Separation and determination of the hottest sulfid

Separation and determination of sulfide and sulfur dioxide

at room temperature, volatile sulfur compounds mainly include hydrogen sulfide and sulfur dioxide. Their determination is very important for the morphological analysis of sulfur compounds. Since natural gas and industrial waste gas usually contain these two different forms of sulfides, the establishment of a simple, fast and accurate analysis method is the premise of effectively controlling pollution and making full use of chemical waste. We have used the dual wavelength method to determine the content of hydrogen sulfide and sulfur dioxide in the mixture [1], but this method has certain limitations. In this paper, two different forms of sulfide were separated by preconcentration method, and different forms of sulfide were determined by atomic absorption spectrophotometer. Through the analysis of mixed samples, it is known that this is a fast and effective method for the determination of hydrogen sulfide and sulfur dioxide with simple instrument and easy operation. It is particularly important that this method lays a foundation for the development of sulfide testing instruments

1 experimental part

1.1 instrument

hg-9001 atomic absorption spectrophotometer (Shenyang analytical instrument factory). Lz-1010 combined flow injection analyzer (Shenyang film reflector factory)

the absorption cell is a quartz tube with a length of 120 mm, an inner diameter of 5 mm, an outer diameter of 7 mm, and quartz windows on both sides. The absorption cell is fixed on the combustion head of the flame atomizer

reactor: the inner diameter is 10 mm and the height is 150 mm. In the experiment, the peristaltic pump is used to inject samples, and the volume of the mixed liquid (sample solution + reaction liquid) in the reactor is controlled by adjusting the height of the liquid level in the reactor

concentrator: inner diameter 15 mm, height 200 mm

concentrated H3PO4 tank: inner diameter 10 mm, length 100 mm, containing 7 ml of concentrated H3PO4

1.2 reagent

the reaction solution is dilute HCl solution. S2 standard stock solution, while the proportion of plastic granulation performance consumption in China in total industrial energy consumption is almost 1.5 (1.000) higher than that in Britain × 103mg/l): it is prepared with na2s.9h2o and calibrated by iodometry. The calibration method is the same as that in literature [2]

so2 standard stock solution (1.00 × 103mg/ml): it is prepared with Na2SO3 and calibrated by iodometry. The calibration method is the same as that in literature [3]

the experimental water is distilled water, and all reagents are superior grade pure or analytical pure. The carrier gas is nitrogen with purity of 99.99%

1.3 experimental method

experimental device is shown in Figure 1. The peristaltic pump pumps the blank sample and reaction liquid, and adjusts the liquid seal height to make the liquid volume in the reactor the best. After blowing the carrier gas to the absorbance value of 0.000, add a certain volume of BaCl2 solution into C (SO2 concentrator); D (H2S preconcentrator) add a certain volume of NaOH solution. Under certain conditions, barium chloride can react with sulfur dioxide instead of hydrogen sulfide, so hydrogen sulfide can enter the D concentrator through the C concentrator. Replace the blank sample with the sample and continue to inject the sample. After entering a certain volume of sample, turn off the pump and let the carrier gas into the air. Add a certain volume of hydrochloric acid into D, turn e to 2, bring the generated H2S into the absorption tank with carrier gas, read the absorbance value, and then discharge the solution in D into the waste liquid tank. Turn e to 1, add a certain amount of hydrochloric acid to C, and turn e to 2. The carrier gas will bring the released SO2 gas into the absorption tank, and read the absorbance value

Figure 1 experimental device for separation and determination of H2S and SO2

a flowmeter; b. Reactor; 2 preconcentrator; d. H2S preconcentrator; e. Tee piston; f. Mixing pipe

g concentrated H3PO4 pool; h. Absorption tank; i. Quartz window; j. Liquid seal pipe; k. L injection port

2 results and discussion

according to the absorption spectra of H2S and SO2 in the ultraviolet visible region, magnesium hollow cathode lamp is selected as the light source, and the wavelength is 202.6 nm

2.1 selection of experimental conditions for SO2 determination

2.1.1 effect of pH value of enrichment solution on absorbance

so2 enrichment solution adopts barium chloride solution, and the effect of pH value of barium chloride solution on absorbance is shown in Figure 2. In order to control the pH value of barium chloride solution, we adjust it with HAC NaAc buffer. See Table 1 for the preparation methods of buffers with different pH values

Fig. 2 Effect of pH value of SO2 enrichment solution on absorbance value

so2 content is 27.0 μ G/ml, the concentration of HCl in the reaction solution is 1 mol/L,

carrier gas flow is 300 ml/min, the enrichment solution is BaCl2,

pH is adjusted with the buffer solution prepared by HAC NaAc

Table 1 Preparation of buffer solution

phvnaac/mlvhac/mlvnaac/vhac4.101.04.00.254.651.01.01.005.264.01.04.005.8516.01.016.06.0024.51.024.5

* the content of NaAc and HAC is 0.1 mol/l.

it can be seen from Figure 2 that the absorbance value increases with the increase of pH value. When the pH value is small, SO2 adsorption is incomplete, so the absorbance value is small; The installation project took 1 hour. When pH = 6, the absorbance value was the largest; When ph>6, some H2S is adsorbed, and the purpose of separation cannot be achieved. In HAC NaAc buffer system, the maximum pH value is 6. Even if only NaAc solution is used, because the reaction solution is HCl solution, HCl will always be brought into the enrichment solution to form HAC NaAc buffer solution and reduce the pH. Therefore, the pH value selected in this paper is 6

