Clay Modification Research Articles

Carbon dioxide adsorption studies on modified montmorillonite clay/reduced graphene oxide hybrids at low pressure

The effect of modification of Montmorillonite clay (MMT) and the development of its hybrid with reduced graphene oxide was studied for CO2 adsorption at low pressure. Novel polyphosphoric acid modified montmorillonite (PMMT) clay was synthesized by cation exchange reaction to improve the surface area and thereby improving the carbon dioxide adsorption capacity. The MMT clay, polyphosphoric acid modified clay (PMMT), and amino modified clay (AMMT) were hybridized with reduced graphene oxide (rGO) by in-situ hydrothermal reduction of graphite oxide for CO2 adsorption studies. The hybrids were characterized using X-ray diffraction (XRD) analysis, Fourier Transform Infrared (FTIR) analysis, Field Emission Scanning Electron Microscopic (FESEM) and Transmission Electron Microscopic (TEM) analyses. The Brunauer–Emmett–Teller (BET) surface area analysis confirmed a surface area of 50.7709 m²/g for PMMT/rGO hybrid, which was higher than that of MMT/rGO and AMMT/rGO hybrids. In general, all hybrids were active in CO2 adsorption at comparatively low pressure [ranging from 0 to 900 mmHg]. PMMT/rGO hybrid showed highest CO2 adsorption of 0.49 mmol/g and this was 42% more in CO2 adsorption when compared to other materials studied in this paper. The low pressure CO2 adsorption values obtained for PMMT/rGO hybrid was substantially good when compared to the literature results and this shows the importance of clay based materials for the development of efficient adsorbent for CO2.

Removal of anionic surfactants from aqueous solutions using Fe-aluminosilicate sorbents

Fe-aluminosilicate sorbents were obtained by modifying bentonite clay with iron polyoxocations and heat treatment at 400°C and 500°C. The specific surface of the sorbents determined by the method of low-temperature nitrogen adsorption was 118-136 m2 · g–1. The iron content in sorbents was equal 7.8 %. The adsorption properties of the obtained sorbents were studied with respect to anionic surfactants (sodium dodecyl sulfate and sodium dodecylbenzenesulfonate) in aqueous solutions. It was shown that the modification of clay leads to a significant increase in anion-exchange capacity. The value of the adsorption capacity was in good agreement with the increase in the number of the basic groups of Fe – OH and the value of the specific surface of the sorbents. Adsorption isotherms of sodium dodecyl sulfate on bentonite clay and on Fe –aluminosilicate sorbents are described by the Langmuir adsorption isotherm equation which describes monolayer adsorption on a homogeneous surface with a correlation coefficient of 1.000 at initial surfactant concentrations of 10-1000 mg · l–1. The adsorption capacity of Fe-aluminosilicate sorbents was more than 3 times higher than the capacity of the original clay in the adsorption of sodium dodecyl sulfate and was about 5 times higher in the adsorption of sodium dodecylbenzenesulfonate. The results of the study suggest that the Fe-aluminosilicate sorbents can be effective for removing anionic surfactants from wastewater.

Study of the Surface Charge of a Porous Clay Heterostructure (PCH) and Its Adsorption Capacity of Alkaline Metals

A Porous Clay Heterostructure (PCH) was prepared by chemical modification of a natural clay, by intercalation of a cationic surfactant. Its surface charge properties as well as its adsorption capacity for alkali metals were studied using a potentiometric titration method. The PCH developed a pH-dependent charge (sH), probably due to the presence of amphoteric silanol groups (SiO2) coming from the pillars of silica interlayered during the pillared process. The PCH presented a region of zero charge in the range of pH of 4.0 to 7.7. The sH acquired by the PCH was adjusted with good correlation to the electric double layer model of Gouy-Chapman (r2 = 0.9925). The surface charge conferred the PCH ion exchange capacity for the studied metals (Li, Na, K, Rb and Cs) at high pH values (10 < pH), in comparable quantities (3.5 to 6 meq/g) to some Dowex resins. The results of this study suggest that PCH could have applications in the recovery of toxic metals from waste waters.

