Question

The correct sequence of Extraction of Lanthanoids from monazite sand is: (A) Treat with cold water, (B) Dilute and adjust pH in alkaline range, (C) Digest with Conc. $H_{2}SO_{4}$ at $200^{\circ}C$, (D) Separation by ion Exchange method, (E) Add $Na_{2}SO_{4}$}

• A. C $\rightarrow$ B $\rightarrow$ A $\rightarrow$ E $\rightarrow$ D
• B. A $\rightarrow$ B $\rightarrow$ C $\rightarrow$ D $\rightarrow$ E
• C. A $\rightarrow$ B $\rightarrow$ C $\rightarrow$ E $\rightarrow$ D
• D. C $\rightarrow$ A $\rightarrow$ B $\rightarrow$ E $\rightarrow$ D

Hint:

Acid digestion always comes first to break the mineral lattice; Ion Exchange is the sophisticated final step for separation.

Answer 1

The Correct Option is D

Step 1: Concept The extraction of Lanthanoids from monazite sand (orthophosphate mineral) involves breaking down the mineral and then separating individual elements.

Step 2: Meaning The process starts with acid digestion to convert phosphates into soluble sulfates.

Step 3: Analysis Digestion with Conc. $H_{2}SO_{4}$ (C) is the first step. This is followed by treatment with cold water (A) to dissolve the sulfates. pH adjustment (B) helps remove impurities like Thorium. Adding $Na_{2}SO_{4}$ (E) precipitates Lanthanoid double sulfates. Finally, individual elements are separated using ion exchange (D).

Step 4: Conclusion The correct sequence is C $\rightarrow$ A $\rightarrow$ B $\rightarrow$ E $\rightarrow$ D. Final Answer: (D)