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diffractometer, using Ni-filtered CuKα-radiation. Room temperature diffractograms were recorded at a scanning speed of 0.002° 2θ s −1 from 5° to 50°. BET specific surface areas were determined by nitrogen adsorption at the temperature of liquid nitrogen on a
Thermal destruction of rice hull in air and nitrogen
A systematic study
chemical compositions, structures, morphologies, BET surface areas, and pore characteristics of RHA samples by means of XRD, FT-IR, SEM, EDS, and nitrogen adsorption analyses. RHA presents different physico-chemical and pore characteristics in different
1123 1141 . C. Woodruff S. Gregory 2005 Profile of Internet gamblers: Betting on the
over the study period, there was no indication of an increase in gamblers with the highest gambling levels ( Auer & Griffiths, 2021 ). A similar study that included an anonymous commercial gambling operator for sports betting and online casino services
, Hing, & Gainsbury, 2015 ). Sports betting promotions are one of the most common types of televised advertisements in Australia, and are considered to normalize the gambling experience, as well as prematurely expose young people to gambling ( Derevensky
Abstract
Organoclays are the adsorption products of organic matter by clay minerals. In modern technology, organoclay-based nanocomposites obtained by modifying Na-clay by primary adsorption of organic ammonium cations or long-chain cationic surfactants are widely used in different industries. They are potential candidates for serving as sorbents of different organic compounds by secondary adsorption. Organoclays are widely spread in the environment and are responsible for the colloid behavior of different environmental elements such as soils. This manuscript summarizes some of the basic knowledge on thermal analysis of organoclays and reviews some of the recent studies carried out in our laboratory on organoclays which occur in the environment, those applied in industry and of those obtained by secondary adsorption processes. Complexes in the environment or those used in industry are mainly of the smectite clay mineral montmorillonite and their thermal analysis in air is treated here.
Thermal analyis of hexadecyltrimethylammonium–montmorillonites
Part 1. Thermogravimetry, carbon and hydrogen analysis and thermo-IR spectroscopy analysis
Abstract
Na-montmorillonite (Na-MONT) was loaded with hexadecyltrimethylammonium cations (HDTMA) by replacing 41 and 90% of the exchangeable Na with HDTMA, labeled OC-41 and OC-90, respectively. Na-MONT, OC-41, and OC-90 were heated in air up to 900 °C. Unheated and thermally treated organoclays heated at 150, 250, 360, and 420 °C are used in our laboratory as sorbents of different hazardous organic compounds from waste water. In order to get a better knowledge about the composition and nature of the thermally treated organoclays Na-MONT and the two organo-clays were studied by thermogravimetry (TG) in air and under nitrogen. Carbon and hydrogen contents in each of the thermal treated sample were determined and their infrared spectra were recorded. The present results showed that at 150 °C both organoclays lost water but not intercalated HDTMA cations. At 250 °C, many HDTMA cations persisted in OC-41, but in OC-90 significant part of the cations were air-oxidized into H2O and CO2 and the residual carbon formed charcoal. After heating both samples at 360 °C charcoal was present in both organo clays. This charcoal persisted at 420 °C but was gradually oxidized by air with further rise in temperature. TG runs under nitrogen showed stepwise degradation corresponding to interlayer water desorption followed by decomposition of the organic compound, volatilization of small fragments and condensation of non-volatile fragments into quasi-charcoal. After dehydroxylation of the clay the last stages of organic matter pyrolysis and volatilization occurred.
