Search Results (248)

A modern approach to the organization of wastewater disposal systems ensures the sustainable development of resort areas. Warm mineral springs (WMSs) located in suburban areas are not only recreational facilities for the population, but also sources of used mineral and communal wastewater. Preventing or reducing the discharge of pollutants in this type of liquid waste can reduce the anthropogenic impact on the environment. The article proposes a method for the chemical precipitation of ammonium ions in a mixture of mineral and domestic wastewater, and the production of struvite, a complex agricultural fertilizer. Three series of experiments were conducted: (1) on a model solution of ammonium ions; (2) on a mixture of a model solution and real mineral water; and (3) on real wastewater and spent mineral water taken from a thermal resort. As a result of an experiment with water samples at an initial concentration of no more than 85 mg/L, optimal doses of reagents were identified: 5.67 g/L of sodium hydrophosphate and 3.21 g/L of magnesium chloride to achieve a residual concentration of ammonium ions in purified water of no more than 1.5 mg/L at pH = 9–10. In the case of mixing of domestic wastewater and used mineral water, it was possible to reduce the use of magnesium chloride by 80%. At the same time it was possible to obtain the amount of sediment containing struvite, which is a valuable agricultural fertilizer. With the introduction of this technology, it is possible to reduce the expenses of reagents and reduce the damage caused by the discharge of liquid waste from a thermal resort, while the profit earned through the sale of fertilizer can partially offset the cost of wastewater disposal. Full article

Phimosis is rarely reported in cats and involves the inability to exteriorize the penis through an absent or abnormally narrowed preputial orifice. This case report describes the clinical presentation, surgical management, and outcome of two male domestic shorthair kittens with suspected congenital type II phimosis. Both cats presented with recurrent stranguria and dysuria, preputial swelling, urine pooling or dribbling, a markedly stenotic preputial orifice, and penile–preputial adhesions. In Case 1, cystic struvite urolithiasis was also identified; treatment included cystotomy and ventrally performed modified preputial urethrostomy because of extensive adhesions, penile hypoplasia, and limited penile mobility. In Case 2, adhesions were limited to the distal penis and were released, allowing circumferential preputioplasty. No postoperative complications occurred. Clinical signs resolved, and normal urination was recorded during available follow-up, which was 12 months in Case 1 and 2 months in Case 2. The congenital origin was suspected based on early onset of clinical signs but could not be definitively confirmed. These cases suggest that selected feline type II phimosis cases can be managed successfully by tailoring surgery to anatomical abnormalities, using ventral-modified preputial urethrostomy when adhesions and penile hypoplasia restrict mobilization, or circumferential preputioplasty when adhesions are limited distally. Full article

Turning waste materials into renewed value is a central aspect of any future circular (bio)economy. Urine and ash are two prominent waste materials produced globally and in considerable amounts each year. Both contain several interesting substances that are so far de facto lost or may even pose a threat to the environment. Urine from industrial-scale farming, for instance, is responsible for significant pollution of soil and groundwater with nitrogen and phosphorous, yet N and P are also high-demand substances in agriculture and industry. Similarly, ash is rich in several interesting metal ions, but is still usually disposed of in a landfill. Using a sequence of simple yet effective biological and chemical processes, it may be possible to convert these two unwanted materials into “green” ammonia and calcium phosphate, both valuable high-demand substances with numerous applications, and with few potentially valuable leftovers still to be dealt with. Eventually, and after considering some of the logistics of the process, such as the collection of materials, this “urinash process” may be upscaled to effectively reduce waste by turning it into renewed value, thus also substituting for—some of—both the energy-intensive synthesis of grey ammonia and the destructive mining for phosphate salts. Full article

