【作者】 李元虎；

【导师】 赵素合；

【作者基本信息】 北京化工大学 ， 材料科学与工程， 2012， 博士

【摘要】 生物法脱硫是利用与硫有代谢能力的菌体，定向诱发硫化橡胶的硫交联键断裂，达到再生废橡胶的目的。这是近年来发展的一种新的无污染的废胶回收方法。符合国家保护环境和持续发展的科学发展理念。本论文自培养、筛选、驯化了四种菌体（氧化亚铁硫杆菌、排硫硫杆菌、鞘氨醇单胞菌和酵母菌），研究了各种菌体的生长工艺条件；考察了弹性体和橡胶助剂对菌体的毒性；确定了四种菌剂分别与废胎面胶粉共培养脱硫的工艺条件、培养基配方、接种量等，用四种菌体分别对废轮胎胎面胶粉进行脱硫再生实验；通过测定脱硫后废胶粉表面的化学基团、元素含量、结合能状态和溶胶含量的变化及脱硫胶粉与橡胶共混胶料的加工性能、综合使用性能和形态结构，系统评价了废胶粉与菌体培养脱硫的效果，定量计算了胶粉脱硫后对胶料性能的贡献，为这种新的再生方法奠定了理论和应用基础。研究结果表明，天然橡胶、丁苯橡胶等对四种菌体的毒性很小，氧化锌和硫化促进剂对菌体有较高的毒性，因此脱硫过程必须采取先用乙醇对废胶粉解毒，然后再加入到已生长旺盛的菌体培养液中进行脱硫再生的工艺；氧化亚铁硫杆菌最佳脱硫时间为20天。培养基中Fe2+浓度为9K培养基的25%，脱硫效果显著。其能将胶粉表面的S代谢为硫盐，对胶粉表面的共轭C=C双键有一定的破坏作用，经脱硫后，胶粉表面的S元素含量下降了52.8%，溶胶份数增大了58%；排硫硫杆菌与废胶粉共培养脱硫7天后培养基中的S2-2O3消耗殆尽，但菌体还可维持较高的生物量，说明菌体可以利用废胶中的化合硫。继续培养20天后，胶粉表面的S含量下降了40.6%， S-S键和S-C键分别减少了18.3%和42.3%，在脱硫胶粉表面形成了S=O基团，脱硫胶粉的溶胶份数增大了46.7%。还发现该菌可将胶粉表面的C=C氧化为C=O键，有氧化降解的功效；鞘氨醇单孢菌是个相对比较温和，对环境耐受程度较高的首次培育的新菌种，采用置换培养基工艺，鞘氨醇单孢菌与胶粉共培养脱硫25~50天，胶粉中部分硫交联键被氧化生成亚砜S=O基团，部分亚砜基团继续被氧化生成砜O=S=O基团，该菌也能氧化破坏部分C=C键生成C=O基团。脱硫的胶粉表面S元素含量下降了22.9%，溶胶份数增大了85%；酵母菌代谢产物G-SH也有定向对废胶粉脱硫的效果，共培养脱硫6天后，胶粉表面S-S键明显减少，而S-C键保持不变。脱硫胶粉硫含量减少了56%，脱硫胶粉的溶胶份数增大了55%。综合考虑，鞘氨醇单胞菌对废胶粉的脱硫再生效果更显著和经济。与原胶粉分别与天然胶和丁苯胶共混胶料比，四种菌剂脱硫再生获得的改性胶粉-橡胶共混胶料力学性能、动态力学性能得到明显改善，胶粉与基胶间的界面结合作用增强。用鲨鱼烯硫化交联产物作为硫化橡胶的模型化合物，揭示鞘氨醇单孢菌对化合硫的代谢-转变机理。培养基对模型化合物结构无影响，在培养基中接入菌剂后，模型化合物的颜色变浅。液相色谱-紫外（HPLC-UV）测试发现，脱硫后鲨鱼烯硫化交联产物的峰位明显降低；质谱测试进一步表明，鲨鱼烯硫化交联产物中单硫和双硫交联键略减少，三硫交联键明显降低，四硫键交联的模型化合物则消失。这充分证明鞘氨醇单孢菌对硫交联键，尤其是多硫键有代谢转变效果。使用工业中广泛应用的再生剂420脱硫再生废胶粉。脱硫过程即发生了主链断裂，又发生了交联键的断裂。胶粉总的交联密度和多硫交联密度降低，双硫交联键的密度略有减少，而单硫交联键的密度几乎保持不变。脱硫之后，胶粉的交联键主要为单硫键和多硫键。延长脱硫时间可以提高脱硫效果，最佳的脱硫温度为180℃。更多还原

