Rate Of Ion Uptake Research Articles

The mayfly Neocloeon triangulifer senses decreasing oxygen availability (PO2) and responds by reducing ion uptake and altering gene expression.

Oxygen availability is central to the energetic budget of aquatic animals and may vary naturally and/or in response to anthropogenic activities. Yet, we know little about how oxygen availability is linked to fundamental processes such as ion transport in aquatic insects. We hypothesized and observed that ion (22Na and 35SO4) uptake would be significantly decreased at O2 partial pressures below the mean Pcrit (5.4 kPa) where metabolic rates (MO2) are compromised, and ATP production is limited. However, we were surprised to observe marked reductions in ion uptake at oxygen partial pressures well above the Pcrit, where MO2 was stable. For example, SO4 uptake decreased by 51% at 11.7kPa, and 82% at the Pcrit (5.4kPa) while Na uptake decreased by 19% at 11.7kPa, and 60% at the Pcrit. Nymphs held for longer time periods at reduced PO2 exhibited stronger reductions in ion uptake rates. Fluids from whole body homogenates exhibited a 29% decrease in osmolality in the most hypoxic condition. The differential expression of atypical guanylyl cyclase (gcy-88e) in response to changing PO2 conditions provides evidence for its potential role as an oxygen sensor. Several ion transport genes (e.g., chloride channel and sodium-potassium ATPase) and hypoxia-associated genes (e.g., ldh and egl-9) were also impacted by decreased oxygen availability. Together, our work suggests that N. triangulifer can sense decreased oxygen availability and perhaps conserves energy accordingly, even when MO2 is not impacted.

Exclusão de Na+ e acúmulo de prolina em cultivares de Urochloa spp.

Abstract The objective of this work was to evaluate the effect of salinity on Na+ and K+ distribution and on proline content in Urochloa brizantha and Urochloa decumbens grass cultivars. Plants were grown in nutrient solution and subjected to salt stress for nine days. Shoot and root lengths and proline, total chlorophyll, K+, and Na+ contents were determined. Salt stress reduced the shoot length of cultivar Marandu but not of Xaraés and Basilisk. Total chlorophyll content was not affected by salinity in U. brizantha cultivars, but increased in cultivar Basilisk of U. decumbens. Salt-induced proline accumulation was observed in all cultivars, with a higher increase in Marandu. The K+ content in leaf blades increased in the Marandu and Basilisk cultivars under salinity conditions. 'Basilisk' showed Na+ exclusion in shoot tissues, whereas 'Marandu' and 'Piatã', followed by 'Xaraés', exhibited a higher Na+ in leaf blades. The pattern of ion distribution among cultivars was attributed mainly to differences in the ability to control the ion transport from root to shoot, since the rates of ion uptake were similarly affected by salinity. Tolerance to salt stress in grasses of the Urochloa genus is associated to Na+ exclusion and not to proline accumulation in shoot tissues.

Effects of film thickness on electrochemical properties of nanoscale polyethylenedioxythiophene (PEDOT) thin films grown by oxidative molecular layer deposition (oMLD).

Poly(3,4-ethylene dioxythiophene) (PEDOT) has a high theoretical charge storage capacity, making it of interest for electrochemical applications including energy storage and water desalination. Nanoscale thin films of PEDOT are particularly attractive for these applications to enable faster charging. Recent work has demonstrated that nanoscale thin films of PEDOT can be formed using sequential gas-phase exposures via oxidative molecular layer deposition, or oMLD, which provides advantages in conformality and uniformity on high aspect ratio substrates over other deposition techniques. But to date, the electrochemical properties of these oMLD PEDOT thin films have not been well-characterized. In this work, we examine the electrochemical properties of 5-100 nm thick PEDOT films formed using 20-175 oMLD deposition cycles. We find that film thickness of oMLD PEDOT films affects the orientation of ordered domains leading to a substantial change in charge storage capacity. Interestingly, we observe a minimum in charge storage capacity for an oMLD PEDOT film thickness of ∼30 nm (60 oMLD cycles at 150 °C), coinciding with the highest degree of face-on oriented PEDOT domains as measured using grazing incidence wide angle X-ray scattering (GIWAXS). Thinner and thicker oMLD PEDOT films exhibit higher fractions of oblique (off-angle) orientations and corresponding increases in charge capacity of up to 120 mA h g-1. Electrochemical measurements suggest that higher charge capacity in films with mixed domain orientation arise from the facile transport of ions from the liquid electrolyte into the PEDOT layer. Greater exposure of the electrolyte to PEDOT domain edges is posited to facilitate faster ion transport in these mixed domain films. These insights will inform future design of PEDOT coated high-aspect ratio structures for electrochemical energy storage and water treatment.

