AIGC:

Label: "1"

ContentProducer: 001191440300708461136T1XGW3

ProduceID: 42c3c8caeb8ff4e0cedb4763052404ad_191268a0925a01c902ccce9fe83aba07

ReservedCode1: o4uP4/wM+UadhHk5jfnHBavTd5flU8Y0r0VKdaoVGdIea+9gVqty7Bar60qx9WF/knZWEQKw42UjcYeW7slK+1z4QM5xD0OPVlY4mFHmNQg=

ContentPropagator: 001191440300708461136T1XGW3

PropagateID: 42c3c8caeb8ff4e0cedb4763052404ad_191268a0925a01c902ccce9fe83aba07

ReservedCode2: o4uP4/wM+UadhHk5jfnHBavTd5flU8Y0r0VKdaoVGdIea+9gVqty7Bar60qx9WF/knZWEQKw42UjcYeW7slK+1z4QM5xD0OPVlY4mFHmNQg=

The acid value detection of molybdenum disulfide (MoS₂) powder is an important quality control step for assessing the chemical cleanliness of the product. The acid value, expressed as the milligrams of potassium hydroxide (mg KOH/g) needed to neutralize the acidic substances in a unit mass of sample, directly reflects the level of residual acidic components on the powder surface and in processes such as flotation and purification. If the acid value is too high, it not only indicates possible deviations in the washing and neutralization steps of the process, but may also accelerate the oxidation of base oils and cause corrosion of metal surfaces in downstream applications such as greases and coatings, thereby weakening the friction-reducing and anti-corrosion performance of the product. Therefore, incorporating acid value into routine ex-factory inspection and batch management has become a common requirement for quality control and acceptance between suppliers and customers. This article starts from the process significance of acid value, systematically introducing the detection principle, standard basis, and quality control points centered on the titration method.

Significance of Acid Value Detection in MoS2 Quality Control

The acid value of MoS₂ products is closely related to raw material sources, beneficiation methods, and the degree of washing and neutralization. For molybdenum disulfide obtained by physical flotation, if washing is insufficient or neutralization is incomplete, trace acidic components from the ore pulp may remain in the powder; during storage, these acidic substances gradually migrate to the particle surface and affect the chemical stability of the powder. On the downstream application side, residual acids promote the decomposition of base oils and soap thickeners in greases, accelerate pitting corrosion of metal parts, and may also affect the pH stability of coating systems. Quantitative monitoring of the acid value provides data support for process optimization and controls potential risks before shipment, serving as an important bridge between production and end-product quality.

Basic Principle of Acid Value Determination by Titration

Acid value determination is based on the acid-base neutralization reaction and belongs to typical titration analysis. During measurement, the sample is dispersed or leached in an appropriate way and dissolved in a mixed solvent such as ethanol-ether, then titrated with a standard potassium hydroxide (KOH) solution of known concentration. The endpoint is judged either by indicator color change or by a potential jump, and the acid value is calculated from the volume of standard solution consumed and the sample mass. Depending on the endpoint detection method, titration can be divided into the color-indicator method and the potentiometric titration method. The color-indicator method is intuitive and low-cost, suitable for light-colored samples; the potentiometric titration method determines the endpoint from the potential change curve formed by glass and reference electrodes, avoiding interference from turbidity and color, and is more suitable for dark-colored sample systems or those with more interference.

Determination Methods and Standard Basis

At the methodological level, GB/T 23274-2009 Molybdenum Disulfide - Methods for Chemical Analysis provides a systematic operational framework for the determination of various indicators of molybdenum disulfide, and chemical indicators such as acid value can be tested under this standard system. For the acid value itself, GB/T 7304-2014 Petroleum Products - Determination of Acid Number - Potentiometric Titration Method specifies the detailed procedure for acid value determination by potentiometric titration and is a common basis for acid value testing of lubricants and related industrial products. At the international level, ASTM D664 provides a comparable specification for the potentiometric titration determination of acid number of petroleum products, while ISO 6618 specifies the operational requirements for the color-indicator titration method for acid value determination. These are mutually corroborated in principle with the Chinese standards, facilitating inter-laboratory and international comparison of test results. In practice, the appropriate method should be chosen according to sample characteristics, and consistency of the method should be maintained.

Sample Pretreatment and Quality Control

The reliability of acid value results depends heavily on sample pretreatment and full-process quality control. Sampling should follow the principle of representativeness: the sample should be fully mixed and repeatedly reduced to obtain a uniform specimen, and kept in a clean sealed container to avoid contamination. Solvents and reagents should be of analytical grade and periodically checked; the KOH standard solution should be standardized as required and its concentration stability verified. During analysis, parallel determinations should be carried out with controlled relative deviation, blank tests should be set up to subtract interference introduced by solvents and vessels, and quality control samples with known acid value should be used regularly to verify the accuracy of the method. The influence of ambient temperature and humidity on the titration endpoint should also be monitored. For abnormal results, the sources of error in sampling, leaching, and titration should be analyzed, and repeated determination should be performed if necessary to confirm reliability, ensuring that the inspection data are truthful and dependable.

Conclusion

The acid value is an important technical indicator for evaluating the chemical cleanliness of molybdenum disulfide, and the titration method, with its mature principle, standardized operation, and reliable results, has become the mainstream approach for acid value determination. Based on the methodological framework established by GB/T 23274-2009, combined with the potentiometric titration method of GB/T 7304-2014 and domestic and international standards such as ASTM D664 and ISO 6618, accurate determination and effective control of acid value can be achieved. Through standardized sampling, rigorous pretreatment, and continuous quality control, the stability and reliability of molybdenum disulfide products in lubrication, friction materials, and other applications can be ensured from the source.