Method for measuring high-temperature stability of hexavalent chromium reducing agent for cement
阅读说明：本技术 一种水泥用六价铬还原剂的高温稳定性能测定方法 (Method for measuring high-temperature stability of hexavalent chromium reducing agent for cement ) 是由 蔡洪 于 2019-11-07 设计创作，主要内容包括：一种水泥用六价铬还原剂的高温稳定性能测定方法,包括以下步骤：S1、测定室温下未掺六价铬还原剂的水泥样品中六价铬含量W<Sub>1</Sub>；S2,测定室温下掺还原剂的水泥样品中六价铬含量W<Sub>2</Sub>；S3,测定经高温烘干后的未掺杂六价铬还原剂的水泥样品中六价铬含量W<Sub>3</Sub>；S4,测定经高温烘干后的掺杂六价铬还原剂的水泥样品中六价铬含量W<Sub>4</Sub>；再通过设定公式计算得到六价铬的高温稳定性能。本发明操作简单,有利于操作人员选择性能良好的六价铬还原剂,确保对降低水泥中六价铬有含量,减少污染,提升操作的安全性和可靠性。(A method for measuring the high-temperature stability of a hexavalent chromium reducing agent for cement comprises the following steps: s1, determining the content W of hexavalent chromium in the cement sample which is not doped with the hexavalent chromium reducing agent at room temperature 1 (ii) a S2, determining the content W of hexavalent chromium in the cement sample doped with the reducing agent at room temperature 2 (ii) a S3, determining the content W of hexavalent chromium in the cement sample which is dried at high temperature and is not doped with the hexavalent chromium reducing agent 3 (ii) a S4, determining the content W of hexavalent chromium in the cement sample doped with the hexavalent chromium reducing agent after being dried at high temperature 4 (ii) a And calculating the high-temperature stability of the hexavalent chromium by a set formula. The method is simple to operate, is beneficial to operators to select the hexavalent chromium reducing agent with good performance, ensures that the content of hexavalent chromium in cement is reduced, reduces pollution, and improves the safety and reliability of operation.)
1. A method for measuring the high-temperature stability of a hexavalent chromium reducing agent for cement comprises the following steps:
s1, determining the content W of hexavalent chromium in the cement sample which is not doped with the hexavalent chromium reducing agent at room temperature1；
S2, determining the content W of hexavalent chromium in the cement sample doped with the reducing agent at room temperature2；
S3, determining the content W of hexavalent chromium in the cement sample which is dried at high temperature and is not doped with the hexavalent chromium reducing agent3；
S4, determining the content W of hexavalent chromium in the cement sample doped with the hexavalent chromium reducing agent after being dried at high temperature4；
S5, calculating the reduction effect of the hexavalent chromium content in the cement sample under the conditions of room temperature and high temperature according to the following formula:
in the above formula, R1For room temperature reduction effect, R2And calculating the high-temperature stabilizing effect of the hexavalent chromium reducing agent in the high-temperature environment for the high-temperature source recovery effect:
in the above formula, R3The effect of high temperature stabilization is achieved;
calculating the ratio of the reduction effect R2 of the hexavalent chromium at the high temperature to the reduction effect R1 of the hexavalent chromium at the room temperature, wherein the higher the numerical value is, the better the high-temperature stability of the hexavalent chromium reducing agent is, and the lower the numerical value is, the worse the high-temperature stability of the hexavalent chromium reducing agent is; when the numerical value is not more than 50, the high-temperature stability of the hexavalent chromium reducing agent is judged to be poor or invalid, and when the numerical value is more than 50, the high-temperature stability of the hexavalent chromium reducing agent is judged to be excellent, so that the hexavalent chromium reducing agents with different qualities can be distinguished conveniently.
2. The method for measuring the high-temperature stability of a hexavalent chromium reducing agent used for mud according to claim 1, wherein the steps S1 to S4 are performed by using the method of national standard GB31893 "method for measuring and limiting the amount of water-soluble chromium (VI) in cement" annex a "method for measuring and measuring the amount of water-soluble chromium (VI) in cement" dibenzoyl dihydrazide spectrophotometry ", and specifically comprises:
mixing and uniformly stirring a cement sample, standard sand and water to form cement mortar, wherein the dosage of the standard sand is three times that of the cement sample, and the dosage of the water is half of that of the cement sample;
filtering the cement mortar to obtain filtrate;
adding diphenylcarbazide into the filtrate, adjusting acidity and color development, measuring absorbance of the solution at 540nm, checking the concentration of hexavalent chromium in the solution on a working curve, and calculating the hexavalent chromium content according to the concentration of hexavalent chromium.
