). From this pool of data, a regime map of RD vs. R+D is established in which the attractive regions of either flowsheet option are identified in terms of the chemical reaction rate and chemical equilibrium. It is found that RD can arise as the cost optimal option for a large range of residence time requirements by virtue of overcoming the external recycle requirements of R+D. This is achieved through optimized reactive tray design. Contrary to conventional distillation design practices, it was found that the preferred use of bubble-cap trays over sieve trays to allow elevated weir heights and designing the column diameter below 80% of flooding become relevant design choices when accommodating high liquid holdup.

For conventional reverse osmosis (RO), the osmotic pressure difference limits the allowable concentration factor for concentrating NaCl solutions. The use of low-salt-rejection RO (LSRRO) membranes could allow much higher concentration factors, provided that these membranes show a sufficient decrease in NaCl retention with increasing NaCl concentration in the retentate. This work quantifies allowable NaCl retentions for LSRRO as function of the retentate concentration for different pressures. For a pressure of 70 bar allowable NaCl retentions start to deviate from retentions reported for commercial RO membranes at NaCl weight fractions below 0.1. NaCl retentions for commercial nanofiltration (NF) membranes are much lower than allowed for LSRRO, leading to high NaCl losses in permeate. The required NaCl retention for LSRRO as function of the NaCl retentate concentration therefore falls in between those reported for commercial RO and NF membranes, implying that LSRRO membrane development is required. Based on the obtained relations required concentration factors for the concentration of purified seawater RO retentate and depleted brine from chlor/alkali production have been determined. The concentration factor for LSRRO for concentrating solutions with a NaCl concentration of either 0.07 kg center dot kg(-1) or 0.18 kg center dot kg(-1) to saturation at 120 bar pressure is 4 - 5 times higher than for a case where full retention would have been allowed. By optimizing the unit lay-out to minimize NaCl loss in permeate, approximately 1.2 m(2)center dot kg(-1)center dot h membrane area per saturated NaCl solution flow produced would be required for concentrating a 0.18 kg center dot kg(-1) NaCl solution to saturation, assuming a permeance of 0.36 kg center dot m(2)center dot h(-1)center dot bar(-1).

Modelling of nanofiltration processes focusses on dilute solutions, whereas industrial nanofiltration applications often feature the use of more concentrated solutions. Recently, nanofiltration models for dilute NaCl solutions were extended to higher concentrations of approximately 1.2 mol center dot L-1. Furthermore, models for the prediction of the NaCl retention for saturated NaCl solutions containing impurities or anti-solvents based on thermodynamic considerations were proposed. However, proper models for intermittent NaCl concentrations were lacking. A new model, extending the earlier NaCl retention model for (near) saturated NaCl solutions, has been developed to fill the existing gap. The key assumption in the model is that the resistance for NaCl transport is a function of the sodium and chloride activities and is independent of the impurity concentration of the solution treated. Based on the experimental results generated in this study and obtained from open literature the validity of this model has been proven for NaCl solutions containing Na2SO4. Experimental NaCl retentions could be predicted by the developed model with sufficient accuracy (within 5 % absolute) over a wide range of NaCl and Na2SO4 concentrations up to saturation. The largest inaccuracies were obtained for nanofiltration of (near) saturated NaCl solutions at very low membrane flux.

In this work, we report the synthesis and characteristics of cyclomatrix polyphosphazene membranes based on interfacial polymerization between 1,1-tris(4-hydroxyphenyl)ethane and hexachlorocyclotriphosphazene on top of alumina or polyacrylonitrile supports. The potential of alumina-supported thin film composite membranes as organic solvent nanofiltration membranes has been confirmed with a polystyrene-based molecular weight cutoff of 347 +/- 120 Da and 503 +/- 220 Da in acetone and toluene, respectively. Also, the resulting alumina-supported TFC membrane showed a methylene blue rejection (Mw = 319 g mol-1) of 98.2 +/- 2.3%, 92 +/- 1.7%, and 93 +/- 0.5% in water, ethanol, and acetone, respectively. Furthermore, a thin film composite membrane has been prepared with a polyacrylonitrile support via interfacial polymerization to validate the preparation technique for polymeric supports and facilitate industrial implementation. The resulting membrane showed higher permeance and lower rejection than the alumina-supported membrane due to the presence of pinholes in the selective layer on top of the polyacrylonitrile supports. Our results clearly show the great potential of cyclomatrix polyphosphazene membranes as organic solvent nanofiltration membranes. However, for polyacrylonitrile-supported membranes, the preparation method needs further investigation.