Nanogravimetric Monitoring of Electrochemically Driven Fluoride Ion Extraction from Water By Aniline-Based Copolymer Films

Sustainable access to safe drinking water is a global societal goal [1]. Accordingly, much attention has been given to the development of technologies for remediation of the unintended effects of agricultural practices and industrial processes. The case of fluoride in water is an interesting case in two respects: its desirability up to a point and its natural origins. The beneficial effects of fluoride on dental health are recognized: in some countries drinking water is routinely fluoridated. However, high levels of fluoride can have detrimental effects on teeth, bones and internal organs; the recommended upper limit is 1.5 mg/L. The fluoride concentration in natural waters - the source of most drinking water - is dictated by the presence of calcium ions, through the solubility product of calcium fluoride. Dependent on the local geology, the calcium ion concentration may be relatively low or high, such that either the beneficial effects of fluoride may not be realized or its injurious effects may dominate. Determination of fluoride concentration using ion selective electrodes is well-established. The question then is how to remedy high fluoride levels. Existing methods for removal of excess fluoride from drinking water and wastewater include precipitation (as Ca or Al salts), membrane technologies and adsorption. Each of these has limitations, e.g. high costs, toxic by-products and slow or complex processes.Here we explore electrochemically controlled fluoride ion extraction by electroactive polymer films. This approach has been studied for water softening (using polypyrrole [2]) and perchlorate removal (using polypyrrole composites [3] and polyaniline-based copolymers [4]). Here we explore the feasibility of using a range of polyaniline-based materials in an electrochemically switched ion exchange system for fluoride removal from water [5]. The concept is based on F- ion uptake as counter ions in the oxidation (p-doping) of the conducting polymer film. Upon oxidation, the film will “capture” F- ions from solution. After separation of the purified water, the F- ions would then be ejected into a concentrated waste stream by reduction (un-doping) of the oxidized polymer.In this presentation we compare the characteristics and performance of polyaniline, poly(o-aminophenol) and poly(o-toluidine) homopolymer films with each other and with those of their copolymers of various composition. Film deposition is controlled electrochemically and monitored nanogravimetrically using the EQCM. Acoustic impedance enables distinction between gravimetric and viscoelastic interpretation of the response [8]. The extent of redox-driven fluoride uptake is then determined upon exposure to solutions of varying fluoride (and in some cases chloride) concentration. Correlation of EQCM-derived film mass and charge responses is used to assay fluoride and solvent uptake during film oxidation and reduction. Comparison with the total redox site population (from the response in fluoride-free media) yields the efficiency. Observations for these aniline-based homopolymers and copolymers reveal behavior that is quite different to that seen for typical small anionic dopants, such as chloride, nitrate and perchlorate. Further, there are surprisingly diverse responses to fluoride for these relatively similar polymeric materials, notably the extent of film solvation change during fluoride uptake. Use of different electrochemical control functions and timescales reveals differences in fluoride ion uptake and release rates. The relevance of these data to defluoridation will be discussed.