Structural modification of nano bentonite by aluminum, iron pillarization and 3D growth of silica mesoporous framework for arsenic removal from gold mine wastewater.

The elevated contamination of arsenic species emitted from gold mine activities causes serious environmental problems. The modification of natural bentonite clay to obtain the adsorbent with high porosity, large surface area, and high adsorption capacity creates a new group of porous and heterostructure materials for immobilization of arsenic species from gold mine wastewater under alkaline condition, owing to the gold cyanidation process. There is a limited approach in alkaline mine wastewater, because of the negative surface charge of most adsorbents. In this research, the adsorbability of arsenic under synthetic and real alkaline wastewater was investigated for the first time. The Visual MINTEQ geochemical modeling software was applied to simulate the arsenic species under different pH, temperature and co-existing ions in mine wastewater obtained from dewatering unit in Zarshuran gold mine. Optimized parameters and better adsorbent were initially determined from synthetic alkaline wastewater, then the efficiency of the adsorption process in real alkaline mine wastewater was measured. In real wastewater treatment, the obtained adsorption efficiency higher than 70% with high reusability in the alkaline condition is an appropriated for only one step process. The major mechanism for adsorption was chemical with complexation in rapid and slow diffusion into the active sites.

The Effect of Processing and Clay Modifications on Properties of Pet/Nano Clay Nanocomposites

The Effect of Processing and Clay Modifications on Properties of Pet/Nano Clay Nanocomposites

Low-Cost Electrode Modification to Upgrade the Bioelectrocatalytic Oxidation of Tannery Wastewater Using Acclimated Activated Sludge

Effective and eco-friendly technologies are required for the treatment of tannery wastewater as its biological toxicity and large volume leads toground water pollution. Hydrophobic (unmodified carbon felt) and hydrophilic modified carbon felt with Linde Type A zeolite (LTA zeolite) and bentonite were examined for their effects on bacterial attachment, current generation, and tannery wastewater treatment efficiency. Chronoamperometry and cyclic voltammetry confirmed the higher electron transfer obtained with modified anodes. Maximum current densities of 24.5 and 27.9 A/m² were provided with LTA zeolite and bentonite-modified anodes, respectively, while the unmodified carbon felt gave a maximum current density of 16.9 A/m². Compared with hydrophobic unmodified carbon felt, hydrophilic modified electrodes increased the exploitation of the internal surface area of the 3D structure of the carbon felt by the electroactive biofilm. The study revealed 93.8 ± 1.7% and 96.3 ± 2.1% of chemical oxygen demand (COD) reduction for LTA zeolite and bentonite, respectively. Simultaneous chromium removal was achieved with values of 94.6 ± 3.6 and 97.5 ± 2.2 for LTA zeolite and bentonite, respectively. This study shows the potential approach of carbon felt clay modification for the efficient tannery wastewater treatment using bioelectrochemicals systems (BESs) accompanied with high current recovery.

Polyamine-Based Organo-Clays for Polluted Water Treatment: Effect of Polyamine Structure and Content.

Hybrid materials based on clays and polyamines are supposed to be efficient heavy metals sorbents due to the well-known adsorption behaviour of the clay matrix and to the coordination properties of un-protonated amino groups. For this purpose, a montmorillonite clay was modified with three different aliphatic polyamines: L6 and L10 have a linear structure with six and ten amino groups, respectively, while B14 is a branched polyamine with fourteen amino groups. Initial amine concentration was the main parameter investigated and data were fitted with Langmuir and Freundlich models. Interaction mechanisms between clay and amines were deeply investigated by different experimental techniques such as X-ray powder diffraction (XRD), thermal analysis measurements (DTG), Fourier Transform Infrared Spectroscopy (FT-IR) and diffuse reflectance (NIR) spectroscopy. Experimental results showed that the amount of amines efficiently immobilized in the solid phase can be increased by increasing the initial concentration of polyamines in the clay modification process. These data were best fitted by Freundlich model, indicating a presence of surface sites of different nature. In the resulting hybrid materials, neither the accessibility of the NH/NH2 groups of the amines, nor the accessibility of the structural OH of the clay was hindered. Several preliminary tests in La ions’ uptake and release from aqueous solution were also carried out. In the conditions used for this study, total metal ion removal was achieved at sufficiently low linear amine loadings (i.e., 0.45 mmol/gclay for the small L6 amine), suggesting that these hybrid materials are promising for the proposed application in environmental remediation.

