CN112924252B - A kind of analysis method of lead form in ash - Google Patents

Abstract

The invention discloses a morphological analysis method of lead in ash, belonging to the field of morphological analysis of trace elements. The method comprises the following steps: firstly, adding a separating agent 1, and separating to obtain X ₁ ＝PbCl ₂ +PbSO ₄ (ii) a Secondly, adding a separating agent 2, and separating to obtain X ₂ ＝PbO+PbCO ₃ (ii) a Thirdly, digesting and separating to obtain X ₃ Lead in other forms, generally considered to be aluminosilicate bound; fourthly, adding a separating agent 3, and separating to obtain Y ₁ ＝PbCl ₂ +PbO+PbCO ₃ For part of special ash, CaO is added in the step to enlarge the application range of the invention; fifthly, adding a separating agent 1, and separating to obtain Y ₂ ＝PbSO ₄ (ii) a Sixthly, digesting and separating to obtain Y ₃ Lead in other forms, generally considered as aluminosilicate bound lead; and finally calculating and analyzing. The method for analyzing the lead form in the ash can be used for analyzing lead-containing compounds in solids such as coal-fired power plant ash, waste incineration ash, biomass combustion ash and the like. The establishment of the lead form analysis method is beneficial to researching the lead migration and transformation process in the solid combustion process, and further the lead removal and transformation are enhanced.

Description

A kind of analysis method of lead form in ash

technical field

The invention belongs to the field of speciation analysis of trace elements, and more particularly relates to a speciation analysis method of lead in ash.

Background technique

Lead is a serious environmental and neurotoxin. Lead can affect the functions of the human nervous system, cardiovascular system, skeletal system, reproductive system and immune system, and cause diseases of the gastrointestinal tract, liver, kidney and brain. Especially in the stage of growth and development, children are more sensitive to lead than adults. The lead that enters the body has a strong affinity for the nervous system, so the absorption of lead is several times higher than that of adults, and the damage is particularly serious. Lead into the body of pregnant women will pass through the placental barrier, affecting fetal development, resulting in deformities.

Lead is a semi-volatile heavy metal, which is mainly concentrated in ash and slag in the process of solid combustion and flue gas emission. When lead exists in a relatively stable form in solid fuels, such as in the form combined with aluminosilicate, it is difficult to be released during the combustion process, and most of it remains in the ash; lead is relatively stable in solid fuels. Unstable forms, such as lead sulfide, lead chloride, etc., may form lead oxide at higher temperatures, and may react with components in the flue gas such as sulfur dioxide, hydrogen chloride, water vapor, etc. during the cooling process , resulting in a variety of lead compounds; it may also have physical and chemical interactions with components such as aluminosilicates in the ash. It can be seen that there are various forms of lead in the ash. When considering the impact of an element on the ecological environment, it cannot be separated from its form. The condensation characteristics of different forms of lead will affect the migration and transformation of lead in the combustion process, and the leaching characteristics and toxicity of different forms of lead will affect the stability of lead in the environment and the harm to the environment. When analyzing lead in ash and slag, by understanding the distribution of these lead forms in ash, it is beneficial to explore the migration and transformation of lead in the process of solid combustion, and then strengthen the removal and transformation of lead in the process of solid fuel combustion.

Therefore, a lead speciation analysis method is needed as a means of in-depth research. At present, the morphological analysis of lead at home and abroad mainly relies on BCR, Tessier morphological analysis methods, and X-ray absorption near-edge structure or extended X-ray absorption fine structure. However, the first two lead speciation analysis methods are mainly aimed at environmental samples, and lead can be roughly divided into acetic acid extractable state, oxidized state, reduced state and residue state, and it is impossible to specifically distinguish each lead-containing compound. The latter two analysis methods are limited by the detection limit. Lead is a trace element, and its content in ash is extremely low. At such a concentration, it is difficult to quantitatively analyze the form of lead in ash.

Chinese patent CN 109030391 proposes a method for measuring soluble lead and soluble zinc in mixed lead-zinc concentrate, which divides lead into soluble lead-zinc, insoluble lead-zinc and lead-zinc sulfide. Chinese patent CN107840587 proposes a method for high-efficiency fixation of heavy metal lead in municipal sludge, wherein the content of lead in each form in the sludge needs to be determined in one step. The method only divides lead forms into exchangeable state, carbonate-bound state, iron-manganese oxide-bound state, organic matter-bound state and residue state. Chinese patent CN 106338478 proposes a method for measuring lead form in cigarette smoke, which divides lead into effective state, slow-acting state and residual state. Chinese patent CN106525802 proposes a method and device for the determination of lead form in cigarette smoke. The method separates inorganic lead, trimethyl lead chloride, triethyl lead chloride and triphenyl lead chloride. These speciation analysis methods simply divide lead into several categories, which cannot meet the requirement of studying lead migration and transformation during solid combustion by analyzing lead speciation distribution in ash.

