Characterisation and prediction of membrane separation performance: An industrial assessment.

The main objective of this work was to develop the existing predictive models for membrane nanofiltration, previously verified at the laboratory scale, and apply these theoretical descriptions to separations of real industrial importance. A detailed comparison was made between the updated Donnan steric partitioning model (UDSPM) model and the simplified linear UDSPM model and the extent of deviation over a wide range of possible nanofiltration conditions was small. This result justified the use of the simplified model for predicting multi-component separations reducing computational time and complexity. A theoretical and experimental comparison was made between two existing continuum descriptions of dielectric exclusion phenomenon. The two models were found to calculate the total contribution of dielectric exclusion effects to the same order of magnitude. The Born model was suggested as the most practical description at present because of the model's inherent simplicity. The UDSPM and linear UDSPM were then employed as a predictive tool in the isolation of N-acetyl-D-neuraminic acid, an important precursor in the production of the influenza antiviral RelenzaTM. The NanomaxTM-50 commercially available NF membrane was characterised and a membrane charge isotherm was developed from a study of the diafiltration components. Excellent agreement between the experimental findings and the model predictions was observed when the membrane charge was varied with pyruvate ion concentration. The linear UDSPM model was then used to assess the performance of a possible full scale industrial process for the recovery of sodium cefuroxime from a process effluent. The model results indicate that inclusion of nanofiltration technology will indeed facilitate the recovery of the high value antibiotic and produce an effluent of significantly improved quality. Overall, as a result of the rational approach taken in this study, the application of existing predictive nanofiltration models for the design, optimisation and scale-up of more complex industrially relevant separations has been established. This will further promote the use of membrane technology in the process industries, such as pharmaceutical and fine chemical manufacture, by significantly reducing development risk and time

Sustainable nutrient recovery from animal manure: A review of current best practice technology and the potential for freeze concentration

Current trends of livestock expansion and associated mass production of manure bring a net import of nutrients that have led to a significant excess in many areas. The implementation of an efficient and more economical technology solution to recover and re-use nutrients from raw or digested wastes is essential and will reduce the need for fossil-fuel based fertilizers. From a waste management standpoint, the identification of nutrient recovery technologies is considered one of the main challenges within a circular economy context. Several traditional techniques exist for manure treatment such as, gasification, thermochemical conversion, composting, hydrothermal carbonization, and liquefaction. However, these technologies face many challenges related to energy consumption and recovered nutrient quality. In this context, freeze concentration (FC) is an emerging technique that can be applied to recover water and concentrate nutrients from waste liquid effluents. This technology brings advantages such as high concentration factor and low energy usage. However, freeze concentration technology is only semi-industrialised and for most applications remains at the development stage. Many studies have been conducted to design and develop processes and applications that target the improvement of both productivity and efficiency, which makes freeze concentration an attractive research subject to the scientific community. Combination of freeze concentration technology with another technology, such as membranes, to generate a more efficient hybrid process must also be considered. This approach of resource recovery from animal manure would ultimately create a more sustainable and circular economy. This paper evaluates the current state-of-the-art and processing strategies related to the treatment of livestock waste materials and contains an up-to-date and critical review on nutrient-rich effluent valorization technologies; focusing on the latest technological progress to recover nutrients from animal manure and introduces the potential that freeze concentration offers, which has only been marginally explored to date. This work makes a comparative analysis of the different processes in terms of their efficiency, cost, energy consumption, operational management, and the results obtained from both bench and large-scale experiments; making it possible to determine the current best practice procedures for the treatment of animal manure

Characterisation of Mass Transfer in Frontal Nanofiltration Equipment and Development of a Simple Correlation

This aim of this work was to investigate the effects of mass transfer in three commercially available frontal nanofiltration systems (Amicon, Sterlitech and Membranology) using the rejection of uncharged poly ethylene glycol (molecular weight 3400) at different pressures and stirrer speeds using a 4000 MWCO membrane. The real rejection was calculated from the observed rejection using the infinite rejection method and a comparison was made between experimentally obtained mass transfer coefficients and those obtained from commonly used ultrafiltration theory. A new mass transfer correlation was proposed that is more appropriate to account for the increased mass transfer effects observed with the larger pressures of nanofiltration. This new correlation is defined as NSh = j(NRe)n (NSc)0.33(1+(Jv/wr)x) is only a minor modification to existing theory and has an accuracy suitable for engineering design purposes

