Functionalized organo-mineral composites of biochar for the effectual immobilization of arsenic in contaminated soil

Arsenic (As) pollution has become one of the major environmental challenges around the world as it is a carcinogenic and toxic metal. Efficient removal of As from soil on sustainable basis is of critical importance.

Organo-mineral composites of date palm-derived biochar (BC) produced at 400°C (B4) and 600°C (B6) were synthesized by intercalation of 10% (B4-C10 and B6-C10) and 20% (B4-C20 and B6-C20) of nano-sized bentonite. After the characterization, the synthesized amendments applied to As-contaminated soils (0 mg kg⁻¹ (OS), 100 mg kg⁻¹ (S1) and 200 mg kg⁻¹ (S2) of As concentrations) at 0% (CK), 1%, and 3% (w/w) application rate under greenhouse conditions with maize (Zea mays L.) as test crop.

The application of 3% B6-C20 resulted in 21% reduced availability of As than CK, indicating the highest As immobilization. The similar treatment resulted in 71%, 64%, and 52% higher shoot length in S2, S1, and OS, respectively, while 66%, 67%, and 56% higher root length in S2, S1, and OS, respectively, than CK. B6-C20 with 3% application rate resulted in 38% and 34% reduced root As concentration in S1 and S2, respectively, while 58% and 59% reduced As in shoots in S1 and S2, respectively, than CK. The similar treatment resulted in the highest phosphorus (3455 mg kg⁻¹) and potassium (755 mg kg⁻¹) in shoots. Phytoextraction indices showed that B6 composites with nano-bentonite can be used for the phytostabilization of As using maize plants.

The outcomes of this study indicated that the amendments could potentially be used for the immobilization of As and improving maize plant growth.