单组分生物炭对有机污染物的吸附性能及机理研究

Sorption is one of the most effective approaches to remediation/remission degradation-resistant organic contaminants in water and soil. Biochar is a kind of high carbon content soild which is derived from pyrolysis of biomass under high temperature with absence of oxygen. It can be used as an effective sorbent for organic contaminants due to its relatively high surface area, developed pore structure and abundant functional groups. However, the sorption capacities of different biomass derived biochar varied due to their different nature, especially the differences of cellulose, hemicellulose and lignin among different biomass, which also lead to the uncertainty of sorption mechanism. In this proposal, single component of plant biomass, including cellulose, hemicellulose and lignin are selected as feedstock to produce biochar at different pyrolytic temperatures. Surface and structure properties and physical-chemical nature of single component- derived biochar are characterized using multiple techniques. Sorption experiments are employed to quantify the sorption kinetics and isotherms using naphthalene, phenanthrene, trichloroethylene and tetracycline as representatives of degradation-resistant organic contaminants with different aromacity, hydrophobicity and polarity. Sorption parameters and properties of single component derived biochar are related with their surface properties and physical-chemical characteristics, and the sorption mechanisms are suggested based on these findings. Results obtaind from this proposal will benefit for better understanding the sorption mechanisms of biochar, and also provide theoretical basis for producing effective biochar for certain use.

吸附法是去除/缓解水体、土壤中难降解有机污染物的最有效途径之一。生物炭是生物质在高温缺氧环境下热解得到的高炭含量固体，有较大的比表面积，相对发育的孔结构以及丰富的表面官能团，且成本相对较低，可用于高效吸附去除难降解有机污染物。但由于生物质中三类主要组分纤维素、半纤维素、木质素含量差别大，导致制备的生物炭吸附能力各异，且难以明确吸附机理。本项目拟以生物质的单一组分纤维素、半纤维素、木质素为原料，在不同温度下热解制备生物炭，通过多种表征技术探明单组分生物炭的表面性质和结构特征，并以萘、菲、三氯乙烯、四环素作为典型难降解有机污染物的代表，研究单组分生物炭对不同极性、芳香性、疏水性有机污染物的吸附性能，并结合其结构特征，探明单组分生物炭的结构与其吸附性能间的关系，明确各组分炭化后对吸附的相对贡献及机理，深入揭示生物炭吸附有机污染物的机理，为有针对性地开发高性能生物炭提供理论依据。

本项目（21307122）在充分调研了生物炭的制备、表征及其在环境保护领域应用的基础之上，研究了以多种生物质以及纤维素、木质素等生物质单一组分为原料的生物炭对有机污染物的吸附性能及机理，主要获得了以下研究结果：.1. 生物质及其各单组分对有机污染物的吸附性能. 生物质可作为吸附有机污染物的天然吸附剂，对水中多环芳烃、亚甲基蓝等有机污染物有较强的吸附去除能力。但其中起主要吸附作用的是木质素等无定型组分，而纤维素等晶形组分吸附能力相对较弱。以菲为例，其木质素-水分配系数（7281 kg/L）约为纤维素-水分配系数（19.7 kg/L）的300余倍。.2. 制备并表征了单组分生物炭. 制备并表征了以纤维素、木质素为原料的单组分生物炭。在200~800℃范围内，发现随着碳化温度升高，各单组份生物炭颗粒尺寸逐渐减小，比表面积及孔体积显著增大，平均孔径减小，极性官能团减少，芳香性增强，组分结构发生明显变化。如纤维素在300℃以上晶体结构开始瓦解，逐渐转变成无定型结构，在700℃以上开始形成类似于石墨烯的稳定结构。.3. 研究了单组分生物炭的吸附性能及其构效关系. 研究了单组分生物炭对多环芳烃、亚甲基蓝等有机污染物的吸附性能。发现高温碳化的单组分生物炭对有机污染物的吸附性能显著高于低温单组分生物炭。高温单组分生物炭较大的比表面积、更丰富的空隙结构、更强的芳香性及疏水性是主要原因。如700℃碳化纤维素生物炭（CBC700）对萘的饱和吸附容量为84.1mg/g，而 300℃时（CBC300）仅为7.83 mg/g；700℃碳化木质素生物炭（LBC700）对亚甲基蓝的饱和吸附量为122mg/g，而300℃时（LBC300）仅为5.36mg/g。