Nowadays, the main challenge in designing ultrafiltration membranes is increasing membrane fouling resistance without sacrificing membrane transport properties. Novel method of modification of ultrafiltration membranes using aqueous solutions of commercially available cationic and anionic polyelectrolytes based on acrylamide copolymers is proposed. Polyelectrolytes based on acrylamide copolymers are utilized as flocculants for drinking water treatment. The main idea of this study is that using aqueous solutions of polyelectrolytes as coagulation medium upon membrane preparation via phase inversion technique leads to the modification of the skin layer due to immobilization of the charged macromolecules of polyelectrolytes. Due to the extremely high molecular weight of commercially available flocculants (M ≥ 5-10 106 Da), their introduction to the coagulation bath is expected to change the viscosity of the coagulation medium which results in the changes of the kinetics of the phase inversion process. The influence of the chemical nature of the polyelectrolytes and their concentration in the coagulation bath on the physio-chemical properties, charge, hydrophilic/hydrophobic balance of the skin layer, structure, transport properties and antifouling resistance of the membrane was studied. Modification of polymer membranes via addition of polyelectrolytes to the coagulation bath was found to be an effective approach to increase membrane antifouling stability toward natural organic matter in the process of the filtration of surface water and significantly increase the flux of ultrafiltration membranes (via modification by anionic polyelectrolyte). (Less)
Abstract Proteins are not only important for our daily diet but also one of the most important food ingredients worldwide. Since the 1970ies membrane processes have established themselves as a key unit operation in protein processing, e.g., in the dairy industry. The recent trend of the protein shift moving consumption of animal‐based to plant‐based proteins provides new applications for membrane processes. Thus, in this work, the opportunities to transfer the membrane processing experiences from animal‐based proteins to plant‐based protein products will be the focus.
Abstract Membrane fouling is the major factor limiting the wider applicability of the membrane-based technologies in water treatment and in separation and purification processes of biorefineries, pulp and paper industry, food industry and other sectors. Endeavors to prevent and minimize fouling requires a deep understanding on the fouling mechanisms and their relative effects. In this study, Brunauer-Emmett-Teller (BET) nitrogen adsorption/desorption technique was applied to get an insight into pore-level membrane fouling phenomena occurring in ultrafiltration of wood-based streams. The fouling of commercial polysulfone and polyethersulfone membranes by black liquor, thermomechanical pulping process water and pressurized hot-water extract was investigated with BET analysis, infrared spectroscopy, contact angle analysis and pure water permeability measurements. Particular emphasis was paid to the applicability of BET for membrane fouling characterization. The formation of a fouling layer was detected as an increase in cumulative pore volumes and pore areas in the meso-pores region. Pore blocking was seen as disappearance of meso-pores and micro-pores. The results indicate that the presented approach of using BET analysis combined with IR spectroscopy can provide complementary information revealing both the structure of fouling layer and the chemical nature of foulants.
Bipolar membrane electrodialysis (EDBM) can be applied for the electro-acidification of skim milk (SM) using a water-splitting effect. A new method of acidification of SM gives opportunities and perspectives to the development of alternative and novel products in the dairy industry. In the present study the effect of EDBM temperatures from 5 °C, 10 °C, 15 °C, 20 °C, 25 °C and 30 °C on electro-acidification of SM in terms of the mineral composition of the side streams was assessed. The ion transport during electro-acidification by bipolar membranes (BMs) coupled with cation-exchange membranes (CMs) showed that the proposed EDBM process success decreased the pH of SM to 5.7 which is a relevant target for pH adjustments in the dairy industry. Since the BMs and CMs are suspected to change their properties during the ED process, their properties and characteristics were investigated in detailed, showing is no significant deterioration. Furthermore, performance efficiency coefficients of the EDBM process as mass flux (J), capacity (CF), specific energy consumption (E) and the current efficiency (η) are presented. In conclusion, the designed EDBM process can be used for the electro-acidification of SM with minimum loss of the protein and lactose value of the SM.
