Phosphate Elimination Research Articles

Efficient Capture of Phosphate From Aqueous Media Using Bimetallic La‐Zr‐MOF

ABSTRACTDeposition of excessive phosphate in natural water column caused several issues, like the eutrophication and destruction of aquatic ecosystems. Adsorption has been an effective and convenient method for phosphate elimination. Herein, a novel bimetallic metal–organic framework adsorbent, namely, La‐Zr‐MOF, was prepared, and the morphology, crystallite, characteristic functional groups, specific surface area, and composite material surfaces were analyzed using XRD, FT‐IR, SEM‐EDS, and BET. The adsorption performance of the adsorbent was systematically evaluated by batch adsorption experiments, and the adsorption thermodynamic and kinetic properties were analyzed. The results reveal that La‐Zr‐MOF exhibits a high selectivity and sorption performance for phosphate, and the adsorption of La‐Zr‐MOF follows the Langmuir and pseudo–second‐order models; the phosphate removal procedure is a chemisorption accompanied by an endothermic reaction, and the maximum capacity was 127.7 mg g−1. Combined with batch adsorption experiments, kinetic and thermodynamic studies and various characterization analyses together revealed the phosphate removal mechanism, mainly ligand exchange and electrostatic interactions.

The amputation of phosphate anions by cobalt oxide nanoparticles doped functionalized nanocomposites from wastewater

As a novel adsorbent to removal phosphate from water, Co3O4 magnetic nanoparticles functionalized with zeolite-A-@silica nanocomposites were created. The produced adsorbent was evaluated for phosphate removal efficiency using batch adsorption tests, as well as X-ray diffractometry (XRD), scanning electron microscopy (SEM), EDX, BET, and FT-IR. The synthesized adsorbent with a BET (Brunauer–Emmett–Teller(BET) surface area of 8.367 m2/g, porous zeolite-A, was successfully constructed with Co3O4 and nanosilica, according to characterization results. The newly created adsorbent performed incredibly well at adsorbing phosphate; according to the Langmuir model, it had a maximum adsorption capacity of 344.83 mg/g. The adsorption occurred quickly, and the pseudo-first-order kinetic model provided the greatest fit for the kinetic data. As the pH of the solution increased (2 to 10), the elimination of phosphate reduced. The experimental results indicated negative ΔG, negative ΔH, and positive S, suggesting the exothermic and spontaneous process of PO4-3 adsorption on synthesized adsorbents.

Endowing turbostratically porous carbon with rich edge nitrogen active sites for efficient capacitive removal of phosphate

The mitigation of phosphate in water is a pivotal concern for the prevention of eutrophication and enhancement of water quality. Capacitance deionization (CDI) technique possesses the merits of high removal efficacy, facile operation, and environmental friendliness, rendering it a promising strategy for phosphate elimination. Herein, the nitrogen-rich laminar porous carbon composites (NTPCs) prepared by direct pyrolysis of supermolecular precursor were utilized as phosphate capture electrodes. The resulting NTPC800 features a high nitrogen content turbostratically amorphous carbon framework, which facilitates efficient ion diffusion pathways and electron transfer. The abundant presence of edge nitrogen (pyridine and pyrrole nitrogen) optimizes the electronic structure of the carbon system and provides more active sites, thus leading to the boosted electrochemical activity and dephosphorization efficiency. Consequently, NTPC800 demonstrates a rapid phosphate removal capacity, achieving 73.51 mg g−1 within a mere 10 min at 1.2 V condition, which is nearly 6 times more efficient than that of the commercial activated carbon electrode. Moreover, it exhibited consistent phosphate removal efficiency across various pH ranges, coexisting ion interferences, and cyclic stability assessments. This study provides theoretical support for the utilization of edge nitrogen decorated carbonaceous electrodes to enhance charge transfer and provide additional active sites for efficient capacitive dephosphorization.

