Ternary and quaternary ion-exchange equilibria have been studied between heavy metal solution (Pb
2+, Cd
2+, Cu
2+) and Na-form of clinoptilolite. The value of the ion-exchange equilibrium constant ...was estimated using the Langmuir, Competitive Langmuir, and thermodynamic sorption models. For each isotherm, calculations were done taking into account the concentration of ions in both phases. Additionally, for the thermodynamic isotherm, two other cases were considered: activity of ions in the liquid phase and concentration in the solid phase; activity of ions in both phases. The activity coefficients of ions in the liquid phase were determined using Pitzer's model; activity coefficients in the solid phase were estimated by Wilson's model. It was found that the exchange capacity for a given M
2+ is not constant and differs in one- or multi-component systems. The results show that the equilibrium model based on the law of mass action, which considers nonideal behavior of both phases, allows one to achieve the best approach to the real multi-component equilibrium data in all studied systems.
The removal of uranium anionic species from aqueous solutions (initial concentration: 10–2,000 mg/L) by a low- and a high molecular weight polyethylenimine–epichlorohydrin resins was studied in the ...absence of background electrolytes at initial pH (pH
init
) 8 to10. The amount of the sorbed U was determined spectrophotometrically using the Arsenazo III method. The maximum uptake was observed at pH
init
8 using both resins. The maximum uptake capacity observed was 221 and 388 mg U/g for the low- and high molecular weight resin respectively. The uptake data were modeled using a number of 2- and 3- parametric isotherm equations (Langmuir, Freundlich, Langmuir–Freundlich, Toth and Redlich–Peterson). The kinetics of the uranium removal was also studied and modeled using the pseudo-first and pseudo-second order equations. The surface and interior of the resin grains were examined after the sorption experiments by scanning electron microscopy/energy dispersive spectroscopy.
The Cr(VI) uptake from aqueous solutions by polyhexamethylene-guanidine-modified natural zeolitic materials from Metaxades, Greece (PHMG-MTX) and Tedzami, Georgia (PHMG-TZ) was investigated using ...batch techniques. Spectrophotometry using 1,5-diphenylcarbazide for colour development was used for Cr determination. The Cr(VI)-solution concentration varied between 5 and 50
mg/L and the initial pH was adjusted to 3.0, 4.0 and 5.0. Additional experiments were conducted in the presence of competing anions (background electrolyte
I
=
0.1
M established by 0.1
M NaNO
3 and 0.033
M Na
2SO
4) on solutions with unadjusted pH. For comparison, the Cr(VI) adsorption by Tedzami tuffs modified by octadecylpolyhexamethylene-guanidine-chloride (ODPHMG-TZ) was also investigated. All investigated materials adsorbed considerable amounts of Cr(VI)-oxyanions. It was shown that the Cr(VI)-uptake strongly depended on pH and the presence of competing anions. The Cr(VI)-oxyanion uptake by PHMG-TZ was slightly higher than that observed for ODPHMG-TZ, whereas the sorption capacity of PHMG-MTX was of the same order of magnitude as Metaxades tuffs modified by hexadecyl-trimethylammonium-bromide. The experimental data obtained for pH
init
=
3.0 were selected for modeling the adsorption behavior of the materials using six isotherm equations (Freundlich (
F), Langmuir (
L), Langmuir–Freundlich (
L–
F), Dubinin–Radushkevich (
D–
R), Redlich–Peterson (
R–
P), Toth (
T)). The obtained modeling results indicated that, although the three-parameter models, taking into account the surface heterogeneity, provided the closest approach to the measurement data, the parameters estimates could be highly biased. On the other hand, the two-parameter Langmuir isotherm was sufficient to describe the process equilibrium in terms of smallest number of adjustable parameters and approximation of the sorption capacity.