Background/Objectives: Osteoporosis poses significant obstacles as it causes an imbalance between osteoblasts and adipocytes, which results in the disruption of bone homeostasis. Although various magnesium-based scaffolds have been deployed for the treatment of osteoporotic bone defects, whether this can be achieved by alleviating bone–fat imbalance still requires further elucidation. Methods: We designed magnesium phosphate-based platforms (GMPCs), based on magnesium photopolymerized methacrylated gelatin (GelMA) and phosphate (K-struvite, MPC), and used them to deliver magnesium ions (Mg²⁺) for alleviating bone–fat imbalance locally. Results: The in vivo results demonstrated that the GMPCs not only improved osteogenic behavior at the implanted site, but also reduced the proportion of adipose tissues in a femoral defect model in 18-month-old SD rats. Moreover, by promoting the differentiation of bone marrow mesenchymal stem cells (BMSCs) into osteoblasts in a concentration-dependent manner, GMPCs significantly reduced adipogenic differentiation in vitro. Also, 5GMPC demonstrated the best comprehensive biologic properties compared to other platforms. Conclusions: GMPCs have great potential in the treatment of age-related osteoporosis via the effective delivery of Mg²⁺. Full article

Forward osmosis (FO) offers a promising route for urine concentration and nutrient recovery, yet inorganic scaling under high water recovery remains a significant challenge. This study systematically investigated scaling during FO treatment of synthetic fresh urine (SFU) and synthetic hydrolysed urine (SHU) over three consecutive cycles to 80% water recovery. SFU exhibited moderate flux decline (~14.4 → 4–5 LMH), with minimal hydraulic resistance from sparse calcium-deficient Ca–P deposits (Ca:P ≈ 1.2; ACP/OCP-like). In contrast, SHU caused severe cumulative scaling, progressively reducing flux from 19 → 14.46 → 1.3 LMH, dominated by struvite (Mg:P ≈ 1.02) and mixed Mg–carbonate phases. Visual MINTEQ thermodynamic modelling correctly identified the dominant mineral families in both feeds, while kinetic effects governed the formation of metastable phases, demonstrating that equilibrium modelling and experimental characterisation are complementary tools for scaling prediction under transient FO conditions. Physical cleaning restored ~98–99% of water flux for both feeds, confirming that even severe SHU-induced scaling is largely hydraulically reversible. High rejection of multivalent ions (PO₄³⁻, Mg²⁺, and Ca²⁺) was maintained throughout, confirming membrane integrity was preserved despite severe scaling. These findings demonstrate that urine hydrolysis fundamentally governs scaling pathways, severity, and reversibility in FO systems, and that simple hydraulic flushing is an effective fouling-control strategy, providing practical guidance for operating condition selection and cleaning strategy design in FO-based urine treatment applications. Full article