SUMMARY OF THE INVENTION

In view of the defects of the related art, the object of the present invention is to provide a method for analyzing lead forms in the ash, aiming to solve the problem that the existing form analysis methods cannot distinguish lead chloride, lead sulfate, oxidized lead and aluminosilicate binding state lead problem.

To achieve the above object, the invention provides a method for analyzing lead form in the ash, comprising the following steps:

S1, take the original ash sample and add Na ₂ S ₂ O ₃ solution to carry out leaching, centrifugation, solid-liquid separation, test the obtained liquid, and measure the content of X ₁ =PbCl ₂ +PbSO ₄ ; Filter and dry to obtain ash A;

S2, adding CH ₃ COONH ₄ buffer solution to the ash residue A to carry out leaching, centrifugation and solid-liquid separation, test the obtained liquid, and measure the content of X ₂ =PbO+PbCO ₃ ; Solid-liquid separation and drying to obtain ash B;

S3, add digestion liquid to described ash residue B to carry out digestion, constant volume, centrifugation, solid-liquid separation, test the obtained liquid, and record X ₃ = the content of lead in other forms;

S4, take the original ash sample and add CH ₃ COOH solution to carry out leaching, centrifugation, solid-liquid separation, test the obtained liquid, and measure the content of Y ₁ =PbCl ₂ +PbO+PbCO ₃ ; wash and filter the obtained solid , dried to obtain ash C;

S5, adding Na ₂ S ₂ O ₃ solution to the ash C to carry out leaching, centrifugation, solid-liquid separation, test the obtained liquid, and measure the content of Y ₂ =PbSO ₄ ; Liquid separation and drying to obtain ash D;

S6, adding digestion solution to the ash slag D for digestion, centrifugation, and solid-liquid separation, and testing the obtained liquid to measure the content of Y ₃ = other forms of lead;

S7, calculate the lead content of each form, so as to analyze the form of lead in the ash.

Preferably, for ash samples with Ca/S less than 5, S is likely to generate SO ₄ ^2- or SO ₃ ^2- combined with Pb ²⁺ during the leaching process to form precipitation, resulting in incomplete separation. Improvements are made: CaO is added to the raw ash sample in step S4, and the Ca/S ratio of the raw ash sample is adjusted to 5.0-9.0. Experiments show that this improvement is effective.

Further, the calculation method of the lead content of each form is:

C(PbCl ₂ )=X ₁ -Y ₂ =Y ₁ -X ₂ ;

C(PbSO ₄ )=Y ₂ ;

C(PbO+PbCO ₃ )=X ₂ ;

C (other forms of lead) = X ₃ =Y ₃ .

Further, the raw ash sample is coal combustion ash, garbage incineration ash or biomass combustion ash.

Further, the pH value of the CH ₃ COONH ₄ buffer solution was adjusted with CH ₃ COOH, and the pH value was 3.000-5.750.

Further, the concentration range of the Na ₂ S ₂ O ₃ solution is 0.2-2 mol/L; the concentration range of CH ₃ COONH ₄ in the CH ₃ COONH ₄ buffer solution is 0.1-3 mol/L; the concentration range of the CH ₃ COOH solution is 0.03 ~3mol/L.

Further, the leaching process uses inversion shaking, magnetic stirring, ultrasonic or microwave-assisted leaching.

Further, the leaching time depends on the leaching method. For ultrasonic and microwave-assisted leaching, the leaching time can be shortened by up to 35 times compared with flipping oscillation.

Further, the rotational speed of the centrifugation ranges from 2000 to 6000 rpm, and the centrifugation time is 2 to 10 minutes.

Further, in the steps S3 and S6, the digestion system is mainly concentrated nitric acid, and concentrated hydrochloric acid, hydrofluoric acid or hydrogen peroxide is added to strengthen the digestion process.

Further, the solid-liquid ratio of the solid and the separating agent in the solid-liquid separation process is 1:10-1:400.

Further, in order to maintain the stability of the separating agent, the two-step leaching process of S1 and S5 needs to be performed in the dark.

Further, the two-step leaching process of S1 and S5 needs to be carried out in the temperature range of 10-30 °C, and the two-step leaching process of S2 and S4 needs to be carried out in the temperature range of 20-70 °C, and the higher the temperature, the more beneficial it is. Speed up the extraction process.

