Deep insights on arsenic speciation and partition in coal-fired particles from micro to nano size

Abstract

Inhalable arsenic laden particles generated from coal combustion are toxic and carcinogenic, deep insights in those arsenic laden particles are of both fundamental and practical significance for abating arsenic emissions. A comprehensive investigation on arsenic partition in particles from bulk fly ash to nano-size single particles have been presented. More than 1000 arsenic-containing single particles in size from 60 nm to 170 nm have been effectively acquired by using single particle Inductively Coupled Plasma equipped with Time-of-Flight Mass Spectrometer (spICP-TOF-MS). More than 90 % of those arsenic containing single particles are mixtures of various elements. Strong associations among As and Sn, Sb, Pb can be identified in nano-size particles, and the association frequencies are more than 0.8. Arsenic in particles from PM0.03 to PM10 is mostly occurring as As5+. Species, such as Pb, Sn, Sb, Na, Fe, and Ca have strong associations with As in particles from nano-size grains to micro-size particles. Semi-volatile elements, such as Pb, Sn, and Sb, are highly suspected to be heterogeneous nucleated and condensed together with As to form the nano-size grains, which is probably the dominating pathway for As accumulations in PMs. Secondary reactions among Na-As, Fe-As, and Ca-As in flue gas will be occurred thus determining arsenic transformation and speciation in PMs together with the growth of As laden particles. Ca and Fe are responsible for inducing As specie to As5+ in PMs. Ca-As5+ is more likely to be presenting in particles from PM0.03 to PM2.5, while Fe-As5+ is likely to be occurring in particles from PM2.5 to PM10.