Insights into the Enhanced Stabilization of Heavy Metals in Sediments: A Novel Biochar-Fe-Heavy Metal Ternary System

Abstract

The stable management of heavy metals in sediments was a crucial approach for the restoration of aquatic ecosystems. To investigate the impact of biochar on heavy metal stability in sediments, the alterations in stability of Cu, Pb and Zn were examined via scanning electron microscopy-energy dispersive spectrometer (SEM-EDS), X-ray photoelectron spectroscopy (XPS), and electron probe microanalysis (EPMA). The results of the toxicity characteristic leaching procedure (TCLP) tests revealed a progressive decrease in the CTCLP values of Cu, Pb and Zn in sediments as the quantity of biochar added increased. The inclusion of 2.5~10% biochar resulted in a significant increase, ranging from 2.6% to 78.3%, in the ratio between the oxidation state (F3) and residual state (F4), while concurrently leading to a reduction, varying from 3.3% to 15.4%, in the zinc content present in the weakly acidic extractable state (F1). Furthermore, the correlation between the stability of Fe and Cu, Pb, and Zn has been found. In general, the addition of biochar enhanced the activity and stability of Fe, while the incorporation of biochar-Fe-heavy metal ternary system had been proposed as a fundamental mechanism to elucidate the stabilization of heavy metals in sediment modified by biochar.

Keywords: Biochar, Heavy metals, sediments, stabilization, Mechanism