A potential method using magnetically modified wheat straw biochars for soil Cd extraction

Every year, hundreds of millions of tons of straw are produced by wheat planting all over the world. In this work, a potential method using wheat straw to produce magnetic sorbents for soil Cd extraction was studied. Wheat straw chips were pyrolyzed at 300 and 700 ?C and then mixed with Fe3+/Fe2+ solution for magnetization. The obtained magnetically modified biochars (MMBs) were applied to two Cd-contaminated paddy soils. During a 30day experiment, MMB recovery from soils by a magnetic rod decreased over time, ranging from 62% to 100% for MMB300 and from 36% to 65% for MMB700. At the end, extraction efficiency of Cd from soils by the MMBs ranged from 21.5% to 31.5%, which was related to sorption capacity of Cd by MMB, recovery percentage of MMB from soils and distribution of Cd fractions in soils. Cd in the exchangeable fraction was more easily extracted by the MMBs (46?78%) than the other Cd fractions. Furthermore, extracting Cd from soils by the MMBs reduced Cd concentration in ryegrass by about 70%, which was largely related to the decrease of soil exchangeable fraction. These findings demonstrate the efficient remediation of Cd-contaminated soils by MMB extraction and meanwhile provide some guidance for further optimization of MMB properties.

Automated summary

This study investigated the potential method of using wheat straw to produce magnetic sorbents for soil Cd extraction. The experiment found that extraction efficiency of Cd from soils by the magnetically modified biochars (MMBs) can significantly reduce Cd concentration in soil, providing guidance for the efficient remediation of Cd-contaminated soils.