Abstract
Fe and Mn (hydr)oxides are widely used as contaminant sorbents in water/wastewater systems but their potential use as micronutrient fertilizers is still poorly known. In this research, four nano-metal (hydr)oxides (amorphous Mn oxide (AMO), Fe-Mn binary oxide (FMBO), two-line ferrihydrite (2L-Fh) and goethite) were successfully synthesized and completely characterized (infrared and Mössbauer spectroscopy, X-ray diffraction particle size, specific surface area, point of zero charge). AMO, FMBO and 2L-Fh were introduced to interact with AgNO3 (20.0 µM) and TlNO3 (100.0 µM) diluted solutions for three days to check their potential capability as potential Ag+ and Tl+ adsorbents. AMO and FMBO (4% w/w) were tested as nanofertilizers by arranging a hydroponic bioassay for 35 days on white lupin culture as a Mn-hyperaccumulator plant model. AMO structure was identified as an amorphous mixture of Mn oxides while FMBO was an Fe dopped birnessite. Both materials were efficient in extracting Ag+ and Tl+ although large Mn concentration was released from FMBO to the solutions. AMO and FMBO promoted Fe and Mn nutrition in plants. Synthetic iron chelate (Fe-EDDHA), present in the nutrient dissolution, could be adsorbed onto AMO surface by producing Fe and Mn accumulation in roots and increasing Mn uptake rate without toxicity symptoms. Therefore, AMO and FMBO not only demonstrated their efficiency as adsorbents, but also displayed they would be promising nanomaterials as micronutrient fertilizers.
Highlights
Iron and manganese oxides are the most studied nanomaterials (NMOs) and are of particular interest because they have strong redox and sorption properties that can limit the mobility of toxic metals within soils, even under a range of redox conditions [1]
In this study, synthetics amorphous Mn oxides (AMOs) and ferro-manganese binary oxide (FMBO) were evaluated as heavy metal absorbents and ecofriendly micronutrient fertilizers
FMBO presented the highest specific surface area and so, showing a synergic effect between the Fe and Mn amorphous oxides, higher than that obtained for other authors [21], but this is attributed to differences in the synthesis method as reagents and aging time
Summary
Iron and manganese oxides are the most studied nanomaterials (NMOs) and are of particular interest because they have strong redox and sorption properties that can limit the mobility of toxic metals within soils, even under a range of redox conditions [1]. Ferrihydrite is much more reactive compared to other iron oxides, which is attributed to its high degree of structural disorder and high specific surface area [4] It is a effective sorbent for heavy metals as Cu, Cr and Pb [5] and arsenate [6] and it is used in wastewater treatment [7]. Ferro-manganese binary oxide (FMBO) is a bimetallic oxide that contains iron and manganese It has been used for metal ions removal from aqueous medium [13], in particular, As (III), As(V), Co(II), SB(V) and Tl(III). It has superior performance mainly because they combine in just one material the oxidation performance of manganese oxide and the high adsorption of iron oxide [14]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
