This work presents the results of the physical characterization of palygorskite and its adsorptive behaviour for three solvatochromic dyes (Nile blue chloride (NBC), methylene blue (MTB) and dithizone (DTZ)). Adsorption isotherms were used to determine the maximum adsorption of the solvatochromic dyes on the palygorskite. The characterization of palygorskite was carried out via mineralogical and chemical analysis with X-ray diffraction, X-ray fluorescence, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy, surface-charge measurement (ζ-potential), thermogravimetric analysis, textural analysis and cation-exchange capacity analysis. The material consists of palygorskite and quartz and its chemistry is dominated by SiO2, MgO and Fe2O3. The specific surface area and cation-exchange capacity of the palygorskite are 142 m2 g–1 and 41 cmol(+) kg–1, respectively. The SEM and TEM analyses showed a fibrous structure with fibres 20–100 nm long. The thermogravimetric analysis showed three endothermic events at 57.3°C, 171.8°C and 439.6°C. The adsorption capacities of the palygorskite for NBC (basic pH), MTB (basic pH) and DTZ (neutral pH) were 0.082, 0.013 and 0.102 g g–1, respectively. The adsorptions of NBC and MTB were fitted with the Langmuir isotherm model and the adsorption of DTZ was fitted with the Sips model.

This work determines the optimal palygorskite (Plg) content (maximum surfactant adsorption point) to achieve organophilization using the cationic surfactant cetyltrimethyl ammonium bromide (CTAB) at various concentrations. Adsorption assays were carried out in a finite bath after varying the content of Plg and CTAB in solution. In those assays, the effects of time, temperature, pH and thermodynamic characteristics were studied. The results were analysed using the Langmuir, Freundlich, Dubinin–Radushkevich and Tempkin adsorption models. The increase in clay content in the dispersion leads to a decrease in adsorption of surfactant on the clay. It was possible to obtain the optimal Plg content to achieve organophilization at various concentrations of CTAB surfactant. The experimental data fitted well to the Freundlich model. The Dubinin–Radushkevich and Tempkin isotherms confirmed the chemical adsorption of CTAB on Plg clay.

The ability of Na+-, Li+-, K+-, Ca2+- and Mg2+-exchanged sepiolites and acid-activated sepiolites to remove ethylene from storage environments was examined. The sepiolite from Sivrihisar deposit, Turkey, was treated with 1.0 M NaNO3, LiNO3, KNO3, Ca(NO3)2, Mg(NO3)2, HNO3 and H2SO4 solutions at 90°C for 4 h. The mineralogical, chemical and textural properties of the materials were examined using X-ray diffraction, X-ray fluorescence, cation-exchange capacity and nitrogen gas adsorption analyses. The main mineral phase present in the materials was sepiolite, with minor dolomite, and traces of quartz and feldspar minerals and amorphous matter. Adsorption isotherms of ethylene at 273 K were measured on sepiolite samples over a pressure range of 0–100 kPa. As a result of partial blockage of the sepiolite channels, the ethylene adsorption capacity on cation-exchanged sepiolite forms (0.376–0.907 mmol g–1) was less than that of acid-activated sepiolite forms (1.279 and 1.308 mmol g–1). The ethylene adsorption capacities of the sepiolite samples were compared with those of other clay-based materials (0.167–1.817 mmol g–1) reported in previous studies of ethylene removal.

Nitrate contamination of surface waters and groundwater is one of the main problems associated with agricultural activities worldwide, and there is an urgent need to develop effective materials and processes to remove efficiently excess nitrate from aquatic environments. Bittern is a seawater resource that contains large amounts of Mg2+ and Ca2+, and its utilization has received much recent attention. In this study, an Fe-type layered double hydroxide (Fe-LDH) product was prepared from bittern with the addition of an inexpensive agent (FeCl3) for nitrate removal. The greatest nitrate removal was obtained for synthesis conditions of pH 8.5–9.5 at 50°C for 0.5 h. The equilibrium adsorption capacity of the product for nitrate was measured and fitted with the Langmuir and Freundlich isotherm models. The experimental data better fit the Langmuir model than the Freundlich model. The calculated maximum adsorption capacity for nitrate was 0.40 mmol g–1, which was greater than those of other reported nitrate adsorbents. The product removed nitrate ions from a highly saline solution. The order of interference of anion species for nitrate removal was CO32– > SO42– > Br– > NO2– > Cl– > F–. The pH of the solution and removal of nitrate increased with increasing solution temperature because of ion exchange between the Cl– in Fe-LDH and the NO3– in the solution. Nitrate ions were repeatedly adsorbed and desorbed. The prepared Fe-LDH is expected to be a new inorganic anion exchanger for the removal and recovery of nitrate ions from aquatic environments.

