Unmodified Clay Research Articles

Adsorption of nickel (II) from aqueous solutions with clay-supported nano-scale zero-valent iron synthesized from green tea extract

Nano zerovalent iron (nZVI) supported adsorbents have been reported as suitable candidates for adsorption of water contaminants. However, the role of and interplay between surface chemistry, functional group density and textural properties has largely been unexplored. In this work, green tea derived nano zerovalent iron (nZVI) supported clay hybrid material (CnZVI) was used as a novel adsorbent for the removal of Ni2+ ions from water. The unmodified natural clay (Arg) and the CnZVI composite were characterized using FTIR, SEM, TGA and BET techniques. Incorporation of nZVI ameliorated the specific surface area from 16.88 to 30.46 m2/g, translating to ∼80 % increase. This translated to ∼69 % increase in maximum adsorption capacity from 8.47 to 14.38 mg/g, respectively. The addition of nZVI in the clay decreased the affinity (KF) for Ni2+ by ∼48 %. The disparity between the percent increase in surface area (∼80 %) and the adsorption capacity (∼69 %) implies the adsorption of Ni2+ was significantly controlled by textural properties compensating for the antagonistic effects of functional group density. The kinetic rates were best predicted by the pseudo-first-order and Elovich’s models for the Arg and CnZVI, respectively, implicit evidence of the role of surface chemistry. A maximum adsorption capacity of 14 mg/g was achieved for 100 mg Ni2+/L in 120 min for CnZVI.

Enhanced fluoride removal from water using acid-modified red clay soil from the Loess Plateau of China

ABSTRACT The discharge of fluoride-containing wastewater poses a severe threat to global water resources, ecosystems, and human health. Urgently needed are economically feasible and environmentally sustainable solutions for worldwide fluoride contamination. This study explores utilizing unmodified and modified red clay soils from China's Loess Plateau as adsorbents for fluoride mitigation. Sulfuric acid-modified red clay soil showed higher fluoride removal than unmodified, NaOH-modified, and thermally modified soils. Fluoride adsorption decreased with rising pH from 2.0 to 10.0 for unmodified (67.67–3.91%) and acid-modified red clay soil (90.44–32.06%). The Langmuir model better described the data (R2 = 0.9821, 0.9901 for unmodified, acid-modified soil), improving maximum adsorption capacity by 252%. Pseudo-second-order kinetics (R2 = 0.9925, 0.9954 for unmodified, acid-modified soil) accurately described the kinetic data. Acid modification improved reaction rates, shortening the breakpoint from 6.694 to 2.318 min1/2. Over time, the process transitioned from intraparticle diffusion to external mass transfer and intraparticle diffusion. FTIR analysis showed that acid modification strengthened ligand exchange and provided ion exchange opportunities. This study advances fluoride adsorption through innovative clay soil utilization, offering economical, viable, and environmentally friendly solutions.

Influence of Hydrothermal Modification on Adsorptive Performance of Clay Minerals for Malachite Green.

Artificially modified adsorbing materials mainly aim to remedy the disadvantages of natural materials as much as possible. Using clay materials such as rectorite, sodium bentonite and metakaolinite (solid waste material) as base materials, hydrothermally modified and unmodified materials were compared. CM-HT and CM (adsorbing materials) were prepared and used to adsorb and purify wastewater containing malachite green (MG) dye, and the two materials were characterized through methods such as BET, FT-IR, SEM and XRD. Results: (1) The optimal conditions for hydrothermal modification of CM-HT were a temperature of 150 °C, a time of 2 h, and a liquid/solid ratio 1:20. (2) Hydrothermal modification greatly increased the adsorptive effect. The measured maximum adsorption capacity of CM-HT for MG reached 290.45 mg/g (56.92% higher than that of CM). The theoretical maximum capacity was 625.15 mg/g (186.15% higher than that of CM). (3) Because Al-OH and Si-O-Al groups were reserved in unmodified clay mineral adsorbing materials with good adsorbing activity, after hydrothermal modification, the crystal structure of the clay became loosened along the direction of the c axis, and the interlayer space increased to partially exchange interlayer metal cations connected to the bottom oxygen, giving CM-HT higher electronegativity and creating more crystal defects and chemically active adsorbing sites for high-performance adsorption. (4) Chemical adsorption was the primary way by which CM-HT adsorbed cationic dye, while physical adsorption caused by developed pore canal was secondary. The adsorption reaction occurred spontaneously.