Through the above technical solutions conceived by the present invention, compared with the prior art, the following beneficial effects can be achieved:

(1) lead chloride, lead sulfate, oxidized lead and aluminosilicate binding lead cannot be distinguished for existing morphological analysis methods, the present invention has selected a separating agent in a targeted manner, and established a set of lead morphological analysis methods , combined with atomic absorption spectrometer, inductively coupled plasma mass spectrometry and other test methods to analyze the lead form in the ash and slag, and provide a method for exploring the migration and transformation of lead in the combustion process and the enhanced removal mechanism.

(2) In the actual application process, in view of the problem that the complex components in the actual ash will interfere with the separation process, such as the ash with Ca/S less than 5, S is easy to generate SO ₄ ^2- or SO ₃ ^2- under acidic conditions Combined with Pb ²⁺ to form precipitation, resulting in incomplete separation of lead species. According to the actual ash Ca/S, CaO was added to adjust the Ca/S, which weakened the influence of the complex components in the ash on the leaching, and made the previous morphological analysis method suitable for ash of various properties.

(3) By analyzing the morphological distribution of lead in the ash, the migration and transformation of lead in the solid combustion process can be explored, thereby strengthening the removal of lead. The method has high recovery rate, good repeatability, strong operability, and is easy to implement. Therefore, a platform with relatively poor equipment can also use this method to analyze the form of lead in ash.

Description of drawings

Fig. 1 is the step diagram of the analysis method of lead form in ash and slag.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

The invention provides a method for analyzing lead form in ash, the process is shown in Figure 1, and includes the following steps:

The first step is to weigh the raw ash into the centrifuge tube, add the separating agent 1 to the centrifuge tube, carry out leaching, centrifugation, solid-liquid separation with Na ₂ S ₂ O ₃ solution, test the liquid, and measure X ₁ = The content of PbCl ₂ +PbSO ₄ . The solid was washed with deionized water, filtered and dried, and ash A was retained.

In the second step, the separating agent 2 is added to the ash A obtained in the first step, and the _{CH 3} COONH ₄ buffer solution is used for leaching, centrifugation, and solid _- liquid separation, and the liquid is tested. content. The solid was washed with deionized water, and the solid-liquid was separated and dried, and the ash residue B was retained.

In the third step, add a digestion solution to the ash residue B obtained in the second step to carry out digestion, constant volume, centrifugation, and solid-liquid separation, and test the liquid to find that X ₃ = lead in other forms, generally mainly aluminosilicate The content of lead in salt-bound form.

The fourth step, weigh the raw ash into the centrifuge tube, add separating agent 3 into the centrifuge tube, carry out leaching, centrifugation, solid-liquid separation with CH ₃ COOH solution, test the liquid, and measure Y ₁ =PbCl ₂ + Content of PbO + PbCO ₃ . The solid was washed with deionized water, filtered and dried, and the ash C was retained.

The fifth step, adding separating agent 1 to the ash residue C obtained in the fourth step, carrying out leaching, centrifugation, solid-liquid separation with Na ₂ S ₂ O ₃ solution, testing the liquid, and measuring the content of Y ₂ =PbSO ₄ . The solid was washed with deionized water, the solid-liquid was separated and dried, and the ash D was retained.

In the sixth step, adding a digestion solution to the ash D obtained in the fifth step for digestion, centrifugation, and solid-liquid separation, and testing the liquid, it was found that Y ₃ = lead in other forms, generally mainly aluminosilicate-bound lead. content.

The seventh step, calculate:

C(PbCl ₂ )=X ₁ -Y ₂ =Y ₁ -X ₂ ;

C(PbSO ₄ )=Y ₂ ;

C(PbO+PbCO ₃ )=X ₂ ;

C (other forms of lead) = X ₃ =Y ₃ .

Further, the ash can be lead-containing solids such as coal combustion ash, waste incineration ash, biomass combustion ash and the like. For each analysis, according to the lead content in the ash, the amount of ash can be weighed as 0.00A0g.

Further, in all the steps, the solid-liquid ratio of the solid and the separating agent can be 1:10-1:400; in the process of separating other forms of lead in the third step and the sixth step, each gram of ash corresponds to 10mL-400mL digestion. liquid.

Further, the separating agent 2 is a CH ₃ COONH ₄ buffer solution, the pH value of which is adjusted with CH ₃ COOH, and the pH value is between 3.000-5.750.

Further, the separating agent 1 is a Na ₂ S ₂ O ₃ solution with a concentration range of 0.2-2 mol/L; the separating agent 2 is a CH ₃ COONH ₄ buffer solution, wherein the CH ₃ COONH ₄ concentration range is 0.1-3 mol /L; separating agent 3 is a CH ₃ COOH solution with a concentration range of 0.03-3 mol/L.

