Phosphate adsorption on dried alum sludge: Modeling and application to treatment of dairy effluents.

This study evaluates Alum sludge from drinking water treatment plants for the efficient and cost-effective removal of phosphates from aqueous solutions. Extensive characterization and batch experiments have established that optimal phosphate removal was achieved with a sludge dosage of 20 g L-1 (at an initial phosphate concentration of 100 mg L-1), a pH of 5, a temperature of 23 °C, and a stirring speed of 200 rpm. These conditions significantly reduced phosphate levels, ensuring compliance with legal discharge limits. The Langmuir isotherm, pseudo-second-order kinetic and intraparticle diffusion models best described the adsorption process, highlighting the spontaneous and endothermic nature of the phenomenon. The sludge effectively reduced phosphate concentrations to acceptable levels when applied to dairy effluents. This study underscores the potential of Alum sludge as a viable solution for phosphate management in environmental cleanup efforts.

Magnetic field-assisted adsorption of phosphate on biochar loading amorphous Zr-Ce (carbonate) oxide composite.

For metal-based phosphate adsorbents, the dispersity and utilization of surface metal active sites are crucial factors in their adsorption performance and synthesis cost. In this study, a biochar material modified with amorphous Zr-Ce (carbonate) oxides (BZCCO-13) was synthesized for the phosphate uptake, and the adsorption process was enhanced by magnetic field. The beside-magnetic field was shown to have a better influence than under-magnetic field on adsorption, with maximum adsorption capacities (123.67 mg P/g) 1.14-fold greater than that without magnetic field. The beside-magnetic field could also accelerate the adsorption rate, and the time to reach 90% maximum adsorption capacity decreased by 83%. BZCCO-13 has a wide range of application pHs from 5.0 to 10.0, with great selectivity and reusability. The results of XPS and ELNES showed that the "magnetophoresis" of Ce3+ under the magnetic field was the main reason for the enhanced adsorption performance. In addition, increased surface roughness, pore size and oxygen vacancies, enhanced mass transfer by Lorentz force under a magnetic field, all beneficially influenced the adsorption process. The mechanism of phosphate adsorption by BZCCO-13 could be attributed to electrostatic attraction and CO32-dominated ligand exchange. This study not only provided an effective strategy for designing highly effective phosphate adsorbents, but also provides a new light on the application of rare earth metal-based adsorbent in magnetic field.

Efficient phosphate and hydrogen recovery from sludge fermentation liquid by sacrificial iron anode in electro-fermentation system.

Electro-fermentation (EF) has been extensively studied for recovering hydrogen and phosphorus from waste activated sludge (WAS), while was limited for the further application due to the low hydrogen yield and phosphorus recovery efficiency. This study proposed an efficient strategy for hydrogen and vivianite recovery from the simulated sludge fermentation liquid by sacrificial iron anode in EF. The optimum hydrogen productivity and the utilization efficiency of short chain fatty acids (SCFAs) reached 45.2 mmol/g COD and 77.6% at 5 d in pH 8. Phosphate removal efficiency achieved at 90.8% at 2 d and the high crystallinity and weight percentage of vivianite (84.8%) was obtained. The functional microbes, i.e., anaerobic fermentative bacteria, electrochemical active bacteria, homo-acetogens and iron-reducing bacteria were highly enriched and the inherent interaction between the microbial consortia and environmental variables was thoroughly explored. This work may provide a theoretical basis for energy/resource recovery from WAS in the further implementation.

Striking the balance: Unveiling the interplay between photocatalytic efficiency and toxicity of La-incorporated Ag3PO4.

