Processing of alumina-coated clay–diatomite composite membranes for oily wastewater treatment

Crack-free alumina-coated clay–diatomite composite membranes were successfully prepared by a simple pressing and dip-coating route using inexpensive raw materials at a temperature as low as 1000 °C in air. The changes of porosity, flexural strength, pore size, flux, and oil rejection rate of the membranes were investigated while changing the diatomite content. A simple burn-out process subjected to the used membranes in air completely recovered the specific surface area, steady state flux, and oil rejection rate of the virgin membranes. The recycled membranes showed an exceptionally high oil rejection rate (99.9%) with a feed oil concentration of 600 mg/L at an applied pressure of 101 kPa. The typical porosity, pore size, flexural strength, oil rejection rate, and steady state flux of the recycled alumina-coated clay–diatomite composite membrane were 36.5%, 0.12 μm, 32 MPa, 99.9%, and 6.91×10⁻⁶ m³ m⁻² s⁻¹, respectively, at an applied pressure of 101 kPa.     

Effect of boric acid on the porosity of clay and diatomite monoliths

Porous silica ceramics were obtained at low forming pressure (40–80 MPa) and low sintering temperature (850–1300 °C) for 4 h in air. Boric acid was used as a low-cost additive, in the amount of 2 wt%. Relatively high porosities of nearly 40% and 65% are obtained for the samples of clay and diatomite pressed at 40 MPa, and sintered at 1000 °C, respectively. The samples sintered at 1150 °C and 1300 °C have the average pore size diameters in the range of macroporous for clay 0.2–10 μm and for diatomite 0.2–5 μm. X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and mercury porosimetry measurements were employed to characterize of the obtained samples. Measurements of densities and open porosities by immersion technique were used, according to the Archimedes principle. The relations between mechanical characteristics of the samples formed by using different pressures and sintered at different temperature, were discussed.     

Preparation and characterization of low-cost ceramic microfiltration membranes for the removal of chromate from aqueous solutions

Low-cost ceramic microfiltration membranes were prepared using clay of IIT Guwahati. Two membranes were prepared by paste casting followed by sintering at different temperatures, the first one from clay only (membrane A) and the second one from clay with small amounts of sodium carbonate, sodium metasilicate and boric acid (membrane B). Both the membranes were characterized by TGA, SEM, XRD, water permeability test and acid–base treatment. With the increase of sintering temperature, pore size as well as permeability and flexural strength were increasing while porosity and pore density were decreasing. The overall performance of membrane B was better than membrane A. The average pore size, porosity, pore density and flexural strength of membrane B sintered at 1000 °C were 4.58 μm, 0.42, 2.06 × 10¹⁰ m^− 2 and 11.55 MPa respectively. This membrane was used for the removal of chromate from aqueous solutions by micellar enhanced microfiltration (MEMF) using cetylpyridinium chloride (CPC). 100% rejection of chromate ions were obtained at a feed ratio (CPC/chromate) of 10. Based on raw material prices, the membrane cost was estimated to be $19/m². The prepared low-cost membrane showed good promise for the treatment of wastewater containing such heavy metals.     

Preparation processes and characterizations of alumina-coated alumina support layers and alumina-coated natural material-based support layers for microfiltration

Recently, porous ceramic membranes have become a subject of significant interest due to their outstanding thermal and chemical stability. To reduce the high manufacturing costs of these porous ceramic membranes, recent research has focused on the utilization of inexpensive natural materials. However, there have not been any well-established direct comparisons of the membrane properties between typical alumina-based membranes and novel natural material-based membranes. Therefore, we compared alumina-coated alumina support layers (with average pore sizes ranging from 0.10 µm ~0.18 µm), alumina-coated diatomite-kaolin composite support layers (with an average pore size of 0.12 µm), and alumina-coated pyrophyllite-diatomite composite support layers (with an average pore size of 0.11 µm) via the dip-coating method and subsequent heat treatment ranging from 1200 °C–1400 °C for 1 h. The pure water permeability of the alumina-coated diatomite-kaolin composite support layer and the alumina-coated pyrophyllite-diatomite composite support layer was found to be approximately 2.0×10² L m⁻² h⁻¹ bar⁻¹, which is similar to that of an alumina-coated alumina support layer. Therefore, we suggest that the average pore size of an alumina-coated natural material-based support layer can be effectively controlled while exhibiting acceptable water permeability.     

