Bentonite Composites Research Articles

Impacts of Impurity Removal Chemical Pretreatment Procedures on the Composition and Adsorption Properties of Bentonites

This work is based on a detailed study of samples from three industrial bentonite deposits in Russia (10th Khutor, Zyryanskoe) and Kazakhstan (Taganskoe). The samples of the listed bentonites were undergoing stage-by-stage purification from carbonates, organic matter, and non-clay iron-bearing phase procedures. The conducted research revealed changes in the composition of bentonites already at the first stage of purification, which, however, were not noted for all bentonites, as well as a change in the forms of Fe in smectite structure. The latter is probably associated with changes in cis- and trans-vacant positions. Sorption characteristics with respect to 137Cs are determined using the localization and charges in the smectite layer and the slight changes during purification, along with the specific surface area indicators.

Heteroatom doped biochar-aluminosilicate composite as a green alternative for the removal of hazardous dyes: Functional characterization and modeling studies

In this work, a novel nitrogen-doped biochar bentonite composite was synthesized by a single-pot co-pyrolysis method. Batch studies were conducted to evaluate the performance of the developed composite in eliminating synthetic dyes from the aqueous matrix. Energy dispersive X-ray spectroscopy analysis and field emission scanning electron microscopy imaging confirmed the N doping and bentonite impregnation into biochar. X-ray photoelectron spectroscopy analysis revealed that the N atoms were doped interstitially into the carbon matrix of biochar in the form of pyridinic and pyrrolic nitrogen. Simultaneous heteroatom doping and bentonite impregnation reduced the specific surface area to 41.721 m2 g−1 but improved the adsorption capacity of biochar for dye adsorption. Further experimental studies depicted that simultaneous bentonite impregnation and N doping into the biochar matrix is beneficial for direct blue-6 (DB-6) and methylene blue (MB) removal and maximum adsorption capacities of 53.17 mg. g−1 and 41.33 mg. g−1 were obtained for MB and DB-6, respectively, at varying conditions. Adsorption energetics of the dyes with the developed composite portrayed the spontaneity of the process through negative ΔG values. The Langmuir and Freundlich isotherm models fitted the best for MB and DB-6 adsorption. The monolayer adsorption capacity and favourability factor for MB and DB-6 adsorption were calculated to be 54.15 mg. g−1 and 0.217, respectively from the best-fitted isotherms. Based on density functional theory calculations and spectroscopic studies, major interactions governing the adsorption were predicted to be charge-based interactions, π-π interactions, H-bonding, and Lewis acid-base interactions.

Research on color treatment of industrial textile wastewater using synthesized inorganic bentonite composite as an adsorbent

Vietnamese bentonite with poor quality had been purified before being modified with iron salts to create inorganic bentonite composite (Ben-C). This process increased the specific surface area to 221.83 m2g−1. The test showed that the reactive dye was rapidly adsorbed in about 1 h by the Ben-C and the adsorption efficiency reached its maximum value at a Ben-C content of 3 g/L. Ben-C had been used as an adsorbent for 6 types of textile industrial wastewater. Companies used different kinds of dyes and additives, so the color adsorption time of each wastewater was also different, ranging from 0.25 to 2 h. Adsorption efficiency tended to increase with adsorbent content, but the increased level depended on the type of wastewater. Wastewater color treatment was more effective when the adsorption process was carried out at a low temperature, 20–25 °C. The FTIR spectrum of wastewater also evaluated the effectiveness of wastewater color removal.

Analysis of natural organic matter chemistry in bentonite clay under compaction using different dry densities and duration