This study of the Aptian lower part of the Carolinefjellet Formation in Svalbard, Norwegian high Arctic, is based on well cores and outcrop section in the Adventdalen area of Spitsbergen and reports ...on the deposits and bioturbation structures of an ancient subpolar marine shelf from a well-known period of global greenhouse climate. The study documents the sedimentation conditions and benthic fauna activity on a warm-water aggrading shelf subject to harsh Arctic wave climate and eurybatic base-level changes, with episodic bottom incursions of cold polar water. Lithofacies associations and 38 observed ichnotaxa represent subenvironments ranging from offshore to lower shoreface and hosting the
Cruziana
ichnofacies in its distal to proximal expression, with a brief mid-Aptian encroachment of middle shoreface zone with a distal expression of the
Skolithos
ichnofacies. The ichnofacies are variously impoverished compared to their archetypes. The sediment bioturbation intensity varies, but similar lithofacies associations show a comparable intensity throughout the stratigraphic succession, which indicates an ichnofauna ecology controlled by the seafloor hydraulic regime and oxygenation, and thus mainly by the wave climate and relative sea-level changes. Sandstone tempestites indicate high-frequency storms, commonly exceeding the magnitude of largest modern hurricane events. The study confirms that a change in global climate mode, such as the Early Cretaceous warming, entails extreme weather conditions.
The removal of chromates and iodides from aqueous solutions by organo-modified tuffs from the Pentolofos area (Thrace, Greece) was investigated using
51Cr- and
131I-labelled solutions and gamma-ray ...spectroscopy. The zeolitic material was modified by hexadecyltrimethyl-ammonium bromide (HDTMA-Br) and octadecyltrimethyl-ammonium bromide (ODTMA-Br) and characterized by scanning electron microscopy, FT-IR spectrometry and zeta potential measurements.
Both experimental study and modelling indicated that both organo-zeolitic sorbents have a bigger affinity for iodide than for chromate. The chromium uptake did not seem to be influenced by the type of modifier but showed, as expected, a dependence on the solution pH. The maximum sorption capacity (2.27
mg/g) of Cr(VI) was achieved for the solution of initial pH 4. On the other hand, the HDTMA-modified tuff showed a lower sorption affinity for iodides than did the ODTMA-modified one (3.37 and 4.02
mg/g, respectively).
Hybrid event beds comprising clay‐poor and clay‐rich sandstone are abundant in Maastrichtian‐aged sandstones of the Springar Formation in the north‐west Vøring Basin, Norwegian Sea. This study ...focuses on an interval, informally referred to as the Lower Sandstone, which has been penetrated in five wells that are distributed along a 140 km downstream transect. Systematic variations in bed style within this stratigraphic interval are used to infer variation in flow behaviour in relatively proximal and distal settings, although individual beds were not correlated. The Lower Sandstone shows an overall reduction in total thickness, bed amalgamation, sand to mud ratio and grain size in distal wells. Turbidites dominated by clay‐poor sandstone are at their most common in relatively proximal wells, whereas hybrid event beds are at their most common in distal wells. Hybrid event beds typically comprise a basal clay‐poor sandstone (non‐stratified or stratified) overlain by banded sandstone, with clay‐rich non‐stratified sandstone at the bed top. The dominant type of clay‐poor sandstone at the base of these beds varies spatially; non‐stratified sandstone is thickest and most common proximally, whereas stratified sandstone becomes dominant in distal wells. Stratified and banded sandstone record progressive deposition of the hybrid event bed. Thus, the facies succession within hybrid event beds records the longitudinal heterogeneity of flow behaviour within the depositional boundary layer; this layer changed from non‐cohesive at the front, through a region of transitional behaviour (fluctuating non‐cohesive and cohesive flow), to cohesive behaviour at the rear. Spatial variation in the dominant type of clay‐poor sandstone at the bed base suggests that the front of the flow remained non‐cohesive, and evolved from high‐concentration and turbulence‐suppressed to increasingly turbulent flow; this is thought to occur in response to deposition and declining sediment fallout. This research may be applicable to other hybrid event bed prone systems, and emphasizes the dynamic nature of hybrid flows.
