活性炭基础知识

Basic knowledge of activated carbon

1. 活性炭分类－由于原料来源、制造方法、外观形状和应用场合不同,活性炭品种不下千种。 

1.1 按原料来源分，可分为木质活性炭(如椰壳活性炭、杏壳活性炭、木质粉炭等)、 矿物质原料活性炭(各种煤和石油及其加工产物为原料制成的活性炭)、其它原料制成的活性炭(如废橡胶、废塑料等制成的活性炭)。

1.2 按制造方法分，可分为化学法活性炭(化学炭)

      将含碳原料与某些化学药品混合后进行热处理，制取活性炭的方法叫化学法。用化学法生产的活性炭又称为化学法活性炭或化学炭。

      可以作为化学法的化学药品又称作活化剂，活化剂有氯化锌、氯化钙、碳酸钾、磷酸、磷酸二氢钾、硫化钾、硫酸、氢氧化钾、氢氧化钠、硼酸等，总之许多酸、碱、盐都可以用作活化剂，主要从活性炭的性能和经济性来考虑采用何种活化剂。

      一般说来，化学炭的孔隙中次微孔、中孔（即孔直径或孔宽大于1.5纳米的孔隙）较发达，主要用于液相吸附精制和溶剂回收的气相（蒸汽）吸附场合。 

      化学法制造活性炭由于加入了化学药品在制造过程中应当极其重视环境保护以及产品中可能存在微量非原料带入的元素的影响问题。

 1.2.2 物理法活性炭

      以炭为原料用水蒸汽、二氧化碳、空气（主要是氧）或它们的混合物（烟道气）为活化介质，在高温下（600～1000℃）进行活化制取活性炭的方法叫物理法。物理法制造的活性炭叫物理法活性炭，也称作物理炭。一般说来物理炭的微孔（孔直径或孔宽小于1.5纳米的孔隙）发达，主要用于气相吸附场合或小分子液相吸附场合。

1.2.3 化学--物理法或物理--化学法活性炭

      在了解化学炭和物理炭的同时，还应当提及化学--物理法或物理--化学法活性炭。选用不同的原料和采用不同的化学法与物理法的组合可以对活性炭的孔隙结构进行调控，从而制取许多性能不同的活性炭。这种化学--物理法或物理--化学法是许多年来及今后相当长时期内世界各国活性炭工作者非常关注的活性炭制取方法。

1.3 按外观形状分

     1.3.1 粉状活性炭

      一般将90%以上通过80目标准筛或粒度小于0.175mm的活性炭通称粉状活性炭或粉状炭。粉状炭在使用时有吸附速度较快，吸附能力使用充分等优点，但需专有的分离方法。随着分离技术的进步和某些应用要求的出现，粉状炭的粒度有越来越细化的倾向，有的场合已达到微米甚至纳米级。 

      1.3.2 颗粒活性炭

      通常把粒度大于0.175mm的活性炭称作颗粒活性炭。

      颗料活性炭又分为下列几种。

      1.3.2.1 不定型颗料活性炭

      不定型颗料活性炭一般由颗料状原料经炭化、活化，然后破碎筛分至需要粒度制成，也可以用粉状活性炭加入适当的粘结剂经适当加工而成。

      1.3.2.2 园柱形活性炭

      园柱形活性炭又称柱状炭，一般由粉状原料和粘结剂经混捏、挤压成型再经炭化、活化等工序制成。也可以用粉状活性炭加粘结剂挤压成型。柱状炭又有实心和中空之分，中空柱状炭是柱状炭内有人造的一个或若干个有规则的小孔。

      1.3.2.3 球形活性炭

      球形活性炭故名思义是园球形的活性炭，它的制取方法与柱状炭类似，但有成球过程。也可以用液态含碳原料经喷雾造粒、氧化、炭化、活化制成，还可以用粉状活性炭加粘结剂成球加工而成。球形活性炭也有实心和空心球形活性炭之分。

      1.3.3 其它形状的活性炭

      除了粉状活性炭和颗粒活性炭两大类外，还有其他形状的，如活性炭纤维、活性炭纤维毯、活性炭布、蜂窝状活性炭、活性炭板等等。

      1.4 按应用场合分

      前已述及活性炭广泛应用于几乎所有国民经济部门和人们的日常生活，正因为如此，按活性炭应用场合进行分类是很困难的，问题在于同一种活性炭可以应用于多种场合，而某种场合又可以用多种活性炭达到相同的目的。人们往往是由应用来获得对活性炭的认识的，所以往往在活性炭词语前冠似×××活性炭也作为的定俗成的活性炭的模糊分类方法。如糖用活性炭、针剂活性炭、味精活性炭、净水活性炭等等。