High performance BaCe0.8Y0.2O3−a (BCY) hollow fibre membranes for hydrogen permeation

In this work, BaCe_0.8Y_0.2O_3−α (BCY) perovskite hollow fibre membranes were fabricated by a phase inversion and sintering method. BCY powder was prepared by the sol–gel technique using ethylenediaminetetraacetic acid (EDTA) and citric acid as the complexing agents. Gel calcination was carried out at high temperature to form the desired crystal structure. The qualified BCY hollow fibre membranes could not be achieved even the sintering was carried out at temperatures up to 1550^oC due to the poor densification behavior of the BCY material. The addition of sintering aid (1 wt% Co₂O₃) inside BCY powder as the membrane starting material significantly improved the densification process, leading to the formation of gas-tight BCY hollow fibres. The optimum sintering temperature of BCY hollow fibre membrane was 1400 °C to achieve the best mechanical strength. H₂ permeation through the BCY hollow fibre membranes was carried out between 700 and 1050 °C using 25% H₂–He mixture as feed gas and N₂ as sweep gas, respectively. For comparison purpose, the disk-shaped BCY membrane with a thickness of 1 mm was also prepared. The measured H₂ permeation flux through the BCY hollow fibres reached up to 0.38 mL cm⁻² min⁻¹ at 1050 °C strikingly contrasting to the low values of less than 0.01 mL cm⁻² min⁻¹ from the disk-shaped membrane. After the permeation test, the microstructure of BCY hollow fibre membrane was still maintained well without signals of membrane disintegration or peeling off.     

Effect of Nd-doping on structural,thermal and electrochemical properties of LaFe0.5Cr0.5O3 perovskites

The structural, thermal and electrochemical properties of the perovskite-type compound La_1−xNd_xFe_0.5Cr_0.5O₃ (x=0.10, 0.15, 0.20) are investigated by X-ray diffraction, thermal expansion, thermal diffusion, thermal conductivity and impedance spectroscopy measurements. Rietveld refinement shows that the compounds crystallize with orthorhombic symmetry in the space group Pbnm. The average thermal expansion coefficient decreases as the content of Nd increases. The average coefficient of thermal expansion in the temperature range of 30–850 °C is 10.12×10⁻⁶, 9.48×10⁻⁶ and 7.51×10⁻⁶ °C⁻¹ for samples with x=0.1, 0.15 and 0.2, respectively. Thermogravimetric analyses show small weight gain at high temperatures which correspond to filling up of oxygen vacancies as well as the valence change of the transition metals. The electrical conductivity measured by four-probe method shows that the conductivity increases with the content of Nd; the electrical conductivity at 520 °C is about 4.71×10⁻³, 6.59×10⁻³ and 9.62×10⁻³ S cm⁻¹ for samples with x=0.10, 0.15 and 0.20, respectively. The thermal diffusivity of the samples decreases monotonically as temperature increases. At 600 °C, the thermal diffusivity is 0.00425, 0.00455 and 0.00485 cm² s⁻¹ for samples with x=0.10, 0.15 and 0.20, respectively. Impedance measurements in symmetrical cell arrangement in air reveal that the polarization resistance decreases from 55 Ω cm⁻² to 22.5 Ω cm⁻² for increasing temperature from 800 °C to 900 °C, respectively.     

Preparation and characterization of porous MgAl2O4 spinel ceramic supports from bauxite and magnesite

Porous magnesium aluminate spinel (MgAl₂O₄) ceramic supports were fabricated by reactive sintering from low-cost bauxite and magnesite at different temperatures ranging from 1100 to 1400 °C and their sintering behavior and phase evolution were evaluated. The effects of sintering temperature on the pore structure, size and distribution as well as on the main properties of spinel ceramic supports such as flexural strength, nitrogen permeation flux and chemical resistance were investigated. The supports prepared at 1300 °C showed a homogeneous pore structure with the average pore size of 4.42 μm, and exhibited high flexural strength (35.6 MPa), high gas permeability (with nitrogen gas flux of 3057 m³ m⁻² h⁻¹ under a trans-membrane pressure of 0.1 MPa) and excellent chemical resistance.     

