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Abstract The multistep solvent extraction is an effective way for evaluating the original structure of coal, however, it is seldom used for studying the Hg distribution in coal and its release behavior during mild pyrolysis process. In this work, the Guizhou bituminous coal was divided into organic-rich class C 1 and minerals-rich class C 2 , the C 1 was further subdivided into 4 groups (EG 1 –EG 4) using multistep solvent extraction method. The Hg species in different samples and their fate during pyrolysis was investigated using sequential chemical leaching methods and temperature-programmed experiments. The results showed the dominant Hg forms in different samples are quite different, the HCl-soluble and HNO 3 -soluble Hg are the dominant forms in C 2 , while organic matrix combined Hg is the most abundant form in C 1 , EG 1 and EG 2 samples. The Hg contents in EG 1 to EG 4 groups are in the order of EG 4 < EG 3 < EG 2 < EG 1 , and have little correlation with the total sulfur contents. The thermal stability of different Hg species are quite distinct, the Hg in EG 1 sample is the most thermal unstable and almost released completely before 400 °C. The Hg release of GZB, C 1 , and C 2 are similar, >60% and 95% of Hg in the three samples can be released at 400 °C and 600 °C, respectively. The Hg-OM+ combined with aromatic clusters in EG 2 is difficult to decompose during pyrolysis process, it mainly released in the temperature range of 400–800 °C. Except the Hg-OM+ combined with aromatic clusters in EG 2 , >95% of Hg can be released before 600 °C for other samples. When the heating rate increased from 5 °C/min to 20 °C/min, the Hg releasing peaks ranged from 150 to 400 °C shifted gradually to higher temperature zones, but there was no obvious change in the positions of peaks ranged from 400 to 800 °C. Graphical abstract Unlabelled Image Highlights • The Hg distribution and releasing behavior in samples were investigated by using multistep solvent extraction method. • The Hg contents in EG 1 to EG 4 samples have little correlation with the total sulfur contents. • The Hg species and their thermal stability in different samples are quite distinct. • More than 95% of Hg in raw coal can be released before 600 °C. • The Hg-OM+ combined with aromatic clusters in EG 2 has higher releasing temperature than other Hg species. [ABSTRACT FROM AUTHOR]

In this study, a green synthesis route was developed to prepare Ca and Co oxides supported carbon aerogel from renewable alginate. The sodium alginate was adopted as a template and carbon source, and a hydrogel with a three-dimensional and core-shell structure was chelated by introducing calcium and cobalt bimetals. The synthesized Ca Co oxides supported carbon aerogel can completely remove Hg0 in the HCl-containing waste gasification gas at room temperature. The Hg0 adsorption capacity on the 4Ca-1Co/CA adsorbent is as high as 4.02 mg/g when the 5% breakthrough occurs. At a 20% breakthrough of HCl, the captured amount of HCl could reach 175.37 mg/g. We concluded that the introduction of calcium and cobalt on the adsorbent provides sufficient active sites for the removal of HCl in a large amount, at the same time, the excellent oxygen supply capacity of Co species in an oxygen-free atmosphere can form active chlorine sites, which is conductive to enhance the removal of Hg0. Additionally, the 4Ca-1Co/CA adsorbent has the characteristics of wide temperature window and wide application range of space velocity, which can meet the needs of various working conditions. [Display omitted] • A green synthesis route to prepare Ca and Co oxides supported carbon aerogel from renewable alginate is provided. • There is a synergistic effect on removing HCl and Hg0 at 4Ca-1Co/CA adsorbent. • The introduction of Ca and Co provides sufficient active sites for the highly efficient removal of HCl and Hg0. • A wide temperature window and high space velocity could be performed on 4Ca-1Co/CA adsorbent. [ABSTRACT FROM AUTHOR]