铁/炭凝胶颗粒高效吸磷以及位点能量分析

Iron/Biochar-based Gel Pellet for Highly Efficient Phosphate Removal and Analysis on Approximate Site Eenergy Distribution

以有机废弃物制备生物炭吸附水体中磷,同步实现了固废的高价值利用以及水体富营养化的抑制,然而缺乏表面修饰的生物炭对磷的吸附能力有限。该文以磁性Fe_(3)O_(4)作为生物炭表面修饰剂,并以壳聚糖为固化剂制备了高效的除磷凝胶颗粒。利用多种表征技术以及近似位点能量分布理论对磷的吸附机理进行了探讨,分析了吸附性能提升的关键原因。结果表明Fe_(3)O_(4)的加入极大地促进了磷的吸附,在293 K下,生物炭对磷的饱和吸附量由13.76 mg/g增加到87.79 mg/g。该凝胶颗粒对磷的吸附是一个吸热过程,准二级动力学模型以及Langmuir模型能够更好地描述磷在凝胶颗粒上的吸附行为。通过表征技术发现Fe与磷之间形成的沉淀是磷吸附的重要机制,孔隙填充、氢键结合和静电吸引同样是B-Fe-C吸附磷的机制。整体而言,化学吸附是主要的吸附机制。此外,对表面近似位点能量分布的分析发现,促进磷与吸附剂表面之间的亲和力以及增加表面高能吸附位点的密集分布是促进磷吸附的一种重要手段。研发的凝胶颗粒对于天然水体中的各种离子具有一定的抗干扰能力,在天然水体中仍能保持对磷的高效吸附,且易于再生。该研究为开发高效除磷吸附剂从设计机理上提供了重要的借鉴。

The biochar prepared by use of organic solid-waste is applied to adsorbing excessive phosphate in water bodies for controlling eutrophication,and at same time,realizing organic solid-waste effective reuse;however,the biochar common⁃ly prepared without any surface modification is limited in terms of phosphate adsorption performance.In this experimental study,magnetic Fe_(3)O_(4)is employed to modify the biochar,and then chitosan is used to make solid gel pellets,i.e.,the highly efficient phosphate adsorbent,and later testing of this iron/biochar-based gel pellets is conducted,which includes the employ⁃ment of several characterizations techniques as well as the theory of approximate site energy distribution to investigate the adsorption mechanism,and the elaborate analysis of the key to upgrading phosphate adsorption performance.As a result,the experimental study presents that it is by adding Fe_(3)O_(4)that the gel pellets increase the adsorption capacity from 13.76 mg/g(with biochar)to 87.79 mg/g(with Fe_(3)O_(4)-modified biochar)at 293 K;phosphate adsorption onto the gel pellets is an endother⁃mic process,and the experimental data about phosphate adsorption behavior could be well described by the pseudo-second and Langmuir model;besides,the characterization techniques reveal that the surface precipitation formed between Fe and phosphate is the primary mechanism,on the other hand,porous filling,hydrogen bonding and electrostatic attraction also play a role in the adsorption.On the whole,chemisorption is regarded as the primary adsorption mechanism;moreover,according to the analysis of approximate site energy distribution,it is revealed that the improvement of adhesion between the phosphate and adsorbent and the intensive distribution of high-energetic adsorptive sites is a critical measure to boost phosphate adsorp⁃tion amount;besides,the iron/biochar-based gel pellet shows a certain flexibility against varied external ions in the water,maintaining high adsorption property in natural water body,and is easy to be recycled.So it is expected that the result of the study would provide a guideline for developing high-efficient phosphate removal adsorbent.