Dielectric and magnetic properties of Nickel ferrite ceramics using crystalline powders derived from DL alanine fuel in sol–gel auto-combustion

Dielectric and magnetic properties of NiFe₂O₄ ceramics prepared with powders using DL-alanine fuel in the sol–gel auto combustion technique are studied. DL-alanine fuel yields crystalline as-burnt powders, and when used for ceramic processing yields varying microstructure at different sintering temperatures. The dielectric properties are influenced by the resulting microstructure and the magnetic properties show slight change in saturation magnetization M_s (~44 – 46 emu/g). The coercive fields, dielectric losses and dispersion are reduced considerably at higher sintering temperatures (1200–1300 °C). The influence of changing microstructure is analyzed through dielectric response, complex impedance analysis and electrical modulus spectroscopy in the frequency range (10⁻²–10⁷ Hz) to understand the interactions from the grain and grain boundary phases. Sintering at 1200 °C, is found to be optimum, yields lower losses & reduced dielectric dispersion, and high resistivity (3.4×10⁸ Ω cm).     

The influence of mineral variability of Callovo-Oxfordian clay rocks on radionuclide transfer properties

The upper part of the Callovo-Oxfordian clay-rich rock formation (C2c unit) (Meuse/Haute-Marne, France) displays large variations in mineralogical composition of quartz, carbonate and clay minerals. This study deals with the effects of this composition variability on the diffusion-dominated transport properties of HTO (tritiated water)³, ³⁶Cl⁻ and ¹³⁷Cs⁺ for these rocks. Effective diffusion coefficients D_e and accessible porosities ε were determined using the through-diffusion method for a set of C2c unit samples characterized by a contrasted mineralogy especially in terms of clay mineral content (4–29%).The relative variations of the effective diffusion coefficients measured for HTO, ³⁶Cl⁻ and ¹³⁷Cs⁺ remain limited within a range of a factor 5 down to a clay mineral content of ~ 10%. In the range of clay mineral content higher than 15%, the effective diffusion coefficient tends to increase for ¹³⁷Cs⁺ and decreases for ³⁶Cl⁻ whereas D_e(HTO) stays relatively stable. Anion exclusion and surface enhanced diffusion for caesium were quantified and can explain this behaviour. Below 10% of clay minerals, these effective coefficients and the accessible porosities decreased drastically. For 4% of clay minerals, D_e were equal to 1.3 · 10^− 12 m² s^− 1 for HTO, 3.5 · 10^− 13 m² s^− 1 for ³⁶Cl⁻ and 7 · 10^− 12 m² s^− 1 for ¹³⁷Cs⁺. One of the main findings is that the anion exclusion and the enhanced diffusion for caesium still occur for the samples characterized by the lowest clay mineral contents. Finally, the set of diffusion data has been analysed against the well-known Archie's relation linking the accessible porosity to the effective diffusion coefficient.     

Effect of sintering temperature on microstructure and mechanical properties of zirconia-toughened alumina machinable dental ceramics

This study investigated the effect of sintering temperature on the microstructure and mechanical properties of dental zirconia-toughened alumina (ZTA) machinable ceramics. Six groups of gelcast ZTA ceramic samples sintered at temperatures between 1100 °C and 1450 °C were prepared. The microstructure was investigated by mercury intrusion porosimetry (MIP), X-ray diffraction (XRD), and scanning electron microscopy (SEM) techniques. The mechanical properties were characterized by flexural strength, fracture toughness, Vickers hardness, and machinability. Overall, with increasing temperature, the relative density, flexural strength, fracture toughness, and Vickers hardness values increased and more tetragonal ZrO₂ transformed into monoclinic ZrO₂; on the other hand, the porosity and pore size decreased. Significantly lower brittleness indexes were observed in groups sintered below 1300 °C, and the lowest values were observed at 1200 °C. The highest flexural strength and fracture toughness of ceramics reached 348.27 MPa and 5.23 MPa m^1/2 when sintered at 1450 °C, respectively. By considering the various properties of gelcast ZTA that varied with the sintering temperature, the optimal temperature for excellent machinability was determined to be approximately 1200–1250 °C, and in this range, a low brittleness index and moderate strength of 0.74–1.19 µm^−1/2 and 46.89–120.15 MPa, respectively, were realized.     

