【作者】 熊征；

【导师】 张晓昱；

【作者基本信息】 华中科技大学 ， 微生物学， 2009， 博士

【摘要】 碱法制浆蒸煮黑液因其高碱性、高COD和高木质素含量等“三高”特点，始终是工业废水低成本、资源化处理技术的难题。传统理化处理黑液技术因其成本及环境友好性问题正在逐渐被生物处理技术所代替。利用产酸微生物析出造纸黑液中的木质素，一定程度上能减轻造纸黑液污染，但效果有限，且生物酸析机制不清晰。基于此，本文主要探讨了褐腐真菌生物酸析处理造纸黑液的机理、废水处理工艺及酸析木质素资源化利用等问题，为生物处理造纸黑液提供新的理论依据和技术支持。通过比较研究无机酸和有机酸处理黑液的特性来论证有机酸酸析处理造纸黑液的可行性。结果显示草酸酸化黑液pH到4．0时，析出的木质素含量达到75．0％以上，COD和色度去除率分别达到42．0％和92．0％，其酸析过程、效果同无机酸酸析相同。因此，有机酸草酸可以取代硫酸酸析处理黑液，其中黑液体系pH降低是黑液中木质素快速析出、COD和色度迅速下降的关键指标。一株具备调节pH能力的产酸菌株IMER2，经形态和分子生物学鉴定，确定该菌株为拟层孔菌（Fomitopsis sp．IMER2）。该菌在刚性破环秸秆木质纤维结构的同时，能够利用速效碳源、半纤维素成分快速合成草酸。该菌生物酸析造纸黑液，pH4以下时木质素去除率达到93．0％，COD和色度去除率分别达到82．7％和88．9％，优于传统酸析处理效果。进一步研究褐腐真菌生物酸析处理黑液的机制。结果显示褐腐真菌处理黑液是一个以酸析木质素为主，吸附、降解木质素为辅的生物反应过程。褐腐真菌在黑液中通过生物合成大量的草酸，快速降低黑液体系pH，导致大量的木质素析出；同时褐腐真菌通过物化吸附和降解木质素，产生一定量的芳香酸，协助降低黑液pH，促进木质素的析出。FTIR、¹H—NMR和GC-MS研究结果表明褐腐真菌主要通过脱甲氧基、芳基羟基化、去酚羟基、侧链氧化等作用方式降解木质素。木质素的苯环结构稳定保留，功能基团活性得到提高，有利于酸析木质素的资源化利用。对褐腐真菌生物酸析处理造纸黑液的影响因素进行研究。结果表明代谢产物C₂O₄^2-及酸析木质素不利于褐腐真菌连续地生物酸析处理造纸黑液。因此，须建立序批式生物酸析处理工艺。该工艺的最适条件是起始黑液pH 7．0，COD 42．0 g／L，褐腐真菌接种量24．0 g／L。褐腐真菌在开放的鼓泡塔生物反应器中成功运行了12个批次共36天，保持了良好的产酸能力，平均COD和色度去除率可达到40．0％和70．0％。对褐腐真菌生物酸析木质素进行资源化利用研究。采用响应面法优化活性炭制备条件，当磷酸浓度为65％，磷料比为4．84：1，活化温度为400℃，活化时间为124 min时，木质素活性炭亚甲基蓝吸附值和得率分别可达到182±4．00 mg／g和56．15±3．81％，其亚甲基蓝吸附性能符合国家木质净水用活性炭一级品标准。表明利用生物酸析木质素可以制备高性能的活性炭。更多还原

【Abstract】 Black liquor is a byproduct of the alkaline pulping process during the production ofpaper pulp.Pollution caused by black liquor is too serious to address because of its highalkaline,high COD loading and high lignin content.Traditional physical and chemicaltreatments of black liquor are gradually being replaced by biological treatment because ofits low-cost and environment-friendliness.Acidification precipitation of lignin from blackliquor can effectively address black liquor pollution by some microorganisms.However,treatment effects are limited,and mechanism of biological acidification precipitation is notclear.This article focused on the biological mechanism of black liquor treatment bybrown-rot fungi,wastewater treatment process and exploitation of lignin,which canprovide theoretical basis and technological support for biological treatment of black liquor.A comparative study about acidifying characteristics of black liquor by inorganic acidand organic acid was firstly investigated.The results showed that organic acid couldcompletely replace inorganic acid to acidify black liquor.When the pH of black liquor wasadjusted to 4.0 by oxalic acid,more than 75.0% lignin could be precipitated and separatedfrom the black liquor.In addition,the effluent COD and color might drop over 42.0% and92.0%,respectively.The key of acid precipitation of lignin,reduction of COD and colorwas lowering pH of black liquor.A strain IMER2 with an ability to adjust pH was identified as brown-rot basidiomyceteFomitopsis sp.IMER2 by morphological and molecular biology.The strain IMER2 couldexcrete and accumulate a large number of oxalic acid by qualitative and quantitative HPLCanalysis.In the process of straw biodegradation by the fungus,straw fiber was rigidlybroken,and some available carbon sources and hemicelluloses were rapidly consumed toproduce oxalic acid.So,the acid-producing brown rot fungus IMER2 could be used fortreatment of black liquor.After black liquor pH was 4.0 below,more than 93.0% lignincould be precipitated and separated,and COD and color reduction reached 82.7% and88.9%,respectively.Noticeably,biological treatment of black liquor by brown rot fungiwas better than conventional acidification treatment. Further analysis of biological treatment mechanism,the results indicated biologicaltreatment processes of black liquor was acidification precipitation of lignin as a main,biological adsorption and degradation of lignin as a supplement.Brown-rot fungi in blackliquor could produce a lot of oxalic acid to rapidly reduce black liquor pH,which resultedin lignin precipitation.Simultaneously,some lignins were adsorbed and degraded bybrown-rot fungi to form an amount of aromatic acids,which can assist in reducing blackliquor pH and enhance biological treatment of black liquor.In addition,the biodegradationof lignin was a primarily modified process with demethoxy,phenolic hydroxylation,dehydroxylation,side-chain oxidation.Some aromatic ring of lignin was retained,andactivities of function in lignin were improved by the fungus.According to previous studies,these lignins could be useful for a variety of industrial applications.To establish a practical treatment process of black liquor,influence of sodium salts andlignin on growth and acid-producing capacity of the fungus IMER2 were studied.Theresults suggested that metabolic products of the fungus such as C₂O₄^2- and precipitatedlignin could inhibit the fungal growth and acid-production.Therefore,a repeated batchtreatment of black liquor was suitably established.The optimal conditions for the repeatedbatch treatment of black liquor were initial black liquor pH 7.0,COD 42.0 g/L,inoculums24.0 g/L.Moreover,the repeated batch process was successfully carried out 12 times over36 days in an air bubble column bioreactor.The average reduction of COD and color wasapproximately 40% and 70%,respectively.At last,utilization of lignin precipitation by acidification was studied.The lignin canbe prepared a kind of high-performance activated carbon.Phosphoric acid concentration（65%）,ration of activation reagent to material （4.84:1）,activation temperature （400℃）,activation time （124 min） were optimized using response surface method.The adsorption ofmethylene blue and the yield of activated carbon could reach 182±4.00 mg/g and 56.15±3.81%,respectively.The adsorption performance of methylene blue has achieved the firstdegree quality of wooden activated carbon for water purification in China.更多还原