Kinetic, adsorption, and thermodynamic study of removal of Cr6+ by iron-rich natural clay minerals

The study explores the adsorption behavior of unmodified natural clay as an ecologically acceptable procedure in the treatment of toxic elements such as Cr6+ in wastewater. Batch experiments were conducted by stirring 30 ml of a Cr6+ solution and natural clay for 3 h at different temperatures, pH, Cr6+ loadings, and concentrations. Characterization of natural clay before and after adsorption was studied by XRD, FTIR, and BET for surface area, SEM, and EDX for surface topography. The Cr6+ content was analyzed by UV–visible spectrophotometer further, the mechanism of the process was illustrated by isotherm and kinetic studies. Cr6+ maximum sorption capacity obtained was 12.3 mg/g at pH 3. The overall process followed the Langmuir model elucidating monolayer adsorption as a major, in addition kinetics study (pseudo-2nd-order) describes accurately that chemisorption is a rate-controlling stage. Thermodynamics measurements indicated a spontaneous and endothermic process involved throughout the adsorption. Therefore, the study highlights the efficacy of unmodified natural clay as an efficient adsorbent for the elimination of Cr6+ from aqueous solution.

Detailed study of Safranin-O adsorption on sepiolite clay: Kinetics, thermodynamics, isotherms and theoretical calculations for optimal water treatment efficiency

Large-scale pollution requires industrial waste management policy. This study describes the adsorptive removal process for the cationic dye Safranin-O (Sfr), known for its high toxicity, using a natural, chemically unmodified clay classified as a fibrous clay, namely sepiolite. This adsorbent was thoroughly characterized using a variety of techniques, including Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy with X-ray energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), X-ray fluorescence (FX), zero charge point analysis (pHZCP) and Zeta potential. The kinetic study showed that adsorption followed pseudo-second-order kinetics associated with a mixed diffusion process including bulk and intra-particle diffusion. The adsorption process reached equilibrium within 300 min. Sorption isotherm models fitted the experimental data in the order: M-J (four parameters) > F-S V (five parameters) > F-S IV (four parameters) > Sips (three parameters) ≈ Hill (three parameters) > R-P (three parameters) > Freundlich (2 parameters) > Langmuir (2 parameters). The maximum adsorption capacity estimated by the Langmuir model was approximately 233.81 mg/g. Analysis of the thermodynamic parameters highlighted adsorption as a spontaneous, physical and exothermic process by nature, underlining the preponderance of randomness at the adsorbent surface. In addition, DFT calculations followed by some electronic parameters linked to the Sfr dye were studied. Topological characteristics such as Localised Orbital Locator (LOL), Electron Localisation Function (ELF), Visualizing Molecular Dynamics (VMD), and Reduced Density Gradient (RDG) were discussed using the multiwave function (Multiwfn) in liquid phase. Monte Carlo (MC) simulation models were conducted to probe the interaction and mechanism between the fibrous clay fraction surface and the Sfr dye. Overall, sepiolite, due to its abundance, low cost, efficiency and environmental safety, is emerging as a promising adsorbent for the treatment of wastewater containing harmful dyes.

Surface Modification of Montmorillonite Clay Towards the Fabrication of Nanocomposites for Engineering Applications