Restricted reaction of layered double hydroxide nanoparticles with phosphate in a confined microsphere space

Over the past decades, considerable efforts have been made to find useful solutions for phosphate pollution control. The state transition of nanomaterials from freely dispersed to encapsulated provides a realizable route for their application in phosphate elimination. The separation convenience offered by encapsulation has been widely recognized, however, the unique binding mode of nanostructures and phosphate in the confined space remains unclear, limiting its further development. Here, carboxymethyl cellulose (CMC) microspheres were used as hosts to deploy layered double hydroxide (LDH) nanoparticles. On this basis, we described an attempt to explore the adsorption behavior of LDH and phosphate in the microsphere space. Compared to their freely dispersed analogues, LDH particles exhibited higher structural stability, wider pH adaptability, and better phosphate selectivity when spatially confined in the CMC microsphere. Nevertheless, the kinetic process was severely inhibited by three orders of magnitude. Besides, the saturated phosphate adsorption capacity was also reduced to 74.6 % of the freely dispersed system. A combinative characterization revealed that the highly electronegative CMC host not only causes electrostatic repulsion to phosphate, but also extracts the electron density of the metal center of LDH, weakening its ability to act as a Lewis acid site for phosphate binding. Meanwhile, the microsphere encapsulation also hinders the ion exchange function of interlayer anions and phosphate. This study offers an objective insight into the reaction of LDH and phosphate in the confined microsphere space, which may contribute to the advanced design of encapsulation strategies for nanoparticles.

Nutritional content and growth ability of aquatic plant Azolla pinnata on wastewater of catfish

Azolla pinnata is a floating aquatic plant with several benefits as a source of feed in aquaculture and animal as well as a phytoremediator. Research with two replications was carried out at RC for Limnology and Water Resources laboratory on May 2022 to explore information on its nutritional content, growth ability and function as a phytoremediator. The growth ability research was carried out in-door using media of catfish cultivation wastewater varied in concentration (100%, 60%, and 30%), and the observation period of 3 days for 15 days. Azolla pinnata contains nutrition (% dry weight): ash: 31.20; fat: 12.37; protein: 27.16; fibre: 11.15; and Nitrogen Free Extract: 18.12, respectively. There were 15 types of amino acids, as much as 1.59 % w/w. On the 15th day, the highest growth was seen in the media with 100% concentration, where the culture density was 310.47 g/m2, specific growth rate (SGR) was 15.38%, and productivity was 35.93 g/m2/day. At the same media, Total Phosphate (TP) elimination rates were 46.06%, and Total Nitrogen (TN) was 79.474%. Azolla pinnata can be cultivated in catfish wastewater to provide nutritious feed as well as to reduce the content of TP and TN.

Mechanistic Investigations into the Catalytic Mode of a Dehydratase Complex Involved in the Biosynthesis of Lantibiotic Cacaoidin

Comprehensive SummaryDehydration of serine/threonine residues necessitates the activity of a dehydratase enzyme (domain) during the biosynthesis of RiPP. Recently, it was reported that dehydration in the thioviridamide pathway relies on a distinct dehydratase complex that showcases the activities of a phosphotransferase TvaC for serine/threonine phosphorylation and a lyase TvaD for subsequent phosphate elimination. Herein, we report that dehydration reactions in the pathway of lantibiotic cacaoidin involves a similar dehydratase complex, CaoK/CaoY. Remarkably, this dehydratase complex exhibits flexible enzymatic activity and tolerates significant variations in its substrate peptide sequence. By binding with the leader peptide (LP) sequence of precursor peptide CaoA, the dehydration reactions proceed in a directional manner from the C‐terminus of the core peptide (CP) to the N‐terminus, and C‐terminally truncated variants of CP are acceptable. We show that fusing CaoK to CaoY in a 1 : 1 molar ratio enables the resulting enzyme CaoYK to exert enhanced dehydration activity. CaoK binds with the LP to improve its own solubility and to ensure the phosphate transfer activity, while CaoY functions in a manner independently of LP. This work advances our understanding of the dehydration process during cacaoidin formation, and provides useful enzymes and methods for the studies of the rapidly emerging RiPPs.

Application and functionalization of toxic waste sludge-derived biochar for efficient phosphate separation from aqueous media: Toxicity diminution, robust adsorption, and inner mechanism

Phosphorus control and the disposal of municipal solid waste have drawn increasing concerns. Herein, we reported the reutilization and functionalization of highly toxic waste sludge derived from landfill leachate treatment process for biochar preparation and therefore phosphate elimination from aqueous media. Toxicity analysis confirmed largely declined heavy metal leaching and diminished ecological risks during biochar pyrolysis, providing a feasible option for the disposal and reutilization of toxic waste. Pre-loading of lanthanum rendered fabricated biochar with robust phosphate adsorption capacity, with optimized composite achieving maximum capacity of ∼94.4 mg P/g at pH 6. Effects of environmental factors, especially co-existing species (anions, cations and dissolved organic matters), were systematically evaluated combining experimental results and characterization analysis. Thereafter, adsorption behaviors of synthesized samples including kinetic, isotherm and thermodynamics were comprehensively explored. In virtue of characterization analysis, physicochemical properties of different composites and phosphate separation mechanism that involved electrostatic attraction and inner-sphere complexation were fully probed. Overall work investigated the feasibility of toxicity reduction via pyrolysis, phosphate uptake performance and inner mechanism, therefore highlighting the potential of waste reutilization for environmental remediation.

