Interlayer Space Of Bentonite Research Articles

Removal of heavy metals from water by macro-mesoporous calcium alginate–exfoliated clay composite sponges

The contamination of drinking water and freshwater by heavy metals has become a growing concern for human health and environment that calls for immediate remedial action. Adsorption process has been proved to be a promising technology for producing treated water that complies with drinking water standards. In this work, we describe a facile and low-cost approach to fabricate porous calcium alginate composite sponges containing exfoliated bentonite clay (denoted as CRAB) by saponin-assisted foaming and external gelation techniques for efficient removal of Cu2+ and Cr6+ ions from aqueous solution and real world water samples. The formation of exfoliated organoclay within the composite matrix was achieved by intercalation of saponin into the interlayer spacing of bentonite and subsequent penetration of alginate chains. Morphological and textural characterizations revealed that the resultant CRAB sponges mainly exhibited meso- and macropores in their interior. The formation of calcium alginate-organoclay exfoliated composites was also verified by the XRD results. The performance of CRAB sponges in removing Cu2+ and Cr6+ ions from aqueous solution was evaluated under different environmental conditions including temperature, pH, ionic strength, and background electrolyte. The results demonstrated that the uptake capacity of Cu(II) and Cr(VI) increased with increasing temperature, suggesting the endothermic nature of the adsorption process. The Freundlich isotherm model was found to better interpret the equilibrium adsorption behaviors of Cu2+ and Cr6+ ions onto the investigated sorbents than the Langmuir model. The sorption kinetics for these metal ions followed a pseudo-first-order model. Reusability tests for CRAB sponge demonstrated that the sorption capacity of the sorbent is well maintained over three successive adsorption–desorption cycles. Together, these results indicate the great potential of low-cost and sustainable CRAB sponges for remediation of water polluted with copper and hexavalent chromium ions.

Development of Cationic Cellulose-Modified Bentonite-Alginate Nanocomposite Gels for Sustained Release of Alachlor.

The nanocomposite gel prepared from nanoclay and natural polysaccharides showed a good sustained-release property. Herein, a cationic cellulose-modified bentonite–alginate nanocomposite gel was prepared and used to enhance the sustained release of alachlor. The underlying effect and mechanism of the structure of modified bentonite–alginate nanocomposite gels on the release behavior of alachlor were explored by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric (TG) analysis. The results showed that the release of alachlor from the nanocomposite gels was dominated by Fickian diffusion and closely related to the adsorption capacity and permeability of the matrix. The cationic cellulose intercalated into the interlayer space of bentonite through an ion exchange reaction, which significantly enhanced the hydrophobicity of bentonite and its interaction with alachlor. The stacking aggregation of bentonite nanoplatelets and permeability of the gel network were decreased through the electrostatic interaction between cationic cellulose and alginate molecular chains, thus remarkably enhancing the sustained-release property of the nanocomposite gel. The release kinetics revealed that the release rate of alachlor from the nanocomposite gel first decreased and then increased as the content of bentonite and modified bentonite gradually increased. Also, the best sustained-release property of the nanocomposite gel was obtained at bentonite and modified bentonite additions of about 10%, under which the release time of 50% alachlor (T50) from bentonite–alginate and modified bentonite–alginate nanocomposite gels was 4.4 and 5.6 times longer than the release time from pure alginate gels, respectively.

Removal of tetracycline from aqueous solutions by adsorption on raw Ca-bentonite. Effect of operating conditions and adsorption mechanism

