Mo Sorption Research Articles

Sorption Profile of Low Specific Activity 99Mo on Nanoceria-Based Sorbents for the Development of 99mTc Generators: Kinetics, Equilibrium, and Thermodynamic Studies.

99Mo/99mTc generators play a significant role in supplying 99mTc for diagnostic interventions in nuclear medicine. However, the applicability of using low specific activity (LSA) 99Mo asks for sorbents with high sorption capacity. Herein, this study aims to evaluate the sorption behavior of LSA 99Mo towards several CeO2 nano-sorbents developed in our laboratory. These nanomaterials were prepared by wet chemical precipitation (CP) and hydrothermal (HT) approaches. Then, they were characterized using XRD, BET, FE-SEM, and zeta potential measurements. Additionally, we evaluated the sorption profile of carrier-added (CA) 99Mo onto each material under different experimental parameters. These parameters include pH, initial concentration of molybdate solution, contact time, and temperature. Furthermore, the maximum sorption capacities were evaluated. The results reveal that out of the synthesized CeO2 nanoparticles (NPs) materials, the sorption capacity of HT-1 and CP-2 reach 192 ± 10 and 184 ± 12 mg Mo·g–1, respectively. For both materials, the sorption kinetics and isotherm data agree with the Elovich and Freundlich models, respectively. Moreover, the diffusion study demonstrates that the sorption processes can be described by pore diffusion (for HT-synthesis route 1) and film diffusion (for CP-synthesis route 2). Furthermore, the thermodynamic parameters indicate that the Mo sorption onto both materials is a spontaneous and endothermic process. Consequently, it appears that HT-1 and CP-2 have favorable sorption profiles and high sorption capacities for CA-99Mo. Therefore, they are potential candidates for producing a 99Mo/99mTc radionuclide generator by using LSA 99Mo.

Structuring efficient photocatalysts into bespoke fiber shaped systems for applied water treatment

In this study, structured photocatalytic systems were successfully developed by a facile method based on Alginate molds and a wet-spinning/cross-linking technique, yielding commercial photocatalyst (Degussa P25) in the form of all-ceramic hollow fibers (HFs). Taking advantage of alginate’s exceptional sorption properties, copper augmented HFs were also developed. The structured photocatalysts were thoroughly characterised by a variety of techniques, including nitrogen adsorption, SEM/EDS, XRD, XPS and Raman. Synthesis and heat treatment parameters were found to affect the fibers’ properties, allowing their optimization. Treatment at 600 °C under Ar was found to produce the best performing photocatalysts in terms mechanical stability, resistance to attrition and photocatalytic performance. Ca-Alginate precursors led to structures with increased mechanical stability, while Cu-Alginate decorated the surface of the photocatalyst with highly dispersed copper nanoparticles, in the state of metallic and CuO. The developed materials were photo-catalytically active, while the copper decorated ceramic HFs exhibited the highest MO adsorption and photocatalytic degradation performance, reaching a MO removal of 73.4%. The synergestic effect of adsorption on the MO degradation performance was also noticed. Moreover, the copper addition facilitated the photocatalytic process by improving the electron-hole separation and inhibiting the recombination effects. The presence of carbon residue was also beneficial, enhancing the MO sorption on the photocatalysts. It is noteworthy that the structured photocatalysts retained their efficiency for at least four photocatalytic cycles. The prepared ceramic HFs exhibited enhanced mechanical properties and excellent resistance to attrition after subsequent cycles, rendering them excellent candidates for application in industrial wastewater processes.

Sorption and speciation of molybdate in soils: Implications for molybdenum mobility and availability

Molybdenum (Mo) is an emerging contaminant in the environment. To assess the mobility and availability of Mo in soils, this study investigated the effect of soil properties on the sorption and desorption of Mo in soils. The Mo K-edge X-ray absorption near edge structure (XANES) of the soils after Mo sorption showed that sorbed molybdate was the predominant species, with Fe/Al-molybdate and Ca-molybdate being the minor components in soils with low and high pH levels, respectively. Although acidic soils exhibited higher Mo sorptivity, they exhibited partial reversibility of Mo sorption, which may be attributed to the high solubility of Al-molybdate. Accordingly, the mobility of Mo may be relatively high in soils with a low pH, high exchangeable Al content, and high Fe-hydroxide crystallinity, such as Ultisols and Oxisols. At higher pHs, the sorption irreversibility of molybdate were enhanced due to the formation of Ca-molybdate precipitate. The results of this study indicated that sorption/desorption irreversibility and related mechanisms should be considered when evaluating the mobility and availability of Mo in soils.