Abstract
Na-montmorillonite was loaded with tetraethylammonium cations (TEA) or with benzyltrimethylammonium cations (BTMA) by replacing 77 and 81% of the exchangeable Na with TEA or BTMA, labeled TEA-MONT and BTMA-MONT, respectively. TEA- and BTMA-MONT were heated in air up to 900 °C. Thermally treated organoclays are used in our laboratory as sorbents of organic compounds from water. The two organoclays were studied by TG and DTG in air and under nitrogen. Carbon content in each of the heated sample was determined. They were diffracted by X-ray, and fitting calculations of d(001) peaks were performed on each diffractogram. TG and thermo-C analysis showed that at 150 and 250 °C both organoclays lost water but not intercalated ammonium cations. DTG peak of the first oxidation step of the organic cation with the formation of low-temperature stable charcoal (LTSC) appeared at 364 and 313 °C for TEA- and BTMA-MONT, respectively. The charcoal was gradually oxidized by air with further rise in temperature. DTG peak of the second oxidation step with the formation of high-temperature stable charcoal (HTSC) appeared at 397 and 380 °C for TEA- and BTMA-MONT, respectively. DTG peak of the final oxidation step of the organic matter appeared at 694 and 705 °C for TEA- and BTMA-MONT, respectively, after the dehydroxylation of the clay. Thermo-XRD analysis detected TEA-MONT tactoids with spacing 1.40 and 1.46 nm up to 300 °C. At 300 and 360 °C, LTSC-MONT tactoids were detected with spacing of 1.29 nm. At higher temperatures, HTSC-MONT-α and -β tactoids were detected with spacings of 1.28 and 1.13 nm, respectively. BTMA-MONT tactoids with spacings 1.46 and 1.53 nm were detected up to 250 °C. At 300 and 360 °C, LTSC-MONT tactoids were detected with a spacing of 1.38 nm. At higher temperatures, HTSC-MONT-α and -β tactoids were detected with spacings of 1.28 and 1.17 nm, respectively. At 650 °C, both clays were collapsed. HTSC-β-MONT differs from HTSC-α-MONT by having carbon atoms keying into the ditrigonal holes of the clay-O-planes. At 900 °C, the clay fraction is amorphous. Trace amounts of spinel and cristobalite are obtained from thermal recrystallization of amorphous meta-MONT.
Thermal analysis of hexadecyltrimethylammonium-montmorillonites
Part 2. Thermo-XRD-spectroscopy-analysis
Abstract
Na-montmorillonite (Na-MONT) was loaded with hexadecyltrimethylammonium cations (HDTMA) by replacing 41 and 90% of the exchangeable Na with HDTMA. The organoclays were labeled OC-41 and OC-90, respectively. Freeze-dried Na-MONT, OC-41, and OC-90 were heated in air at 150, 250, 360, 420, 550, 700, and 900 °C. The thermally treated samples were suspended in water, air-dried, and desiccated over silica during 40 days. All samples were diffracted by X-ray and fitting calculations were performed on each diffractogram. These calculations gave information on basal spacings, relative concentrations, and homogeneity of the different tactoids obtained at each temperature, before and after suspending and desiccating. HDTMA-MONT tactoids with spacing ≥1.41 nm appeared between 25 and 250 °C. OC-41 or OC-90 intercalated monolayers or bilayers of HDTMA, respectively. At 250 °C OC-41 was air-oxidized to a smaller extent than OC-90, resulting in charcoal-MONT tactoids. With further heating the organic matter was gradually oxidized and at 700 °C both clays were collapsed. During the thermo-XRD-analysis of both organoclays three types of charcoal-MONT complexes appeared: (1) LTSC-MONT tactoids with a basal spacing 1.32–1.39 nm, between 250 and 420 °C in both clays; (2) HTSC-α-MONT tactoids with spacing 1.22–1.28 nm, between 360 or 250 and 500 or 550 °C in OC-41 or OC-90, respectively; (3) HTSC-β-MONT with spacing 1.12–1.18 nm, between 360 and 550 °C in both clays, where LTSC and HTSC are low- and high-temperature stable charcoal, respectively. HTSC-β-MONT differs from HTSC-α-MONT by having carbon atoms keying into the ditrigonal holes of the clay-O-planes.
Abstract
The adsorption of the tertiary aromatic amide alachlor by Na-montmorillonite and Al-polyhydroxy-montmorillonite was investigated by DTA, XRD, SEM and Thermo-FTIR Spectroscopy. This molecule is adsorbed into the interlayer space of the montmorillonite, replacing interlayer water. In this organo-clay complex the interlayer water forms hydrogen bonds with N or O atoms of the tertiary amide group. Samples which were aged during six months degraded by hydrolysis to give mainly secondary amide. This reaction was catalysed by Al-polyhydroxy-montmorillonite more than by Na-montmorillonite.
