Kinetic, isotherm and pH dependency investigation and environmental application of cationic dye adsorption on montmorillonite

In this study, individual and competitive adsorption of three cationic dye onto montmorillonite were investigated. Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models were used to analyze experimental data for individual and competitive adsorption of dyes. Surface precipitation occured in the presence of inert electrolyte because of decreasing solubility of dye. The organic dye adsorption was pH-independent in a pH scale between 2 and 6. It is, thus, assumed that the adsorption took place between cationic organic dye and permanently negatively charged surface, which is a pH-independent surface site of adsorbent and occured as a result of isomorphic substitution. Mean free energies (E-D) varied between 0.65 and 7.87J/mol, and heats of sorptions (B) changed between 4 and 96J/mol. These low energy values support the electrostatic interaction between surface and dye molecules. Organic dye adsorption showed Langmuirian character and in the presence of more than one adsorptive dye, adsorption capacities remained under individual adsorption capacity values because of competition. Adsorption kinetic showed second order reaction character. Using sodium humate, CaCl2 solution, and acid mixture solution as leach solutions desorption properties were examined. Higher desorption values were achieved by using 1% of sodium humate solution because of hydrophobic interactions and formation of H bonds

Investigation of individual and competitive adsorption of Cu(II), Cd(II), and Pb(II) on montmorillonite in terms of surface complexation and kinetic properties of Cu(II) adsorption

In this study, individual and competitive Cu(II), Cd(II), and Pb(II) adsorptions on montmorillonite were searched by considering surface acidic functional groups of adsorbent. pH dependency of adsorptions and kinetic properties of Cu(II) adsorption was investigated. Cu(II) adsorption on montmorillonite fits pseudo-first-order reaction with the 0.008k value. Individual and competitive heavy metal adsorptions were modeled using Langmuir, Freundlich, Temkin, and Dubinin-Astakhov isotherms. Adsorption capacities were calculated using equations of related linearized models. The adsorption capacities of individual metal adsorption, obtained from linearized models, are higher than the yielded capacities from competitive adsorption experiments. All adsorption energies calculated from linearized Dubinin-Astakhov model varied between 7 and 16kJ/mol. The values of adsorption energies gained for metal adsorption in competition did not significantly differ from those of individual adsorption. Since montmorillonite surface behaves as a weak acid and has a strong buffer effect at pH values between 2 and 3, the pH dependency of adsorption was explained by taking into account the surface acidic properties of adsorbent and introduced preferred surface sites beyond adsorption with increasing pH. Cu(II), Cd(II), and Pb(II) existence on loaded montmorillonite was proved by the aid of SEM-EDX results

Paraganglioma of the cauda equina: A highly vascular tumour

WOS: 000286124000024PubMed ID: 20637630Paragangliomas uncommonly occur in the cauda equina region. This type of tumour may be misdiagnosed pre-operatively as a neurinoma or an ependymoma. Paragangliomas are highly vascular tumours. We report three patients with paraganglioma of the cauda equina. The first patient had many dilated vessels resembling an arteriovenous malformation, which were seen during surgery. The second patient had a post-operative haemorrhage without any residual tumour. The third patient had a selective angiogram with dense tumour staining. (c) 2010 Elsevier Ltd. All rights reserved

A Rare History: an Intracranial Nail Present for Over a Half-Century

We present a rare case of a patient with a persistent headache for many years found to have an intracranial nail present for nearly 65 years. The nail was found entering approximately 1 cm from the midline on the left side, passing below the superior sagittal sinus, with the tip 1.5 mm right of the frontal horn of the lateral ventricle. Treatment strategies designed to optimize outcome for intracranial foreign bodies and possible complications are discussed in this report. We also discuss the decision for surgical intervention for foreign bodies and the relevance of position of the foreign body

MODELING OF ACIDIC AND COMPLEXATION PROPERTIES OF HUMIC ACIDS USING THE IRWING-ROSSOTTI METHOD

Consequently, distribution of humic acids between solid and liquid phases, mechanism of surface protonation and metal-humate complexation are introduced through this study

MODELING OF ACIDIC AND COMPLEXATION PROPERTIES OF HUMIC ACIDS USING THE IRWING-ROSSOTTI METHOD

In this study, acidic and metal complexation properties of five humic acid samples, obtained from different source, were investigated. Humic acid samples were extracted with 1 M NaOH solution and then precipitated using concentrated HCl. Thus, purified humic acid samples were used in neutralization and Cu(II) complexation experiments. Purity of the humic acid samples varies between 75-85 %. Structural analysis of purified humic acid samples were performed by using FTIR, SEM and LC-MS methods. Molecular weights of them were determined by the aid of LC-MS method. Distribution coefficients (K-D) of humic acid samples in convenient solvent were also investigated and calculated. The data gained as a result of potentiometric titration were evaluated in Irwing-Rossotti method. Thus, acidity constants of -COOH and -OH groups, that can release proton, and formation constants of Cu(II) - humate complexes were determined. All experiments were performed at 2 degrees C and 25 degrees C

Nonoperative treatment of acute extradural hematomas: Analysis of 80 cases

WOS: A1996VL84800016PubMed ID: 8858030Between 1986 and 1994, 270 patients with an acute extradural hematoma (EDH) were treated in the Department of Neurosurgery, Izmir State Hospital in Izmir, Turkey. Eighty patients with a supratentorial EDH of less than 30 mL in volume were treated conservatively. The 69 male and 11 female patients ranged in age from 5 to 68 years. Five of the patients subsequently underwent surgery because of the deterioration in the level of consciousness and enlargement of EDH. One patient died after the operation. EDHs were localized in the temporal region in all five patients who subsequently required the surgical intervention. It has been emphasized that the findings on a computed tomographic (CT) scan performed very early may be misleading in patients with an EDH in progress. We concluded that the temporal location of EDHs with heterogeneous density in patients whose CT scan was performed less than 6 hours after trauma had a higher risk of hematoma growth and thus should be treated surgically. Periodic CT scans should be performed at brief intervals during the early phase of hospitalization

Determination of total antioxidant capacity of humic acids using CUPRAC, Folin-Ciocalteu, noble metal nanoparticle- and solid-liquid extraction-based methods

Total antioxidant capacity (TAC) of humic acid (HA) samples was determined using CUPRAC (CUPric Reducing Antioxidant Capacity), FC (Folin-Ciocalteu), QUENCHER-CUPRAC, QUENCHER-FC, Ag-NP (Silver nanoparticle)- and Au-NP (Gold nanoparticle)-based methods. Conventional FC and modified FC (MFC) methods were applied to solid samples. Because of decreased solubility of Folin-Ciocalteu's phenol reagent in organic solvents, solvent effect on TAC measurement was investigated using QUENCHER-CUPRAC assay by using ethanol:distilled water and dimethyl sulfoxide:distilled water with varying ratios. To see the combined effect of solubilization (leaching) and TAC measurement of humic acids simultaneously, QUENCHER experiments were performed at 25 degrees C and 50 degrees C; QUENCHER-CUPRAC and QUENCHER-FC methods agreed well and had similar precision in F-statistics. Although the Gibbs free energy change (Delta G degrees) of the oxidation of HA dihydroxy phenols with the test reagents were negative, the Delta G degrees was positive only for the reaction of CUPRAC reagent with isolated monohydric phenols, showing CUPRAC selectivity toward polyphenolic antioxidants. This is the first work on the antioxidant capacity measurement of HA having a sparingly soluble matrix where enhanced solubilization of bound phenolics is achieved with coupled oxidation by TAC reagents. (C) 2016 Elsevier B.V. All rights reserved