Removal of nickel from aqueous solution by using corncob as adsorbent

Heavy metal deposition in the environment is increasing day by day as a result of the rapid growth of the industrial sector and massive anthropogenic activities. Among numerous heavy metals, nickel is the 5th greatest copious component on the planet. Though numerous conventional treatments are available to remediate nickel-contaminated water, including electrochemistry, precipitation, flocculation, ion exchange, coagulation, membrane filtration, and adsorption, each has some or all of the following drawbacks in terms of cost and efficiency in removing metal ions from water. Among all methods, the adsorption method was found to be the most cost-effective and efficient at removing metal ions from water. Adsorption is a highly efficient and cost-effective method of extracting nickel ions from water that involves surface phenomena. The primary goal of this paper is to identify the indigenous adsorbent for a batch study in extracting nickel ions from an aqueous solution. Corncob is used as a low-cost agro-based adsorbent in this study to remove nickel ions from an aqueous medium. Under batch methodology, the effect of several major adsorption operating parameters has been considered and optimized. It was discovered that the optimum adsorbent dose was 1.5 g/50 ml, that equilibrium was achieved in 120 min, and that better adsorption at pH 8 was obtained. Freundlich, Langmuir, and Temkin isotherm models were used to correlate sorption data. The result demonstrates that the Langmuir adsorption model fits best when compared to other adsorption isotherm models, with R2 = 0.9781 and adsorption capacity, Q0 = 0.0517 mg/g. Adsorption kinetics are discussed to investigate the rate of nickel ion uptake on the adsorbent. A kinetic study revealed that the pseudo-second-order model was better fitted than pseudo-first-order, with R2 = 0.9999.

Inorganic nitrogen uptake rate of Picea asperata curtailed by fine root acclimation to water and nitrogen supply and further by ectomycorrhizae.

Ectomycorrhizal (ECM) fungi colonization and function depend on soil water and nutrient supply. To study the effects of resource supply on ECM colonization and inorganic nitrogen (N) uptake by roots of Picea asperata seedlings, we conducted a study at the end of a 5-year long experiment consisting of five watering regimes (40, 50, 60, 80, and 100% of field capacity) and three NH4 NO3 application rates (0 [N0], 20 [N1], and 40 [N2]g N m-2 year-1 ). We measured fluxes of ammonium ( ) and nitrate ( ) into colonized and uncolonized roots using noninvasive microtest technology. We found that, across the N supply levels, ECM colonization rate increased by 53 ± 14% from the highest to the lowest level of water supply. Across the watering regimes, the fraction of mycorrhizal root tips was 39 ± 4% higher under native N supply compared to roots grown under N additions. As expected for conifers, both colonized and uncolonized roots absorbed at a higher rate than . N additions reduced the instantaneous ion uptake rates of uncolonized roots grown under low water supply but enhanced the fluxes into roots grown under sufficient soil water availability. Soil water supply improves inorganic N uptake by uncolonized roots but reduces the efficiency of colonized roots. Under the lowest water supply regime, the uptake rate of and by colonized roots was 40-80% of those by uncolonized roots, decreasing to 20-30% as soil water supply improved. Taken together, our results suggest that the role ectomycorrhizae play in the nutrient acquisition of P. asperata seedling likely diminishes with increasing availability of soil resources.

Physiological plasticity and acclimatory responses to salinity stress are ion-specific in the mayfly, Neocloeon triangulifer

Freshwater salinization is a rapidly emerging ecological issue and is correlated with significant declines in aquatic biodiversity. It remains unclear how changing salinity regimes affect the physiology of sensitive aquatic insects. We used the parthenogenetic mayfly, Neocloeon triangulifer, to ask how ionic exposure history alters physiological processes and responses to subsequent major ion exposures. Using radiotracers (22Na, 35SO4, and 45Ca), we observed that mayflies chronically reared in elevated sodium or sulfate (157 mg L−1 Na or 667 mg L−1 SO4) had 2-fold (p < 0.0001) and 8-fold (p < 0.0001) lower ion uptake rates than mayflies reared in dilute control water (16 mg L−1 Na and 23 mg L−1 SO4) and subsequently transferred to elevated salinities, respectively. These acclimatory ion transport changes provided protection in 96-h toxicity bioassays for sodium, but not sulfate. Interestingly, calcium uptake was uniformly much lower and minimally influenced by exposure history, but was poorly tolerated in the toxicity bioassays. With qRT-PCR, we observed that the expression of many ion transporter genes in mayflies was influenced by elevated salinity in an ion-specific manner (general upregulation in response to sulfate, downregulation in response to calcium). Elevated sodium exposure had minimal influence on the same genes. Finally, we provide novel light microscopic evidence of histomorphological changes within the epithelium of the Malpighian tubules (insect primary excretory system) that undergoes cellular degeneration and necrosis secondary to calcium toxicity. We conclude that physiological plasticity to salinity stress is ion-specific and provide evidence for ion-specific toxicity mechanisms in N. triangulifer.