Kinetic modeling of molybdenum sorption and transport in soils.

In this investigation, batch and column experiments were conducted to investigate the molybdenum (Mo) sorption and transport processes on a neutral-pH soil (Webster loam) and an acidic soil (Mahan sand) in Ca2+ and K+ background solutions. Batch results showed that the adsorption of Mo was strongly non-linear in both soils and amount of Mo sorbed in the acidic soil was larger than the neutral soil. The Freundlich distribution coefficients (Kf) and Langmuir sorption maxima (Smax) in Ca2+ background solution are larger than that in K+ solution, indicating greater Mo sorption in Ca2+ than in K+. Experimental breakthrough curves (BTCs) demonstrated that mobility of Mo was higher at neutral condition than that at acidic condition. A multi-reaction transport model (MRTM) formulation with two kinetic retention reactions (reversible and irreversible) well described Mo transport for Webster soil. However, MRTM model which accounts for equilibrium and kinetic sites is recommended for Mo transport in Mahan soil, reflecting different soil properties. Based on inverse modeling, the sorption forward rate coefficients (k1) obtained from Ca2+ in both soils are larger than that from K+, which consistent with batch experiment. Overall, MRTM model was capable of describing the Mo transport behavior under different geochemical conditions.

Evaluation of novel Mg/Al/Ni-BaFe ternary layered hydroxides uptake of methyl orange dye from water

MgAlNi-BaFe ternary layered hydroxide (UMLDH) and its calcined (CMLDH) form were synthesized and tested as adsorbents for methyl orange dye (MO) uptake from water. The adsorptive performances of the new magnetic nanocomposites were modeled, evaluated and optimized via response surface methodology (RSM). The UMLDH and CMLDH maximum removal efficiency and adsorption capacities data were fitted into RSM models with insignificant lack of fit (p-values<0.05) and high R2=0.991–0.997. The UMLDH and CMLDH MO adsorption capacities increased with decrease in both pH and initial MO concentration and decreased when the temperature was increased. Under optimal operating conditions, pseudo-second-order described kinetics of MO sorption on the nanocomposites, while the Freundlich isotherm gave the best fits for both the two adsorbents. The MO uptake simultaneously incorporated both mono and multi-layer surface adsorption involving strong electrostatic attraction and chemical interactions between MO and the adsorbents surface functional groups. Respectively, the obtained maximum Langmuir theoretical sorption capacity of 715.44 and 708 mg/g, indicated profoundly improved MO sorption capacities compared with many other magnetic-LDHs. These results demonstrate the potential of MgAlNi-BaFe as excellent adsorbents for effective remediation of dyes wastewater effluents.

Transport and retention of Molybdenum(VI) on iron oxide-coated sand: A modified multi reaction model

In this investigation, batch and miscible displacement experiments were performed to investigate the pH-dependent effect on retention and transport of Mo(VI) on iron oxide-coated sand (IOCS). Measured results indicated that Mo(VI) sorption was strongly nonlinear and kinetically controlled, where the amount of Mo(VI) sorbed and its reaction rates increased with decreasing solution pH. Mo(VI) breakthrough curves (BTCs) obtained at varying pHs were asymmetrical in shape and exhibited different degree of tailing, where mobility of Mo(VI) was lowest under acidic condition (pH 4.0) and highest under alkaline condition (pH 7.5). In this study, based on extended Freundlich equation, we proposed a modified multi-reaction model (M-MRM) including a pH term, which was utilized to describe pH-dependent sorption and transport process. From the goodness-of-fit of modeling results, the M-MRM model provided a good prediction for Mo(VI) retention and transport datasets on IOCS. In comparison to numerical surface complexation models (SCMs), the proposed M-MRM is relatively less complex and requires fewer parameters. Moreover, it is simpler to integrate reaction transport equations into kinetic models to simulate non-equilibrium transport behavior. Our work provided a unified kinetic model to describe pH-dependent sorption and transport in IOCS.

Tracing Molybdenum Attenuation in Mining Environments Using Molybdenum Stable Isotopes.

