Control of heavy metals in sludge pyrolysis process by modified sepiolite
A variety of heavy metals were inevitably produced in the process of sludge pyrolysis.In this study,Co-pyrolysis experiments of municipal sludge with modified sepiolite in several factors including hydrochloric acid impregnation concentration of sepiolite(2-6mol/L),thermal activation temperature of sepiolite(750-950℃),and co-pyrolysis temperature of sludge and sepiolite(400-600℃)were conducted in a horizontal fixed-bed reactor.The effects of these factors on the enrichment characteristics,morphological changes and ecological risks of heavy metal elements Cd,Zn,Pb and Cr in sludge pyrolysis carbon were investigated.The results showed that the addition of modified sepiolite effectively increased the retention rates of Cd,Zn and Pb in the co-pyrolysis temperature range of 400-600℃,but had little effect on Cr enrichment.The modified sepiolite,especially the 950-SEP and 4H-SEP,exhibited a good enrichment effect on Cd,Zn and Pb.In addition,the analysis of the heavy metal fugacity pattern showed that the increase of pyrolysis temperature and modified sepiolite both led conversion of heavy metal in biochar to a more stable form.According to the ecological risk assessment of heavy metals in the pyrolysis biochar,the ecological risk of raw sludge was greatly reduced after pyrolysis.The addition of modified sepiolite effectively reduced the ecological risk of heavy metals in the sludge pyrolysis char below 600℃.
万方数据
维普