3. The method for measuring the high-temperature stability of the hexavalent chromium reducing agent for slime according to claim 1, wherein the step S1 is specifically performed by:
crushing a cement sample which is not doped with a hexavalent chromium reducing agent, filtering, and then placing for more than 4 hours;
repeatedly testing the hexavalent chromium content in the undoped cement sample at least twice, and taking the average value as the final content W1。
4. The method for measuring the high-temperature stability of the hexavalent chromium reducing agent for slime according to claim 3, wherein the step S2 specifically comprises:
doping hexavalent chromium reducing agents with the amount being less than or equal to 10ppm into a cement sample which is not doped with the hexavalent chromium reducing agents to form a cement sample doped with the hexavalent chromium reducing agents;
performing parallel detection for more than two times, and taking the average value to obtain the hexavalent chromium content W2。
5. The method for measuring the high-temperature stability of the hexavalent chromium reducing agent for slime according to claim 4, wherein the step S3 is specifically performed by:
putting a cement sample which is not doped with a hexavalent chromium reducing agent into a high-temperature drying box, drying the cement sample at the temperature of 50-200 ℃ for more than 8 hours, taking the cement sample out of the drying box, then placing the cement sample for more than 2 hours, then carrying out water-soluble hexavalent chromium content detection, repeatedly carrying out more than two times of parallel detection, and obtaining the corresponding hexavalent chromium content W by taking the average value3。
6. The method for measuring the high-temperature stability of the hexavalent chromium reducing agent for slime according to claim 5, wherein the step S4 is specifically performed by:
putting the cement sample doped with the hexavalent chromium reducing agent into a high-temperature drying oven at 50 DEG CDrying at-200 deg.C for more than 8 hr, taking out from the oven, standing for more than 4 hr, detecting the content of water-soluble hexavalent chromium, repeating the parallel detection for more than two times, and averaging to obtain the corresponding content W4。
7. The method for measuring the high-temperature stability of a hexavalent chromium reducing agent for slime according to claim 6, wherein the cement samples used are products of the same batch, and the tests are completed within the same time period and cannot be measured in a time-span manner.
Technical Field
The invention relates to a method for detecting an additive for cement, in particular to a method for measuring the high-temperature stability of a hexavalent chromium reducing agent for cement.
Background
It is estimated that there are 80 different industries that may be exposed to hexavalent chromium. Various hexavalent chromium compounds are respectively applied to industries such as cement, leather making, textile production, printing and dyeing, pigment, chromium plating and the like. Hexavalent chromium has high water solubility and strong permeability, and can easily permeate into human tissues to cause diseases such as dermatitis, fester and the like. After the hexavalent chromium in the concrete which is drenched or soaked for a long time is dissolved out, the hexavalent chromium is brought into a reservoir or is infiltrated underground to cause chromium pollution of a drinking water source.
The cement industry is a high-pollution, high-energy-consumption and high-consumption three-high industry, wherein hexavalent chromium is mainly brought in the clinker manufacturing process, in order to reduce the harm of the hexavalent chromium to human bodies, an 2003/53/EC instruction is issued by the European Union, and the hexavalent chromium in the cement is regulated to be not more than 2.0 mg/kg. The method is published in 2016, 10 months and 1 day in China in GB 31893-2015 limit and determination method for water-soluble chromium (VI) in cement, and the content of hexavalent chromium in the cement cannot exceed 10 mg/kg.
In the cement production process, the cement grinding and storage processes are all carried out at high temperature due to the temperature brought by clinker, the heat generated by grinding, weather and the like. At present, a method for treating soluble hexavalent chromium in cement abroad is to use a certain amount of hexavalent chromium reducing agent (hereinafter referred to as reducing agent) to reduce the soluble hexavalent chromium in the cement to trivalent chromium, but the reducing agent does not resist high temperature and loses due effect in a high-temperature environment. Therefore, in the actual cement production, the addition amount of the reducing agent basically exceeds the reference addition amount, and the soluble hexavalent chromium in the cement can be ensured to be reduced to trivalent chromium. Excessive use causes an increase in cost. Therefore, in evaluating the reducing effect of the hexavalent chromium reducing agent for cement, the stability of the hexavalent chromium reducing agent at high temperature should be considered.
Disclosure of Invention
In order to solve the technical problems, the invention provides a method for measuring the high-temperature stability of a hexavalent chromium reducing agent for cement.