      活性炭由于具有吸附、催化和一定的化学反应性能，同时又具有物理、化学的相对稳定性。广泛应用于几乎所有国民经济部门和人们的目常生活。

      3.1 活性炭在气（汽）相吸附中的应用

      活性炭在气（汽）相吸附中的大规模应用是从第一次世界大战中的毒气防护开始的。此后，逐渐向其他领域扩展，归纳起来其主要应用如下。

      3.1.1 有毒或有害气体的防护

      防毒面具、口罩和防护服是活性炭应用的典型代表。

      3.1.2 气（汽）体的净化、精制和分离

      空气净化、空气的氮、氧吸附分离和纯化；工业氢的度压吸附分离和提纯；溶剂回收；烟气中去除二氧化硫和氮氧化合物；空调；航天和深海潜艇的工作环境的气体净化等部离不开活性炭。

      3.2 活性炭在液相吸附中的应用

      活性炭最早的应用是从欧洲人精制糖液开始的。现在活性炭在液相吸附中的应用乙遍及许多工业部门和人们的日常生活。

      3.2.1 食品工业中的应用

      所有甜味剂、调味品、食用油脂、饮料都使用活性炭进行脱色精制。到目前为止，这方面的应用仍然是活性炭最广阔的市场之一，特别是正在实现工业化的我国和许多发展中国家。

      3.2.2 制药工业中的应用

      所有人工合面和生物制药的原料药，尤其是西药都采用活性炭进行脱色精制。活性炭吸附的主要作用是去除杂质、提高纯度和去除致热源。这是活性炭又一广大市场之一。

      3.2.3 活性炭在化学工业和其他工业中的应用

      活性炭在石化工业中的油品精制、脱硫、脱臭、催化剂载体；无机化工中的含用和医药级制品的精制提纯；治金工业中特别是湿法冶金中的金、铂等贵金属的提取以及染织工业中的染料、媒染剂等都逐渐使用活性炭，是近几十年来活性炭新开发的市场。

      3．3 活性炭在环境保护中的应用

      活性炭的应用中，从上世纪六、七十年代起环境保护逐渐成为活性炭最大的消费领域，包括气、液相吸附的环保用活性炭往往占发达国家总用量的60%以上。环保中的气相处理是各种工业生活废气的净化和回收有用溶剂。环保中的液相汲附处理中主要用于人们生活的上、下水和工业废水的处理上。发达国家的人们的饮用水、城市生活废水、工业废水基本上都采用包括活性炭处理在内的三级净化，发达国家用于水处理的活性炭约占其总用量的40～50%。我国开始重视环境问题，预期不远将来，活性炭在我国水处理中将获得跃式的发展。

      3.4 活性炭在高新技术领域中的应用进展

      近二十年来高新技术已成国世界各国经济发展的竞技物。科技的迅速发展促进了活性炭的发高比表面、高孔容、高吸附容量的高性能活性炭、超细活性炭、活性炭各种各样的制品不断涌现。而这些活性炭新品系在高新电子电极、新型催化剂截体、电能和高能量密度物质（如压缩或液化氢气、天然气等）和贮存。电动汽车、功能性绿色环保等诸多领域的应用都屡见有关文献，不少已投放市场。我国的活性炭工作者也在不懈努力，有些方面已取得突破，可以预期在新世纪里我国活性炭在高新技术领域将占有一席之地。

