Controlled release of molasses melanoidin-like product from hybrid organic–inorganic silica xerogels and its application to the phytoextraction of lead through the Indian mustard

In this study, we investigate the release of melanoidin-like product (MLP) from hybrid silica xerogels to control the quantity of MLP in the medium for lead phytoextraction. In the preparation of the hybrid organic–inorganic xerogels with MLP, tetraethoxysilane (TEOS), methyltriethoxysilane (MTES), propyltriethoxysilane (PTES), and 3-aminopropyltriethoxysilane (APTES) were used as precursors. The experimental results suggest that the release of MLP can be easily controlled by partially substituting TEOS with the organosilanes. The addition of the organosilanes lowered the release rate of MLP in the following order of xerogels: TEOS, MTES/TEOS, PTES/TEOS, and APTES/TEOS. Furthermore, a novel phytoextraction of lead through the Indian mustard was conducted using the MLP-doped TEOS xerogel. Results show that the addition of TEOS xerogel did not have any influence on the growth of the mustard, whereas the lead uptake significantly increased in a nutrition medium with 1-mM Pb(NO). In conclusion, the beneficial effect of the MLP-doped TEOS xerogel on lead phytoextraction was confirmed.