Use 3-D tomography to reveal structural modification of bentonite-enriched clay by nonionic surfactants: Application of organo-clay composites to detoxify aflatoxin B1 in chickens.

Although nonionic surfactants are relatively eco-friendly compared with cationic and anionic surfactants, few studies have investigated their application in modified clay. Herein we prepared organo-clay composites (OCCs) by mixing bentonite-enriched clay (BEC) with nonionic surfactants (Brij 30 and Igepal CO-890) and determined if these modifications would enable chickens to detoxify aflatoxin B1 (AFB1). For the first time, in situ three-dimensional (3-D) microstructures of modified BEC was characterized in suspension using transmission X-ray microscopy. Although X-ray diffraction patterns indicated the expansion in the spacing between planes of atoms (basal spacing) of surfactant-modified BEC, 3-D images indicated shrinkage in its microscale porous framework with increasing surfactant additions from 1 to 30 wt%. Such declining trends in porous dimensions caused by the dehydration in interlayer galleries of clays positively correlated with sorption amounts of AFB1 on OCCs. After chickens had consumed amended feeds for 11 weeks, AFB1 concentrations in liver, kidney, and plasma were significantly lower than in the control treatment. Thus, we suggest using BEC with 1 wt% surfactant addition, an amendment to chicken feeds, to detoxify AFB1. Modifying BEC with nonionic surfactants show the promise in mitigating AFB1 accumulation in chickens, which should improve food safety and reduce environmental contamination.

Modification of Egyptian clay by different organic cations

Nowadays, clay minerals are used extensively in a wide range of applications as nano additives for polymeric materials. Nevertheless hydrophilic characteristics of the nano additives reduce their degree of compatibility with polymeric chains. To overcome this problem it is necessary to modify the clay in order to render its surface more organophilic prior to the intercalation of the polymeric chains between its layers. In this work the Egyptian natural clay mineral montmorillonite (MMT) was modified with two cationic organic modifiers, namely hexadecyltrimethylammonium (HDTMA) and tributyl hexadecyl phosphonium using two different procedures. The first, using the magnetic stirrer while the second using a high speed mixer at different mixing times from 0.5 up to 2.5 hr. The samples with and without organic modifiers were characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), thermogravimetric analysis (TGA), scanning electron microscope (SEM) and transmission electron microscope (TEM). XRD results revealed that the basal spacing of the organo-montmorillonite (OMMT) prepared using high speed mixer was larger than that using magenetic stirrer. The best result was obtained after 1.5 hr stirring in the high speed mixer. The modification of MMT was confirmed by FTIR as determined from –CH2 stretching vibration of the organic modifiers. The TGA analysis revealed that the MMT modified with tributyl hexadecyl phosphonium cation had high thermal stability than that modified with hexadecyl trimethyl ammonium cation. The amount of surfactants within organoclays were found to be found to be about 19 and 24%, respectively, for hexadecyl trimethyl ammonium bromide and tributyl hexadecyl phosphonium bromide. SEM demonstrated that the modified MMT exhibited a massive thin layered structure with some large flacks and some interlayer spaces. TEM images of the prepared organoclays showed exfoliated structure. This work proved to enhance the economical value of the Egyptian natural resources.

