【作者】 苗莹；

【导师】 王高升； 于孟辉； 张东彪；

【作者基本信息】 天津科技大学 ， 轻工技术与工程（专业学位）， 2022， 硕士

【摘要】 水热法处理农业秸秆所得水解液中富含糖类化合物,可被微生物转化为生物基燃料和化学品。然而,水解液中所含酚类化合物对于微生物生长及代谢存在抑制作用。本论文研究了通过絮凝法去除玉米秸秆水解液中的酚类化合物来提升水解液沼气发酵性能的工艺,同时对絮凝处理后所得絮体的抗氧化活性进行了分析。首先分别以阳离子聚丙烯酰胺（CPAM）、氯化铁（Fe Cl₃）以及聚合氯化铁（PFC）作为絮凝剂,考察了絮凝剂用量、絮凝体系p H、絮凝剂分子量、水解液初始浓度等工艺条件对于玉米秸秆水解液中酚类化合物去除的影响。结果表明,在CPAM分子量为800万,用量0.2 g/L、p H=9.0、絮凝时间为3.0h等条件下进行絮凝处理,酚类化合物去除效率达到最大值16.62%。分别以PFC和Fe Cl₃作为絮凝剂,在絮凝剂用量2.0 g/L、水解液p H=9.0、絮凝时间为3.0h等条件下,酚类化合物去除率的最大值可分别达到21.24%及22.69%。在此基础上,考察了以CPAM为助凝剂对于Fe Cl₃及PFC絮凝去除水解液中酚类化合物的影响。结果显示,以CPAM为助凝剂可显著提升水解液中酚类化合物的去除率。在助凝剂CPAM用量为0.1 g/L,絮凝剂Fe Cl₃和PFC用量分别为2.0 g/L,水解液p H=4.0以及絮凝时间3.0h等条件下,水解液中的酚类化合物去除率分别达到了27.09%和30.59%。研究表明,在酸性及碱性条件下,添加助凝剂CPAM均可强化水解液中酚类化合物的去除效果。其中,酸性条件下无机絮凝剂Fe Cl₃和PFC首先通过电荷中和作用或电荷中和-架桥机制吸附酚类化合物,然后CPAM通过电荷中和作用及架桥机制强化酚类化合物的去除;碱性条件下,Fe Cl₃和PFC首先通过卷扫机理吸附酚类化合物,而后CPAM通过补丁及卷扫机理强化酚类化合物的去除。接下来进一步考察了水解液初始浓度对于酚类化合物去除的影响,结果显示将水解液稀释后可促进酚类化合物的去除。将水解液稀释3倍后在无机絮凝剂2.0 g/L、CPAM 0.1 g/L用量条件下进行絮凝处理,经过CPAM、Fe Cl₃、PFC、Fe Cl₃-CPAM以及PFC-CPAM等絮凝剂处理后,水解液的酚类化合物去除率达到了28.23%、22.16%、26.53%、41.61%和43.04%。水解液的BOD/COD分别提升了29.51%、27.87%、24.59%、42.62%和39.34%,可生化降解性明显提升。将絮凝后所得水解液在接种比0.2kg VS/kg COD、37±1℃、碱度2700 mg/L等条件下接种菌泥进行沼气发酵后,沼气发酵速率分别提升了26.25%、179.14%、56.83%、182.76%及33.99%;经过CPAM、PFC及PFC-CPAM处理后,累积甲烷得率分别提升了20.00%、16.86%及18.94%。通过红外光谱对絮体进行化学组分分析,确认了絮体中的有机化合物主要由酚类化合物组成。通过ABTS⁺·（2,2’-联氮-双-3-乙基苯并噻唑啉-6-磺酸）自由基清除率实验证实,絮体具有一定的抗氧化活性,每克絮体相当于3.40～17.23 mg BHT（2,6-二叔丁基-4-甲基苯酚）抗氧化剂,可作为原料进一步加工制备抗氧化剂,从而提升工艺的整体经济性。更多还原