Persistent molecules, such as pesticides, herbicides, and pharmaceuticals, pose significant threats to both the environment and human health. Advancements in developing efficient photocatalysts for degrading these substances can play a fundamental role in remediating contaminated environments, thereby enhancing safety for all forms of life. This study investigates the enhancement of photocatalytic efficiency achieved by incorporating La3+ into Ag3PO4, using the co-precipitation method in an aqueous medium. These materials were utilized in the photocatalytic degradation of Rhodamine B (RhB) and Ciprofloxacin (CIP) under visible light irradiation, with monitoring conducted through high-performance liquid chromatography (HPLC). The synthesized materials exhibited improved stability and photodegradation levels for RhB. Particularly noteworthy was the 2% La3+-incorporated sample (APL2), which achieved a 32.6% mineralization of CIP, nearly three times higher than pure Ag3PO4. Toxicological analysis of the residue from CIP photodegradation using the microalga Raphidocelis subcapitata revealed high toxicity due to the leaching of Ag + ions from the catalyst. This underscores the necessity for cautious wastewater disposal after using the photocatalyst. The toxicity of the APL2 photocatalysts was thoroughly assessed through comprehensive toxicological tests involving embryo development in Danio rerio, revealing its potential to induce death and malformations in zebrafish embryos, even at low concentrations. This emphasizes the importance of meticulous management. Essentially, this study adeptly delineated a thorough toxicological profile intricately intertwined with the photocatalytic efficacy of newly developed catalysts and the resultant waste produced, prompting deliberations on the disposal of degraded materials post-exposure to photocatalysts.

Modeling of phosphate speciation on goethite surface: Effects of humic acid.

Iron (hydr)oxides and humic acid (HA) are important active components in soils and usually coexist in the environment. The effects of HA on the adsorption and subsequent immobilization of phosphate on iron (hydr)oxide surface are of great importance in studies of soil fertility and eutrophication. In this study, two types of goethite with different particle sizes were prepared to investigate the phosphate adsorption behaviors and complexation mechanisms in the absence or presence of HA by combining multiple characterization and modeling studies. The adsorption capacity of micro- (M-Goe) and nano-sized goethite (N-Goe) for phosphate was 2.02 and 2.04 µmol/m2, which decreased by ∼25% and ∼45% in the presence of 100 and 200 mg/L HA, respectively. Moreover, an increase in equilibrium phosphate concentration significantly decreased the adsorption amount of goethite for HA. Charge distribution-multisite surface complexation (CD-MUSIC) and natural organic matter-charge distribution (NOM-CD) modeling identified five phosphate complexes and their corresponding affinity constants (logKP). Among these phosphate complexes, FeOPO2OH, (FeO)2PO2, and (FeO)2POOH species were predominant complexes on the surface of both M-Goe and N-Goe across a wide range of pH and initial phosphate concentrations. The presence of HA had little effect on the coordination mode and logKP of phosphate on goethite surface. These results and the obtained model parameters shed new lights on the interfacial reactivity of phosphate at the goethite-water interface in the presence of HA, and may facilitate further prediction of the environmental fate of phosphate in soils and sediments.

Drug Crystal Precipitation in Biorelevant Bicarbonate Buffer: A Well-Controlled Comparative Study with Phosphate Buffer.

The purpose of the present study was to clarify whether the precipitation profile of a drug in bicarbonate buffer (BCB) may differ from that in phosphate buffer (PPB) by a well-controlled comparative study. The precipitation profiles of structurally diverse poorly soluble drugs in BCB and PPB were evaluated by a pH-shift precipitation test or a solvent-shift precipitation test (seven weak acid drugs (pKa: 4.2 to 7.5), six weak base drugs (pKa: 4.8 to 8.4), one unionizable drug, and one zwitterionic drug). To focus on crystal precipitation processes, each ionizable drug was first completely dissolved in an HCl (pH 3.0) or NaOH (pH 11.0) aqueous solution (450 mL, 50 rpm, 37 °C). A 10-fold concentrated buffer solution (50 mL) was then added to shift the pH value to 6.5 to initiate precipitation (final volume: 500 mL, buffer capacity (ß): 4.4 mM/ΔpH (BCB: 10 mM or PPB: 8 mM), ionic strength (I): 0.14 M (adjusted by NaCl)). The pH, ß, and I values were set to be relevant to the physiology of the small intestine. For an unionizable drug, a solvent-shift method was used (1/100 dilution). To maintain the pH value of BCB, a floating lid was used to avoid the loss of CO2. The floating lid was applied also to PPB to precisely align the experimental conditions between BCB and PPB. The solid form of the precipitants was identified by powder X-ray diffraction and differential scanning microscopy. The precipitation of weak acids (pKa ≤ 5.1) and weak bases (pKa ≥ 7.3) was found to be slower in BCB than in PPB. In contrast, the precipitation profiles in BCB and PPB were similar for less ionizable or nonionizable drugs at pH 6.5. The final pH values of the bulk phase were pH 6.5 ± 0.1 after the precipitation tests in all cases. All precipitates were in their respective free forms. The precipitation of ionizable weak acids and bases was slower in BCB than in PPB. The surface pH of precipitating particles may have differed between BCB and PPB due to the slow hydration process of CO2 specific to BCB. Since BCB is a physiological buffer in the small intestine, it should be considered as an option for precipitation studies of ionizable weak acids and bases.