Rheological study on the invert emulsion fluids with organoclay at high aged temperatures

Invert emulsion fluids stabilized by organoclays are important for applications in thixotropic fluids and petrochemical industry, especially in the field of oil extraction. Among these applications, improvement of the rheological properties of invert emulsion fluids at high temperatures lacks detailed study. In the current work, three different organoclays, including organo-sepiolite (OSEP), organo-hectorite (OSHCA) and organo-montmorillonite (OMMT) were prepared through chemical modification of unmodified clays using DODMAC. The results of X-ray diffraction (XRD) and scanning electron microscopy (SEM) show that DODMAC is not only adsorbed on the surface of particles, but also inserted into the layers of OMMT and OSHCA. For OSEP particles, DODMAC can only be adsorbed on the surface of particles. Interestingly, the results of optical microscopy and rheology indicate that the OSHCA particle-stabilized invert emulsion fluid provides better rheological properties than the other two organoclays at high temperature. Such high rheological properties is ascribed to the weak flocculation of OSHCA particles. Due to its nonreactive Mg−OH surface groups, OSHCA maintains the rheology of high-temperature aged invert emulsions by reconstructing weak flocculation structure. On the other hand, on the particle surface of OMMT and OSEP, Al−OH may react with OH− under alkaline conditions, which will destroy the weak flocculation due to increased repulsion interaction. These results clearly shed light on the relationship between the performance of invert emulsion at high aged temperature and particle weak flocculation, and also are beneficial to the applications which need stable emulsion at high temperature.

Polyamidoamine as a clay modifier and curing agent in preparation of epoxy nanocomposites

In the present study the commercial multifunctional fatty acid polyamidoamine (PAA) was for the first time simultaneously applied as a curing agent and clay modifier for epoxy/clay nanocomposites (NC) based on diglycidyl ether of bisphenol A. The montmorillonite (Cloisite®Na+) was modified with different quantities of partially and fully protonated polyamidoamine. The NCs with 0.5 wt% novel organoclay were prepared by solution intercalation method. The major aims of this paper are investigations of the effects of the composition of PAA modified clays on structure, mechanical, barrier properties and corrosion stability on steel substrates of NCs were studied.The thermogravimetric, flame photometry and X-ray diffraction analyses confirmed the efficient modification of clay surface with polyamidoamine, predominantly located within layers. The NCs exhibited an intercalated/exfoliated morphology and the presence of free amino groups and increased content of modifier facilitated dispersion of clay particles within the polymer matrix, as shown by electron microscopy techniques (SEM, TEM). Under an optimized loading of PAA (molar quantity of total amino groups per clay cation exchange capacity of 1.75), the layers in stacks were separated by 5.0 nm and high number of individual layers was present in NC. Clay modified by PAA with free amino groups showed increased storage modulus in the rubbery state, glass transition temperature of NCs, while dumping factor was decreased. The tensile test confirmed that introduction of flexible modifier on the epoxy/clay interface lead to increase in the ultimate tensile strenght and elongation at break by 31% and toughness up to 83%. The electrochemical impedance spectroscopy and permeability tests proved the pronounced barrier effect of clay particles against corrosive species and water vapor when high dispersion degree of clay in NC was achieved.

Removal of Fe and Mn From Polluted Water Sources in Lesotho Using Modified Clays

This paper reports the use of unfunctionalized and phenylalanine functionalized clays as an alternative cost effective, environmental friendly and efficient sorbent for the removal of Mn and Fe from polluted drinking water sources in Lesotho. The Mn and Fe metals were adsorbed on two different clays (clay A—a black clay and clay B—a yellow clay) collected from Ha-Teko in Maseru (clay A) and Phoqoane in Mafeteng district (clay B). Comprehensive batch test studies were performed to assess the effect of pH, stirring time and initial concentration of Mn and Fe. The adsorption of the metals was greater at higher pH and equilibrium was reached at pH 8 after 30 min of stirring. The phenylalanine functionalized clays displayed improved adsorption efficiency of up 100% (Fe adsorption using clay A in 30 min) while the unfunctionalized clays gave relatively low adsorption of up to 70% (Fe and Mn adsorption using clay A). The clays, which are present in abundance in Lesotho, can be effectively used for the removal of Fe and Mn from drinking water sources.

