Zinc Interaction with Struvite During and After Mineral Formation

Rouff, Ashaki A.; Juarez, Karen M.

doi:10.1021/es500188t

Cited by 58 publications

(33 citation statements)

References 48 publications

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“…As is also relevant to repurposing MAP recovered from wastewaters for additional usage, such as fertilizer. For example, contaminants such as Cr and Zn can associate with MAP during mineralization (Rouff, 2012;Rouff and Juarez, 2014), and MAP generated from such systems can also incorporate As into the structure during the precipitation process (Ma and Rouff, 2012).…”

Section: Discussionmentioning

confidence: 99%

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Adsorption of arsenic with struvite and hydroxylapatite in phosphate-bearing solutions

Rouff

Kustka

2016

Chemosphere

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Arsenic sorption at above neutral pH is relevant when considering contaminant mobility in alkaline, phosphorus-bearing wastewaters, and may be viable in the presence phosphate minerals. Arsenic adsorption on struvite (MgNH 4 PO 4 •6H 2 O, MAP) and hydroxylapatite (Ca 5 (PO 4) 3 OH, HAP) was evaluated at pH 8-11 from solutions with 2.7-0.125 mM phosphate and 0.05 mM As(III) or As(V). Over 7 d, As(III) removal from solution was minimal, but As(V) removal increased with pH, and was higher in the presence of MAP compared to HAP with a maximum of 74% removal in pH 11 MAP-bearing solutions. X-ray absorption fine structure spectroscopy (XAFS) analysis of solids recovered from pH 10-11 solutions revealed different mechanisms of As(V) sorption with MAP and HAP. Arsenic forms monodentate mononuclear surface complexes with MAP through the formation of a Mg-O-As bond, but is incorporated at the near-surface of HAP forming a johnbaumite-like (Ca 5 (AsO 4) 3 OH) structure. Experiments using radioactive 33 P at pH 10-11 revealed faster exchange of P at the HAP surface, which could promote more facile As incorporation. Near-surface incorporated As in HAP may be less susceptible to remobilization compared to surface adsorbates formed with MAP. Overall, both MAP and HAP may sorb As at high pH in the presence of phosphate. This is relevant to the fate of As in alkaline contaminated waters in contact with phosphate mineral phases.

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Section: Discussionmentioning

confidence: 99%

“…As removal by adsorption may be enhanced. Therefore the potential for MAP to adsorb As, and other contaminants (Rouff and Juarez, 2014), has implications for repurposing of this mineral.…”

Section: Discussionmentioning

confidence: 99%

Adsorption of arsenic with struvite and hydroxylapatite in phosphate-bearing solutions

Rouff

Kustka

2016

Chemosphere

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“…Common contaminants present in wastes include heavy metals and metalloids, such as chromium (Cr), zinc (Zn), copper (Cu), nickel (Ni), cobalt (Co), arsenic (As), and selenium (Se), as well as various organic substances and pathogens. During struvite precipitation, these species could either be incorporated in the struvite structure, adsorbed to the crystal surface, or precipitated as separate phases [9][10][11][12][13]. Thus, such ions likely affect the crystallisation behaviour of struvite.…”

Section: Introductionmentioning

confidence: 99%

Struvite Crystallisation and the Effect of Co2+ Ions

et al. 2019

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The controlled crystallisation of struvite (MgNH4PO4∙6H2O) is a viable means for the recovery and recycling of phosphorus (P) from municipal and industrial wastewaters. However, an efficient implementation of this recovery method in water treatment systems requires a fundamental understanding of struvite crystallisation mechanisms, including the behavior and effect of metal contaminants during struvite precipitation. Here, we studied the crystallisation pathways of struvite from aqueous solutions using a combination of ex situ and in situ time-resolved synthesis and characterization techniques, including synchrotron-based small- and wide-angle X-ray scattering (SAXS/WAXS) and cryogenic transmission electron microscopy (cryo-TEM). Struvite syntheses were performed both in the pure Mg-NH4-PO4 system as well as in the presence of cobalt (Co), which, among other metals, is typically present in waste streams targeted for P-recovery. Our results show that in the pure system and at Co concentrations < 0.5 mM, struvite crystals nucleate and grow directly from solution, much in accordance with the classical notion of crystal formation. In contrast, at Co concentrations ≥ 1 mM, crystallisation was preceded by the transient formation of an amorphous nanoparticulate phosphate phase. Depending on the aqueous Co/P ratio, this amorphous precursor was found to transform into either (i) Co-bearing struvite (at Co/P < 0.3) or (ii) cobalt phosphate octahydrate (at Co/P > 0.3). These amorphous-to-crystalline transformations were accompanied by a marked colour change from blue to pink, indicating a change in Co2+ coordination in the formed solid from tetrahedral to octahedral. Our findings have implications for the recovery of nutrients and metals during struvite crystallisation and contribute to the ongoing general discussion about the mechanisms of crystal formation.

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“…where k a and k d represent the adsorption and desorption rate constants, PO 4 3− represents the various possible solution-phase phosphate species (which are assumed to interchange rapidly), ≡FeOH represents the active surface site on PF-HFO, which was determined to be 0.45 mM ([Fe], mM) −1 in our previous study 7 (though protonated or deprotonated forms may dominate depending upon the pH), and ≡FeH n PO 4 (3−n)− was considered to be representative of the phosphate “surface complex”, which forms on the surface of HFO (and which is simplified to ≡FeP below). It should be noted that the phosphate surface complex used in this study was semi-empirical and that the actual surface speciation of HFO was complicated and should be further investigated by ATR-FTIR and XAFS 37 .…”

Section: Methodsmentioning

confidence: 99%

Kinetic Modeling of Phosphate Adsorption by Preformed and In situ formed Hydrous Ferric Oxides at Circumneutral pH

Mao

Yue

2016

Sci Rep

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Kinetics of phosphate removal by Fe(III) was investigated by both preformed and in situ formed hydrous ferric oxides (HFO) at pH 6.0–8.0. A pseudo-second-order empirical model was found to adequately describe phosphate removal in the two cases. The Elovich and intra-particle diffusion models, however, were only capable of describing phosphate adsorption to preformed HFO (PF-HFO). By using surface complexation kinetic models (SCKMs) to describe phosphate adsorption to PF-HFO, the adsorption rate constant (0.0386–0.205 mM−1 min−1 for SCKM-1 and 0.0680–0.274 mM−1 min−1 for SCKM-2) decreased with increasing pH while the protonation reaction rate constant in SCKM-2 (0.0776–0.0947 mM−1 min−1) increased over the pH range 6.0–8.0. Using the rate constants obtained from the process of phosphate adsorption to PF-HFO, the amount of active surface sites on the in situ formed HFO were calculated as 0.955 ± 0.170, 1.46 ± 0.39 and 2.98 ± 0.78 mM for pH = 6.0, 7.0 and 8, respectively. Generally, as the SCKMs incorporate phosphate complexation on HFO surface sites and protons competiting for the surface sites, they could provide a good description of the rate and extent of phosphate removal by both preformed and in-situ formed HFO over a wide range of conditions.

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Zinc Interaction with Struvite During and After Mineral Formation

Cited by 58 publications

References 48 publications

Adsorption of arsenic with struvite and hydroxylapatite in phosphate-bearing solutions

Adsorption of arsenic with struvite and hydroxylapatite in phosphate-bearing solutions

Struvite Crystallisation and the Effect of Co2+ Ions

Kinetic Modeling of Phosphate Adsorption by Preformed and In situ formed Hydrous Ferric Oxides at Circumneutral pH

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