A stochastic model for residence time and contact time distributions of the gas in multistage fluidised beds

Desalination of seawater is an alternative solution in arid zones to provide potable water. In south Morocco, the National Office of Electricity and Water (ONEE) has built many desalination factories. However, the osmosis water (permeate) is unbalanced and has a corrosive character. Therefore, a post-treatment of remineralization is necessary to return to water its calcio-carbonic equilibrium and to protect the distribution pipelines from corrosion degradation. Following the performance on limestone bed remineralization in Daoura plant in comparison with other methods, this article evaluates this technique, by checking the effect of parameters on water quality on the laboratory scale using a calcite bed pilot. We tested E.B.C.T (Empty Bed Contact Time), the upward speed, the bed length, the effect of water debit and the residence time on the treated water quality. Monitoring these parameters on the laboratory scale is indeed essential for optimal remineralization process. With the results of this study as well as economic consideration, it is possible to optimize the choice of the conditions needed for remineralization operation through limestone bed to minimize its costs with sizing and extrapolating to the industrial scale.

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Interfacial Biocatalytic Performance of Nanofiber-Supported β-Galactosidase for Production of Galacto-Oligosaccharides

Catalysts ◽

10.3390/catal10010081 ◽

2020 ◽

Vol 10 (1) ◽

pp. 81

Author(s):

Mailin Misson ◽

Bo Jin ◽

Sheng Dai ◽

Hu Zhang

Keyword(s):

Residence Time ◽

Contact Time ◽

Fluorescence Analysis ◽

Catalytic Performance ◽

Enzymatic Reactions ◽

Chemically Modified ◽

Structural Conformation ◽

Lactose Concentration ◽

Lactose Conversion ◽

Scanning Electron

Molecular distribution, structural conformation and catalytic activity at the interface between enzyme and its immobilising support are vital in the enzymatic reactions for producing bioproducts. In this study, a nanobiocatalyst assembly, β-galactosidase immobilized on chemically modified electrospun polystyrene nanofibers (PSNF), was synthesized for converting lactose into galacto-oligosaccharides (GOS). Characterization results using scanning electron microscopy (SEM) and fluorescence analysis of fluorescein isothiocyanat (FITC) labelled β-galactosidase revealed homogenous enzyme immobilization, thin layer structural conformation and biochemical functionalities of the nanobiocatalyst assembly. The β-galactosidase/PSNF assembly displayed enhanced enzyme catalytic performance at a residence time of around 1 min in a disc-stacked column reactor. A GOS yield of 41% and a lactose conversion of 88% was achieved at the initial lactose concentration of 300 g/L at this residence time. This system provided a controllable contact time of products and substrates on the nanofiber surface and could be used for products which are sensitive to the duration of nanobiocatalysis.

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