2.1.2 influence of carrier gas flow on absorbance value during SO2 separation and enrichment Figure 3 shows the relationship between carrier gas flow rate and absorbance. The results show that the absorbance value is the largest when the carrier gas flow is 300 ~ 400 ml/min; If the flow is too small, the absorbance value is also small, and some SO2 may not be carried out; When the carrier gas flow is too large, the reaction between SO2 and the enrichment solution is incomplete due to the short residence time in the concentrator

Figure 3 Effect of carrier gas flow rate on absorbance value

so2 content 28.0 μ G/ml, the content of HCl in the reaction solution is 1 mol/l, the volume of the enrichment solution is 1.5 ml, and the pH of the enrichment solution is 6

2.1.3 effect of hydrochloric acid content in the reaction solution on the absorbance value of sulfur dioxide Figure 4 shows the effect of hydrochloric acid content in the reaction solution on the absorbance. Figure 4 shows that the absorbance value is the largest when the HCl content in the reaction solution is 1 mol/l; If the content of HCl is too small, the reaction is incomplete, resulting in the decrease of absorbance value; If the content of HCl is too large, some HCl will be carried into the concentrator, so that the pH value of the enrichment solution will be reduced, SO2 adsorption is incomplete, and the measured absorbance value is low

Figure 4 Effect of hydrochloric acid content of reaction solution on absorbance value

so2 concentration is 28 μ G/ml, the carrier gas flow rate is 300 ml/min,

the volume of the enrichment solution is 1.5 ml, and the content of BaCl2 in the enrichment solution is 0.1 mol/L.

2.1.4 the influence of HCl content used to release SO2 on the absorbance test results show that the absorbance value increases with the increase of HCl content, and when the HCl content reaches 1.0 mol/L, the absorbance value will no longer change significantly with the change of HCl content

2.1.5 effect of BaCl2 content in enrichment solution when the content of BaCl2 in enrichment solution is greater than 0.05 mol/l, it has no effect on the measured value. The content of BaCl2 solution we selected is 0.1 mol/L

2.2 selection of experimental conditions for determining H2S

2.2.1 effect of carrier gas flow rate on absorbance Figure 5 shows the effect of carrier gas flow rate on absorbance for enrichment and separation. The results in Figure 5 show that the absorbance value is the largest when the flow rate is 400 ml/min. When the flow rate of carrier gas is too small, H2S is not completely carried, resulting in reduced absorbance; If the flow rate of carrier gas is too large, the residence time of H2S gas in the concentrator is short, and the reaction is incomplete, so the absorbance value decreases. Considering that the Ministry of science and technology of SO2 has set up a major research and development special determination of material genome, the carrier gas flow selected in this paper is 400 ml/min

Figure 5 Effect of concentration and separation carrier gas flow rate on absorbance

s2- content 1.9 μ G/ml, HCl content is 1 mol/ml.

2.2.2 effect of NaOH content in the enrichment solution on the absorbance value

when keeping the HCl content in the reaction solution twice the NaOH content and with the same volume, the absorbance increases slightly with the increase of NaOH content, because with the increase of content, the neutralization heat increases, which accelerates the release of H2S

2.2.3 effect of HCl content in the reaction solution on absorbance

in the enrichment process, when the NaOH content of the enrichment solution is 0.5 mol/l, the HCl content is between 1 ~ 2 mol/l, and the absorbance value is the largest. If the HCl content is small, the reaction is incomplete and the absorbance value decreases. When the content of HCl is large, it will enrich 3. Lubricating oil: regularly fill the transmission parts (such as screws) of the machine every month with lubrication (choose ordinary lubricating oil). The reaction is incomplete and the absorbance is reduced

according to the above experimental results, the experimental conditions are selected in this experiment: the acidity of BaCl2 solution in SO2 enrichment solution is ph=6 (NaAc HAC), the concentration of BaCl2 in SO2 enrichment solution is 0.1 mol/l, the flow rate of carrier gas (N2) is 400 ml/min, the content of hydrochloric acid in reaction solution is 1.0 mol/l, the content of hydrochloric acid in release solution is 1.0 mol/L, the content of NaOH in H2S enrichment solution is 0.5 mol/L, the volume of SO2 enrichment solution is 1.5 ml, and the volume of H2S enrichment solution is 1.5 ml. Table 2 lists the detection limit, linear range and precision of s2- and SO2. The concentration of the tested substance used to determine the precision is 100 times of the detection limit, and the number of determinations is 8. Table 2 sulfur and sulfur dioxide analysis performance

sample linear range/（ μ g. ML-1) detection limit/（ μ g. ML-1) RSD (%) enrichment factor s.04 ~ 50.022.12.3so20.2 ~ 400.081.92.1

2.3 interference

at 202.6nm, the interference of some coexisting anions on the determination of s2- and so was studied. When the content of s2- is 1.02 μ G/ml, so content is 10 μ At g/ml, 100 times of br-, Co, scn- and NO-3 and 10 times of NO-2 do not interfere with the determination

2.4 analysis of mixed samples

according to the above experimental conditions, several synthetic samples were analyzed, and the test results are listed in Table 3. It can be seen from table 3 that the ratio of SO2 to H2S in the mixed sample is between 2 and 100 times, which can be determined by this method, as long as the content of the tested sample is within its linear range. The results show that this method can be used for the separation and determination of s2- and so. Table 3 sample analysis results

mixed samples/（ μ g. ML-1) actual measured value/（ μ g. ML-1) recovery (%) h2sso2h2sso2h2sso20.1010.000.109 2010.000.219.. 5010.000.549.. 0010.001.009.. 0010.002.019.. 0010.004.9010.

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