0000000000298168
AUTHOR
Gerald T. Schmidt
Adsorption mechanism of arsenate by zirconyl-functionalized activated carbon
Arsenate [As(V)] and arsenite [As(III)] sorption at the solid-water interface of activated carbon impregnated with zirconyl nitrate (Zr-AC) was investigated using X-ray absorption spectroscopy (XAS) and surface complexation modeling. The XAS data at the Zr K-edge suggest that the structure of the zirconyl nitrate coating is built from chains of edge-sharing ZrO8 trigonal dodecahedra bound to each other through two double hydroxyl bridges. The 8-fold coordination of each Zr atom is completed by four O atoms, which share a bit less than the two theoretically possible bidentate nitrate groups. On impregnation, two of the O atoms may lose their nitrate group and be transformed to hydroxyl group…
Speciation of Copper in Enriched Agricultural Lime
Agricultural liming materials are used to lower soil acidity and to improve microbial functionality and plant growth. A brownish colored agricultural lime was found to contain up to 180 mg kg ―1 Cu, an amount well above any fertilizing materials code threshold. The dark color of the milled material was due to ample black and brown dendrites consisting of the tectomanganate mineral romanechite (ideally (Ba,H 2 O) 2 (Mn 4+ ,Mn 3+ ) 5 O 10 ) and a mixture of the two nanocrystalline Fe oxides ferrihydrite and goethite. A four-step sequential extraction analysis of the lime powder was not sufficient to argue whether the Cu load was contained in the carbonate matrix or in the oxide dendrites, or,…
Speciation and Mobility of Arsenic in Agricultural Lime
Agricultural liming materials are used to correct soil acidity and to improve plant growth and microbial functionality. A relatively low-grade agricultural lime was found to contain up to 125 mg kg(-1) arsenic (As), which is above any fertilizing materials code threshold. The color of the milled material is brown due to ample oxide dendrites. Microprobe elemental maps confirmed that these accessory oxide mineral phases are responsible for the elevated As concentrations in the limestone. The black Mn-bearing dendrites contain minor amounts of As, whereas the brown Fe-bearing dendrites contain the major part of the As inventory, with an Fe/As molar ratio around 100. Because the elemental maps…