【作者】 冒海燕；

【导师】 周定国； 汪孙国； Zaher Hashisho；

【作者基本信息】 南京林业大学 ， 木材科学与技术， 2013， 博士

【摘要】 本论文以农林废弃物（松木片、麦秸）为原料，采用微波加热和KOH活化技术制备活化生物质炭，并探索了活化生物质炭的制备工艺参数、碘值、得率、孔隙结构和表面官能团；采用自主设计的吸附-脱附装置进行吸脱附甲苯和丙酮实验，着重研究了KOH/生物质炭配比、甲苯和丙酮的初始浓度、吸附温度等对其吸附量、穿透曲线和吸附等温线的影响，并采用Dubinin-Radushkevich（DR）模型进行拟合。最后，采用微波法再生载甲苯和丙酮的活化生物质炭，探索了微波输出功率、气流流速和增加水蒸汽装置对载甲苯和丙酮活化生物质炭再生速率的影响，并与传统电加热法在加热时间、升温速率、再生效率和能耗等方面进行了对比。本研究得到的结论归纳如下：（1）以碘值为衡量指标优化的生物质炭和活化生物质炭制备工艺参数：炭化阶段的炭化温度为550℃，升温速率为10℃/min，炭化时间为2h和增加水蒸气装置；微波活化阶段的微波功率600W，微波时间30min，流量为0.5L/min和增加水蒸气装置。生物质炭化物（松木炭和麦秸炭）的得率在23-29%之间，活化生物质炭的得率在72-81%之间。随着KOH/生物质炭配比从0.5增加到3.0，松木活化生物质炭的比表面积从1053m2/g增加到2044m2/g；微孔孔容和总孔容也呈现出了同样的趋势，分别从0.373cc/g增加到0.701cc/g，0.473cc/g增加到0.933cc/g。麦秸活化生物质炭的比表面积也从942m2/g增加到1250m2/g；微孔孔容和总孔容分别从0.319cc/g增加到0.411cc/g，0.419cc/g增加到0.601cc/g。(2)常温常压下，甲苯和丙酮的初始浓度为200ppmv，不同KOH/生物质炭配比下制备的活化生物质炭具有不同的吸附性能，随着配比的增加，吸附量也随着增加。对于吸附质甲苯，配比从0.5增加到3.0，松木活化生物质炭的吸附量从22.3%增加到47.6%，麦秸活化生物质炭的吸附量从17.1%增加到32.7%。对于吸附质丙酮，松木活化生物质炭的吸附量从15.4%增加到21.7%，麦秸活化生物质炭的吸附量从14.0%增加到17.8%。随着甲苯和丙酮浓度从100增加到300ppmv，活化生物质炭的吸附量增大；对甲苯而言，松木活化生物质炭的吸附量从43.4%增加到51.3%，而麦秸活化生物质炭的吸附量则从20.2%增加到24.4%；两种活化生物质炭对丙酮的吸附量也具有同样的增加趋势。比较6种系列活化生物质炭的穿透曲线形状发现，配比为3.0的松木和麦秸活化生物质炭的曲线最为陡峭，而配比为0.5的松木和麦秸活化生物质炭的曲线最为平缓，因此，穿透时间也越长。在相同浓度下，甲苯的穿透时间比丙酮要长，达到饱和的时间也长，活化生物质炭对其吸附能力较好，饱和吸附量较大。甲苯和丙酮浓度在200ppmv下，当温度从25℃上升到45℃，系列活化生物质炭对甲苯和丙酮的吸附量都明显下降。KOH/生物质炭配比为3.0的松木活化生物质炭和麦秸活化生物质炭对甲苯的吸附量分别从47.6%降到25.0%和32.7%降到19.2%；松木活化生物质炭和麦秸活化生物质炭对丙酮的吸附量分别从21.7%降到15.3%和17.7%降到12.0%。（3）在常温下测试吸附等温线的结果表明，在相对压力较低的情况下，活化生物质炭的吸附量急剧上升；随着相对压力增大，吸附等温线呈水平或接近水平状，表明其孔隙结构以微孔为主。甲苯和丙酮在活化生物质炭上的吸附量随着KOH/生物质炭配比的增加而增加，配比为3.0的松木和麦秸活化生物质炭对甲苯的吸附量分别达到最大为71.9%和36.2%。松木和麦秸活化生物质炭对甲苯的吸附能力强于对丙酮的吸附能力。松木活化生物质炭对甲苯和丙酮的吸附能力大于麦秸对甲苯/丙酮的吸附能力。不同温度（25、35和45℃）下，甲苯和丙酮在系列活化生物质炭上的吸附等温线表明，甲苯和丙酮的吸附量随着温度的升高而降低，这两种活化生物质炭对甲苯和丙酮吸附等温线的试验数据都能采用Dubinin-Radushkevich模型进行很好地拟合。松木活化生物质炭和麦秸活化生物质炭对甲苯和丙酮吸附等温线拟合DR方程的平均相对误差分别为3.3%（甲苯）、5.0%（甲苯）和4.1%（丙酮）、8.1%（丙酮）。因而，松木活化生物质炭比麦秸活化生物质炭的吸附曲线能更好地拟合DR方程。（4）微波加热法再生载甲苯和丙酮活化生物质炭，经过5次吸附-微波辐射再生之后，两种活化生物质炭的再生率都达到99.7%以上；对于松木活化生物质炭对甲苯和丙酮的吸附量分别在457.0-455.5mg/g和229.5-231.3mg/g之间变化；对于麦秸活化生物质炭对甲苯和丙酮的吸附量分别在329.0-330.8mg/g和184.1-185.4mg/g之间变化。随着微波输出功率、气流流速和湿氮气的增加，微波加热再生的速率随之增加，最后得出优化微波再生参数为：600W、1L/min和增加湿氮气。在与传统电加热法相比较试验显示，对于再生载甲苯松木活化生物质炭的试验，恒功率微波加热法、恒温微波加热法和电加热法的再生速率分别为：32.9%/min、1.7%/min和0.9%/min；同样对于再生载丙酮松木活化生物质炭的试验，采用以上3种方法测试的再生速率分别为：99.7%/min、5.1%/min和1.7%/min。对比升温速率发现，恒温微波加热法的升温速率为186°C/min，电加热法的升温速率只有9°C/min，由此可见，升温速率越快，再生效率越高。在能耗对比方面，在确保再生率达到99%以上的前提下，微波再生法的能耗为13.5kJ/g，而电加热法的能耗为40.5kJ/g，相当于微波加热法的3倍。比较加热的时间可知，对于载甲苯的松木和麦秸活化生物质炭，恒功率（600W）微波再生法需要的时间最短为3min，其次为恒温（150°C）微波再生法为30min，最长的则是电加热法为120min。对于丙酮，恒功率（600W）微波再生法需要的时间最短为1min，其次为恒温（100°C）微波再生法为10min，最长的则是电加热法为60min。微波再生前后，活化生物质炭的比表面积、孔隙结构和表面官能团并没有明显变化。因此，微波再生法是一种节能、环保、有效的活化生物质炭再生方法，具有工业化应用的良好潜质。更多还原

【Abstract】 This paper describes the activation of pine and wheat straw biochar with KOH andmicrowave heating to obtain a product with high adsorption capacity for toluene and acetone.For this purpose, a microwave activation process for the preparation of activated biochar wasdeveloped and the effects of various KOH/biochar mass ratios on the structural properties andadsorption capacity of activated biochar were investigated. The preparation conditions, such asthe microwave power, the KOH/biochar ratio and the microwave heating time were investigated.The properties of the produced activated carbon were characterized using iodine number as wellas BET surface area and pore size distribution. Adsorption capacity for toluene/acetone