Montmorillonite (MMT) is a layered clay mineral composed of silica and alumina sheets with a layer thickness of about 1 nm qualifies it as a two-dimensional nanomaterial. MMT is found in natural clay ores in the Murunkan, Kirinda, and Okanda areas in Sri Lanka. Nanocomposites with enhanced physical and mechanical properties can be prepared by dispersing MMT in a polymer matrix. However, the hydrophilic nature of MMT hinders the incorporation of MMT into hydrophobic polymer matrices. Hence, a suitable surface modification is required to make MMT compatible with polymers. The present study was based on the preparation and analysis of organically modified calcium Montmorillonite (Ca-MMT)-polypropylene nanocomposites as a green technology initiative. Homo-ionic Ca-MMT was prepared by treating commercial MMT-K10 with a CaCl2 solution. The predominant exchangeable divalent cations present in MMT-K10 and Ca-MMT were determined using AAS. The cation exchange capacity of Ca-MMT was about two times greater than that of MMT-K10. Furthermore, XRD analysis showed a slight increase in d- spacing of Ca-MMT compared to MMT-K10. A novel ligand, triethylene glycol dodecyl methyl ether was synthesized by treating triethylene glycol monomethyl ether (TGME) with 50% w/w aqueous solution of sodium hydroxide followed by 1-bromododecane with the molar ratio of TGME:NaOH:1-bromododecane in 1:2:2. The crude product was purified by column chromatography and characterized by FTIR and GCMS analysis. Hydrophilic Ca-MMT was surface modified with the organic ligand presumably via the coordination of triethylene glycol moiety with Ca2+ cations at the outer edge of the MMT particles. The long aliphatic chains in the periphery of the modified MMT particle make it more organophilic. Modified Ca-MMT was characterized by XRD, TGA, and FTIR analysis. The XRD revealed a slight increase in the d-spacing related to the 001 plane of modified Ca-MMT compared to unmodified clay. The effect of modified Ca-MMT loadings (0.5%, 1%, and 1.5%) on the mechanical properties of the nanocomposite was studied. The results implied an enhancement of the mechanical properties in terms of impact resistance, hardness, and flexural properties in the nanocomposite compared to the virgin polymer. The fabricated nanocomposite is a promising engineering material that may have applications in automotive, construction, and packaging products.
 
 Keywords: Montmorillonite, Polypropylene, Nanocomposite, TGME, Compatibility

NATURAL CLAY MINERALS FOR REMOVAL OF CATIONIC DYE: KINETIC, ADSORPTION, AND THERMODYNAMIC STUDY

In recent years managing ecological changes and comprehending diverse anthropogenic contributions towards pollution is now of great concern due to industrialization. Therefore, creating an environmentally friendly solution for dealing with harmful substances like Methylene Blue in water has become a critical issue. This experimental investigation aims to design and assess the unmodified clay mineral of the Panchaganga River flood zone for the removal of MB by batch tests. The removal of MB was examined by optimizing all the variables, further XRD, SEM, EDX, BET, and FTIR, were all used to meticulously examine the NC before and after adsorption. Methylene Blue content was determined by UV-visible spectrophotometrically, and the mechanism of NC’s adsorption to MB in water was examined by modeling isotherm and kinetics studies. At pH 7.00 to 8.00, the NC showed a high extraction of MB due to negatively charged clay surface (Si-O- ), (Al-O- ). The adsorption capacity qm obtained was 88.8 mg/g (Langmuir). The kinetics study showed that the adsorption mechanism follows pseudo-2nd-order indicating chemisorption as a rate-determining step, moreover, adsorption also occurs via the intra-particle-diffusion process due to small pores on NC. The study demonstrates that the NC exhibits significant efficacy in efficiently removing the cationic dye (MB) pollutant from waste-water systems.

The Influence of the Used Bleaching Earth on the Content of Natural Dyes in Hemp (Cannabis sativa L.) Oils

Cold-pressed hemp oils are characterized by an intense color, which is undesirable when used directly. Therefore, research was undertaken on removing chlorophyll and carotenoids effectively. This publication presents the results of tests that verified the adsorption properties of seven bleaching earths (BE1–BE7) in two doses (2.5% and 5.0%) in the low-temperature bleaching process of hemp oils. These oils were obtained by cold and hot pressing of the seeds of three varieties of hemp (Cannabis sativa L.): Finola, Earlina 8FC, and Secuieni Jubileu. The color change and the content of carotenoid and chlorophyll pigments in the bleached oils were verified using the colorimetric method (CIE-Lab). The BEs used had different abilities to reduce the content of natural dyes connected with oil decolorization. The conducted research allowed us to characterize the influence of BEs on the organoleptic properties of the tested oils. Hemp oil obtained from the Secuieni Jubileu CP and HP hemp variety should be bleached with unmodified magnesian bentonite at 2.5%. Unmodified attapulgite clay is not recommended for this variety, as it strongly adsorbs carotenoids from the oil.