Sustainable phosphorus (P) management in agriculture requires a circular economy approach through the use of so-called bio-based fertilizers (BBFs). The properties of BBFs vary widely depending on raw materials and production processes. However, it is still unknown how these properties, and particularly the dominant P compounds determine not only the efficiency of BBFs in supplying P to crops, but also their effects on soil functioning and crop quality. This study aimed to evaluate the efficiency of a representative set of BBFs, and relate this efficiency to their composition and dominant P compounds. To this end, 14 BBFs were studied: four from water purification (struvite, vivianite, and sewage sludge with and without composting), four composts (municipal solid waste (MSW), vineyard residues, and two using olive husks), three vermicomposts (two homemade and one commercial), fish meal, digestate, and a commercial organic fertilizer. Phosphorus forms in BBFs were determined using ³¹P nuclear magnetic resonance spectroscopy (P-NMR). The BBFs were compared to a single superphosphate (SSP) in a pot experiment growing wheat in two different alkaline soils, one rich in iron (Fe) oxides and one rich in carbonates. The effects on critical elements in grain [magnesium, Fe, zinc (Zn), manganese, and copper] and enzyme activities related to soil functioning and P cycling were also assessed. The dominant P compound in the BBFs was orthophosphate (73.8–89.5% of the total P in the NaOH–EDTA extracts). The MSW had the highest polyphosphate content (4.1%), a complex inorganic P compound. The organic P content ranged from 9.2% (fish meal) to 25.5% (Moge). Sewage sludge and composted sludge contributed high levels of phosphonates (4.1 and 5.6% of extracted P). The most abundant organic P compound class was inositol hexakisphosphates (IHPs), and myo-IHP (phytate) was the dominant IHP stereoisomer (1.2–6.4%) followed by D-chiro-IHP and scyllo-IHP. Plant dry matter and grain yield with most BBFs were not significantly different from that of SSP in both soils, likely due to the high concentrations of phosphate in relatively soluble forms in most of the BBFs. Vivianite and sewage sludge resulted in significantly higher grain yield than SSP (43% and 40%, respectively) in the carbonate-rich soil, likely due to progressive phosphate dissolution, which decreased the precipitation rate of insoluble calcium (Ca) phosphates. The highest P recoveries were obtained with horse manure vermicompost (65% and 15% higher than SSP in the Fe oxide-rich and in the carbonate-rich soil, respectively), partially attributed to the decreased precipitation rate of insoluble Ca phosphates with the added organic matter. Some BBFs increased micronutrient concentrations in grains and most decreased the P-to-Zn ratio relative to SSP. Overall, phosphatase and β-glucosidase activities increased with carbon-rich BBFs. Most of the studied BBFs could effectively replace fertilizers from non-renewable sources, in some cases with better crop P recoveries. Furthermore, some BBFs could provide additional benefits to grain quality, in terms of micronutrient supply for humans, and soil functioning. Full article

Phosphorus is an essential and finite resource critical for global food production, yet its inefficient use and discharge from wastewater systems contribute to eutrophication and resource depletion. The transition from conventional wastewater treatment plants to water resource recovery facilities has intensified interest in technologies that enable phosphorus recovery within a circular economy framework. This review provides a critical and up-to-date synthesis of phosphorus recovery strategies from wastewater, with primary emphasis on struvite (MgNH₄PO₄·6H₂O) crystallization as one of the most mature and practically implemented recovery routes. The occurrence and chemical forms of phosphorus in wastewater streams are discussed alongside conventional approaches, such as enhanced biological phosphorus removal and chemical precipitation, in order to position struvite recovery within the broader phosphorus management landscape. In addition to struvite crystallization, selected competing and complementary recovery pathways, including electrochemical systems, biochar-assisted processes, and sludge ash recovery, are discussed to compare technological maturity, recovery potential, and practical applicability. Particular attention is given to reactor configurations, full-scale applications, and commercial technologies to assess operational reliability, recovery performance, and fertilizer product quality. Life-cycle assessment results and regulatory developments are also discussed to contextualize sustainability claims, technology selection, and market integration. The review identifies key technical and economic challenges, particularly regarding magnesium supply, competing ions, wastewater matrix effects, and the feasibility of mainstream application. Overall, controlled sidestream struvite crystallization appears to offer the most favorable balance between recovery efficiency, operational reliability, and fertilizer product quality under suitable plant conditions. Full article