Molybdenum contamination is a concern in mining regions worldwide. Better understanding of processes controlling Mo mobility in mine wastes is critical for assessing potential impacts and developing water-quality management strategies associated with this element. Here, we used Mo stable isotope (δ98/95Mo) analyses to investigate geochemical controls on Mo mobility within a tailings management facility (TMF) featuring oxic and anoxic environments. These isotopic analyses were integrated with X-ray absorption spectroscopy, X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and aqueous chemical data. Dissolved Mo concentrations were inversely correlated with δ98/95Mo values such that enrichment of heavy Mo isotopes in solution reflected attenuation processes. Inner-sphere complexation of Mo(VI) with ferrihydrite was the primary driver of Mo removal and was accompanied by a ca. 1‰ isotope fractionation. Limited Mo attenuation and isotope fractionation were observed in Fe(II)- and Mo-rich anoxic TMF seepage, while attenuation and isotope fractionation were greatest during discharge and oxidation of this seepage after discharge into a pond where Fe-(oxyhydr)oxide precipitation promoted Mo sorption. Overall, this study highlights the role of sorption onto Fe-(oxyhydr)oxides in attenuating Mo in oxic environments, a process which can be traced by Mo isotope analyses.

Molybdenum-isotope signals and cerium anomalies in Palaeoproterozoic manganese ore survive high-grade metamorphism

Molybdenum (Mo) and its isotopes have been used to retrieve palaeoenvironmental information on the ocean–atmosphere system through geological time. Their application has so far been restricted to rocks least affected by severe metamorphism and deformation, which may erase or alter palaeoenvironmental signals. Environmental Mo-isotope signatures can be retrieved if the more manganese (Mn)-enriched rocks are isotopically depleted and the maximum range of δ98Mo values is close to the ~2.7‰ Mo-isotope fractionation known from Mo sorption onto Mn oxides at low temperature. Here, we show that the Morro da Mina Mn-ore deposit in Minas Gerais, Brazil, contains Mn-silicate–carbonate ore and associated graphitic schist that likely preserve δ98Mo of Palaeoproterozoic seawater, despite a metamorphic overprint of at least 600 °C. The extent of Mo-isotope fractionation between the Mn-silicate–carbonate ore and the graphitic schist is similar to modern Mn-oxide precipitates and seawater. Differences in δ98Mo signals are broadly reflected in cerium (Ce) anomalies, which suggest an oxic–anoxic-stratified Palaeoproterozoic ocean.

Transport and Retention of Molybdenum(VI) in Soils: Kinetic Modeling

Core Ideas Mo(VI) sorption was kinetically controlled and highly nonlinear in two different soils. Mo(VI) retention mechanism in Windsor sand was different from Webster loam. Rate‐limited processes greatly influenced Mo(VI) transport in soils. Mo(VI) transport was well described using a second‐order model. Understanding the mechanisms and kinetics controlling the retention and transport of molybdenum [Mo(VI)] is a prerequisite in the effort to evaluate environmental risk of groundwater contamination. In this study, kinetic batch and miscible‐displacement experiments were performed to investigate Mo(VI) adsorption–desorption and transport behaviors on a neutral soil (Webster loam) and a slightly acidic soil (Windsor sand). Batch results indicated that adsorption of Mo(VI) was kinetically controlled and highly nonlinear in both soils. The Mo(VI) maximum adsorption and kinetic rate for acidic Windsor sand was much higher than for neutral Webster loam. Mo(VI) breakthrough curves (BTCs) were asymmetrical and exhibited extensive tailing with incomplete recovery in the effluent: these features demonstrate that rate‐limited or non‐equilibrium process influenced Mo(VI) transport behavior. To better understand the controls on the nonlinear kinetic behavior of Mo transport in these soils, a second‐order (SO) model which accounts for equilibrium, reversible, and irreversible retention mechanisms was used to describe Mo(VI) retention and transport in soils. Based on optimized and predictive modeling results, a fully reversible equilibrium‐kinetic SO model successfully described the time‐dependent Mo(VI) sorption for Webster loam. However, for Windsor sand, which exhibited strong affinity and low mobility for Mo(VI), an additional consecutive irreversible reaction phase was necessary to describe Mo(VI) retention and transport with time.

Kinetics of Molybdenum Adsorption and Desorption in Soils.