【Abstract】 The hydrolysate obtained from the hydrothermal treatment of agricultural straw is rich in sugar compounds,which can be converted into bio-based fuels and chemicals by microorganisms.However,the phenolic compounds contained in the hydrolysate have inhibitory effect on the growth and metabolism of microorganisms.This paper studied the process of removing phenolic compounds in corn stover hydrolysate by flocculation to improve the biogas fermentation performance of hydrolysate,and analyzed the antioxidant activity of flocs obtained after flocculation.Firstly,cationic polyacrylamide（CPAM）,ferric chloride（Fe Cl₃）and polyferric chloride（PFC）were used as flocculants,and the process conditions such as the amount of flocculant,the p H of the flocculation system,the molecular weight of the flocculant,and the initial concentration of the hydrolysate were investigated.Effect on the removal of phenolic compounds from corn stover hydrolysate.The results showed that the removal efficiency of phenols reached the maximum value of 16.62%after flocculation treatment under the conditions of CPAM molecular weight of 8 million,dosage of 0.2 g/L,p H=9.0,and settling time of 3.0 h.Using PFC and Fe Cl₃ as flocculants respectively,under the conditions of flocculant dosage of 2.0 g/L,p H of hydrolysate was 9.0,and flocculation time of 3.0h,the maximum removal rates of phenolic compounds can reach 21.24%and 22.69%,respectively.On this basis,the effect of using CPAM as coagulant on Fe Cl₃ and PFC flocculation to remove phenolic compounds in hydrolysate was investigated.The results showed that the removal rate of phenolic compounds in the hydrolysate can be significantly improved by using CPAM as a coagulant.Under the conditions of 0.1 g/L of coagulant CPAM,2.0 g/L of flocculants Fe Cl₃ and PFC,p H of hydrolysate was 4.0 and settling time was 3.0h,the removal rate of phenolic compounds in hydrolysate reached 27.09%and 30.59%.Studies have shown that the addition of coagulant aid CPAM can enhance the removal effect of phenolic compounds in the hydrolysate under acidic and alkaline conditions.Among them,inorganic flocculants Fe Cl₃ or PFC firstly adsorbed phenolic compounds through charge neutralization or charge neutralization-bridging mechanism under acidic conditions,and then enhanced the removal of phenolic compounds through CPAM charge neutralization and bridging mechanism;under alkaline conditions,Fe Cl₃ or PFC firstly adsorbed phenolic compounds through a roll-sweep mechanism,and then CPAM enhanced the removal of phenolic compounds through a patch and roll-sweep mechanism.Next,the effect of the initial concentration of the hydrolysate on the removal of phenolic compounds was further investigated,and the results showed that diluting the hydrolysate can promote the removal of phenolic compounds.After diluting the hydrolysate by 3 fold,flocculation was carried out under the conditions of inorganic flocculant 2.0 g/L and CPAM0.1 g/L.After treatment with flocculants such as CPAM,Fe Cl₃,PFC,Fe Cl₃-CPAM and PFC-CPAM,the removal rate of phenols in the hydrolysate reached 28.23%,22.16%,26.53%,41.61%and 43.04%respectively.The BOD/COD increased by 29.51%,27.87%,24.59%,42.62%and 39.34%respectively,and the biodegradability was significantly improved.After the hydrolysate obtained after flocculation was inoculated for biogas fermentation under the conditions of inoculation ratio of 0.2 kg VS/kg COD,37±1℃,and alkalinity of 2700 mg/L,the biogas fermentation rate increased by 26.25%,179.14%,56.83%,182.76%,and 33.99%respectively.After CPAM,PFC and PFC-CPAM treatments,the cumulative methane yields increased by 20.00%,16.86%and 18.94%,respectively.The chemical composition of the flocs was analyzed by infrared spectroscopy,and it was confirmed that the organic compounds in the flocs were mainly composed of phenolic compounds.The ABTS⁺·（2,2′-azino-di（3-ethylbenzothiazoline-6-sulfonic acid））free radical scavenging rate experiment confirmed that the flocs have a certain antioxidant activity,and each gram of flocs is equivalent to 3.40～17.23 mg BHT（butylated hydroxytoluene）antioxidants,which can be used as raw materials for further processing to prepare antioxidants,thereby improving the overall economy of the process.更多还原