The Nuclear Waste Management Organization of Canada has adopted an adaptive phased management plan for the long-term storage of used nuclear fuel in a Deep Geological Repository (DGR). The DGR barrier system employs copper-coated used fuel containers (UFCs) surrounded by buffer material which is composed of highly compacted bentonite clay. The natural organic matter (NOM) composition of the compacted bentonite is of practical importance for the safety assessment as it regulates the biogeochemical processes at the interface between the UFCs and the buffer layer. However, insufficient investigations on NOM constituents limits the understanding of biogeochemical dynamics in bentonites compacted under different dry densities. This study analyzed the carbon content and NOM composition using targeted compound analysis and solid-state 13C nuclear magnetic resonance (NMR) spectroscopy with bentonites compacted at 1.1, 1.4 or 1.6 g/cm3 dry density for 1, 3, 6, 12 or 18 months. Organic carbon contents were similar across bentonites with different compaction densities at various durations as compared to the reference clay (powdered bentonite sample before compaction). The overall NOM composition measured by solid-state 13C NMR suggested a predominance of alkyl and aromatic carbon in bentonite samples. No marked variations were observed for the NOM components (i.e., alkyl, O-alkyl and aromatic carbon) between the compacted bentonites and the reference clay. Targeted compound analysis revealed that the extractable lipid concentrations in the compacted clays did not significantly vary from the reference bentonite with only some compounds exhibiting nano-gram level differences. Bentonites with relatively lower dry densities (1.1 and 1.4 g/cm3) demonstrated slightly higher extractable compound concentrations, but these differences were not statistically significant. In contrast, the compound concentrations of bentonites compacted to 1.6 g/cm3 were similar or slightly lower compared with the reference bentonite, likely associated with limited microbial growth under high dry compaction density. Taken together, these results suggested that NOM composition and quantity did not significantly alter in bentonites under various pressures nor with longer experimental durations. These findings highlight that compacted bentonite exhibited geochemical stability under the simulated repository environments, which provides critical insight for design and performance of engineered barrier system in a DGR concept.

Enhanced dielectric properties of zinc doped bentonite composites: an effect of cobalt doping concentrations and tight binding calculation

In this study we have successfully synthesized undoped and Zn and Co incorporated bentonite samples. The amount of Zn was kept constant while as Co amount was varied. All the synthesized samples were characterized using x-ray diffraction analysis which confirms the predominant presence of montmorillonite in all the samples thus confirming successful formation of bentonite. Similarly, EDX analysis confirms successful incorporation of Zn and Co in Ben sample. The analysis of the dielectric properties of the produced samples was successfully carried out, and the frequency dependence of the dielectric constant and dielectric loss was explored. According to the results, all the samples exhibit considerable dielectric dispersion at lower frequencies, whereas steady dielectric constant and modest dielectric loss are shown at higher frequencies. The effect of Zn, Co incorporation and temperature dependence of dielectric behaviour of all the samples was also analysed and it was observed that at low temperatures undoped Ben samples showed high dielectric constant while as at higher temperatures the incorporation of Zn and Co enhances the dielectric constant of as prepared sample. Similarly, the variation of conductivity of as prepared samples with frequency and temperature was analysed and it was observed that all the samples show similar conduction behaviour and follows correlated barrier hopping type of conduction. The real and imaginary part of electric modulus as a function of frequency was also analysed. Further, theoretical analysis showed considerable change in HUMO and LUMO which is considered as a main reason responsible for change in dielectric characteristics of Ben and Zn/Co incorporated samples. From this study it was observed that the incorporation of metal ions into the layered bentonite improved the dielectric properties at high temperature thus this study provides a new insight into the development of new dielectric materials which could be used under high temperature operation conditions.

Experimental and modelling study of the interaction of bentonite with alkaline water

Compacted bentonite is planned to be used as buffer and backfill materials for the containment of radioactive waste in underground repositories. The performance of these barriers depends on the swelling capacity of bentonite upon hydration. Prolonged interaction between bentonite and alkaline fluids from neighbouring concrete structures can impair the swelling capacity due to profound changes in the chemical composition of bentonite. The coupled hydro-chemo-mechanical behaviour of bentonite under such conditions is at present not well understood. This paper presents for the first time a combined experimental and modelling study that addresses this coupled behaviour with the aim of understanding the key mechanisms leading to swelling pressure loss. Two experiments are presented in which compacted Wyoming bentonite was saturated with either clay or cementitious water, leading to different initial swelling capacities. The samples were subsequently subject to a flow of a KOH-rich cementitious water leading to a slow but sustained decrease in swelling pressure in both tests. The main novelty is the application of a recently developed hydro-chemo-mechanical model for bentonite for interpretation of the experiments. The model accounts for the impact of montmorillonite dissolution, cation exchange reactions, and changes in salinity on the swelling capacity of bentonite. The model results show a relatively good agreement with experimental measurements and suggest that the decrease in swelling capacity of bentonite is driven primarily by an increase in potassium fraction in the interlayer water and by montmorillonite dissolution.

