摘要
采用蒸汽爆破技术对杨木进行预处理,以蒸汽爆破前后的杨木为原料制备多孔炭,探究蒸汽爆破对杨木基多孔炭成孔性能的影响。采用N2吸附-脱附曲线、扫描电子显微镜和傅里叶变换红外光谱仪对制得的多孔炭进行表征。结果表明,以蒸汽爆破后的杨木为原料、添加尿素制备的多孔炭PCSE-N的比表面积最高,为3002
随着我国纺织及印染行业的发展,染料废水的排放量逐渐增加,给环境和人类健康造成巨大威
因此,对于成分复杂的植物生物质原料来说,如何简单、廉价地改变原料的组分,使之有利于多孔炭的成孔,是科研人员的研究方向之
本研究以提高多孔炭对亚甲基蓝的吸附性能为目标,采用蒸汽爆破技术对杨木进行预处理,探究蒸汽爆破对杨木基多孔炭成孔性能的影响。通过调控工艺参数,采用尿素协同KOH进行活化,从而实现了超高比表面积多孔炭的制备,且制备的多孔炭中含有丰富的介孔和大孔结构,可以实现对亚甲基蓝分子的高效吸附。
亚甲基蓝、KOH、尿素、盐酸均为分析纯,购于国药集团化学试剂有限公司。
实验所用杨木片取自山东太阳纸业有限公司,平均尺寸约为30 mm×30 mm×5 mm。实验中对木片进行清理以去除泥土,风干后置于自封袋中平衡水分,控制水分为35%左右。
取400 g杨木原料(NP,绝干质量)置于容量为5 L的汽爆实验台反应容器中,通入水蒸气,控制反应温度为217 ℃(压力约2.2 MPa)。在温度恒定的通蒸汽条件下保温7 min后,瞬间释放压力,然后从收集仓内收集蒸汽爆破后的杨木纤维(SE)。采用美国能源实验室报道的方
称取一定质量的KOH于50 mL烧杯中,加入一定体积的去离子水溶解,然后将40~60目的NP和SE分别与KOH按1∶1(w/w)比例充分混合,室温下反应2 h后置于105 ℃的烘箱中烘干备用。将烘干后的NP与KOH混合物、SE与KOH混合物置于小型管式炉中,在400 ℃下进行低温预炭化,炭化一定时间后得到预炭化产物,标记为P400-NP和P400-SE。
称取一定质量的尿素分别与两种预炭化产物按1∶1(w/w)比例充分混合,然后置于小型管式炉中进行高温炭化,在高温条件下保温1 h,得到黑色粉末样品后进行洗涤,即先用1 mmol/L盐酸溶液浸泡,然后采用蒸馏水进行多次洗涤至中性,最后在105 ℃的烘箱中干燥后得到多孔炭,分别命名为PCNP-N和PCSE-N。以不添加尿素的多孔炭作为对照样,分别命名为PCNP和PCSE。
取15 mL初始浓度为1000 mg/L的亚甲基蓝溶液于锥形瓶中,加入10 mg多孔炭,然后置于恒温摇床中,以120 r/min的速度振荡,温度控制为25 ℃,一段时间后,取出样品过滤得到清液,利用UV-vis分析滤液中亚甲基蓝的浓度,并利用
(1) |
式中,C0、Ce分别为亚甲基蓝初始浓度和达到吸附平衡时的浓度,mg/L;V为亚甲基蓝溶液体积,mL;m为多孔炭的质量,g。
利用准一级动力学模型和准二级动力学模型对吸附反应进行动力学拟合,比较其相关系数
准一级动力学模型:
(2) |
准二级动力学模型:
(3) |
式中,K1、K2分别为准一级、准二级动力学速率常数,g/(mg·min);t为反应时间,min;qt为t时刻的吸附量,mg/g。
经217 ℃、7 min蒸汽爆破处理后,杨木三大组分的含量发生了明显变化,结果如
样品 | 纤维素含量/% | 半纤维素含量/% | 木质素含量/% |
---|---|---|---|
NP | 44.1 | 19.4 | 27.8 |
SE | 57.5 | 3.8 | 17.8 |

图1 PCNP(a)、PCNP-N(b)、PCSE(c)和PCSE-N(d)的SEM图
Fig. 1 SEM images of PCNP (a), PCNP-N (b), PCSE (c), and PCSE-N (d)
4种多孔炭的N2吸附-脱附等温线及孔径分布曲线如