onactivated biochar was obtained using breakthrough curves at low concentrations and a sorptionanalyzer at high concentration. The adsorption isotherms were fitted with theDubinin–Radushkevich (DR) model. In the regeneration, this paper presents a comparison ofmicrowave and conductive heating regeneration of toluene and acetone from activated biochar,in terms of regeneration ratio, desorption rate, heating time and energy consumption. Thefollowing conclusions may be drawn:(1) The optimized preparation conditions for activated biochar are that carbonization timeis2h and humid N2during the carbonization period; and microwave power, microwave heatingtime are600W and30min, respectively, as well humid N2during the microwave activationperiod. As for pine and wheat straw activated biochar, the BET surface area increased from1053m2/g and942m2/g to1250m2/g and2044m2/g with an increase in the KOH/biochar massratio from0.5to3.0, respectively; micropore surface area and micropore volume showedsimilar increases. Most of the pores developed in the activated biochar samples are within themicroporous range, indicating that the microporosity is independent of the KOH/biochar massratio. Microporosity was present due to the initial porosity of the precursor material (e.g. thetracheids) that aided KOH impregnation into the biochar and to chemical reactions betweenKOH and biochar during microwave heating. The FTIR spectra of biochar activated by microwave heating and KOH with ratio of3.0showed bands of–OH, C-H, C=O, and=CH2functional groups.(2) For toluene at200ppmv, the adsorption capacities of pine and wheat straw activatedbiochar increase from22.3%and17.1%to47.6%and32.7%as increasing of KOH/biocharratio from0.5-3.0. The same tendency of acetone at200ppmv, the adsorption capacities of pineand wheat straw activated biochar increase from15.4%and14.0%to21.7%and17.8%asincreasing of KOH/biochar ratio from0.5-3.0. Adsorption capacity was increased according tothe increment of inlet concentration from100to300ppmv. For toluene, adsorption capacity ofpine and wheat straw activated biochar at KOH/biochar ratio of3.0was increased from43.4%and20.2%to51.3%and24.4%, respectively with the increasing of inlet concentration from100to300ppmv. For acetone, adsorption capacity of pine and wheat straw activated biochar atKOH/biochar ratio of3.0was increased from17.8%and12.7%to24.4%and21.4%,respectively. Higher KOH/biochar mass ratios resulted in longer breakthrough times andproduced more micropores, leading to a higher adsorption capacity. Furthermore, the fasterbreakthrough was and the slope of breakthrough curve was gradually increased. Breakthroughcurves on pine activated biochar and wheat straw activated biochar corresponding toKOH/biochar mass ratios of0.5,1.5, and3.0, respectively. Pine activated biochar atKOH/biochar mass ratios of0.5,1.5, and3.0took8,12, and18hours, respectively, to reachbreakthrough during the toluene adsorption process. Wheat straw activated biochar atKOH/biochar mass ratios of0.5,1.5, and3.0took4.5,5.5and6hours, respectively. Theadsorption capacity and breakthrough time decreased as the adsorption temperature increasedfrom25to45℃. As for toluene, the adsorption capacity of pine and wheat straw activatedbiochar at KOH ratio of3.0decreased from47.6%and32.7%to25.0%and19.2%,respectively, when the temperature increased from25to45℃; for acetone, the adsorptioncapacity of pine and wheat straw activated biochar at KOH ratio of3.0decreased from21.7%and17.7%to15.3%and12.0%, respectively, when the temperature increased from25to45℃.