To develop a high-performance inorganic fireproof coating suitable for steel structures, this study utilized magnesium phosphate cement (MPC) as the matrix and introduced expanded perlite (EP) as a lightweight aggregate. The effects of EP content (40–55%) and magnesium-to-phosphorus ratio (M/P = 4:1–7:1) on the dry density, compressive strength, bond strength, and fire resistance of the coating were systematically investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) were employed to reveal the phase evolution and microstructure evolution mechanisms at high temperatures. The results indicate that increasing EP content significantly reduces the dry density and thermal conductivity of the coating, enhancing thermal insulation performance. However, excessive incorporation leads to the deterioration of mechanical properties, with an optimal EP content of 45%. The M/P ratio influences the interfacial bond strength and high-temperature structural stability by regulating the proportion of the hydration product K-struvite (KMgPO₄·6H₂O) and residual MgO. Compressive strength peaked at M/P = 6:1 (0.80 MPa), while bond strength was optimal at M/P = 5:1 (0.097 MPa), corresponding to the best fire resistance (back-side temperature of 180.4 °C). At high temperatures, K-struvite dehydrates and transforms into anhydrous KMgPO₄, which, together with residual MgO and crystallized SiO₂ from EP, forms a dense ceramic skeleton, ensuring the structural integrity of the coating. Comprehensive performance evaluation determined the optimal mix ratio as M/P = 5:1 and EP content = 45%. The coating with this ratio exhibits a dry density of approximately 560 kg/m³, a 14-day compressive strength of 0.53 MPa, a bond strength of 0.097 MPa, and a back-side temperature of 180.4 °C under flame exposure, demonstrating a favorable balance of lightweight character, mechanical integrity, and thermal insulation performance suitable for steel structure fire protection applications. Full article

Magnesium potassium phosphate cement (MKPC) is a promising bone repair material but suffers from excessively rapid setting time (typically within minutes) that limits clinical application. This study systematically investigates trimagnesium phosphate (TMP) as a candidate retarding additive for MKPC. TMP was used to partially replace dead-burned magnesium oxide at replacement levels of 0%, 10%, and 15% by mass. The effects of TMP content, water-to-cement ratio (0.17–0.23), and magnesium-to-phosphate molar ratio (4–10) on setting time, fluidity, hydration kinetics, compressive strength, and microstructure were comprehensively evaluated. Results show that TMP effectively extends the setting time from 9–13 min (without TMP) to 10–19 min, providing a working window that may be suitable for biomedical applications requiring extended handling time. Notably, 10% TMP incorporation enhances early compressive strength, with 1-day strength reaching 35.2 MPa compared to 28.5 MPa for control samples. Hydration heat analysis reveals TMP moderates the acid-base reaction kinetics through its slower dissolution rate compared to MgO. Microstructural characterization shows TMP promotes the formation of denser K-struvite crystals with refined microstructure. The optimal TMP dosage of 10% achieves a balanced performance, extending setting time while improving early strength and microstructural densification. These findings establish TMP as an effective retarder for developing MKPC-based materials with potential for biomedical applications, pending further biological validation. Full article

Canine urolithiasis is a common and highly recurrent urinary tract disease, with struvite and calcium oxalate being the predominant stone types. Stone formation has traditionally been attributed to urinary physicochemical factors, including urine pH, mineral supersaturation, and urinary tract infection. However, these factors alone cannot fully explain the persistent growth and rapid progression of stones in affected dogs. In this study, we provide evidence that innate immune mechanisms, particularly neutrophil extracellular traps (NETs), are associated with canine urolith formation. We found that neutrophils, key cells of the innate immune system, release neutrophil extracellular traps composed of DNA and antimicrobial proteins, which are consistently present within urinary stones and their surrounding microenvironments. Common canine urinary pathogens were shown to trigger this response, and these immune-derived structures promoted crystal nucleation, aggregation, and stone growth in experimental systems. Importantly, enzymatic degradation of NETs by DNase I attenuated NET-associated stone growth under in vitro conditions. These findings suggest that canine urinary stones develop not only as a consequence of physicochemical factors, but also in association with inflammation-driven biomineralization processes involving NETs. Recognizing the contribution of innate immunity provides new insight into stone recurrence and may inform future preventive and therapeutic strategies. Full article

