skip to main content

Title: Transition metal-doped MgO nanoparticles for nutrient recycling: an alternate Mg source for struvite synthesis from wastewater
Nutrient nitrogen (N) and phosphorus (P) recovery from wastewater is an important challenge for enhanced environmental sustainability. Herein we report the synthesis and properties of mesoporous MgO nanoparticles doped with copper (Cu), iron (Fe), and zinc (Zn) as an alternative low-solubility high-abundance magnesium (Mg) source for crystalline struvite precipitation from nutrient-laden wastewater. Undoped MgO was shown to have the fastest phosphate (PO 4 3− ) adsorption kinetics with a k 2 value of 0.9 g g −1 min −1 at room temperature. The corresponding rate constant decreased for Cu–MgO (0.175 g g −1 min −1 ), Zn–MgO (0.145 g g −1 min −1 ), and Fe–MgO (0.02 g g −1 min −1 ). Undoped MgO resulted in the highest PO 4 3− removal at 94%, while Cu–MgO, Fe–MgO, and Zn–MgO resulted in 90%, 66% and 66%, respectively, under equivalent reaction conditions. All dopants resulted in the production of struvite as the main product with the incorporation of the transition metals into the struvite crystal lattice. X-ray absorption spectroscopy (XAS) showed that the majority of the Cu, Fe, and Zn were primarily in the +2, +3, and +2 oxidation states, respectively. XAS also showed that the Cu atoms exist in elongated more » octahedral coordination, while Fe was shown to be in octahedral coordination. Zn was shown to be in a complex disordered environment with octahedral sites coexisting with the majority of the tetrahedral sites. Finally, X-ray photoelectron spectroscopy data suggest a two-fold struvite surface enrichment with dopant metals, with Cu exhibiting an interesting new local binding structure. The dopant concentrations utilized were consistent with those found in natural Mg minerals, suggesting that (a) utilizing natural mineral periclase as the Mg source for struvite production can result in struvite formation, albeit at the expense of the reaction kinetics and overall yields, while also (b) supplying essential micronutrients, such as Zn and Cu, necessary for balanced nutrient uptake. « less
Authors:
; ; ; ;
Award ID(s):
1710120
Publication Date:
NSF-PAR ID:
10292516
Journal Name:
Environmental Science: Nano
Volume:
7
Issue:
11
Page Range or eLocation-ID:
3482 to 3496
ISSN:
2051-8153
Sponsoring Org:
National Science Foundation
More Like this
  1. Simultaneous major nutrient nitrogen (N) and phosphorus (P) recovery from wastewater is key to achieving food–energy–water sustainable development. In this work, we elucidate the reaction kinetics, crystalline structure and chemical composition of the resulting solid precipitate obtained from simulated N and P containing wastewater solution using widely abundant low solubility magnesite (MgCO 3 ) particles in the presence of common transition metal ions, such as zinc (Zn 2+ ) or copper (Cu 2+ ). We show that up to 100 ppm Zn 2+ from the simulated wastewater can be incorporated into the struvite lattice as isolated distorted Zn 2+ while even at very low concentrations of ∼5 ppm Cu 2+ ions almost completely inhibit struvite crystal formation. The resulting solid precipitate distinctly affects soil microbial biomass carbon and soil dehydrogenase enzyme activity. These results show a cautionary case where abundant natural mineral MgCO 3 exhibits very different chemistry in Cu 2+ containing simulated wastewater and does not readily adsorb or retain NH 4 + and PO 4 3− ions, unlike less sustainable but more water-soluble magnesium sources, such as MgCl 2 , at the equivalent [Mg 2+ ] : [NH 4 + ] : [PO 4 3− ] molar ratio of 1.4 : 1 : 1.