Preparation and characterization of mesoporous silicon oxycarbide ceramics without free carbon from polysiloxane

Mesoporous silicon oxycarbide ceramics without free carbon were prepared by pyrolysis of cross-linked polysiloxane at different temperatures (1300–1450 °C) followed by post treatments. The post treatments comprised two steps (HF etching and oxidation at 650 °C in air). The sample pyrolyzed at 1300 °C after post treatments exhibits the largest specific surface area (SSA) reaching up to 204 m²/g and the biggest total pore volume (0.58 cm³/g) with an average pore size of 11.4 nm. Increasing pyrolysis temperature will lead a quick decline of SSA and total pore volume. The thermal stability of pore structure of the sample pyrolyzed at 1300 °C with post treatments was investigated in air. The SSA and total pore volume almost keeps the same up to 750 °C, and subsequently decreases with a high speed. The most possible reason is the pores are severely closed by viscous flow of SiO₂ produced from SiC nanocrystallites.     

A novel low cost method for the synthesis of ceramic nano silicon oxycarbide powder

Although different methods have been used for manufacturing micro- Silicon Oxycarbide (SiOC) powder, there is no account of nano-SiOC synthesis in the literature. In this study, a novel low cost sol–gel method was used for the synthesis of nano-silicon oxycarbide (SiOC) powder. An organic–inorganic hybrid, i.e., a Tetraethyl Ortosilicate/Polydimethylsiloxane (TEOS/PDMS) mixture, was used as the starting material. The sol–gel technique was employed to cross-link the precursors using a base catalyst. Consequently, the gel was dried at 90 °C for 24 h. The dried gel was pyrolyzed in a two-step process in argon atmosphere. The synthesized powder was investigated using XRD, FTIR, TGA, FESEM and BET techniques. XRD and FTIR analyses identified the product to be SiOC. BET analysis showed a specific surface area of about 150 m²/g for the synthesized powder, thereby suggesting its nano-sized characteristics. FESEM studies further confirmed that the powder was nano-sized with an average particle size of about 50 nm. The proposed procedure could be, therefore, a simple low cost method for the synthesis of nano-SiOC powder.     

Nanoporous anatase ceramic membranes as fast-proton-conducting materials

Nanoporous anatase ceramic membranes were prepared via particulate sol–gel processes. The calcined xerogels were mesoporous, with a BET surface area of 121 m²/g, an average pore diameter of 5.8 nm and a pore volume of 0.236 cm³/g. Proton conductivity of the membranes was measured as a function of temperature and relative humidity, R.H. When anatase membranes are treated at pH 1.5, the proton conductivity increased in the whole range of temperature and R.H. It indicates that the surface site density (number of water molecules per square nanometer) of these materials has a strong effect on conductivity. The proton conductivity of the studied anatase membranes followed an Arrhenius-like dependence on the temperature (from room temperature to 90 °C), in both treated and untreated membranes. A sigmoidal dependence of the conductivity on the R.H. was observed with the greatest increase noted between 58 and 81% R.H. in both treated and untreated anatase membranes. The highest value of proton conductivity was found to be 0.015 S/cm at 90 °C and 81% R.H., for treated anatase ceramic membranes. An increase of the conductivity could be achieved by means of longer times of treatment.According to the activation energy values, proton migration in this kind of materials could be dominated by the Grotthuss mechanism in the whole range of R.H. The similar values of proton conductivity, lower cost and higher hydrophilicity of these membranes make them potential substitutes for perfluorosulfonic polymeric membranes in proton exchange membrane fuel cells (PEMFCs).     

Evaluating the photocatalytic activity of Pt/TNT film catalyst

TiO₂ nanotubes (TNT) were prepared by a hydrothermal method from the commercially available TiO₂-P25. Five types of TNT were produced at different temperatures (120 °C, 130 °C, and 150 °C) and by using different reaction times (12 h, 24 h, and 30 h). The photocatalytic reactor that was used is a film catalytic reactor, in which the height of the catalyst is 1.0 mm. The BET and FESEM analysis results showed that TNT130-24 (130 °C, 24 h) and TNT150-12 (150 °C, 12 h) possessed well-formed tubular structures with a high specific surface area (282.9–316.7 m² g⁻¹) and large pore volumes (0.62–0.70 cm³ g⁻¹). However, TNT120-30 (120 °C, 30 h) presented the best photocatalytic activity upon CO removal due to the synergistic effect of TiO₂ nanotubes and TiO₂ particles. After the TNT catalysts were modified with Pt particles, the removal efficiency was in the order of Pt/TNT120-30>Pt/TNT130-24>Pt/P25. Pt/TNT120-30 showed 99% removal efficiency in a continuous photoreactor with a high space velocity of 1.79×10⁴ h⁻¹. The results of the TEM and DRS analyses confirmed that the Pt particles enhanced the photocatalytic reaction, which was attributed to the well-dispersed nature of the 1 nm nanoscaled Pt particles on the surfaces of the TNT catalysts, and narrowed the band gap from 3.22 eV to 3.01 eV.     

