In order to improve the removal efficiency of clays in oil refining, to explore the related factors and to clarify the removal mechanism of alkaline nitride, a series of modified clays was prepared to test removal of alkaline nitride from lubricating oil. After the addition of 1 wt.% FeCl3, the removal rate of alkaline nitride increased from 33.6% to 43.3%. Furthermore, the acidity and chlorine content did not exceed acceptable levels. The testing methods of N2 adsorption–desorption, particle-size distribution, Fourier-transform infrared spectroscopy and X-ray diffraction were conducted to verify the removal mechanism. The removal rate of alkaline nitride is mainly related to the density of Lewis acid sites. The Fourier-transform infrared spectra confirmed the existence of the complexation reaction. The basic nitrides were removed by chemical adsorption via Fe3+-complexation.

Hierarchical layered double hydroxide (HLDH) was synthesized by using sodium dodecyl sulfate (SDS) as a soft-template agent for the removal of two charged organic dyes (i.e. methylene blue (MB; cationic dye) and methyl orange (MO; anionic dye)). The experimental results based on response surface methodology (RSM) demonstrated distinct removal behaviours of HLDH towards these two dyes: (1) the maximum capacity was 416.7 mg g–1 for MO and 58.7 mg g–1 for MB at 25°C; (2) the increase in temperature could enhance MO removal significantly, whereas it had a negligible effect on the MB treatment process; and (3) rapid removal of MB (5 min) compared to MO (480 min) was observed. In addition, the removal process for both dyes was pH-independent. Multiple characterization techniques further revealed the removal mechanisms, demonstrating that SDS played a significant role in the removal of both dyes; that is, MO replaced SDS to be intercalated into the HLDH interlayer via anion exchange. MB could influence the –SO3 group of SDS, resulting in it modifying the electrodensity of SDS. It could then be further combined with an SDS anion (DS–) via hydrophobic and electrostatic interactions to form DS-MB monolayers. This work not only provides an efficient capture agent for charged dyes, but also offers a deep insight into the underlying removal mechanism.

Halloysite is a 1:1 dioctahedral clay mineral that has been studied widely for applications in nanotechnology and as a mineral exploration guide for recognizing regolith-hosted heavy rare earth element (HREE) deposits. In Brazil, pegmatites from the state of Rio de Janeiro have been catalogued, but their potential to host halloysite deposits has never been studied. After a mineral exploration programme, one pegmatite with considerable halloysite contents and economic potential was discovered. This study reports the mineralogical and chemical characterization of the halloysite of this pegmatite and evaluates the possibility of clay-adsorbed HREE deposits, like that in the Zudong (China) regolith-hosted HREE deposit. Seven samples were collected in horizontal channels. Bulk samples and clay fractions (<2 μm) were analysed by quantitative mineral analysis (X-ray diffraction/Rietveld method), chemical analysis (major elements by X-ray fluorescence and Y, U, Th and rare earth elements by inductively coupled plasma mass spectrometry), scanning electron microscopy, Fourier-transform infrared spectroscopy, particle-size analysis, nitrogen physisorption and cation-exchange capacity. Mixed polygonal/cylindrical halloysite-7Å in concentrations between 6.3 and 35.4 wt.% in bulk samples and between 58.0 and 89.8 wt.% in the clay fractions were identified in the pegmatite. The clay fractions presented an average chemical composition of 45.46 wt.% SiO2, 36.10 wt.% Al2O3, 14.62 wt.% loss on ignition and 1.04 wt.% Fe2O3, as well as technological properties close to those observed in world-class halloysite deposits such as Dragon Mine (USA) and Matauri Bay (New Zealand). The clay minerals did not present significant HREE contents.

Modified sericite mica was prepared by combining the intercalation of cetyltrimethylammonium bromide (CTAB) through ion exchange and surface modification of 3-aminopropyltriethoxysilane (KH550) with the following steps: high-temperature activation of sericite mica, acid activation, sodium modification, LiNO3 treatment, the ion-exchange intercalation of the cetyltrimethylammonium cation (CTA+) and surface modification of KH550. High-temperature activation was the most critical step for the modified sericite mica, and the number of hydroxyl groups of mica under high temperature directly affected the surface modification of KH550. The effects of various activation temperatures on the surface modification of sericite mica were investigated. The structure of activated sericite mica was intact when activation temperature was 600°C or 700°C, and the surface modification of sericite mica was not affected. The structure of activated sericite mica was partially destroyed at 800°C. The optimal temperature for activating sericite mica was 700°C. The structure and morphology of modified sericite mica were characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, Brunauer–Emmett–Teller (BET) analysis and loose bulk volume. The KH550 could not only chemically graft onto the surface of sericite mica, but also enter into the interlayer through electrostatic attraction after its end amino group was protonated. The interlayer spacing of modified sericite mica increased to 3.22 nm, indicating that it might be an excellent layered silicate for preparing clay–polymer nanocomposites.