1. Classification of Activated Carbon - Due to differences in raw material sources, manufacturing methods, appearance forms, and application scenarios, there are no fewer than a thousand types of activated carbon.   1.1 Classified by Raw Material Source   They can be divided into wood-based activated carbon (such as coconut shell activated carbon, apricot shell activated carbon, wood powder carbon, etc.), mineral raw material activated carbon (activated carbon made from various coals, petroleum and their processed products as raw materials), and activated carbon made from other raw materials (such as activated carbon made from waste rubber, waste plastics, etc.).   1.2 Classified by Manufacturing Method   1.2.1 Chemical Method Activated Carbon (Chemical Carbon)   The method of preparing activated carbon by mixing carbon-containing raw materials with certain chemicals and then performing heat treatment is called the chemical method. Activated carbon produced by the chemical method is also known as chemical method activated carbon or chemical carbon.   Chemicals that can be used in the chemical method are also called activators. Activators include zinc chloride, calcium chloride, potassium carbonate, phosphoric acid, potassium dihydrogen phosphate, potassium sulfide, sulfuric acid, potassium hydroxide, sodium hydroxide, boric acid, etc. In short, many acids, alkalis, and salts can be used as activators, and the choice of which activator to use mainly depends on the performance and economy of the activated carbon.   Generally speaking, the mesopores and macropores (pores with a diameter or width greater than 1.5 nanometers) in the pores of chemical carbon are well-developed, and they are mainly used in liquid-phase adsorption refining and gas-phase (vapor) adsorption occasions for solvent recovery.   In the production of activated carbon by the chemical method, due to the addition of chemicals, great attention should be paid to environmental protection during the manufacturing process, as well as the impact of possible trace elements in the product that are not brought in by the raw materials.   1.2.2 Physical Method Activated Carbon   The method of preparing activated carbon by using carbon as the raw material and steam, carbon dioxide, air (mainly oxygen) or their mixtures (flue gas) as the activation medium, and performing activation at high temperatures (600-1000°C) is called the physical method. Activated carbon produced by the physical method is called physical method activated carbon, also known as physical carbon. Generally speaking, the micropores (pores with a diameter or width less than 1.5 nanometers) of physical carbon are well-developed, and they are mainly used in gas-phase adsorption occasions or small-molecule liquid-phase adsorption occasions.   1.2.3 Chemical-Physical Method or Physical-Chemical Method Activated Carbon   While understanding chemical carbon and physical carbon, it is also necessary to mention chemical-physical method or physical-chemical method activated carbon. By selecting different raw materials and using different combinations of chemical and physical methods, the pore structure of activated carbon can be adjusted, thereby producing many types of activated carbon with different properties. This chemical-physical method or physical-chemical method has been and will be a method for preparing activated carbon that has attracted great attention from activated carbon researchers around the world for many years and for a long time to come.   1.3 Classified by Appearance Form   1.3.1 Powdered Activated Carbon   Generally, activated carbon with more than 90% passing through an 80-mesh standard sieve or with a particle size smaller than 0.175mm is commonly referred to as powdered activated carbon or powdered carbon. Powdered carbon has the advantages of fast adsorption speed and full utilization of adsorption capacity during use, but it requires a proprietary separation method. With the advancement of separation technology and the emergence of certain application requirements, the particle size of powdered carbon tends to become more and more refined, and in some cases, it has reached the micron or even nanometer level.   1.3.2 Granular Activated Carbon   Activated carbon with a particle size larger than 0.175mm is usually called granular activated carbon.   Granular activated carbon can be further divided into the following types:   1.3.2.1 Unshaped Granular Activated Carbon   Unshaped granular activated carbon is generally made from granular raw materials through carbonization, activation, then crushing and sieving to the required particle size. It can also be made by adding an appropriate binder to powdered activated carbon and processing it appropriately.   1.3.2.2 Cylindrical Activated Carbon   Cylindrical activated carbon, also known as columnar carbon, is generally made from powdered raw materials and binders through kneading, extrusion molding, then carbonization, activation and other processes. It can also be made by extrusion molding with powdered activated carbon and binders. Columnar carbon can be solid or hollow; hollow columnar carbon has one or several regular small holes artificially made inside.   1.3.2.3 Spherical Activated Carbon   As the name suggests, spherical activated carbon is spherical activated carbon. Its preparation method is similar to that of columnar carbon, but with a pelletizing process. It can also be made from liquid carbon-containing raw materials through spray granulation, oxidation, carbonization, and activation, or from powdered activated carbon with binders through pelletizing. Spherical activated carbon can also be divided into solid and hollow spherical activated carbon.   