Much uncertainty exists in mechanisms and kinetics controlling the adsorption and desorption of molybdenum (Mo) in the soil environment. To investigate the characteristics of Mo adsorption and desorption and predict Mo behavior in the vadose zone, kinetic batch experiments were performed using three soils: Webster loam, Windsor sand and Mahan sand. Adsorption isotherms for Mo were strongly nonlinear for all three soils. Strong kinetic adsorption of Mo by all soils was also observed, where the rate of retention was rapid initially and was followed by slow retention behavior with time. The time-dependent Mo sorption rate was not influenced when constant pH was maintained. Desorption or release results indicated that there were significant fractions of Mo that appeared to be irreversible or slowly reversibly sorbed by Windsor and Mahan. X-ray absorption near edge structure (XANES) analysis for Windsor and Mahan soils indicated that most of Mo had been bound to kaolinite, whereas Webster had similar XANES features to those of Mo sorbed to montmorillonite. A sequential extraction procedure provided evidence that a significant amount of Mo was irreversibly sorbed. A multireaction model (MRM) with nonlinear equilibrium and kinetic sorption parameters was used to describe the adsorption-desorption kinetics of Mo on soils. Our results demonstrated that a formulation of MRM with two sorption sites (equilibrium and reversible) successfully described Mo adsorption-desorption data for Webster loam, and an additional irreversible reaction phase was recommended to describe Mo desorption or release with time for Windsor and Mahan soils.

Low‐cost biosorbent based on Moringa oleifera residues for herbicide atrazine removal in a fixed‐bed column

AbstractA low‐cost biosorbent based on Moringa oleifera Lam (MO) seed husks was used in order to remove atrazine (ATZ) from aqueous solutions in a continuous system. The influence of some parameters, such as bed depth, flow rate, pH, and inlet concentration, on ATZ biosorption was investigated. The breakthrough and saturation time increased with the increase of bed depth. However, the opposite behaviour was observed for the flow rate. The sorption capacity, breakthrough, and saturation time were similar at all values of pH tested. Increasing the inlet concentration, the MO sorption capacity also increased, while the breakthrough and saturation time decreased. The Adams‐Bohart, Thomas, dose‐response, and Yoon‐Nelson models were applied to predict the breakthrough curves. All models showed good agreement with the experimental data, presenting good values of the correlation coefficient (R2). The results showed that MO seed husks can be effectively used as a biosorbent to remove the atrazine in aqueous solutions, achieving five cycles of biosorption‐desorption without loss of biosorption capacity, which demonstrates the potential of MO as a biosorbent for the removal of ATZ being a low‐cost and efficient alternative to the use of conventional materials.

Influence of pH of Nitric Acid Solution on the Kinetics of the 99Мо Sorption onto Titanium Hydroxide

The kinetics of the 99Мо sorption onto T-5 sorbent at different pH values of the nitric acid solution was studied. The previously suggested limiting steps of the 99Мо sorption onto Т-5 sorbent were confirmed. The effective rate constant of the molybdenum sorption onto titanium hydroxide (fast step) as a function of pH passes through a maximum at pH from 4.5 to 5.5, which does not correspond to the maximum of the pH dependence of the distribution coefficient but correlates with the maximal content of one of the sorbable species, НМоО4–, in the solution. Thus, the rate of Mo sorption onto titanium hydroxide as a function of pH passes through a maximum at a minimal negative charge of the sorbate near pH of the isoelectric point of the sorbent. The kinetic studies confirm the scheme of the sorption of molybdenum hydroxo complexes onto titanium hydroxide, suggested previously on the basis of the logkd–рН and log e–log[m] sorption isotherms. According to this scheme, simultaneous redistribution and sorption of sorbable molybdenum species, МоО2ОН+, Н2МоО4, and НМоО4–, are possible.

PURITY UPGRADE OF AMMONIUM PERRHENATE SOLUTIONS IN RESPECT OF MOLYBDENUM (VI) AT SORPTION RECOVERY OF RHENIUM (VII) FROM SOLUTIONS CONTAINING MOLYBDENUM (VI)