Increasing sustainability awareness has created opportunities for the recovery and reuse of salt solutions in industrial processes. Osmotically assisted reverse osmosis (OARO) has the potential to concentrate these salt solutions. Until now OARO research focussed on the production of purified water yielding an unsaturated salt solution as retentate, whereas a saturated salt solution is often needed for reuse. OARO featuring recycling of part of the saturated salt solution to the permeate side of the membrane has now been investigated. The introduction of a saturated NaCl solution results in strongly changing osmotic pressure difference and flux profiles along the length of the modules, with a maximum osmotic pressure difference and a minimum flux close to the outlet of the OARO system. In contrast to the NaCl retention of the membrane, the NaCl feed concentration does not have an influence on the maximum osmotic pressure difference. The osmotic pressure difference and membrane flux are strongly dependent on the applied concentrate split factor, which has a strong effect on the required membrane area per feed flow supplied as well. The amount of surface area required per flow of saturated NaCl solution leaving the OARO unit has an optimum as function of the concentrate split factor. This is due to two counteracting effects, the lower osmotic pressure difference, and the lower fraction of saturated NaCl solution leaving the OARO for a higher concentrate split factor. Based on the modelling, essential knowledge has been generated for the further research and development of OARO.

BACKGROUND: Phenol is used as a raw material in the polycarbonate industry and as the incentive for bio-based plastics and products is increasing, so is the interest in and demand for bio-based phenols. In renewable phenol production processes based on biomass, impurities derived from the biomass, including other oxygenate compounds, are expected in the phenol containing solution. Vapor – liquid equilibrium (VLE) of phenol and 2-Octanone was studied and impact of impurities thereon to gain insights applicable for similar systems in biore fi neries for renewable phenol production. RESULTS: For the binary mixture of phenol - 2-octanone azeotropic VLE behavior was found. The effects of ternary compounds on the molecular interactions between phenol and 2-octanone were studied using isothermal calorimetry (ITC) and molecular modelling (MM), and the impact on the VLE behavior was measured using an ebulliometer. CONCLUSION: It was found that the relative volatility could be improved by adding solvents that are polar and/or contain hydrogen bond accepting groups. Ketones and ethers most strongly improved the relative volatility of the binary mixture 2- octanone – phenol. Addition of a linear alkane, a repelling component especially for 2-octanone, strongly improved the relative volatility as well. ITC and MM results, providing heat of mixing and the interaction energy of mixture components, improved fundamental understanding of the molecular interactions between phenol, 2-octanone and ternary compounds, and supported the VLE fi ndings. Supporting information may be found in the online version of this article.

This chapter considers applications of nanofiltration in the chemical Industry, covering inorganic chemicals, organic chemicals, petrochemicals, pharmaceuticals and applications in biotechnology. Examples and case studies are provided of ‘in-process’ separations and of effluent treatment and reuse. It is shown that the unique solute separation capabilities provided by nanofiltration technologies are attractive for many applications in the chemical industries.

We present an easily accessible, open-access approach for fast pre-selection of solvents for extractive distillation at isobaric and isothermal conditions. The method uses the three-component Margules equation, which can predict vapor-liquid equilibria (VLE) in ternary systems with the infinite dilution activity coefficients, gamma i infinity, as sole input parameters. This approach is accessible for anybody regardless of the availability of process simulators or other dedicated software to predict VLE, and can be combined with open access gamma i infinity to perform solvent screening. This approach shows a deviation in VLE of 5% for non-hydrogen bond donating mixtures, while for highly dissimilar (e.g. alkane - alcohol) mixtures the deviation can be 10%. The presented method identifies molecular solvents for case studies where the same or similar solvents have also been reported in literature or are already applied on the industrial level, showing realistic pre-selection outcomes. Furthermore, small, cyclic, polar, molecular solvents are identified to induce preferential interactions and several structurally similar solvents, e.g. ethylene carbonate, dihydrolevoglucosenone and y-valerolactone, are identified to be potential alternative solvents. Among the ionic liquids (ILs) and deep eutectic solvents (DESs), the morpholinium and ammonium structures are identified to have the highest potential for increasing relative volatilities, they also show lower toxicity than other cations. This method thus proves to be able to perform early-stage pre-screening among new classes of solvents which generates information on the minimum required solvent to feed ratio (SFmin) for energy-efficient distillation from gamma i infinity obtained by measurement or from literature.

