氯化锌改性竹炭脱除单质汞的特性与机理分析

引言燃煤排放的汞是人为汞污染的主要来源之一,燃煤烟气中的汞主要以单质汞(Hg<'0>)、二价汞化合物(HgO、HgCl<,2>)和颗粒态汞3种形式存在,其中单质汞因其高挥发性、不溶于水等特点最难控制.由于汞的剧毒性,目前汞的排放控制已经引起广泛的研究[1-4],目前对汞的排放控制可分为燃烧前控制、燃烧中控制和尾部烟气控制3种,已有的研究发现活性炭吸附除汞是尾部烟气汞控制中最有前途的技术之一,美国目前已将该技术用于垃圾焚烧炉,并取得较好的效果.

Performance and mechanism for elemental mercury removal by bamboo charcoal modified by ZnCl2

Elemental mercury from coal combustion has become an increasingly environmental concern due to its high volatility and toxicity，and it has been found that activated carbon adsorption is an effective mercury-control method，but there exists high-cost limit. An important precursor for activated carbon is bamboo，a renewable bioresource，and bamboo charcoal(BC)may act as a low-cost sorbent used for mercury controlling. In this paper，the adsorptive potential of modified BC using ZnCl₂(Cl-BC)for elemental mercury was investigated in a bench-scale bed. Their pore structure and surface chemical properties were characterized by BET and XPS. The results suggested that Cl-BC had excellent adsorption potential for elemental mercury even at a relative higher temperature，and the enhancing-effect was more obvious with increasing Cl content. There was an optimum ZnCl₂ concentration for impregnation. The increase of performance of Cl-BC is probably due to the increase of active sites for mercury adsorption. The kind of Cl functional groups on the original and ZnCl₂-modified BC was found to be different，the latter is of the active site for mercury adsorption and oxidation，and for the former it is negligible. There is an optimum Cl content on the ZnCl₂-modified BC for elemental mercury removal，and mercuric chloride could be formed during mercury sorption.