Modification and characterization of selected Zambian clays for potential use as photocatalysts

Natural materials such as clay are valued for their favorable physical and chemical characteristics on the surface. In this study, the selected Zambian clay materials are immobilized with TiO2 and manganese ions to determine their suitability for use as photocatalysts. SiO2 and Al2O3 oxide composition of Zambian clays was obtained in the range of 35.08-52.63/35.15-52.72 and 13.85-21.73/13.77-21.80, respectively, by inductively coupled plasma (ICP) and X-ray fluorescence (XRF); while Energy dispersive spectroscopy (EDS) of modified clays showed that they have 1.54% incorporation of Ti and 4.98% Mn for Chingola clay to act as UV-Vis absorbers. According to the powder X-ray diffraction analysis of raw clays, the primary phase of all samples is quartz and contains low concentrations of bentonite and kaolinite. The scanning electron microscope (SEM) showed fluffy morphology with agglomeration, while the particle sizes of the clay photocatalysts with the use of transmission electron microscopy (TEM) ranged between 3.0 and 4.8 nm. UV-vis spectroscopy of the samples showed bandgap energies ranging from 2.52-3.08 eV. The surface areas, pore volumes, and pore sizes of the investigated modified and unmodified clays determined by the Brunauer, Teller, Emmett/Barrett Joyner Halenda (BET/BJH) model ranged from 12.06-64.51 m2/g, 0.029-0.068 cm3/g, and 0.642-2.802 nm, respectively. To enhance the mixing of oil and clay, the adsorbents were grafted with silane and confirmed by Fourier transform infrared (FTIR) spectroscopy through CH peaks at ~1450 and ~2860 cm-1. The modified clay materials exhibited favorable properties for use as photocatalysts.

Effective stabilization of per- and polyfluoroalkyl substances (PFAS) precursors in wastewater treatment sludge by surfactant-modified clay

The application of biosolids or treated sewage sludge containing per- and polyfluoroalkyl substances (PFAS) in agricultural lands and the disposal of sludge in landfills pose high risks to humans and the environment. Although PFAS precursors have not been regulated yet, their potential transformation to highly regulated perfluoroalkyl acids (PFAAs) may enable them to serve as a long-term source and make remediation of PFAAs a continuing task. Therefore, treating precursors in sewage sludge is even more, certainly not less, critical than treating or removing PFAAs. In this study, a green surfactant-modified clay sorbent was evaluated for its efficacy in stabilizing two representative PFAA precursors in sludge, e.g., N-ethyl perfluorooctane sulfonamido acetic acid (N-EtFOSAA) and 6:2 fluorotelomer sulfonic acid (6:2 FTSA), in comparison with unmodified clay and powdered activated carbon (PAC). Results showed N-EtFOSAA and 6:2 FTSA exhibited distinct adsorption behaviors in the sludge without sorbents due to their different physicochemical properties, such as hydrophobicity and functional groups. Among the three sorbents, the modified clay reduced the water leachability of N-EtFOSAA and 6:2 FTSA by 91.5% and 95.4%, respectively, compared to controls without amendments at the end of the experiment (47 days). Within the same duration, PAC decreased the water leachability of N-EtFOSAA and 6:2 FTSA by 60.6% and 37.3%, respectively. At the same time, the unmodified clay demonstrated a poor stabilization effect and even promoted the leaching of precursors. These findings suggested that the modified clay had the potential for stabilization of precursors, while negatively charged and/or hydrophilic sorbents, such as the unmodified clay, should be avoided in the stabilization process. These results could provide valuable information for developing effective amendments for stabilizing PFAS in sludge or biosolids. Future research should evaluate the long-term effect of the stabilization approach using actual sludge from wastewater treatment facilities.

Efficient removal of cationic dye from wastewater using novel low-cost adsorbent, cellulose-clay composite: Insights from isotherm, kinetic, thermodynamic, and molecular dynamics simulation studies