  2. Copper-antimony-sulfide compounds have desirable earth-abundant compositions for application in renewable energy technologies, such as solar energy and waste heat recycling. These compounds can be synthesized by bottom-up, solution-phase techniques that are more energy and time efficient than conventional solid-state methods. Solution-phase methods typically produce nanostructured materials, which adds another dimension to control optical, electrical, and thermal material properties. This study focuses on a modified-polyol, solution-phase synthesis for tetrahedrite (Cu 12 Sb 4 S 13 ), a promising thermoelectric material with potential also for photovoltaic applications. To dope the tetrahedrite and tune material properties, the utility of the modified polyol synthetic approach has been demonstrated as a strategy to produce phase-pure tetrahedrite that incorporates transition metal (Fe, Co, Ni, Zn, Ag) dopants for Cu, Te dopant for Sb, and Se for S. Six of these reported tetrahedrite compounds have not previously been made by solution-phase methods. For the bottom-up formation of the tetrahedrite nanomaterials, the evolution of the chemical phases has been determined by an investigation of the reaction progress as a function of temperature and time. Digenite (Cu 1.8 S), covellite (CuS), and famatinite (Cu 3 SbS 4 ) are identified as key intermediates and are consistently observed for bothmore »undoped and doped tetrahedrites. The effect of nanostructuring and doping tetrahedrite on thermal properties has been investigated. It was found that nanostructured undoped tetrahedrite has reduced thermal stability relative to samples made by solid-state methods, while the addition of dopants for Cu increased the thermal stability of the material. Crystallinity, composition, and nanostructure of products and intermediates were characterized by powder X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy, and transmission electron microscopy. Thermal properties were investigated by differential scanning calorimetry and thermal gravimetric analysis. This synthetic study with thermal property analysis demonstrates the potential of the modified polyol method to produce tetrahedrite and other copper-antimony-sulfide compounds for thermoelectric and photovoltaic applications.« less
  3. Heavy metal ions are highly toxic and widely spread as environmental pollutants. This work reports the development of two novel chelating adsorbents, based on the chemical modifications of graphene oxide and zirconium phosphate by functionalization with melamine-based chelating ligands for the effective and selective extraction of Hg( ii ) and Pb( ii ) from contaminated water sources. The first adsorbent melamine, thiourea-partially reduced graphene oxide (MT-PRGO) combines the heavier donor atom sulfur with the amine and triazine nitrogen's functional groups attached to the partially reduced GO nanosheets to effectively capture Hg( ii ) ions from water. The MT-PRGO adsorbent shows high efficiency for the extraction of Hg( ii ) with a capacity of 651 mg g −1 and very fast kinetics resulting in a 100% removal of Hg( ii ) from 500 ppb and 50 ppm concentrations in 15 second and 30 min, respectively. The second adsorbent, melamine zirconium phosphate (M-ZrP), is designed to combine the amine and triazine nitrogen's functional groups of melamine with the hydroxyl active sites of zirconium phosphate to effectively capture Pb( ii ) ions from water. The M-ZrP adsorbent shows exceptionally high adsorption affinity for Pb( ii ) with a capacity of 681 mg gmore »−1 and 1000 mg g −1 using an adsorbent dose of 1 g L −1 and 2 g L −1 , respectively. The high adsorption capacity is also coupled with fast kinetics where the equilibrium time required for the 100% removal of Pb( ii ) from 1 ppm, 100 ppm and 1000 ppm concentrations is 40 seconds, 5 min and 30 min, respectively using an adsorbent dose of 1 g L −1 . In a mixture of six heavy metal ions at a concentration of 10 ppm, the removal efficiency is 100% for Pb( ii ), 99% for Hg( ii ), Cd( ii ) and Zn( ii ), 94% for Cu( ii ), and 90% for Ni( ii ) while at a higher concentration of 250 ppm the removal efficiency for Pb( ii ) is 95% compared to 23% for Hg( ii ) and less than 10% for the other ions. Because of the fast adsorption kinetics, high removal capacity, excellent regeneration, stability and reusability, the MT-PRGO and M-ZrP are proposed as top performing remediation adsorbents for the solid phase extraction of Hg( ii ) and Pb( ii ), respectively from contaminated water.« less