Pressure-dependent cationic associations of ionic liquids with bentonite nanoclay

Pressure-dependent IR spectroscopy is used to investigate the possibility of stabilizing ionic liquid (IL)–hydrophilic bentonite (Bent) composites with the application of high pressures. Ambient-pressure experiments suggest IL hydrophilicity/hydrophobicity impacts cation and anion interactions with Bent. For example, both the cation and anion of hydrophilic 1-butyl-3-methylimidazolium dicyanamide ([BMIM][DCA]) experience composition-dependent vibrational mode wavenumber shifts. However, anion–Bent interactions are suppressed at ambient pressure when the nanoclay is paired with hydrophobic 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([BMIM][NTf2]). Compression to high pressures triggers significant blue shifts for ring-bound C–H stretching bands. The rates of these changes upon pressurization indicate the two ILs experience different interaction motifs with the Bent surface. Large wavenumber shifts for C4–H and C5–H stretching modes of [BMIM][NTf2] imply preferential coordination to Bent surface sites through these groups. This presumably leaves the C2–H group available for hydrogen bonding with the NTf2 anion. The situation is different for [BMIM][DCA], where all three C–H groups on the imidazolium ring appear to interact with Bent surface sites. Depressurization reveals further differences between the two systems. Spectroscopic features are reversible for [BMIM][NTf2], whereas the C–H stretching mode blue shifts for [BMIM][DCA] are either irreversible or the relaxation is kinetically hindered upon return to ambient pressure. Taken together, the spectroscopic data strongly suggests that IL–Bent interactions are pressure sensitive, and IL assemblages along the interface may be manipulated through the application of high pressure.

Structured LDH/Bentonite Composites for Chromium Removal and Recovery from Aqueous Solutions.

This study focuses on chromium removal through adsorption and ion exchange using structured calcined layered double hydroxide (LDH) (MgAl)-bentonite composites. Firstly, the powders were structured into granulates to study the effect on Cr sorption kinetics to circumvent the limitations of working with powders in real-life applications. Secondly, the regeneration of the structured composites was optimized to enable multi-cycling operation, which is the key for their applicability beyond laboratory scale. Firstly, the LDH/bentonite ratio was optimized to obtain the best performance for the removal of Cr3+ and Cr6+ species. In powder form, the calcined adsorbent containing 80 wt% LDH and 20 wt% bentonite performed best with an adsorption capacity of 48 and 40 mg/g for Cr3+ and Cr6+, respectively. The desorption was optimized by studying the effect of the NaCl concentration and pH, with a 2 M NaCl solution without pH modification being optimal. The kinetic data of the adsorption and desorption steps were modelled, revealing a pseudo-second order model for both. This was also demonstrated using XRD and Raman measurements after the Cr3+ and Cr6+ adsorption tests, indicating successful uptake and revealing the adsorption mechanism. Finally, five consecutive adsorption-desorption cycles were performed, each showing nearly 100% adsorption and desorption.

Acoustic properties of composites materials based on bentonite and coconut or cactus (nopal) fibers