• Bentonite had the highest capacity for adsorbing tetracycline (TC) than other clays. • Bentonite presented a maximum adsorption capacity towards TC of 283.5 mg/g. • Adsorption capacity of bentonite was comparable to those of carbon-based materials. • TC adsorbed on the external surface and in the interlayer space of bentonite. • Adsorption of TC was due to cation exchange and electrostatic attraction. This study aims to investigate the adsorption of tetracycline (TC) from water onto several clays with different structural characteristics such as bentonite, sepiolite, vermiculite, halloysite, phlogopite and kaolinite. Among these, raw bentonite (Bent) presented the highest adsorption capacity due to its swelling characteristic, interlayer cations nature, and TC molecular size. The Bent and Bent equilibrated with TC were characterized by SEM, XRD, FT-IR, TGA, N 2 physisorption and Zeta potential techniques. The importance of the pH, ionic strength and temperature upon Bent adsorption capacity towards TC was studied thoroughly, and the reversibility of TC adsorption onto Bent was also analyzed. The results showed that the TC adsorption occurred on the external surface and in the interlayer space of Bent, and both physical and chemical mechanisms governed the adsorption. The basal space (0 0 1) at pH = 7 increased from 1.50 to 1.62 nm, while raised from 1.50 to 1.89 nm at pH = 3. The TC maximum uptake was 283.5 mg/g at pH = 3, relating to cationic exchange between interlaminar cations of Bent and the cationic TC species (TCH 3 + ), and electrostatic attraction among the negative surface of Bent and TCH 3 + . At pH = 7, there are weak electrostatic attractions between the Bent cationic sites and the positively charged dimethylamino group of the zwitterionic TC species (TCH 2 ± ) and the formation of outer-sphere coordination complexes between the TC negative species (TCH - ) and the internal hydration sphere of the interlayer Ca 2+ cation. Additionally, the TC adsorption on Bent was partially reversible and endothermic.

Effect of Bentonite on the Structure and Performance of Sodium Alginate as Microsphere Carrier of Essential Oil

The effect of bentonite (BT) on the structure and performance of sodium alginate (SA) as microsphere carrier of essential oil is studied. The addition of BT can improve the performance of alginate gel microspheres through the study of the properties of single carrier SA and composite carrier SA/BT. The experimental results show that the viscosity of composite carrier SA/BT solution is higher than that of carrier SA solution, and the increasing rate of viscosity of composite solution with temperature is less than that of SA. The addition of BT can effectively inhibit the swelling of SA microspheres. The hydrogen bonding between SA and BT is shown in FTIR, and the interlayer spacing of BT crystal structure is not changed in XRD analysis. The mass loss rate of SA/BT microspheres is lower than that of SA in TGA analysis. The more dense structure of SA/BT microspheres than that of SA microspheres is confirmed by SEM. The release rate of cinnamon oil in SA/BT gel microspheres is significantly lower than that in SA gel microspheres under different temperature conditions. The addition of BT could better control the volatilization of essential oil encapsulated in SA gel microspheres.

Specific molecular design of polycarboxylate polymers exhibiting optimal compatibility with clay contaminants in concrete

It is widely recognized that the dispersing ability of polycarboxylate superplasticizers (PCEs) could be hindered due to the presence of clay contaminants in concrete. In this study, a series of allyl ether-based polycarboxylate superplasticizers possessing short polyethylene glycol side chains was successfully synthesized and probed for their clay tolerance. The resulting PCE polymers were characterized via Size Exclusion Chromatography (SEC) to obtain their molecular properties. Thereafter, their dispersing ability was probed in the absence and presence of sodium bentonite. Allyl ether-based polycarboxylate (APEG) polymers possessing short side chains were found to exhibit enhanced clay resistance as compared to that of conventional MPEG PCEs holding long pendant chains. The mode of interaction between APEG PCEs and bentonite was investigated via sorption and XRD measurements. The data revealed that APEG PCEs possessing a lower side chain density intercalate less into the interlayer space of bentonite than those exhibiting higher side chain density.

Humic acid-modified bentonite composite material enhances urea-nitrogen use efficiency

Bentonite was modified by introducing humic acid (HA) into interlayer space of bentonite. The structural and physicochemical properties of modified bentonite were determined by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), X-ray powder diffraction (XRD) and thermogravimetric analysis (TGA). The results showed that HA could enter the bentonite interlayer and increase the interlayer distance. Moreover, we were also investigated the high adsorption capacity and thermodynamics of modified bentonite to NH4+ cations in solutions. Under the same conditions, the NH4+ adsorption efficiency of modified bentonite (96.4%) was 69.2% higher compared with the natural bentonite (57.0%). The pseudo-second order kinetic model well fit the adsorption kinetics of NH4+ on modified bentonite, indicating that the adsorption type was chemical adsorption or chemisorptions. The isotherms fit well with Langmuir model, and the separation factor revealed that NH4+ on modified bentonite belonged to favorable adsorption. Compared with the natural bentonite, the modified bentonite exhibited a much lower leaching loss of NH4+-N and NO3−-N in soil. Meanwhile, the loss of nitrogen caused by NH3 volatilization and N2O emission from soil could also be significantly attenuated by the combined application of modified bentonite and urea. The slower nitrogen release in the treatment combining modified bentonite and urea resulted in a greater yield and nitrogen uptake of wheat. Collectively, the modified bentonite could be used as nitrogen fertilizer synergist to enhance the nitrogen use efficiency.

