基于密度泛函的铁基改性生物焦汞吸附与再生机理  

Mercury adsorption and regeneration mechanism of iron-based modified biochar based on density functional theory

作　　者：秦舒宁 樊保国[1] 贾里 范浩东 金燕[1] QIN Shuning;FAN Baoguo;JIA Li;FAN Haodong;JIN Yan(College of Electrical and Power Engineering,Taiyuan University of Technology,Taiyuan 030024,China)

机构地区：[1]太原理工大学电气与动力工程学院,山西太原030024

出　　处：《煤炭学报》2022年第7期2779-2789,共11页Journal of China Coal Society

基　　金：国家自然科学基金资助项目(U1910124);山西省高等学校科技创新资助项目(2020L0073)。

摘　　要：为进一步探究生物焦汞吸附特性与提升生物焦汞吸附性能,采用共沉淀法制备以生物基为载体的铁基改性生物焦脱汞剂,基于密度泛函理论,结合多种表征和计算手段,通过高价金属离子、晶格氧与氧空位结合,构建了缺陷型碳环掺杂金属的铁基改性生物焦分子模型,并对Hg^(0)在铁基改性生物焦表面吸附的反应路径进行研究,确定了Hg^(0)在改性生物焦表面的吸附反应活化能垒和决速步骤,进一步揭示了Hg-Fe10%-BC的反应机制和相应成键机理。在验证不同铁基负载比率失活生物焦再生可行性的基础上,揭示了失活生物焦再生反应机理,探究了反应条件和含氧官能团对吸附过程的影响机制。研究发现,Hg^(0)在铁基改性生物焦表面的吸附过程共包含扩散与吸附氧化阶段,其中Hg^(0)作为Lewis碱易与作为Lewis酸的改性生物焦发生非均相氧化反应,而HgO则为Hg^(0)吸附后的主要赋存形态;带有电子的氧空位为吸附过程的化学吸附位点,均匀分散在生物焦中的金属离子与对应氧化物中的晶格氧为反应过程中的氧化位点;含氧官能团通过自身酸碱程度进一步影响生物焦汞吸附性能;失活生物焦再生受到氧链长度增加的限制,最大汞吸附效率降至改性生物焦一次汞吸附效率的90%;定量揭示了铁基改性生物焦Hg^(0)的吸附机理与失活改性生物焦的再生机制,为脱汞方法的优化提供理论依据。To further explore the adsorption characteristic of biochar mercury and improve the adsorption performance of biochar mercury,the iron-based modified biochar mercury remover with bio-based as the carrier is prepared by co-precipitation method.Based on the density functional theory(DFT)and a variety of characterization and calculation methods,through the combination of high valence metal ions,lattice oxygen and oxygen vacancy,the metal doped defective carbon ring is constructed as the molecular model of iron-based modified biochar.The reaction path of Hg^(0)on the surface of iron-based modified biochar is studied.The activation energy barrier and the rate determining step of Hg^(0)adsorption on the surface of modified biochar are determined.The reaction mechanism of Hg-Fe10%-BC and the corresponding bonding mechanism are further revealed.In addition,on the basis of verifying the feasibility of regeneration of inactivated biochar with different iron-based loading ratios,the regeneration reaction mechanism of inactivated biochar is revealed and the influence of reaction conditions and oxygen-containing functional groups on the adsorption process is explored.It is found that:The adsorption process of Hg^(0)on iron-based modified biochar included diffusion and adsorption stages.Hg^(0),as a Lewis base,is easy to react with the modified biochar as a Lewis acid,while HgO is the main occurrence form after Hg^(0)adsorption;The oxygen vacancy with electrons is the chemical adsorption site in the adsorption process,and the metal ions and the lattice oxygen in the corresponding oxides uniformly dispersed in the biochar are the oxidation sites in the reaction process;The oxygen-containing functional groups further affect the mercury adsorption performance of biochar through their own acid-base degree;The regeneration of inactivated biochar is limited by the length of oxygen chain.And the maximum mercury adsorption efficiency decreases to 90%of that of modified biochar.The adsorption mechanism of Hg^(0)on iron-based modified bi

关 键 词：生物焦 铁基改性 共沉淀法 缺陷型碳环 失活再生 氧化机制 

分 类 号：TQ424[化学工程] X701[环境科学与工程—环境工程]