The mixing sensitivity was studied for the sulfonation of two alkylbenzenes (ArH's), toluene and ethylbenzene, by using a rotor-stator spinning disc reactor (SDR). Fuming sulfuric acid (FSA), containing 30 wt. % free sulfur trioxide, was used as a sulfonating agent, which resulted in a fast, exothermic, and viscous liquid-liquid reaction system. Experiments were conducted by varying the SDRs' rotational speed between 50 and 9000 rpm. In addition, different molar flow ratios (ArH:FSA) were investigated, ranging from 0.8 to 3.2, while operating at a maximum residence time of 7.1 s. The selectivity towards mono-sulfonated products was found to increase significantly at a higher rotational speed. This was observed consistently for both alkylbenzenes and all molar flow ratios, confirming the mixing sensitivity of the two alkylbenzene sulfonation reactions. Furthermore, it was proposed that the mixing sensitivity arises from a competition that exists between the desired and highly reactive primary sulfonation and the much less reactive consecutive sulfonation step to disulfonic acids.

The increasing need for sustainable processes stimulates the production and recovery of renewable organic acids. The purification of these acids is often difficult because of similar acid volatilit...

The infinite dilution activity coefficient, gamma(infinity)(i), is a frequently used molecular descriptor to pre-select a solvent for various kinds of fluid separations. Unfortunately, information related to these coefficients is scattered throughout the open literature. Therefore, an open-source gamma(infinity)(i)-database containing 77.173 gamma(infinity)(i) data points over the temperature interval 243 K < T < 555.6 K for 268 solutes and 692 solvents is provided in the electronic supporting information of this work. Additionally, we performed an inter- and extrapolation data analysis algorithm using the Van 't Hoff equation to extend the gamma(infinity)(i) data points at 298.15 K. The gamma(infinity)(i) for five solutes (n-hexane, benzene, chloroform, acetone and ethanol) in a wide range of molecular solvents and ionic liquids (ILs) were compared. Various trends between the molecular solvent structure and the gamma(infinity)(i) are visualized, which allows for not only a pre-selection of solvents for targeted gamma(infinity)(i) but also visualizes the effect molecular modification of the solvent will have on the gamma(infinity)(i). Overall, the presented methodology is complementary to approaches using simulation software, and helps acquiring a detailed understanding of the effect of the solvent structure on the gamma(infinity)(i), which will facilitate solvent pre-selection in an early process design stage towards greener fluid separations.

Conventional commercially available nanofiltration (NF) membranes show limited stability at extreme pH conditions, whereas commercially available NF membranes that can cope with these conditions often show (too) low permeance or are relatively open. Since NF applications in many industrial sectors require pH stable NF membranes with a range of molecular weight cut-offs (MWCO), including tight NF membranes, substantial research and development efforts are being devoted to the research and development of these membranes. This review discusses these developments as reported in open literature, with a focus on the period between 2016 and 2021. Most developments relate to the use of interfacial polymerization to produce thin film composite membranes. Polyamine and polyurea membranes with good chemical stability for extreme pH conditions have been prepared. For polysulfonamide membranes indications for good chemical stability at low pH have been shown. These membrane types show improved stability compared to developed poly(aryl cyanurate), polyesteramide, poly(amide-sulfonamide), and polyamide membranes, which are more susceptible to hydrolysis and therefore less chemically stable at extreme pH. Furthermore, layer-by-layer coating using strong cation - and anion polyelectrolytes has led to new pH stable NF membranes. Despite the extension of the pH stable NF membrane portfolio, most of the developed membranes still do not meet the performance characteristics of the best commercially available NF membranes applicable for the common pH range between 2 and 11. Only a few layer-by-layer coated polyelectrolyte membranes combine high permeance, relatively low MWCO and stability at extreme pH. However, these membranes are not yet commercially available for full-scale applications requiring high pressure operation. Consequently, there is still room for research and development to further improve pH stable NF membranes.

