Slow Hydrolysis Research Articles

Formation of active Fe(OH)3 in situ for enhancing arsenic removal from water by the oxidation of Fe(II) in air with the presence of CaCO3

The wide-spread arsenic contamination is considered one of the most global serious environmental issues in the world. In this work, enhanced arsenic removal from water by the oxidation of FeSO4 with CaCO3 in air was investigated and the mechanisms were discussed. Oxidation of Fe(II) into Fe(OH)3 in air became possible in the presence of CaCO3, of which the hydrolyzed OH− from CaCO3 changed the conversion route of Fe(II) to Fe(OH)3. Freshly generated Fe(OH)3 in situ presented high activity for arsenic removal, with Fe/As molar ratio at 2 giving the removal rate of 99.93% and low remaining concentration of 0.035 mg/L from 50 mg/L initial concentration. Precipitation products were characterized by a set of analytical methods including XRD, XPS and Raman analyses to confirm the existence of ferric arsenate phase. Different from using Ca(OH)2 with enough OH− group, the slow hydrolysis of CaCO3 resulted in a continuous generation of fresh Fe(OH)3 for arsenate precipitation and could avoid its rapid transformation into stable FeOOH of large particle size to lose the activity. Aging the ferric compositions by prolonged agitation of Fe(II) and CaCO3 before with arsenate solution confirmed the growth of FeOOH and resulted in a rapid decrease in the capacity for arsenic removal. The observed phenomena were interpreted based on the difference between the precipitation by fresh Fe(OH)3 and the adsorption by large crystalline particles of FeOOH. Controlling the forming speed of ferric composition from Fe(II) with the addition of solid CaCO3 to maintain a fresh state as an easy operation could enhance tremendously its efficiency for As removal, with the ever highest capacity of 248 mg/g among iron absorbents.

Amorphous nanoporous WOx modification for stability enhancement and hysteresis reduction in TiO2-based perovskite solar cells

This work focuses on reducing the hysteresis and improving the stability of TiO2-based perovskite solar cells. A simple slow hydrolysis and rapid evaporation (SHRE) method was developed to deposit amorphous nanoporous WOx up on the TiO2 base at low temperature to form a TiO2-WOx bilayer as composite electron transport materials (ETMs) for efficient CH3NH3PbI3 solar cells. In the composite bilayers, the nanoporous WOx sublayer functions as an effective scaffold to modify the electrical contact between the perovskite and TiO2, and also as an anti-reflective film to enhance light transmittance. The WOx modifying layer much reduces the serious hysteresis and the dependence of power conversion efficiencies (PCEs) on the J–V scan rates. Moreover, it has also significantly enhanced the long-term stability of solar cells. The functioning mechanism for the WOx modifying layer in the TiO2-WOx composite ETMs is explored and interpreted in terms of nanoporous inorganic scaffolds and also the salutary effect of capacitive currents from the high-capacitance WOx.

Bridging the Micro-Macro Gap between Single-Molecular Behavior and Bulk Hydrolysis Properties of Cellulase.

The microscopic kinetics of enzymes at the single-molecule level often deviate considerably from those expected from bulk biochemical experiments. Here, we propose a coarse-grained-model approach to bridge this gap, focusing on the unexpectedly slow bulk hydrolysis of crystalline cellulose by cellulase, which constitutes a major obstacle to mass production of biofuels and biochemicals. Building on our previous success in tracking the movements of single molecules of cellulase on crystalline cellulose, we develop a mathematical description of the collective motion and function of enzyme molecules hydrolyzing the surface of cellulose. Model simulations robustly explained the experimental findings at both the microscopic and macroscopic levels and revealed a hitherto-unknown mechanism causing a considerable slowdown of the reaction, which we call the crowding-out effect. The size of the cellulase molecule impacted significantly on the collective dynamics, whereas the rate of molecular motion on the surface did not.

Improving Post-Anaerobic Digestion of Full-Scale Anaerobic Digestate Using Free Ammonia Treatment

Post-anaerobic digestion of full-scale anaerobic digestate (AD) is used in enhancing sludge reduction in some sewage treatment plants (STPs). However, the AD degradation is usually inhibited due to its slow hydrolysis rate and low degradability. This study presents an innovative pretreatment method by using free ammonia (FA, i.e., NH3) to improve post-anaerobic digestion full-scale AD degradation. The FA treatment at over 360 mg NH3-N/L for 24 h has improved AD degradation with the highest solubilization (0.1 mg chemical oxygen demand (COD)/mg volatile solids (VS), at 850 mg NH3-N/L), being 5.3 times that without pretreatment (0.019 mg COD/mg VS). After 8 days of post-anaerobic digestion, non-pretreated AD has degraded 8.5%, while the FA pretreated AD at 360–850 mg NH3-N/L has degraded 9.9–10.9%, representing a relative increase of 14–22%. The mathematical model captured the tested data well with R2 > 0.994 in all cases, and the model revealed that AD degradation improvement was attributed to an increase ...