Two novel adsorbents – montmorillonite (Mnt)-hyamine and Mnt-hyamine-sodium dodecyl sulfate (SDS) – were synthesized using Mnt nanoparticles. The modified Mnt and Mnt nanoparticles were used for the removal of crystal violet from water, and they were characterized using various techniques. The effects of pH, time, temperature, adsorbent dosage and initial dye concentration on the dye-removal efficiency were investigated using response surface methodology. The optimum conditions for maximum dye removal were obtained. The optimum conditions for crystal violet adsorption on Mnt-hyamine, Mnt-hyamine-SDS and Mnt nanoparticles are temperatures 25.00°C, 29.97°C and 27.28°C; pH values 9.00, 10.41 and 9.40; adsorbent dosages 1.00, 1.15 and 1.06 g L–1; and initial dye concentrations 30.00, 98.74 and 99.44 mg L–1, respectively. The adsorbent dosage is the most critical variable for dye removal. Temkin and Langmuir are the best isotherms for studying adsorption equilibria. In the kinetic study, the fractal-like integrated kinetic Langmuir model was the most appropriate model, and the thermodynamic parameters were also determined. The synthesized adsorbents could be easily separated from solution. The Mnt-hyamine-SDS adsorbent has a high adsorption capacity (690.69 mg g–1) for the removal of crystal violet.

In this study, the adsorption of NH3 gas on a bentonite from Ünye (Turkey) in its natural state and after acid treatments, was investigated experimentally at 298 K and up to 100 kPa. Bentonite was treated with HCl solutions of various concentrations (0.5–2.5 M) at 75°C for 4 h. X-ray diffraction (XRD), X-ray fluorescence (XRF), N2 adsorption and thermogravimetric/differential thermal analysis (TG/DTA) were used to characterize the bentonite before and after acid treatment. The quantitative XRD analysis demonstrated that the bentonite sample was composed predominantly of smectite (75%), with abundant feldspar (20%) and minor opal-CT, analcime and quartz (5%). Increasing gas adsorption values of acid-treated bentonites were analysed depending on the structural changes of the clay. The NH3-adsorption capacities of the bentonite samples (3.801–5.068 mmol g–1) were also compared with previously studied clay-based materials (0.828–4.000 mmol g–1) in terms of their textural and structural differences.

Montmorillonite (Mnt), a clay mineral with a nanolayered structure, was combined with an Fe-based metal–organic framework (MOF; MIL-53(Fe)) using an in situ growth technique that yielded a novel eco-friendly clay-based adsorbent (MIL-53(Fe)@Mnt). The adsorbent was characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and N2 gas adsorption. The MIL-53(Fe) particles grew on the surface of the nanolayered Mnt and the MIL-53(Fe) particle size became smaller. The adsorption performance of MIL-53(Fe)@Mnt was investigated by removing methylene blue (MB), and optimization experiments were carried out to study the effects of contact time, pH, initial dye concentration and adsorbent mass on the adsorption processes. The MIL-53(Fe)@Mnt exhibited excellent adsorption capacity for MB, namely 313.7 mg g−1, which was 3.02 times and 3.54 times greater than that of pure Mnt and MIL-53(Fe), respectively. Adsorption was fitted with the Langmuir isotherm model and followed a pseudo-second order kinetic model. The MIL-53(Fe)@Mnt obtained is a low-cost and eco-friendly adsorbing material and might be a candidate for removing dyes during water treatment.