(3) Adsorption capacity at high concentration was increased according to the increment ofKOH/biochar ratio from0.5to3.0. For toluene, adsorption capacity of pine and wheat strawactivated biochar were increased from32.2%and20.2%to71.9%and45.9%, respectively,when KOH/biochar ratio was increased from0.5to3.0. For acetone, adsorption capacity ofpine and wheat straw activated biochar were increased from24.7%and22.7%to57.8%and36.4%, respectively, when KOH/biochar ratio was increased from0.5to3.0. An increase oftemperature from25to45℃, the toluene/acetone adsorption capacity from the adsorptionisotherm of activated biochar at high concentration was decreased. DR Dubinin–Radushkevich(DR) model can be used to fit toluene/acetone adsorption isotherm data for pine and wheat straw activated biochars at various temperatures of25,35,45℃.(4) The adsorption capacity of activated biochar is not influenced by successivemicrowave swing regeneration. For toluene, it was found that the adsorption capacities of pineand wheat straw activated biochar are about445mg/g and231mg/g, respectively, and5cyclesover repetitive microwave heating did not reduce or increase adsorption capacities. For acetone,it showed the adsorption capacities of pine and wheat straw activated biochar are about330mg/g and185mg/g, respectively. A increasing of microwave output power, flow rate of purgegas, and humidity of purge gas, desorption rates using microwave heating was increased. Theoptimized parameters of microwave output power, flow rate of purge gas, and humidity ofpurge gas for microwave heating under this experiment condition are:600W,1L/min and humidN2. Comparison of pine and wheat straw activated biochar loaded with toluene/acetone onadsorption capacity, regeneration ratios, temperature rats, desorption rates, power and energyconsumption, microwave regeneration has been demonstrated on a lab-scale to be a rapider,more efficient and simpler regeneration technique than that of conductive regeneration method.The results showed that the regeneration ratio reached99.7%and99.8%under3min and1minof microwave heating with constant power of600W, when the pine and wheat straw activatedbiochar was loaded with toluene and acetone, respectively. For microwave heating withconstant temperature, it took30min and10min for pine activated biochar loaded with tolueneand acetone, respectively, while it took only10min and5min for activated activated biocharloaded with toluene and acetone, respectively. However, for conductive heating, it took120minand60min for both pine/wheat straw activated biochar loaded with toluene and acetone,respectively. To achieve99.6%desorption, microwave heating requires13.5KJ/g and9KJ/g fortoluene and acetone, while conductive heating requires40.5KJ/g and31.5KJ/g for toluene andacetone. Therefore, the energy consumption of conductive heating was3times higher than thatof microwave heating for the desorption of toluene and acetone. The BET surface area,micropore volume, micropore surface area and surface functional group of the microwave andconventional treated samples was found unchanged. Therefore, microwave heating withconstant power is recognized as the most efficient and feasible regeneration method foractivated biochar saturated with toluene or acetone.更多还原