Water softening in treatment plants In municipal or industrial water treatment, the zeolite (ion exchange) process is primarily used to remove which property of water?

Introduction / Context: Hardness in water, caused mainly by calcium and magnesium ions, interferes with soap action, scales boilers, and reduces heat transfer efficiency. The zeolite process is a classic method for softening water via ion exchange, replacing hardness ions with sodium.

Given Data / Assumptions:

• Zeolite (natural or synthetic) operates as a cation exchanger.
• Feed contains hardness-causing cations Ca²⁺ and Mg²⁺.
• Regeneration is with brine (NaCl solution), restoring exchange capacity.

Concept / Approach: Sodium zeolite exchanges Na⁺ for Ca²⁺/Mg²⁺: hardness ions are captured on the resin, sodium enters the water. The process directly targets hardness rather than acidity, alkalinity, or trace metals removal (though some incidental removal may occur under specific conditions).

Step-by-Step Solution:

Verification / Alternative check: Standard water treatment sequences often include zeolite softening prior to boiler or process use; hardness tests (EDTA titration) confirm efficacy post treatment.

Why Other Options Are Wrong:

Common Pitfalls: Assuming ion exchange removes everything; it is selective and capacity-limited, optimized for hardness ions.

Final Answer: hardness