Process wastewater from separation and purification processes in the food and biotech industries as well as in biorefineries often contain components that can be recovered as valuable by-products in the context of closed-loop recycling with membrane processes. These effluents have a high proportion of organic components and are particularly complex, which is why they have a high fouling potential and organic membrane fouling occurs more frequently. Membrane fouling is a constant challenge for the application of membrane processes. It often results in a drastic reduction of the membrane filtration capacity and a change of the membrane retention. In addition, membrane life is often reduced by increased membrane cleaning, resulting in increased process costs.The development of effective strategies to minimize membrane fouling is therefore highly desirable. One possibility is process monitoring with conventional fouling monitoring methods, e.g. membrane flow and transmembrane pressure. These conventional methods often only register membrane fouling when it is already advanced and therefore no longer reversible.In contrast, in-situ real-time monitoring methods can provide early warning and additional information on the extent, quality or distribution of the fouling on the membrane surface. These methods are needed to achieve one of the major goals in the development of membrane processes - elimination/minimization of fouling to achieve stable membrane flow and retention. Despite these obvious advantages, the use of real-time monitoring methods is not widespread even in the fouling-prone industries - food and biotech industries and biorefineries. In this presentation different insitu real-time monitoring methods and their theoretical basics are presented. The respective advantages and disadvantages are discussed with a focus on methods that could be used in connection with membrane processes in fouling susceptible industries. (Less)
The colloidal stability of lipid based cubosomes, aqueous dispersion of inverse bicontinuous cubic phase, can be significantly increased by a stabilizer. The most commonly used stabilizers are non-ionic tri-block copolymers, poloxamers, which adsorb at the lipid-water interface and hence sterically stabilize the dispersion. One of the challenges with these synthetic polymers is the effect on the internal structure of the cubosomes and the potential toxicity when these nanoparticles are applied as nanomedicine platforms. The natural polysaccharide, softwood hemicellulose, has been proved to be an excellent stabilizer for oil-in-water emulsions, partially due to the presence of hydrophobic lignin in the extract which to some extent is associated to hemicellulose. Herein, we reported for the first time cubosomes stabilized by two types of softwood hemicelluloses, where one is extracted through thermomechanical pulping (TMP, low lignin content) and the other obtained from sodium-based sulfite liquor (SSL, high lignin content). The effect of the two hemicellulose samples on the colloidal stability and structure of monoolein-based cubosomes have been investigated via DLS, SAXS, AFM and cryo-TEM. The data obtained suggest that both types of the hemicelluloses stabilize monoolein (GMO) based cubosomes in water without significantly affecting their size, morphology and inner structure. SSL-extracted hemicellulose yields the most stable cubosomes, likely due to the higher content of lignin in comparison to TMP-stabilized ones. In addition, the stability of these particles was tested under physiological conditions relevant to possible application as drug carriers.
