Synthesis Of Struvite Research Articles

Cesium immobilization from aqueous solution by struvite synthesis

ABSTRACT To demonstrate the validity of the Cs decontamination process by synthesizing Cs-struvite (CsMgPO4·6 H2O) from a waste solution containing multiple cations, synthesis tests and tests confirming structural stability were performed. The synthesis test was conducted in a solution containing Na, K, Cs, Mg, and P. After 0.5 h stirring, Cs, Mg, and P were recovered, and the sample structure was confirmed as Cs-struvite. With the TG-DTA analysis, the absence of Cs vaporization was confirmed up to 1200°C. The gamma irradiation resistance of Cs-struvite was confirmed. Gamma irradiation using the Co-60 as the radiation source with a maximum radiation dose of 300 kGy caused no loss of Cs or structural changes. The elution test, in which samples were left to stand in distilled water for 7 days, showed that Cs-struvite had a higher water resistance than CsMgPO4, indicating that it is desirable to compress Cs-struvite directly after synthesis to obtain a solidified body with higher water resistance. The results demonstrated the feasibility of Cs removal by Cs-struvite synthesis and the stability of Cs-struvite.

Sustainable Co-Management of Acid Mine Drainage with Struvite Synthesis Effluent: Pragmatic Synergies in Circular Economy

Herein, the alkaline supernatant of a struvite recovery system from municipal wastewater was successfully co-managed with acid mine drainage (AMD). Various ratios (v/v) of AMD to struvite supernatant were examined, and the quality of the passively co-treated effluent and of the generated sludge were examined using state-of-the-art analytical techniques including ICP-OES, FE-SEM/FIB/EDX, XRD, XRF, and FTIR. The optimum ratio was 1:9, where metals and sulphate were largely removed from AMD, i.e., from higher to lower score Fe (~100%) ≥ Pb (~100%) ≥ Ni (99.6%) ≥ Cu (96%) ≥ As (95%) ≥ Al (93.7%) ≥ Zn (92.7%) > Ca (90.5%) > Mn (90%) ≥ Cr (90%) > sulphate (88%) > Mg (85.7%), thus implying that opportunities for mineral recovery could be pursued. The pH of the final effluent was regulated to acceptable discharge levels, i.e., 6.5 instead of 2.2 (AMD) and 10.5 (struvite supernatant), while a notable reduction in the electrical conductivity further implied the attenuation of contaminants. Overall, results suggest the feasibility of the passive co-treatment of these wastewater matrices and that opportunities for direct scaling up exist (e.g., using waste stabilization ponds). Furthermore, apart from the initial recovery of struvite from municipal wastewater, metals could also be recovered from AMD and water could be reclaimed, therefore introducing circular economy and zero liquid discharge in wastewater treatment and management.

Effective removal of ammonia from aqueous solution through struvite synthesis and breakpoint chlorination: Insights into the synergistic effects of the hybrid system

The ever-growing contamination of surface water due to various catchment activities poses threats and stress to downstream water treatment entities. Specifically, the presence of ammonia, microbial contaminants, organic matter, and heavy metals has been an issue of paramount concern to water treatment entities since stringent regulatory frameworks require these pollutants to be removed prior to water consumption. Herein, a hybrid approach that integrates struvite crystallization (precipitation) and breakpoint chlorination (stripping) for the removal of ammonia from aqueous solution was evaluated. To fulfil the goals of this study, batch experimental studies were pursued through the adoption of the well-known one-factor-at-a-time (AFAAT) method, specifically the effects of time, concentration/dosage, and mixing speed. The fate of chemical species was underpinned using the state-of-the-art analytical instruments and accredited standard methods. Cryptocrystalline magnesium oxide nanoparticles (MgO-NPs) were used as the magnesium source while the high-test hypochlorite (HTH) was used as the source of chlorine. From the experimental results, the optimum conditions were observed to be, i.e., Stage 1 – struvite synthesis, 110 mg/L of Mg and P dosage (concentration), 150 rpm of mixing speed, 60 min of contact time, and lastly, 120 min of sedimentation while optimum condition for the breakpoint chlorination (Stage 2) were 30 min of mixing and 8:1 Cl2:NH3 weight ratio. Specifically, in Stage 1, i.e., MgO-NPs, the pH increased from 6.7 to ≥9.6, while the turbidity was reduced from 9.1 to ≤1.3 NTU. Mn removal efficacy attained ≥97.70% (reduced from 174 μg/L to 4 μg/L) and Fe attained ≥96.64% (reduced from 11 mg/L to 0.37 mg/L). Elevated pH also led to the deactivation of bacteria. In Stage 2, i.e. breakpoint chlorination, the product water was further polished by eliminating residual ammonia and TPC at 8:1 Cl2–NH3 weight ratio. Interestingly, ammonia was reduced from 6.51 to 2.1 mg/L in Stage 1 (67.74% removal) and then from 2.1 to 0.002 mg/L post breakpoint chlorination (99.96% removal), i.e., stage 2. Overall, synergistic and complementary effects of integrating struvite synthesis and breakpoint chlorination hold great promise for the removal of ammonia from aqueous solutions thus confirming that this technology could potentially be used to curtail the effects of ammonia in the receiving environments and drinking water.