BACKGROUND: Although phenol is a key intermediate in the plastics and polycarbonate industry, it is also a toxic component that requires removal from dilute aqueous streams, potentially by liquid – liquid extraction (LLX). For LLX, cumene is suggested as a solvent as it is already present in processes in the polycarbonate industry. For the recovery of cumene from phenol by dis- tillation, knowledge on vapor – liquid equilibrium (VLE) behavior is important, in combination with how this is affected by other components possibly present as an impurity or explicitly added as a solvent. This was investigated in this work. RESULTS: The binary cumene – phenol system shows a tangent pinch in the binary VLE diagram. Addition of a range of impurities and solvents showed that hydrogen bond accepting compounds strongly improve the relative volatility of the mixture, whereas dodecane, not capable of forming hydrogen bonds, has a negative effect on the relative volatility. CONCLUSION: Addition of polar components with hydrogen bonding abilities, i.e. ketones or ethers, affected the relative volatility of cumene over phenol the most positively. Combining two types of components results in similar effects, and clear synergistic effects could not be shown based on current VLE measurements. Addition of an apolar component in combination with polar com- ponents with hydrogen abilities had only a minor effect on the relative volatility. Chemical information online

Sustainable processes, often dealing with complex mixtures, would benefit from the availability of more accurate and predictive thermodynamic models. Most existing models are (semi)empirical and require extensive input, while application to complex mixtures is cumbersome. In this work, the potential of extracting information about nonideal behavior directly from spectroscopic information as a sole source is studied. A methodology framework is proposed and 45 binary component mixtures with a broad nonideality range were evaluated. Excess infrared absorbance spectra were successfully correlated with Gibbs excess energy using multivariate data analysis. For most binary mixtures, experimental vapor-liquid equilibrium literature data could be predicted accurately based on a model (UNIQUAC) using thermodynamic parameters obtained from the spectroscopic results. This also applied to binary mixtures that were not involved in the correlating step. Potential benefits of the investigated method are cost-effective, accurate, and quick measurement of nonideality information, and improved predictive models, even for complex mixtures. The principle is demonstrated, and suggestions for further developments are provided.

Transport mechanisms for nanofiltration membranes are usually studied for solutions containing low solute concentrations, whereas practical applications of nanofiltration often use highly concentrated or even saturated solutions. These solutions are amongst others obtained from anti-solvent crystallization processes. This study shows that the NaCl retention for nanofiltration of a solution saturated in NaCl and containing either ionic or neutral anti-solvents can be predicted from thermodynamic considerations. The membrane resistance of nanofiltration membranes during NaCl transport through the membrane for solutions with a high NaCl concentration in the concentrate is negligible. Furthermore, the NaCl retention can be predicted based on simple anti-solvent crystallization experiments, provided that the concentrations of the anti-solvent in the permeate and concentrate are known. The concept has been proven for a range of ionic and neutral anti-solvents and a broad range of nanofiltration membranes.

Corrosion is a major issue in industry, and the oxygen concentration in the fluids processed influences corrosion rates. Membrane contactors, such as Liqui-Cel (R) modules, are suitably used for de-aerating ultrapure water to low oxygen levels. Liquid mass transfer correlations for water de-aeration have been determined by varying liquid flow rates at ambient conditions. Limited information is available on membrane de-aeration of concentrated salt solutions. In our work the feasibility of membrane contactors for de-aeration of salt solutions containing 0.1-25 wt% NaCl has been investigated and confirmed. Oxygen outlet concentrations as low as 70 ppb have been obtained at a temperature of 40 degrees C and a (vacuum) pressure of 70 mbar using the Liqui-Cel (R) 2.5 x 8 Extra-flow module. Mass transfer coefficients have been determined for a range of liquid velocities, viscosities, densities, and oxygen diffusion coefficients by changing the salt concentration and the temperature. This means that not only the Reynolds number has been varied (as commonly done), but the Schmidt number as well. Their effect on the Sherwood number has thus been established. The obtained correlation allows sufficiently accurate prediction of oxygen removal from NaCl solutions over the entire salt concentration range. A membrane area of 455-4105 m(2) (using Liqui-Cel (R) 14 x 40 modules) is required for de-aeration of a saturated sodium chloride solution to an oxygen concentration below 50 ppb using a total liquid flow of 100-900 m(3)/h, which is typical for salt production.