This study was aimed to evaluate the potential of a natural clay modified with cellulose acetate polymer (CA) as a sustainable and cost-effective material for removing cationic dyes, particularly crystal violet (CV), from aqueous solutions. The cellulose acetate-clay composite (CA-Clay) was created by mixing CA with natural clay and characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscope (SEM) and X-ray fluorescence (XRF) techniques. Batch adsorption studies were conducted to investigate the impact of contact time (10–360 min), initial concentration (50–500 mg/L), temperature (293–318 °K), and pH (2–12) on the removal of CV from aqueous solutions using both CA-Clay and raw clay. Molecular Dynamic simulations (MDS) were employed to explore the adsorptive properties of the surfaces of illite and kaolinite clay fractions and the adsorption behavior of CV on both modified and unmodified clay fractions with (CA). The results showed that the maximum equilibrium adsorption capacity for the CA-Clay and raw-Clay was 67.35 mg/g and 47.62 mg/g, respectively. The kinetic behavior and the isotherms were satisfactorily fitted with the pseudo second-order and Langmuir models, respectively. The thermodynamic parameters showed that the adsorption of CV onto CA-Clay and raw clay was a spontaneous process, and the Gibbs energy increased with increasing temperature. Molecular Dynamic simulations revealed that the higher negative value of the calculated interaction energy in the presence of the (CV-CA-Illite-Water) system was attributed to electrostatic interactions and hydrogen bonds formed between CV molecules and both the illite surface and CA oxygen atoms. Overall, this study suggests that CA-Clay is a promising adsorbent for the removal of cationic dyes from wastewater and provides insights into the adsorption mechanisms and thermodynamic parameters of CV adsorption onto CA-Clay and raw clay.

Study of Clayey Soils Stabilized with Ladle Furnace Slag as Alternative Binder for Use in Road Works

Steelmaking industry generates a large volume of by-products that not always can be reintroduced into production processes, such as the steelmaking process itself or the production of cement. This is the case of ladle furnace slag (LFS), whose potential use is limited and usually ends up in landfill. This work investigates the feasibility of using LFS as binder for clayey soils stabilization in substitution of lime. The main parameters evaluated are plasticity index, California Bearing Ratio (CBR) and Unconfined Compressive Strength (UCS). The results show that the strength behavior of the mixtures is remarkable, obtaining increases in the CBR index between 8-14 times above unmodified clays. The mechanical performance base on UCS results show improvements of 85 % relative to natural soils three days after mixing. Moreover, if the curing time is up to 90 days, the UCS doubles or triples its value. Depending on the chemical composition of the soils, the performances of the mixtures are different, but in all cases the results are positive and encourage further research for the incorporation of ladle furnace slag as stabilizing agent.

Evaluation of Performance of Polyacrylamide-Modified Compacted Clay as a Gas Barrier: Water Retention and Gas Permeability and Diffusion Characteristics

In this paper, the performance of a gas barrier that consisted of polyacrylamide (PAM)-modified compacted clayey soil was experimentally explored. The moisture content and water loss characteristics of the tested soils were adopted as indicative indices of water retention capacity (WRC). The gas permeability (Kp) and gas diffusion coefficient (Dp) of the modified compacted clays were evaluated via gas permeability and gas diffusion tests. The test results showed that the moisture content of the modified compacted clay samples subjected to drying tests increased with increasing polyacrylamide content. Kp and Dp decreased with increasing PAM content. Compared with 0.2% PAM content, the Kp of the sample with 1.0% PAM was reduced by ten times, and the Dp was reduced to ~35%. Compared to the unmodified clay, the liquid limit of the PAM-modified clay increased by 45~55%. Comparison of the liquid limit tests between this study and previous studies revealed that the liquid limit ratio of the zwitterionic polyacrylamide (ZP)-modified soil was much higher than the other material-modified soils. The results of this study are useful to facilitate the application of modified compacted clays as gas barrier materials at industrial contaminated sites.

Aqueous Adsorptive Removal of Bisphenol A Using Tripartite Magnetic Montmorillonite Composites

The adsorption of bisphenol A into untreated montmorillonite clay, doped titanium composite and cationic polymer modified tripartite magnetic montmorillonite composite was investigated under different conditions. The magnetic property of the modified adsorbent was ascertained by action of external magnetic field on the materials when dispersed in aqueous media. The XRD results for the unmodified and modified adsorbents showed that interlayer spacing of the clay material increases due to intercalation of the precursor molecules. The textural properties of the adsorbents from BET analysis showed that pore size and specific surface area of the tripartite magnetic composite was calculated to be 288.08 m2/g while that of the unmodified clay was 90.39 m2/g. The TGA results showed the tripartite magnetic composite was more stable with the lowest percentage mass loss compared to the unmodified montmorillonite. The tripartite magnetic composite showed higher adsorption capacity. Adsorption was best described by the Freundlich isotherm model, which confirmed that the adsorption process was multilayer coverage unto the uneven surface of the adsorbents. Kinetic treatment of the adsorption data confirmed the the process followed a pseudo-second-order kinetic model and predominantly chemisorption process. The standard Gibb’s free energy computed for the adsorbents showed that the adsorption processes were favourably spontaneous with highly negative energy values of −336.70, −533.76 and −1438.38 KJ/mol, respectively, for the unmodified montmorillonite, doped titanium composite and the tripartite magnetic composite. It was observed that the addition of cationic aromatic moiety to the clay material increased pollutant-adsorbent interactions and improved adsorption capacity for micro-pollutants in a simulated industrial effluent.

