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ION EXCHANGE AND DIALYSIS. THE REMOVAL OF IONS FROM SOLUTION USING RESINS. RESIN PARTICLE AND BEADS. Ion exchange of monovalent cations : (assume y = 1). For most solutions g A = B . Ion exchange of mixed-valent cations : (assume y = 1).
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ION EXCHANGE AND DIALYSIS THE REMOVAL OF IONS FROM SOLUTION USING RESINS
Ion exchange of monovalent cations: (assume y = 1) For most solutions gA = B
Selectivity of Ion Exchange Resins In Order of Decreasing Preference Strong acid cation Strong base anion Barium Iodide Lead Nitrate Calcium Bisulfite Nickel Chloride Cadmium Cyanide Copper Bicarbonate Zinc Hydroxide Magnesium Fluoride Potassium Sulfate Ammonia Sodium Hydrogen
Chelating Cation Resin Selectivities for Metal Metal KM/Caa Hg+2........................... 2,800 Cu+2........................... 2,300 Pb+2........................... 1,200 Ni+2 .......................... 57 Zn+2........................... 17 Cd+2........................... 15 Co+2....... .................... 6.7 Fe+2............................ 4.7 Mn+2............................ 1.2 Ca+2............................ 1 • Selectivity coefficient for the metal over calcium ions at a pH of 4
Cost of Commercially Available Resins • Resin Cost($/ft3) Strong acid cation.......... 45-130 Weak acid cation............ 120-160 Strong base anion........... 210-270 Weak base anion............. 210-260 Chelating cation............ 350-650
SMALL SCALE ION EXCHANGE COLUMNS
POSITIONING OF RESIN BEADS FOR A MIXED BED JUST AFTER BACKWASHING
Improved Nitrate Removal from Drinking Water by Ion Exchange: Testing a Hydraulic Device for Improved Regeneration
America's really big sacred cow is fluoridation of drinking water. Fact: Fluoride is so toxic that only one milligram constitutes a prescription dose. In spite of this, the Environmental Protection Agency (EPA) allows up to this amount in a single glass of drinking water. Fact: Virtually every country in Europe has stopped fluoridation. Research shows that fluoride confers little if any real benefit. Fact: Persons who have grown up with fluoridated water have, on the average, only 1/2 of one filling less per lifetime than people who did not drink fluoridated water (Chemical and Engineering News, May 8, 1989).