Reuse of phosphogypsum and phosphorus ore flotation tailings as adsorbent: The adsorption performance and mechanism of phosphate

Phosphogypsum (PG) and phosphorus ore flotation tailings (POFT) are generated in the phosphorus chemical industry, where stockpiling PG and POFT causes serious pollution to the environment. In this study, a novel adsorbent material (i.e., PGTA) was prepared in proportion to PG, POFT and starch to remove phosphate from the aqueous solution. Batch experiments were conducted to investigate the adsorption performance of PGTA for phosphate. The effects of various factors such as initial pH and coexisting anions on the phosphate adsorption were investigated as well as the properties of the PGTA adsorbent. The results showed that the optimum initial pH for phosphate adsorption was 5.15 and amount of PGTA was 1.5 g/L. The pseudo-second-order kinetic model fitted well with the adsorption process of the phosphate while the maximum adsorption capacity of phosphate was 31.28 mg/g as stimulated in the Langmuir model. In conclusion, the PGTA adsorbent could be used for effective phosphate elimination, which positively contributes to the sustainable disposal of PG and POFT.

Sustainable lanthanum-attapulgite/alginate hydrogels with enhanced mechanical strength for selective phosphate scavenging

Attapulgite has rarely been used in lanthanum-based alginate hydrogel development for phosphate elimination. The associated research gaps regarding green fabrication, eco-friendly application, and mechanical strength improvement are worthy of systematic investigation. Herein, a newly designed lanthanum-crosslinked attapulgite/sodium alginate (La-ATP/SA) hydrogel adsorbent was prepared by an eco-friendly facile cross-linking method. The results showed that the introduction of attapulgite into sodium alginate enhanced the mechanical strength of La-ATP/SA beads. SEM images, TG tests, and stability assessment tests further verified the reinforced structure. Batch experiments demonstrated that the adsorption information was better described by the Freundlich isotherm equation and the pseudo-second-order kinetic model, harvesting more than 50% phosphate removal of the total amount within 120 min, proving that chemical adsorption dominated the sorption process. The maximum phosphate sorption capacity was 24.57 mg/g and stable phosphate removal was obtained in the presence of the commonly existing anions. The adsorption behavior was pH-dependent and efficient phosphate uptake was maintained over a wide pH range (3–9). The dominant mechanism for phosphate removal of La-ATP/SA was the inner-sphere complex mechanism. Small spherical macromolecular hydrogels can be easily recollected and display good reusability after five cycles. The results of this study demonstrate that the La-ATP/SA hydrogel is a promising sustainable candidate for phosphate control.

Efficient phosphate elimination from aqueous media by La/Fe bimetallic modified bentonite: Adsorption behavior and inner mechanism

Nowadays, eutrophication problem in surface waterbodies has attracted specific attention. Herein, we reported facile synthesis and application of La/Fe engineered bentonite (LFB) for efficient phosphate elimination. Results indicated that bimetallic modified LFB composite could achieve efficient phosphate removal at pH 2–6, and satisfactory selectivity was implied by stable phosphate capturing within the interference of competing species (Cl−, NO3−, HCO3−, SO42−, F− and HA). Pseudo-second-order model could satisfactorily depict the kinetic behavior at different initial concentrations, indicating chemisorption of phosphate on LFB surface. Isotherm study suggested that phosphate adsorption behavior could be fitted well with Sips isotherm equation, indicating that both homogeneous monolayer adsorption and heterogeneous multilayer coverage of phosphate on LFB surface occurred within the investigated conditions. Adsorption thermodynamics implied the spontaneous and endothermic feature of phosphate loading on LFB composite. Characterization analysis confirmed successful La and Fe loading on bentonite, and electrostatic attraction and ligand exchange were the main adsorption mechanism. The high adsorption capacity, cost-effective feature and strong affinity towards phosphate demonstrated certain potential of as-prepared LFB composite for phosphate separation from eutrophic water.

