A review on common adsorbents for acid gases removal: Focus on biochar

Biochar, a product of pyrolysis of biomass, represents an attractive alternative to non-renewable or unsustainably sourced biomass as an adsorbent material for treating gaseous effluents. Biomass from residues associated with agricultural and forestry operation, otherwise considered waste material or a storage issues, represents a potential sustainable source of adsorbent. There are several adsorbents for removal of contaminants from gases including carbon based, silica based, and metal oxide based adsorbents; however, availability of feedstock, low cost, and potential high adsorption capacity distinguish biochar from other adsorbents. This review includes common sorbents for removal of contaminants from gas, biochar production methods, and compares biochar with activated carbon as one of the most common commercial adsorbents. Adsorption isotherms, mechanisms, and process systems for removal of acid gases such as CO2 and H2S by biochars have been comprehensively reviewed. The application of molecular modeling to describe adsorption by activated carbons and possible extension to biochar were studied. There is still a lack of published information in the molecular modeling of biochars, and using these models to understand the complex adsorbent mechanisms on the very heterogeneous surfaces of biochar (relative to commercial adsorbent materials such as activated carbons). Therefore, further research needs to fill these gaps to identify all potentials of this promising adsorbent.

生物炭是生物质热解的产物，作为一种用于处理气体排放物的吸附材料，它是不可再生或不可持续获取的生物质的一种有吸引力的替代品。来自农业和林业作业相关残余物的生物质，否则会被视为废弃物或存在储存问题，它代表着一种潜在的可持续吸附源。有多种用于去除气体中污染物的吸附剂，包括碳基、硅基和金属氧化物基吸附剂；然而，原料的可获取性、低成本以及潜在的高吸附能力使生物炭有别于其他吸附剂。这篇综述涵盖了用于去除气体中污染物的常见吸附剂、生物炭的生产方法，并将生物炭与作为最常见商业吸附剂之一的活性炭进行了比较。对生物炭去除二氧化碳和硫化氢等酸性气体的吸附等温线、机理和工艺系统进行了全面综述。研究了分子模拟在描述活性炭吸附方面的应用以及可能对生物炭的拓展。在生物炭的分子模拟方面仍然缺乏已发表的信息，并且利用这些模型来理解生物炭这种非常不均匀的表面（相对于活性炭等商业吸附材料）上复杂的吸附机理。因此，需要进一步的研究来填补这些空白，以确定这种有前景的吸附剂的所有潜力。