Appraising the effect of in-situ remediation of heavy metal contaminated sediment by biochar and activated carbon on Cu immobilization and microbial community

The immobilization of heavy metal Cu with rice husk biochar (RHB) and activated carbon (AC) addition were compared by in-situ remediation of sediment in this research. The RHB and AC were characterized using SEM, FTIR, XRD, XPS, Raman and BET surface area measurements. Heavy-metal contaminated sediments were immobilized by RHB and AC with the addition amount of 2%, 5% and 10% (w/w). The sequential extraction experiment demonstrated that the acid-soluble fractions of Cu were reduced by 48%-93% and 18%-31% with the treatment of AC and RHB, respectively. With the decrease of acid-soluble fractions of Cu, the results showed that the surface water concentration of Cu decreased by 32%-68% and 8%-60% with the treatment by AC and RHB, respectively. The Cu concentration of interstitial water decreased by 14.8%-63% and 11.1%-48.1% with the treatment by AC and RHB, respectively. Meanwhile, hierarchical cluster analysis which was used for the detection of microbial community was conducted. The results showed that the microbial community was destroyed in the sediment treatment with high amount of AC. However, new microbial community appeared in the sediment treatment with three addition amount of RHB. Based on the data analysis, AC was more effective than RHB on Cu immobilization in the sediment. Unfortunately, AC was more expensive than RHB and had potential negative effect on microbial community. By comparing these aspects comprehensively, our results suggest that the RHB would be a low-cost and environmentally friendly material for heavy-metal contaminated site remediation.