•Novelty biomimetic mineralized microalgae cultivated in Hg(II) wastewater.•Mineralized layer enhanced activity of cells in Hg(II) wastewater.•Higher lipid yield was observed in mineralized modified cells.•Removal of Hg(II) by modified microalgae was proved to be 94.74%.Considering the high concentration of mercury in industrial wastewater, such as coal-fired power plants and gold mining wastewater, this research study investigated the coupling process of lipid production and mercury bioremediation using microalgae cells. Chlorella vulgaris modified by biomimetic mineralization. The cultivation was divided in two stages: a natural cultivation for 7 days and 5 days of Hg2+ addition (10–100 μg/L) for cultivation at different pH values (4–7) after inoculation. Next, the harvested cells were eluted, and lipid was extracted. The fluorescein diacetate (FDA) dye tests demonstrated that the mineralized layer enhanced the biological activity of microalgae cells in Hg2+ contaminated media. Hg distribution tests showed that the Hg removal capacity of modified cells was increased from 62.85% to 94.74%, and 88.72% of eluted Hg2+ concentration was observed in modified cells compared to 48.42% of raw cells, implying that more mercury was transferred from lipid and residuals into elutable forms.Download high-res image (132KB)Download full-size image

•H2 yield was promoted by adding K2CO3 or CH3COOK but inhibited by adding KCl.•K2CO3 showed different catalytic activity from CH3COOK from 600 °C to 700 °C.•Carbon conversion in SEG process was enhanced by adding K2CO3 or CH3COOK.•The results can be used to select a proper catalyst in SEG process.Sorption enhanced gasification (SEG) of biomass with steam was investigated in a fixed-bed reactor to elucidate the effects of temperature, catalyst type and loading on hydrogen production. K2CO3, CH3COOK and KCl were chosen as potassium catalyst precursors to improve carbon conversion efficiency in gasification process. It was indicated that from 600 °C to 700 °C, the addition of K2CO3 or CH3COOK catalyzed the gasification for hydrogen production, and hydrogen yield and carbon conversion increased with increasing catalyst loadings of K2CO3 or CH3COOK. However, the hydrogen yield and carbon conversion decreased as the amount of KCl was increased due to inhibition of KCl on gasification. The maximum carbon conversion efficiency (88.0%) was obtained at 700 °C corresponding to hydrogen yield of 73.0 vol.% when K2CO3 of 20 wt.% K loading was used. In particular, discrepant catalytic performance was observed between K2CO3 and CH3COOK at different temperatures and the corresponding mechanism was also discussed.

The influence of KCl and CaCl2 on the primary reactions of cellulose pyrolysis is studied using a wire-mesh reactor from 250 °C to 600 °C, focusing on the reaction intermediates. A pre- column derivatization with benzoyl chloride prior to HPLC analysis is applied for the quantification of anhydro-sugars (levoglucosan, cellobiosan, maltosan) from pyrolysis. At low temperatures, the additions of inorganics salts, especially CaCl2, weakens hydrogen bonds, resulting in high yields of levoglucosan and cellobiosan from the cleavage of glycosidic bonds rather than from dehydration reactions. At elevated temperatures, dehydration reactions in the sugar units are mainly responsible for the destruction of sugar rings followed by the scission of pyran rings, leading to the weight-loss of CaCl2-loaded cellulose in the form of low molecular weight organic species. Meanwhile, accumulated unsaturated structures suppress the cleavage of glycosidic bonds, leading to the formation of char. However, KCl appears to catalyze the cleavage of glycosidic bonds or the scission of pyran rings directly, which perhaps occurs through a homolytic mechanism, leading to low molecular weight species. Furthermore, maltosan is shown to be a secondary product and is catalyzed by KCl and CaCl2 indirectly through the repolymerization of levoglucosan in the solid phase. A modified mechanism is also proposed regarding cellulose pyrolysis and the primary catalysis of KCl and CaCl2.