Resources recycling by advanced techniques for PVC containing waste plastics

研究项目的目的是开发先进的技术，回收含有废塑料的聚氯乙烯，特别是在日本。顺利的回收系统不仅需要技术，还需要消费者对产品的接受度。特别是，废旧聚氯乙烯产品给日本消费者留下了负面印象，因为日本消费者担心残留的Cl物种对健康产生不利影响，即使浓度低至ppb。因此，为了消除对聚氯乙烯废料衍生产品的担忧，日本应该开发一种不受现有方法限制的新技术。作为脱氢氯化后碳渣生产活性炭的替代方法，我们提出了钾活化法，其优点是钾既可以作为残留Cl种的中和剂，又可以作为碳的活化剂。此外，活性炭中残留的钾和氯化钾可以作为农田肥料使用，但由于盐污染，不能作为钠的肥料使用。我们尝试了活性炭的生产，并确定了玻璃制造装置和配备煤油燃烧器和不锈钢窑的间歇式装置的最佳条件。在750℃条件下制备了表面积大于1000 m^2/g的活性炭。研究发现，炭化前最重要的一步是300-400C的预氧化处理，即形成不可石墨化碳。处理后的活性炭在炭化过程中抑制了熔融形成石墨化炭，提高了活性炭的收率和质量。预氧化处理在间歇装置生产中的重要性也得到了证实。此外，活性炭中的二恶英浓度符合环保标准。活性炭的特性如下：1)活性炭比现有的大多数活性炭具有更强的亲水性。2)通过Boehm法滴定，形成了大量的表面官能团，如OH和COOH，这些官能团与亲水性有关。3)通过添加HNO_3和H_2SO_4等溶液进行了表面改性，稀硝酸溶液对C-C键氧化生成含氧基团特别有效。4) PVC与聚烯烃的混合比例对活性炭的性能有一定影响，聚烯烃的浓度应控制在50%以下。在农业领域的应用正在进行中

The purpose of research project is the development of advanced techniques for the recycling of PVC containing waste plastics, especially in Japan. The smooth recycling system requires not only the technology but also the consumer acceptance of products. Particularly, the products from waste PVC gave a negative impression because Japanese consumers are afraid to an adverse health effect by the residual Cl species, even the concentration as low as ppb. Thus, in order to dispel concerns about products derived from PVC wastes, a new technology unconstrained existing methods should be developed in Japan. As the alternative method for the production of an activated carbon from carbon residues after the dehydrochlorination, we proposed a potassium activation method, whose advantages are that potassium will act both as the neutralizing agent for residual Cl species and as the activating agent for carbon. Furthermore, residual potassium and potassium chloride in the activated carbon can be used … More as a fertilizer in the agricultural fields but not for sodium due to the salt pollution. We attempted the production of activated carbons and determined the optimal condition for both a glass made apparatus and a batch apparatus equipped with a kerosene burner and a stainless-steel kiln. The activated carbon with a surface area of over 1000 m^2/g was prepared at 750C. It was found that the most important step is the pre-oxidation treatment at 300-400C before the carbonization, which means the formation of non-graphitizable carbon. After the treatment, both yield and quality of activated carbon are improved by the inhibition of melting to form graphitizable carbon during the carbonization. The importance of pre-oxidation treatment is confirmed in the production by the batch apparatus, too. In addition, dioxin concentration in the activated carbon meets environmental standards. Characteristics of activated carbon are as follows: 1) The activated carbon is more hydrophilic than most activated carbons available. 2) A large amount of surface functional groups such as OH and COOH, which are titrated by Boehm method, are formed and correlate contribute to the hydrophilic property. 3) The surface modification is successfully performed by add solutions such as HNO_3 and H_2SO_4 and thin nitric acid solutions are particularly effective for the generation of oxygenate group by the oxidation of C-C bonds. 4) Characteristics of activated carbon are somewhat affected by mixing ratios between PVC and polyolefin and the concentration of polyolefin should be control to be less than 50%. An application to agricultural field is now in progress Less