图2 多孔炭N2吸附-脱附等温线(a)和孔径分布曲线(b)
Fig. 2 Curves of N2 adsorption-desorption isotherm (a) and pore size distribution (b)
从
样品 | 总比表面积/ | 孔体积/c | 微孔孔体积/c | 介孔孔体积/c | 介孔孔体积占比/% |
---|---|---|---|---|---|
PCNP | 928.3 | 0.5947 | 0.4171 | 0.1776 | 29.86 |
PCSE | 1169 | 0.6073 | 0.4011 | 0.2062 | 33.95 |
PCNP-N | 2698 | 1.535 | 0.6932 | 0.8218 | 53.54 |
PCSE-N | 3002 | 1.911 | 0.4880 | 1.423 | 74.46 |
采用FT-IR对4种多孔炭进行表征,探究其官能团和结构,结果如

图3 多孔炭的FT-IR谱图
Fig. 3 FT-IR spectra of porous carbons

图4 不同多孔炭对亚甲基蓝(1000 mg/L)的平衡吸附量
Fig. 4 Equilibrium adsorption capacity of methylene blue (1000 mg/L) by different porous carbons

图5 亚甲基蓝初始浓度和吸附时间对PCSE-N吸附量的影响
Fig. 5 Effects of initial concentration of methylene blue and adsorption time on adsorption capacity of PCSE-N
采用准一级和准二级动力学模型拟合PCSE-N对亚甲基蓝的吸附过程,利用动态方程对数据进行非线性回归分析,结果分别如


图6 准一级动力学模型(a)和准二级动力学模型(b)的线性拟合
Fig. 6 Linear fitting of pseudo-first-order kinetic model (a) and pseudo-second-order kinetic model (b)
动力学模型 | 参数 | 亚甲基蓝初始浓度/mg· | ||||
---|---|---|---|---|---|---|
1000 | 1200 | 1400 | 1600 | 1800 | ||
准一级动力学 |
qe/mg· | 1465 | 1630 | 1675 | 1668 | 1726 |
qe, cal/mg· | 274.4 | 176.4 | 257.4 | 295.1 | 199.5 | |
K1/g·m | -0.03217 | -0.04844 | -0.05485 | -0.06695 | -0.05944 | |
| 0.8468 | 0.6814 | 0.6250 | 0.7407 | 0.7430 | |
准二级动力学 | qe | 1465 | 1630 | 1675 | 1668 | 1726 |
qe, cal/mg· | 1477 | 1630 | 1695 | 1689 | 1735 | |
K2/g·m | 0.00068 | 0.00061 | 0.00059 | 0.00059 | 0.00058 | |
| 0.9995 | 0.9997 | 0.9999 | 0.9999 | 0.9999 |
根据吸附体系的性质和类型选择Langmuir和Freundlich模型拟合PCSE-N对亚甲基蓝的吸附等温线,结果如