Polymer-derived mesoporous Ni/SiOC(H) ceramic nanocomposites for efficient removal of acid fuchsin

In this paper, magnetic porous Ni-modified SiOC(H) ceramic nanocomposites (Ni/SiOC(H)) were successfully prepared via a template-free polymer-derived ceramic route, which involves pyrolysis at 600 °C of nickel-modified allylhydridopolycarbosilane (AHPCS-Ni) precursors synthesized by the reaction of allylhydridopolycarbosilane (AHPCS) with nickel(II)acetylacetonate (Ni(acac)₂). The resultant Ni/SiOC(H) nanocomposites are comprised of in-situ formed nanoscaled Ni socialized with small amounts of NiO and nickel silicides embedded in the amorphous SiOC(H) matrix. The materials show ferromagnetic behavior and excellent magnetic properties with the saturation magnetization in the range of 1.71–7.08 emu g⁻¹. Besides, the Ni/SiOC(H) nanocomposites are predominantly mesoporous with a high BET surface area and pore volume in the range of 253–344 and 0.134–0.185 cm³ g⁻¹, respectively. The measured porosity features cause an excellent adsorption capacity towards a template dye acid fuchsin with the adsorption capacity Q_t at 10 min of 80.7–85.8 mg g⁻¹ and the Q_e at equilibrium of 123.8–129.8 mg g⁻¹.     

Soft-templated mesoporous carbons as potential materials for oral drug delivery

Template-synthesized mesoporous carbons were successfully used in in vitro investigations of controlled delivery of three model drugs, captopril, furosemide, and ranitidine hydrochloride (HCl). Captopril and furosemide exhibited desorption kinetics over 30–40 h, and ranitidine. HCl had a complete release time of 5–10 h. As evident from the slow release kinetics, the mesoporous carbons have excellent potential for the controlled-release media of the specific drugs targeted towards oral delivery. The mesoporous carbons, synthesized from phloroglucinol and lignin, a synthetic and a sustainable precursor, respectively, exhibit BET surface area of 200–400 m² g⁻¹ and pore volume of 0.2–0.6 cm³ g⁻¹. The synthetic carbon has narrower pore widths and higher pore volume than the renewable counterpart and maintains a longer release time. The release kinetics reveals that the diffusivities of the drugs from carbon media are of equivalent magnitude (10⁻²² to 10⁻²⁴ m² s⁻¹). However, a tailored reduction of pore width in the sorbent reduces the diffusivity of smaller drug molecule by an order of magnitude. Thus, engineered pore morphology, along with its functionalization potential for specific interaction, can be exploited for optimal delivery system of a preferred drug.     

High-surface area carbons from renewable sources with a bimodal micro-mesoporosity for high-performance ionic liquid-based supercapacitors

Highly porous materials with a bimodal pore size distribution in the micro-mesopore range have been produced from biomass by adding melamine to the hydrochar/KOH mixture used in the activation process. These carbons are characterized by BET surface areas in excess of ∼3300 m² g⁻¹ and a porosity equally distributed between micropores and mesopores. The use of melamine in the synthesis process not only extends the pore size distribution into the mesopore region, but leads to the incorporation of a certain amount of nitrogen atoms into the carbon framework. These materials combine high ion adsorption capacities (micropores) and enhanced ion-transport kinetics (mesopores) leading to an outstanding capacitive performance in ionic liquid-based supercapacitors. Thus, they have specific capacitances >160 F g⁻¹ at 1 A g⁻¹ and >140 F g⁻¹ at 60 A g⁻¹ in both pure ionic liquid and in acetonitrile-diluted ionic liquid, enabling these materials to store up to a maximum of ca. 60 W h kg⁻¹ in both kinds of electrolytes and deliver ca. 20 W h kg⁻¹ at ∼42 kW kg⁻¹ (discharge time ca. 2 s) in pure ionic liquid and ∼25–30 W h kg⁻¹ at ∼97–100 kW kg⁻¹ (discharge time ∼1 s) in acetonitrile-diluted ionic liquid.     

