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- Nanofiltration and reverse osmosis as a platform for production of natural botanic extracts: the case study of carob by-productsPublication . Almanasrah, Mohammad; Brazinha, Carla; Kallioinen, Mari; Duarte, Luís C.; Roseiro, Luisa B.; Lukasik, Rafal M.; Carvalheiro, Florbela; Manttari, Mika; Crespo, JoãoCarob kibbles are a low-cost and renewable source of economically relevant phenolic compounds (high value catechin and its derivatives and gallic acid) and abundant in small sugars. This work aims at producing two distinct natural extracts from carob kibbles, one extract enriched in catechin and its derivatives for the nutraceuticals market and an extract enriched in sugars for the food industry. This valorisation strategy involves an integrated process based on membrane technology that fulfils the zero discharge principle and may be applied to other agro-industrial by-products. Different aqueous extraction schemes were considered (a one-step process and a two-steps approach). The aqueous extracts obtained were fractionated by diananofiltration and the fractions obtained were evaluated in terms of their content in target products. An integrated scheme for production of fractionated extracts is proposed based on the experimental work developed assuring, simultaneously, a minimal use of resources and emission of waste.
- Study of membrane ageing and grafting mechanisms using electron paramagnetic resonancePublication . Oliveira, Fábio R. P.; Matos, Cristina T.; Moura, José J. G.; Portugal, Carla A. M.; Crespo, JoãoAn important setback for a wider use of membrane processes in industry is fouling, caused by aggregation of biomolecules at membrane surface and pores. Two important approaches to reduce this effect are the use of chemical cleaning procedures and the functionalisation of the membrane surface. However, both processes may lead to membrane degradation and structure alteration due to free radical formation or radical interaction with membrane polymer chains. In this work, electron paramagnetic resonance (EPR) was used to evaluate and quantify radical formation in both chemical cleaning and membrane functionalisation by UV grafting, allowing for a better understanding of free radical formation processes and their influence on membrane characteristics. Studies under different cleaning and grafting conditions, such as, cleaning agent concentration and pH, light intensity and irradiation were also performed showing the potential of EPR as a technique for monitoring both procedures. The information provided by EPR may contribute significantly to the development of new cleaning strategies which minimise the effect of membrane ageing and to the implementation of new and more efficient grafting procedures
- Selective recovery of phenolic compounds and carbohydrates from carob kibbles using water-based extractionPublication . Almanasrah, Mohammad; Roseiro, Luisa B.; Lukasik, Rafal M.; Carvalheiro, Florbela; Brazinha, Carla; Crespo, João; Kallioinen, Mari; Manttari, Mika; Duarte, Luís C.Carob kibbles are an important renewable source of valuable compounds, such as fermentable sugars and phenolic compounds. However, the selective recovery of these compounds is not a trivial task. In this work, a strategy was developed to enable the recovery of both classes of compounds by means of awater-based extraction.One-step extraction recovered only approximately 20% of the phenolic compounds, corresponding to an extraction yield of 0.6 g Gallic acid equivalents (GAE)/100 g dry mass of carob kibbles. The obtained extract contained a significant amount of carbohydrates (110 g/L). The alternative two-step extraction developed enabled higher compound selectivity together with an increase in the yield of the phenolic compounds to about 70%, corresponding to 1.9 gGAE/100 g carob dry matter.The two-step extraction was easily scaled-up and is an effective method to obtain significantly sepa-rated carbohydrates and polyphenol-rich streams that can be further processed, e.g., in biorefineries orfood industries, respectively.
- Production of drinking water using a multi-barrier approach integrating nanofiltration: a pilot scale studyPublication . Lopes, Mafalda T. P.; Matos, Cristina T.; Pereira, Vanessa J.; Benoliel, Maria J.; Valério, Maria Ermelinda; Bucha, Luís B.; Rodrigues, Alexandre; Penetra, Ana I.; Ferreira, Elisabete; Cardoso, Vitor; Reis, Maria A.; Crespo, JoãoA multi-barrier system was studied for the production of drinking water with high chemical and microbiological quality. The integration of nanofiltration (NF) and ultraviolet (UV) photolysis was tested at pilot scale in a surface water treatment plant. The NF membranes tested, Desal DK and NF270, allow for the production of permeates with high quality standards, although the membrane with higher molecular weight cut-off (NF270) revealed to be the best option for surface water treatment due to its higher permeability. The NF270 membrane was also efficient to deliver high quality water, even under high pollutant concentrations, making possible to operate with water recovery rates as high as 98%. Extensive studies were performed in the water treatment plant where the proposed system was tested at three locations of the drinking water production line. Seeking to achieve the best compromise between high recovery rate, high retention of chemicals and microorganisms as well as preventing operational problems (flux decline and fouling), it was found that the integrated system should be placed after the conventional sand filtration, operating at a 91% recovery rate. Under the selected conditions – TMP of 8 bar and recovery rate of 91% – it is possible to operate at constant permeability without flux decline for a period of 15 days, after which a gentle CIP procedure is recommended. Membrane fouling was also investigated and the major foulant classes identified were proteins, polysaccharides and humic acids. A cleaning protocol was also tested and the impact of each cleaning step on the recovery of permeability evaluated.