Thermophysical properties and grain size effects in Luffa Cylindrica-modified clay composites for thermal insulation

The study explored the thermal insulation potential of composite material made from clay and Luffa cylindrica. Clay/ Luff cylindrica composite (denoted as Clay/L-C) was developed from natural resources. In the research, Luffa cylindrica particles of different grain sizes and different proportions were mixed with clay, and thermal evaluations were done with respect to thermal conductivity, thermal diffusivity, specific heat capacity, mass depletion with temperature, and microstructure. Two different mixture ratios, namely 4:1and 3:2 corresponding to 20 wt % and 40 wt % Luffa cylindrica particle, respectively, were used for Clay/ Luffa cylindrica combination. While Luffa cylindrica particle sizes varied from 600µm to 300µm and 150µm, the effects of Luffa cylindrica content and particle size on thermal properties were then examined. These novel composite materials developed in this study demonstrate motivating potential for enhanced thermal insulation when compared to unmodified clay. Improved thermal insulation performance indicated by thermal properties was observed for all the modified samples. This is on the account of reduced thermal conductivity of the modified samples. The best sample possessed thermal conductivity, thermal resistivity, thermal diffusivity, specific heat capacity, and porosity values of 0.216 W/mK, 462.90°C.cm/W, 0.123 mm/s2 1.493 MJ/m3K, and 89.3%, respectively. Results show that Luffa cylindrica fiber can be applied as an additive for effective thermal insulation. Development in this area of study is very necessary especially as the raw materials are readily available and cost-effective.

Non-catalytic and Catalytic Pyrolysis of Low Density Polyethylene LDPE Plastic Waste Into Fuel Ranged Hydrocarbons Using Nigerian Local Clay Composites

Plastic utilisation and plastic waste accumulation is rising in recent times mostly in developing countries. The utilization of modified and unmodified Nigerian bentonite clay as catalyst for preparation of fuel-ranged hydrocarbons from low-density polyethylene (LDPE) sachet wastes by pyrolysis was investigated. Pyrolysis of LDPE was done using locally fabricated semi-batch reactor condenser column. The products were characterized using Fourier transform infra-red spectroscopy (FTIR) and gas chromatograph with a flame ionisation detector (GC-FID). Physicochemical properties of the products were determined using standard analytical methods. The products from non-catalysed contained mostly saturated hydrocarbons compared to that of the catalytic process which contained more branched-chain hydrocarbons and mono-substituted aromatics. Physicochemical properties of the product from non-catalytic process showed resemblance to those of kerosene and diesel fuel while the properties of products from catalytic pyrolysis closely approximates those of commercial gasoline. This implies that the catalytic process gave products that were more suitable as fuels for auto engine which require higher octane number based on their naphthenic and aromatic content.

Magnetic Functionalization of Poly( N ‐isopropylacrylamide) Hydrogels for Sensor Applications

To develop a hydrogel sensor system using the Hall effect to detect the degree of swelling, gels containing high concentrations of magnetic particles are necessary to induce a strong magnetic field. For this purpose, hydrogels based on poly(N-isopropylacrylamide) cross-linked with Laponite XLS are modified with various magnetic nanoparticles. The focus of this work is to introduce high particle densities with a homogeneous distribution into the gel. Particles are coated with 3-(trimethoxysilyl)propyl methacrylate to bind them into the network structure. The swelling behavior and temperature response of gels containing pure and modified particles are compared to the unmodified clay gel. Ferrogels are further synthesized in a magnetic field to permanently align magnetic nanoparticles in the network. This results in permanently embedded rod-like structures spanning the entire length of the gel. The influence of this anisotropic distribution on the mechanical properties of the hydrogel is investigated through compression measurements.

Synthesis, characterization and application of organoclays for adsorptive desulfurization of fuel oil.