The pulp and paper industry is among the world most important industrial sectors. At present it focuses on the production of cellulose pulp fibers and electricity but transforming pulp mills into biorefineries can reduce the use of fossil fuel resources. Adjusting the processes and converting lignocellulosic materials into new environmental friendly products will enable the production of biochemicals, biofuels and advanced materials for a future bio-economy. The widely used thermomechanical pulping (TMP) process produces large quantities of process water containing cellulose, lignin, hemicellulose and extractives. An efficient separation of these wood chemicals is crucial for the pulp biorefinery concept. The pressure-driven membrane processes microfiltration (MF) and ultrafiltration (UF) are high potential technologies for the separation task. In this application MF and UF are confronted with membrane fouling resulting in flux reduction and retention alteration which have a major impact on the separation process economy. Using suitable cleaning agents can recover flux and retention leading to a sustainable process. During the separation of hemicellulose from TMP process water, severe membrane fouling occurred due to the presence of polysaccharides and proteins. A typical cleaning protocol in pulp biorefineries often includes the use of strong alkaline solutions at high temperatures resulting in short membrane life cycles. The use of enzymatic cleaning is environmental friendly and requires less harsh conditions. The aim of this work is to demonstrate the feasibility of cleaning membranes fouled by TMP process water with enzymes to recover flux and retention. Furthermore, the impact of different enzymatic cocktails as cleaning agents to enhance the efficiency of the cleaning step is discussed. Effective membrane cleaning is a key for the transformation of pulp mills into biorefineries. Overall, this presentation will show that enzymes are an alternative to common cleaning agents, resulting in longer membrane life cycle and less environmental impact. (Less)
Fouling is a constant challenge in membrane-based technologies. As conventional fouling monitoring and control methods are often based on process performance or product quality, they might reveal fouling so late that it has already damaged the membrane in severe and non-reversible way. Thus, surface sensitive online monitoring techniques capable of providing early warning capacity and information about extent, quality and distribution of foulants accumulated on the surface of the membrane are needed. Despite the evident advantages of different real-time monitoring tools, adaptation of them in fouling-concerned food and biorefining industries has not been widely published. Hence, this study aims to explore views on importance, usability and potential of real-time membrane fouling monitoring techniques in the field of these industries. Interview survey was conducted to identify properties needed in real-time fouling monitoring, to find out how established different techniques are in practice and what kind of challenges have been faced in the implementation of in situ tools. Interviews were chosen to concentrate on industrial practitioners working with membranes and persons involved in sales of analysis instruments. To get and overview of the emerging techniques the future perspective is also discussed based on interviews and recently published literature. (Less)
The pulp and paper industry is one of the most important industrial sectors worldwide. The focus of current pulp mills is on the production of cellulose pulp fibres and electricity. By converting traditional pulp mills into biorefineries they can be a keystone in a future bioeconomy based on renewable resources instead of fossil fuels. In order to achieve this, pulp mills have to close their loops and focus on the optimal utilisation of the lignocellulosic raw material not only for fibres but also for the production of biochemicals, biofuels and other advanced materials.Thermomechanical pulping (TMP) is one of most widely used pulping processes. However, its current concept results in large quantities of process water containing very diluted lignocellulosic components such as cellulose, lignin, hemicellulose and extractives and are today send for biological wastewater treatment. An efficient separation and concentration of these wood chemicals could be fundamental in utilising the TMP process in future pulp mill biorefineries. The pressure-driven membrane processes microfiltration (MF) and ultrafiltration (UF) have been identified as high potential processes for the separation and concentration of lignocellulosic components. During the separation process, MF and UF are experiencing membrane fouling resulting in flux reduction and changes in membrane retention, which have both a negative impact on the process economy. However, flux and retention can be recovered by regular cleaning but improved cleaning protocols and new cleaning agents are required to obtain a sustainable process.Therefore, this study focus on the cleaning of polymeric membranes used for the separation of hemicellulose from TMP process water which are severely fouled due to the presence of polysaccharides and proteins. Typical conventional cleaning protocols for such fouling include generally the use of strong alkaline solutions with added detergents at high temperatures resulting in a reduced membrane life cycles, Anton et al. (2015). Alternatively, enzymatic membrane cleaning protocols could be adopted which are more sustainable since they have a lower environmental impact and require less harsh conditions with regard to temperature and pH. Thus, the aim of this work is to compare different conventional and enzymatic cleaning protocols with regard to flux and retention recovery of the membranes fouled by TMP process water.This work will show that on the one hand polysaccharide degrading enzymes can help to enhance the cleaning of membranes fouled with TMP process water and thus resulting in a longer membrane life cycle and less environmental impact, but on the other hand it will also reveal that there is still further development of cleaning agents and protocols required to obtain a complete environmental friendly replacement for current cleaning agents and protocols. Overall, this study will highlight that effective and sustainable membrane cleaning is a key for the true transformation of pulp mills into biorefineries. (Less)
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