Combination of membrane modules for single transport of catechins is formulated before the commercial application of the recovery process using HF-SLM. LM techniques 30 1.6 Scope of LM for extraction and recovery of catechins 32 1.7 Importance and objective of the research work 33.
APPENDIX-I
APPENDIX-II
CHAPTER-I
Introduction and Literature Review
Introduction
- Liquid membrane
- Mechanism of separation through LM
- Types of transport of solute in LM based separation
- Carrier
- Types of LM
- Solute
- Applications of LM
- LM for general applications
- LM for recovery of bioactive compounds
- Metal complexation of catechin
- Conventional processes of catechins extraction vs. LM techniques
- Scope of LM for extraction and recovery of catechins
- Importance and objective of the research work
To increase the rate of mass transfer or the efficiency of LM separation, a carrier agent is added to the membrane phase. However, the quality of the drugs (ligands) depends on the complementarity of these ligands and corresponding receptors [75, 76].
Sastre, Mass transfer modeling of di(2-ethylhexyl)thiophosphoric acid-enhanced palladium liquid membrane transport, J. Dai, D2EHPA-facilitated non-steady-state transport of iron(III) across an n-decanol-supported liquid membrane, J. Dhahbi, Extraction of phenol from aqueous solutions by supported liquid membranes (SLM) containing tri-n-octyl phosphine oxide (TOPO), J.
Shukla, Hollow fiber supported liquid membrane: A new technique for the separation and recovery of plutonium from aqueous acidic waste, J. Danesi, A simplified model for coupled transport of metal ions through hollow fiber supported liquid membranes, J.
CHAPTER-II
Materials and Methods
- Chemicals and reagents
- Working solutions for “synthetic extract” of catechin
- Preparation of “real extract” from green tea leaves and analysis of catechins
- Analytical instruments
- Identification and quantification of catechins
- Characterization of catechin complex
- Other instruments
- Experimental studies
- Two phase equilibrium distribution of catechin
- Three phase experimental studies with BLM [2, 3]
- Hollow fiber membrane (HFM) module .1 Set-up
- Model calculation
The detail of the procedure for the identification and quantification of catechins from real extract is described in the next section. Individual catechins in the tea leaf extract and each of the standards were analyzed with a Shimadzu LC-. Two different BLM configurations can be set up depending on the density of the membrane phase.
The membrane fluid (ML) is immobilized in the pores of the flat sheet polymeric membrane. 2.5(a), while a single hollow fiber with LM in the pores and flow direction of the currents in Fig.
Nomenclature
CHAPTER-III
Recovery of Catechin through BLM
Theoretical background
The reaction of catechin with TBP can be described by the following reaction: and the equilibrium constant, Kex by:. where, [CatOH]aq, [TBP]org and [CatOH.xTBP]org represent concentration of catechin in aqueous feed phase, concentration of TBP in organic membrane phase and the concentration. The FT-IR analysis results (covering pure catechin, pure TBP and the combination of catechin + TBP) (Fig. 3.4) indicate that there was no additional peak for the combination of catechin + TBP. It is assumed that the interfacial reaction is very fast and therefore the concentrations at the interfaces will be almost equal to the equilibrium concentrations.
The interfacial flux due to the chemical reaction has been neglected, as the chemical reaction is intrinsically very fast, and therefore the concentrations at the interface will be almost equal to the equilibrium concentrations. The total flux can be derived by Fick's first law of diffusion, both of which apply to the feed phase.
Results and discussion
- Two phase equilibrium study
Removal of the solute from the extract phase (membrane phase) is carried out by a stripping agent present in the stripping phase. The optimal concentration in a three-phase study depends on the interfacial area of the inlet membrane and the diffusivity of the solution-carrier complex in the membrane phase. Both extraction and recovery increase with increasing ethanol concentration up to 0.2 M.