Treatment of emerging contaminants in simulated wastewater via tandem photo-Fenton-like reaction and nutrient recovery

Nutrient rich wastewater containing emerging organic contaminants was used for struvite synthesis with a novel tandem process with a heterogeneous Fenton oxidation pretreatment.

Emerging remediation potentiality of struvite developed from municipal wastewater for the treatment of acid mine drainage

The valorisation of wastewaters for minerals recovery and their potential beneficiation has gained enormous attention recently. In this study the removal of phosphate and ammonia from municipal wastewater using activated magnesite resulted in the formation of struvite. The optimum conditions for the synthesis of struvite were 60 min of mixing, 300 rpm mixing speed, 1 g of activated magnesite and room temperature, whilst optimum conditions for the treatment of acid mine drainage (AMD) using the synthesized struvite were 45 min of mixing, 20 g of struvite dosage, 1000 mL, and 300 rpm mixing speed. The efficacy of struvite for neutralisation of AMD and attenuation of inorganic contaminants were ≥98.99% for metals (Al3+, Fe3+, and Mn2+) and ≥30% for SO42−. Traces of other metals such as Zn, Cu, Ni, Pb, and Cr were significantly attenuated. Phosphate was fully attenuated from the aqua-sphere. PHREEQC predicted the removal of minerals as oxy-(hydro)-sulphates, oxy-(hydro)-phosphate, metals hydroxides, and other complexes. FE-SEM equipped with FIB and an EDX, XRD, XRF, and FTIR confirmed the synthesis of struvite and fate of chemical species after treatment. This study confirmed the feasibility of recovering phosphate and ammonia as struvite which can be employed for the treatment of AMD.

Synthesis of Struvite in Aqueous-Salt Systems in which Competing Phases of Magnesium Phosphate Crystal Hydrates of Different Compositions Can Be Formed

Synthesis of Struvite in Aqueous-Salt Systems in which Competing Phases of Magnesium Phosphate Crystal Hydrates of Different Compositions Can Be Formed

Enhanced struvite generation and separation by magnesium anode electrolysis coupled with cathode electrodeposition

Adding magnesium ions (Mg2+) to produce struvite is an important method to recover nitrogen and phosphorus from wastewater. Both the Mg2+ source and subsequent separation of struvite are key factors for the utilization of struvite. In this study, we developed an efficient method to recover nutrient salts from wastewater using sacrificial Mg anodes to generate struvite, with its simultaneous separation through cathode electrodeposition. The anode-released Mg2+ reacted with NH4+-N and PO43−-P in bulk solution to form struvite, which was more intense on the cathode surface due to the relatively higher pH environment from hydrogen evolution, resulting in most of the struvite being deposited on the cathode surface and simultaneously separated out of the bulk solution. Using a cathode with a higher solution-cathode interface area and relatively low current density facilitated struvite deposition. Results showed that under optimal electrolysis condition (5.76 A/m2, pH 8.5, 180 min, and 1.2:1.0 Mg:P), 91% of the undissolved substances as the phosphate precipitation were deposited on the graphite cathode surface, and the proportion of struvite in the deposition reached 41.52%. This study provides a novel electrochemical method for struvite synthesis and separation for the recovery of nitrogen and phosphorus from wastewater.