图7 Langmuir模型(a)和Freundlich模型(b)的线性拟合
Fig. 7 Linear fitting of Langmuir model (a) and Freundlich model (b)
吸附模型 | 吸附参数 | |
---|---|---|
Langmuir |
qL/mg· | 1720 |
KL/L·m | 0.198 | |
| 0.9992 | |
Freundlich |
KF/m | 1339 |
n | 25.48 | |
| 0.8989 |
采用蒸汽爆破技术对杨木进行预处理,以蒸汽爆破前后的杨木为原料制备多孔炭,并采用尿素协同KOH活化多孔炭,探究蒸汽爆破和添加尿素对杨木基多孔炭成孔性能的影响,主要结论如下。
(1)采用相同方法制备多孔炭时,以蒸汽爆破后杨木为原料制备的多孔炭的比表面积均高于杨木原料制备的多孔炭。其中,以蒸汽爆破后的杨木为原料、添加尿素制备的多孔炭PCSE-N的比表面积为3002
(2)当亚甲基蓝初始浓度为1800 mg/L、吸附时间为60 min时,PCSE-N对亚甲基蓝的吸附量高达1726 mg/g。
(3)通过吸附动力学分析可知,准二级动力学模型更好地拟合了PCSE-N对亚甲基蓝的吸附,说明该吸附过程以化学吸附为主;通过等温吸附模型分析可知,PCSE-N对亚甲基蓝的吸附过程与Langmuir模型更吻合,表明PCSE-N对亚甲基蓝的吸附为单层吸附。
参考文献
Boczkaj G, Fernandes A.Wastewater Treatment by Means of Advanced Oxidation Processes at Basic pH Conditions: a Review[J].Chemical Engineering Journal, 2017, 320: 608-633. [百度学术]
吕后鲁, 刘德启.工业废水处理技术综述[J].石油化工环境保护, 2006, 29(4): 15-19. [百度学术]
LYU H L, LIU D Q.Overview of Industrial Wastewater Treatment Technologies[J].Environmental Protection in Petrochemical Industry, 2006, 29(4): 15-19. [百度学术]
朱国婷, 邢献军, 汪家权, 等.酸预处理活性炭对废水染料的吸附研究[J].环境科学与技术, 2016, 39(S2): 166-171. [百度学术]
ZHU G T, XING X J, WANG J Q, et al.Adsorption Study of Wastewater Dyes on Acid Pretreated Activated Carbon[J].Environmental Science & Technology, 2016, 39(S2): 166-171. [百度学术]
孙荣泽, 耿龙龙, 公 超, 等.明胶衍生多孔炭的制备及其吸附亚甲基蓝性能研究[J].山东化工, 2019(5): 221-223. [百度学术]
SUN R Z, GENG L L, GONG C, et al.Preparation of Gelatin-derived Porous Carbon and Its Performance in Adsorption of Methylene Blue[J].Shandong Chemical Industry, 2019(5): 221-223. [百度学术]
Crini G.Non-conventional Low-cost Adsorbents for Dye Removal: a Review[J].Bioresource Technology, 2006, 97(9): 1061-1085. [百度学术]
梁 波, 关 杰.吸附法处理亚甲基蓝研究[J].工业用水与废水, 2015, 46(1): 6-11. [百度学术]
LIANG B, GUAN J.Study on Treatment of Methylene Blue by Adsorption[J].Industrial Water & Wastewater, 2015, 46(1): 6-11. [百度学术]
Noked M, Soffer A, Aurbach D.The Electrochemistry of Activated Carbonaceous Materials: Past, Present, and Future [J].Journal of Solid State Electrochemistry, 2011, 15(7-8): 1563-1578. [百度学术]
Ruan C P, Ai K L, Lu L H.Biomass-derived carbon materials for high-performance supercapacitor electrodes [J].RSC Advances, 2014, 4(58): 30887-30895. [百度学术]
Correa C R, Otto T, Kruse A.Influence of the Biomass Components on the Pore Formation of Activated Carbon[J].Biomass and Bioenergy, 2017, 97: 53-64. [百度学术]
Wang H M, Liu Z, Hui L F, et al.Biomass-derived Porous Carbon Materials for Supercapacitor Electrodes: A Review[J].Paper and Biomaterials, 2020, 5(2): 60-75. [百度学术]
亢 能, 刘 忠, 惠岚峰.木质纤维原料生产燃料乙醇的蒸汽爆破预处理技术[J].酿酒科技, 2011(11): 17-20. [百度学术]
KANG N, LIU Z, HUI L F.Steam Blasting Pretreatment Technology for Fuel Ethanol Production from Wood Fiber Feedstock[J].Liquor-Making Science & Technology, 2011(11): 17-20. [百度学术]
Sluiter A, Hames B, Ruiz R O, et al.Determination of Structural Carbohydrates and Lignin in Biomass[R].USA: National Renewable Energy Laboratory, 2008. [百度学术]
陈丽群, 张红杰, 朱荣耀, 等.木质素/Fenton污泥基磁性活性炭对亚甲基蓝和苯酚吸附特性的研究[J].中国造纸, 2020, 39(5): 23-28. [百度学术]
CHEN L Q, ZHANG H J, ZHU R Y, et al.Study on Adsorption Behaviors of Methylene Blue and Phenol by Lignin/Fenton Sludge Based Magnetic Activated Carbon[J].China Pulp & Paper, 2020, 39(5): 23-28. [百度学术]
Li L, Wu M, Song C, et al.Efficient Removal of Cationic Dyes via Activated Carbon with Ultrahigh Specific Surface Derived from Vinasse Wastes[J].Bioresource Technology, 2021, DOI: 10.1016/j.biortech.2020. [百度学术]
曾宪阳, 李 沅, 陈 宪, 等.淀粉基多孔炭材料制备及其亚甲基蓝吸附性能[J]. 大连工业大学学报, 2020, 39(6): 434-438. [百度学术]