Calix[4]trap: A Bioinspired Host Equipped with Dual Selection Mechanisms.

Regulation of recognition events evolving in time and space is vital for living organisms. During evolution, organisms have developed distinct and orthogonal mechanisms to achieve selective recognition, avoiding mutual interference. Although the merging of multiple selection mechanisms into a single artificial host may lead to a more adaptable recognition system with unparalleled selectivity, successful implementation of this strategy is rare. Inspired by the intriguing structures and recognition properties of two well-known biological ion binders-valinomycin and K+ channels-we herein report a series of hosts equipped with dual guest selection mechanisms. These hosts simultaneously possess a preorganized binding cavity and a confined ion translocation tunnel, which are crucial to the record-setting K+/Na+ selectivity and versatile capabilities to discriminate against a wide range of ion pairs, such as K+/Rb+, K+/Ba2+, and Rb+/Cs+. Mechanistic studies verify that the host's portal is capable of discriminating cations by their size, enabling varied ion uptake rates. The confined tunnel bearing consecutive binding sites promotes complete desolvation of ions during their inclusion into the buried cavity, mimicking the ion translocation within ion channels. Our results demonstrate that the capability to manipulate guest recognition both in equilibrium and out-of-equilibrium states allows the host to effectively discriminate diverse guests via distinct mechanisms. The strategy to merge orthogonal selection mechanisms paves a new avenue to creating more robust hosts that may function in complex biological environments where many recognition events occur concurrently.

The efficient recovery of Au(III) ions from acidic solutions by a novel scavenger based on functionalized poly(styrene-co-maleimide) nanoparticles

Tertiary amine functionalized poly(styrene-co-maleimide) nanoparticles were readily synthesized by an organic solvent-free thermal imidization reaction. The obtained spherical nanoparticles, with average diameters of about 50 nm, were shown to be highly effective as a unique scavenger for the recovery of Au(III) ions from strong acidic solution. High equilibrium Au loading capacities (>570 mg/g) were obtained at 25 °C and the rate of metal ion uptake was remarkably fast. The Au(III) ions in the feed solutions were almost quantitatively recovered within 3–10 min, depending on the shaking speed during batch sorption. Elution of the adsorbed Au species was however incomplete with a maximum elution efficiency of 75% using acidified thiourea as eluant. XPS analysis showed that the adsorbed Au species were present as a mixture of Au(0), Au(I), and Au(III), which explained the inadequate elution. An alternative and innovative method to recover the adsorbed Au was developed consisting of digestion of the Au-loaded scavenger followed by reductive precipitation with water as reducing agent. The Au formerly loaded on the scavenger was successfully and completely recuperated as pure metallic Au. This is a step-change in the way Au is recovered from solution and eliminates the need for difficult, partial, and environmentally unfavorable elution processes of Au species strongly adsorbed on the scavenger particles.