Electrochemical Synthesis of Struvite from Wastewater: Implications of Chloride Ion and Initial pH

Electrochemical precipitation of magnesium ammonium phosphate (MAP) compounds, specifically as struvite (NH4MgPO4.6H2O) from wastewater is gaining importance as one of the techno-economically feasible pathways of sustainable development [1]. However, systematic exploration of the optimal range of anode potential for maximizing phosphate recovery under varied parametric conditions of pH and ion concentrations, other than NH4 + and PO4 3- has not been attempted so far. Additionally, ion dissolution from sacrificial magnesium anode over stipulated potential range between pitting and secondary passivation needs to be investigated for maximum struvite production with minimal consumption of magnesium. In this study, we have characterized the role of initial pH (4 and 8) and chloride ion concentration (1 M) on phosphate recovery and magnesium dissolution by conducting batch electrochemical experiments with three different anode potentials covering the entire range of feasible potential window. Linear Sweep Voltammetry (LSV) was performed at two different initial pHs to identify the aforementioned potential range. Subsequently, batch experiments at different anode potentials were conducted in an electrochemical cell consisting of pure magnesium sheet as sacrificial anode and stainless steel cathode. 77 mM solution of dihydrogen ammonium phosphate (NH4H2PO4) and 1M sodium chloride was used as electrolyte. Lower value of Pitting potential in presence of chloride ions with respect to that with baseline NH4H2PO4 solution was indicative of the favorable effect of chloride in rupturing the passive layer of magnesium hydroxide that normally forms on anode surface and hinders magnesium dissolution. Higher magnesium dissolution rate and phosphate recovery were recorded above and over respective pitting potentials for both pHs. Moreover, monotonic increasing profiles of precipitate masses with increasing anode potential unambiguously indicates higher dissolution of magnesium with as alternatively reflected in terms of elevated charge transfer as per Faraday’s law. In both cases of different initial pHs, final pH was recorded in alkaline range. Nevertheless, ammonia loss was observed to increase with anode potentials and increasing pH. Precipitates, formed at the surface of anode and in bulk solution, on characterization revealed the presence of several MAP and other magnesium phosphate precipitates including Struvite (MgNH4PO4.6H2O), Dittmarite (MgNH4PO4.H2O), Magnesium phosphate tribasic (Mg3(PO4)2) and Newberyite (MgHPO4.3H2O). Magnesium hydroxide was detected at higher pH. Simulation of saturation indices and product distribution using Visual Minteq 3.1 predicted optimal recovery of Struvite (MgNH4PO4.6H2O) in the pH range 8-10. Reference: [1] Cid, C. A.; Jasper, J. T.; Hoffmann, M. R., Phosphate Recovery from Human Waste via the Formation of Hydroxyapatite during Electrochemical Wastewater Treatment. ACS Sustainable Chem. Eng. 2018, 6 (3), 3135-3142.

XRD-Rietveld analysis as a tool for monitoring struvite analog precipitation from wastewater: P, Mg, N and K recovery for fertilizer production

The objective of this study was to select between four proposed synthesis conditions, which one would be the most propitious for struvite precipitation from wastewater and, on such product, detail its crystallochemical aspects using the Rietveld refinement method to determine the chemical formula and chemistry analyses by Wavelength Dispersive X-ray Fluorescence (WDXRF) for validation. The struvite synthesis was investigated for pH 10 and 12 and phosphorus concentrations of 100 and 300 mg/L under the same room temperature (RT) condition and a magnesium to phosphorus to nitrogen (Mg: P: N) molar ratio of 1: 1: 2. Struvite was successfully obtained under a moderately alkaline pH (10). No struvite precipitation occurred under the same temperature and Mg: P: N molar ratio for a highly alkaline pH (12). Under RT condition, 300 mg/L P, a Mg: P: N molar ratio of 1: 1: 2, and a pH of 10, a product with two struvite phases was obtained: an 75% struvite analog ([K0.34(NH4)0.66]MgPO4.6H2O) and 25% struvite (NH4MgPO4.6H2O). Last, the Rietveld tool is useful for monitoring struvite production from wastewaters, since the chemical ratio (stoichiometry of the phase) is what will define its classification in: struvite, struvite analog, K-struvite or mixed. In addition, it will help in the classification of the fertilizer product (chemical content of nutrients).

