CN1975391A

CN1975391A - Method for measuring chlorion in lime slurry by nitric acid mercurimetry

Info

Publication number: CN1975391A
Application number: CNA2006100953192A
Authority: CN
Inventors: 杜云贵; 刘艺; 刘清才; 罗晓渝; 洪燕; 蒋聪敏; 潘庆; 廖帆; 赵伟俊; 毛莉; 吴其荣
Original assignee: Chongqing University; CPI Yuanda Environmental Protection Engineering Co Ltd
Current assignee: Chongqing University; CPI Yuanda Environmental Protection Engineering Co Ltd
Priority date: 2006-12-21
Filing date: 2006-12-21
Publication date: 2007-06-06
Anticipated expiration: 2026-12-21
Also published as: CN100458420C

Abstract

The invention provides a method to detect the trace Cl- in the limestone serum by the mercuric nitrate titration. The Cl- reacts with the Hg+ of the mercuric nitrate to form the mercury chloride. When the titration finishes, the redundant Hg+ reacts with the indicator diphenylcarbazone to form the purple complex compound, so the solution color changes from the Kelly to the purple which is the end point. Last to compute the Cl- content according to the titer of the mercuric nitrate. The invention has the simple operation and low cost, it can detect the Cl- of some ppm and get rid of interfere of the sulfurous acid radical, the titration terminal has the evidence color change and easy to distinguish.

Description

Mercuric nitrate complexometry is measured the method for chlorion in the lime stone slurry

Technical field

The present invention relates to the flue gas desulfurization field, particularly the determination of chloride ions in the lime stone slurry of flue gas desulfurization field.

Background technology

China is SO in the world ₂One of country of discharge capacity maximum, annual emissions is near 2,000 ten thousand tons, and its main cause is that coal proportion in energy consumption structure is too big.Flue gas desulfurization (FGD) is to control SO at present ₂The important means of polluting, wherein, wet desulphurization is most widely used flue gas desulfurization technique, has that equipment is simple, the gas-liquid contact is good, desulfuration efficiency is high, an absorbing agent utilization factor height, advantage that processing power is big.Absorbing agent difference, wet desulphurization technology are also different, wherein, adopt lime stone the most ripe, most widely used as the desulfurization method of limestone-gypsum technology of desulfurizing agent.

In the FGD engineering, the main source of chlorion is: the HCl of water-soluble salt of technology and smoke absorption.The harm of chlorion in desulfurization project is mainly reflected in the following aspects:

(1) reduces SO ₂Absorptivity

(2) influence the gypsum quality

(3) etching system equipment

So must detect inevitable chlorine ion concentration accurately and be controlled at certain limit, the detection method of chlorion is many at present, and method commonly used has following several:

(1) automatic potentiometric titration: degree of accuracy is than higher, but this method needs just can finish the cost height by means of automatical potentiometric titrimeter and corresponding auxiliary electrode.

(2) HgCl ₂Titrimetry: with the diphenyl urea is indicator, uses HgCl ₂Titration Cl ion can detect the following Cl ion of 10ppm, but the volumetric soiutions HgCl of this method ₂Belong to extremely toxic substance, endanger very greatly, be difficult for to promote.

(3) silver nitrate titration method: silver nitrate and chloride effect generate silver nitride precipitation, and unnecessary silver nitrate and potassium chromate indicator reaction generate red siliver chromate precipitation, reach terminal point this moment.This method is subjected to Br ^-, I ^-, CN ^-, S ^2-, SO ₃ ^2-Interference bigger; And the red siliver chromate precipitation that titration end-point generates makes solution be muddy state, is difficult for judging the color change process that personal error is big.

(4) other assay methods: ion selecting electrode determining method, the chromatography of ions, polarography etc. all need special support equipment just can finish, the cost height;

Summary of the invention

Problem at present method of testing exists the invention provides a kind of new method-mercuric nitrate complexometry method, and it is a kind of simple to operate, higher, the lower-cost method of testing of degree of accuracy.