Further, the leaching time in each step can be adjusted. For example, the leaching time is in the range of 3h-10h in the first step; the leaching time in the second step is 6-18h; the third step is digestion The time range is 0.5h-10h; the fourth step extraction time range is 16h-32h; the fifth step extraction time range is 6h-18h; the sixth step digestion time range is 0.5h-10h; if the solid sample is difficult to separate The substances can be assisted in the leaching process by other means, including but not limited to inversion oscillation, magnetic stirring, ultrasound, and microwave assistance. If ultrasonic extraction is used, the extraction time range of the first step is 5-30min; the extraction time range of the second step is 10-80min; the digestion time range of the third step is 0.5h-10h; the extraction time range of the fourth step is 40-120min; the fifth step extraction time range is 5-30min; the sixth step digestion time range is 0.5h-10h;

Further, in each step of the method, the centrifugal speed range is 2000-6000 rpm, and the centrifugal time is 2-10 min.

Further, in order to maintain the stability of the separating agent, the leaching process of the first step and the fifth step in the method needs to be performed in the dark.

Further, the leaching process of the first step and the fifth step in the method needs to be carried out in the temperature range of 10-30°C, and the leaching process of the second step and the fourth step needs to be carried out in the temperature range of 20-70°C. , and the higher the temperature, the more conducive to speed up the leaching process.

Further, in the third step and the sixth step, the digestion system is mainly concentrated nitric acid, and reagents including but not limited to concentrated hydrochloric acid, hydrofluoric acid, hydrogen peroxide and the like can be added to strengthen the digestion process. The digestion time range is 0.5h-10h. The digestion temperature range is 80-230°C.

Further, in order to solve the problem that the lead content in the ash is too low, it may not be possible to detect this phenomenon in the separating agent. Lead content in each ash. The lead content of each form is obtained by the following calculation:

X ₁ =C(raw ash)-C(ash A)

X ₂ =C(ash A)-C(ash B)

X ₃ =C (ash B)

Y ₁ =C(raw ash)-C(ash slag C)

Y ₂ =C(ash C)-C(ash D)

Y ₃ =C (ash D)

C(PbCl ₂ )=X ₁ -Y ₂ =Y ₁ -X ₂ ;

C(PbSO ₄ )=Y ₂ ;

C(PbO+PbCO ₃ )=X ₂ ;

C (other forms of lead) = X ₃ =Y ₃ .

Further, in order to solve the phenomenon that other components in the ash interfere with the leaching process, it has been verified by experiments that adjusting the Ca/S ratio and controlling the Ca/S between 5.0 and 9.0 can effectively reduce the interference of other components. .

The invention can separate lead compounds of different forms, and provides a method for exploring the migration and transformation process of lead in the solid combustion process.

Now, the present invention will be further described in detail by taking the specific analysis method of lead in slag as an example.

Example 1

The first step is to weigh 5g of coal-fired ash residue into the centrifuge tube, add the separating agent 1, 0.3mol/L Na ₂ S ₂ O ₃ solution into the centrifuge tube, and shake and extract on the shaker for 10h. The solid-liquid ratio is 1:20, centrifuge at 5000 rpm for 3 min on a centrifuge, separate the solid from the liquid, wash the solid with deionized water, filter and dry, and retain ash A. Since the lead content in the coal ash is too low, it is difficult to detect the lead content in the liquid. The ash A was digested and tested, and the lead content C (ash A) in the ash A was measured.

The second step, repeat the first step, add separating agent 2, 0.2mol/L CH ₃ COONH ₄ buffer solution (pH=4.5000) to the ash A, and shake and leaching for 18h on the inversion shaker, and the solid-liquid ratio is 1: 20. Centrifuge at 5000 rpm for 3 min on a centrifuge, separate solid from liquid, wash the solid with deionized water, filter and dry, and retain ash B. Due to the low lead content in the coal ash slag, it is difficult to detect the lead content in the liquid. The ash slag B was digested and tested, and the lead content C (ash slag B) in the ash slag B was measured.

The third step is to digest the ash residue A retained in the first step, the B retained in the second step and the original ash residue. The volume of acid added per 1g of sample is 20g, and the digestion system is concentrated nitric acid, concentrated hydrochloric acid and hydrofluoric acid, with a volume ratio of 6:2:2, digested with a microwave digestion apparatus, digested at 200 °C for 40 min, and driven acid at 130 °C 2h, constant volume, centrifuge at 5000rpm for 3min on the centrifuge, solid-liquid separation, test the liquid, and the lead content C in ash A (ash A) and the lead content in ash B can be measured respectively. C (ash slag B), lead content in the original ash slag C (original ash slag).

