Integrating cadmium removal and phosphate supplementation by fortified biochar hydrogel for agricultural soil: a novel composite material

The preparation of phosphate-loaded biochar-based hydrogel composite beads impregnated with phosphate solubilising bacteria (PSB) for simultaneous immobilisation of cadmium and release of plant-available phosphorus has been reported in the present experiment. The prepared tri-calcium phosphate-loaded biochar hydrogel-PSB beads (THB) showed outstanding swelling properties with better stability. Cadmium (Cd) adsorption onto the THB was found to be 98% within 5 min in aqueous solution. Cadmium accumulation by rice (Oryza sativa L.; cv IET 4094) plant was 4.71 times greater than that of plants grown in THB-treated soil. Insoluble tri-calcium phosphate (TCP) was used as the phosphate source in the THB. Phosphate solubilising bacteria present within the THB matrix solubilises the TCP for the efficient generation of plant-available phosphate, demonstrated by the release of 0.26 mol phosphate after 11 days. The plant growth study with THB-treated soil also confirms a significant increase in total seedling length compared to the hydrogel, biochar hydrogel beads, and control treatment. This THB composite holds promising potential to act as a bifunctional tool for the improvement of the phosphate crisis in agriculture and land reclamation simultaneously.