Ion-exchange basics — An ion-exchange resin is composed of which structural and chemical elements?

Introduction:
Ion-exchange resins are ubiquitous in water treatment and bioseparations. Their performance relies on a solid matrix bearing charged groups and mobile counter-ions that can exchange with ions from the liquid phase. Recognizing all three components is essential to understand capacity and selectivity.

Given Data / Assumptions:

• Typical styrene–divinylbenzene or acrylic-based matrices.
• Functional groups tailored as cationic or anionic exchangers.
• Presence of exchangeable counter-ions (e.g., H+, Na+, Cl−, OH−).

Concept / Approach:
The polymeric network provides mechanical strength and porosity. Functional groups provide the fixed charge sites. Counter-ions balance charge and participate in exchange equilibria with solutes, enabling separations based on charge and affinity.

Step-by-Step Solution:
Confirm the need for a solid backbone to hold charged groups and create pores.Identify the role of fixed ionic groups in binding and exchanging ions.Recognize that counter-ions are essential for electroneutrality and exchange processes.

Verification / Alternative check:
Titration of resins reveals exchange capacity corresponding to functional groups and associated counter-ions; microscopy shows porous polymer matrices supporting transport.

Why Other Options Are Wrong:

• Any single component alone cannot perform ion exchange.
• An inert polymer without charged groups cannot exchange ions.

Common Pitfalls:
Ignoring water content and swelling that affect transport; conflating chelating resins with simple ion exchangers but both still require the triad of matrix, groups, and counter-ions.

Final Answer:
All of these