Removal of phosphate from synthetic wastewater: A comparative study between both activated clays using an experimental design methodology.

Phosphate-loaded industrial wastewaters have resulted in numerous environmental issues that have hard hit the Gulf of Gabes-Tunisia, making the environmental protection one of the most compelling priorities. Consequently, this study aimed first to compare the amounts of phosphate adsorbed by two types of Tunisian activated clays. The second goal was to assess and optimize the phosphate removal efficiency of these clays, using Box-Behnken design (BBD) under response surface methodology. Results showed that the highest adsorption amounts of 130.16 mg g-1 , 125.42 mg g-1 were yielded for Jebel Haidoudi clay and Douiret clay, respectively. These values demanded an initial phosphate concentration of 300 mg L-1 , a contact time of 5h, and a pH of 2). Thus, kinetic and isotherm studies of phosphate elimination from synthetic solutions demonstrated that for both activated clays, the pseudo-second-order and Langmuir equation fitted very well the experimental data, respectively. These results indicate that phosphate adsorption might be mainly a chimisorption phenomenon and a monolayer process. All these findings confirmed that both activated clays could be considered as a competent, cost-effective, efficient and ecological alternative for the elimination of phosphate from industrial wastewaters. PRACTITIONER POINTS: Activated clay could be adopted as an efficient and cost-effective adsorbent. The optimum conditions were nominated as 300 mg L-1 of initial phosphate concentration, 5 h contact times and pH=2. The probable uptake mechanism of phosphate followed predominantly the acid-base interaction and hydrogen bond.

La(III) loaded Fe(III) cross–linked chitosan composites for efficient removal of phosphate from wastewater: Performance and mechanisms

The cost–effective removal and recovery of phosphate from wastewater is of great importance to controlling eutrophication and alleviating the phosphorus resource exhaustion crisis. Herein, chitosan (Cs) encapsulated bimetallic lanthanum (La) and iron (Fe) metal(hydro) oxides (La/Fe–Cs) composites were fabricated using a co–precipitated method for enhanced phosphate removal and recovery. The La/Fe–Cs composites had rough and raised spongy–like surfaces coated with La/Fe (hydr)oxide particles with a high specific surface area of 109.84 m2 g−1, providing more potential binding sites for phosphate capture. The La/Fe–Cs composites with a 1:2 La–to–Fe molar ratio exhibited a maximum adsorption capacity of 67.52 mg g−1 for phosphate at 308 K, calculated using the Langmuir model, which was 211% higher than that of monometallic Fe–Cs composites. Meanwhile, this composite also showed a high phosphate removal rate (63–95%) in an extensive applicable pH range (3.00–10.00) and rapid adsorption within 10 min (up to 94%). Moreover, the adsorption of phosphate by La/Fe–Cs composites was mildly disturbed against co–existing ions of NO3−, Cl−, and humic acid, while adsorption capacities were reduced by almost 13–45% with the existence of SO42−, HCO3−, and CO32−. The FTIR, XPS, and DFT results suggested that La–doped facilitated phosphate removal and the predominant mechanisms involved electrostatic interaction, surface precipitation, and inner–sphere complexation processes. Additionally, La/Fe–Cs composites also illustrated excellent efficiencies in simultaneous scavenging phosphate and ammonia from eutrophication and poultry wastewater. These results highlight bimetallic La/Fe–Cs composites are promising candidates for efficient elimination and recovery of phosphate from real wastewater, and subsequently could be used as slow–release fertilizers or soil amendments.

Role of trace TEMPO as electron shuttle in enhancing chloroquine phosphate elimination in UV-LED-driven persulfate activation process

Chloroquine Phosphate (CP) is an antiviral drug used for treatment of COVID-19. It is released into wastewater and eventually contaminates natural water. This study reports an effective homogeneous catalysis way for CP degradation by the 2,2,6,6-Tetramethylpiperidine-N-oxyl (TEMPO) enhanced persulfate (PDS) activation under UVB-LEDs irradiation at 305 nm. TEMPO at a low concentration (0.1 μM) enhanced CP degradation in UV305/PDS process in deionized water at different pHs, in different anions and different molecular weight dissolved organic matter solutions and in real surface water. The enhancement was verified to be attributed to the electron shuttle role of TEMPO, which promoted the yield of SO4•– by enhancing electron donating capacity of the reacting system. The degradation products of CP and their acute toxicities suggested that UV305/PDS/TEMPO process has better performance on CP detoxification than UV305/PDS process. This study provides a new way to tackle the challenge of pharmaceutical pollutions in homogeneous photocatalysis process for natural water and sewage restoration.