NaY zeolite was synthesized from kaolin/dimethyl sulfoxide (DMSO) intercalation composites using an in situ crystallization technique. The effects of the intercalation ratios and the amounts of the kaolin/DMSO intercalation composite on the synthesis of an NaY zeolite molecular sieve were studied. The samples were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, differential thermal analysis, N2 adsorption–desorption and scanning electron microscopy. In the in situ synthesis system, when the kaolin/DMSO intercalation composite was added, pure NaY zeolite was formed. By increasing the amount of kaolin/DMSO intercalation composite added, the crystallinity of the samples increased, and after reaching the maximum amount of kaolin/DMSO intercalation composite added, the crystallinity decreased with further increases of the amount of kaolin/DMSO intercalation composite added. To higher intercalation ratio, the crystallinity can be greatly improved at the lower addition content. At an intercalation ratio of 84%, the added amount of kaolin/DMSO intercalation composite was 2.5% and the crystallinity of the NaY zeolite molecular sieve reached a maximum value of 45%. At intercalation ratios of 55% and 22%, the amount of kaolin/DMSO intercalation composite added was 15% and the crystallinities of the NaY zeolite molecular sieves were 44% and 47%, respectively. The NaY zeolite has good thermal stability and a particle diameter of ~0.5 μm. The Brunauer–Emmett–Teller (BET) specific surface area and pore volume of the sample were 519 m2 g–1 and 0.355 cm3 g–1, respectively.

The surface coating of a gas reaction electrode with layered double hydroxides (LDHs) featuring various electrode catalyst activities was prepared via electrodeposition and the subsequent crystal growth of LDHs. LDH formation was confirmed by X-ray diffraction and Raman scattering measurements after subsequent crystal growth on respective electrodeposited precursor films in Ni-Fe and Zn-Al LDH systems. However, the crystal growth of LDHs in Ni-Mn and Cu-Mn systems was observed on the Mg-Al LDH-electrodeposited films. LDH films were also deposited on the surface of a carbon paper electrode with a rugged surface via electrodeposition and subsequent crystal growth. Using the prepared LDH-coated carbon paper electrodes, the electrode catalytic activity for the oxygen reduction reaction (ORR) was examined. For Ni-Mn, Ni-Al and Ni-Fe LDH-coated carbon paper electrodes, the threshold voltages of the ORR decreased. Hence, the LDHs electrodeposited on a gas reaction electrode have high electrochemical catalytic activity for the ORR.

The Qingliang Temple kiln located in Baofeng County, Henan Province, China, is the discovery site of Ru Kuan porcelain, which is one of the five famous porcelain types of the Song dynasty in China. The ‘Ru-type ware’ and unglazed firing bodies were unearthed from the Qingliang Temple kiln in 2014, and the excavation site was very close to the central firing area of Ru Kuan porcelain. In this paper, the chemical composition, firing temperature and phase structure of the Ru-type ware and unglazed firing bodies from the Qingliang Temple kiln were analysed systematically using energy-dispersive X-ray fluorescence spectrometry, high-temperature thermal expansion and X-ray diffraction. The raw-material sources of the Ru-type ware bodies with various glaze colours are consistent but differ significantly from those of the unglazed firing bodies. The firing temperatures of the Ru-type ware and unglazed firing bodies are 1150–1200°C and 950°C, respectively, which are considered underfired. Mullite, α-quartz, β-cristobalite and α-Fe2O3 are the main constituents of the Ru-type ware bodies, whereas α-quartz and anatase were identified in the unglazed firing bodies. The Ru-type ware is related to the Ru Kuan ware in terms of firing techniques and official use.

Acid-activated clays are inexpensive materials that are used extensively in the removal of unsaturated compounds on an industrial scale. The performance of bentonitic clays in removing these compounds relies heavily on the types of raw clays and acids used in the activation process. In this work, we report on the removal of olefins from aromatic streams by bentonitic clays activated via two different routes. After preliminary tests of four different natural clays, the best clay was selected in terms of it having high swelling index, cation-exchange capacity, specific surface area and suspension stability values. Activation was achieved with hydrochloric acid (HCl) and sulfuric acid (H2SO4), and olefin removal was evaluated after holistic clay characterization by means of X-ray diffraction, X-ray fluorescence, Brunauer–Emmett–Teller (BET) specific surface area analysis, ζ-potential analysis, Fourier-transform infrared (FTIR) spectroscopy after treatment with pyridine, scanning electron microscopy and transmission electron microscopy. The increased basal spacing, replacement of H+ with interlayer cations and retained structural stability of the clay after acid treatment contributed to the improvement of olefin removal for HCl-activated clay. The HCl-activated clay was more efficient in terms of olefin removal than its H2SO4-activated counterpart, removing up to 90% of olefin components after 40 h. Based on pyridine-FTIR spectra and quantitative measurement of the acidic properties of the samples, HCl treatment increased the total number acid sites (Brønsted and Lewis) by approximately ninefold compared to the pristine natural clay and by approximately fourfold compared to the H2SO4-activated clay.

