Hydrothermal synthesis of LDO/vinasse biochar composites with ultra-high specific surface areas for phosphate remediation and fertilizer utilization

In this work, CaMgAl-layered double oxide/biochar (LDO@BC) composites were elaborated by hydrothermal coprecipitation and calcination for the efficient recovery of phosphate as well as the further application of the reclaimed composites as fertilizers. On the one hand, the appropriate selection of biochar derived from vinasses as the substrates could solve the limitations of LDO like low specific surface areas as well as poor dispersion. The obtained composites possess the ultrahigh specific surface area as high as 508.97 m2/g. Therefore, a maximum adsorption capacity of 153.64 mg/g is achieved. In addition, our composites are with fast adsorption rates that nearly 100 % phosphate could be removed within 60 s at a trace concentration owing to the large specific surface areas. On the other hand, the recovered adsorbents could be used as fertilizers because of the high contents of P, Ca and Mg elements. The phosphate-adsorbed LDO@BC (P-LDO@BC) demonstrated a positive fertilization effect, significantly accelerating plant growth with length increment by 0.75 times and mass increment by 2.09 times compared with the control groups. Thus, this work not only provides a new approach for waste vinasse utilization, but also presents a promising adsorbing material for phosphate recovery and reuse.