Sustainable reprocessing of lithium iron phosphate batteries: A recovery approach using liquid-phase method at reduced temperature.

Lithium iron phosphate batteries, known for their durability, safety, and cost-efficiency, have become essential in new energy applications. However, their widespread use has highlighted the urgency of battery recycling. Inadequate management could lead to resource waste and environmental harm. Traditional recycling methods, like hydrometallurgy and pyrometallurgy, are complex and energy-intensive, resulting in high costs. To address these challenges, this study introduces a novel low-temperature liquid-phase method for regenerating lithium iron phosphate positive electrode materials. By using N2H4·H2O as a reducing agent, missing Li+ ions are replenished, and anti-site defects are reduced through annealing. This process restores nearly all missing Li+ ions at 80 °C/6h. After high-temperature sintering at 700 °C/2h, the regenerated LiFePO4 matches commercial LiFePO4 in terms of anti-site defects and exhibits excellent performance with a 97 % capacity retention rate after 100 cycles at 1C. Compared to high-temperature techniques, this low-temperature liquid-phase method is simpler, safer, and more energy-efficient, offering a blueprint for reclaiming discarded LiFePO4 and similar materials.

Ferrioxalate photolysis-assisted green recovery of valuable resources from spent lithium iron phosphate batteries.

Recovering valuable resources from spent cathodes while minimizing secondary waste generation is emerging as an important objective for the future recycling of spent lithium-ion batteries, including lithium iron phosphate (LFP) batteries. This study proposes the use of oxalic acid leaching followed by ferrioxalate photolysis to separate and recover cathode active material elements from spent LFP batteries. The cathode active material can be rapidly dissolved at room temperature using appropriate quantities of oxalic acid and hydrogen peroxide, as determined through thermodynamic calculations. The dissolved ferrioxalate complex ion (Fe(C2O4)33-) is selectively precipitated through subsequent photolysis at room temperature. Depending on the initial concentration, the decomposition ratio can exceed 95 % within 1-4 h. Molecular mechanism analysis reveals that the decomposition of the Fe(C2O4)33- complex ion into water-insoluble FeC2O4·2H2O results in the precipitation of iron and the separation of metal elements. Lithium can be recovered as dihydrogen phosphates through filtration and water evaporation. No additional precipitant is needed and no other side products are generated during the process. Oxalic acid leaching followed by photolysis offers an environmentally friendly and efficient method for metal recovery from spent LFP cathodes. The photochemical process is a promising approach for reducing secondary waste generation in battery recycling.

Composition regulates dissolved organic matter adsorption onto iron (oxy)hydroxides and its competition with phosphate: Implications for organic carbon and phosphorus immobilization in lakes.

