Description:
The influence of nanoparticles (NP) on the accumulation of heavy metals in the paddy crust (PC) was unclear. This experiment explored the potential effects and mechanism of TiO2 NP with different particle sizes on Cd removal by PC from waterbody. All the TiO2 with size of 25 nm (T25), 100 nm (T100) and 2000 nm (T2000) can promote the Cd uptake by the PC, and with the sequence: T100>T25>T1000. Especially, 0.1mg/L T100 can enhanced ~45% Cd removal comparing with pristine PC, and the Cd uptake capacity reached as high as 92 mg/g. After treatment of 72h, the PC+T100 can reduce Cd in the acidic coal drainage from 0.48 mg/L to 0.009 mg/L, with removal efficiency of 98%. The TiO2 stimulation to PCs secreted the extracellular substance and then increased the content of amino/hydroxyl adsorptive sites by 30-70%. T25 can only stimulate the Microcystics, Chlorococcum, Scenedesmius and bacteria with thin cell membranes to produce extracellular substance. However, T100 can stimulate not only the sheath layer of Oedogonium, the main component of PC, but also the previous mentioned algae and bacteria. And induce it to produce a large amount of protein, phospholipids, etc. T25 would easily enter the cell trough thin cell membranes, result in that the Cd attached to T25 to penetrate the intracell. Our investigation demonstrated that the addition of nanoparticles TiO2 with appropriated size was a potential efficient method to remove the heavy metal from waterbody by enhancing Cd uptake in PCs