Phosphate Removal Using Polyethylenimine Functionalized Silica-Based Materials

In water and wastewater, phosphate anions are considered critical contaminants because they cause algae blooms and eutrophication. The present work aims at studying the removal of phosphate anions from aqueous solutions using silica particles functionalized with polyethylenimine. The parameters affecting the adsorption process such as pH, initial concentration, adsorbent dose, and the presence of competitive anions, such as carbonate, nitrate, sulfate and chromate ions, were studied. Equilibrium studies were carried out to determine their sorption capacity and the rate of phosphate ions uptake. The adsorption isotherm data fitted well with the Langmuir and Sips model. The maximum sorption capacity was 41.1 mg/g at pH 5, which decreased slightly at pH 7. The efficiency of phosphate removal adsorption increased at lower pH values and by increasing the adsorbent dose. The maximum phosphate removal was 80% for pH 5 and decreased to 75% for pH 6, to 73% for pH 7 and to 70% for pH 8, for initial phosphate concentration at about 1 mg/L and for a dose of adsorbent 100 mg/L. The removal rate was increased with the increase of the adsorbent dose. For example, for initial phosphate concentration of 4 mg/L the removal rate increased from 40% to 80% by increasing the dose from 0.1 to 2.0 g/L at pH 7. The competitive anions adversely affected phosphate removal. Though they were also found to be removed to a certain extent. Their co-removal provided an adsorbent which might be very useful for treating waters with low-level multiple contaminant occurrence in natural or engineered aquatic systems.

An electroactive montmorillonite/polyaniline nanocomposite film: Superfast ion transport and ultra-affinity ion recognition for rapid and selective separation of Pb2+ ions

Although a variety of functional materials have been developed for the separation target ions, most of them suffer from sluggish uptake of ions and deficient selectivity. Herein, a nanocomposite electroactive film with a sandwich-like structure was facilely prepared by intercalating conductive polyaniline (PANI) into the interlayer of montmorillonite (MMT) with layered structure for rapid and selective separation of Pb2+ ions. This MMT/PANI nanocomposite film exhibited an extreme Pb2+ ion uptake rate (1422.67 μg∙(g∙s)−1), which exceeded those of conventional adsorbents by 2 to 4 orders of magnitude. Meanwhile, trace Pb2+ ions at ppb level in the wastewater were quantitatively detected by employing the MMT/PANI nanocomposite electroactive film based on its strong affinity towards Pb2+ ions. It was confirmed that the rapid and selective Pb2+ ion uptake/release by the MMT/PANI composite film was achieved via the directional proton migration powered by the electrochemical redox of the intercalated PANI, the superfast ion transport in atomically interlamellar ion transport path and the ultra-affinity ion recognition of ion capture sites on MMT layer. It is expected that such an MMT/PANI composite film could be a promising alternative of conventional materials for separating and detecting of Pb2+ ions in wastewater.

Use of a carbonic anhydrase Ca17a knockout to investigate mechanisms of ion uptake in zebrafish (Danio rerio).

In fishes, branchial cytosolic carbonic anhydrase (CA) plays an important role in ion and acid-base regulation. The Ca17a isoform in zebrafish (Danio rerio) is expressed abundantly in Na+-absorbing/H+-secreting H+-ATPase-rich (HR) cells. The present study aimed to identify the role of Ca17a in ion and acid-base regulation across life stages using CRISPR/Cas9 gene editing. However, in preliminary experiments, we established that ca17a knockout is lethal with ca17a-/- mutants exhibiting a significant decrease in survival beginning at ∼12 days postfertilization (dpf) and with no individuals surviving past 19 dpf. Based on these findings, we hypothesized that ca17a-/- mutants would display alterations in ion and acid-base balance and that these physiological disturbances might underlie their early demise. Na+ uptake rates were significantly increased by up to 300% in homozygous mutants compared with wild-type individuals at 4 and 9 dpf; however, whole body Na+ content remained constant. While Cl- uptake was significantly reduced in ca17a-/- mutants, Cl- content was unaffected. Reduction of CA activity by Ca17a morpholino knockdown or ethoxzolamide treatments similarly reduced Cl- uptake, implicating Ca17a in the mechanism of Cl- uptake by larval zebrafish. H+ secretion, O2 consumption, CO2 excretion, and ammonia excretion were generally unaltered in ca17a-/- mutants. In conclusion, while the loss of Ca17a caused marked changes in ion uptake rates, providing strong evidence for a Ca17a-dependent Cl- uptake mechanism, the underlying causes of the lethality of this mutation in zebrafish remain unclear.