Mechanistic Studies on Dehydration in Class V Lanthipeptides.

Lanthipeptides are ribosomally synthesized and post-translationally modified peptides characterized by lanthionine (Lan) and/or methyllanthionine (MeLan) residues. Four classes of enzymes have been identified to install these structures in a substrate peptide. Recently, a novel class of lanthipeptides was discovered that lack genes for known class I–IV lanthionine synthases in their biosynthetic gene cluster (BGC). In this study, the dehydration of Ser/Thr during the biosynthesis of the class V lanthipeptide cacaoidin was reconstituted in vitro. The aminoglycoside phosphotransferase-like enzyme CaoK iteratively phosphorylates Ser/Thr residues on the precursor peptide CaoA, followed by phosphate elimination catalyzed by the HopA1 effector-like protein CaoY to achieve eight successive dehydrations. CaoY shows sequence similarity to the OspF family proteins and the lyase domains of class III/IV lanthionine synthetases, and mutagenesis studies identified residues that are critical for catalysis. An AlphaFold prediction of the structure of the dehydration enzyme complex engaged with its substrate suggests the importance of hydrophobic interactions between the CaoA leader peptide and CaoK in enzyme–substrate recognition. This model is supported by site-directed mutagenesis studies.

The pathway for coenzyme M biosynthesis in bacteria

Mercaptoethane sulfonate or coenzyme M (CoM) is the smallest known organic cofactor and is most commonly associated with the methane-forming step in all methanogenic archaea but is also associated with the anaerobic oxidation of methane to CO2 in anaerobic methanotrophic archaea and the oxidation of short-chain alkanes in Syntrophoarchaeum species. It has also been found in a small number of bacteria capable of the metabolism of small organics. Although many of the steps for CoM biosynthesis in methanogenic archaea have been elucidated, a complete pathway for the biosynthesis of CoM in archaea or bacteria has not been reported. Here, we present the complete CoM biosynthesis pathway in bacteria, revealing distinct chemical steps relative to CoM biosynthesis in methanogenic archaea. The existence of different pathways represents a profound instance of convergent evolution. The five-step pathway involves the addition of sulfite, the elimination of phosphate, decarboxylation, thiolation, and the reduction to affect the sequential conversion of phosphoenolpyruvate to CoM. The salient features of the pathway demonstrate reactivities for members of large aspartase/fumarase and pyridoxal 5'-phosphate-dependent enzyme families.

Remarkable phosphate electrosorption/desorption by bimetallic MOF-derived hierarchically porous carbon electrode: In-situ creation of multiple active centers and boosting electrochemical activities

Elimination of phosphate is essential to control eutrophication and improve water quality. Nevertheless, the removal capacity of dephosphorization agents in conventional methods is far from satisfactory. Herein, we proposed an electro-assisted adsorption method and fabricated a novel bimetallic Zr-Al metal organic framework (MOF) derived hierarchically porous carbon (ZAMC-13) electrode for efficient phosphate electrosorption. The results of systematic experimental indicated that the synergistic contribution of Zr and Al can boost the electrochemical activities and oxygen vacancies, thus resulting in an increased reaction rate and removal capacity. The ZAMC-13 electrode, as expected, demonstrated a remarkable phosphate electrosorption capacity of 539.85 mg/g at 1 V, with an exceptional regeneration performance of 90.59% after 20 consecutive cycles using a reverse voltage. The electrosorption behavior was further revealed using kinetic and isotherm models. Besides, the phosphate electrosorption mechanisms, which were primarily dominated by ligand exchange, electrostatic attraction, oxygen vacancies consumption, and electric field, were elucidated. Furthermore, the energy consumption and operating cost for electro-assisted phosphate removal are as low as 0.0108 kWh/kg P and 0.020 $/m3, respectively. This work demonstrates a deep understanding and promotes a new level of electro-assisted phosphate adsorption.

