A combination of ion exchange and electrochemical reduction for nitrate removal from drinking water. Part I: nitrate removal using a selective anion exchanger in the bicarbonate form with reuse of the regenerant solution.
The process of selective nitrate removal from drinking water by means of ion exchange was studied. A commercial strong base anion exchanger with triethylammonium (-N+Et3) functional groups was used in the bicarbonate (HCO3-) and carbonate (CO3(2-)) form. The aim of this study was to optimize ion-exchanger regeneration in view of the subsequent electrochemical reduction of nitrates in the spent regenerant solution. The effects of ion-exchanger form, concentration of regenerant solution, and presence of nitrates, chlorides, and sulphates in the regenerant solution were studied. The strong base anion exchanger in HCO3- form that was investigated was able to treat 270 bed volumes of model water solution containing 124 mg dm(-3) nitrates. To achieve adequate regeneration of the saturated anion exchanger, it is necessary to use approximately 30 bed volumes of fresh 1-M sodium bicarbonate (NaHCO3) regenerant solution. The presence of residual 50-mg dm(-3) nitrates in the regenerant solution, treated by electrolysis, resulted in an increase in the dose of regenerant solution to 35 bed volumes and a decrease in the subsequent sorption run of approximately 13%. The volume of applied regenerant solution was high, but the consumption of NaHCO3 for regeneration was low.
Jelínek
Ludek
L
Department of Power Engineering, Institute of Chemical Technology, Prague, Czech Republic.
Parschová
Helena
H
Matejka
Zdenek
Z
Paidar
Martin
M
Bouzek
Karel
K
D000838:Anions / Q000032:analysis; D001639:Bicarbonates / Q000737:chemistry; D002852:Chromatography, Ion Exchange; D003300:Copper / Q000032:analysis; D004563:Electrochemistry; D007474:Ion Exchange; D009566:Nitrates / Q000737:chemistry*; D010084:Oxidation-Reduction; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D013054:Spectrophotometry, Atomic; D018508:Water Purification / Q000295:instrumentation / Q000379:methods*
D000838:Anions; D001639:Bicarbonates; D009566:Nitrates; D000644:Quaternary Ammonium Compounds; C066585:triethylammonium cation; D003300:Copper