HUALu-lu,HUANGXian-huai,QIANJing,et al.Characteristics of Iron Modified Biochar for Nitrate Nitrogen Adsorption in Water[J].China Water & Wastewater,2022,38(19):61-68.
铁改性生物质炭对水体中硝态氮的吸附特性
- Title:
- Characteristics of Iron Modified Biochar for Nitrate Nitrogen Adsorption in Water
- Keywords:
- biochar; Fe3+; modification; nitrate nitrogen; adsorption
- 摘要:
- 为提高生物质炭对水体中硝态氮（NO3--N）的吸附潜力，在高温限氧条件 （600 ℃）制备花生壳基生物质炭的基础上，利用铁（Fe3+）对其进行金属负载改性，通过批量吸附试验探讨其对NO3--N的吸附机制。结果表明，改性生物质炭（FeHBC）在铁炭质量比为0.672时的吸附效果最好，改性后对NO3--N的吸附能力得到显著提升（P<0.05），与未改性生物质炭（HBC）相比提高了近16倍；准二级动力学方程（R2=0.986）能较好地拟合FeHBC对NO3--N的吸附动力学过程，其吸附行为更加符合Freundlich等温吸附模型（R2= 0.994），热力学参数ΔG<0、ΔH>0、ΔS>0，表明FeHBC对NO3--N是自发的吸热过程，反应的自发性随温度升高而增大；酸性环境更有利于FeHBC对NO3--N的吸附。除此之外，还结合扫描电子显微镜（SEM）、X射线衍射光谱（XRD）、傅里叶变换红外光谱（FTIR）、零电荷点（pHPZC）等表征手段对其吸附机制进行深入分析。结果表明，FeHBC形成的多微孔粗糙颗粒表面为其提供了更多的吸附位点，吸附过程可能主要受Fe3+与含氧官能团络合沉淀反应的影响，与未改性相比其正电性增强，这一局部微结构的变化为提高生物质炭的吸附性能提供了理论支撑。
- Abstract:
- Peanut shell-based biochar was prepared at high temperature (600 ℃) and oxygen-limited condition, and then the biochar was loaded with iron (Fe3+) to improve its capacity for nitrate nitrogen (NO3--N) adsorption in water. The adsorption mechanism was investigated by batch experiment. The modified biochar (FeHBC) had the best adsorption performance when the mass ratio of iron to carbon was 0.672, and the adsorption capacity of NO3--N was significantly improved after modification (P<0.05), which was 16 times higher than that of the unmodified biochar (HBC). The pseudo-second-order kinetic model (R2=0.986) could well fit the kinetics of the modified biochar for NO3--N adsorption, and its adsorption behavior was more consistent with Freundlich isothermal adsorption model (R2=0.994). The thermodynamic parameters were as follows: ΔG less than zero, ΔH and ΔS both greater than zero, which showed that the adsorption of NO3--N by FeHBC was a spontaneous endothermic process, and the spontaneity of the reaction increased with the temperature increasing. The acidic environment was more conducive to the adsorption of NO3--N by FeHBC. In addition, the adsorption mechanism was analyzed by characterization methods such as scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and zero point of charge (pHPZC). FeHBC had more adsorption sites due to its porous rough particle surface. The adsorption process might be mainly affected by the complex precipitation reaction between Fe3+ and oxygen-containing functional groups. Compared with unmodified biochar, the positive electrical property of FeHBC was enhanced. This change of local microstructure provided theoretical support for improving the adsorption performance of biochar.
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