Optimal Anode Potential Range for Electrochemical Synthesis of Struvite from Wastewater

Electrochemical recovery of phosphorous and nitrogen from wastewater as struvite (NH4MgPO4.6H2O) is progressively gaining importance as one of the innumerable pathways of sustainable development. However, the optimal range of anode potential that maximizes struvite purity under varied parametric conditions of pH and ion concentrations other than NH4 +and PO4 -3 has not been methodically explored so far. Additionally, corrosion behavior of a sacrificial magnesium anode under an anode potential range needs to be investigated because according to techno-economic feasibility criterion, it is advantageous to produce struvite with minimal consumption of magnesium. In this study, we will report on the effects of pH (4 and 8) and chloride ion concentration (0.1 M to 1 M) on struvite production and magnesium dissolution rates through performing a systematic investigation using Linear Sweep Voltammetry (LSV) and Potentiodynamic Polarization (PDP) techniques. Aqueous solutions of dihydrogen ammonium phosphate with varied chloride ion concentration are used as simulated wastewater. Electrochemical experiments are conducted in batch mode with a sacrificial magnesium anode and a stainless-steel cathode. Furthermore, bulk and electrode surface (both anode and cathode) precipitates are analyzed for elemental composition, crystallinity,and morphological features. The present research outcomes are expected to serve as a baseline protocol to select an optimal anode potential window in electrochemical struvite production from wastewater.

Advocating circular economy in wastewater treatment: Struvite formation and drinking water reclamation from real municipal effluents

• This study proved the feasibility of valorizing municipal effluents. • Simultaneous synthesis of struvite and drinking water reclamation was achieved. • This circular economic approach can produce 81,600 L/day of drinking water. • The synthesized struvite can amount up to 1260 kg/day. In this pilot study, the circular economy concept in wastewater treatment was examined, through a zero liquid discharge (ZLD) process where struvite was recovered and drinking water was reclaimed. A stage wise approach was followed for struvite formation and the subsequent reclamation of drinking water. Specifically, the early stages of treatment entail the synthesis of struvite via the chemical precipitation of nutrients (phosphate and ammonia), using thermally activated cryptocrystalline magnesite. Thence, reverse osmosis (RO) was employed for drinking water reclamation. With this dual approach, 3.5 m 3 of municipal wastewater were successfully treated at a pilot plant in South Africa, producing ∼52.5 kg of struvite and ∼3.4 m 3 of drinking water. The operating parameters were 30 min of residence time, 0.5 g : 500 mL solid to liquid (S/L) ratio, using ambient temperature and pH. X-ray diffraction (XRD) and High Resolution Scanning Electron Microscopy (HR-SEM) coupled with electron dispersion spectroscopy (EDS) confirmed the synthesis of struvite and the presence of notable Mg/P ratios. Fourier Transform Infrared Spectrometer (FTIR) further ascertained the obtained results. Moreover, it was identified that the reclaimed water meets the South African National Standard (SANS) 241:2015 and the world health organisation (WHO) standards for drinking water. An economic analysis revealed the viability of the process, suggesting that the system could be self-sustainable. Therefore, the results of this work indicate that introducing the concept of circular economy in wastewater treatment can promote the sustainable management of the ever-increasing quantities of municipal wastewater and at the same time address problems of emerging concern, such as water scarcity and phosphate shortage.

Phosphorus removal from livestock effluents: recent technologies and new perspectives on low-cost strategies.