The fourth step, weigh 5g of coal-fired ash slag into the centrifuge tube, add separating agent 3, 0.5mol/LCH ₃ COOH solution into the centrifuge tube, shake for 32h on an inversion shaker, the solid-liquid ratio is 1:20, centrifuge The machine was centrifuged at 5000 rpm for 3 min to carry out solid-liquid separation, the solid was washed with deionized water, filtered and dried, and the ash C was retained. Since the lead content in the coal ash is too low, it is difficult to detect the lead content in the liquid. The ash C was digested and tested, and the lead content C (ash C) in the ash C was measured.

The fifth step, repeat the fourth step, add separating agent 1, 20mL 0.3mol/LNa ₂ S ₂ O ₃ solution to the solid obtained in the fourth step, shake it on an inversion shaker for 10h, the solid-liquid ratio is 1:20, Centrifuge at 5000 rpm for 3 min on a centrifuge to separate solids and liquids, wash the solids with deionized water, filter and dry, and retain ash D. Since the lead content in the coal ash is too low, it is difficult to detect the lead content in the liquid. The ash D was digested and tested, and the lead content C (ash B) in the ash D was measured.

The sixth step is to digest the ash residue C retained in the fourth step, the D retained in the fifth step and the original ash residue. The volume of acid added per 1g of sample is 20g, and the digestion system is concentrated nitric acid, concentrated hydrochloric acid and hydrofluoric acid, with a volume ratio of 6:2:2, digested with a microwave digestion apparatus, digested at 200 °C for 40 min, and driven acid at 130 °C 2h, set the volume, centrifuge at 5000rpm for 3min on the centrifuge, separate the solid and liquid, and test the liquid. The lead content C in the ash C (ash C) and the lead content in the ash D can be measured respectively. C (ash slag D), lead content in the original ash slag C (original ash slag).

The seventh step, calculate:

X ₁ =C(raw ash)-C(ash A)

X ₂ =C(ash A)-C(ash B)

X ₃ =C (ash B)

Y ₁ =C(raw ash)-C(ash slag C)

Y ₂ =C(ash C)-C(ash D)

Y ₃ =C (ash D)

C(PbCl ₂ )=X ₁ -Y ₂ =Y ₁ -X ₂ ;

C(PbSO ₄ )=Y ₂ ;

C(PbO+PbCO ₃ )=X ₂ ;

C (other forms of lead) = X ₃ =Y ₃ .

Through this example 1, the lead content in the liquid obtained in each step is measured by atomic absorption spectrometer, and the content of PbCl ₂ in the coal ash slag is 9.35mg/kg, the content of PbSO ₄ is 13.24mg/kg, and the content of PbO+PbCO ₃ It is 28.81mg/kg, and the lead content in aluminosilicate bound state is 31.51mg/kg.

Example 2

The first step is to weigh 0.05g of grate furnace waste incineration ash into the centrifuge tube, add 1,2mol/L Na ₂ S ₂ O ₃ solution of the separating agent into the centrifuge tube, ultrasonically extract for 10min, and the solid-liquid ratio is 1 : 40, centrifuge at 3500 rpm for 4 min on a centrifuge, separate the solid from the liquid, test the liquid, and measure the content of X ₁ =PbCl ₂ +PbSO ₄ . The solid was washed with deionized water, filtered and dried, and the solid ash A was retained.

In the second step, adding a separating agent 2,3mol/L CH ₃ COONH ₄ buffer solution (pH=4.000) to the solid ash A obtained in the first step, ultrasonic leaching for 20min, the solid-liquid ratio is 1:40, on the centrifuge Centrifuge at 3500 rpm for 2 min, separate the solid from the liquid, test the liquid, and measure the content of X ₂ =PbO+PbCO ₃ . The solid was washed with deionized water, and the solid-liquid was separated and dried, and the solid ash B was retained.

The third step, adding digestion solution to the solid ash residue B obtained in the second step, the volume of acid added per 1g sample is 40g, and the digestion system is concentrated nitric acid, concentrated hydrochloric acid and hydrofluoric acid, and the volume ratio is 8:2:1 , digested with graphite digester, heated at 120 °C for 3 hours, 130 °C to drive acid, centrifuged at 3500 rpm for 2 minutes on a centrifuge, solid-liquid separation, tested the liquid, and measured X ₃ = the content of lead in other forms.

The fourth step is to weigh 0.05g of grate furnace waste incineration ash into the centrifuge tube, add a separating agent 3,3mol/L CH ₃ COOH solution into the centrifuge tube, ultrasonically extract for 55min, and the solid-liquid ratio is 1:40, Centrifuge at 3500 rpm for 2 min on the centrifuge to conduct solid-liquid separation, test the liquid, and measure the content of Y ₁ =PbCl ₂ +PbO+PbCO ₃ . The solid was washed with deionized water, filtered and dried, and the solid ash C was retained.