  4. Abstract Labile low-molecular-mass (LMM) transition metal complexes play essential roles in metal ion trafficking, regulation, and signalling in biological systems, yet their chemical identities remain largely unknown due to their rapid ligand-exchange rates and weak M–L bonds. Here, an Escherichia coli cytosol isolation procedure was developed that was devoid of detergents, strongly coordinating buffers, and EDTA. The interaction of the metal ions from these complexes with a SEC column was minimized by pre-loading the column with 67 ZnSO 4 and then monitoring 66 Zn and other metals by inductively coupled plasma mass spectrometry (ICP-MS) when investigating cytosolic ultrafiltration flow-through-solutions (FTSs). Endogenous cytosolic salts suppressed ESI-MS signals, making the detection of metal complexes difficult. FTSs contained ca. 80 µM Fe, 15 µM Ni, 13 µM Zn, 10 µM Cu, and 1.4 µM Mn (after correcting for dilution during cytosol isolation). FTSs exhibited 2–5 Fe, at least 2 Ni, 2–5 Zn, 2–4 Cu, and at least 2 Mn species with apparent masses between 300 and 5000 Da. Fe(ATP), Fe(GSH), and Zn(GSH) standards were passed through the column to assess their presence in FTS. Major LMM sulfur- and phosphorus-containing species were identified. These included reduced and oxidized glutathione, methionine, cysteine, orthophosphate, and common mono- and di-nucleotides such as ATP,more »ADP, AMP, and NADH. FTSs from cells grown in media supplemented with one of these metal salts exhibited increased peak intensity for the supplemented metal indicating that the size of the labile metal pools in E. coli is sensitive to the concentration of nutrient metals.« less
  5. After release into the aquatic environment, engineered nanomaterials (ENMs) undergo complex chemical and physical transformations that alter their environmental fate and toxicity to aquatic organisms. Hyalella azteca are sediment-dwelling amphipods predicted to have a high exposure level to ENMs and have previously shown to be highly sensitive to ZnO nanoparticles (NPs). To investigate the impacts of environmentally transformed ZnO NPs and determine the route of uptake for these particles, we exposed H. azteca to ZnSO 4 , ZnO NPs, and environmental aged ZnO NPs which resulted in three types of particles: 30 nm ZnO–Zn 3 (PO 4 ) 2 core–shell structures (p8-ZnO NPs), micron scale hopeite-like phase Zn 3 (PO 4 ) 2 ·4H 2 O (p6-ZnO NPs), and ZnS nano-clusters (s-ZnO NPs). Treatments included freshwater, saltwater (3 ppt), and the presence of sediment, with a final treatment where animals were contained within mesh baskets to prevent burrowing in the sediment. Dissolution was close to 100% for the pristine ZnO NPs and phosphate transformed NPs, while s-ZnO NPs resulted in only 20% dissolution in the water only exposures. In the freshwater exposure, the pristine and phosphate transformed ZnO NPs were more toxic (LC 50 values 0.11–0.18 mg L −1 )more »than ZnSO 4 (LC 50 = 0.26 mg L −1 ) and the s-ZnO NPs (LC 50 = 0.29 mg L −1 ). Saltwater treatments reduced the toxicity of ZnSO 4 and all the ZnO NPs. In the presence of sediment, water column concentrations of Zn were reduced to 10% nominal concentrations and toxicity in the sediment with basket treatment was similarly reduced by a factor of 10. Toxicity was further reduced in the sediment only treatments where the sediments appeared to provide a refuge for H. azteca . In addition, particle specific differences in toxicity were less apparent in the presence of sediment. Bioaccumulation was similar across the different Zn exposures, but decreased with reduced toxicity in the saltwater and sediment treatments. Overall, the results suggest that H. azteca is exposed to ZnO NPs through the water column and NP transformations in the presence of phosphate do not reduce their toxicity. Sulfidized ZnO NPs have reduced toxicity, but their similar level of bioaccumulation in H. azteca suggests that trophic transfer of these particles will occur.« less