The study covers the method of additional cleaning of ammonium perrhenate desorbates from molybdenum through sorption recovery of rhenium from Mo-containing solutions with Purolite A170 and A172 weak base anion exchange resins. The dependence of Re(VII) and Mo(VI) sorption using these resins on solution pH was studied under static conditions with the 1 M (NH 4 ) 2 SO 4 solution. It was found that the pH range at which the resins retain the ability of Re(VII) sorption extends to a weak-alkaline area. A significant decrease in Re(VII) adsorption begins when pH exceeds 7,5 Mo(VI) capacity of the resins decreases significantly when solution pH exceeds 5,0, and both anion exchange resins practically stop molybdenum sorption at above pH ~ 7,0. Reduction of Mo(VI) content in rhenium desorbates obtained in sorption recovery of Re(VII) from Mo-containing solutions with weak base anion exchange resins can be achieved as follows. First, major quantity of adsorbed Mo(VI) is desorbed from the loaded resin by ammonium sulfate solution when stirring the mixture and keeping pH constant in the 7,0–7,5 range by dosing the ammonia solution. Then the resin is separated from the Mo(VI)-containing ammonia solution, washed with water, and Re(VII) is desorbed by the ammonia solution in dynamic conditions. The proposed method was verified with anion exchangers loaded in sorption from the model solution with the following composition, g/L: 98 H 2 SO 4 , 4 Mo(VI), 0,5 Re(VII). It was shown that resin treatment with the ammonium sulfate solution removes at least 90 % of adsorbed molybdenum. A ratio of Re(VII) to Mo(VI) concentrations in ammonium perrhenate desorbates increases by 11 times with Purolite A170 resin, and by 20 times with Purolite A172 resin compared to the results obtained without an additional Mo(VI) washing. Re(VII) losses (reversible) with the Mo-containing desorbate are below 5,2 % of the adsorbed Re(VII) amount.

Kinetics of 99Мо sorption onto a sorbent based on hydrated titanium dioxide

The kinetics of 99Мо sorption onto T-5 sorbent in the batch mode at different values of the stirring rate, temperature, and sorbent granule size was studied. All the experimental kinetic curves are described by a sum of two exponents. In the first time interval of phase contact, from 0 to 5–10 min, the sorption is controlled by external diffusion, and in the interval from 10 to 40 min the step of transformation of unsorbable Mo species into sorbable hydroxo species also becomes a rate-determining step (external kinetic control). In the final stage (time interval from 40 min to 2–3 h), the sorption occurs at the lowest rate, and the Mo diffusion in micropores and overcoming of electrostatic hindrance on the surface of titanium hydroxide pores become the most probable limiting steps. In sulfate solutions, the Mo sorption rate considerably decreases already in the first stage, and the external kinetic control becomes prevalent because of hindered redistribution of unsorbable sulfate complexes into sorbable hydroxo complexes. The controlling factor in the sulfate and nitrate solutions in the second stage is presumably the same.

Recovery of molybdenum oxyanions using macroporous copolymer grafted with diethylenetriamine

The presented study describes macroporous crosslinked poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) [PGME] functionalized with diethylenetriamine [PGME-deta] as a potential recovery agent for Mo(VI) oxyanions from aqueous solutions. Sorption studies were carried out by varying experimental conditions (pH, time, concentration, temperature). Kinetics of Mo(VI) sorption was investigated in batch (static) experiments, in the temperature range 298–343K. Sorption dynamics data were fitted to seven chemical-reaction and particle-diffusion models. The kinetics studies showed that Mo(VI) sorption adhered to the pseudo-second-order model under all investigated operating conditions. The sorption kinetics was determined to be governed by both the intraparticle diffusion and the external film diffusion to a lesser extent. The temperature rise promotes the molybdate species removal, with the maximum experimental uptake capacity of 4.02mmolg−1 at 298K, at the selected pH which is consistent with the predominance range of hydrolized polynuclear Mo(VI) forms and optimum electrostatic attraction.

Acidic phosphoryl podands as components of impregnation-type sorbents for 99Mo recovery from nitric acid solutions

A series of phosphoryl podands of acid type, differing in the length of the polyether chain and structure of the terminal group, were synthesized. The compounds obtained were tested as complexing components of impregnation-type sorbents. The regular trends of the Mo sorption from model solutions of ammonium molybdate in HNO3 in relation to the qualitative and quantitative composition of the sorbents were studied by extraction chromatography. The composition of a new impregnation-type complexing sorbent for selective recovery of Mo from nitric acid solutions was developed and optimized, and conditions were determined for its practical use. The sorbent allows efficient recovery of 99Mo and its separation from products of reprocessing of irradiated uranium materials in process solutions of the Mayak Production Association. The sorbent also allows separation of 99Mo and 99mTc, which makes it potentially suitable for use in 99Mo/99mTc generators of chromatographic type.

