Phosphate Removal in Relation to Structural Development of Humic Acid-Iron Coprecipitates

Abstract

Precipitation of Fe-hydroxide (FH) critically influences the sequestration of PO4 and organic matter (OM). While coatings of pre-sorbed OM block FH surfaces and decrease the PO4 adsorption capacity, little is known about how OM/Fe coprecipitation influences the PO4 adsorption. We aimed to determine the PO4 adsorption behaviors on humic acid (HA)-Fe coprecipitates in relation to surface and structural characteristics as affected by HA types and C/(C + Fe) ratios using the Fe and P X-ray absorption spectroscopy. With increasing C/(C + Fe) ratios, the indiscernible changes in the proportion of near-surface C for coprecipitates containing HA enriched in polar functional groups implied a relatively homogeneous distribution between C and Fe domains. Wherein PO4 adsorbed on FH dominated the P inventory on coprecipitates, yielding PO4 sorption properties nearly equivalent to that of pure FH. Structural disruptions of FH caused by highly associations with polar functional groups of HA enhanced the C solubilisation. While polar functional groups were limited, coprecipitates consisted of core FH with surface outgrowth of HA. Although surface-attached HA that was vulnerable to solubilisation provided alternatively sites for PO4 via ternary complex formation with Fe bridges, it also blocked FH surfaces, leading to a decrease in PO4 adsorption.

Iron, Phosphorus and Trace Elements in Mussels’ Shells, Water, and Bottom Sediments from the Severnaya Dvina and the Onega River Basins (Northwestern Russia)

“…In contrast, a strong positive correlation between Fe and P in shells of mollusks may indicate either P co-precipitation with Fe hydroxide or formation of Fe phosphate at the shell surface or impregnated between growing layers. Strong removal of P with Fe hydroxide from aqueous solutions is fairly well known [24][25][26]. The importance of this process for concomitant Fe and P accumulation in mollusks shells is consistent with the fact that the K d Shell/Water for Fe and P did not exhibit statistically significant regression relationships with the distance from the mouth of the Severnaya Dvina River (p > 0.05), despite sizable variations of these element concentrations in the river water.…”

The Role of Surface Functional Groups of Iron Oxide, Organic Matter, and Clay Mineral Complexes in Sediments on the Adsorption of Copper Ions

“…In addition to more surface functional groups, group B had the characteristics of strong silicide activity. Moreover, the organic matter removal (organic degradation in sediment) would reduce the polar functional groups and reduce the activity of silicide, and lead to heavy metal desorption and re-entry into the water body [44]. Therefore, it was observed that the adsorption capacity of the organic matter-clay mineral complex in group B was higher than that of group A inorganic minerals.…”

Efficiency and mechanism of phosphorus removal by iron-organic matter associations in peatland

“…Both of them have remarkable anti-biodegradation properties, which allows for their long-term stability in soil (Chen et several studies proposed that HS does not signi cantly affect the adsorption behavior of iron oxide (Borggaard et al 2006;Weng et al 2009). Khouri et al (1995) suggested that the inhibition of phosphate adsorption by OM was temporary, while Chen et al (2018) found that coprecipitates of ferrihydrite and OM yield P sorption properties nearly equivalent to that of pure ferrihydrite.…”