Phosphorus is an essential element in the food production chain, even though it is a non-renewable and limited natural resource, which is going to run out soon. However, it is also a pollutant if massively introduced into soil and water ecosystems. This study focuses on the current alternative low-cost technologies for phosphorus recovery from livestock effluents. Recovering phosphorus from these wastewaters is considered a big challenge due to the high phosphorus concentration (between 478 and 1756mgL-1) and solids content (> 2-6% of total solids). In particular, the methods discussed in this study are (i) magnesium-based crystallization (struvite synthesis), (ii) calcium-based crystallization, (iii) electrocoagulation and (iv) biochar production, which differ among them for some advantages and disadvantages. According to the data collected, struvite crystallization achieves the highest phosphorus removal (> 95%), even when combined with the use of seawater bittern (a by-product of sea salt processing) instead of magnesium chloride pure salt as the magnesium source. Moreover, the crystallizer technology used for struvite precipitation has already been tested in wastewater treatment plants, and data reported in this review showed the feasibility of this technology for use with high total solids (> 5%) livestock manure. Furthermore, economic and energetic analyses here reported show that struvite crystallization is the most practicable among the low-cost phosphorus recovery technologies for treating livestock effluents.

Transition metal-doped MgO nanoparticles for nutrient recycling: an alternate Mg source for struvite synthesis from wastewater

Nanostructured MgO doped with transition metals has been used to recycle nutrients from wastewaterviastruvite crystallization.

Optimization of phosphate recovery as struvite from synthetic distillery wastewater using a chemical equilibrium model.

This study investigates the feasibility of recovery of phosphorus via struvite precipitation from a synthetic anaerobically treated distillery spent wash by optimizing the process using a chemical equilibrium model, namely Visual MINTEQ. Process parameters such as Mg2+, [Formula: see text], and [Formula: see text] ion concentrations and pH were used as inputs into the model. Increasing the molar ratio of [Formula: see text] from 0.8:1 to 1.6:1 at pH 9 led to an increase in phosphate recovery from 88.2 to 99.5%. The model and experimental results were in good agreement in terms of phosphate recovery, indicating that the Visual MINTEQ model can be used to pre-determine the process parameters for struvite synthesis. Increasing the concentration of calcium ion adversely affected the synthesis and purity of struvite, whereas the presence of melanoidins had no significant impact. This study demonstrates that phosphorus recovery through struvite precipitation is a sustainable approach to reclaim phosphorus from high-strength industrial wastewater.

Spatially Resolved Product Speciation during Struvite Synthesis from Magnesite (MgCO3) Particles in Ammonium (NH4+) and Phosphate (PO43–) Aqueous Solutions

While population growth necessitates a significant increase in crop production, stringent environmental regulations require that it be done using sustainable nutrient sources. Nutrients in the form...

Bioinspired Struvite Mineralization for Fire-Resistant Wood.

High-performance wood materials have attracted significant attention in recent years because of excellent property profiles achieved by relatively easy top-down processing of a renewable resource. A crucial flaw of the renewable wood scaffolds is the low flame retardancy, which we tackled by bioinspired mineralization in an eco-friendly processing step. The formation of the biomineral struvite, commonly found in urinary tract stones, was used for the infiltration of hierarchical wood structures with the necessary ions followed by an in situ synthesis of struvite by ammonium steam fumigation. Struvite decomposes prior to wood, which absorbs heat and releases nonflammable gas and amorphous MgHPO4 resulting from the degradation, which promotes insulating char formation. As a result, the mineralized wood can hardly be ignited and the treatment strongly suppresses the heat release rate and smoke production.

Hydrothermal synthesis of struvite and its phase transition: Impacts of pH, heating and subsequent cooling methods