Hexadecylpyridinium (HDPy) modified bentonite for efficient and selective removal of 99Tc from wastewater

99Tc is one of the critical fission products in the treatment of wastewater and the nuclear waste repository due to its long half-life (t1/2 = 2.13 × 105 y), high fission yield (~6%), and high mobility in the environment. The development of highly-efficient, low-cost and easily available materials that can rapidly and selectively remove 99Tc is of great significance, but remains a challenge. In this work, bentonite-based materials (HDPy-bent) were obtained through modifying bentonite with hexadecylpyridinium (HDPy) and applied for the remove of TcO4− as well as its surrogate ReO4−. The structure of HDPy-bent (e.g., the values of d001) was evaluated and the maximum loading amount of HDPy on bentonite was found to be 200% CEC. The loaded HDPy+ might replace exchangeable cations in the inter-layer space of bentonite. Batch experiment results show that HDPy-bent could quantitatively remove TcO4− from aqueous solution within 3 min. The distribution coefficient (Kd) of TcO4− in this material is up to 2.1 × 105 mL/g, which is significantly higher than most of the previously tested inorganic adsorbent materials. More importantly, HDPy-bent can selectively remove TcO4− in the presence of large excess (80,000 times) of competitive anions (NO3–, SO42−, CO32−, PO43− and Cl−). This work demonstrates that the HDPy-bentonite is a low cost, and effective adsorbent for removing 99Tc from contaminated water.

Development of Mn or Fe sulfides in the interlayer space of raw and Al-pillared bentonite

Preparation of metal sulfide nanoclusters (Mn or Fe) confined in the interlayer space of a bentonite either with or without previous Al2O3-pillaring was investigated by H2S-sulfidization of Mn²⁺- or Fe²⁺-exchanged Al2O3-pillared bentonite as potential strategy to control growth and mean final size of interlayered, MnS or FeS-like polynuclear nanoclusters. The materials were characterized by elemental analysis, cation exchange capacity, low-angle powder X-ray Diffraction, N2 adsorption isotherms, simultaneous thermal analysis (DTA/TGA), diffuse reflectance UV-vis spectroscopy and high-resolution X-ray photoelectron spectroscopy. Interlayered metal sulfides were successfully obtained in pretty short time of reaction (only ~12 h). Optimal set of preparation conditions was established promoting stabilization of the interlayered metal sulfides, whereas preserving typical layered stacking of the starting clay: (i) ratio H2S/M²⁺(incorporated) = 50 mol/mol (M = Mn²⁺ or Fe²⁺); (ii) temperature of sulfidization = 100 °C; (iii) 200 °C for final thermal treatment, irrespective the type of atmosphere used (inert-N2 or oxidizing-air) and (iv) acid-base neutralization prior to thermal treatment did not enhance thermal stability. The most efficient Al-pillaring was achieved with 20 meq Al³⁺/g clay in terms of both higher XRD 001 basal reflection and narrower distribution of alumina-pillars. HR-XPS and DR-UV-vis analyses of the best materials with every transition metal evidenced formation of polysulfide groups and blue-shift of the absorption signal as a consequence of the modification performed on the layered aluminosilicate. Development of Mn or Fe sulfides in the interlayer space of.... Available from: https://www.researchgate.net/publication/323399710_Development_of_Mn_or_Fe_sulfides_in_the_interlayer_space_of_raw_and_Al-pillared_bentonite [accessed Apr 18 2018].