The present study encompasses the application of cost effective, organo-modified bentonite material for efficient desulfurization of model oil and real fuel. For the adsorptive desulfurization of oil, dibenzothiophene (DBT) was used as model compound. Various experimental parameters (time, temperature, adsorbent-amount and DBT concentration) were thoroughly investigated. The synthesized material was characterized via X-ray diffraction (XRD), X-ray Fluorescence (XRF), Scanning electron microscopy (SEM), Energy dispersive x-ray (EDX), Thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FT-IR). The modification exhibits the increase in interlayer spacing of clay as confirmed from XRD and modified material shows interesting morphology as compared to unmodified bentonite. The results showed that > 90% of DBT removal was achieved under optimized conditions for B-BTC, B-BTB and B-DSS and > 80% for B-BEHA, for model fuel oil which are greater than unmodified clay (< 45%). Additionally, the findings from desulfurization of real fuel oil declare that 96.76% and 95.83% removal efficiency was achieved for kerosene and diesel oil respectively, at optimized conditions and fuel properties follow ASTM specifications. The obtained findings well fitted with thermodynamic, isothermal (Langmuir) with adsorption capacity (70.8 (B-BTC), 66 (B-BTB), 61.2 (B-DSS) and 55.2 (B-BEHA) in mg/g) and pseudo-second-order kinetics. In thermodynamic studies, negative sign (Delta G^circ ) specifies the spontaneity whereas, left(Delta H^circ right) endothermic and positive sign (Delta S^circ ) show randomness after DBT adsorption onto organoclay.

Adsorption of Copper (II) from Aqueous Solutions with Alginate/Clay Hybrid Materials.

Massive amounts of industrial and agricultural water around the world are polluted by various types of contaminants that harm the environment and affect human health. Alginic acid is a very versatile green polymer used for heavy metal adsorption due to its availability, biocompatibility, low cost, and non-toxic characteristics. The aim of this paper was to prepare new low-cost hybrid composite beads using sodium alginate with treated montmorillonite and kaolin for the adsorption of copper (Cu) cations. Modified and unmodified clays were investigated by studying their morphology and elemental composition, functional groups, and mean particle size and particle size distribution. The characterization of alginate/clay hybrid composite beads was carried out by evaluating surface morphology (by scanning electron microscopy, SEM), crystallinity (by X-ray diffraction, XRD), and point of zero charge (pHpzc)(Zeta Potential Analyzer). Batch adsorption experiments of alginate/clay hybrid composite beads investigated the effect of metal concentration in the range of 1–4 mg L−1 on Cu(II) removal, adsorption kinetic for maximum 240 min, and Langmuir and Freundlich adsorption isotherms by using atomic absorption spectrometry. The pseudo-second-order kinetic model best fitted the adsorption for alginate/montmorillonite beads (R2 = 0.994), while the diffusion process was predominant for montmorillonite/kaolin beads (R2 = 0.985). The alginate/clay hybrid materials best fitted the Langmuir isotherm model.

3D Printing of Alginate-Natural Clay Hydrogel-Based Nanocomposites.

Biocompatibility, biodegradability, shear tinning behavior, quick gelation and an easy crosslinking process makes alginate one of the most studied polysaccharides in the field of regenerative medicine. The main purpose of this study was to obtain tissue-like materials suitable for use in bone regeneration. In this respect, alginate and several types of clay were investigated as components of 3D-printing, nanocomposite inks. Using the extrusion-based nozzle, the nanocomposites inks were printed to obtain 3D multilayered scaffolds. To observe the behavior induced by each type of clay on alginate-based inks, rheology studies were performed on composite inks. The structure of the nanocomposites samples was examined using Fourier Transform Infrared Spectrometry and X-ray Diffraction (XRD), while the morphology of the 3D-printed scaffolds was evaluated using Electron Microscopy (SEM, TEM) and Micro-Computed Tomography (Micro-CT). The swelling and dissolvability of each composite scaffold in phosfate buffer solution were followed as function of time. Biological studies indicated that the cells grew in the presence of the alginate sample containing unmodified clay, and were able to proliferate and generate calcium deposits in MG-63 cells in the absence of specific signaling molecules. This study provides novel information on potential manufacturing methods for obtaining nanocomposite hydrogels suitable for 3D printing processes, as well as valuable information on the clay type selection for enabling accurate 3D-printed constructs. Moreover, this study constitutes the first comprehensive report related to the screening of several natural clays for the additive manufacturing of 3D constructs designed for bone reconstruction therapy.