In order to solve the technical problems, the invention adopts the following technical scheme:
a method for measuring the high-temperature stability of a hexavalent chromium reducing agent for cement comprises the following steps:
s1, determining the content W of hexavalent chromium in the cement sample which is not doped with the hexavalent chromium reducing agent at room temperature1；
S2, determining the content W of hexavalent chromium in the cement sample doped with the reducing agent at room temperature2；
S3, determining the content W of hexavalent chromium in the cement sample which is dried at high temperature and is not doped with the hexavalent chromium reducing agent3；
S4, determining the reduction of the doped hexavalent chromium after high-temperature dryingHexavalent chromium content W in cement samples of the agent4；
S5, calculating the reduction effect of the hexavalent chromium content in the cement sample under the conditions of room temperature and high temperature according to the following formula:
（1）
in the above formula, R1For room temperature reduction effect, R2And calculating the high-temperature stabilizing effect of the hexavalent chromium reducing agent in the high-temperature environment for the high-temperature source recovery effect:
in the above formula, R3The effect of high temperature stabilization is achieved;
calculating the ratio of the reduction effect R2 of the hexavalent chromium at the high temperature to the reduction effect R1 of the hexavalent chromium at the room temperature, wherein the higher the numerical value is, the better the high-temperature stability of the hexavalent chromium reducing agent is, and the lower the numerical value is, the worse the high-temperature stability of the hexavalent chromium reducing agent is; when the numerical value is not more than 50, the high-temperature stability of the hexavalent chromium reducing agent is judged to be poor or invalid, and when the numerical value is more than 50, the high-temperature stability of the hexavalent chromium reducing agent is judged to be excellent, so that the hexavalent chromium reducing agents with different qualities can be distinguished conveniently.
In the steps S1-S4, the determination of the content of the hexavalent chromium reducing agent in the cement sample is performed by using a method of national standard GB31893 "limit and determination method of water-soluble chromium (VI) in cement" appendix a "determination method of water-soluble chromium (VI) in cement" dibenzoyl dihydrazide spectrophotometry ", which specifically comprises the following steps:
mixing and uniformly stirring a cement sample, standard sand and water to form cement mortar, wherein the dosage of the standard sand is three times that of the cement sample, and the dosage of the water is half of that of the cement sample;
filtering the cement mortar to obtain filtrate;
adding diphenylcarbazide into the filtrate, adjusting acidity and color development, measuring absorbance of the solution at 540nm, checking the concentration of hexavalent chromium in the solution on a working curve, and calculating the hexavalent chromium content according to the concentration of hexavalent chromium.
The step S1 specifically includes:
crushing a cement sample which is not doped with a hexavalent chromium reducing agent, filtering, and then placing for more than 4 hours;
repeatedly testing the hexavalent chromium content in the undoped cement sample at least twice, and taking the average value as the final content W1。
The step S2 specifically includes:
doping hexavalent chromium reducing agents with the amount being less than or equal to 10ppm into a cement sample which is not doped with the hexavalent chromium reducing agents to form a cement sample doped with the hexavalent chromium reducing agents;
performing parallel detection for more than two times, and taking the average value to obtain the hexavalent chromium content W2。
The step S3 specifically includes:
putting a cement sample which is not doped with a hexavalent chromium reducing agent into a high-temperature drying box, drying the cement sample at the temperature of 50-200 ℃ for more than 8 hours, taking the cement sample out of the drying box, then placing the cement sample for more than 2 hours, then carrying out water-soluble hexavalent chromium content detection, repeatedly carrying out more than two times of parallel detection, and obtaining the corresponding hexavalent chromium content W by taking the average value3。
The step S4 specifically includes:
putting a cement sample doped with a hexavalent chromium reducing agent into a high-temperature drying box, drying for more than 8 hours at the temperature of 50-200 ℃, taking out the cement sample from the drying box, then placing for more than 4 hours, then carrying out water-soluble hexavalent chromium content detection, repeatedly carrying out more than two times of parallel detection, and obtaining the corresponding hexavalent chromium content W by taking the average value4。
The cement samples used were products of the same batch and the tests were completed in the same time period and could not be measured over time.
The method is simple to operate, is beneficial to operators to select the hexavalent chromium reducing agent with good performance, ensures that the content of hexavalent chromium in cement is reduced, reduces pollution, and improves the safety and reliability of operation. The method is beneficial to optimizing the product formula of the hexavalent chromium reducing agent by a supplier and establishing the evaluation method of the hexavalent chromium reducing agent by a demander, so that the produced cement product meets the requirement of the limit value of hexavalent chromium in the national standard GB 31893.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments in order to further understand the features and technical means of the invention and achieve specific objects and functions.