Materials made from natural fibers or waste have been studied to acquire a composite with good acoustical isolation properties, commercial materials used in this concern are polyurethane foam, fiberglass, Rockwool, and drywall. This work proposes using waste coconut and cactus ( Opuntia ficus-indica) fibers to synthesize bentonite composites and study their physicochemical and acoustic properties. Physicochemical properties of precursor and composites (75% wt. fiber) were determined by XRD, FTIR, N2 adsorption, optical, and SEM microscopies. The transmission, reflection, and absorption coefficients, 50 to 10,000 Hz, were obtained in an impedance tube and were compared with commercial materials. The composites were subjected to surface humidity and thermal (30, 50, and 70°C) tests to evaluate the stability of acoustic properties. The mechanical properties of the composites are improved with the addition of bentonite, hardness is increased by 6.7% and 0.9%, and the density is decreased by 73.6% and 45.5%, for coconut and nopal, respectively, porosity also changes. We corroborated the significant presence of montmorillonite in bentonite (XRD), while the nopal or coconut fibers are composed of hemicellulose, cellulose, and lignin (FTIR). Also, mucilage was identified in the nopal samples as adherent biopolymer that generates stability either thermally or in wetting conditions. Coconut fiber has a high absorption coefficient (similar to polyurethane), which is reduced with humidity. However, by adding bentonite, the reflection is more elevated, and transmission is lower than commercial materials. The bentonite and nopal (fiber and composite) presented stability in the acoustic coefficients as a function of humidity and temperature.

Effects of synthetic processes on the swelling capacity and modification mechanism of CMC-modified bentonite composites

Polymer-modified bentonite is widely utilized in wastewater treatments and barrier projects for contaminants due to its excellent performance. Despite numerous studies being conducted on the properties of different types of polymer-modified bentonite, the impact of synthetic processes has not been systematically explored. Hence, two common processes, the wet process and the semi-dry process, were investigated and compared. Sodium carboxymethyl cellulose (CMC)-modified bentonite was selected as an example here. Response surface methodology (RSM) was employed to develop relationship models of various factors versus the swell index. Specifically, the influence of modification temperature and stirring duration in the wet process, as well as pressure, moisture content, and ageing time in the semi-dry process were investigated. The feasibility and accuracy of the models were verified by the analysis of variance (ANOVA) and hypothesis testing. Results indicate that the semi-dry process leads to greater expansibility than the wet process. CMC dosage is a critical factor affecting performance. The following recommendations were made for the practical production: for the wet process, long-duration stirring at high temperature should be avoided at low CMC dosage, while the opposite is true at high CMC dosage (> 10%); for the semi-dry process, a longer ageing period should be selected at higher polymer contents, which can obviously improve the performance. Microscopic experiments were conducted to compare the differences in the modification mechanism of the two processes. Polymer/bentonite composites mainly form co-existing exfoliated and intercalated structures in wet and semi-dry processes, and the latter has a higher degree of exfoliation. The intensity of cationic bridging, hydrogen bonding, and group interaction between the polymer and bentonite is stronger when adopting the semi-dry process, resulting in better modification effects.

Adsorption of tetracycline using chitosan–alginate–bentonite composites

Nanocomposites composed of biopolymers and clay minerals have applications in several fields, particularly in environmental remediation. In this study, a series of new adsorbents for tetracycline was prepared by the microwave-assisted reaction of two biopolymers, chitosan (CS) and sodium alginate (SA), with sodium bentonite (Na-Bent), a clay mineral. The nanocomposites were prepared by first mixing CS with Na-Bent at 100, 200, and 300% of Na-Bent's cation-exchange capacity (CEC) at 50 °C for 30 min. Subsequently, the resulting mixture was reacted with SA at a 1:1 mass ratio under microwave-assisted heating. X-ray diffraction analyses indicated the formation of intercalated nanocomposites (with basal spacings of 1.96–2.26 nm) with increasing amount of CS, as quantified by CHN elemental analysis (the samples obtained using CS at 300% CEC of Na-Bent had higher carbon contents of 5.82% or 6.95 mmol/ g). Maintenance of the flake-like morphology of the clay was confirmed by scanning electron microscopy. The tetracycline-adsorption studies, viz., kinetics and equilibria at pH 5.5, using the bionanocomposites were conducted using 10–550 mg L−1 tetracycline solutions. Compared with that of Na-Bent (69% removal at 75 mg dosage), the nanocomposites exhibited a higher adsorptive capacity (>75%) for the antibiotic at 10 mg L−1, even when a lower dosage of the nanocomposites (25 mg) was used in comparison with that of Na-Bent. A better performance was obtained using the bionanocomposite prepared with CS at 100% CEC of Na-Bent, and the tetracycline removal reached 97.7% in 30 min. The addition of SA did not significantly change the adsorption capacity of the nanocomposites, and the tetracycline removal reached 81.8–82.7% at 45–90 min (adsorbent concentration: 10 mg L−1). Long- and short-range interaction characteristics and zeta potential measurements indicated that electrostatic interactions and ion-exchange processes drove the adsorption mechanism.