MAP (magnesium, ammonium, and phosphate) precipitation under hydrothermal condition was investigated in the present study. The hydrothermal mediated solution of a MAP in equimolar ratios (1:1:1) was prepared for crystal growth in a reactor autoclave. In the hydrothermal experiments, the reactor was heated in a furnace at varying temperatures (60, 80 and 120 °C) for 24 h, and then followed by (i) air cooling and (ii) water quenching to room temperature. Struvite could be formed in the solution with initial pH values (7–10) when the reactor worked at 60 °C for 24 h and was subsequently air-cooled and water-quenched to room temperature. Working with the temperature of 80 °C and subsequent air cooling yielded struvite, dittmarite, and newberyite in the solution with pH values of 9 and 10. By heating reactor at temperatures of 80 and 120 °C and water quenching, however, a pure dittmarite could be grown in the solution with any pH values (7–10). Dittmarite was also the major phase precipitated in the solution with any pH condition at 120 °C for the longer reaction time (96 h). A small impurity of sylvite was unexpectedly co-precipitated in all processes. SEM micrograph showed that the crystal solids have irregular prismatic-shaped morphology. The optimal pH for MAP crystallization was predicted to be about 9. The present results provided valuable information for the understanding of phosphate recovery from effluent by the hydrothermal treatment.

Synthesis of Struvite using a Vertical Canted Reactor with Continuous Laminar Flow Process

Struvite is a white crystalline that is chemically known as magnesium ammonium phosphorus hexahydrate (MgNH4PO4·6H2O). It can easily dissolve in acidic conditions and slightly soluble in neutral and alkaline conditions. In industry, struvite forms as a scale deposit on a pipe with hot flow fluid. However, struvite can be used as fertilizer because of its phosphate content. A vertical canted reactor is a promising technology for recovering phosphate levels in wastewater through struvite crystallization. The study was carried out with the vertical canted reactor by mixing an equimolar stock solution of MgCl2, NH4OH, and H3PO4 in 1: 1: 1 ratio. The crystallization process worked with the flow rate of three stock solution entering the reactor in the range of 16-38 ml/min, the temperature in the reactor is worked on 20°, 30°, and 40°C, while the incoming air rate is kept constant at 0.25 liters/min. Moreover, pH was maintained at a constant value of 9. The struvite crystallization process run until the steady state was reached. Then, the result of crystal precipitates was filtered and dried at standard temperature room for 48 hours. After that, struvite crystals were stored for the subsequent analysis by Scanning Electron Microscope (SEM) and XRD (X-Ray Diffraction) method. The use of canted reactor provided the high pure struvite with a prismatic crystal morphology.

Synthesis of struvite (MgNH4PO4·6H2O) and its use for sorption of nickel ions

The influence of the conditions of the struvite synthesis on its ability to form crystals with developed faces of different forms (hkl) and on the possibility of the subsequent transition to more stable forms was examined. The correlation between the ζ-potential of the struvite particle surface, struvite crystal size, and tendency to form agglomerates was demonstrated. The sorption rate in the system consisting of struvite, nickel ions, ammonium ions, and water can be increased by combining the internal diffusion and recrystallization of the solid interaction products. The possibility of enhancing the sorption performance by properly choosing the anionic composition of solutions of nickel salts for the sorption was revealed. The conditions for preparing struvite for its use as agent for improvement of contaminated soils to immobilize heavy metal ions were substantiated.

Biomimetic synthesis of struvite with biogenic morphology and implication for pathological biomineralization.

Recent studies have found that certain urinary proteins can efficiently inhibit stone formation. These discoveries are significant for developing effective therapies for stone disease, but the inhibition mechanism of crystallization remains elusive. In the present study, polyaspartic acid (PASP) was employed as a model peptide to investigate the effect of urinary proteins on the crystallization and morphological evolution of struvite. The results demonstrate that selective adsorption/binding of PASP onto the {010} and {101} faces of struvite crystals results in arrowhead-shaped morphology, which further evolves into X-shaped and unusual tabular structures with time. Noticeably, these morphologies are reminiscent of biogenic struvite morphology. Concentration-dependent experiments show that PASP can inhibit struvite growth and the inhibitory capacity increases with increasing PASP concentration, whereas aspartic acid monomers do not show a significant effect. Considering that PASP is a structural and functional analogue of the subdomains of aspartic acid-rich proteins, our results reveal that aspartic acid-rich proteins play a key role in regulating biogenic struvite morphology, and aspartic acid residues contribute to the inhibitory capacity of urinary proteins. The potential implications of PASP for developing therapeutic agents for urinary stone disease is also discussed.