Infection urinary stones account for approximately 10–15% of all urinary stones worldwide, with a rising incidence observed in recent decades, particularly in countries with a high Socio-Demographic Index (SDI). This trend has been partially attributed to dietary changes, including increased consumption of processed foods. Heavy metals belong to a group of substances, the source of which can be both food and the human environment. Among many heavy metals, in this study, we focus on copper and investigate its influence on the nucleation and growth of struvite crystals, the primary component of infection urinary stones. Experiments were conducted in artificial urine, both in the presence and absence of Proteus mirabilis, a urease-producing bacterium commonly associated with infection urinary stones. In a bacteria-free system, bacterial urease activity was mimicked by the addition of aqueous ammonia solution. Our results demonstrate that the presence of copper in artificial urine induces a slight shift in the struvite crystallization toward lower pH values, indicating that crystal formation initiates earlier compared to a control test. Additionally, the amount of precipitated struvite increases modestly in the presence of copper. Struvite crystals formed in copper-containing artificial urine are larger and exhibit altered habit and morphology. Energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) analyses confirm that copper does not incorporate into either the bulk or surface structure of the struvite crystals. X-ray diffraction (XRD) data show that struvite remains the sole crystalline phase, consistent with the control samples. Microbiological assays reveal that copper, at the concentrations tested, does not affect the viability of P. mirabilis, indicating an absence of bacteriostatic or bactericidal effects. To elucidate the physicochemical mechanisms underlying copper’s influence on nucleation and growth of struvite, speciation analysis of chemical complexes was performed. This revealed the formation of various copper complexes in artificial urine, including Cu(OH)⁺, CuCit⁻, CuC₂O₄, Cu(OH)₂, CuHPO₄, Cu(NH₃)²⁺, Cu(NH₃)₂²⁺, and Cu(NH₃)₃²⁺. These chemical complexes modulate the equilibrium and formation of complexes with Mg²⁺ and PO₄³⁻ (e.g., MgHCit, MgCit⁻, MgOH⁺, MgC₂O₄, MgSO₄, MgHPO₄), contributing to the observed shift in struvite crystallization to lower pH values. Full article

Long-term deterioration of concrete due to synergistic dry–wet cycles and sulfate attack significantly compromises the structural durability and integrity. CFRP-reinforced concrete offers a promising solution for repair and performance enhancement under such adverse conditions. In addition, binder selection is critical to the reinforcement efficacy. However, traditional epoxy (EP) binders have certain limitations in environmental adaptability and sustainability, necessitating alternative approaches. Thus, inorganic magnesium phosphate cement (MPC) binders have garnered attention due to their rapid hardening, early strength, interface compatibility, and environmental benefits. Nevertheless, the durability of MPC under combined sulfate exposure and dry–wet cycles, as well as the performance of CFRP-bonded concrete using MPC, has remained underexplored. In this study, the chemical, microstructural, pore, and mechanical properties of MPC mortar and MPC–CFRP concrete columns subjected to sulfate dry–wet cycles were systematically investigated and compared to ordinary and EP–CFRP concretes. The results indicate that MPC mortar forms struvite during sulfate dry–wet cycles, though the struvite content decreases with increasing cycles. In addition, the porosity of MPC mortar initially decreases and then increases, reaching a maximum of 1.52. The resulting compressive and flexural strengths of MPC mortar decline over cycles, reaching 28.4 MPa and 8.4 MPa, respectively, after 240 cycles. For concrete columns, sulfate dry–wet cycles result in significant sulfate crystallization on EP–CFRP surfaces, whereas MPC–CFRP columns show reduced crystallization and improved ductility. After 240-day cycles, compressive strengths of ordinary, EP–CFRP, and MPC–CFRP columns were 17.64 MPa, 53.87 MPa, and 72.41 MPa, respectively, with the strength retention rates of 56.89%, 65.57%, and 86.87%. The MPC–CFRP columns exhibited the best mechanical properties, strength retention, and ductility. Further, the degradation mechanisms of MPC and MPC/EP–CFRP concretes under sulfate dry–wet cycles were clarified, offering a reference for enhanced durability and service life of concrete structures in saline soil regions. Full article

