Contrasting Cr(VI) and Cd(II) immobilization in contaminated soils by microalgae derived hydrochar.
Wang Y, Cao B, Chen L, Qiu X, Hu C
Phytoremediation
Vegetable gardens and allotments on former industrial land often carry invisible chromium or cadmium contamination that quietly moves into roots and leaves — this algae-based soil amendment could block that transfer at the source.
Scientists took a material called hydrochar, made by cooking algae under pressure and heat, and mixed it into soils polluted with two dangerous heavy metals: chromium and cadmium. The hydrochar acted like a trap, keeping the metals stuck in the soil rather than being absorbed by plants — it was especially effective at locking down chromium (nearly 97% immobilized). As a bonus, the soil's beneficial microbes started recovering after the treatment.
Key Findings
Algal hydrochar immobilized 96.9% of Cr(VI) and 76.1% of Cd(II) in contaminated soils, with metals remaining stable through wet-dry and freeze-thaw aging cycles.
Sequential extraction showed both metals shifted from easily dissolved (labile) fractions to more stable soil-bound fractions, significantly reducing plant uptake and translocation.
The two metals were trapped by different mechanisms: chromium was chemically reduced to a less toxic form (Cr III) via electron transfer, while cadmium was held by electrostatic attraction and bonding to oxygen- and nitrogen-containing groups on the hydrochar surface.
chevron_right Technical Summary
Researchers found that hydrochar made from algae (Chlorella) can lock heavy metals — chromium and cadmium — into contaminated soils, reducing their uptake by plants. The material works through different chemical mechanisms for each metal, and it also helps restore the soil's microbial community.
Abstract Preview
Heavy metal accumulation in soils poses serious environmental risks, particularly from Cr(VI) and Cd(II). Hydrochar is a promising amendment for in situ immobilization of heavy metals; however, the...
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