Dissolved organic matter (DOM) is a heterogeneous pool of compounds and exhibits diverse adsorption characteristics with or without phosphorous (P) competition. The impacts of these factors on the burial and mobilization of organic carbon and P in aquatic ecosystems remain uncertain. In this study, an algae-derived DOM (ADOM) and a commercially available humic acid (HA) with distinct compositions were assessed for their adsorption behaviors onto iron (oxy)hydroxides (FeOx), both in the absence and presence of phosphate. ADOM contained less aromatics but more protein-like and highly unsaturated structures with oxygen compounds (HUSO) than HA. The adsorption capacity of FeOx was significantly greater for ADOM than for HA. Protein-like and HUSO compounds in ADOM and humic-like compounds and macromolecular aromatics in HA were preferentially adsorbed by FeOx. Moreover, ADOM demonstrated a stronger inhibitory effect on phosphate adsorption than HA. This observation suggests that the substantial release of autochthonous ADOM by algae could elevate internal P loading and pose challenges for the restoration of restore eutrophic lakes. The presence of phosphate suppressed the adsorption of protein-like compounds in ADOM onto FeOx, resulting in an increase in the relative abundance of protein-like compounds and a decrease in the relative abundance of humic-like compounds in post-adsorption ADOM. In contrast, phosphate exhibited no discernible impact on the compositional fractionation of HA. Collectively, our results show the source-composition characters of DOM influence the immobilization of both DOM and P in aquatic ecosystems through adsorption processes. The preferential adsorption of proteinaceous compounds within ADOM and aromatics within HA highlights the potential for the attachment with FeOx to diminish the original source-specific signatures of DOM, thereby contributing to the shared DOM characteristics observed across diverse aquatic environments.

Research progress on the application of magnesium phosphate bone cement in bone defect repair: A review.

BACKGROUND: Bone defects arising from diverse causes, such as traffic accidents, contemporary weapon usage, and bone-related disorders, present significant challenges in clinical treatment. Prolonged treatment cycles for bone defects can result in complications, impacting patients' overall quality of life. Efficient and timely repair of bone defects is thus a critical concern in clinical practice. OBJECTIVE: This study aims to assess the scientific progress and achievements of magnesium phosphate bone cement (MPC) as an artificial bone substitute material. Additionally, the research seeks to explore the future development path and clinical potential of MPC bone cement in addressing challenges associated with bone defects. METHODS: The study comprehensively reviews MPC's performance, encompassing e.g. mechanical properties, biocompatibility, porosity, adhesion and injectability. Various modifiers are also considered to broaden MPC's applications in bone tissue engineering, emphasizing drug-loading performance and antibacterial capabilities, which meet clinical diversification requirements. RESULTS: In comparison to alternatives such as autogenous bone transplantation, allograft, polymethyl methacrylate (PMMA), and calcium phosphate cement (CPC), MPC emerges as a promising solution for bone defects. It addresses limitations associated with these alternatives, such as immunological rejection and long-term harm to patients. MPC can control heat release during the curing process, exhibits superior mechanical strength, and has the capacity to stimulate new bone growth. CONCLUSION: MPC stands out as an artificial bone substitute with appropriate mechanical strength, rapid degradation, non-toxicity, and good biocompatibility, facilitating bone repair and regeneration. Modification agents can enhance its clinical versatility. Future research should delve into its mechanical properties and formulations, expanding clinical applications to create higher-performing and more medically valuable alternatives in bone defect repair.

TMV-CP based rational design and discovery of α-Amide phosphate derivatives as anti plant viral agents.

The tobacco mosaic virus coat protein (TMV-CP) is indispensable for the virus's replication, movement and transmission, as well as for the host plant's immune system to recognize it. It constitutes the outermost layer of the virus particle, and serves as an essential component of the virus structure. TMV-CP is essential for initiating and extending viral assembly, playing a crucial role in the self-assembly process of Tobacco Mosaic Virus (TMV). This research employed TMV-CP as a primary target for virtual screening, from which a library of 43,417 compounds was sourced and SH-05 was chosen as the lead compound. Consequently, a series of α-amide phosphate derivatives were designed and synthesized, exhibiting remarkable anti-TMV efficacy. The synthesized compounds were found to be beneficial in treating TMV, with compound 3g displaying a slightly better curative effect than Ningnanmycin (NNM) (EC50 = 304.54 µg/mL) at an EC50 of 291.9 µg/mL. Additionally, 3g exhibited comparable inactivation activity (EC50 = 63.2 µg/mL) to NNM (EC50 = 67.5 µg/mL) and similar protective activity (EC50 = 228.9 µg/mL) to NNM (EC50 = 219.7 µg/mL). Microscale thermal analysis revealed that the binding of 3g (Kd = 4.5 ± 1.9 µM) to TMV-CP showed the same level with NNM (Kd = 5.5 ± 2.6 µM). Results from transmission electron microscopy indicated that 3g could disrupt the structure of TMV virus particles. The toxicity prediction indicated that 3g was low toxicity. Molecular docking showed that 3g interacted with TMV-CP through hydrogen bond, attractive charge interaction and π-Cation interaction. This research provided a novel α-amide phosphate structure target TMV-CP, which may help the discovery of new anti-TMV agents in the future.