Wood ash as a stabilizer for pavement subgrade

Soil stabilization techniques have been widely accepted as a measure for enhancing the soil engineering properties. Use of conventional additives such as lime, cement, etc. has been found to have long-term environmental and economic limitations. In this study, wood ash has been experimented as a subgrade stabilizer for sodium bentonite clay, which is a weak pavement subgrade. Chemical composition and index properties of wood ash and bentonite were determined. Bentonite was replaced with 0%, 10%, 20%, 30%, and 40% of wood ash to determine the changes in the engineering properties. Experimental results showed that the maximum values of Optimum Moisture Content (OMC), Maximum Dry Density (MDD), and Unconfined Compressive (UCC) Strength, lie between 20% and 30% dosages of wood ash. Further experiments were conducted with 22%, 24%, 26% and 28% dosages of wood ash in bentonite, which showed optimum strength properties at 24% mix percentage. UCC strength at optimum wood ash dosage at 0 days and 7 days of curing were 122 kPa and 148 kPa respectively. CBR value for soaked specimen at optimum dosage was found as 7.3%. Substantial results prove that wood ash is a successful stabilizer for sodium bentonite as pavement subgrade. This also provides a sustainable solution for disposal of wood ash.

Mining Leachates Effect on the Hydraulic Performance of Geosynthetic Clay Liners under Different Temperatures

Geosynthetic clay liners (GCLs) are often used as anti-seepage systems in landfills and at the bottom of tailing ponds. The anti-seepage performance of GCL will change under different temperatures. In this study, bentonite was mixed with test solutions at different temperatures to measure the basic performance indexes of bentonite components and analyze the permeability. The composition and micro-structure of bentonite at different temperatures were analyzed by X-ray diffraction, X-ray fluorescence spectrum, and SEM, and the change rule of permeability property with the mine leachates at different temperatures was understood by combining the macro-measured parameters with the microscopic analysis results. The research results indicate that the fluid loss of two bentonites increased with the increasing temperature due to the inhibition of ion exchange between bentonite and mixture by the increased temperature. The swelling index of the bentonite increased at high temperatures. The micro-structure analysis showed the increase of the pore size attributed to high temperature, and the uneven distribution of the pore size resulted in the increase of the intrinsic permeability. The study would provide the reference for the application of GCL in mining.

Mesoporous silica nanocatalyst used in the preparation of the retention substance bentonite-sorbents sorption of isotherms research

In this study, the retention substance bentonite was used in the preparation of a mesoporous silica nanocatalyst. The analysis of sorbents from the sorption isotherm study and the results obtained were summarized. Also discussed are the chemical composition of bentonite from the Navbahor deposit, the types of sorbent isotherms obtained by the adsorption of various gases on sorbents, descriptions of sorbent isotherms in mesoporous sorbents, the phase composition of sorbent samples synthesized from textures, and the physic-chemical characteristics of the X-ray diffractometric catalyst, and the dependence of the characteristics of texturs of the characteristics of nanocomposite sorbents made from bentonite.

Preparation and Swelling Properties of Poly(3,4–Thylenedioxythiophene)/Poly(Acrylic Acid)/bentonite Composite Hydrogels

In this study, poly(acrylic acid) (PAA)/bentonite (BNT) composites were synthesized through chemical crosslinking by a chemical polymerization using ammonium persulfate as initiator and N,N’-methylenebisacrylamide as crosslinker. Poly(3,4-ethylenedioxythiophene) (PEDOT) was synthesized by oxidative polymerization and then PEDOT/PAA/BNT composites were prepared by mixing PEDOT at 5%, 10% and 20% by mass into PAA/BNT composite. These hydrogel composites were characterized by FTIR, XRD and SEM. It was observed that water absorbency increased with the increase of PEDOT ratio of hydrogel composites.