A method for measuring the high-temperature stability of a hexavalent chromium reducing agent for cement comprises the following steps:
s1, determining the content W of hexavalent chromium in the cement sample which is not doped with the hexavalent chromium reducing agent at room temperature1；
S2, determining the content W of hexavalent chromium in the cement sample doped with the reducing agent at room temperature2；
S3, determining the content W of hexavalent chromium in the cement sample which is dried at high temperature and is not doped with the hexavalent chromium reducing agent3；
S4, determining the content W of hexavalent chromium in the cement sample doped with the hexavalent chromium reducing agent after being dried at high temperature4；
S5, calculating the reduction effect of the hexavalent chromium content in the cement sample under the conditions of room temperature and high temperature according to the following formula:
（2）
in the above formula, R1For room temperature reduction effect, R2And calculating the high-temperature stabilizing effect of the hexavalent chromium reducing agent in the high-temperature environment for the high-temperature source recovery effect:
in the above formula, R3The effect of high temperature stabilization is achieved;
calculating the ratio of the reduction effect R2 of the hexavalent chromium at the high temperature to the reduction effect R1 of the hexavalent chromium at the room temperature, wherein the higher the numerical value is, the better the high-temperature stability of the hexavalent chromium reducing agent is, and the lower the numerical value is, the worse the high-temperature stability of the hexavalent chromium reducing agent is; when the numerical value is not more than 50, the high-temperature stability of the hexavalent chromium reducing agent is judged to be poor or invalid, and when the numerical value is more than 50, the high-temperature stability of the hexavalent chromium reducing agent is judged to be excellent, so that the hexavalent chromium reducing agents with different qualities can be distinguished conveniently.
In the steps S1-S4, the determination of the content of the hexavalent chromium reducing agent in the cement sample is performed by using a method of national standard GB31893 "limit and determination method of water-soluble chromium (VI) in cement" appendix a "determination method of water-soluble chromium (VI) in cement" dibenzoyl dihydrazide spectrophotometry ", which specifically comprises the following steps:
mixing and uniformly stirring a cement sample, standard sand and water to form cement mortar, wherein the dosage of the standard sand is three times that of the cement sample, and the dosage of the water is half of that of the cement sample;
filtering the cement mortar to obtain filtrate;
drawing a working curve, respectively putting 1.00mL, 2.00mL, 5.00mL, 10.00mL and 15.00mL chromium standard solutions into a 50mL volumetric flask, respectively adding 5.00mL diphenylcarbodihydrazide solution and 5mL hydrochloric acid, diluting with water to a marked line, and shaking up. The solution contained 0.1mg, 0.2mg, 0.5mg, 1.0mg, 1.5mg hexavalent chromium per liter, respectively. After standing for 15-30min, the absorbance of the solution was measured at 540nm using a spectrophotometer photoelectric colorimeter (A.4.3), 10mm cuvette, and the absorbance of the blank was subtracted. And drawing a working curve according to the absorbance corresponding to different hexavalent chromium concentrations.
Within 8h after filtration, 5.00mL of the filtrate was aspirated into a 100mL beaker. 5.00mL of diphenylcarbodihydrazide solution and 20mL of water are added, then the solution is shaken, and immediately the pH value is adjusted to be between 2.1 and 2.5 by hydrochloric acid under the indication of a pH meter. According to different contents of water-soluble hexavalent chromium in the cement, selecting a proper volumetric flask, transferring the solution into the volumetric flask, diluting the solution with water to the marked line, and shaking up the solution. After standing for about 30 minutes, the absorbance of the solution was measured at 540nm using a spectrophotometer, photoelectric colorimeter, 10mm cuvette, and the absorbance of the blank was subtracted. Finding out the concentration of the water-soluble hexavalent chromium on the working curve, wherein the unit is mg/L.
And finally, calculating a result. The content W of water-soluble hexavalent chromium in the cement is expressed in mg/kg and is calculated by the following formula:
wherein W is the content of water-soluble hexavalent chromium in the cement, and the unit of milligram per kilogram; c is the concentration of the water-soluble hexavalent chromium obtained from the working curve, and the unit is milligram per liter; v1 is the volume of water in the mortar, and the unit is milliliter; v2 is the volume of filtrate in milliliters; v3 is the volume of the volumetric flask in ml; 450 refers to the mass of cement in the mortar in grams. Wherein the content of the first and second substances,
The above-mentioned method is a known measurement method, and steps S1 to S4 in the present application are all used for measuring the hexavalent chromium content in the cement sample.
The following is a description of specific examples.
The name and specification of the used equipment are
1) High-temperature air blast drying oven: 1 SUS304 model, temperature control range RT + 10-300 ℃, 2) the temperature control precision of the high-temperature blast drying box is 0.1 ℃, the temperature fluctuation is +/-1 ℃, and the timing range is 0-9999 min.
3) Stainless steel utensils: 12 pieces of SUS304 with diameter of 150 mm.
4) A thermometer: 2, the measuring ranges are 0-100 ℃ and 0-200 ℃ respectively.
5) Analytical balance: 1, the measuring range is 0-200 g, and the accuracy is 0.1 mg.
6) Other devices: please refer to the equipment in GB 31893-.