Organic modification of bentonite and its effect on rheological properties of paper coating

ObjectiveThe effect of organic modified bentonite on rheological behavior of paper coating was studied to extend the use of bentonite in the paper industry. BackgroundIn the coating process, the paper coating was performed in various shear forces. Therefore, the rheological properties of the coating had profound effects on the quality of coated paper. In order to achieve the good rheology, paper coating required the addition of thickener or rheology modifiers. Organic bentonite was a kind of thixotropic ge1, which was extensively used in a number of applications as rheology modifier to modify the rheology and control the stability of systems. MethodNa+-bentonite was modified with diallyl dimethylammonium chloride and dodecyl trimethylammonium chloride, respectively. The organic bentonite was characterized by XRD and TGA and the rheological properties of paper coating containing organic bentonite were measured by rheometer. ResultsThe XRD spectra showed that the 001 reflection of bentonite was shifted to a lower 2θ after the modification. Moreover, the modification with DTAC had more pronounced effect than with DADMAC. The TGA curve showed that one dehydration stage in the range of 30–155°C was observed. For organic bentonite, thermal degradation took place in two stages. The first step was obtained in the temperature range of 250–600°C and the second step took place between 600 and 900°C. The addition of modified organic bentonite resulted in the increases of yield stress and viscosity of coating, and they increased when the amount of organic bentonite was increased. The flow characteristics fitted well with the Herschel–Bulkley model, and the rheological properties of paper coatings exhibited typical pseudoplastic behavior. Conclusion(1) The organic modifying agents were successfully inserted into the interlayer space of bentonite, the bonded amount of DADMAC and DTAC was 0.107g/1g Bent-DADMAC and 0.124g/1g Bent-DTAC, respectively; (2) organic bentonites had the thickening and promoting rheological function for paper coating; and (3) the paper coating containing organic bentonite exhibits the pseudoplastic fluid.

Removal of Rhodamine B with Fe-supported bentonite as heterogeneous photo-Fenton catalyst under visible irradiation

Fe-supported bentonite (Fe-B) was successfully fabricated as a low-cost heterogeneous catalyst for adsorption and visible light photo-Fenton degradation of Rhodamine B (RhB) from aqueous solution. The support of iron rendered a significant increase in specific surface area and a slight increase in interlayer spacing of bentonite, thus improving the adsorption performance of Fe-B. The maximum adsorption capacity of RhB onto Fe-B was calculated to be 227.27mgg−1 by the fitting of Langmuir adsorption isotherm. The catalytic activity of Fe-B was evaluated by the degradation of RhB (80mgL−1) in the presence of H2O2 under visible light irradiation. Light-emitting diodes (LED) lamps were used as visible light source as they are small in size, energy efficient, compact, have a relatively long life span, and can be facile to operate. The estimated quantum yield of photodegradation of RhB was calculated as (1.66±0.21)×10−2. The results showed that the Fe-B catalyst demonstrated good performance in the removal of RhB by combination of adsorption and degradation with optimum operating conditions of Fe-B 0.25gL−1, natural pH 4.2 and H2O2 12mM. The Fe-B catalyst retained high visible light photocatalytic activity toward RhB in a wide pH range from 3.0 to 9.0 and exhibited good chemical stability after five consecutive adsorption/degradation cycles.

A Sulfide Ion Sensor from Commercial Bentonite

Bentonite is a synonymous term of montmorillonite which is a clay mineral consisting of 2 : 1 aluminosilicate layered structure. In this work, a commercial bentonite was used to prepare an intercalation compound [Ca (2,2-bipyridine)3]2+ in the interlayer space, by solid-solid reaction, which formation was confirmed by the expansion of the interlayer space of bentonite from 1.5 to 1.8 nm, by powder X-Ray Diffraction technique. The intercalation compound [Ca (2,2-bipyridine)3]2+-bentonite was then used as a sensor to assemble a potentiometric electrode. The electrode gave best response to sulfide ion in terms of Nernstian slope. Precision of measurement, reproducibility and percent recovery were also studied. The electrode could be used to measure sulfide ion in real water samples and gave satisfactory results.