Evaluation of Commercial Additives Used with Granular Urea for Nitrogen Conservation

Core Ideas Urease and nitrification inhibitors can reduce N loss from granular urea. Agrotain Ultra functioned as a urease inhibitor, Nutrisphere‐N, and NZone did not. Agrotain Ultra reduced ammonia volatilization, Nutrisphere‐N, and NZone had little effect. SuperU and Instinct inhibited nitrification, Nutrisphere‐N, and NZone did not. ABSTRACTUrea is subject to loss by ammonia volatilization, and, after nitrification, by leaching and denitrification. This study evaluated commercial products marketed as fertilizer additives for granular urea for the purpose of reducing N loss. In a urea hydrolysis study, urea granules were applied to three soils, and hydrolysis measured for 10 d. The urea granules were untreated, or treated with Nutrisphere‐N (Verdesian Life Sciences, Cary, NC), NZone (AgXplore, Parma, MO), or Agrotain Ultra (Koch Agronomic Services, Wichita, KS). Agrotain Ultra was effective in slowing urea hydrolysis, but amending the granules with Nutrisphere‐N and NZone did not slow urea hydrolysis. In a ammonia volatilization study, the treatments were the same, two soils were used, and volatilization was measured over 14 d. Agrotain Ultra was effective in reducing ammonia loss compared to untreated urea granules, but amending the granules with Nutrisphere‐N and NZone had little effect. In a nitrification study, three soils were treated with urea granules, SuperU granules (Koch Agronomic Services, Wichita, KS), or urea granules treated with Nutrisphere‐N, NZone, or Instinct (Dow Agrosciences, Indianapolis, IN). The progress of nitrification was measured after 2 and 4 wk of incubation. SuperU granules, or granules treated with Instinct nitrified more slowly than untreated urea granules, amending urea granules with Nutrisphere‐N and NZone did not slow nitrification. The three experiments do not support the use of Nutrisphere‐N or NZone as fertilizer additives for granular urea, for the purpose of reducing N loss.

The Orphan Kinesin PAKRP2 Achieves Processive Motility via a Noncanonical Stepping Mechanism

Phragmoplast-associated kinesin-related protein 2 (PAKRP2) is an orphan kinesin in Arabidopsis thaliana that is thought to transport vesicles along phragmoplast microtubules for cell plate formation. Here, using single-molecule fluorescence microscopy, we show that PAKRP2 is the first orphan kinesin to exhibit processive plus-end-directed motility on single microtubules as individual homodimers. Our results show that PAKRP2 processivity is achieved despite having an exceptionally long (32 residues) neck linker. Furthermore, using high-resolution nanoparticle tracking, we find that PAKRP2 steps via a hand-over-hand mechanism that includes frequent side steps, a prolonged diffusional search of the tethered head, and tight coupling of the ATP hydrolysis cycle to the forward-stepping cycle. Interestingly, truncating the PAKRP2 neck linker to 14 residues decreases the run length of PAKRP2; thus, the long neck linker enhances the processive behavior. Based on the canonical model of kinesin stepping, such a long neck linker is expected to decrease the processivity and disrupt the coupling of ATP hydrolysis to forward stepping. Therefore, we conclude that PAKRP2 employs a noncanonical strategy for processive motility, wherein a long neck linker is coupled with a slow ATP hydrolysis rate to allow for an extended diffusional search during each step without sacrificing processivity or efficiency.