ZENG X Y, LI Y, CHEN X, et al.Preparation of Porous Carbon Material and Its Adsorpting for Methylene Blue[J].Journal of Dalian Polytechnic University, 2020, 39(6): 434-438. [百度学术]
刘源源, 刘 昕, 王 萌, 等.果糖基碳微球的制备及其吸附性能研究[J].中国造纸学报, 2022, 37(1): 1-7. [百度学术]
LIU Y Y, LIU X, WANG M, et al. Study on Preparation of Fructose-based Carbon Microspheres and Their Adsorption Properties [J].Transactions of China Pulp and Paper, 2022, 37(5): 1-7. [百度学术]
Tang X, Ran G, Li J, et al.Extremely Efficient and Rapidly Adsorb Methylene Blue Using Porous Adsorbent Prepared from Waste Paper: Kinetics and Equilibrium Studies[J].Journal of Hazardous Materials, 2021, DOI: 10.1016/j.jhazmat.2020.123579. [百度学术]
Yao X, Ji L, Guo J, et al.Magnetic Activated Biochar Nanocomposites Derived from Wakame and Its Application in Methylene Blue Adsorption[J].Bioresource Technology, 2020, DOI: 10.1016/j.biortech.2020.122842. [百度学术]
魏同业.生物质基多孔炭材料的制备与应用[D].湘潭: 湘潭大学, 2016. [百度学术]
WEI T Y.Preparation and Application of Biomass-based Porous Carbon Materials[D].Xiangtan: Xiangtan University, 2016. [百度学术]
Chen P, Wang L K, Wang G, et al.Nitrogen-doped Nanoporous Carbon Nanosheets Derived from Plant Biomass: an Efficient Catalyst for Oxygen Reduction Reaction[J].Energy and Environmental Science, 2014, 7(12): 4095-4103. [百度学术]
Ding D, Ma L, Li X, et al.Porous Carbon Material Derived from Steam-exploded Poplar for Supercapacitor: Insights into Synergistic Effect of KOH and Urea on the Structure and Electrochemical Properties[J].Materials, 2022, DOI: 10.3390/ma15082741. [百度学术]
刘芳芳.生物质衍生掺杂碳基催化剂的制备及其氧还原电催化性能的研究[D].广州: 华南理工大学, 2015. [百度学术]
LIU F F.Preparation of Biomass-derived Doped Carbon-based Catalysts and Their Oxygen Reduction Electrocatalytic Performance[D].Guangzhou: South China University of Technology, 2015. [百度学术]
Zahoor A, Christy M, Hwang Y J, et al.Improved Electrocatalytic Activity of Carbon Materials by Nitrogen Doping[J].Applied Catalysis B: Environmental, 2014, 147: 633-641. [百度学术]
Akçay M.The Catalytic Acylation of Alcohols with Acetic Acid by Using Lewis Acid Character Pillared Clays[J].Applied Catalysis A: General, 2004, 269(1-2): 157-160. [百度学术]
Bezrodna T, Puchkovska G, Shimanovska V, et al.Pyridine-TiO2 Surface Interaction as a Probe for Surface Active Centers Analysis [J].Applied Surface Science, 2003, 214(1-4): 222-231. [百度学术]
Shi L, Zhang G, Wei D, et al.Preparation and Utilization of Anaerobic Granular Sludge-based Biochar for the Adsorption of Methylene Blue from Aqueous Solutions[J].Journal of Molecular Liquids, 2014, 198: 334-340. [百度学术]
Mohammadi S, Hosseinzadeh H.Quince Seed Mucilage Magnetic Nanocomposites as Novel Bioadsorbents for Efficient Removal of Cationic Dyes from Aqueous Solutions[J].Carbohydrate Polymers, 2015, 134: 213-221. [百度学术]
温俊峰, 刘 侠, 马向荣, 等.沙柳基磁性多孔炭的制备及其吸附亚甲基蓝性能研究[J].功能材料, 2021, 52(4): 184-191. [百度学术]
WEN J F, LIU X, MA X R, et al.Preparation of Magnetic Porous Carbon from Salix and Adsorption Properties for Methylene Blue[J].Journal of Functional Materials, 2021, 52(4): 184-191. [百度学术]
Liu S, Li J, Xu S, et al.A Modified Method for Enhancing Adsorption Capability of Banana Pseudostem Biochar Towards Methylene Blue at Low Temperature[J].Bioresource Technology, 2019, 282: 48-55. [百度学术]
Sun L, Chen D, Wan S, et al.Performance, Kinetics, and Equilibrium of Methylene Blue Adsorption on Biochar Derived from Eucalyptus Saw Dust Modified with Citric, Tartaric, and Acetic Acids[J].Bioresource Technology, 2015, 198: 300-308. [百度学术]