Utilization and value-adding of waste: Fabrication of porous material from chitosan for phosphate capture and energy storage.

Efficient removal and recycling of phosphorus from complex water matrices using environmentally friendly and sustainable materials is essential yet challenging. To this end, a novel bio-based adsorbent (DX-FcA-CS) was developed by coupling oxidized dextran-crosslinked chitosan with ferrocene carboxylic acid (FcA). Detailed characterization revealed that the incorporation of FcA reduced the total pore area of DX-FcA-CS to 7.21 m2·g-1, one-third of ferrocene-free DX-CS (21.71 m2·g-1), while enhancing thermal stability and PO43- adsorption performance. Adsorption kinetics and isotherm studies demonstrated that the interaction between DX-FcA-CS and PO43- followed a pseudo-second-order kinetic model and Langmuir model, indicating chemical and monolayered adsorption mechanisms, respectively. Moreover, DX-FcA-CS exhibited excellent anti-interference properties against concentrated co-existing inorganic ions and humic acid, along with high recyclability. The maximum adsorption capacity reached 1285.35 mg·g-1 (∼428.45 mg P g-1), three times that of DX-CS and surpassing many other adsorbents. PO43--loaded DX-FcA-CS could be further carbonized into electrode material due to its rich content of phosphorus and nitrogen, transforming waste into a valuable resource. These outstanding characteristics position DX-FcA-CS as a promising alternative for phosphate capture and recycling. Overall, this study presents a viable approach to designing environmentally friendly, recyclable, and cost-effective biomaterial for wastewater phosphate removal and value-added applications.

Polyetheretherketone bioactivity induced by farringtonite.

Polyetheretherketone (PEEK) is considered as an excellent biomaterial for bone grafting and connective tissue replacement. The clinical potential is, however, limited by its bioinertness, poor osteoconduction, and weak antibacterial activity. These disadvantages can be overcome by introducing suitable additives to produce mineral-polymer composites or coatings. In this work, a PEEK-based bioactive composite has been obtained by blending the polymer with magnesium phosphate (Mg3(PO4)2) particles in amounts ranging from 1 to 10 wt.% using the hot press technique. The obtained composite exhibited improved mechanical and physical properties, above the lower limits set for bone engineering applications. The tested grafts were found to not induce cytotoxicity. The presence of magnesium phosphate induced the mineralisation process with no adverse effects on the expression of the marker crucial for osteoblastic differentiation. The most promising results were observed in the grafts containing 1 wt.% of magnesium phosphate embedded within the PEEK matrix. The improved bioactivity of grafts, together with suitable physical-chemical and mechanical properties, indicate this composite as a promising orthopaedic implant material.

An eco-friendly porous hydrogel adsorbent based on dextran/phosphate/amino for efficient removal of Be(II) from aqueous solution.

A novel environmentally-friendly porous hydrogel adsorbent (GHPN) is firstly designed and prepared using dextran, phosphate, and calcium hydroxide for the adsorption of Be(II). GHPN shows good adsorption selectivity for Be(II) (Kd = 1.53 × 104 mL/g). According the adsorption kinetics and thermodynamics, the theoretical adsorption capacity of GHPN to Be(II) is 43.75 mg/g (35 °C, pH = 6.5), indicating a spontaneous exothermic reaction. After being reused for 5 cycles, the adsorption and desorption efficiencies of Be(II) with GHPN are obtained to be more than 80 %, showing acceptable recycling performance. Both of the characterizations and theoretical calculations indicate that the phosphate group, hydroxyl group, and amino group own the affinity to form stable complexes with Be(II). Benefiting from the introduction of phosphate and amino, the adsorption effect of the hydrogel adsorbent on Be(II) can be greatly improved, and surface precipitation, complexation, and ligand exchange are the dominant mechanisms of beryllium adsorption. The results suggest that GHPN has great potential to be utilized as an eco-friendly and useful adsorbent of Be(II) from aqueous solution.