A critical review of clay-based composites with enhanced adsorption performance for metal and organic pollutants.

Adsorption techniques offer unique advantages owing to the use of synthetic (e.g., nanosized metal oxides and polymer-functionalized nanocomposites) and natural (e.g., clay and biochar) materials for pollutant removal. Although the most widely used adsorbent is activated carbon, extensive studies have highlighted the promising potential of modified clay minerals and biochar for removing heavy metal and organic pollutants from industrial, drinking, and eutrophic wastewater, due to their low cost and easy accessibility. However, clay modification using acids, calcination, polymers, or surfactants exhibits relatively low absorption/regeneration ability towards antibiotics, aromatics, and various dyes. The coexistence of numerous contaminants in industrial wastewater inhibited the performance of adsorbents, which accelerated the development of novel modified clay composites such as clay-biochar, organo-bentonite/sodium alginate beads, and enhanced biochar. This review summarizes recent studies and absorption mechanisms concerning clay composites based on various modification methods and component materials. The comparison of clay composites used for the removal of organic and inorganic contaminants provides valuable insight into real wastewater treatment. Knowledge gaps, uncertainties, and future challenges involved in the fabrication and regeneration of modified clay composites are also identified.

Mechanical Assisted Modification of Halloysite Nano Clay: Characterization and Its Effect on Mechanical Properties of Halloysite-Epoxy Nano Composites

Modificationof Halloysite nano clay has been done using 3-aminopropyltriethoxysilane in the presence of distilled water as solvent media. Untreated and modified nano clay was characterized by Powder X-ray diffractometer (PXRD), Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FT-IR). Functionalization of Halloysite nano clay is also strongly affected the morphological parameters and enabling the application in epoxy nano composite. However, the influence of modified clay concentration on the mechanical properties of epoxy/nanoclay composites, with different concentrations (2%, 3%, 4% and 5%) of nano clay in the epoxy resin was investigated. Experimental results showed that the mechanical properties of epoxy were improved upto 4 wt% of HNP’s, evidently because of the loading of modified clay. The tensile strength, tensile Modulus, flexural strength, flexural modulusand fracture toughness of the nanocomposites increased by 13%, 17%, 9%, 14%and 27% respectivelythis demonstrated that the composites were strengthened.

Hydrophobic Sorbent of Silica Clay

The paper presents the results of a study of the physicochemical and sorption characteristics of the modified silica clay. It is established that the modification of the silica clay provides an increase in the hydrophobicity, specific surface, and porosity of the sorbent, and also increases its capacity in petroleum absorption. It was found out that the modified silica clay is a highly effective sorbent with respect to emulsified petroleum products. The sorption activity of the modified silica clay on petroleum products was estimated using sorption isotherms.

Modification of montmorillonite clay with Cymbopogon citratus for the decontamination of zearalenone in millet

Montmorillonite clay due to its abundance and environmental friendliness, has several industrial applications among which is the adsorption of mycotoxins in foods and feeds as binding agents. Fungal species from the genus Fusarium produce zearalenone (ZEA); an oestrogenic compound, which has been implicated in hormonal and reproductive issues for both animal and man. In this study, various nanoformulations from montmorillonite clay and Cymbopogon citratus (lemongrass) extracts were developed for the decontamination of ZEA in millet. The various formulations developed included montmorillonite clay and essential oil of Cymbopogon citratus (Mont-LGEO), montmorillonite clay mixed with C. citratus (lemongrass) powder (Mont-LGP) and montmorillonite clay washed with 1 mM NaCl (Mont-Na). Unmodified montmorillonite clay (Mont) and C. citratus (lemongrass powder) (LGP) served as the negative controls for the treatment. Each of the formulations was exposed to millet grains at concentrations of 8 and 12% and stored for 4 weeks. All the formulations were effective in the decontamination of ZEA in millet after 4 weeks with LGP exposed at 12% recording the highest reduction of 98.3% while the second most effective formulation, Mont-LGP exposed at 12% showed a 66% reduction of ZEA in millet (p = 0.05).