The interaction between chalcopyrite and illite particles was analysed using ζ-potential measurements and flotation tests. Statistically designed tests were used to examine the factors controlling flotation (frother concentration, dispersant concentration, froth height, airflow rate and amount of clay). Furthermore, the significance levels of the impacts of these factors on responses (chalcopyrite grade/recovery, pyrite grade/recovery, dynamic froth stability and mean bubble diameter) were determined. Chalcopyrite and pyrite ζ-potentials were measured in the presence of illite. The addition of 15% illite to the chalcopyrite, especially between pH 11 and 12, shifted the ζ-potential values closer to that of pure illite, indicating complete surface coating of chalcopyrite with illite. In the flotation experiments, better results were obtained in terms of chalcopyrite grade at a low airflow rate and a high froth height. With increasing froth height there was a decline in the gangue mineral recovery as the residence time of the froth increased. The most significant factor increasing pyrite recovery was the amount of clay. Although illite is considered to be the least problematic clay mineral for flotation, as reported in the literature, an illite content of as low as 5% in the ore decreased chalcopyrite grade by 3.83%. While K and Na contents of 4% were detected after flotation without the addition of illite, their abundance increased to 5.7% after the addition of illite.

A hybrid fluorescent pigment composed of fluorescent yellow X-10GFF (FY-10G) and palygorskite (PLG) was prepared by semi-dry grinding. The effects of the physically adsorbed water content and grinding time on the environmental stability of FY-10G/PLG hybrid fluorescent pigments in terms of acid, ethanol and ultraviolet irradiation are discussed in detail. The incorporated FY-10 G molecules are mainly trapped on the external surface and the groove of PLG. Due to the host–guest interaction between PAL and FY-10G, the emission spectrum of the FY-10G/PLG hybrids shifts to a greater wavelength compared with that of FY-10G, but the physically adsorbed water content and grinding time have no effect on the position of the emission spectrum except for its intensity. A larger, physically adsorbed water content and appropriate grinding time may effectively prevent the aggregation and breakage of the bundles of PLG and facilitate FY-10 G molecules to enter into the groove of PAL. This increases the environmental stability of the as-prepared hybrid pigments.

Clays are used in the general production of earthen tiles. In this study, the production and characterization of earthen tiles from schist, a clayey rock formed by metamorphism of mudstone or shale, was investigated. The impact of tiles on atmospheric temperature through their absorption of the visible, near-infrared and far-infrared wavelength regions is evaluated. In particular, the absorption of ultraviolet and infrared radiation by the tiles was evaluated, as this could have beneficial applications for human health and the environment. UV-A radiation (320–400 nm) is not absorbed by the atmosphere, but schist materials absorb UV-A, which can contribute to melanoma formation (i.e. cancer). Field-emission scanning electron microscopy, X-ray fluorescence spectrometry and X-ray diffraction were used for the analysis of the schist materials. The tile-production stages of schist materials (drying, firing, water absorption rate, etc.) were tested at Hatipoglu Gunes Tile and Brick Industry, Inc. (Turkey). The tiles fired at 950°C and 1000°C comply with the industry standard compressive strength values for fired tiles (when converted to industry production conditions) and were 156.15 and 123.20 kg cm–2, respectively.

Polycarboxylate superplasticizer (PCE) is sensitive to the clay present in concrete aggregates. In particular, Montmorillonite (Mnt), an impurity inevitably contained in the aggregate, can significantly influence the performance of concrete. In an effort to improve the compatibility of PCE, a zwitterionic PCE with cationic amide groups and shorter side-chain lengths was synthesized via free radical copolymerization. The optimal synthesis condition was verified via Box-Behnken design. In addition to characterizing the PCE, the performance of PCE in cement pastes with or without Na-Mnt was examined and the underlying mechanism was explored. The results show that, compared with commercially available PCE, the required dosage of PCE for cements containing Na-Mnt decreased. Unlike commercially available PCE, no intercalation occured on the newly manufactured clay-tolerant PCE within the layers of Mnt, resulting in a greater sorption thickness and improved dispersion of the cements containing Na-Mnt.

