Changes in the extractability and fractionation of cadmium and copper in a contaminated soil amended with various sugarcane bagasse-based materials.

Heavy-metal contamination in soil has long been a persistent challenge and the utilization of agricultural waste for in-situ stabilization remediation presents a promising approach to tackle this problem. Agricultural wastes exhibit promising potential in the remediation of contaminated land and modification could improve the adsorption performance markedly. Citric acid and Fe ₃ O ₄ treated sugarcane bagasse adsorbed more heavy metals than raw materials in the aqueous system, employing these materials for heavy metal remediation in soil holds significant implications for broadening the raw material source of passivators and enhancing waste utilization efficiency. In this paper, a 120-day soil incubation study was conducted to compare the effects of pristine sugarcane bagasse (SB), citric-acid modified (SSB1, SSB2 and SSB3 with increasing proportion of citric acid) and citric-acid/Fe ₃ O ₄ modified (MSB1, MSB4 and MSB7 with increasing proportion of Fe ₃ O ₄ ) sugarcane bagasse at 1 % addition rate on cadmium (Cd) and copper (Cu) passivation. The SB, SSB1 and MSB1 did not always decrease the content of CaCl ₂ -extractable Cd while all the seven amendments decreased the CaCl ₂ -extractable Cu during the experiment period. Among all materials, SSB3 and MSB7 exhibited the highest efficiency in reducing the concentrations of CaCl ₂ -extractable Cd and Cu. At Day 120, SB, SSB3 and MSB7 reduced the content of CaCl ₂ -extractable Cd by 8 %, 18 % and 24 %, and of CaCl ₂ -extractable Cu by 25 %, 50 % and 61 %, respectively. The efficiency of Cd and Cu immobilization was associated positively with the pH, functional groups and H-bonds of the amendments. The results suggest that the efficiency of sugarcane bagasse in heavy-metal passivation can be largely enhanced through chemical modifications using high proportions of citric acid and Fe ₃ O ₄ .
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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