Modeling and experimental validation of forward osmosis process: Parameters selection, permeate flux prediction, and process optimization

Currently, understanding the dynamics of the interaction between the agents in a process is one of the most important factors regarding its operation and design. Membrane processes for industrial wastewater management are not strangers to this topic. One such example is the concentration of compounds with high added value, such as the phenolic compounds present in olive mill wastewater (OMW). This process is a viable option, thanks to the forward osmosis (FO) process, osmotically driven by a saline stream. In this context, the transport of the solute and the solvent through the FO membranes, although essential to the process, remains problematic. This paper presents a study to predict, by means of a theoretical model, the water flux for two membranes (a cellulose triacetate flat sheet and a polyamide hollow fiber with integrated aquaporin proteins) with different characteristics using a sodium chloride solution as the draw solution (DS). The novelty of this model is the consideration of the contribution of organic compounds (in addition to the inorganic salts) to the osmotic pressure in the feed side. Moreover, the geometry of the modules and the characteristics of the membranes were also considered. The model was developed with the ability to run under different conditions, with or without tyrosol (the compound chosen as representative of OMW phenolic compounds) in the feed solution (FS), and was fitted and evaluated using experimental data. The results presented a variability in the model prediction, which was a function of both the membrane used and the FS and DS, with a greater influence of tyrosol observed on the permeate flux in the flat cellulose triacetate membrane.

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Theoretical Model for the Prediction of Water Flux during the Concentration of an Olive Mill Wastewater Model Solution by Means of Forward Osmosis

Cifuentes-Cabezas,

Álvarez-Blanco,

Mendoza-Roca

et al. 2023

“…The molar concentration of the FS bulk stream c FS in Equation ( 9) can now be substituted by Equation ( 8) to obtain Equation (10), which describes the calculation of the external concentration polarization (ECP) on the feed side.…”

Section: Membrane Performance For a Given Locationmentioning

confidence: 99%

“…For the FO simulation, the thermodynamic knowledge of existing solutions and the knowledge of mass transport through the membrane of the FO are necessary. There are two types of principle models, namely, computational fluid dynamics (CFD) [9] and simplified models [10]. The authors selected the simplified model due to its ease of adaptability and extension, as well as its potential for effortless transfer to industrial applications.…”

Section: Introductionmentioning

confidence: 99%

Predicting Water Flux in Forward Osmosis with Unknown Feed Solution Composition: An Empirical Approach Based on Thermodynamical Properties

Greisner¹,

Mauer²,

Rögener

et al. 2023

This study investigated the predictability of forward osmosis (FO) performance with an unknown feed solution composition, which is important in industrial applications where process solutions are concentrated but their composition is unknown. A fit function of the unknown solution’s osmotic pressure was created, correlating it with the recovery rate, limited by solubility. The osmotic concentration was derived and used in the subsequent simulation of the permeate flux in the considered FO membrane. For comparison, magnesium chloride and magnesium sulfate solutions were used since these show a particularly strong deviation from the ideal osmotic pressure according to Van’t Hoff and are, thus, characterized by an osmotic coefficient unequal to 1. The simulation is based on the solution–diffusion model with consideration of external and internal concentration polarization phenomena. Here, a membrane module was subdivided into 25 segments of equal membrane area, and the module performance was solved by a numerical differential. Experiments in a laboratory scale for validation confirmed that the simulation gave satisfactory results. The recovery rate in the experimental run could be described for both solutions with a relative error of less than 5%, while the calculated water flux as a mathematical derivative of the recovery rate showed a bigger deviation.

“…The permeation flux in the forward osmosis process is relatively lower compared to that in the membrane-based separation processes that operate under pressure [ 19 , 20 ]. To achieve an acceptable permeation flux in forward osmosis setups, a better understanding of the parameters affecting the flux is necessary, such as the interactions between the solvent and solute.…”

mentioning

confidence: 99%

Recent Studies of Membranes for Liquids Separation and Water Treatment

Ezazi,

Quazi,

Taheri

2023