Concrete technical scheme is as follows:

A kind of mercuric nitrate complexometry method is surveyed the method for trace chloro ion in the lime stone slurry, may further comprise the steps:

(1) pipettes lime stone slurry 500mL to be measured, cross the leaching supernatant liquor;

(2) volume aspirated be the supernatant liquor of VmL in conical flask, add superoxol and eliminate the interference of inferior sulfate radical titration;

(3) preparation of diphenylcarbazone mixed indicator is by every 0.5g diphenylcarbazone, 0.05g bromophenol blue and 0.12g dimethylbenzene green grass or young crops, is dissolved in each raw material that takes by weighing accurate in scale in the ethanol of 100mL 95%, leave in shake up in the brown bottle standby;

(4) add the diphenylcarbazone mixed indicator of step (3) gained in the conical flask, make solution colour become blueness, dropwise add nitric acid regulator solution pH value then, become blue-green or yellow green from blueness up to solution colour;

(5) be that the mercuric nitrate solution of C1mol/L carries out titration in the conical flask of step (4) with the concentration for preparing, solution colour is titration end-point when blue-green or yellow green become purple, and the mercuric nitrate liquor capacity of consumption is designated as a mL;

(6) use and repeat above-mentioned steps with the distilled water of volume as testing sample with the sample supernatant liquor and do blank test, the mercuric nitrate liquor capacity of consumption is designated as b mL;

(7) the chlorine ion concentration computing formula in the testing sample is

C＝(a-b)×2C ₁×1000×35.54/V

Wherein: the chlorine ion concentration in the C=clear liquid, mg/L

The mercuric nitrate liquor capacity that the a=specimen test consumes, mL

The mercuric nitrate liquor capacity that the b=blank test consumes, mL

C ₁The concentration of=mercuric nitrate complexometry solution, mol/L

35.54 be the chlorion atomic weight

The clear liquid volume that V=pipettes, mL

The data substitution formula of measuring is calculated chlorine ion concentration.

Principle of the present invention is that chlorion and mercury ion react, form sl. sol. mercuric chloride, during titration end-point, unnecessary mercury ion and diphenylcarbazone indicator reaction generate violet complex, solution colour is mutated into purple by yellow green and is terminal point, and the titer according to mercuric nitrate calculates chloride ion content at last.Chemical equation is as follows:

The used indicator of the present invention must be by described proportionate relationship preparation, if the blending ratio difference is difficult to observe change color.

It is in order to eliminate the interference of inferior sulfate radical to titration that step (2) adds superoxol, per generally speaking 100 milliliters of supernatant liquors need add about 1～2 milliliter of superoxol, must add capacity, if the sulfite ion in the sample can not can be made resultant error increase by abundant oxidation very little.

Step (4) adds nitric acid regulator solution pH value, become blue-green or yellow green up to solution colour from blueness, through the pH value of measuring this moment is 3.1, if nitric acid adds excessively in the adjustment process, the NaOH that can add 0.1mol/L in addition is transferred to about 3.1 up to pH value.The concentration of nitric acid selects can be 0.1mol/L.

Step (6) is in order to reduce error with distilled water as blank assay.

We have carried out the contrast experiment of two kinds of methods to slurries clear liquid of the same race, and experimental result is as follows:

The experimental result contrast of table 1 the inventive method and silver nitrate titration method

Project	Chlorinity, mg/L
	Chlorinity, mg/L			Sample one	Sample two	Sample three
	Silver nitrate titration method the inventive method	9.56 9.38	10.46 10.19	Sample one	Sample two	Sample three	9.04 8.91

We find in the experimentation, and the change color of the titration end-point of silver nitrate titration method is not clearly, does not have the mutation process of color, are difficult to accurately determine terminal point; And titration end-point color change of the present invention is very obvious, is beneficial to observation.

From the experimental result of table 1, the experimental result that adopts silver nitrate titration method to measure is slightly higher than inventive method, and reason one is because the SO of some in the slurries ₃ ^2-Ion, and silver nitrate titration method SO ₃ ^2-Interference bigger; Reason two is exactly that the titration end-point variable color of silver nitrate titration method is obvious inadequately, the red siliver chromate precipitation that titration end-point generates makes solution be muddy state, add to the difficulties for the change color of judging solution, just because of above-mentioned two reasons, so the result who adopts silver nitrate titration method to measure understands higher.

