Device and method for analyzing total cyanide in water samples

1. A device for analyzing total cyanide in a water sample, comprising: a mixing tube, a stripping tube, a sampling pipe, a reaction pipe, a peristaltic pump, an air pump, a UV digester, a heater, a condenser, a drain pipe and a water sample detector;

wherein the mixing tube, the stripping tube, the sampling pipe and the reaction pipe are respectively connected to the peristaltic pump; the mixing tube is connected to the reaction pipe; a bottom of the stripping tube, the air pump, the UV digester, the heater and the condenser are sequentially connected; the condenser is connected to the mixing tube; an upper portion of the stripping tube, the sampling pipe and the reaction pipe are respectively connected to the drain pipe; and the water sample detector is able to detect and analyze parameters of the water sample in the mixing tube.

2. The device of claim 1 , wherein the reaction pipe and the sampling pipe each comprise a plurality of three-way valves, and respective three-way valves comprise a normally closed end, a common end and a normally open end.

3. The device of claim 2 , wherein the reaction pipe comprises three-way valves Q 0 , Q 1 , Q 2 , Q 3 , Q 4 and Q 5 ;

wherein a normally closed end of Q 0 is connected to a pure water pipe; a common end of Q 0 is connected to a normally closed end of Q 1 ; a common end of Q 1 is connected to a normally open end of Q 3 ; a normally open end of Q 1 is connected to a normally open end of Q 2 ; a normally closed end of Q 2 is connected to the drain pipe; a common end of Q 2 is connected to the mixing tube; normally closed ends of Q 3 , Q 4 and Q 5 are respectively connected to chemical agent tubes R 1 , R 2 and R 3 ; a common end of Q 3 is connected to a normally open end of Q 4 ; a common end of Q 4 is connected to a normally open end of Q 5 ; and a common end of Q 5 is connected to the peristaltic pump.

4. The device of claim 2 , wherein the sampling pipe comprises three-way valves Q 6 , Q 7 , Q 8 , Q 9 and Q 10 ;

wherein normally closed ends of Q 6 , Q 7 , Q 8 , Q 9 and Q 10 are respectively connected to a pure water pipe, a water sample-monitoring tube, a standard sample tube, the drain pipe and a chemical agent tube R 4 ; a normally open end of Q 6 is connected to an air inlet pipe; common ends of Q 6 , Q 7 , Q 8 and Q 9 are respectively connected to normally open ends of Q 7 , Q 8 , Q 9 and Q 10 ; and a common end of Q 10 is connected to the peristaltic pump.

5. The device of claim 1 , wherein the peristaltic pump is provided with two connecting ports, which are respectively connected to common ends of two simultaneously-operated three-way valves QA 1 and QA 2 ; normally open ends of QA 1 and QA 2 are respectively connected to the reaction pipe and the mixing tube; and normally closed ends of QA 1 and QA 2 are respectively connected to the sampling pipe and the stripping tube.

6. The device of claim 1 , wherein the mixing tube is connected to the condenser through three-way valves QB and QC; and the air pump is connected to the bottom of the stripping tube through a three-way valve QD.

7. A method for analyzing total cyanide in a water sample using the device of claim 1 , comprising:

(1) emptying a stripping tube and a mixing tube in a thermostatic water bath; and performing a heating process to obtain a constant temperature inside a heater;

(2) pumping pure water into the mixing tube followed by a standing to obtain an initial absorbance of the water sample;

(3) pumping chemical agents R 1 and R 2 , as well as a small amount of pure water from a reaction pipe to the mixing tube through a peristaltic pump to produce a mixed chemical agent solution; wherein R 1 is a mixed solution of a 18-22 g/L potassium Hydrogen phthalate solution and a 2-4 g/L sodium hydroxide solution, and R 2 is a 3-5 g/L chloramine T solution;

(4) pumping a sample to be detected from a sampling pipe to the stripping tube through the peristaltic pump;

(5) adding a chemical agent R 4 to the stripping tube for catalytic elimination; wherein R 4 is a mixed solution of a 3-5 g/L sodium hydroxide solution with a concentration of and a 18-22 g/L citric acid solution;

(6) pumping the sample to be detected in the stripping tube by an air pump to a UV digester and then to the heater; instantaneously vaporizing the sample to be detected by distillation in the heater to release a cyanide gas; cooling the cyanide gas into a cyanide liquid by a condenser; allowing the cyanide liquid to flow into the mixing tube to react with the mixed chemical agent solution obtained in step (3); and repeating the distillation until the sample to be detected is completely vaporized;

(7) adding a chemical agent R 3 to the mixing tube for color development, wherein R 3 is a mixed solution of pyridine with a volume fraction of 99% or more, barbituric acid with a mass concentration of 28-32 g/L and concentrated hydrochloric acid; subjecting the reaction mixture to standing for a certain period after the color development; measuring a final absorbance of the reaction mixture; and calculating the total cyanide content in the sample to be detected according to spectrophotometry; and

(8) pumping pure water to empty and clean the mixing tube, the stripping tube, the UV digester, the heater and the condenser.

8. The method of claim 7 , wherein the sample to be detected in step (4) is a water sample to be monitored or a standard sample; the water sample to be monitored is collected to the sampling pipe through a water sample-monitoring tube, and then pumped into the stripping tube through the peristaltic pump; and the standard sample is collected to the sampling pipe through a standard sample tube, and then pumped into the stripping tube through the peristaltic pump.

9. The method of claim 7 , wherein in step (3), air is pumped into the mixing tube to completely mix the chemical agents R 3 and R 4 with pure water; and in step (4), the excess sample to be detected in the stripping tube is discharged from a drain pipe which is provided at an upper portion of the stripping tube.

10. The method of claim 7 , wherein in step (1), the heater has an internal temperature of 80° C., a pulse-heating temperature of 162° C. and a maximum temperature of 165° C.