Early-life stress influences ion balance in developing zebrafish (Danio rerio).

As a key endocrine axis involved in responding to stress, the hypothalamic-pituitary-interrenal axis plays dual roles in mobilizing energy and maintaining ionic/osmotic balance in fishes. Although these roles have been examined independently in detail in adult fishes, less attention has been paid to the effects of an endogenous stress response during early life, particularly with respect to its potential effects on ionic/osmotic balance. The present study tested the hypothesis that exposure of zebrafish to stress during early development would alter ion balance later in life. Zebrafish at three developmental stages (4, 7, or 15days post-fertilization, dpf) were subjected to an air-exposure stressor twice a day for 2days, causing elevation of whole-body cortisol levels. Individuals stressed early in life exhibited decreased survival and growth, altered cortisol responses to a subsequent air-exposure stressor, and increased whole-body Na+ and Ca2+ concentrations. Changes in whole-body Ca2+ concentrations were accompanied by increased ionocyte abundance at 7 dpf and increased rates of Ca2+ uptake from the environment. Differences in whole-body ion concentrations at 15 and 35 dpf were not accompanied by altered ion uptake rates. Across all ages examined, air-exposure stress experienced at 7 dpf was particularly effective at eliciting phenotypic changes, suggesting a critical window at this age for a stress response to influence development. These findings demonstrate that early-life stress in zebrafish triggers developmental plasticity, with age-dependent effects on both the cortisol stress axis and ion balance.

Effect of aluminum loading on structural and morphological characteristics of ZnO nanoparticles for heavy metal ion elimination.

The aim of this work consists on the synthesis of a nanomaterial for heavy metal ion removal from aqueous solutions. Al-doped ZnO (ZnO:Alx%) nanopowders with 0 to 5% Al content are prepared via an amended sol-gel method. The morphology and microstructure of the prepared ZnO:Alx% are probed by means of scanning electron microscopy (SEM), X-ray particles diffraction (XRD) analysis, energy dispersive X-ray spectroscopy (EDS) and elemental mapping. The findings reveal the prevalence of the hexagonal wurtzite ZnO structure with increasing crystallite size (45 to 60nm) as a result of Al doping. SEM images show nearly spherical nanoparticles with considerable aggregation. EDS and elemental mapping analysis confirm the incorporation of Al within ZnO host lattice. The relatively large surface area as estimated from N2 adsorption makes the nanopowders very favorable for the uptake Cd(II), Cr (IV), Co (II) and Ni(II) from aqueous solution. The ZnO:Alx% with 1wt% Al exhibits the highest uptake rate of heavy metal ions. The adsorption process has been found to be spontaneous and endothermic and obey Langmuir adsorption model. The high tendency of the prepared nanoparticles to eliminate heavy metal ions renders them suitable candidates for environmental remediation. Desorption studies with 0.1M NaOH indicate that ZnO:Alx% can be regenerated effectively.

Use of gene knockout to examine serotonergic control of ion uptake in zebrafish reveals the importance of controlling for genetic background: A cautionary tale

