生物质炭对有机污染物的吸附及机理研究进展

生物质炭是一种利用废弃生物质材料在缺氧或厌氧环境中热化学转换制备的多孔级富碳固体材料。因其吸附能力强,制备原料来源广泛,生产成本低且环境友好等优点受到学术界越来越多的关注。探究生物质炭对有机污染物的吸附机理和规律,对于评估其环境行为和应用价值至关重要。着重综述了目前研究报道的生物质炭吸附有机污染物的吸附机理,包括分配作用、表面吸附作用和孔隙截留等。一般低温生物质炭对非极性有机物的吸附机制以分配作用为主,这种非竞争性吸附机理可以解释高浓度有机污染物在生物质炭上的吸附过程。表面吸附是一种非线性竞争性吸附作用,是有机污染物在生物质炭表面有效吸附位点上形成静电作用或通过氢键、离子建、π-π相互作用等结合的过程。孔隙截留是另一种生物质炭固定有机污染物的微观机制,有机污染物在孔隙内部的分配和吸附也是生物质炭吸附能力的重要体现。而在实际复杂的污染环境中,各类生物质炭对有机污染物的吸附过程需要多种机制共同解释。此外,本文对吸附机制的影响因素进行了分析和总结,生物质炭自身理化特性决定了其应用价值,生物质炭的性质与有机污染物的极性、芳香性和分子大小等相匹配才能更好地实现吸附固定,不同的吸附环境如吸附介质、p H和共存离子等也会对吸附机制和吸附效果产生影响。最后,文章进一步探讨了生物质炭吸附有机污染相关研究未来应着重解决的问题,以及生物质炭在有机污染土壤修复中的应用前景。

A Review of Researches on Biochar Adsorbing Organic Contaminants and its Mechanism

Biochar is a kind of porous and carbon-rich material prepared out of waste biomass through pyrolyzation anaerobically or aerobically. Thanks to its high adsorption capacity,handy resources, low preparation cost and environment-friendliness,biochar has aroused more and more attention among the academic circles. Knowledge about mechanism and rules of biochar adsorbing organic contaminants is crucial to proper evaluation of its environmental behaviors and application value. This article reviewed with emphasis reports available on mechanisms of biochar adsorbing organic pollutants,such as partition,surface adsorption,pore interception,etc. Generally speaking,biochar prepared at low temperature adsorbs non-polar organics mainly via partitioning. This non-competitive adsorption mechanism can be used to explain the process of biochar adsorbing pollutant high in concentration. Surface adsorption is a kind of competitive sorption mechanism. Organic contaminants caught on the effective sites on the surface of biochar are adsorbed via electrostatic interaction or hydrogen bonding,ionic bonding,π-electron donor-acceptor(π-π EDA), etc. Pore interception is another microscopic mechanism of biochar adsorbing organic pollutants. Partitioning and adsorption of organic pollutants inside the pores is also an important portion of the biochar adsorption capacity. Both polar and/or non-polar organic contaminants can be sorbed on biochar via pore interception. In fact,the mechanisms of biochar adsorbing organic compounds are various with one dominated and additional other mechanisms also occurred. In addition,this paper analyzed and summarized influencing factors of mechanisms of biochar adsorbing organic contaminants. Physico-chemical properties of biochar including high specific area,well-developed porosity,rich polar functional groups and stable aromatic structure are essential to determine the application value of this super-sorbent. Only biochar with properties matchable to organic contaminants in polarity,aromaticity,molecular size can be used to bring their adsorption capacity into full play. Sorption environment such as pH,medium and co-existing ions is also an important factor affecting adsorption effect of biochar. All account for the complex process of biochar adsorbing organic compounds. However,the researches reported in the literature are found to have some problems. For example,some of them remained on the stage of laboratory and little is reported in the literature on using experimental methods to probe mechanisms of biochar adsorbing organic compounds. At the end,the article brought forth solutions to the existing problems and described prospects of the application of biochar in remediation of organic polluted soils in future.