Solubility vs Dissolution in Physiological Bicarbonate Buffer.

BACKGROUND: Phosphate buffer is often used as a replacement for the physiological bicarbonate buffer in pharmaceutical dissolution testing, although there are some discrepancies in their properties making it complicated to extrapolate dissolution results in phosphate to the in vivo situation. This study aims to characterize these discrepancies regarding solubility and dissolution behavior of ionizable compounds. METHODS: The dissolution of an ibuprofen powder with a known particle size distribution was simulated in silico and verified experimentally in vitro at two different doses and in two different buffers (5 mM pH 6.8 bicarbonate and phosphate). RESULTS: The results showed that there is a solubility vs. dissolution mismatch in the two buffers. This was accurately predicted by the in-house simulations based on the reversible non-equilibrium (RNE) and the Mooney models. CONCLUSIONS: The results can be explained by the existence of a relatively large gap between the initial surface pH of the drug and the bulk pH at saturation in bicarbonate but not in phosphate, which is caused by not all the interfacial reactions reaching equilibrium in bicarbonate prior to bulk saturation. This means that slurry pH measurements, while providing surface pH estimates for buffers like phosphate, are poor indicators of surface pH in the intestinal bicarbonate buffer. In addition, it showcases the importance of accounting for the H2CO3-CO2 interconversion kinetics to achieve good predictions of intestinal drug dissolution.

Adsorption Potential, Speciation Transformation, and Risk Assessment of Hg-, Cd-, and Pb-Contaminated Soils Using Biochar in Combination with Potassium Dihydrogen Phosphate.

The objective of this study is to develop a remediation technology for composited heavy metal-contaminated soil. Biochars (BC300, BC400, and BC500) derived from corn were combined with potassium dihydrogen phosphate (KH2PO4) to immobilize and remove heavy metal ions, including mercury (Hg2+), cadmium (Cd2+), and lead (Pb2+). The adsorption kinetics of metal ions in aqueous solutions with different concentrations was tested, and the fitting effects of the two models were compared. The findings demonstrate that the joint application of biochar and KH2PO4 could markedly enhance the immobilization efficacy of Pb2+, whereas the utilization of KH2PO4 on its own exhibited a more pronounced immobilization impact on Cd2+. Furthermore, the present study underscores the shortcomings of various remediation techniques that must be taken into account when addressing heavy metal-contaminated soils. It also emphasizes the value of comprehensive remediation techniques that integrate multiple remediation agents. This study offers a novel approach and methodology for addressing the intricate and evolving challenges posed by heavy metal contamination in soil. Its practical value and potential for application are significant.

Recycled Iron Phosphates: A New Phosphorus Fertilizer for Paddy Rice.

The potential of recycled iron phosphates (FePs), e.g., vivianites (Fe3(PO4)2·8H2O) and Fe(III)-rich phosphorus (P) adsorbent materials, as phosphorus fertilizer is limited by the strong interaction between Fe and P. In this study, the efficiency of FePs as P fertilizer was explored by applying them as granules or powder in flooded strongly P-fixing soils (acid and calcareous), thereby taking advantage of increased P release induced by reductive dissolution of P-bearing Fe(III) minerals. First, no P diffusion from granular FeP fertilizers into flooded soils was detectable by the diffusive gradient in thin films (DGT) technique and microfocused X-ray fluorescence (µ-XRF) analysis of thin soil sections, in contrast to detectable P diffusion away from granules of soluble triple superphosphate (TSP) fertilizer. On the contrary, powdered FePs demonstrated an excellent increase in extractable P (1 mM CaCl2) in a 120-day incubation experiment in flooded soils. Second, a pot experiment was performed with rice (Oryza sativa) grown in flooded acid and calcareous soils. The fertilizer value of FePs was remarkable when dosed as powder, as it was even up to 3-fold higher than TSP in the acid soil and similar to TSP in the calcareous soil. The beneficial effect of FeP over TSP in the acid soil is attributed to the slow release of P from FePs, which allows to partly overcome P fixation. The promising results of FePs as P fertilizer applied as powders in flooded soils debunk the generally accepted idea that FePs are poor sources of P while demonstrating the importance of the timing of FeP fertilizer application.