Beneficial effect of the present invention is embodied in the following aspects:

(1) simple to operate, cost is low, and conventional buret just can be finished this experiment;

(2) precision height can detect the chlorion of several ppm;

(3) the titration end-point variable color is obvious, easily distinguishes, solution colour becomes tangible purple by yellow green; Bromophenol blue in the mixed indicator solution is the pH indicator, and the grey that can shelter diphenylcarbazone itself makes the variable color of titration end-point more obvious;

(4) this invention adopts superoxol to get rid of SO ₃ ^2-The interference of ion, accuracy is higher.

Specific embodiment

Embodiment 1 mercuric nitrate complexometry method detects the chlorine ion concentration in the lime stone slurry

Step is as follows:

(2) volume aspirated be the supernatant liquor of 100mL in conical flask, add 1 milliliter of interference of eliminating inferior sulfate radical to titration of superoxol of capacity;

(3) preparation of diphenylcarbazone mixed indicator accurately takes by weighing 0.5g diphenylcarbazone, 0.05g bromophenol blue and 0.12g dimethylbenzene green grass or young crops, is dissolved in 95% the ethanol of 100mL, leave in shake up in the brown bottle standby;

(4) add the diphenylcarbazone mixed indicator of step (3) gained in the conical flask,, dropwise add the nitric acid regulator solution pH value of 0.1mol/L then, become blue-green or yellow green from blueness up to solution colour up to making solution colour become blueness;

(5) the mercuric nitrate solution with the 0.01mol/L for preparing carries out titration in conical flask, and solution colour is titration end-point when blue-green or yellow green become purple, and the mercuric nitrate liquor capacity of consumption is designated as 1.34mL;

(6) use and repeat above-mentioned steps with the distilled water of volume as testing sample with the sample supernatant liquor and do blank test, the mercuric nitrate liquor capacity of consumption is 0.02mL;

(7) with data substitution formula C=(a-b) * 2C ₁The chlorine ion concentration that calculates in the testing sample among * 1000 * 35.54/V is

(1.34-0.02) * 2 * 0.01 * 1000 * 35.54/100=9.38mg/L is 9.38ppm

The comparative example detects the chlorine ion concentration of sample among the embodiment 1 with silver nitrate titration method

(1) pipettes the 500mL slurries, leave standstill, cross the leaching supernatant liquor;

(2) pipette clear liquid 100mL in conical flask;

(3) add several phenolphthalein indicators in conical flask, dropwise add the sodium hydroxide solution of 0.1mol/L then, up to the solution colour baby pink, the salpeter solution with 0.05mol/L drips to colourless then; 10% the potassium chromate solution that adds 1mL again.

(4) liquor argenti nitratis ophthalmicus with 0.01mol/L carries out titration, and solution colour becomes and is terminal point when brick-red, and the volume of the liquor argenti nitratis ophthalmicus that consume this moment is 2.71mL.

(5) volume of the liquor argenti nitratis ophthalmicus of blank test consumption is 0.02mL.

Chlorine ion concentration in the clear liquid:

(2.71-0.02) * 0.01 * 1000 * 35.54/100=9.56mg/L is 9.56ppm

Embodiment 1 compares with the comparative example, because SO ₃ ^2-The interference of ion, the result that the titration end-point variable color obviously makes silver nitrate titration method record inadequately is higher.

Claims

1. a mercuric nitrate complexometry is measured the method for chlorion in the lime stone slurry, may further comprise the steps:

(1) pipettes lime stone slurry to be measured, cross the leaching supernatant liquor;

(5) be C with the concentration for preparing ₁The mercuric nitrate solution of mol/L carries out titration in the conical flask of step (4), solution colour is titration end-point when blue-green or yellow green become purple, and the mercuric nitrate liquor capacity of consumption is designated as amL;

(6) use and repeat above-mentioned steps with the distilled water of volume as testing sample with the sample supernatant liquor and do blank test, the mercuric nitrate liquor capacity of consumption is designated as bmL;