Search results for "Kaolinite"

Adsorption of dissolved organic matter on clay minerals as assessed by infra-red, CPMAS 13C NMR spectroscopy and low field T1 NMR relaxometry

2011

Abstract Dissolved organic matter (DOM) is a very important environmental constituent due to its role in controlling factors for soil formation, mineral weathering and pollutant transport in the environment. Prediction of DOM physical–chemical properties is achieved by studying its chemical structure and spatial conformation. In the present study, dissolved organic matter extracted from compost obtained from the organic fraction of urban wastes (DOM-P) has been analysed by FT-IR, CPMAS 13C NMR spectroscopy and 1H T1 NMR relaxometry with fast field cycling (FFC) setup. While the first two spectroscopic techniques revealed the chemical changes of dissolved organic matter after adsorption eith…

Adsorption isotherms and thermal behavior of hybrids based on quercetin and inorganic fillers

2019

We investigated the adsorption process of quercetin onto several inorganic fillers, such as kaolinite, calcium carbonate and alumina. Firstly, we performed equilibrium adsorption studies in order to determine the quercetin/filler adsorption isotherms, which were successfully fitted through the Langmuir model. Based on the adsorption data analysis, we estimated the maximum adsorption capacity of each filler as well as the Langmuir constant, which is related to the affinity between quercetin and the surfaces of the inorganic particles. Then, we prepared hybrids formed by fillers saturated with quercetin. The obtained composites were characterized by thermogravimetric analysis with the aim of …

Nanocomposites based on esterified colophony and halloysite clay nanotubes as consolidants for waterlogged archaeological woods

2017

We have designed an innovative protocol for the consolidation of waterlogged archaeological woods by using acetone mixtures of halloysite clay nanotubes and a chemically modified colophony (Rosin). Firstly, we have investigated the thermal properties of HNTs/Rosin nanocomposites, which have been prepared by means of the casting method from acetone. The HNTs content have been systematically changed in order to study the influence of the inorganic filler on the thermal stability and glass transition process of Rosin. We have observed that the thermal properties of the hybrids are affected by the specific HNTs/Rosin interactions. Then, acetone dispersions of HNTs/Rosin composites at variable f…

Continental weathering and climatic changes inferred from clay mineralogy and paired carbon isotopes across the early to middle Toarcian in the Paris…

2014

Abstract Lower Toarcian strata (Lower Jurassic) have been extensively studied with a view to understanding the oceanographic, climatic and biological processes that drove the Earth's system into an Oceanic Anoxic Event (OAE). For this time period, the evolution of the European marine seaways is now relatively well constrained owing to multiple geochemical studies, but investigations regarding climatic trends in the continental realm remain sparse. In the present study, we test the clay mineralogy as a continental climate-sensitive proxy in the well-documented Sancerre core (southern Paris Basin). We compare variations in the kaolinite content with p CO 2 fluctuations (derived from paired ca…

The role of pedogenic overprinting in the obliteration of parent material in some polygenetic landscapes of Sicily (Italy)

2016

Abstract Many soils older than the Holocene have experienced several changes, and possess properties that may be due to the complex effect of several stages of soil development; these soils are called polygenetic. It is still rather unclear, however, if, as time elapses, pedogenic processes tend to diverge generating different soils, or converge towards increasingly similar soils. We studied five pedons (37°60′N, 13°90′E) exposed to present weathering simultaneously since the Holocene but located on Upper Miocene or Holocene parent material. Their XRD and FTIR clay mineralogy reveal an overall homogeneity; smectites, calcite and gypsum reach the thermodynamic equilibrium, a slight undersatu…

A new FESEM procedure for assessment of XRD microstructural data of kaolinites

2007

Abstract A sample preparation method for FESEM microstructural analysis of sheet silicates using oriented aggregates on metallic strips parallel to the electronic beam is described. The method allows the easy measurement of thickness of kaolinite crystallites. The results have been compared to the apparent crystallite size measured by XRD The performed measurements for a set of selected kaolinites are in the range 15–60 nm and show a good correlation with XRD crystallite thickness (in the range 11–48 nm) obtained by the Voigt function method.

A structural comparison of halloysite nanotubes of different origin by Small-Angle Neutron Scattering (SANS) and Electric Birefringence

2018

The structure of halloysite nanotubes (Hal) from different mines was investigated by Small-Angle Neutron Scattering (SANS) and Electric Birefringence (EBR) experiments. The analysis of the SANS curves allowed us to correlate the sizes and polydispersity and the specific surfaces (obtained by a Porod analysis of the SANS data) of the nanotubes with their specific geological setting. Contrast matching measurements were performed on patch Hal (from Western Australia) in order to determine their experimental scattering length density for a more precise analysis. Further characterization of the mesoscopic structure of Hal was carried out by Electric Birefringence (EBR), which allowed to study th…

ADSORPTION OF WATER MOLECULES ONTO 1:1 DIOCTAHEDRAL CLAY MINERALS: A BADER'S TOPOLOGICAL ANALYSIS OF THE AB-INITIO ELECTRON DENSITIES

2011

Neptunium(V) sorption on kaolinite

2011

Abstract The sorption behavior of neptunium(V) onto the clay mineral kaolinite was studied in batch experiments under different experimental conditions: [Np(V)]=7 × 10−12–8 × 10−6 M, solid-to-liquid ratio 2–20 g L−1, I=0.1 and 0.01 M NaClO4, pH=6–10, ambient air and Ar atmosphere. The short-lived isotope 239Np (T 1/2=2.36 d) was used instead of 237Np (T 1/2=2.14 × 106 a) to study the sorption behavior of Np(V) at environmentally-relevant concentrations, i.e., 7 × 1012 M Np. In addition, 239Np(V) served as tracer to measure sorption isotherms over six orders of magnitude in Np concentration (4.8 × 10−12–1.0 × 10−4 M). The results show that Np(V) sorption on kaolinite is strongly influenced b…

Studies of the ternary systems humic substances – kaolinite – Pu(III) and Pu(IV)

2008

AbstractThe behaviour of plutonium with respect to its migration in the aquifer has been studied under conditions close to nature. Most relevant under these conditions are Pu(III) and Pu(IV) in contact with humic substances (HS) and minerals. As a model for the host rock, kaolinite (KGa-1b) was chosen. The complexation of Pu(III) and Pu(IV) with Aldrich humic acid (AHA) in aqueous solution at ionic strength 0.1 M was investigated by the ultrafiltration method. The sorption of Pu(III) and Am(III) onto kaolinite (K) as a function of pH and metal-ion concentration was studied under aerobic and anaerobic conditions. The pH edge was found at pH∼5.5 independent of the metal-ion concentration and …