Use Of New Technology Research, Medicinal Charcoal Charcoal Preparation

Owing to its high purity, strong decoloration and quick filtration rate, medicinal charcoal is widely used as an auxiliary agent in the decolorization and refinement of the original Chinese and Western medicine, doxycycline catalyst carrier, blood perfusion. Furthermore, it also absorbs the gastrointestinal tract bacteria acting as detoxification. However, during its preparation using conventional heating methods which are based on heat conduction, convection and radiation, heat is transferred from the outside to the inside, therefore, it heats slowly and forms a non-uniform temperature field. Thus, it takes a very long time on forming well-developed micropore structure. It's urgent to develop a new method to overcome the above mentioned shortcomings. Compared with conventional heating, microwave heating has the following advantages:internal, rapid, selective, easy automated, highly energy-consumption efficient and so on. In recent years, activated carbon produced by microwave heating has become a hot research.China has an abundant bamboo resource, so preparing medicinal charcoal from bamboo not only increases the added value of the bamboo, but also widens the resources of the raw materials. However, medicinal charcoal based on bamboo charcoal which was produced by microwave heating has not yet reported in the literature.This thesis described a method to prepare medicinal charcoal from bamboo charcoal which meets the adsorbent affinity of the Chinese medicinal pharmacopoeia requirements, using conventional heating and microwave heating method, respectively. It adopts either water steam or carbon dioxide as physical activation agent, which can avoid disadvantages brought about by chemical methods, so it eliminates pickling, washing and other processes that might pollute the environment. The objective is looking for a new energy-saving and environmental friendly method to prepare medicinal charcoal. Three types of activation process, namely:conventional heating-steam, conventional heating-carbon dioxide and microwave heating-steam activation were mainly studied. The optimized process conditions were decided by choosing the main corresponding factors, such as activation temperature, activation time, activation agent flow, particle size, influencing on adsorbent affinity, iodine adsorption value and the yield of the medicinal charcoal. Moreover, the pore size distribution of medicinal charcoal under optimized process conditions were characterized by automatic physical and chemical adsorption instrument, made by Quantachrome Corporation in the United States. Meanwhile, different activation agents and heat mechanisms were discussed in this thesis, too.(1) The optimization process conditions of medicinal charcoal prepared by conventional heating-steam were obtained as follows:particle size between 3.35mm and 4.75 mm, activation temperature 900℃, activation time 60min, and steam flow 1.10ml/min. The adsorbent affinity of medicinal charcoal was 13.42, which meets the adsorbent affinity of the Chinese medicinal pharmacopoeia requirements, the iodine number was 1107.50mg/g, and the yield was 52.7%.(2) The optimization process conditions of medicinal charcoal prepared by conventional heating-carbon dioxide were obtained as follows:particle size between 3.35 mm and 4.75 mm, activation temperature 950℃, activation time 120 min, and carbon dioxide 600 ml/min. The adsorbent affinity of medicinal charcoal was 13.28, which meets the adsorbent affinity of the Chinese medicinal pharmacopoeia requirements, the iodine number was 1029.84 mg/g, and the yield was 54.3%.(3) The optimization process conditions of medicinal charcoal prepared by microwave heating-steam were obtained as follows:particle size between 3.35 mm and 4.75 mm, activation temperature 850℃, activation time 12 min, and steam flow 3.00 ml/min. The adsorbent affinity of medicinal charcoal was 13.57, which meets the adsorbent affinity of the Chinese medicinal pharmacopoeia requirements, the iodine number was 1155.34mg/g, and the yield was 36.0%.(4) The pore size distributions of three medicinal charcoals and bamboo charcoal achieved at optimization process conditions were analyzed by DA equation, HK equation, BJH method and NLDFT theory. The results show that when bamboo charcoal treated by activation, its total pore volume and specific surface area increase remarkably, as well as its content of ultramicropore. So, the prepared medicinal charcoals are characterized by microporous.(5) By analyzing different activation agents and heat mechanisms, it's found that the diameter of steam molecule is smaller than that of carbon dioxide molecule; Moreover, steam molecule is a "V"-shaped while carbon dioxide molecule is linear, therefore, the spread of steam is faster than that of carbon dioxide during bamboo charcoal activation giving rise to the higher rate of steam activation of the carbon dioxide. Bamboo charcoal and steam are both microwave absorption material, during the activation, there are more active sites generated by microwave heating than those by conventional heating. Compared with conventional heating-steam, microwave heating-steam is faster, which saves about 80% time on the optimized process conditions.Experimental studies found that bamboo charcoal as raw material and steam as the activation agent to produce bamboo charcoal-based medicinal charcoal, which is heated by microwave, is feasible. This heating method has the potential to overcome the conventional process problems. So, it can provide a better alternative for industrial production of medicinal charcoal.