Freshwater (FW) fishes inhabit dilute environments and must actively absorb ions in order to counteract diffusive salt loss. Neuroendocrine control of ion uptake in FW fishes is an important feature of ion homeostasis and several important neuroendocrine factors have been identified. The role of serotonin (5-HT), however, has received less attention despite several studies pointing to a role for 5-HT in the control of ion balance. Here, we used a gene knockout approach to elucidate the role of 5-HT in regulating Na+ and Ca2+ uptake rates in larval zebrafish. Tryptophan hydroxylase (TPH) is the rate-limiting step in 5-HT synthesis and we therefore hypothesized that ion uptake rates would be altered in zebrafish larvae carrying knockout mutations in tph genes. We first examined the effect of tph1b knockout (KO) and found that tph1bKO larvae, obtained from Harvard University, had reduced rates of Na+ and Ca2+ uptake compared to wild-type (WT) larvae from our institution (uOttawa WT), lending support to our hypothesis. However, further experiments controlling for differences in genetic background demonstrated that WT larvae from Harvard University (Harvard WT) had lower ion uptake rates than those of uOttawa WT, and that ion uptake rate between Harvard WT and tph1bKO larvae were not significantly different. Therefore, our initial observation that tph1bKO larvae (Harvard source) had reduced ion uptake rates relative to uOttawa WT was a function of genetic background and not of knockout itself. These data provide a cautionary tale of the importance of controlling for genetic background in gene knockout experiments.

Biosorption of Cd(II) Ions from Aqueous Solution Using Chitosan-iso-Vanillin as a Low-Cost Sorbent: Equilibrium, Kinetics, and Thermodynamic Studies

In the current study, the removal of Cd(II) ions from aqueous solution using chitosan-iso-vanillin biosorbent has been investigated. The impacts of pH, exposure time, adsorbent dosage and initial amount of studied ion on the removal process have been carried out using batch experiments. The quantity of residual ions has been estimated via atomic absorption spectrometry. The synthesized biosorbent is characterized using infrared spectroscopy, DTA, and SEM techniques. The maximum sorption of Cd(II) ions is achieved at pH 5. Langmuir isotherm works as the best explanation model for the experimental data with the highest adsorption capacity equal to $$38.31\,\hbox {mg g}^{-1}$$ . Kinetic studies reveal that chemisorption is the rate-determining step, and the results point out fast rates of metal ion uptake with 77% highest percentage achieved after 60 min. Thermodynamics suggest spontaneous and endothermic process with raise in randomness at the solid/solution interface throughout the bio-adsorption of Cd(II) ions onto modified chitosan.

Biosorptive removal of Zn(II) ions by Pongamia oil cake (Pongamia pinnata) in batch and fixed-bed column studies using response surface methodology and artificial neural network

Design of experiment and artificial neural networks (ANN) have been effectively employed to predict the rate of uptake of Zn(II) ions onto defatted pongamia oil cake. Four independent variables such as, pH (2.0–7.0), initial concentration of Zn(II) ions (50–500 mg/L), temperature (30ºC-50 °C), and dosage of biosorbent (1.0–5.0 g/L) were used for the batch mode while the three independent variables viz. flowrate, initial concentration of Zn(II) ions and bed height were employed for the continuous mode. Second-order polynomial equations were then derived to predict the Zn(II) ion uptake rate. The optimum conditions for batch studies was found to be pH: 4.45, metal ion concentration: 462.48 mg/L, dosage: 2.88 g/L, temperature: 303 K and on the other hand the column studies flow rate: 5.59 mL/min, metal ion concentration: 499.3 mg/L and bed height: 14.82 cm. Under these optimal condition, the adsorption capacity was 80.66 mg/g and 66.29 mg/g for batch and column studies, respectively. The same data was fed to train a feed-forward multilayered perceptron, using MATLAB to develop the ANN based model. The predictive capabilities of the two methodologies were compared, by means of the absolute average deviation (AAD) (4.57%), model predictive error (MPE) (4.15%), root mean square error (RMSE) (3.19), standard error of prediction (SEP) (4.23) and correlation coefficient (R) (0.99) for ANN and for RSM AAD (16.27%), MPE (21,25%), RMSE (13.15%), SEP and R (0.96) by validation data. The findings suggested that compared to the prediction ability of RSM model, the properly trained ANN model has better prediction ability. In batch studies, equilibrium data was used to determine the isotherm constants and first and second order rate constants. In column, bed depth service time (BDST) and Thomas model was used to fit the obtained column data.

