Question

An exhausted zeolite bed was revived by 250 L of NaCl solution containing `50gL^(-1)` of NaCl solution. How many litres of hard water of hardness 250 ppm can be softened on the zeolite bed?

Answer 1

Correct Answer - `42735 L`
Let `V_(1)` be the volume of hard water and `V_(2)` be the volume of `NaCl` solution containing `x g L^(-1)` used for the regeneration of the zeolite. Then hardness `(H)` is given by:
Hardness `(H)=(50xxxV_(2)xx10^(3))/(58.3xxV_(1)) {:(EW of CaCO_(3)=50),(MW of NaCl=58.5):}`
In the problem , `x=50 g L^(-1), V_(2)=250 L,H=250 p p m`
So, `250 =(50xx50xx250xx10^(3))/(58.5xxV_(1))`
`:. V_(1)=42735 L`