Development and application of lanthanum peroxide loaded sepiolite nanocomposites for simultaneous removal of phosphate and inhibition of cyanobacteria growth

The ecological and environmental problem caused by harmful algal blooms (HABs) is challenging to humans. The simultaneous elimination of cyanobacteria and phosphate from eutrophic waters is of great importance. Herein, a new lanthanum peroxide-loaded sepiolite nanocomposite was fabricated via a facile in-situ co-precipitation method and demonstrated the excellent properties on removal of phosphate and inhibition of cyanobacteria growth. The optimized nanocomposite (termed as LPS30) prepared with a La-to-Sepiolite mass ratio of 0.3:1 demonstrated the best cyanobacteria removal with an effective duration of at least 3 months, due to the even dispersion of high-content LP nanoparticles in the sepiolite. LPS30 exhibited a high phosphate uptake (52.68 mg-P/g), fast uptake kinetics (∼45 min to reach 80% of ultimate uptake), and relatively higher selectivity in the presence of competing matters. The pH-dependent phosphate sorption resulted from the ligand exchange between phosphate and surface functional groups (e.g., peroxo and hydroxyls), and the electrostatic attraction. The efficient and long-lasting inhibition for cyanobacteria regrowth was attributed to the combined effect of the oxidative species (i.e., LaOO-) and the efficient removal of phosphate through the coagulation flocs. Our study demonstrated that LPS30 is a promising material to simultaneously treat phosphate and algae for HABs management.

Rice straw derived adsorbent for fast and efficient phosphate elimination from aqueous solution

Rice straw (RS) is an abundant agricultural residue with plentiful hydroxyl groups. In this study, a low-cost and effective RS-based phosphate adsorbent (RS-PA) was prepared through a three-step reaction process, successively with epichlorohydrin (ECH), ethylenediamine (EDA), and triethylamine (TEA). The elimination process of phosphate was optimized by considering altered adsorption conditions. The successful production of RS-PA was confirmed by FTIR, organic element, and zeta potential analyses. The key factors influencing the phosphate adsorption were the temperature in the second reaction step and EDA dosage. Langmuir isotherm and pseudo-second-order kinetic models predicted the phosphate adsorption on the RS-PA very well. A complete phosphate removal was achieved at 50 mg/L phosphate concentration, 10 g/L adsorbent dosage and 25 ℃ in 10 min. The exothermic nature of phosphate adsorption on RS-PA was confirmed since the temperature rise reduced the adsorption of phosphate on the adsorbent. These results demonstrate that full component rice straw-based phosphate adsorbent was successfully prepared for the removal of phosphorus compounds from waste water.

Recent advances in developing innovative sorbents for phosphorus removal-perspective and opportunities.

Phosphorus is an essential mineral for the growth of plants which is supplied in the form of fertilizers. Phosphorus remains an inseparable part of developing agrarian economics. Phosphorus enters waterways through three different sources: domestic, agricultural, and industrial sources. Rainfall is the main cause for washing away a large amount of phosphates from farm soils into nearby waterways. The surplus of phosphorus in the water sources cause eutrophication and degradation of the habitat with an adverse effect on aquatic life and plants. Phosphate elimination is necessary to control eutrophication in water sources. Among the different methods reported for the removal and recovery of phosphorus: ion exchange, precipitation, crystallization, and others, adsorption standout as a sustainable solution. The current review offers a comparative assessment of the literature on novel materials and techniques for the removal of phosphorus. Herein, different adsorbents, their behaviors, mechanisms, and capacity of materials are discussed in detail. The adsorbents are categorized under different heads: iron-based, silica-alumina-based, calcium-based, biochar-based wherein the metal and metal oxides are employed in phosphorus removal. The ideal attribute of adsorbent will be the utilization of spent adsorbents as a phosphate plant food and a soil conditioner in agriculture. The review provides the perspective on the current research with potential challenges and directives for possible research in the field.

Trapping and structural characterisation of a covalent intermediate in vitamin B6 biosynthesis catalysed by the Pdx1 PLP synthase.

The Pdx1 enzyme catalyses condensation of two carbohydrates and ammonia to form pyridoxal 5-phosphate (PLP) via an imine relay mechanism of carbonyl intermediates. The I333 intermediate characterised here using structural, UV-vis absorption spectroscopy and mass spectrometry analyses rationalises stereoselective deprotonation and subsequent substrate assisted phosphate elimination, central to PLP biosynthesis.