The fifth step, adding separating agent ₁ , 20mL 2mol/ _L Na2S2O3 solution to the solid ash C obtained in the fourth step, ultrasonic leaching for 10min, the solid-liquid ratio is 1:40, and the centrifuge is centrifuged at a rotating speed of 3500rpm. 2min, carry out solid-liquid separation, test the liquid, and measure the content of Y ₂ =PbSO ₄ . The solid was washed with deionized water, and the solid-liquid was separated and dried, and the solid ash D was retained.

The 6th step, add digestion solution to the solid ash D that obtains in the 5th step, the volume that every 1g sample adds acid is 40g, and the digestion system is concentrated nitric acid, concentrated hydrochloric acid and hydrofluoric acid, and the volume ratio is 8: 2: 1 , digested with graphite digester, heated at 120°C for 3h, 130°C to drive acid, constant volume, centrifuged at 3500rpm for 2min on a centrifuge, separated from solid and liquid, tested the liquid, measured Y ₃ = other forms of lead content.

The seventh step, calculate:

C(PbCl ₂ )=X ₁ -Y ₂ =Y ₁ -X ₂ ;

C(PbSO ₄ )=Y ₂ ;

C(PbO+PbCO ₃ )=X ₂ ;

C (other forms of lead) = X ₃ =Y ₃ .

Through this example 2, the lead content in the liquid obtained in each step is measured by atomic absorption spectrometer, and the content of PbCl in the coal-fired ash is 652.41 _mg /kg, the content of PbSO is _418.24 mg/kg, and the content of PbO+PbCO is _418.24 mg/kg. It is 175.88mg/kg, and the lead content of other forms is 120.46mg/kg.

Example 3

The first step is to weigh 1g of fluidized bed waste incineration ash into the centrifuge tube, add 1,1mol/L Na ₂ S ₂ O ₃ solution of the separating agent to the centrifuge tube, and shake and extract for 6h on the inversion shaker. 1:400, centrifuge at 3000 rpm for 4 min on the centrifuge, separate the solid from the liquid, test the liquid, and measure the content of X ₁ =PbCl ₂ +PbSO ₄ . The solid was washed with deionized water, filtered and dried, and the solid ash A was retained.

In the second step, separating agent 2, 1.5mol/L CH ₃ COONH ₄ buffer solution (pH=2.000) was added to the solid ash A obtained in the first step, and the leaching was shaken on a shaker for 15 hours, and the solid-liquid ratio was 1 : 400, centrifuge at 3000rpm for 4min on the centrifuge, separate the solid from the liquid, test the liquid, and measure the content of X ₂ =PbO+PbCO ₃ . The solid was washed with deionized water, and the solid-liquid was separated and dried, and the solid ash B was retained.

The third step, adding digestion solution to the solid ash residue B obtained in the second step, the volume of acid added per 1g sample is 400g, and the digestion system is concentrated nitric acid, concentrated hydrochloric acid and hydrofluoric acid, and the volume ratio is 9:1:1 , digest it with a graphite digester, heat it at 130°C for 2.5h, drive off the acid at 130°C, centrifuge it at 3500rpm for 4min on a centrifuge, separate the solid from the liquid, and test the liquid to find that X ₃ = the content of lead in other forms .

The fourth step is to weigh 1g of fluidized bed waste incineration ash into the centrifuge tube, add 3,2mol/L CH ₃ COOH solution of the separating agent to the centrifuge tube, and shake on an inversion shaker for 24h, and the solid-to-liquid ratio is 1: 1. 400, centrifuge at 3000 rpm for 4 min on the centrifuge, carry out solid-liquid separation, test the liquid, and measure the content of Y ₁ =PbCl ₂ +PbO+PbCO ₃ . The solid was washed with deionized water, filtered and dried, and the solid ash C was retained.

The fifth step, adding separating agent 1, 20mL 1mol/L Na ₂ S ₂ O ₃ solution to the solid ash C obtained in the fourth step, oscillating on an inversion shaker for 15h, the solid-liquid ratio is 1:400, and the centrifuge Centrifuge at 3000 rpm for 4 min to carry out solid-liquid separation, test the liquid, and measure the content of Y ₂ =PbSO ₄ . The solid was washed with deionized water, and the solid-liquid was separated and dried, and the solid ash D was retained.

The 6th step, add digestion solution to the solid ash residue D obtained in the 5th step, the volume that every 1g sample adds acid is 400g, and the digestion system is concentrated nitric acid, concentrated hydrochloric acid and hydrofluoric acid, and the volume ratio is 9: 1: 1 , digested with graphite digester, heated at 130°C for 2.5h, 130°C to drive acid, centrifuged at 3500rpm for 4min on a centrifuge, separated from solid and liquid, tested the liquid, and measured Y ₃ = the content of lead in other forms .

