Question

Name the membrane system which does function of simultaneous concentration and demineralization

• A. Microfiltration
• B. Ultrafiltration
• C. Reverse osmosis
• D. Nanofiltration

Hint:

Membrane Functions in Dairy:
NANOFILTRATION (NF) = SIMULTANEOUS CONCENTRATION AND DEMINERALIZATION (Retains lactose, permeates NaCl).
Ultrafiltration = Protein concentration.
Reverse Osmosis = Pure water removal.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Nanofiltration membrane separation selectivity: Nanofiltration (NF, 'Loose RO', MWCO 200--1,000 Da) rejects multivalent ions, sugars, and organic solutes ($> 95\%$) while permeating monovalent mineral salts (NaCl, KCl), enabling simultaneous partial demineralization and concentration of whey.
Key Formula or Approach:
\[ \text{Nanofiltration (NF) Permeation: } \underbrace{\text{Monovalent Salts (Na}^+, \text{Cl}^-, \text{K}^+) + \text{Water}}_{\text{Permeate (Demineralization)}} \quad \longleftrightarrow \quad \underbrace{\text{Lactose} + \text{Proteins} + \text{Multivalent Minerals}}_{\text{Retentate (Concentration)}} \]

Step 2: Detailed Explanation:
In dairy membrane processing and whey valorization technology:
- Nanofiltration (NF) (D) (often termed 'Loose Reverse Osmosis' or 'Demineralizing Concentration'):
1. Operates at pore dimensions of $1 - 2\text{ nm}$ with a Molecular Weight Cut-Off (MWCO) of 200 to 1,000 Daltons.
2. It exhibits high rejection ($> 98\%$) for neutral organic molecules like Lactose and peptides, concentrating total solids from $6\%$ to $20 - 22\%$.
3. Simultaneously, it allows monovalent inorganic salt ions ($\text{Na}^+, \text{K}^+, \text{Cl}^-$) and lactic acid to freely pass through into the permeate, achieving a $35\% - 45\%$ partial demineralization of sweet or acid whey without requiring expensive electrodialysis or chemical ion exchange.

Step 3: Final Answer:
Therefore, the membrane system is Nanofiltration, corresponding to option (D).