At the end of three such cycles, the concentration of catechin in the stripping phase reached 95 mg.L-1 (Fig. 3.17). But one of the important steps in liquid membrane technique is mass transfer (target solvent) by diffusion in the membrane phase.
Summary of the recovery of catechin through BLM
Ethanol has proven to be an excellent stripping agent for the recovery of catechin from the membrane phase. The optimum conditions for the three-phase studies were found to be a pH of 4.0, a carrier concentration in the membrane phase of 0.8 M, an ethanol concentration of 0.2 M in the stripping phase, a stirring speed of 400 rpm, and an initial concentration of of food of 100 mg.L -1. Extraction of 70% and recovery of 44% was achieved in the BLM transport process from the initial catechin concentration of 100 mg.L-1 in the feed phase.
Almost the same concentration of catechin as in the feed phase was recovered in the strip phase by 3 times in the Fed-batch process. 𝐶𝑐𝑎𝑡]𝑡1 catechin concentration at time 𝑡1 [𝐶𝑐𝑎𝑡] 𝑂𝐻]𝑟 Catechin concentration in intake phase [𝐶𝑎𝑡𝑂𝐻]𝑡𝑜𝑡 Total catechin concentration in food.
CHAPTER-IV
Recovery of Catechins through FS-SLM
Results and discussion
- Selection of solvent-carrier-stripping agent combination
- Selection of polymeric support
- Optimization of parameters for efficient transport of catechin .1 Role of ethanol concentration in stripping phase
- Case study: application of FS-SLM for recovery of various catechin from “real extract” of tea leaves
Experiments were performed with variation in ethanol concentration in stripping phase in the FS-SLM setup (with feed phase of pH = 4, initial catechin concentration of 100 mg.L-1 and 1.2 M carrier in membrane phase). Consequently, the optimum concentration of TBP is dependent on the diffusivity of the catechin-TBP complex in the membrane phase. The effect of feed phase pH on extraction and recovery of catechin in three phase studies was investigated in the pH range of 2.0-10.0.
Beyond the catechin concentration of 100 mg.L-1, the flux increases, however with decreasing slope, indicating that the mentioned saturation condition is reached for the higher catechin concentration and the flux increases as a driving force for the transport, i.e. after three runs of catechin concentration in the stripping phase was found to be 88 mg.L-1, which is quite close to the initial catechin concentration (100 mg.L-1) in the feeding phase.
Summary of the FS-SLM based catechins transportation
The optimal conditions for three-phase studies are a pH of the feed solution of 4.0, a TBP concentration in the membrane phase of 1.2 M, an ethanol concentration of 0.4 M in the stripping phase, a stirring speed of 200 rpm and an initial catechin concentration of 100 mg. .L-1. The developed technique is very applicable for the recovery of catechins from real tea leaf extract without any serious problems. The only problem associated with this technique was the adsorption of the colored substances, tannins, to the pore surface of the carrier material.
Diffusion coefficient D1 between membrane phase and feed phase Diffusion coefficient D2 between strip phase and membrane phase. Kozukue, Stability of green tea catechins in commercial tea leaves during storage for 6 months, Journal of Food Science H47-H51.
CHAPTER-V
Recovery of Catechins through HF-SLM
Theoretical background
- Extraction equilibrium
- Measurement of permeability coefficients
- Mass transfer modeling
𝐴 and 𝑉𝑓 are the effective surface area of membrane and volume of the feed stream, respectively. 𝑄𝑓 is the flow rate (m3.s-1) of the feed stream passing through the lumen of the hollow fibers. The design of the HF-SLM module for the transport of catechin centers on a robust mass transfer modeling of the process.
The second resistance is due to the diffusion of catechin-TBP complex through the membrane phase and the third resistance is experienced at strip side boundary layer of the stripping solution. 5.6) where 𝑟𝑙𝑚 is the log mean radius of hollow fibers, 𝑘𝑖 and 𝑘𝑠 are mass transfer coefficients in lumen and shell side respectively, 𝑟𝑖 and 𝑟𝑜 are internal and external radii of the hollow fiber phase [5].
