挥发性有机化合物（VOCs）因其对生态环境和人类健康的严重危害而受到广泛关注。VOCs处理技术主要有焚烧法、冷凝法、吸附法和催化氧化法等，其中，吸附法以成本低、效果稳定、吸附剂可再生等优点被认为是一种高效、经济的处理手段。生物炭是一种绿色环保、廉价易得的炭质吸附材料，近年研究较多。介绍了生物炭基本吸附特性，对比不同制备和改性方法的优劣，重点分析了比表面积、孔隙特性和官能团等因素对生物炭吸附VOCs的影响，讨论了生物炭吸附VOCs的机理。生物炭原料来源广泛，原料种类、含量和成分差异都会影响生物炭的结构性质，从而影响其吸附能力。生物炭具有丰富的官能团和复杂的孔隙结构，一般采用常规热解方法在适当温度下制备的生物炭产率较高，结构性能较好。现阶段对生物炭改性效果显著的方法包括物理改性和化学改性，且生物炭改性后具备很高的VOCs吸附性能。通常生物炭比表面积越大，吸附性能越好；孔径越大，对大分子VOCs吸附更有利，但孔径远大于VOCs分子直径时，分子间吸附减弱；孔径越小，对小分子VOCs吸附更有利，但孔径过小也会增加VOCs的扩散阻力。较大的比表面积、适当的孔径以及针对被吸附VOCs气体极性进行改性使得生物炭具有较好的吸附性能。生物炭吸附VOCs的机理主要包括炭化区的吸附和非炭化有机物的分配，炭化温度小于300 ℃时分配作用为主要作用。比表面积越大，孔隙结构越发达，越有利于物理吸附；化学吸附一般通过生成化学键（如氢键、π—π键）产生作用。多组分VOCs会发生竞争吸附，且吸附亲和力较强的气体会取代吸附亲和力弱的气体。生物炭在相关领域的研究主要集中在实验室阶段，原料运输以及二次污染等问题使得生物炭吸附在工业上还未有成熟应用。提出未来生物炭吸附VOCs重点研究方向在于开发靶向改性生物炭、新型环保型生物炭复合材料、降低生物炭材料生产成本以及在分子水平上进行模拟研究。

Volatile organic compounds (VOCs) have attracted wide attention because of their serious harm to the ecological environment and human health. VOCs treatment technologies mainly include incineration,condensation,adsorption and catalytic oxidation,among which adsorption is considered to be an efficient and economical control strategy with its low cost,stable effect and renewable adsorbents. As a green,cheap and easily available carbon adsorption material,biochar has become a research hotspot.The basic adsorption characteristics of biochar were introduced,and the advantages and disadvantages of different preparation and modification methods were compared. The effects of specific surface area,pore characteristics and functional groups on VOCs adsorption by biochar were analyzed,and the mechanism of VOCs adsorption by biochar was discussed. The raw materials of biochar come from a wide range of sources,and the structural properties of biochar will be affected by the differences in the type,content and composition of raw materials,thus affecting its adsorption capacity. Biochar has rich functional groups and complex pore structure. Generally,the biochar prepared by conventional pyrolysis at appropriate temperature has high yield and good structural properties. At present,the significant modification methods of biochar include physical modification and chemical modification,and the modified biochar has high VOCs adsorption properties. In general,the larger the specific surface area of biochar is,the better the adsorption performance is; the larger the pore size is,the more favorable for the adsorption of macromolecular VOCs is,but when the pore size is much larger than the diameter of VOCs molecules,the intermolecular adsorption weakens; the smaller the pore size is,the more favorable for the adsorption of small molecules VOCs is,but too small pore size will also increase the diffusion resistance of VOCs. The biochar have better adsorption properties due to the larger specific surface area,appropriate pore size and targeted modification according to the polarity of the adsorbed VOCs gas. The adsorption mechanism of biochar on VOCs mainly includes the adsorption of carbonization zone and the distribution of non-carbonized organic matter. The distribution is the main mechanism when the carbonization temperature is less than 300 ℃. The larger the specific surface area is,the more developed the pore structure is,which is more conducive to physical adsorption; Chemisorption is generally achieved through the formation of chemical bonds (such as hydrogen bond,π—π). Multi-component VOCs will have competitive adsorption,and the gas with strong adsorption affinity will replace the gas with weak affinity. The research of biochar in related fields is mainly focused on the experimental stage in the laboratory. Due to the problems of raw material transportation and secondary pollution,biochar adsorption is not yet mature in industry. The future research direction of biochar adsorption of VOCs is developing targeted modified biochar,new environment-friendly biochar composites,reducing the production cost of biochar materials and conducting simulation research at the molecular level.

0 引言

1 生物炭材料制备与性能

   1.1 生物炭的基本特性

   1.2 生物炭的制备

   1.3 生物炭的改性

2 生物炭材料吸附VOCs的关键影响因素

   2.1 原材料的影响

   2.2 比表面积的影响

   2.3 孔隙特性的影响

   2.4 表面化学官能团的影响

   2.5 生物炭的再生能力

   2.6 吸附条件对生物炭吸附VOCs的影响

3 生物炭吸附VOCs的机理

   3.1 分配作用机制

   3.2 表面吸附作用机制

   3.3 其他微观机制

4 结语及展望