This study examines magnesium potassium phosphate cements (MKPCs) modified with industrial wastes for extrusion-based 3D concrete printing, evaluating the rheological properties (workability, setting time), mechanical performance and printability of formulations incorporating secondary materials: Mg dross waste (up to 20 wt.%, replacing MgO), calcined sewage sludge (up to 10 wt.%, replacing KH₂PO₄), alternative fillers such as glass from municipal solid waste glass and from construction and demolition waste and ground blast furnace slag, benchmarked against volcanic ash. The baseline MKPC exhibited initial/final setting times of 34/109 min, good workability and compressive strengths of 29 MPa (1 day)/28 MPa (28 days). Optimal low-waste mixes (e.g., using municipal glass or 20 wt.% Mg dross) shortened the initial setting to 19–25 min (decreasing 24–42%), reduced the slump by 9–18% yet remained printable at laboratory-scale and achieved 1-day strengths >23 MPa/28-day >31 MPa (comparable or superior). Glass from municipal waste proved most promising, due to superior workability, lighter aesthetics and strength gains, supporting circular economy goals while substantially reducing material costs; higher waste levels compromised fluidity and buildability. Mineralogical analyses confirmed K-struvite formation alongside residual periclase, validating these formulations for upscaling sustainable 3D printing. Full article

This study investigated the effects of calcium (Ca²⁺) and iron (II) Fe²⁺ concentrations (0–500 mg/L) on the heterogeneous nucleation and crystallization behavior of struvite (MgNH₄PO₄·6H₂O) through controlled batch precipitation experiments. Struvite formed under different Ca²⁺ and Fe²⁺ concentrations were systematically characterized using XRD, SEM, FTIR, and XPS, while real-time pH and redox potential (Eh) monitoring was employed to elucidate reaction dynamics and thermodynamic speciation and saturation indices were calculated, and classical nucleation theory (CNT) was applied to interpret nucleation behavior. The results show that Ca²⁺ primarily suppresses struvite formation through bulk-phase competition with Mg²⁺ for phosphate, diverting phosphate into Ca–P phases and progressively reducing struvite supersaturation, which leads to decreased crystallinity and distorted Crystal habit. In contrast, Fe²⁺ does not form detectable crystalline Fe-P phases but inhibits struvite crystallization mainly through surface-mediated processes. Surface analyses indicate that Fe-bearing species adsorb onto struvite surfaces and promote amorphous Fe-P deposition, increasing interfacial resistance to nucleation and growth. CNT analysis further reveals that Ca²⁺ inhibition is governed by reduced thermodynamic driving force, whereas Fe²⁺ inhibition is dominated by surface-related kinetic barriers. This study provides mechanistic insight into ion-specific interference during struvite crystallization and offers guidance for optimizing phosphorus recovery in ion-rich wastewater systems. Full article

Phosphorus recovery from wastewater as struvite via electrochemical magnesium dosing is a promising approach to address the growing demand for fertilizers. However, its large-scale implementation is often constrained by energy requirements. To overcome this limitation, this study investigates electroless struvite precipitation from cheese whey wastewater using sacrificial magnesium anodes. Under optimal conditions, up to 90% of the phosphorus was recovered within 4–6 h. In this process, spontaneous magnesium dissolution acts as the driving force for phosphorus precipitation and is strongly influenced by the wastewater’s ionic composition. To identify conditions that favor efficient recovery, the effects of ammonium, chloride, and sulfate ions were evaluated by monitoring phosphorus removal and magnesium corrosion behavior. Sulfate ions enhanced magnesium corrosion more strongly than chloride during the initial stages, likely due to stronger coulombic interactions with Mg²⁺ at the electrode–electrolyte interface, whereas chloride ions were more effective at disrupting the passivation layer that develops over time. Based on these observations, a mechanistic interpretation of ion-specific effects on anodic corrosion is proposed. Solid-phase analyses using multiple characterization techniques confirmed struvite formation, with ammonium sulfate and ammonium chloride systems yielding the highest product purity. Overall, these findings improve the understanding of electroless struvite precipitation and highlight its potential as an energy-efficient approach for nutrient recovery. Full article