Electrocoagulation of tetrafluoroborate (BF4−) and the derived boron and fluorine using aluminum electrodes

Tetrafluoroborate anion (BF4−) is found in the streams of flue-gas desulfurization and borosilicate glasses etching which deteriorates water quality through slow hydrolysis into boric acid and fluoride. Decomposition and electrocoagulation (EC) of BF4− were studied using metallic aluminum as the sacrificial electrode. The dissolved Al(III) from the anode could efficiently decompose BF4− in forms of fluoroaluminate complexes, and the derived boric acid and fluoride ion were removed by sweep flocculation. Major variables were investigated to optimize EC, including the reaction pH, initial concentration of BF4−, current density and electrolyte type. The mechanism of EC process was elucidated with the kinetics of consecutive reactions. Experimental results suggested that the removal of BF4− and total fluoride were less influenced by pH, and that of total boron reached a maximum at pH 8 which favored the surface complexation between borate species and EC precipitates. Under the conditions: [BF4−]0 = 9.3 mM, [NaCl] = 10 mM, pH = 8.0, current density = 5 mA/cm2, 98.3% of BF4− was decomposed and the removal of total fluoride and boron attained 98.2% and 74.1%, respectively within 3 h. EC using the Al electrode outperformed the conventional chemical coagulation and reduced the levels of BF4, B(OH)3 and F− in aqueous solution synergically.

Highly Efficient Synthesis of Alkyl Levulinates from α-Angelica Lactone, Catalyzed with Lewis Acidic Trifloaluminate Ionic Liquids Supported on Carbon Nanotubes

Levulinic acid esters (LAEs) were synthesized from α-angelica lactone and alcohols, in a reaction catalyzed by a new family of chloride-free Lewis acidic ionic liquids, containing trifloaluminate anions, [Al(OTf)3+n]n−. Changing the catalyst from poorly soluble Al(OTf)3 (used as suspension) to fully homogeneous trifloaluminate ionic liquids resulted in shorter reaction times required for full α-AL conversion (60 min at 60 °C for 0.1 mol % catalyst loading) and unprecedented selectivities to LAEs, reaching >99%. Supporting the trifloaluminate ionic liquid on multiwalled carbon nanotubes gave an easily recyclable system, with no leaching observed over six cycles. Mechanistic considerations suggest that the propensity of Al(OTf)3 to undergo very slow hydrolysis results in the correct balance of Bronsted and Lewis acidic sites in the system, which inhibit byproduct formation.

Insights into base-free OsO4-catalyzed aminohydroxylations employing chiral ligands

Attempts to perform the OsO4-catalyzed enantioselective base-free aminohydroxylation of β,β-disubstituted enoates are described. Low yields and racemic products were obtained in the presence of standard chiral ligands, suggesting the occurrence of a “Second Cycle” process due to slow hydrolysis of the amino alcohol product from the Os metal center. Support for this hypothesis was provided by the slightly improved enantioselectivity (60:40 er) obtained with an amino alcohol ligand. Based on density functional theory calculations, it is proposed that the lack of significant enantioselectivity is due to a low-energy (3 + 2) oxo/imido cycloaddition transition state without the chiral ligand in the Second Cycle that outcompetes protonolysis in the First Cycle.

Hg2+-Promoted Spirolactam Hydrolysis Reaction: A Design Strategy for the Highly Selective Sensing of Hg2+ over other Metal Ions in Aqueous Media.

A mercury sensor (N-(rhodamine-6G)lactam-ethylenediamine-4-dimethylamino-cinnamaldehyde—RLED) based on the Hg2+-promoted hydrolysis reaction has been designed and developed with a combination of theoretical calculations and experimental investigations. The interaction between RLED and Hg2+ goes through a fast-initial stage with formation of a 1:1 complex, followed by a slow hydrolysis process. The formation of durable intermediate complexes is due to quite a long hydrolysis reaction time. As a result, RLED can selectively detect Hg2+ in the presence of other metal ions, with a detection limit of 0.08 μM for the colorimetric method, and of 0.008 μM with the fluorescent method. In addition, the RLED sensor can work in a solution with a small amount of organic solvent, with a wide pH range from 5 to 10. The time-dependent density functional theory has been used for investigations of the excitation and de-excitation processes in RLED, intermediate complexes, and reaction products, thereby clarifying the changes in the fluorescence intensity before and after the RLED interacts with Hg2+ ions.

Phospholipid and Triglyceride keep vortex-dispersed sulfur mustard analog as undissolved droplets which induce necrosis from nearby cells via declining mitochondrial membrane potential

SM (Sulfur mustard) is an oily, hydrophobic, and lipophilic chemical agent that damages cells with intricate patterns. CEES (2-chloroethyl ethyl sulfide soluble) is a standard SM analog commonly employed in the toxicity mechanism study. To obtain ideal results in vitro, researchers should disperse CEES well in the medium, avoiding the presence of undissolved droplets. However, such a purpose is not easy to reach under the conventional solution preparation, and the information about droplet formation and function is little available. Here, we showed that phospholipid and triglyceride, two essential components of serum lipids, could prevent CEES from dissolving in water after vortex, which kept partial CEES as small droplets. By detecting CEES level, we proved that residual droplets slowed CEES hydrolysis and conversion. Under the microscope, CEES droplets were observed to degrade and diffuse with time to induce the necrosis and mitochondrial membrane potential decline from nearby cells. In conclusion, the damage pattern of CEES droplets is quite different from that of dissolved CEES, and a low level of phospholipid and triglyceride is beneficial for preventing droplets formation in preparing CEES solution.

Time-controlled synthesis of the 3D coordination polymer U(1,2,3-Hbtc)2 followed by the formation of molecular poly-oxo cluster {U14} containing hemimellitate uranium(iv).

Two coordination compounds bearing tetravalent uranium were synthesized in the presence of tritopic hemimellitic acid in acetonitrile with a controlled amount of water (H2O/U ≈ 8) and structurally characterized. Compound 1, [U(1,2,3-Hbtc)2]·0.5CH3CN is constructed around an eight-fold coordinated uranium cationic unit [UO8] linked by the poly-carboxylate ligands to form dimeric subunits, which are further connected to form infinite corrugated ribbons and a three-dimensional framework. Compound 2, [U14O8(OH)4Cl8(H2O)16(1,2,3-Hbtc)8(ox)4(ac)4] ({U14}) exhibits an unprecedented polynuclear {U14} poly-oxo uranium cluster surrounded by O-donor and chloride ligands. It is based on a central core of [U6O8] type surrounded by four dinuclear uranium-subunits {U2}. Compound 1 was synthesized by a direct reaction of hemimellitic acid with uranium tetrachloride in acetonitrile (+H2O), while the molecular species ({U14} (2)) crystallized from the supernatant solution after one month. The slow hydrolysis reaction together with the partial decomposition of the starting organic reactants into oxalate and acetate molecules induces the generation of such a large poly-oxo cluster with fourteen uranium centers. Structural comparisons with other closely related uranium-containing clusters, such as the {U12} cluster based on the association of inner core [U6O8] with three dinuclear sub-units {U2}, were performed.

Evidence that a catalytic glutamate and an 'Arginine Toggle'act in concert to mediate ATP hydrolysis and mechanochemical coupling in a viral DNA packaging motor.

ASCE ATPases include ring-translocases such as cellular helicases and viral DNA packaging motors (terminases). These motors have conserved Walker A and B motifs that bind Mg2+-ATP and a catalytic carboxylate that activates water for hydrolysis. Here we demonstrate that Glu179 serves as the catalytic carboxylate in bacteriophage λ terminase and probe its mechanistic role. All changes of Glu179 are lethal: non-conservative changes abrogate ATP hydrolysis and DNA translocation, while the conservative E179D change attenuates ATP hydrolysis and alters single molecule translocation dynamics, consistent with a slowed chemical hydrolysis step. Molecular dynamics simulations of several homologous terminases suggest a novel mechanism, supported by experiments, wherein the conserved Walker A arginine ‘toggles’ between interacting with a glutamate residue in the ‘lid’ subdomain and the catalytic glutamate upon ATP binding; this switch helps mediate a transition from an ‘open’ state to a ‘closed’ state that tightly binds nucleotide and DNA, and also positions the catalytic glutamate next to the γ-phosphate to align the hydrolysis transition state. Concomitant reorientation of the lid subdomain may mediate mechanochemical coupling of ATP hydrolysis and DNA translocation. Given the strong conservation of these structural elements in terminase enzymes, this mechanism may be universal for viral packaging motors.

Quantitation of fast hydrolysis of cellulose catalyzed by its substituents for potential biomass conversion

This paper investigates the accelerated acidic hydrolysis of cellulose by its substituents for potential biomass conversion. Insufficient pretreatments and slow cellulose hydrolysis are major obstacles that impede efficient hydrolysis of cellulose. Substituted cellulose, such as dyed cotton, has large availability. It is susceptible to acidic hydrolysis and can be used for biomass conversion without any pretreatments. To understand the mechanism of accelerated hydrolysis of cellulose by its substituents is a prerequisite for cellulosic biomass conversion with high efficiency. Substituents with different charge properties were synthesized and their interactions with oxocarbenium ions were studied based on Density Functional Theory. Results indicate that hydrolysis rate is affected by field effect from substituents. Such field effect is dominated by amounts of negative charges on substituents and distance between negatively charged groups and oxocarbenium. Hydrolysis rate of dye-substituted cotton is higher than or comparable to that applied with other catalytic approaches.

Enhancing Anaerobic Digestion of Waste Activated Sludge by Solid–Liquid Separation via Isoelectric Point Pretreatment

Anaerobic bioconversion of waste activated sludge (WAS) into methane is often limited by the slow hydrolysis rate and/or poor methane potential. In this study, a novel pretreatment strategy based on the isoelectric point of sludge particulate is proposed to enhance methane production from WAS. Pretreatment of WAS for 4 h at room temperature substantially changed the physicochemical properties of sludge particulate, resulting in the disintegration of WAS. The experimental results showed that the apparent activation energy of sludge organic solubilization was decreased by 49.5% and the surface site density of sludge particulate was increased by 71.2%, indicating that by this pretreatment WAS solubilization was enhanced and the surface binding sites for enzymes were decreased. In addition, compared to the conventional pretreatment methods, the main metal contents of WAS were decreased by 41.4% after this pretreatment, suggesting the possibility of simultaneously enhancing methane conversion and removing heavy metals from WAS. The biochemical methane potential assays demonstrated that after pretreatment the hydrolysis and acidification of sludge were significantly improved, with the highest volatile fatty acid concentration (3364 ± 28 mg/L) being more than twice that of the untreated samples. Model-based analysis indicated that pretreatment improved methane potential by approximately 19% (from 197.5 ± 8.3 to 242.8 ± 6.2 mL CH4/g volatile solids (VS)), thereby changing methane production kinetics. Further analysis indicated that after pretreatment the methanogenic bacteria growth, rather than the hydrolysis reaction of sludge, became the rate-limiting step in the anaerobic digestion (AD) process. These findings, however, may provide a new direction for enhancing the AD efficiency of WAS.

One-Dimensional-Like Titania/4'-Pentyl-4-Biphenylcarbonitrile Composite Synthesized Under Magnetic Field and its Structure-Photocatalytic Activity Relationship.

The demonstration of the structure–properties relationship of shape-dependent photocatalysts remains a challenge today. Herein, one-dimensional (1-D)-like titania (TiO2), as a model photocatalyst, has been synthesized under a strong magnetic field in the presence of a magnetically responsive liquid crystal as the structure-aligning agent to demonstrate the relationship between a well-aligned structure and its photocatalytic properties. The importance of the 1-D-like TiO2 and its relationship with the electronic structures that affect the electron–hole recombination and the photocatalytic activity need to be clarified. The synthesis of 1-D-like TiO2 with liquid crystal as the structure-aligning agent was carried out using the sol–gel method under a magnetic field (0.3 T). The mixture of liquid crystal, 4′-pentyl-4-biphenylcarbonitrile (5CB), tetra-n-butyl orthotitanate (TBOT), 2-propanol, and water, was subjected to slow hydrolysis under a magnetic field. The TiO2–5CB took a well-aligned whiskerlike shape when the reaction mixture was placed under the magnetic field, while irregularly shaped TiO2–5CB particles were formed when no magnetic field was applied. It shows that the strong interaction between 5CB and TBOT during the hydrolysis process under a magnetic field controls the shape of titania. The intensity of the emission peaks in the photoluminescence spectrum of 1-D-like TiO2–5CB was lowered compared with the TiO2–5CB synthesized without the magnetic field, suggesting the occurrence of electron transfer from 5CB to the 1-D-like TiO2–5CB during ultraviolet irradiation. Apart from that, direct current electrical conductivity and Hall effect studies showed that the 1-D-like TiO2 composite enhanced electron mobility. Thus, the recombination of electrons and holes was delayed due to the increase in electron mobility; hence, the photocatalytic activity of the 1-D-like TiO2 composite in the oxidation of styrene in the presence of aqueous hydrogen peroxide under UV irradiation was enhanced. This suggests that the 1-D-like shape of TiO2 composite plays an important role in its photocatalytic activity.

Deciphering the super relaxed state of human β-cardiac myosin and the mode of action of mavacamten from myosin molecules to muscle fibers

Mutations in β-cardiac myosin, the predominant motor protein for human heart contraction, can alter power output and cause cardiomyopathy. However, measurements of the intrinsic force, velocity, and ATPase activity of myosin have not provided a consistent mechanism to link mutations to muscle pathology. An alternative model posits that mutations in myosin affect the stability of a sequestered, super relaxed state (SRX) of the protein with very slow ATP hydrolysis and thereby change the number of myosin heads accessible to actin. Here we show that purified human β-cardiac myosin exists partly in an SRX and may in part correspond to a folded-back conformation of myosin heads observed in muscle fibers around the thick filament backbone. Mutations that cause hypertrophic cardiomyopathy destabilize this state, while the small molecule mavacamten promotes it. These findings provide a biochemical and structural link between the genetics and physiology of cardiomyopathy with implications for therapeutic strategies.

A numerical modelling and simulation of core-scale sandstone acidizing process: a study on the effect of temperature

A wide and comprehensive understanding of the chemical reactions and mechanisms of HBF4 is crucial as it significantly influences its performance in stimulating a sandstone formation. In general, it is well-known that HBF4 is able to provide a deeper penetration into the sandstone matrix before being spent due to its uniquely slow hydrolysis ability to produce HF. In the present study, a 3D numerical modelling and simulation were conducted to examine the capability of HBF4 in enhancing the porosity and permeability of the sandstone matrix. The model is built in COMSOL® Multiphysics commercial software of computational fluid dynamics (CFD) to simulate the acid core flooding process on sandstone core. The model had been validated against the experimental data in the literature. The results matched with the measured plot data very well. The effect of temperature on the performance HBF4 sandstone acidizing is evaluated in this study. The simulation results indicated that at low temperature of 25 °C, HBF4 is not very effective, as justified in its poor porosity and permeability increments of only 1.07 and 1.23, respectively. However, at elevated temperatures, the porosity and permeability enhancement also become increasingly more significant, which showed 1.26 and 2.06, respectively, at 65 °C; and 1.67 and 7.06, respectively, at 105 °C. Therefore, one can conclude that HBF4 acid treatment performed better at elevated temperatures due to increased hydrolysis rate, which is a governing function in HBF4 sandstone acidizing. Overall, this model had provided a reliable alternative to optimize various other parameters of HBF4 acid treatment.

Preparation of one dimensional silver nanowire/nickel-cobalt layered double hydroxide and its electrocatalysis of glucose

A novel silver nanowire/nickel–cobalt layered double hydroxide (AgNW/NiCo LDH) nanocomposite was successfully synthesized, after which a glucose sensor was fabricated. AgNW was synthesized by ethylene glycol as reductant in presence of Fe3+, and NiCo LDH grafted vertically along the 1D AgNW by slow hydrolysis of urea. The morphology and composition of AgNW/NiCo LDH were characterized by Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and Fourier transform infrared spectroscopy. The electrochemical investigation showed that the AgNW/NiCo LDH/GCE exhibited excellent electrocatalytic ability to glucose oxidation, with a linear range from 0.002 mM to 6 mM at a low applied potential of 0.4 V (vs. SCE) and a low detection limit of 0.66 μM at the signal-to-noise ratio of 3. It is expected that the AgNW/NiCo LDH nanocomposites appear to be a promising catalyst for non-enzymatic glucose sensor.

Enhanced phosphate removal from wastewater by using in situ generated fresh trivalent Fe composition through the interaction of Fe(II) on CaCO3

Excessive existences of nutrients such as phosphate in the aqueous environment remain as a heavy concern although many researches have been reported for dealing with their removal. Based on the understanding toward the interactions of Fe compounds with phosphate and carbonate from many available researches, we designed a very simple and efficient approach for phosphate removal by using in situ generated fresh trivalent Fe composition through the interaction of Fe(II) as FeSO4 on CaCO3. Addition and agitation of Fe(II) and CaCO3 simultaneously to phosphate solution allowed an amorphous Fe(III)-P or Ca-Fe(III)-P precipitation, with a phosphate removal rate close to 100%, to reduce the residual phosphorus concentration less than 0.03 mg/L from 100 mg/L, reaching the discharge limit, even with the addition amounts of CaCO3 as low as a stoichiometric ratio of CaCO3/PO43− at 0.9 and ratio of Fe(II)/PO43− at 1.5, and the percent of P2O5 in the precipitate was as high as 19.4% enough as phosphate source for fertilizer production. Different from the alkaline process with enough OH− group, the slow hydrolysis of CaCO3 resulting in low concentration of OH− group for the formation of Fe(OH)2, which was oxidized soon by air into trivalent Fe, achieved a continuous generation of fresh ferric composition for phosphate precipitation and could avoid its rapid formation and subsequent transformation into stable FeOOH of large particle size to lose the activity. These results based on the synergistic effect of using CaCO3 and Fe(II) together may have applications in the treatment of eutrophic wastewater through a process with many advantages of easy operation and low-cost besides the high removal efficiency with phosphate percentage inside the precipitate high enough to serve for fertilizer production.