Combined Orobol-Bentonite Composite Formulation for Effective Topical Skin Targeted Therapy in Mouse Model.

Orobol is an isoflavone that has a potent skin protection effect. The objective of this study was to prepare a novel bentonite-based composite formulation of orobol to enhance topical skin delivery. The composition was optimized based on the orobol content in the composite and the in vitro release studies, followed by the in vitro and in vivo hairless mouse skin deposition studies. Physicochemical characterizations of the composite formulation were performed by powder X-ray refractometry (XRD) and scanning electron microscopy (SEM). The in vitro cytotoxicity and in vivo toxicity studies were conducted in human keratinocytes and in hairless mouse, respectively. The in vitro release of orobol from the bentonite composites was higher than that from the suspension, which was further increased with the addition of phosphatidylcholine. The composite formulation significantly enhanced the in vitro and in vivo skin deposition of orobol in hairless mouse skin compared to the orobol suspension. Moreover, the addition of phosphatidyl choline not only improved the dissolution and incomplete release of orobol from the bentonite composite but also enhanced the deposition of orobol in the skin. XRD histograms and SEM images confirmed that the enhanced dissolution of orobol from the composite was attributed to its amorphous state on bentonite. The in vitro and in vivo toxicity studies support the safety and biocompatibility of the orobol-loaded bentonite composite formulation. These findings suggest that the orobol-loaded bentonite composite formulation could be a potential topical skin delivery system for orobol.

Synthesis, characterization of Ag-WO3/bentonite nanocomposites and their application in photocatalytic degradation of humic acid in water.

In this study, Ag-WO3/bentonite nanocomposites were synthesized through a sol-gel process, a microwave irradiation technique, and a sol-immobilization process to examine their impact on the photocatalytic activity in the degradation of humic acids. The optical and structural properties of the synthesized materials were characterized using X-ray diffraction (XRD), Fourier-transform-infrared spectra (FTIR), field emission scanning electron microscope (FE-SEM) with energy dispersive X-ray (EDX), UV-Vis diffused reflectance spectra (UV-Vis DRS), Brunauer-Emmett-Teller (BET) method, and transmission electron microscope (TEM). The presence of Ag and WO3 peaks in the XRD and EDX spectra confirmed the synthesis of Ag-WO3 nanoparticles in the composite. The monoclinic structure of the produced WO3 samples are shown by powder X-ray diffraction patterns. The WO3-based nanocomposites' photocatalytic activity was improved by the composition of Ag and bentonite, which reduced the optical bandgap energy of WO3. The binary (Ag-WO3) nanocomposite showed improved photocatalytic activity towards the degradation of humic acid (HA) from 58% (pristine WO3) to 82% (Ag-WO3) when compared with the pristine WO3 sample under the visible light irradiation. Notably, the ternary (Ag-WO3/bent) nanocomposite demonstrated an outstanding photocatalytic efficiency of HA degradation (91.0%) under normal conditions (pH = 7.0 and 25°C). Humic acid degradation in Ag-WO3/bent was expressed by the pseudo-first-order kinetic. To summarize, integrating Ag, WO3, bentonite, and visible light radiation to activate HA efficiently can be offered as a successful and promising technique for wastewater treatment.

Bentonite Nanoclay Optoelectrochemical Property Improvement through Bimetallic Silver and Gold Nanoparticles

