| 钟旋,蒋恩臣,卢璐璎,高振楠,王明峰.稻壳炭的制备及其对尿素态氮的吸附特性[J].农业环境科学学报,2021,40(10):2150-2158. |
| 稻壳炭的制备及其对尿素态氮的吸附特性 |
| Preparation of rice husk biochar and adsorption characteristics of urea nitrogen |
| 投稿时间：2021-03-15 |
| DOI：10.11654/jaes.2021-0308 |
| 中文关键词: 热解 稻壳生物炭 尿素态氮 吸附动力学 吸附特性 |
| 英文关键词: pyrolysis rice husk biochar urea nitrogen adsorption kinetics adsorption characteristics |
| 基金项目:国家自然科学基金项目（51706074）；广东省林业科技创新项目（2020KJCX008） |
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| 中文摘要: |
| 为探索热解稻壳生物炭对尿素态氮的吸附特性，采用自制的无轴螺旋连续热解装置制备了热解温度分别为350、450、550℃和650℃的稻壳生物炭（RHB），研究了热解温度对RHB各项理化特性的影响规律，及其对水溶液中尿素态氮的吸附能力，并用吸附动力学模型和吸附等温线模型对尿素态氮的吸附过程进行拟合，结合吸附前后RHB的微观形貌特征，探讨了RHB对尿素态氮的吸附机制。结果表明，RHB的BET比表面积及孔容均随着热解温度的升高而逐渐增大，而平均孔径则逐渐减小；与热解温度为550℃和650℃制得的RHB相比，350、450℃制得的RHB保留了更多数量的酸性含氧有机官能团。650℃制得的RHB对尿素态氮的吸附能力更强（350℃和650℃ RHB的平衡吸附量分别为30.59 mg·g-1和33.16 mg·g-1），等温吸附模型拟合及吸附动力学拟合结果表明，RHB对尿素态氮的吸附过程可用Langmuir-Freundlich模型和Elovich模型描述，其对尿素态氮的吸附同时受到物理吸附和化学吸附的作用。RHB对尿素态氮的吸附过程为尿素分子首先通过自由扩散运动穿透液膜表面抵达RHB颗粒表面，并与RHB表面的官能团吸附位点发生化学吸附反应，然后尿素分子从RHB颗粒外表面进入到内部的复杂多孔结构中并被“封锁”于孔隙内部，之后逐渐趋于动态平衡。不同热解温度制得的RHB的吸附机制表现为低热解温度RHB通过表面含氧官能团与尿素分子形成氢键发生化学吸附，而高热解温度制得的RHB通过形成更多的复杂孔隙结构与尿素分子发生物理吸附。 |
| 英文摘要: |
| This study investigated the adsorption characteristics of urea nitrogen by using continuous pyrolysis biochar. Rice husk biochar (RHB)was prepared at 350, 450, 550℃, and 650℃ in a home-made shaftless spiral continuous pyrolysis device. The effects of pyrolysis temperature on the physical and chemical properties of RHB were studied, along with the adsorption capacity of urea nitrogen in an aqueous solution. The adsorption of urea nitrogen was fit using adsorption kinetic and adsorption isotherm models. The mechanism governing the adsorption of urea nitrogen by RHB was explored in combination with the micro-morphology characteristics of RHB before and after adsorption. Brunauer-Emmett-Teller specific surface area and pore volume of RHB increased with a rise in the pyrolysis temperature, while the average pore size decreased gradually. Compared with RHB prepared at 550℃ and 650℃, RHB prepared at 350℃ and 450℃ retained more acidic oxygen-containing organic functional groups. The adsorption capacity of RHB prepared at 650℃ for urea nitrogen was stronger(the equilibrium adsorption capacity of RHB at 350℃ and 650℃ was 30.59 mg·g-1 and 33.16 mg·g-1, respectively). The results of isothermal adsorption model and adsorption kinetics fittings showed that the adsorption of urea nitrogen by RHB could be described by the Langmuir Freundlich and Elovich models. The adsorption of urea nitrogen by RHB was simultaneously affected by physical adsorption and chemical adsorption. This study revealed the following adsorption process:Urea molecules first penetrate the surface of the liquid film through free diffusion to reach the surface of RHB particles. The molecules chemically adsorb with the adsorption sites of functional groups on the RHB surface. The urea molecules then move from the surface of the RHB particles to the inner complex porous structure and are "blocked" inside the pores. Ultimately, a dynamic equilibrium is established. Furthermore, the adsorption mechanism of RHB varied at different pyrolysis temperatures. At a low pyrolysis temperature, RHB forms hydrogen bonds with urea molecules through surface oxygen-containing functional groups and chemical adsorption. At a high pyrolysis temperature, RHB physically adsorbs to urea molecules through the formation of more complex pore structures. |
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