Novel imino diacetamide styrene divinyl benzene resin for separation of99molybdenum from irradiated uranium–aluminium alloy

Imino diacetamide styrene divinyl benzene (IDAA SDVB) resin was synthesized and evaluated for separation of molybdenum (Mo) from simulated dissolver solution of irradiated uranium–aluminium alloy. Detailed studies were carried out to understand the influence of various parameters on sorption of Mo. The kinetics of Mo sorption is found to be fast and the kinetics data fit well to the pseudo-second order kinetic equation. Sorption of Mo is found to decrease with the increase of feed acidity. The loading capacity of resin is determined to be 30 mg g−1, the sorption isotherm data fit well to the Langmuir model. Batch sorption experiments with simulated dissolver solution showed quantitative uptake of Mo along with some co-extraction of iodine (I). Column runs have demonstrated that co-extracted ‘I’ could be scrubbed easily with solutions of feed acidity. Finally, sorbed Mo could be eluted with 3.0 M HNO3. XAFS and FT-IR studies of Mo sorbed on to IDAA SDVB resin have shown that Mo is sorbed in the +6 oxidation state (in the form of MoO42−), wherein the complex attains octahedral geometry with contribution from four oxygen atoms of the molybdate anion and two oxygen atoms of the amidic moiety of the imino-diacetamide ligand.

Evidence for free oxygen in the Neoarchean ocean based on coupled iron–molybdenum isotope fractionation

Most geochemical proxies and models of atmospheric evolution suggest that the amount of free O2 in Earth’s atmosphere stayed below 10−5 present atmospheric level (PAL) until the Great Oxidation Event (GOE) that occurred between ∼2.2 and 2.4Ga, at which time free O2 in the atmosphere increased to approximately 10−1 to 10−2 PAL. Although photosynthetically produced “O2 oases” have been proposed for the photic zone of the oceans prior to the GOE, it has been difficult to constrain absolute O2 concentrations and fluxes in such paleoenvironments. Here we constrain free O2 levels in the photic zone of a Late Archean marine basin by the combined use of Fe and Mo isotope systematics of Ca–Mg carbonates and shales from the 2.68 to 2.50Ga Campbellrand–Malmani carbonate platform of the Kaapvaal Craton in South Africa. Correlated Fe and Mo isotope compositions require a key role for Fe oxide precipitation via oxidation of aqueous Fe(II) by photosynthetically-derived O2, followed by sorption of aqueous Mo to the newly formed Fe oxides. A dispersion/reaction model illustrates the effects of Fe oxide production and Mo sorption to Fe oxides, and suggests that a few to a few tens of μM free O2 was available in the photic zone of the Late Archean marine basin, consistent with some previous estimates. The coupling of Fe and Mo isotope systematics provides a unique view into the processes that occurred in the ancient shallow ocean after production of free O2 began, but prior to oxygenation of the deep ocean, or significant accumulation of free O2 in the atmosphere. These results require oxygenic photosynthesis to have evolved by at least 2.7Ga and suggest that the Neoarchean ocean may have had a different oxygenation history than that of the atmosphere. The data also suggest that the extensive iron formation deposition that occurred during this time was unlikely to have been produced by anoxygenic photosynthetic Fe(II) oxidation. Finally, these data indicate that the ocean had significant amounts of O2 at least 150Myr prior to previously proposed “whiffs” of O2 at the Archean to Proterozoic transition.

Transport of molybdenum in a biosolid-amended alkaline soil

The transport of molybdenum (Mo) in a biosolid-amended, alkaline, agricultural soil was examined in the research reported herein. Batch-equilibrium and miscible-displacement experiments were conducted to examine the transport of Mo in soil with and without 10% by weight biosolid amendment. The results of geochemical modeling, conducted using PHREEQC, indicated that no mineral dissolution or precipitation reactions were expected for the system under the prevailing conditions. Sorption equilibrium coefficients ( K d ) obtained from moment analysis of the Mo breakthrough curves were similar to those calculated from the results of the batch-equilibrium experiments. Mo sorption was greater for the biosolid-amended soil ( K d of 1.3 versus 0.35). Sorption of Mo was shown to be linear, rate limited, and reversible for both unamended and amended soil. The results suggest that Mo associated with biosolid-amended soils is relatively bioavailable and mobile.

Sorption of Molybdenum(VI) on Synthetic Magnetite

ABSTRACTIn this study we experimentally investigated the interaction of Mo(VI) with magnetite, which is a corrosion product of steel. The work was conducted with commercial magnetite, and we studied the influence of pH, pe and solid/liquid ratio on Mo sorption. A Surface Complexation Model (SCM) has been applied tothe experimental data, allowing to explain the results using the Diffuse Layer Model (DLM) and by considering the formation of the monodentate complex: &gt;FeOMo(OH)5. At pH 2, experimental data were satisfactorily fitted to a a Langmuir isotherm.