Assessment of sulfuric acid as pH control agent in catalytic nitrate reduction in drinking waters

Abstract

H2SO4 was thoroughly assessed as an alternative to CO2 as pH controller, as it allows for to a much precise dosage control. Catalytic nitrate reduction tests using a Pd-Cu catalyst supported on a carbon black were performed using both Milli-Q grade and real natural drinking waters spiked with NO3– in batch reactors. Conversion and selectivity results were equivalent to those obtained for CO2 use, obtaining total NO3– conversion and final NH4+ selectivity around 30 % for a pH range of 5.5–6 using a 0.05 M H2SO4 solution. Good stability of the catalyst in natural drinking water with the higher salt content studied was observed through reaction cycles, despite the presence of SO42- in the reaction medium, with total NO3– conversion after four reaction cycles and final NH4+ concentration of less than 16 mg/L were obtained, making H2SO4 a promising alternative to CO2 as pH controller in the catalytic NO3– reduction.