Carbons with narrow pore size distribution prepared by simultaneous carbonization and self-activation of tobacco stems and their application to supercapacitors

Highly microporous carbons with narrow pore size distribution have been prepared by simultaneous carbonization and self-activation of tobacco wastes at temperatures ranging from 600 to 1000 °C. The efficiency of porosity development, without pores broadening, is attributed to well-distributed alkalis at the molecular level in the tobacco precursor. With Burley tobacco, the BET specific surface area and average micropore size L₀ increased up to 800 °C (Burley 800), where the values reached maxima of 1749 m² g⁻¹ and 1.2 nm, respectively. At temperatures higher than 800 °C, annealing of the materials dominates and provokes a decrease of S_BET and L₀. Burley carbons were implemented in supercapacitors using 1 mol L⁻¹ aqueous Li₂SO₄ or 1 mol L⁻¹ TEABF₄ in acetonitrile. In both electrolytes, the capacitance of Burley carbons followed the same trend as S_BET and L₀. Burley 800 demonstrated outstanding capacitance values of 167 F g⁻¹ (at 0.8 V limit) and 141 F g⁻¹ (at 2.3 V limit) in 1 mol L⁻¹ aqueous Li₂SO₄ and 1 mol L⁻¹ TEABF₄, respectively. Such values, about 50% higher as compared to commercially available carbons, are attributed to the narrow pore size distribution of this carbon with a maximum of pores around 1.2 nm close to the size of solvated ions in these electrolytes.     

Sorption of heavy metal ions from aqueous solution by a novel cast PVA/TiO2 nanohybrid adsorbent functionalized with amine groups

Sorption of Cd(II), Ni(II) and U(VI) ions onto a novel cast PVA/TiO₂/APTES nanohybrid adsorbent with variations in adsorbent dose, pH, contact time, initial metal concentration and temperature has been investigated. The adsorbent were characterized by SEM and FTIR analysis. BET surface area, pore diameter and pore volume of adsorbent were 35.98 m² g⁻¹, 3.08 nm and 0.059 cm³ g⁻¹, respectively. The kinetic and equilibrium data were accurately described by the double-exponential and Freundlich models for all metals. The maximum sorption capacities were 49.0, 13.1 and 36.1 mg g⁻¹ for Cd(II), Ni(II) and U(VI) ions with pH of 5.5, 5 and 4.5, respectively. Thermodynamic studies showed that the sorption process was favored at higher temperature. The adsorbent can be easily regenerated after 5 cycles of sorption–desorption.     

Study on superabsorbent composites. IX: Synthesis,characterization and swelling behaviors of polyacrylamide/clay composites based on various clays

A series of clay-based superabsorbent composite from acrylamide (AM) and various clays, such as attapulgite, kaolinite, mica, vermiculate and Na⁺-montmorillonite, was prepared by free-radical aqueous polymerization, using N,N′-methylenebisacrylamide (MBA) as a crosslinker and ammonium persulfate (APS) as an initiator, and then saponified with sodium hydroxide solution. In this paper, the reaction mechanism and thermal stability of the superabsorbent composites incorporated with various clays were characterized by FTIR, XRD and TGA, respectively. The effects of clay kind and clay content on equilibrium water absorbency of these composites were also investigated and compared. In addition, the influences of clay kind on comprehensive swelling behaviors of the PAM/clay superabsorbent composites were studied. The results indicated that the introduced clays could influence physicochemical properties of obtained superabsorbent composites. Mica could improve thermal stability of corresponding superabsorbent composites to the highest degree comparing with the other clays. The PAM/clay superabsorbent composites incorporated with 10 wt% clay of various kinds were all endowed with equilibrium water absorbency of more than 1300 g g⁻¹. The equilibrium water absorbency decreases with increasing clay content and correlates with the kind of clay. Attapulgite-based superabsorbent composite was endowed with higher water absorbency in univalent cationic saline solution, however, the vermiculite- and the kaolinite-based ones acquired the highest water absorbency in CaCl₂ and FeCl₃ aqueous solution, respectively. Moreover, the superabsorbent composites incorporated with Na⁺-montmorillonite have higher swelling rate and that of doped with mica was endowed with higher reswelling capability.