Polymer Composite Film Based on Polyethylene and Organoclay

Clay is an inorganic material with hydrophilic surface which cannot interact well with hydrophobic polymer as a reinforcement filler phase. However, surface modification allows useful applications as fillers in composite fabrication with most hydrophobic polymers. To achieve this, native clay was activated by mineral acids, modified through acetylation using commercial vinegar to convert the hydrophilic clay surface to hydrophobic one, capable of interaction with polyethylene. The formulated composite films were biodegraded after one month of test experiment carried out at different locations. Scanning electron microscopy analysis of composite films evidently showed that surface compatible, dispersible and exfoliated type composites were formed. FT-IR spectroscopy revealed the presence of C=O, -COO-, -CH3 and -C-CH3 due to acetylation. Absorption studies using water, acid/base show that the composite films exhibited good resistance to these solvents. Biodegradation studies showed high microbial activities with samples buried at refuse dump sites. EDX results revealed the presence of kaolinite and montmorillonite as major minerals, whereas radioactive elements were detected in the studied clay. This study demonstrated the useful application of commercial vinegar for the modification of clay for better surface interaction with polyethylene for composite formulation.

Testing of brick clay modifications as a raw material for building ceramic products

Brick clay is nowadays modified by various procedures to achieve the best properties when used for building ceramic products. In the treatment of these clays, the properties are regulated by changing the quantity of water, sharpening, lightening, venting, settling, using additives, but also by consistent homogenization, crushing, grinding and mixing. This article compares several clay bricks before and after treatment and also compares them with ceramic clay. Comparative parameters are bulk density, porosity, water absorption, compressive strength and flexural strength, long-term changes in burning and weight loss by burning.

Porous aluminosilicic solids obtained by thermal-acid modification of a commercial kaolinite-type natural clay

Transformation of natural clay minerals is an interesting way to design new microporous solids with potential applications as adsorbents or heterogeneous catalysts. Particularly, kaolinite is a widely commercialized 1:1 clay mineral of promising modifiable structure. This paper reports the preparation of microporous solids with high surface areas and increased acidity by thermal-acid treatments of a natural kaolinite. Previous heating (700 °C and 900 °C) was used to activate the kaolinite (23 m2/g surface area) and produce metakaolinite. Then, aluminum extraction with 3 M HCl solution yielded solids with 320 m2/g and 526 m2/g micropore surface areas. The successful dissolution of Al3+ ions from the kaolinite octahedral sheets produces strong dealuminized solids with superior acidity (Brönsted and Lewis). The remarkable characteristics of these solids (high thermal stability, high porosity and enhanced acidity) allow considering them as important catalytic supports.

Surfactant-based modification of sodic-Algerian illite clay for the preparation of polymeric membranes: application for separation of iron and zinc ions from aqueous solutions

In the present work, polymer solutions of cellulose triacetate (CTA) and tris-ethylhexyl phosphate (TEHP) mixed with Algerian green illite clay were used to prepare selective filtration membranes by the phase inversion technique via immersion precipitation. The effect of a local clay additive on the structure and performances of the membranes was studied. Algerian clay was characterized by x-ray diffraction (XRD), thermogravimetric analysis (TGA), x-ray fluorescence (XRF) and scanning electron microscopy (SEM). The obtained hybrid membranes were characterized by XRD, Fourier transform infrared spectroscopy (FTIR-ATR), TGA and contact angle measurements. All the synthesized membranes had an amorphous structure without any diffraction peak. This could be due to the absence of crystallization within the membrane. As the plasticizer molecules were hydrophobic, their location at the surface of the modified polymeric membranes is expected to modify the contact angle. Overall, our results show that the addition of plasticizer to the hybrid material (polymer and clay) results in homogeneous and hydrophobic membranes of which the physical properties were ameliorated compared to (CTA + Clay) membranes. As applications, transport of Zn(II) and Fe(III) in polymeric membranes using (CTA + TEHP + Clay) membranes was studied.