Adsorption of phenol from wastewater by organo-bentonite

Na–bentonite was modified via an ion-exchange reaction with hexadecyl trimethyl ammonium bromide (CTAB). X-ray diffractometer (XRD) indicated CTAB cations had exchanged with Na+ ions in Na–bentonite and the interlayer space of bentonite was increased. Batch adsorption tests were carried out to remove phenol from model wastewater using the modified bentonite, and the effect of amount of CTAB, contact time, pH, and adding quantity of modified bentonite were evaluated. The experimental results showed that the removal efficiency of phenol can be up to 81.36% under the following conditions: the amount of CTAB was 1.5 cation exchange capacity (CEC), the dosage of organic modified bentonite was 7 g/L, the adsorption time was 60 min, and the pH value was 7. The adsorption isotherms of organic modified bentonite for phenol-based wastewater met the Freundlich adsorption equation.

Synthesis of CdS/bentonite nanocomposite powders for H2 production by photocatalytic decomposition of water

Abstract A novel approach was used to synthesize CdS/bentonite nanocomposite powders by the one-step thermal decomposition of complex ion [Cd(NH 2 CSNH 2 ) 2 ] 2 + in the interlayer space of bentonite. XRD results demonstrated that the intercalation of CdS into the interlayer space of bentonite led to the expansion of layer spacing. The weight losses of the nanocomposite were via dehydration, decomposition of complex ion [Cd(NH 2 CSNH 2 ) 2 ] 2 + and dehydroxylation in the interlayer space of bentonite. Diffuse reflectance UV–visible spectra indicated that the absorption edge of the nanocomposites was blue-shifted as compared with bulk CdS due to the quantum size effect of CdS nanoparticles. The photocatalytic activity of hydrogen production for the nanocomposites was attributed to the synergistic effect between CdS and bentonite. A possible photocatalytic mechanism was proposed.

Removal of phosphate from natural waters using innovative modified bentonites

A modified inorganic bentonite (Zenith/Fe) based on natural bentonite with the code name Zenith-N, was prepared by embedding Fe ions in the interlayer space of bentonite. Bench-scale batch experiments were performed to examine its efficiency as an adsorbent for phosphate removal from natural waters. Phosphate uptake was evaluated vs. pH using adsorption kinetics and adsorption isotherms. The effects of temperature and salinity (fresh, brackish and marine waters) on phosphate-uptake capacity were also investigated. Comparative experiments were carried out for unmodified bentonite (Zenith-N) and a commercial product Phoslock (lanthanum modified clay). The results showed that phosphate-uptake capacity of Zenith/Fe [11.15mg/g, at pH=7] was improved by ~350% compared to unmodified bentonite (Zenith-N) [4.12mg/g, at pH=7] and was comparable to the phosphate-uptake capacity of Phoslock [11.60mg/g]. The optimal pH for phosphate adsorption ranged between 6 and 7. However, phosphate adsorption by Zenith/Fe and Phoslock appeared to be less pH-dependent than natural bentonite. Adsorption kinetics showed that over 80% of phosphate was removed from water within 1h. The resulting isotherms also fit well with Langmuir and Freundlich isotherm models. The increase in adsorption capacity of Zenith/Fe at higher temperatures was caused by the enlargement of pore size and/or activation of the adsorbent surface. Finally, the phosphate adsorption capacity followed the order: fresh water<brackish<marine water.

Characteristics of organobentonite prepared by microwave as a sorbent to organic contaminants in water

This paper put forward a microwave irradiation method to effectively prepare organbentonite, which aims to decrease time-consuming and energy-intensive in preparation of organobentonite by convention. The optimal conditions for preparing organobentonite by microwave (MOB) were studied. The mechanism of organobentonite prepared by microwave was proposed. Characteristics of MOB and organobentonite prepared by convention (COB) were compared in detail. An ideal amount of cetylpyridinium chloride (CPC) used for preparation of organobentonite was 1.0 times of cation exchange capacity (CEC) of bentonite. The optimal microwave irradiation time was 2 min. The preparation reaction time for organobentonite was decreased from several hours by convention to only a few minutes by microwave, which confirms that microwave method is very effectively for preparing organobentonite. XRD and atomic force microscopy (AFM) showed that the CPC moles have entered into interlayer spacing of bentonite. