Phosphate Capture Research Articles

Robust phosphate capture over inorganic adsorbents derived from lanthanum metal organic frameworks

Excessive phosphate in water can cause severe water quality problems owing to its somatotrophic effect on microorganisms. Herein, a superstructural phosphate scavenger, La-MOF-500, composed of La2O2CO3, is rationally designed by derivation from lanthanum metal organic frameworks (La(1,3,5-BTC)(H2O)6) by calcination. La-MOF-500 has a hierarchical micro/nano structure of microsphere-nanorod-nanoparticle: urchin-like microsphere is comprised of many nanorods and the individual nanorod was formed by piling up plentiful thin nanoparticles. The hierarchical micro/nano structure provides La-MOF-500 with an intriguing phosphate capture capacity of 173.8mgP/g and a high utilization of lanthanum active sites, simultaneously, which was a challenge in previous research. Moreover, La-MOF-500 exhibits a good tolerance of foreign species. Even in the water from Songhua River (China), La-MOF-500 can remove phosphate to be less than 10μgP/L. This development is expected to be meaningful for practical water purification.

Biochar and enhanced phosphate capture: Mapping mechanisms to functional properties

A multi-technique analysis was performed on a range of biochar materials derived from secondary organic resources and aimed at sustainable recovery and re-use of wastewater phosphorus (P). Our purpose was to identify mechanisms of P capture in biochar and thereby inform its future optimisation as a sustainable P fertiliser. The biochar feedstock comprised pellets of anaerobically digested sewage sludge (PAD) or pellets of the same blended in the ratio 9:1 with ochre sourced from minewater treatment (POCAD), components which have limited alternative economic value. In the present study the feedstocks were pyrolysed at two highest treatment temperatures of 450 and 550 °C. Each of the resulting biochars were repeatedly exposed to a 20 mg l−1 PO4-P solution, to produce a parallel set of P-exposed biochars. Biochar exterior and/or interior surfaces were quantitatively characterised using laser-ablation (LA)-ICP-MS, X-ray diffraction, X-ray photo-electron spectroscopy (XPS) and scanning electron microscopy coupled with energy dispersive X-ray. The results highlighted the general importance of Fe minerals in P capture. XPS analysis of POCAD550 indicated lower oxidation state Fe2p3 bonding compared to POCAD450, and LA-ICP-MS indicated stronger covariation of Fe and S, even after P exposure. This suggests that low-solubility Fe/S compounds are formed during pyrolysis, are affected by process parameters and impact on P capture. Other data suggested capture roles for aluminium, calcium and silicon. Overall, our analyses suggest that a range of mechanisms for P capture are concurrently active in biochar. We highlighted the potential to manipulate these through choice of form and composition of feedstock as well as pyrolysis processing, so that biochar may be increasingly tailored towards specific functionality.

Preferable uptake of phosphate by hydrous zirconium oxide nanoparticles embedded in quaternary-ammonium Chinese reed

Phosphate capture from aqueous was conducted using hydrous zirconium oxide (HZO) embedded in quaternary-ammonium Chinese reed (CR-N+-HZO), and the characteristics of adsorbent was determined. HZO was dispersed as nanoparticles or nano-clusters on the external or inside the networking pores of CR-N+-HZO. The surface of CR-N+-HZO was heterogeneous with multiple adsorption sites, HZO nanocomposite and N+(CH2CH3)3Cl−, which both contributed to the adsorption process. The phosphate uptake by CR-N+-HZO was optimal at pH 3.0 and phosphate uptake by HZO nanocomposite was greatly inhibited at alkaline pH. Kinetics studies suggested that both the intra-particle mass-transfer and external resistances were likely to be the rate controlling steps. The Qmax (maximum adsorption capacity) of phosphate uptake by CR-N+-HZO and CR-N+ (30°C) calculated based on Langmuir model was about 59.2mg(P)/g(CR-N+-HZO) and 30.4mg(P)/g(CR-N+). A high usage efficiency of Zr in CR-N+-HZO was observed with calculated molar ratio of P/Zr to be 3.07.

A Cleanup Method for Mass Spectrometric Analysis of Sphingosine- and Ceramide-1-Phosphate in Blood and Solid Tissue Using a Phosphate Capture Molecule.

Cleanup technology and mass spectrometric determination of sphingosine-1-phosphate (S1P) using a phosphate capture molecule are shown. The protocol is rapid, requires neither thin-layer chromatography nor liquid chromatography, and is applicable to both blood and solid tissue samples. The mass spectrometric method is also applicable to ceramide-1-phosphate.

Climate forcing for dynamics of dissolved inorganic nutrients at Palmer Station, Antarctica: An interdecadal (1993–2013) analysis

AbstractWe analyzed 20 years (1993–2013) of observations of dissolved inorganic macronutrients (nitrate, N; phosphate, P; and silicate, Si) and chlorophyll a (Chl) at Palmer Station, Antarctica (64.8°S, 64.1°W) to elucidate how large‐scale climate and local physical forcing affect the interannual variability in the seasonal phytoplankton bloom and associated drawdown of nutrients. The leading modes of nutrients (N, P, and Si empirical orthogonal functions 1, EOF1) represent overall negative anomalies throughout growing seasons, showing a mixed signal of variability in the initial levels and drawdown thereafter (low‐frequency dynamics). The second most common seasonal patterns of nitrate and phosphate (N and P EOF2) capture prolonged drawdown events during December–March, which are correlated to Chl EOF1. Si EOF2 captures a drawdown event during November–December, which is correlated to Chl EOF2. These different drawdown patterns are shaped by different sets of physical and climate forcing mechanisms. N and P drawdown events during December–March are influenced by the winter and spring Southern Annular Mode (SAM) phase, where nutrient utilization is enhanced in a stabilized upper water column as a consequence of SAM‐driven winter sea ice and spring wind dynamics. Si drawdown during November–December is influenced by early sea ice retreat, where ice breakup may induce abrupt water column stratification and a subsequent diatom bloom or release of diatom cells from within the sea ice. Our findings underscore that seasonal nutrient dynamics in the coastal WAP are coupled to large‐scale climate forcing and related physics, understanding of which may enable improved projections of biogeochemical responses to climate change.

Analysis of Molecular Species Profiles of Ceramide-1-phosphate and Sphingomyelin Using MALDI-TOF Mass Spectrometry.

Ceramide-1-phosphate (C1P) is a potential signaling molecule that modulates various cellular functions in animals. It has been known that C1P with different N-acyl lengths induce biological responses differently. However, molecular species profiles of the C1P in animal tissues have not been extensively examined yet. Here, we developed a method for determination of the molecular species of a C1P using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry with Phos-tag, a phosphate capture molecule. The amounts of total C1P in skin, brain, liver, kidney and small intestine of mice were determined to be 344, 151, 198, 96 and 90 pmol/g wet weight, respectively. We found a C1P species having an α-hydroxypalmitoyl residue (h-C1P, 44 pmol/g wet weight) in mouse skin. The h-C1P was detected only in the skin, and not other tissues of mice. The same analysis was applied to sphingomyelin after conversion of sphingomyelin to C1P by Streptomyces chromofuscus phospholipase D. We found that molecular species profiles of sphingomyelin in skin, kidney and small intestine of mice were similar to those of C1P in corresponding tissues. In contrast, molecular species profiles of sphingomyelin in liver and brain were quite different from those of C1P in these tissues, indicating selective synthesis or degradation of C1P in these tissues. The method described here will be useful for detection of changes in molecular species profiles of C1P and sphingomyelin.

Hydrous iron oxide modified diatomite as an active filtration medium for phosphate capture.

A simple method to functionalize diatomite with hydrous iron oxide was attempted and its performance as a new active filtration material to remove and recover phosphate from water was investigated under varying solution conditions. The Langmuir phosphate adsorption capacity increased from 0.6 mgP/g for raw diatomite to 4.89, 14.71, 25.02 mgP/g for hydrous iron oxide modified diatomite (HIOMD), depending on the amount of iron loaded. Loading of hydrous iron oxide caused the increase in true and bulk density and a decline in filtration rate, but to a lesser extent. It was shown that the HIOMD product with suitable iron content could retain a good filtration performance with a greatly increased adsorption capacity for phosphate. The phosphate adsorption increased by decreasing pH and by increasing ionic strength at high pH levels. The adsorption process was interpreted by ligand exchange. Coexisting oxyanions of sulfate, nitrate, citrate, carbonate, silicate and humic acid showed different effects on phosphate fixation but it was presumed that their influence at their concentrations and pH levels commonly encountered in effluent or natural waters was limited, i.e., HIOMD had a reasonably good selectivity. Results in repeated adsorption, desorption and regeneration experiment showed that the adsorbed phosphate could be recovered and the material could be reused after regeneration. The column test showed that HIOMD could be potentially utilized as an adsorption filtration medium for phosphate removal and recovery from water.

Highly Efficient Phosphate Scavenger Based on Well-Dispersed La(OH)3 Nanorods in Polyacrylonitrile Nanofibers for Nutrient-Starvation Antibacteria.

La(OH)3 nanorods immobilized in polyacrylonitrile (PAN) nanofibers (PLNFs) were fabricated for the first time by electrospinning and a subsequent in situ surfactant-free precipitation method and then applied as a highly efficient phosphate scavenger to realize nutrient-starvation antibacteria for drinking water security. The immobilization by PAN nanofibers effectively facilitated the in situ formation of the aeolotropic and well-dispersed La(OH)3 nanostructures and, thus, rendered higher phosphate removal efficiency due to more exposed active sites for binding phosphate. The maximum phosphate capture capacity of La(OH)3 nanorods in PAN nanofibers was around 8 times that of the La(OH)3 nanocrystal fabricated by precipitation without PAN protection. Moreover, remarkably fast adsorption kinetics and high removal rate were observed toward low concentration phosphate due to the high activity of our materials, which can result in a stringent phosphate-deficient condition to kill microorganisms in water effectively. The present material is also capable of preventing sanitized water from recontamination by bacteria and keeping water biologically stable for drinking. Impressively, stabilized by PAN nanofibers, the La(OH)3 nanorods can be easily separated out after reactions and avoid leaking into water. The present development has great potential as a promising antimicrobial solution for practical drinking water security and treatment with a negligible environmental footprint.

Gastropod shell column reactor as on-site system for phosphate capture and recovery from aqua system

Gastropod shell (GS), whose distribution is worldwide and mineralogical assemblage is aragonite, was packed in a glass column and evaluated for phosphate capture and recovery from aqua system. The column reactor was operated in a batch-continuous mode, considered as a close approximation to a practical water treatment system, for 30 days. The time–concentration profile parameters were derived at different influent phosphate concentrations and hydraulic residence time (HRT) to determine the performance efficiency of the reactor column. The mechanism of phosphate removal was investigated and phosphate fractionation protocol was employed to elucidate the form and pattern of phosphate distribution in the spent reactor. Variations in influent phosphate concentration and HRT had minimal influence on the time–concentration profile parameters and the performance efficiency of the column reactor within the process variables studied. The first order rate constant (k1) showed that increase in the HRT of the influent in the SS column reactor does not enhance the phosphate removal. The value of the saturation index (SI) obtained over the 30 days period were all positive and the thermodynamic parameter (ΔG) was <0 which is an indication of supersaturation, the significant role of precipitation as a mechanism of phosphate removal in the reactor and spontaneity of the precipitation reaction. The order of distribution of each fraction of P, relative to the total phosphorus (T-P) in the phosphate laden SS, is as follows: dicalcium phosphate (Ca2-P) (42.5%)>ten-calcium phosphate (Ca10-P) (40.50%)>octacalcium phosphate (Ca8-P) (16.65%)>occluded phosphate (O-P) (0.35%). The simple appraisal of the fertilizer value of the spent reactor showed that it would preferentially serve as a soil conditioner cum fertilizer in acidic soil.

Lanthanum-doped ordered mesoporous hollow silica spheres as novel adsorbents for efficient phosphate removal

Lanthanum-doped ordered mesoporous hollow silica spheres were fabricated and utilized as phosphate adsorbents for the first time. Our prepared adsorbents exhibited spherical shapes with macropores in the center and ordered 2D hexagonal mesopores in the shell. By increasing the actual loading of La from 4.19 wt% to 22.44 wt%, the BET surface areas of the adsorbents decreased from 987.48 m2 g−1 to 420.38 m2 g−1, coupled with a decline in average pore diameters and total pore volumes. In the batch adsorption tests, the adsorbents with greater amounts of La loading possessed markedly enhanced adsorption capacities; in contrast, the un-doped pure ordered mesoporous hollow silica particles could hardly adsorb any phosphate in solution. The adsorption isotherms of the La-doped ordered mesoporous hollow silica spheres were represented better by using the Langmuir model than the Freundlich model. The sample with 22.44 wt% La loading exhibited a maximum phosphate capture capacity of 47.89 mg P g−1. In the kinetic study, its phosphate adsorption followed the pseudo-second-order model well. Moreover, a dramatically fast kinetic adsorption was observed in the solution with a low phosphorus concentration of 2 mg P L−1; the adsorption equilibrium was reached in 15 min, with a 99.71% phosphate removal rate. High adsorption capacities were achieved within the pH range 3.0 to 8.0; relatively high selectivity to phosphate was observed in the presence of coexisting anions.

One-pot synthesis of Fe(III)-coordinated diamino-functionalized mesoporous silica: Effect of functionalization degrees on structures and phosphate adsorption

Fe(III)-coordinated mesoporous silica adsorbents functionalized with different loadings of ethylenediamine groups were prepared by a new NH4F-assisted co-condensation method and impregnation of Fe3+ cations. Various characterization techniques, e.g. XRD, SEM, TEM, ICP-MS, elemental analysis, FT-IR spectroscopy, and nitrogen adsorption–desorption, were utilized to investigate the effect of functionalization degrees of adsorbents on their chemical composition, surface chemistry, pore structures and phosphate adsorption capacities in detail. In the batch adsorption tests, the functionalized adsorbents with increasing loadings of ethylenediamine groups possessed markedly enhanced adsorption capacities, although there was a gradual loss of ordered mesostructures accompanied. The adsorption isotherms were represented better by using Langmuir model than Freundlich model, which indicated the presence of monolayer adsorption. In particular, for the resulting adsorbent prepared with 0.5:1M ratio of AAPTS and TEOS, the maximum phosphate capture capacity calculated from Langmuir model is 20.7mg P/g. In the kinetic study, the phosphate adsorption followed pseudo-second-order equation well with a correlation coefficient of 0.999, suggesting the adsorption process be chemisorption. The phosphate adsorption efficiency of prepared adsorbent was highly pH-dependent and the high removal of phosphate was achieved within the pH between 3.0 and 6.0. The presence of Cl− and NO3- exhibited small impacts on the phosphate adsorption by using our synthesized absorbent; whereas, there were significantly negative effects from HCO3- and SO42- on the phosphate removal. In 0.010M NaOH, more than 90% of the absorbed phosphate anions on the spent adsorbent could be desorbed, suggesting the absorbent with a capacity of regeneration.

Low-cost biogenic waste for phosphate capture from aqueous system

Premised on the principle of waste minimization and affordable water and wastewater treatment system, the ability of waste African land snail shell (SS), as a sorbent, in the capture of phosphate from aqueous system was evaluated. Batch sorption process assessment of the effects of process variables showed that pH had no influence on phosphate sorption while anionic interference and organic load impacted negatively on the magnitude of phosphate uptake. Analysis of the sorption process using different kinetic models showed that the reversible first order and pseudo first order kinetic models gave poor descriptions of the process (r2=0.6977–0.8819) while the pseudo second order kinetic model gave the best description of the process (r2>0.99). Equilibrium isotherm analysis of the sorption process data showed that the Freundlich isotherm gave the best description of the process than the Langmuir and Temkin isotherm models. Estimation of the energy of sorption gave a value of 0.3318kJ/mol, which is a pointer to the fact that electrostatic interaction did not dominate the mechanism of interaction between phosphate and SS. A simple economic evaluation of the process showed that the monolayer sorption capacity of the SS for phosphate (222.22mg/g) was higher than that of other sorbents that have been screened for phosphate sorption from aqueous system and the phosphate laden SS could be used as soil conditioner cum fertilizer in agricultural practices.

Phos-tag chemistry

Recently, we found that an alkoxide-bridged dinuclear zinc(II) complex of 1,3-bis[bis(pyridin-2-ylmethyl) amino]propan-2-olate acts as a novel phosphate capture molecule under physiological conditions. The dizinc(II) complex forms a stable 1:1 complex with a phosphate monoester dianion in aqueous solutions. The X-ray crystal analysis of the 1:1 dizinc(II) complex with a p-nitrophenyl phosphate dianion disclosed that each phosphate oxygen anion binds to a zinc(II) at the fifth coordination site and that the two zinc(II) ions are separated by a distance of 3.6 A. Thus, the dizinc(II) complex having a vacancy on the two zinc(II) ions is suitable for the access of a phosphate monoester dianion. In an aqueous solution, the dizinc(II) complex strongly binds to the phenyl phosphate dianion (Kd=2.5×10-8 M) at a neutral pH. The anion selectivity indexes against SO42-, CH3COO-, Cl-, and the diphenyl phosphate monoanion at 25°C are 5.2×103, 1.6×104, 8.0×105, and >2×106, respectively. In addition, the 1:1 formation of the dizinc(II) complex and an inorganic phosphate dianion (HOPO32-) was clearly detected by matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) based on a characteristic mass shift and a total-charge change of the phosphate (from -2 to +1). This finding introduced a new procedure for the analysis of phosphorylated compounds using the dizinc(II) complex as an MS probe. Therefore, we termed the dinuclear metal complex Phos-tag as a phosphate-binding tag molecule.

Phosphate adsorption on chemically modified sugarcane bagasse fibres

Integral sugarcane bagasse fibres of about 2 cm length that were pre-treated for removal of greases and sugars were carboxymethylated on their surface, retaining about 20% of impurities (as insoluble material and water). The fibres were doped with Fe 2+ ion, by dipping in aqueous iron chloride solutions of different concentrations. This material was used to remove phosphate from water. Thermal analyses (differential scanning calorimetry – DSC) and infrared spectroscopy – FTIR show the occurrence of important changes on carboxymethylated fibres after incorporation of Fe 2+ and PO 4 3- . Non-carboxymethylated fibres, also treated with the iron solutions, also showed a good level of capture of phosphate from an aqueous solution. The chemical modification increases Fe 2+ ion adsorption on the fibre surface, increasing the efficiency of phosphate adsorption. Apparently, the process of modification, without incorporation of Fe 2+ , also improves phosphate retention. When about 4% of iron is adsorbed on the fibres, 97% of phosphate is captured on the carboxymethylated material and 94% on the non-carboxymethylated material. The absorption data fit both the Langmuir and Freundlich isotherm. When quantified by measuring the monolayer adsorption in the Langmuir isotherm model, the presence of Fe 2+ ions on the surface fibres increases the phosphate adsorption capacity by about 45%. Our results (Q max = 152 mg/g) are far superior or in the same order of magnitude, when compared with literature data, with the advantage be the raw material, waste of biomass, only somewhat changed chemically and even after the modifications compose materials harmless to the environment. ► Bagasse carboxymethylated or not, grafted with Fe 2+ , adsorbs phosphate from water. ► The higher quantity of Fe2+ on surface fibres results in higher phosphate adsorption. ► The adsorption of Fe 2+ is higher on chemically modified fibres. ► The adsorption sites are the cellulose and lignin. ► 152 mg/g is phosphate maximum amount adsorbed on fibres modified and grafted with Fe.

Molecular Modeling Studies of the Binding Characteristics of Phosphates to Sevelamer Hydrochloride – Assessing a Novel Technique to Reduce Phosphates Contamination

Recent advances in the use of polymeric materials for the remediation of phosphate from aqueous systems, including biological environments, have prompted the use of computational techniques to determine which methods are feasible to model such complex systems and to model the mechanism of binding action. In particular, Sevelamer Hydrochloride (Renagel) is used as our model polymer. A relatively simple system is constructed with a dimer of Sevelamer Hydrochloride and four phosphate ions used for capture. This work reports on molecular dynamics and Monte Carlo simulations used to determine average structure, and points of intermolecular interaction, and calculate changes in volume after the successful capture of phosphate in our model. Our resulting volume changes are of the order of 20-25%, in comparison to experimental swelling measurements on similar systems, which have an average swelling of 50-60% in aqueous media.

Detection and Quantification of On-Chip Phosphorylated Peptides by Surface Plasmon Resonance Imaging Techniques Using a Phosphate Capture Molecule

We describe herein a detection and quantification system for on-chip phosphorylation of peptides by surface plasmon resonance (SPR) imaging techniques using a newly synthesized phosphate capture molecule (i.e., biotinylated zinc(II) complex). The biotinylated compound is a dinuclear zinc(II) complex that is suitable for accessing phosphate anions as a bridging ligand on the two zinc(II) ions. The compound was exposed on the peptide array and detected with streptavidin (SA) via a biotin-SA interaction by SPR imaging. In the conventional method using antibody, both anti-phosphoserine and anti-phosphotyrosine antibodies were required for phosphoserine and phosphotyrosine detection, respectively. Detection of the phosphate group by the zinc(II) complex, however, was independent of the phosphorylated amino acid residues. The calibration curve for the phosphorylation ratios was established with a calibration chip, on which phosphoserine-containing peptide probes were immobilized. The peptide probes, which were phosphorylated on the surface by protein kinase A, were detected and quantified by SPR imaging using the zinc(II) complex, SA, and anti-SA antibody. The reaction rate and the kinetics of on-chip phosphorylation were also evaluated with the peptide array. The phosphorylation ratio was saturated at approximately 20% in 2 h in this study.

An Alkoxide-Bridged Dinuclear Zinc(II) Hexaazacryptate: A Novel Phosphate Capture Molecule in Aqueous Solution

Abstract A novel dinuclear zinc(II) hexaazacryptate (Zn2L3+) has been synthesized as a phosphate capture molecule in aqueous solution (L = an alkoxide form of 4,16-(2-hydroxypropano)-1,4,7,13,16,19-hexaazacyclotetracosane). Potentiometric pH titration study disclosed a 1:1 phenyl phosphate complexation with Zn2L3+. The dissociation constant, Kd ( = [Zn2L3+][PhOPO32−]/[Zn2L3+–PhOPO32−]) is a small value of 6 × 10 − 7 M at 35 °C with I = 0.10 (NaNO3). The X-ray crystal analysis of the p-nitrophenyl phosphate complex with Zn2L3+ showed that the phosphate dianion binds as a bridging ligand to the two zinc(II) ions. The analogous 1:1 CH3COO−-bound Zn2L3+ complex was isolated and characterized by X-ray analysis.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry of phosphorylated compounds using a novel phosphate capture molecule.

This paper introduces a simple, rapid, and sensitive procedure for the analysis of phosphorylated compounds (ROPO(3) (2-)) by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). The method is based on a characteristic mass shift and a total-charge change (from -2 to +1) of the phosphate residue due to complexation of ROPO(3) (2-) with a dinuclear zinc(II) complex (1,3-bis[bis(2-pyridinylmethyl)amino]-2-propanolato dizinc(II) complex, Zn(2)L(3+)) in aqueous solution at physiological pH. Furthermore, the use of single zinc-isotope derivatives ((64)Zn(2)L(3+) and (68)Zn(2)L(3+)) enables improvement of the sensitivity and accuracy of the analysis.

Restricted spatial expression of a high-affinity phosphate transporter in potato roots.

Phosphorus deficiency limits plant growth, and high-affinity phosphate transporters, of the Pht1 family, facilitate phosphate uptake and translocation. The family is subdivided into root specific, phosphate deprivation induced members and those also expressed in leaves. An antibody to StPT2, a potato root specific transporter, detected two bands (52 kDa and 30 kDa) on western blots of root plasma membrane extracts that were most intense in whole extracts from the root tip and slightly increased throughout the root in response to phosphate depletion. RT-PCR, using StPT2 specific primers, confirmed these findings. Low power confocal immunofluorescent images showed StPT2 expression mainly in the elongation zone at the root tip. By contrast, a vacuolar pyrophosphatase and a plasma membrane ATPase antibody labelled the whole root. High power images showed, by comparison with alpha-tubulin, cell wall and plasma membrane ATPase labelling, that StPT2 was in the epidermal plasma membrane and restricted to the apical surface. This is the first evidence of polar plasma membrane localisation of a plant nutrient transporter and is consistent with a role for StPT2 in phosphate capture and uptake.

Light microscopic visualization of transport ATPase in the chick kidney and intestine using catalytic histochemistry

To visualize the enzyme Na+/K(+)-ATPase (transport ATPase) in the chick kidney and intestine two recent methods of catalytic histochemistry were modified using capture of inorganic phosphate with lead according to Mayahara et al.(1980) or cerium after Kobayashi et al. (1987). For light microscopy a new step for the visualization of the reaction product was added; lead phosphate was visualized with (NH4)2S and cerium phosphate with the DAB-H2O2-Ni-hexamonium sulfate method. Reaction product was specifically found in the basolateral plasma membrane region of enterocytes and renal epithelial cells (distal tubules, thick ascending limbs of Henle's loops, cortical collecting ducts). Treatment of the sections with 8 mM levamisole and 40 mM L-phenylalanine before and during incubation was necessary to suppress the co-reaction of non-specific alkaline phosphatase in the microvillous zone of proximal tubules and enterocytes. The reaction specificity was controlled with 10 mM ouabain which completely inhibited the basolateral activity in enterocytes and renal epithelial cells. The described methods for transport ATPase are reliable and provide reproducible results in the chick.