As an excellent physical and chemical adsorbent, activated carbon has attracted more and more attention. With the increase in the use of activated carbon, there are more and more methods for detecting activated carbon. However, different detection methods may produce different performance indicators. It brings difficulties to the exchange of information between the activated carbon industry, and also brings certain losses to the export of activated carbon. This urgently requires activated carbon experts and authoritative machinery to develop a more complete and standardized method for detecting activated carbon, so that the activated carbon industry can be regulated.
1 Introduction
Activated carbon is made of charcoal, various kinds of husks and high-quality coal as raw materials. It is made of a series of processes such as sieving, activation, carbonization, drying and screening. The appearance is black, the internal pore structure is developed, and the specific surface area is large. A type of microcrystalline carbon material with strong adsorption capacity. It is an adsorbent, catalyst or catalyst carrier. It has the twin characteristics of physical adsorption and chemical adsorption. It can selectively adsorb various substances in the gas phase and liquid phase to achieve decolorization, refining, disinfection, deodorization and decontamination. The purpose of purification. Mainly used in sugar, medicine, monosodium glutamate industry, water treatment, solvent recovery, food and beverage purification, air purification, desulfurization, carrier, medicine, gold refining, gas mask, anti-virus clothing, semiconductor field and so on.
Since the establishment of the activated carbon industry in the 20th century, it now has more than 300 various activated carbon manufacturers. The annual production capacity has exceeded 200,000 tons. China has a variety of abundant coal resources and rich wood and nutshell resources, which provide a certain material basis for the production of activated carbon. With the increase in the use of activated carbon, the scope of application has expanded, and the types of activated carbon have become more and more. The evaluation of a kind of activated carbon mainly depends on its performance indicators, but the current problem is that the detection method of activated carbon is not uniform. This has greatly increased our evaluation workload. Because different detection methods may produce different performance indicators, and lack an authoritative promotion mechanism. This requires us to perform a variety of methods for the same activated carbon, so that the utilization of the test data is not high, and the detection cost of activated carbon is increased. At the same time, it has brought difficulties to the exchange of information between enterprises in the industry.
2 Current status of activated carbon detection methods
2.1 The detection method of activated carbon is not uniform
The world's largest producer of activated carbon is the United States, followed by China, Russia, and Japan. In countries with large output in recent years, they generally use their own testing methods. Because of the differences in detection methods, the measured data is different.
Taking the most basic iodine value of activated carbon as an example, the determination of iodine value has been a routine test project in China for many years. There are three main methods of measurement, JISK1474-1991 and GB/T7702-1997. Although both are iodine values, the results are different because of the different ratios of iodine and potassium iodide. Below we will use the three methods to test the same activated carbon, the measured data is as follows:
method
Carbon sample iodine adsorption value
Type mg/g ASTM4607-1994 JISK1474-1991 GB/T7702-1997
8×35 1047 1012 973
Broken charcoal 1041 1029 967
D×30 951 910 876
PJ4×8 918 930 837
ZJ15 840 826 791
Powdered charcoal 871 827 775
Through this experiment, we can see that the iodine adsorption value of activated carbon is also measured. It is only because of the different measurement methods used, and different iodine value indexes are generated for the same activated carbon. From the experiment, we can see that the iodine value measured by the US standard is higher, followed by Japan, and our standard method has the lowest measured value. To this end, we can not put aside the detection method, but only evaluate the quality of activated carbon based on the performance index of activated carbon. From this we can also see the importance of the determination method. However, as far as the current situation is concerned, China's domestic activated carbon detection methods are still confusing. Due to the different detection methods, the performance indicators of activated carbon provided by enterprises are not comparable. It has brought difficulties to the exchange of information between enterprises in this industry, and it has also caused problems for customers in their choices.
2.2 The detection method of activated carbon is not perfect
For the current testing projects in various countries, most of them are tests for conventional activated carbon projects. For example, the iodine adsorption value, moisture, ash, and particle size distribution of activated carbon mainly measured in the United States are mainly based on the powder and granular activated carbon standards of the American Water Works Association, and the latest activated carbon standards and test methods of ASTM. Japan mainly measures the methylene blue decolorization power, sulfonate adsorption value, pH value, drying loss, total iron salt, ignition residue, chloride, specific conductivity, phenol value, ABS value, arsenic, lead, cadmium, particle size of 200 mesh of activated carbon. By the way, the main basis is the Japanese industrial standard?? Activated carbon detection method. Russia mainly measures the apparent density, moisture, ash and pH of activated carbon, mainly based on the latest activated carbon in Russia and its testing methods. China mainly measures the decolorization power, iodine adsorption value, drying, reduction, pH value, total iron salt, chloride, etc. of activated carbon, based on the national standard and enterprise standard of activated carbon. With the rapid development of industries in various countries, the application range of activated carbon is expanding, and the use of activated carbon is increasing day by day. Activated carbon is widely used in almost all industrial sectors, especially in food, pharmaceutical, environmental protection, agriculture, national defense, and other sectors. Applications. Activated carbon companies in various countries are constantly developing new products and expanding market capacity. With the increasing application range of activated carbon, the detection range of activated carbon is also expanding. Conventional projects can no longer meet the requirements of customers. For example, there are requirements for soluble organic matter, humic acid and metal content of activated carbon. Especially in the field of application of activated carbon, people have also put forward new requirements, such as pure medium pressure loss, different water temperature expansion curves.
2.3 Lack of dedicated testing equipment
As a pillar of the national economy, activated carbon plays an increasingly important role in modern society, and special equipment for activated carbon detection is still lacking. Most of the testing equipment is processed by the testing manufacturer according to the experimental needs, such as specific surface area measuring instrument, particle size meter and so on. Most of them lack uniform standards, which makes the detection data sometimes have errors, which brings a lot of inconvenience to the detection.
3 Development of activated carbon detection methods
Activated carbon itself has a strong selective adsorption, and it can also be used as a carrier. Therefore, people's research on activated carbon is getting deeper and deeper, and there are more and more kinds of substances, and detection methods are also emerging. In particular, in recent years, environmental pollution has been increasingly on the agenda, and the environmental protection industry is booming. Due to its superior adsorption performance and its reproducibility, activated carbon is used to treat nitrogen and sulfur in electric field flue gas in Japanese power plants. This requires us to test the desulfurization and denitrification capacity of such activated carbon. The detection method of this indicator, but this detection method is still very few in the standard, and most of them are self-made detection methods.
In summary, China's continued strong economic growth, accession to the WTO and the reorganization of state-owned assets will bring new opportunities for reform of the activated carbon industry. However, China's activated carbon industry is facing challenges in both domestic and international markets. The domestic market will require the activated carbon industry to continuously improve quality, increase varieties, and reduce costs; the international market is facing fierce competition in the sale of activated carbon. This requires us to strictly control the quality of products, and the quality of products is fundamental to the survival of enterprises. The quality of the product must be based on the test method of the product. At present, many detection methods of activated carbon are difficult to collect. This urgently requires activated carbon experts and authoritative organizations to develop a more complete and standardized method for detecting activated carbon. Secondly, a large number of people with lofty ideals are required to study various methods at home and abroad in order to find out the differences between the methods. At the same time, it is necessary to have a formal instrument factory to process and manufacture its instruments. Therefore, the activated carbon industry can be regulated, and the information exchange between the domestic activated carbon industry can be enhanced. At the same time, on the basis of eliminating tariff barriers, technical barriers in international trade can be eliminated and reduced, so that Chinese activated carbon products can participate in the global market competition. Play a bigger role in the international arena.
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