The seventh step, calculate:

C(PbCl ₂ )=X ₁ -Y ₂ =Y ₁ -X ₂ ;

C(PbSO ₄ )=Y ₂ ;

C(PbO+PbCO ₃ )=X ₂ ;

C (other forms of lead) = X ₃ =Y ₃ .

Through this example 3, the lead content in the liquid obtained in each step is measured by atomic absorption spectrometer, and it is obtained that the content of PbCl in the coal-fired ash is 528.41 _mg /kg, the content of PbSO ₄ is 308.36 mg/kg, and the content of PbO+PbCO ₃ It is 193.87mg/kg, and the lead content of other forms is 58.68mg/kg.

Example 4

The first step is to weigh 3g of biomass combustion ash into the centrifuge tube. Since the Ca/S in biomass combustion ash is low, add 0.02g CaO to the ash to adjust the Ca/S of the sample to 5.5, and then add 0.02g of Ca/S to the centrifuge. Add separating agent ₁ , 0.5mol/ _L Na2S2O3 solution into the tube, ultrasonically extract for 20min, the solid-liquid ratio is 1:100, centrifuge at 6000rpm for 10min on the centrifuge, separate the solid and liquid, and wash the solid with deionized water , filter, dry, retain the solid ash A. Because the lead content in the biomass combustion ash is too low, and the lead content in the liquid is difficult to detect, the ash A is carried out digestion test, and the lead content C in the ash A is measured ( Ash A)

The second step, repeating the first step, adding separating agent 2 to the solid ash A obtained in the first step, 1mol/LCH ₃ COONH ₄ buffer solution (pH=5.750), ultrasonic leaching for 40min, the solid-liquid ratio is 1: 100, centrifuge at 6000 rpm for 10 min on a centrifuge, separate the solid from the liquid, wash the solid with deionized water, filter and dry, and retain the ash residue B. Due to the low lead content in the coal ash slag, it is difficult to detect the lead content in the liquid. The ash slag B was digested and tested, and the lead content C (ash slag B) in the ash slag B was measured.

The third step is to digest the ash residue A retained in the first step, the B retained in the second step and the original ash residue. The volume of acid added per 1g of sample is 100g, the digestion system is concentrated nitric acid, concentrated hydrochloric acid and hydrofluoric acid, the volume ratio is 6:2:0, digested with a graphite digester, kept at 80 ° C for 2 hours, and 130 ° C to drive the acid 4h, set the volume, centrifuge at 6000rpm for 10min on the centrifuge, separate the solid and liquid, and test the liquid. The lead content C in the ash A (ash A) and the lead content in the ash B can be measured respectively. C (ash slag B), lead content in the original ash slag C (original ash slag).

The fourth step is to weigh 3g of biomass combustion ash into the centrifuge tube. Since the Ca/S in the biomass combustion ash is low, add 0.02g CaO to the ash to adjust the Ca/S of the sample to 5.5. Add separating agent 3, 0.2mol/LCH ₃ COOH, ultrasonic leaching for 110min, the solid-liquid ratio is 1:100, centrifuge at 6000rpm for 10min on the centrifuge, carry out solid-liquid separation, wash the solid with deionized water, filter , dry, retain ash C. Since the lead content in the coal ash is too low, it is difficult to detect the lead content in the liquid. The ash C was digested and tested, and the lead content C (ash C) in the ash C was measured.

The fifth step, repeat the fourth step, add separating agent 1, 0.5mol/L Na ₂ S ₂ O ₃ solution to the solid ash C obtained in the fourth step, ultrasonically extract for 20min, the solid-liquid ratio is 1:100, centrifuge. The machine was centrifuged at 6000 rpm for 10 min to carry out solid-liquid separation, and the liquid was tested to measure the content of Y ₂ =PbSO ₄ . The solid was washed with deionized water, filtered and dried, and the ash D was retained. Since the lead content in the coal ash is too low, it is difficult to detect the lead content in the liquid. The ash D was digested and tested, and the lead content C (ash B) in the ash D was measured.

The sixth step is to digest the ash residue C retained in the fourth step, the D retained in the fifth step and the original ash residue. The volume of acid added per 1g of sample is 100g, the digestion system is concentrated nitric acid, concentrated hydrochloric acid and hydrofluoric acid, the volume ratio is 6:2:0, digested with a graphite digester, kept at 80 ° C for 2 hours, and 130 ° C to drive the acid 4h, set the volume, centrifuge at 6000rpm for 10min on the centrifuge, separate the solid and liquid, and test the liquid. The lead content C in the ash C (ash C) and the lead content in the ash D can be measured respectively. C (ash slag D), lead content in the original ash slag C (original ash slag).

