A System for Continuous Measurement of Nitrate Ion Concentration in Pickling Waste Water

Abstract

A new system for continuous measurement of nitrate ion concentration in the waste water discharged from the pickling bath for stainless steel sheet has been developed. This system is based on the principle that nitrate ion is spectrophotometrically measured after the coexisting ions are eliminated as hydroxides. The measurement of nitrate ion concentration in the proposed system is performed as follows. The waste water sample from the neutralization bath is continuously filtered by a newly developed device and some hydroxide precipitates such as iron hydroxide are removed. Then the sample is constantly passed through a debubbling device to the flow cell of an ultraviolet monitor and absorbance of the sample is continuously measured at 302nm. Precision and time response of this system were practical. This system was suitable to the continuous measurement of nitrate ion in pickling waste water.