水中氯化物的来源及处理
Source
Chloride (Cl-1) is one of the major anions found in water and are
generally combined with calcium, magnesium, or sodium. Since almost all chloride
salts are highly soluble in water, the chloride content ranges from 10 to 100
mg/I. Sea water contains over 30,000 mg/i as NaC1. Chloride is associated with
the corrosion of piping because of the compounds formed with it; for example,
magnesium chloride can generate hydrochloric acid when heated. Corrosion rates
and the iron dissolved into the water from piping increases as the sodium
chloride content of the water is increased. The chloride ion is instrumental in
breaking down passivating films that protect ferrous metals and alloys from
corrosion, and is one of the main causes for the pitting corrosion of stainless
steel. The SMCL (suggested maximum contaminant level) for chloride is 250 mg/i
which is due strictly to the objectionable salty taste produced in drinking
water.
Treatment
Reverse Osmosis will remove 90 - 95% of the chlorides because of its salt
rejection capabilities. Electrodialysis and distillation are two more processes
that can be used to reduce the chloride content of water. Strong base anion
exchanger which is the later portion of a two-column deionizer does an excellent
job at removing chlorides for industrial applications.