The seventh step, calculate:

X ₁ =C(raw ash)-C(ash A)

X ₂ =C(ash A)-C(ash B)

X ₃ =C (ash B)

Y ₁ =C(raw ash)-C(ash slag C)

Y ₂ =C(ash C)-C(ash D)

Y ₃ =C (ash D)

C(PbCl ₂ )=X ₁ -Y ₂ =Y ₁ -X ₂ ;

C(PbSO ₄ )=Y ₂ ;

C(PbO+PbCO ₃ )=X ₂ ;

C (other forms of lead) = X ₃ =Y ₃ .

Through this example 4, the lead content in the liquid obtained in each step is measured by atomic absorption spectrometer, and it is obtained that the content of PbCl in the coal ash is 17.54 mg/kg, the content of PbSO ₄ is 17.94 mg/kg, and the content of PbO+ _{PbCO 3} It is 5.42mg/kg, and the lead content of other forms is 2.67mg/kg.

Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, etc., All should be included within the protection scope of the present invention.

Claims (8)

1. The method for analyzing the form of lead in ash is characterized by comprising the following steps:

s1, adding Na into the original ash sample ₂ S ₂ O ₃ Leaching the solution,Centrifuging, separating solid from liquid, testing the obtained liquid to obtain X ₁ ＝PbCl ₂ +PbSO ₄ The content of (a); cleaning, filtering and drying the obtained solid to obtain ash A;

s2, adding CH into the ash A ₃ COONH ₄ Leaching, centrifuging and separating solid and liquid in the buffer solution, testing the obtained liquid to obtain X ₂ ＝PbO+PbCO ₃ The content of (A); washing, solid-liquid separating and drying the obtained solid to obtain ash B;

s3, adding digestion solution into the ash B for digestion, constant volume, centrifugation and solid-liquid separation, testing the obtained liquid, and measuring X ₃ The content of lead in other forms;

s4, adding CH into the original ash sample ₃ The COOH solution is leached, centrifuged and solid-liquid separated, and the obtained liquid is tested to obtain Y ₁ ＝PbCl ₂ +PbO+PbCO ₃ The content of (A); cleaning, filtering and drying the obtained solid to obtain ash C;

s5, adding Na into the ash C ₂ S ₂ O ₃ Leaching, centrifuging, separating solid and liquid, testing the obtained liquid to obtain Y ₂ ＝PbSO ₄ The content of (a); washing, solid-liquid separating and drying the obtained solid to obtain ash D;

s6, adding digestion solution into the ash D for digestion, centrifuging and solid-liquid separation, testing the obtained liquid, and measuring Y ₃ The content of lead in other forms;

s7, calculating the content of lead in each form, and analyzing the form of lead in the ash;

the raw ash sample is coal-fired ash, waste incineration ash or biomass combustion ash;

measuring the content of lead in the liquid obtained in each step by an atomic absorption spectrometer;

the solid-liquid ratio of the solid to the separating agent in the solid-liquid separation process is 1: 100-1: 400.

2. The method of claim 1, wherein CaO is added to the raw ash sample in step S4, and the Ca/S ratio of the raw ash sample is adjusted to 5.0 to 9.0.

3. The analysis method according to claim 1, wherein the content of each form of lead is calculated by:

C(PbCl ₂ )＝X ₁ -Y ₂ ＝Y ₁ -X ₂ ；

C(PbSO ₄ )＝Y ₂ ；

C(PbO+PbCO ₃ )＝X ₂ ；

c (other forms of lead) ═ X ₃ ＝Y ₃ 。

4. The assay of claim 1, wherein CH ₃ COONH ₄ The pH value of the buffer solution is CH ₃ COOH, pH value of 3.000-5.750, Na ₂ S ₂ O ₃ The concentration range of the solution is 0.2-2 mol/L; CH (CH) ₃ COONH ₄ CH in buffer solution ₃ COONH ₄ The concentration range is 0.1-3 mol/L; CH (CH) ₃ The concentration range of the COOH solution is 0.03-3 mol/L.

5. An assay method according to any one of claims 1 to 4 wherein the leaching process uses tumbling agitation, magneton agitation, ultrasound or microwave assisted leaching.

6. The method according to any one of claims 1 to 4, wherein the centrifugation is performed at a rotation speed in the range of 2000 to 6000rpm for a period of 2 to 10 min.

7. The analytical method according to any one of claims 1 to 4, wherein in the steps S3 and S6, the digestion system is mainly concentrated nitric acid, and concentrated hydrochloric acid, hydrofluoric acid or hydrogen peroxide is added to enhance the digestion process.

8. The assay of any one of claims 1 to 4, wherein the leaching in steps S1 and S5 is carried out at 10 to 30 ℃ in the absence of light and the leaching in steps S2 and S4 is carried out at 20 to 70 ℃.

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