Review of the dielectric properties of nanofiltration membranes and verification of the single oriented layer approximation

The structuring of water at soft solid surfaces remains an area of great interest to colloid science as a whole and has many applications in relation to colloid stability, foams, and wetting films as well as being central to membrane separations. Quantitatively calculating the structural components of thin layers of water and the interaction forces of hydrated molecules with the surface of pores through a layer of water having modified structure is one of the most important challenges in the physics of surface phenomenon. In this paper these effects are reviewed and discussed in relation to the confines of a capillary pore. Membrane nanofiltration is extremely complex and is dependent on the micro-hydrodynamics and interfacial events occurring at the membrane surface and within the membrane nanopores. There is significant debate as to the exact nature of these complex phenomena and rejection is typically attributed to a combination of steric and electrical effects. The electrical effects are less well understood and in particular the contribution of dielectric exclusion. A review of the two competing descriptions of dielectric exclusion is presented along with the theories currently used in modelling this phenomena. A series of rejection experiments of 0.01 M salt solutions at the membrane isoelectric point has been performed for the NF270 and NF99HF membranes. The dielectric constants inside the nanopore are calculated and these values were consistent for three of the salts studied, indicating that a simplistic model based on Born theory is accurate enough for engineering calculations and that ion solvation is most likely to be the more appropriate dielectric exclusion mechanism for true nanofiltration membranes.Peer ReviewedPostprint (published version

Review of the dielectric properties of nanofiltration membranes and verification of the single oriented layer approximation

The structuring of water at soft solid surfaces remains an area of great interest to colloid science as a whole and has many applications in relation to colloid stability, foams, and wetting films as well as being central to membrane separations. Quantitatively calculating the structural components of thin layers of water and the interaction forces of hydrated molecules with the surface of pores through a layer of water having modified structure is one of the most important challenges in the physics of surface phenomenon. In this paper these effects are reviewed and discussed in relation to the confines of a capillary pore. Membrane nanofiltration is extremely complex and is dependent on the micro-hydrodynamics and interfacial events occurring at the membrane surface and within the membrane nanopores. There is significant debate as to the exact nature of these complex phenomena and rejection is typically attributed to a combination of steric and electrical effects. The electrical effects are less well understood and in particular the contribution of dielectric exclusion. A review of the two competing descriptions of dielectric exclusion is presented along with the theories currently used in modelling this phenomena. A series of rejection experiments of 0.01 M salt solutions at the membrane isoelectric point has been performed for the NF270 and NF99HF membranes. The dielectric constants inside the nanopore are calculated and these values were consistent for three of the salts studied, indicating that a simplistic model based on Born theory is accurate enough for engineering calculations and that ion solvation is most likely to be the more appropriate dielectric exclusion mechanism for true nanofiltration membranes.Peer Reviewe

Investigation of the dielectric properties of nanofiltration membranes

There is significant debate as to the exact nature of the separating mechanisms of nanofiltration membranes, particularly dielectric exclusion. This paper reports the findings from an international collaboration to investigate this phenomenon and proposes that a simplistic description based on the Born theory of ion solvation is remarkably accurate. The work illustrates that simplistic descriptions of nanofiltration can have impact in the ab initio design, optimisation and scale up of industrial separation processes. A review comment stated ‘the scientific approach adopted in this study is rigorous and highlights the very important role of modelling nanofiltration processes’

Investigation of the dielectric properties of nanofiltration membranes

Membrane nanofiltration is extremely complex and is dependent on the micro-hydrodynamics and interfacial events occurring at the membrane surface and within the membrane nanopores. There is significant debate as to the exact nature of these complex phenomena and rejection is typically attributed to a combination of steric and electrical effects. The electrical effects are less well understood and in particular the contribution of dielectric exclusion. There is a real need to determine a suitable description for dielectric exclusion for use in membrane modelling for the ab initio design and development of new membrane separation processes and for the scale up and optimisation of existing processes. In this paper the currently accepted separation mechanisms of membrane nanofiltration are explored in order to justify the use of porous models. Furthermore, the Desal-5-DK membrane is characterised by performing a series of rejection experiments of 0.01 M salt solutions at the membrane isoelectric point. This has the advantage of effectively neutralising the membrane fixed charge and facilitating an independent study of the dielectric partitioning at the membrane surface. A simplistic model based on Born theory was tested and found to be remarkably accurate, indicating that ion solvation may be the appropriate dielectric exclusion mechanism for true nanofiltration membranesPeer Reviewe