Clays are raw materials with properties that are necessary for the manufacture of ceramic tiles. The characteristics of clay ceramic raw materials may vary within the same mineral deposit. Clay blending promotes better use of clay reserves, thereby increasing the applicability and life cycle of raw materials. Therefore, it is important to understand the mechanisms controlling the firing of ceramic tiles. In this study, three different clays from a clay deposit were assessed and ten formulations were prepared using the mixture design method. The formulations were analysed using differential thermal and thermogravimetric analyses and dilatometric analysis. Subsequently, the most refractory and fluxing formulations were subjected to thermal tests under various heating rates, similar to the process used for the calculation of apparent sintering activation energy for the densification of clays and for pyroplasticity tests. It is suggested that a mineral deposit can be assessed based on activation energy and thermal kinetics, expanding the alternatives available to the miner through the planning of mixtures with various clays and thus reducing the energy costs of the industrial process.

Palygorskite-bearing claystones and mudstones were deposited in a salt lake in the middle and lower parts of the Neogene Baiyanghe Formation in the Yangtaiwatan Basin, China. The petrological, mineralogical and geochemical characteristics of the sediments were investigated to determine the factors controlling palygorskite formation. The palygorskite claystones and mudstones have distinctly varying mineral compositions. The claystones are composed of detrital minerals, palygorskite and illite, whereas the mudstones consist mainly of mixed-layer illite/smectite and illite. The palygorskite crystals were intact with sharp edges and interwoven with other minerals, indicating an authigenic origin. The chemical characteristics indicate that the palygorskite claystones in the middle part of the Baiyanghe Formation were deposited in a salt lake environment in an arid and hot climate. As the salinity of the lake gradually increased, the detrital minerals such as quartz, feldspar, dolomite and detrital clay minerals dissolved in the alkaline medium, thus providing Si4+, Mg2+ and Al3+ for the crystallization of palygorskite. The palygorskite coexists with certain amounts of detrital quartz and feldspar with limited roundness and sorting, indicating that the shallow lake of the basin under an oxidation environment may represent a favourable environment for the crystallization of palygorskite.

Non-metallic raw materials are largely unexplored in many African countries. In an attempt to reduce this knowledge gap, kaolin occurrences in three promising regions of southern Mauritania were examined. The aim of the paper is to describe the occurrences and characterize the material in terms of mineralogy and potential technical use in the ceramics industry. The kaolins are geologically associated with various sedimentary rock units in either the Coastal Basin (Kaédi), the Mauritanide Belt (Hassi Abyad) or the Taoudeni Basin (Néma). Geochemical data show Al2O3 contents of between 9% and 38% (corresponding to 23–96% kaolinite). Samples from the Hassi Abyad and Kaédi regions have greater kaolinite contents on average and were further investigated mineralogically. The kaolin from the Néma region contained less kaolinite (<50 mass%). The region is also less accessible and hence is not considered further in this study. X-ray diffraction, X-ray fluorescence and infrared spectroscopy confirmed the geochemically calculated kaolinite contents of the kaolins and identified quartz, anatase and goethite as the remaining major mineral constituents. The degree of structural disorder of the kaolinites (determined by infrared spectroscopy) is generally greater in the Kaédi occurrences than at Hassi Abyad. Ceramic tests proved that all of these kaolin raw materials might be used for the production of ceramics, and some may even be used for fine ceramics. From an economic point of view, the Hassi Abyad deposit is interesting in terms of its quality and reserves, aspects that will be addressed in detail in a follow-up study.

Microcapsules are successfully used in various applications such as self-healing, drug delivery and military camouflage. The shells of the microcapsules based on the traditional surfactant-stabilized emulsion template method are often single organic materials. The surfactants generally have insufficient stability against demulsification during preparation of the microcapsules. In the present study, kaolinite was used as an emulsifier for stabilizing Pickering emulsions and subsequently as an enhancer for forming microcapsules. Kaolinite-armoured polyurea microcapsules were fabricated based on the interfacial polymerization of isophorone diisocyanate at the oil–water interfaces of kaolinite-stabilized Pickering emulsions. The prepared microcapsules with core–shell structure were spherical and exhibited good dispersibility in anhydrous ethanol. The shell thickness (~0.5–1.0 μm) and diameter (~20.0–160.0 μm) of kaolinite-armoured polyurea microcapsules may be tailored by varying the dosages of isophorone diisocyanate and kaolinite and the emulsifying speed of the high-shear homogenizer. Hence, the encapsulation and release performance of microcapsules may be controlled. The kaolinite particles were embedded and armoured in a polyurea matrix. The formed kaolinite-embedded and -armoured polyurea structures might prolong the release of the encapsulated lipophilic Sudan Red (III) from 20 to 45 h. The microcapsules have controllable encapsulation and release characteristics for lipophilic compounds and are cost effective, making them suitable pesticides.