Investigation on effects of ion exchangers structure and functional groups on the Re(VII) ions adsorption behavior from aqueous solution

ABSTRACTAlteration adsorption properties of Re(VII) on two resins with different functional groups and structure, weak base/macroporous and strong base/gel type, Purolite A170 (A170) and Dowex 21K (21K) respectively, were investigated experimentally and interpreted by isotherm, kinetic and thermodynamic modeling. Following the comparison of coefficient of determination values, the Freundlich and D-R isotherm models were found to be more suitable for description of investigated systems (R2 > 0.99). The Langmuir isotherm capacities (qm) were indicated that the perrhenate ions (ReO4−) adsorption is higher for weak base/macroporous type resin rather than the other at pH 3 in the presence of 50–250 mg L−1 Re (166.67 and 142.86 mg g−1, respectively). Also, the results from EDX studies corroborated this phenomenon. The adsorption reaction on both adsorbents was found to be chemically with mean free energy, E, as 12.18 and 13.62 kJ mol−1 for A170 and 21K, respectively. Kinetics of adsorption was studied by fitting the data into different mechanisms, among which the pseudo-second order mechanism was found successful for both used resins, but in case of 21K, the rate of perrhenate ions uptake was more rapid than A170. That is possibly attributed to the presence of strong base (quaternary amine) in functional groups. ΔG values obtained were all negative for both resins indicating a spontaneous adsorption process. The positive values of both ΔH (3.34 kJ mol−1) and ΔS (27.31 J mol−1 K−1) obtained suggest an endothermic reaction and in increase in randomness at the solid–liquid interface during the adsorption onto the A170 resin while for 21K, the negative changes in enthalpy and entropy provide an indication that the process is endothermic as well as it follows associative mechanism.

Evaluation of uptake rate and distribution of nutrient ions in wheat (Triticum aestivum L.) under waterlogging condition

Waterlogging is an important factor which is influence on nutrient uptake. Therefore, in this study, the uptake and distribution of nutrients ions in different parts of plant were investigted in wheat cultivars. This study was conducted at the Agricultural Research Station, Islamic Azad University- Ahvaz Branch. Experimental design was a factorial according to randomized complete block design (RCBD) with three replications. In this experiment three wheat cultivars namely “Chamran”, “Dez” and “Verry/nac” were used. These were grown under no-waterlogging (control), 7 days and 14 days of waterlogging. Meanwhile, waterlogging treatments for each cultivar were given separately at three different growth stages namely at the beginning of tillering stage, at the beginning of stem elongation stage and at the commencement of booting stage. The results showed that the concentration of N, K, Fe, Mn, Cu and Zn in root, stem and seed did not affect when waterlogging was applied at different growth stages, significantly. Duration of waterlogging significantly decreased concentration of N, K, Cu and Zn in all parts of plant. The concentration of Fe and Mn in the root increased significantly after duration of waterlogging, but decreased in stem and seed. Results also showed a significant difference between tested wheat cultivars for concentration of N, K, Fe, Mn, Cu and Zn in all parts of plant.

Kinetic Studies on the Removal of Some Lanthanide Ions from Aqueous Solutions Using Amidoxime-Hydroxamic Acid Polymer.

Lanthanide metal ions make distinctive and essential contributions to recent global proficiency. Extraction and reuse of these ions is of immense significance especially when the supply is restricted. In light of sorption technology, poly(amidoxime-hydroxamic) acid sorbents are synthesized and utilized for the removal of various lanthanide ions (La3+, Nd3+, Sm3+, Gd3+, and Tb3+) from aqueous solutions. The sorption speed of trivalent lanthanides (Ln3+) depending on the contact period is studied by a batch equilibrium method. The results reveal fast rates of metal ion uptake with highest percentage being achieved after 15–30 min. The interaction of poly(amidoxime-hydroxamic) acid sorbent with Ln3+ ions follows the pseudo-second-order kinetic model with a correlation coefficient R2 extremely high and close to unity. Intraparticle diffusion data provide three linear plots indicating that the sorption process is affected by two or more steps, and the intraparticle diffusion rate constants are raised among reduction of ionic radius of the studied lanthanides.