Background
Struvite, biochar and ash products (collectively known as STRUBIAS) derived from different waste streams are used as fertilisers in agriculture. Raw dairy processing sludge (DPS) shows ...promise as bio‐based fertilisers, but secondary STRUBIAS‐derived products need further testing as fertilisers.
Aims
The objective of this study was to calculate the phosphorus mineral fertiliser equivalency (P‐MFE) for some STRUBIAS products derived from DPS.
Methods
Ryegrass (Lolium perenne L.) and wheat (Triticum aestivum) pot trials were used to determine the P‐MFE using the apparent P recovery (APR) method for Fe‐DPS and DPS‐derived struvites (Struvite 1–4), hydrochars (HC1–3) and ash.
Results
The tested STRUBIAS products can be divided into two groups: (1) a range of products that can (i.e. Struvite 1–3) and (2) cannot (i.e., Struvite 4, HC1–3, ash and Fe‐DPS) be considered fertilisers. In the first group, the P‐MFE ranged from 66.8% to 76.7% for ryegrass and from 77.9% to 93.5% for spring wheat grain. In the second group, the P‐MFE ranged from 7.8% to 58.3% for ryegrass and from −34.5% to −151.3% for spring wheat grain. The negative agronomic effects of some products for wheat grain (struvite and HC) in this study were mainly caused by high Fe content, which could be overcome by improved treatment processes.
Conclusions
Future policy and research must be aware that not all the DPS‐derived STRUBIAS products are suitable as fertilisers and therefore need to be tested individually.
Flow chart of experimental setup, results and take home message.
In this study, the removal of Co(II) and Ni(II) ions from contaminated water was investigated using silica gel materials functionalized with both ethylenediaminetetraacetic acid (EDTA) and ...diethylenetriaminepentaacetic acid (DTPA). The modified adsorbents were characterized using elemental analysis, surface area and pore size analysis, and zeta potential analysis. The adsorption and regeneration studies were conducted in batch mode. The optimum conditions for the removal of both metals at an initial concentration of 10
mg/L were 2
g/L of dose, pH 3, 50
rpm of agitation speed and 4
h of contact time. The removal of Co(II) and Ni(II) by EDTA- and/or DTPA-modified silica gels was substantially higher than that by their unmodified form. The maximum Co(II) and Ni(II) uptakes by the EDTA-modified silica gel were 20.0 and 21.6
mg/g, comparable to their adsorption capacities by DTPA-modified silica gel (Co(II): 16.1
mg/g; Ni(II): 16.7
mg/g). At the same concentration of 10
mg/L, the removal of both metals by the modified adsorbents ranged from 96% to 99%. The two-site Langmuir model was representative to simulate adsorption isotherms. The kinetics of Co(II) and Ni(II) adsorption by modified silica gels followed pseudo-second-order.
On October 1, 2012, as part of the Affordable Care Act, the Centers for Medicare and Medicaid Services began to reduce payments to hospitals with excessive rehospitalization rates through the ...Hospital Readmissions Reduction Program. These financial penalties have intensified hospital leaders' efforts to implement strategies to reduce readmission rates. The purpose of this multiple case study was to explore organizational strategies that leaders use to reduce readmission rates in hospitals located in a non-Medicaid-expansion state. The data collection included semistructured interviews with 15 hospital leaders located in five metropolitan and rural hospitals in southwest Missouri. Consistent with prior research, the use of predictive analytics stratified by patient population was acknowledged as a key strategy to help reduce avoidable rehospitalization. Study findings suggest that leveraging data from the electronic health records to identify at-risk patients provides comprehensive health information to reduce readmissions. Hospital leaders also revealed the need to understand and address the health needs of their local population, including social determinants such as lack of access to transportation as well as food and housing.
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