碳化改性硅藻土对四环素的吸附

为提高天然硅藻土对水体中有机污染物的吸附去除性能,以葡萄糖为碳源,通过一步低温热解法对天然硅藻土进行碳化改性。利用扫描电镜(SEM/EDX)、傅里叶红外光谱(FTIR)、X射线衍射(XRD)、Zeta电位等技术表征了碳化改性的硅藻土(CD₃₀₀)的结构特点和化学性质,并以四环素(TC)为目标污染物,对CD₃₀₀吸附TC的吸附动力学、吸附等温线和热力学进行研究分析。结果表明:在300℃下CD₃₀₀对TC的吸附效果最佳,较天然硅藻土的吸附性能提高了110.6%。表征结果证实了碳化产物成功负载至天然硅藻土表面且改性不会明显影响天然硅藻土的形貌结构。Elovich动力学模型表明,CD₃₀₀吸附TC以化学吸附为主。颗粒内扩散模型显示,CD₃₀₀对TC的吸附由液膜扩散和内扩散2个阶段控制,而内扩散阶段为主要的速率控制步骤。吸附等温线分析显示,Freundlich模型拟合效果更好(R2>0.966),表明吸附为多分子层吸附过程。热力学参数ΔG0<0、ΔH0>0和ΔS0>0,说明吸附过程为自发、吸热且混乱度增加。溶液初始pH值和离子影响强度实验证明,TC分子与CD₃₀₀间可能存在较强的外层结合,而静电作用在吸附过程中占据了主导作用。此外,碳化改性的硅藻土拥有良好的再生性能,表明其可作为一种高效吸附剂用于有机污染物的吸附去除。

PREPARATION OF MODIFIED DIATOMITE VIA CARBONIZATION AND ITS ADSORPTION PERFORMANCE ON TETRACYCLINE

To enhance the adsorption performance of the raw diatomite for organic pollutants in water, the modified diatomite(CD₃₀₀) was simply synthesized, using glucose as a carbon source, by low-temperature pyrolysis of glucose-immersed diatomite. CD₃₀₀ was characterized by SEM, EDX, FTIR, XRD, and Zeta potential, respectively. The adsorption kinetics, adsorption isotherms and adsorption thermodynamics of tetracycline(TC) as target pollutant were studied. It was observed that the modified adsorbents pyrolyzed at 300℃ performed better than other adsorbents for the TC adsorption, 110.6% higher than that of the raw diatomite. The characterization revealed that the carbonization products were successfully deposited on the surface of diatomite, and the morphology and structure of the raw diatomite were not significantly changed by carbonization modification. Based on correlation coefficient R2, Elovich kinetic model was better to fit the experiment results(R2>0.941), indicating that the adsorption on CD₃₀₀ was mainly chemisorption. Intra-particle diffusion model showed that the adsorption process was controlled by liquid film diffusion and internal diffusion, and the internal diffusion phase was the main rate control step. The adsorption isotherm analysis showed that the Freundlich model fitted the experimental data better(R2>0.966), indicating that the adsorption was multi-layer adsorption. The thermodynamic parameters, ΔG0<0, ΔH0>0 and ΔS0>0, indicated that the adsorption process was spontaneous, endothermic and the increase of disorder degree. The influence experiments of initial solution pH and ionic strength proved that there might be a strong outer-sphere association between TC molecules and CD₃₀₀, and electrostatic interaction was a dominant role in adsorption process. In addition, the favorable regeneration performance of CD₃₀₀ indicated that it could be used as an efficient adsorbent for organic pollutants adsorption removal.