Concomitant urea stabilization and phosphorus recovery from source-separated fresh urine in magnesium anode-based peroxide-producing electrochemical cells.

In this study, we investigated the recovery of nitrogen (N) and phosphorus (P) from fresh source-separated urine with a novel electrochemical cell equipped with a magnesium (Mg) anode and carbon-based gas-diffusion cathode. Recovery of P, which exists primarily as phosphate (PO43-) in urine, was achieved through pH-driven precipitation. Maximizing N recovery requires simultaneous approaches to address urea and ammonia (NH3). NH3 recovery was possible through precipitation in struvite with soluble Mg supplied by the anode. Urea was stabilized with electrochemically synthesized hydrogen peroxide (H2O2) from the cathode. H2O2 concentrations and resulting urine pH were directly proportional to the applied current density. Concomitant NH3 and PO43- precipitation as struvite and urea stabilization via H2O2 electrosynthesis was possible at lower current densities, resulting in urine pH under 9.2. Higher current densities resulted in urine pH over 9.2, yielding higher H2O2 concentrations and more consistent stabilization of urea at the expense of NH3 recovery as struvite; PO43- precipitation still occurred but in the form of calcium phosphate and magnesium phosphate solids.

Novel Ag3PO4/ZnWO4-modified graphite felt electrode for photoelectrocatalytic removal of harmful algae: Performance and mechanism.

A novel Ag3PO4/ZnWO4-modified graphite felt electrode (AZW@GF) was prepared by drop coating method and applied to photoelectrocatalytic removal of harmful algae. Results showed that approximately 99.21% of chlorophyll a and 91.57% of Microcystin-LR (MCLR) were degraded by the AZW@GF-Pt photoelectrocatalytic system under the optimal operating conditions with a rate constant of 0.02617 min-1 and 0.01416 min-1, respectively. The calculated synergistic coefficient of photoelectrocatalytic algal removal and MC-LR degradation by the AZW@GF-Pt system was both larger than 1.9. In addition, the experiments of quenching experiments and electron spin resonance (ESR) revealed that the photoelectrocatalytic reaction mainly generated •OH and •O2- for algal removal and MC-LR degradation. Furthermore, the potential pathway for photoelectrocatalytic degradation of MC-LR was proposed. Finally, the photoelectrocatalytic cycle algae removal experiments were carried out on AZW@GF electrode, which was found to maintain the algae removal efficiency at about 91% after three cycles of use, indicating that the photoelectrocatalysis of AZW@GF electrode is an effective emergency algae removal technology.

Photoluminescence properties of Pb5(PO4)3Br:RE (RE = Dy3+, Eu3+ and Tb3+) phosphor synthesised using solid-state method.

This study describes the luminous properties of Pb5(PO4)3Br doped with RE3+ (RE = Dy3+, Eu3+ and Tb3+) synthesised using the solid-state method. The synthesised phosphor was characterised using Fourier-transform infrared, X-ray diffraction, scanning electron microscopy and photoluminescence measurements. Dy3+-doped Pb5(PO4)3Br phosphor exhibited blue and yellow emissions at 480 and 573 nm, respectively, on excitation at 388 nm. Eu3+-doped Pb5(PO4)3Br phosphor exhibited orange and red emissions at 591 and 614 nm, respectively, on excitation at λex = 396 nm. Pb5(PO4)3Br:Tb3+ phosphor exhibited the strongest green emission at 547 nm on excitation at λex = 380 nm. Additionally, the effect of the concentration of rare-earth ions on the emission intensity of Pb5(PO4)3Br:RE3+ (RE3+ = Dy3+, Eu3+ and Tb3+) phosphors was investigated.