Continuous monitoring for cyanide in waste water with a galvanic hydrogen cyanide sensor using a purge system

A continuous monitoring system for cyanide with a galvanic hydrogen cyanide sensor and an aeration pump for purging was developed. Hydrogen cyanide ev olved from cyanide solution using a purging pump was measured with the hydr ogen cyanide sensor. The system showed good performance in terms of stabili ty and selectivity. A linear calibration curve was obtained in the concentr ating range from 0 to 15 mg dm(3) of cyanide ion with a slope of -0.24 mu A mg(-1) dm(-3). The lower detection limit was 0.1 mg dm(-3). The 90% respon se time of the sensor system was within 3.5 min for a 0.5 mg dm(-3) cyanide solution, when the flow rate of the purging air was 1 dm(3) min(-1). The s ystem maintained the initial performance for 6 months in the field test. Th e developed galvanic sensor system was not subject to interference from sul fide and residual chlorine, compared with a potentiometric sensor system de veloped previously. The analytical results obtained by the present system w ere in good agreement with those obtained by the pyridine pyrazolone method . The correlation factor and regression line between both methods were 0.97 9 and Y = 2.30 x 10(-4) + 1.12X, respectively. This system was successfully applied for a continuous monitoring of cyanide ion in waste water. (C) 199 9 Elsevier Science B.V. All rights reserved.