| The production technology of traditional diosgenin (the old technology) usuallyused the process of "natural fermentation and acid solution to extract diosgenin". In theprocess of turmeric paste acid solution, a lot of starch and cellulose were acidolysisedinto sugars in saponin wastewater, resulting high COD, high organic matter content, deepchromaticity and serious waste water pollution in the waste water. The direct separation(new technology) was a new technology of turmeric diosgenin clean production thatcarried out in recent years. It used physical method to separate the fiber and starch inturmeric, then conducting the process of “fermentation and acid solution to extractdiosgenin”. Compared with the old technology, the new technology reduced theconsumption of materials such as water and hydrochloric acid, making the follow-up ofwastewater discharge and pollution load greatly reduced. However, a large number ofwaste generated was discarded or stacked in the factory. It was not only a pollution to theenvironment, but also a waste of resources, hindering the further popularization andapplication of new technology. While there were a number of research on comprehensiveutilization of the old process waste, the research on comprehensive utilization of the newprocess waste was little. The composition of new and old technology waste was different.Therefore, the research on new technology of waste residue composition analysisconducted on the basis of comprehensive utilization was more targeted. It was of a greatsignificance to solve bottleneck development of saponin industry and promote the cleanproduction technology progress in the industry.On the basis of comparative analysis of old and new process waste residuecomposition, this study conducted the preparation of carbon materials according to thecharacteristics of new technology waste with high fiber, half number of fiber content,small ash content and density, and large specific surface. Adopting the method of singlefactor (biochar: rate of heating up, pyrolysis temperature, pyrolysis time; activatedcarbon: impregnation ratio, activation temperature, activation time) and orthogonal test,the product yield and methylene blue adsorption value as a reference index to carry on the preparation conditions of the optimization experiment, explored the best optimizationconditions of preparation of carbon materials specific surface area, pore diameter,scanning electron microscopy and the adsorption character of value. In the sameconditions, we conducted a adsorption experiments with commercial activated carbon.Finally, we made a summary analysis to the environmental benefits and cost benefitwhen carbon materials applied to industrial production. It had certain referencesignificance for industrial applications.The main conclusion of experiment was as follows:1.The main ingredients of new technology diosgenin waste were:20.95%cellulose,15.87%hemicellulose,18.48%lignin,0.83%reducing sugar and9.06%starch.2.The most significant factor to the activated carbon adsorption capacity and yieldwas pyrolysis temperature, followed by the pyrolysis time and heating rate. The bestpreparation conditions for biochar was:4℃/min of temperature speed,500℃ofpyrolysis temperature,35min of pyrolysis time. Under the condition, the biochar yieldwas24.80%, adsorption value of methylene blue was16.237mg/g, specific surface areawas338.8m2/g, and total pore volume was0.19cm3/g.3.The best preparation conditions for activated carbon were: impregnation ratio of1.5:1, the activation temperature of550℃, the activation time of45min. On theconditions, activated carbon yield was51.2%, adsorption value of methylene blue was85.8mg/g. Analyzed specific surface area, the specific surface area of activated carbonwas601m2/g, with developed pore and lot of holes.4.The influence on the yield and properties of activated carbon when various factorschanged in the optimal experimental conditions: The influence of impregnated ratio andactivation temperature on the yield and properties of activated carbon was bigger, theactivation temperature effect was very small. When impregnation ratio increased, theyield of activated carbon first decreases then increased and the adsorption performancegradually rise. When the activation temperature increased, the yield of activated carbondecreased and adsorption performance gradually increased till to balance.5. Studied the adsorption capacity to saponin wastewater and heavy metal wastewater of biochar and commercial activated carbon respectively through contrastexperiment, the results showed that COD removal rate of biochar in saponin wastewaterunder the optimal conditions was45.44%, the chroma removal rate was52.40%. CODremoval rate of activated carbon in saponin wastewater under the optimal conditions was45.44%, the chroma removal rate was52.40%，The biochar rates were all above the levelof the activated carbon adsorption.6. Biochar preparation process is much simpler than activated carbon, and itsapplication to a more targeted, flexible, more economic and environmental advantages. |
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