Acid activation was carried out by heating muds prepared from Ca-rich bentonite (CaB), sulfuric acid (H2SO4) and distilled water, yielding various bleaching earths (BEs). The roles of each of the process variables, namely mass fraction of H2SO4 (x) in the dried CaB and pure H2SO4 mixture, heating temperature (T) and contact time (t), in the activation were tested. The raw CaB and each BE were examined with X-ray diffraction, chemical analyses, N2 adsorption/desorption, pH-metry and tintometry. The BE contents in both the aqueous and oily suspensions were set to 2% by mass in order to measure the pH value and the bleaching power, respectively. The optimum conditions for the activation to obtain a BE having the same bleaching power (0.60) as Tonsil® Optimum Bleaching Earth for soybean oil were determined as x = 0.35, T = 100°C and t = 2 h. The bleaching power increased only marginally upon increasing the activation time from 2 h up to 10 h at a given x and T. After 10 h, significant changes did not take place in the bleaching power of the BE. The mass fraction of total structural metal oxide (y), pH value, specific pore volume (V), specific surface area (S) and mean internal diameter (D) of the mesopores for the optimized BE are y = 0.10, pH = 3.0, V = 0.31 cm3 g–1, S = 225 m2 g–1 and D = 7 nm. The pH and D values were more important for bleaching the alkaline refined soybean oil compared to the other parameters tested.

Sediments from the ST5 deep-sea bottom core collected from the south-east Aegean Sea between Symi and Tilos islands, Greece, were examined by quantitative mineralogical analysis and geochemical analysis to infer provenance and palaeoenvironmental control over sediment deposition. The mineralogical composition comprises carbonates (mainly calcite and Mg-calcite), quartz, feldspars, serpentine, amphibole and clay minerals. Chlorite is the most abundant clay mineral, whereas smectite and illite are less abundant than in the sediments in the south-west Aegean and the Cretan Sea. Semi-quantitative analysis of clay minerals from oriented clay fractions overestimates significantly the smectite content and underestimates the abundances of illite, chlorite and kaolinite. The studied sediments are enriched in MgO, Ni and Cr, which decrease in abundance with decreasing depth, following the distribution of serpentine. By contrast, the abundances of SiO2, Al2O3, Fe2O3, Na2O and K2O increase upcore. The regional S1 sapropel horizon is enriched in V and Co and has considerably greater Ba/Al ratios than the remaining sequence. The mineralogical and geochemical relationships indicate a strong ultrabasic influence, probably from the Marmaris ophiolite in the Lycian nappes. The clay mineral distribution suggests that the smectite was mainly of volcanogenic origin, the illite was supplied by the nearby landmasses of west Anatolia and the islands of Rhodes, Tilos and Symi and the contribution from the south-east Mediterranean was limited or totally lacking. The combined use of the mineralogical and geochemical analysis of bulk sediments rather than the clay fractions is not only extremely useful in tracing sediment provenance in relatively closed basins, but it also enables a more realistic assessment of the importance of water circulation patterns on sedimentation processes in such environments.

Steam jet milling was applied for the first time to ultra-fine grind the filter cake (moisture content 23.80%) produced by a kaolin concentrator. The material was dehydrated and dried simultaneously during grinding, and the final ground sample met the moisture content requirement for powder products of <2%. The particle size of the ground kaolin samples decreased and the particle-size distribution was more concentrated, indicating that the steam jet milling was more effective for kaolin processing than the conventional dry grinding process. In addition, steam jet milling can improve the whiteness and decrease the crystal order of the samples, thus improving the kaolin properties in follow-up applications.

Geopolymers can be transformed into zeolites under certain synthesis conditions. However, zeolite formation is not frequently reported in KOH-activated geopolymers. This study attempted to explore zeolite synthesis through geopolymerization for a curing time of 24 h using mixed NaOH/KOH alkaline solution as an activator, and then applying the geopolymer-supported zeolites to immobilize Cd(II) in paddy soil. The K2O/M2O–H2O/SiO2 and K2O/M2O–OH–/SiO2 binary zeolite crystallization phase diagrams were obtained. Zeolite A, faujasite and sodalite formed at lower K2O/M2O molar ratios (0–0.2), ferrierite formation was favoured at a K2O/M2O molar ratio of 0.2–0.4 and zeolite K-I and zeolite F-K (both K-zeolites) were observed at a K2O/M2O molar ratio of 0.6. The geopolymer-supported zeolites had micropores and mesopores and specific surface area values of 44.2–74.8 m2 g–1. The material displayed a considerable Cd(II) immobilization efficiency (55.6–58.7% at 4–6 wt.% addition of zeolite).

Tungstophosphoric acid-intercalated MgAl layer double hydroxides (LDHs) are active catalysts for removing naphthenic acids (NAs) from petroleum via esterification. Due to their active sites being in the interlayer, the interlayer spacing of LDHs might affect their activity, particularly for NAs with various structures. Herein, two tungstophosphoric acid-intercalated MgAl LDHs with various interlayer spacings (d003 = 1.46 and 1.07 nm) synthesized by varying the ion-exchange time were used as catalysts for esterification between NAs and ethylene glycol. Six NAs with various side chains and rings were used as model compounds to investigate the effects of NA structures and d003 values on the activity of LDHs. In general, NAs with large molecule sizes and steric hindrances are less reactive over the same catalyst. The LDH with a larger d003 value favours the esterification of NAs regardless of their structure, particularly NAs with large molecule sizes and steric hindrances. However, a large d003 is less effective for esterification of NAs with conjugated carboxyl groups. An enlarged interlayer space might facilitate NA molecules to access the interlayer of LDHs so as to come into contact with the catalytic sites, making this process responsible for the enhanced reactivity. The esterification kinetics of cyclohexanecarboxylic acid over these LDHs follow a first-order reaction. The activation energies for the LDHs with large and small d003 values are 26.25 and 32.18 kJ mol–1, respectively.