This study assesses the physical and electrochemical changes of bimetallic Ag-Au nanoparticle-functionalized bentonite nanoclay. Nanoclay was studied to deduce a better sensing material/film. A chemical co-reduction method was used to synthesize bimetallic Ag-Au c nanoparticles, which were used to prepare a Ag-Au/PGV bentonite composite. Bimetallic Ag-AuNPs and their nanoclay composite were optically characterized using the scanning electron microscope, ultraviolet visible spectroscopy, X-ray diffraction, and Fourier transform infrared, whilst cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to ascertain their electrochemical activity and properties. The results of surface morphological inspection showed an average size of 10 nm, in agreement with XRD. The bimetallic Ag-AuNPs UV/Vis characteristic wavelengths of 414 nm and 516 nm confirmed the presence of Ag and Au metals, respectively. XRD exhibited diffraction planes related to 2θ values of Ag and Au metals, whilst FTIR indicated mainly COO- functional groups from the citrate capping of bimetallic Ag-Au NPs. CV and DPV showed that bentonite nanoclay is largely insulated by silicates but exhibited a small electroactivity of Fe. The electroactivity of Ag-Au/PGV bentonite exhibited peak potentials due to Ag/Ag+ and Au/Au3+ redox couples at 0.19 V/−0.20 V and 1.37 V/0.42, respectively. The Ag-Au/PGV bentonite nanocomposite exhibited the highest surface concentration of 3.25 × 10−2 cm2, a diffusion coefficient of 2.36 × −11 cm2/s, and an electron transfer rate constant (Ks) of 1.99 × 10−4 cm2. The outcome of these results indicated that the Ag-Au/PGV bentonite nanocomposite was more electroactive than PGV. Therefore, this study accentuates Ag-Au/PGV bentonite nanocomposite as a novel and promising platform for electrochemical sensing with higher sensitivity and efficiency than other sensing materials.

Solidification/Stabilization of waste containing lead using flyash and bentonite

In this study, the Stabilization/Solidification was used to treat Pb as heavy metal waste using flyash and bentonite, as binder and mixing agent. Flyash and bentonite was mixed with the waste containing Pb and formed to cube called “mortar” with a size of 5x5x5 cm. The variations of flyash and bentonite were 100:0, 90:10, 80:20, 70:30, 60:40, 50:50, 40:60, 30:70, 20:80, 10:90, and 0:100. Then the mortars had a curing time process for 7 days, 14 days, and 28 days. After curing time process, the products tested using a compressive strength test and TCLP test. Result of compressive strength test indicated that the optimum compressive strength value occurred in 100% fly ash composition with 28 days curing time. The estimation of compressive strength test was 3220 tons/m2. The result of the TCLP test showed the optimum TCLP test results occurred at 100% fly ash composition and the rate was 0,0338 mg/L Pb. The composition of fly ash and bentonite showed a significant effect on the compressive strength and TCLP test.

Investigation of the properties of alkaline binding materials with the addition of fine bentonite

Introduction. Searching for new methods of making less energy-intensive materials by reducing their cost, adding local raw materials and industrial waste to the mineral resource base, as well as developing efficient production technologies is a relevant problem of the construction industry. A clinker-free technology for the manufacture of hydraulic binders will partially replace resource-intensive Portland cement in construction and help to solve these problematic issues to a certain extent and boost the environmental safety at the global level. The proposed binders, based on principles of structurization in alkaline systems as a combination of sequential and parallel physical and chemical transformations due to the contact interaction between fine powders of aluminosilicate nature and cations of alkali metals, contribute to the formation of strong and durable composites.
 Materials and methods. The study of energy dispersive microanalysis of components of the binder system was performed using the QUANTA 3D scanning electron microscope; dynamic light scattering was employed to study the particle granulometry with the help of the HORIBA analyzer. The strength characteristics of the binder systems “aspiration dust – bentonite – Na2O∙SiO2” were determined according to GOST 30744-2001 using Testometric FS150AT testing machine.
 Results. Electron microscopic analysis showed that particles of aspiration dust larger than 200 microns and smaller than 100 microns have a similar oxide composition, with a predominance of oxides of calcium, silicon, aluminum and carbon. The chemical composition of bentonite confirms the aluminosilicate nature. An increase in the physical and mechanical properties of specimens of the systems “aspiration dust – bentonite – Na2O∙SiO2” has been identified; it is the addition of higher dispersion bentonite that contributes to the dense packing of grains due to the volume-wise redistribution of particles, which positively affects the pore structure and water resistance of the cement stone.
 Conclusions. The results of the study have proven the new prospects for the alkaline activation of complex powders made of cement industry waste and bentonite clay; the characteristics and dependencies, obtained by the authors, will allow using the proposed technology in construction.