【Abstract】 Microbial desulfurization method uses bacteria which exhibit biologicalactivity towards sulfur to break down sulfur crosslinkds of vulcanized rubberso as to achieve the purpose of regeneration of waste rubber. It is a newmethod for recycling waste rubber in recent years and meets the nationalrequirements of scientific and sustainable development.In this paper, four different bacterias （Thiobacillus ferrooxidans,Thiobacillus sp., Sphingonomas sp., and Yeast） after culture, isolation, andidentification are used for ground tire rubber （GTR） desulfurization. Thetoxicity test about the growth of bacterias in presence of different elastomersand rubber additives are invested. The optimal conditions for each bacteriumco-cultured with GTR such as desulfurization process, medium formulation,pH values, and inoculum are researched. The desulfurization effect on GTR bybacterias is systematically evaluated through analysis of the chemical groups,element content, bonding energy, and sol fraction before and afterdesulfurization. The contribution to the properties of the rubber blend withdesulfurated GTR （DGTR） are quantitatively calculated though evaluation ofprocessing performance, integrated application performance, and morphologystructure. All these results settle the theory and application basis of this newrecycling method.The results show that the toxicity of natural rubber and styrene-butadienerubber is low to the bacterias. Zinc oxide and vulcanization accelerator havehigh toxicity to bacteria. Therefore, GTR must be taken a detoxification byethanol before desulfurization, and then added to medium with vigorousgrowing bacteria. Thiobacillus ferrooxidans has a good effect ondesulfurization GTR when co-cultured time is20days and Fe2+concentrationof medium is25%of9K medium. T. ferrooxidans can oxide sulfur on the surface of GTR to SO₄^2-. A rupture of conjugated C=C bonds and a reductionof sulfur content by52.8%on the surface of GTR have occurred duringdesulfurization. The sol fraction of GTR increases by58%, from its original4.69%to7.43%. When Thiobacillus sp. is co-cultured desulfurization withGTR for7days, S2-2O3in medium has been exhausted and biomass can alsokeep a high level. It is revealed that bacteria can take advantage of sulfur onGTR surface. When continued co-cultured to20days, sulfur content on thesurface of GTR decreses by40.6%, and the content of S-S groups and S-Cgroups are respectivily reduced by18.3%and42.3%. S-O groups are formedon the DGTR surface. The sol fraction of GTR increases by58%.Thiobacillus sp. can oxide C=C bonds to C=O groups. Sphingomonas sp. is anew and relatively moderate strain with high environmental tolerance. It isfirst used for rubber desulfurization. Sphingonomas sp. is co-cultured withGTR for25-50days by replacement medium procress. After desulfurization,sulfur crosslinks are broken down to form S=O sulfoxide groups duringdesulfurization process, and partical sulfoxide groups are continuely oxidizedto form the sulfone O=S=O groups. Sphingonomas sp. can oxide C=C bondsto C=O groups. Sulfur content on the surface decreases by22.9%and solfraction increses by85%. G-SH, thiol-containing product generated duringYeast metabolism, can be used for the desulfurization regeneration of wasterubber. After desulfurization, sulfur content is reduced by56%, S-S groupsare increased by54%, and S-C groups remain unchanged. The sol fraction isincreased by55%. Though comprehensive consideration, desulfurizationeffect on GTR by Sphingonomas sp. is more remarkable and economy.Compared with rubber composites filled with GTR, DGTR filled rubbercomposites has better mechnical properties, dynamic mechnical properties,and improved interface between DGTR and rubber matrix.Sulfur crosslined squalene is used as a model of vulcanized rubbercompounds for revealing sulfur crosslink bonds metabolism mechanism bySphingomonas sp. Medium has no effect on the structure of modelcompounds. After inoculation of Sphingomonas sp., the color of the modelcompounds fades and the peak values of the model compounds aresignificantly reduced by Liquid chromatography-ultraviolet （HPLC-UV）test. Mass spectrometry furthur indicates that the monosulfide bonds anddisulfide bonds decrease slightly, trisulfide bonds decrease significantly and four-sulfur cross-linked model compounds disappeares. The relsutessuggest that Sphingomonas sp. indeed has desulfurization effect on GTRand mainly cut polysulfur cross-linked bonds during desulfurizationprocess.Desulfurization regeneration activitor420（RA420） is widely used forindustrial recycling waste rubber. Both main chain scissions and crosslinkscissions are ocuured during desulfurization process. The total amount ofcrosslink as well as the fraction of the polysulfidic crosslink obviouslydecreases, whereas the disulfidic crosslink slightly decreases and themonosulfidic crosslink remains constant. After reclaiming, the crosslinksstill present in waste rubber are mainly disulfide and monosulfidecrosslink. Extending the desulfurization time can increase thedesulfurization and the optimal temperature for desulfurization180°C.更多还原