Ball-milled sepiolite/phosphate rock for simultaneous remediation of cadmium-contaminated farmland and alleviation of phosphorus deficiency symptoms in pepper

Abstract

Herein, ball-milled combination of sepiolite and phosphate rock was carried out for synergistic passivation of Cd in soil and alleviation of phosphorus deficiency in pepper. The as-prepared BM-Sep2PR1 exhibited extensive pH adaptability and fast uptake for Cd(II) with maximal uptake capacity of 78.67 mg/g. After application of 0.5 % BM-Sep2PR1, the bioavailability of Cd in soil decreased by 58.2 %, and its unstable forms declined by 57.0 % with transformation into residual speciation such as Cd3(PO4)2 and CdnCa5-n(PO4)3OH. Moreover, BM-Sep2PR1 significantly decreased the amount of Cd in pepper shoot (77.8 %) and root (54.8 %), and the bioconcentration factors (soil-root) and translocation factors (root-shoot) were significantly reduced by 54.8 % and 50.8 %, respectively. Notably, the soil available phosphorus, pepper root vitality, and photosynthetic pigment content increased by 202.8 %, 136.4 %, and 58.4 %, respectively, thus significantly alleviating the phosphorus deficiency symptoms of pepper. Additionally, BM-Sep2PR1 improved soil microbial community structure, especially enhanced the abundance of microorganism involved in nutrient cycling and heavy metal resistance. The Cd passivation mechanisms of BM-Sep2PR1 were identified as pore filling, electrostatic attraction, ion exchange, surface complexation, and chemical precipitation. Overall, this study provided a potential strategy for synergetic soil remediation and plant nutrient supplement by using ball-milled functional materials.