Effect of different pretreatments on the thermal degradation of seaweed biomass

Abstract

This study aims to investigate the pyrolysis characteristics of seaweed biomass (Enteromorpha) after water-washed and acid-washed (7%, 10% of hydrochloric acid, 7% of sulfuric acid, 7% of phosphoric acid) pretreatments. These pretreatments of seaweed were signifi after water-washed and acid-washed (7%, 10, Ca, Na and Mg metals. Among these pretreatments the removal capacity of H2SO4 was the most obvious. The pyrolysis behaviors of materials after pretreatments have been studied using thermogravimetry-mass spectroscopy. During the pretreatments, OH, CO/CH, SO and CO functional groups in Enteromorpha were cleaved. Phosphoric acid and hydrochloric acid made the intensities of the absorption peaks of OH and SO decrease the most obvious, respectively. Therefore, there was almost no NO2 and SO2 emission in the process of pyrolysis of Enteromorpha washed by hydrochloric acid and phosphoric acid. The volatile components of Enteromorpha were easy to evolve after the pretreatment. Sulfuric acid exhibited the best efficiency in the process of pyrolysis, and it manifested smaller influence on other volatile organics simultaneously. However, the maximum weight loss rate and the corresponding temperature reduced after pretreatments, and the maximum weight loss rate reduced more distinctly after 7% hydrochloric acid treatment. These results suggest that selective acid pretreatment would facilitate the thermal conversion of seaweed biomass.