Please eaxplain a stepbystep method for the purification of

Please eaxplain a step-by-step method for the purification of water that uses PFA fixation?

1- Add deionized water to a flask and heat to 60 degrees.

2- Add PFA with constant stirring( in 1lit of final reaction volume,add 40g of PFA,water 750 ml,250ml of 0.4M buffer)

3-slowly add a few drops of 10N NaOH ,with stirring.

4- Remove from heat and cool to room temperature.

5- Filter with 3 whatman filter paper.

6-Add 0.4M Sodium phosphate buffer

7- Add 100 mls of distilled water.

8- Add 1M HCl to adjust ph 7.4-7

9-Bring to final volume with deionized water.