1.3.3 Activated Carbon of Other Shapes   In addition to the two major categories of powdered activated carbon and granular activated carbon, there are other shapes, such as activated carbon fiber, activated carbon fiber blanket, activated carbon cloth, honeycomb activated carbon, activated carbon plate, etc.   1.4 Classified by Application Scenario   As mentioned earlier, activated carbon is widely used in almost all national economic sectors and people's daily lives. Because of this, it is very difficult to classify activated carbon according to its application scenarios. The problem is that the same type of activated carbon can be used in multiple scenarios, and a certain scenario can also use multiple types of activated carbon to achieve the same purpose. People often gain an understanding of activated carbon through its applications, so they often prefix the term "activated carbon" with a modifier (e.g., sugar-use activated carbon, injection-use activated carbon, monosodium glutamate-use activated carbon, water purification activated carbon, etc.) as a customary vague classification method for activated carbon.   Activated carbon has adsorption, catalytic, and certain chemical reaction properties, as well as relative physical and chemical stability. It is widely used in almost all national economic sectors and people's daily lives.   3.1 Application of Activated Carbon in Gas (Vapor) Phase Adsorption   The large-scale application of activated carbon in gas (vapor) phase adsorption began with gas protection during World War I. Since then, it has gradually expanded to other fields. To summarize, its main applications are as follows:   3.1.1 Protection Against Toxic or Harmful Gases   Gas masks, face masks, and protective clothing are typical examples of the application of activated carbon.   3.1.2 Purification, Refining, and Separation of Gases (Vapors)   Air purification, adsorption separation and purification of nitrogen and oxygen in air; pressure swing adsorption separation and purification of industrial hydrogen; solvent recovery; removal of sulfur dioxide and nitrogen oxides from flue gas; air conditioning; gas purification in the working environments of aerospace and deep-sea submarines, etc., all rely on activated carbon.   3.2 Application of Activated Carbon in Liquid Phase Adsorption   The earliest application of activated carbon started with the refining of sugar solutions by Europeans. Now, the application of activated carbon in liquid phase adsorption has spread to many industrial sectors and people's daily lives.   3.2.1 Application in the Food Industry   All sweeteners, condiments, edible oils, and beverages use activated carbon for decolorization and refining. So far, this application remains one of the largest markets for activated carbon, especially in China and many developing countries that are undergoing industrialization.   3.2.2 Application in the Pharmaceutical Industry   All raw materials for artificial synthesis and biopharmaceuticals, especially western medicines, use activated carbon for decolorization and refining. The main role of activated carbon adsorption is to remove impurities, improve purity, and remove pyrogens. This is another large market for activated carbon.   3.2.3 Application of Activated Carbon in the Chemical Industry and Other Industries   In the petrochemical industry, activated carbon is used for oil product refining, desulfurization, deodorization, and as a catalyst carrier; in the inorganic chemical industry, it is used for the refining and purification of industrial and pharmaceutical-grade products; in the metallurgical industry, especially in hydrometallurgy, it is used for the extraction of precious metals such as gold and platinum; and in the dyeing and weaving industry, it is used for dyes, mordants, etc. These are newly developed markets for activated carbon in recent decades.   3.3 Application of Activated Carbon in Environmental Protection   In the application of activated carbon, environmental protection has gradually become the largest consumption field of activated carbon since the 1960s and 1970s. Activated carbon used for environmental protection in gas and liquid phase adsorption often accounts for more than 60% of the total consumption in developed countries. The gas-phase treatment in environmental protection involves the purification of various industrial and domestic waste gases and the recovery of useful solvents. The liquid-phase adsorption treatment in environmental protection is mainly used for the treatment of domestic water, sewage, and industrial wastewater. In developed countries, domestic drinking water, urban domestic wastewater, and industrial wastewater are basically treated with tertiary purification including activated carbon treatment. Activated carbon used for water treatment in developed countries accounts for about 40-50% of their total consumption. China has begun to attach importance to environmental issues, and it is expected that in the near future, the application of activated carbon in water treatment in China will achieve leapfrog development.   3.4 Application Progress of Activated Carbon in High-Tech Fields   In the past 20 years, high technology has become a key area for economic development in countries around the world. The rapid development of science and technology has promoted the development of activated carbon. High-performance activated carbon with high specific surface area, high pore volume, and high adsorption capacity, ultra-fine activated carbon, and various products of activated carbon are constantly emerging. These new types of activated carbon have been frequently mentioned in the literature for their applications in many fields such as high-tech electronic electrodes, new catalyst carriers, storage of electrical energy and high-energy-density substances (such as compressed or liquefied hydrogen, natural gas, etc.), electric vehicles, and functional green environmental protection. Many of them have been put on the market. Chinese researchers of activated carbon are also making unremitting efforts, and breakthroughs have been made in some aspects. It is expected that China's activated carbon will occupy a place in the high-tech field in the new century.