Results and discussion
- Change of transportation of catechin with time
- Influence of catechin concentration on permeation
- Evaluation of mass transfer coefficient and diffusion coefficient
- Recovery of catechins from “real extract" of green tea leaves: A case study
- Cleaning and the reusability of the HFM
- Combination of membrane modules for once-through transportation
Consequently, the permeability of catechin increases with the increase in flow rate of the feed in the lumen up to 32 × 10-6 m3.min.-1. On the other hand, the rate of recovery of the catechin was found to be negligible during the first 5 minutes as the catechin takes time to diffuse through the membrane phase. Where 𝐽, 𝑇, 𝜇 are flow of catechin in the membrane phase, the operating temperature of the process and the viscosity of the membrane phase, respectively.
The effective diffusion coefficient (𝐷𝑒𝑓𝑓) of the catechin-carrier complex in the membrane phase is calculated using Eq. The maximum recovery of catechins in subsequent runs decreases despite cleaning the membrane after each run.
Summary of the recovery of catechins through HFM module
A simple mathematical calculation was made for the recovery of catechins using HF-SLM in the once-through mode. Ghoshal, Transport of bioactive (+) catechin from its aqueous solution using flat plate supported liquid membranes, J. Sastre, Use of a modified membrane carrier system for recovery of gold cyanide from alkaline cyanide media using hollow fiber supported liquid membranes: feasibility studies and mass transfer modeling, J.
Kumar, Hollow fiber supported fluid membrane: a new technique for the separation and recovery of plutonium from aqueous acid waste, J. Pancharoen, Selective separation of lead and mercury ions from synthetic produced water via a hollow fiber supported fluid membrane, World Academy of Science, Engineering and Technology.
CHAPTER-VI
Recovery and Enrichment of Catechins through Iron-complexation using FS-SLM
Experimental procedure
A required amount of electrolyte (NaCl) was dissolved in the aqueous feed phase to increase the interfacial tension and thereby reduce loss of ML from the pores of the fixed membrane. The use of electrolyte (NaCl) in the aqueous phases has been reported in detail in Section 7.2.3 of Chapter-VII [1]. All the transport experiments were performed with carrier (TBP) concentration of 1.2 M and this concentration was optimized in Chapter-IV [1, 2].
Vacuum-dried precipitate of metal-catechin complex was weighed and recovery was estimated from the stoichiometry of iron catechin complexation. The schematic of permeation cell, the model equation for flux of catechin has been described in Chapter-II.
Results and Discussion
- Chemistry of the Fe-catechin complexation
- Stripping phase selection
- Stoichiometry of complexation reaction
- Identification of metal-catechin complex
- Significance of concentration of stripping solution
- Role of pH in metal complexation of catechin
- Significance of initial concentration of feed
- Kinetic behavior of the transportation
- Case study with real extract
Therefore, the lower concentration of catechin in holding the stripping phase indicates the occurrence of the complexation reaction, while the absence of any UV-vis. Precipitation of the metal-catechin complex begins at the value of the solubility product in the stripping solution. Further, the effect of stripping solution pH on catechin transport was studied in the range from 1.2 to 2.96 as the complexation reaction at the strip side interface is pH dependent.
The effect of the initial concentration of catechin in the nutrient solution had to be investigated with varied concentrations of stripping solution. This is due to the complexation reaction and subsequent precipitation that resulted in a higher driving force (concentration gradient) for transport in the stripping phase.
Summary of the Fe-catechin complexation in SLM
The developed technique can be used without serious problems for the recovery of catechin compounds from hot water extracts (60˚C) of tea leaves, except for the adsorption of the colored substances, tannins, on the pore surface of the carrier material. The solution to this problem is an upcoming challenge that will widely open the research perspectives in the field of separation/purification, recovery and the metal complexation of bioactive compounds from various medicinal plants.
CHAPTER-VII
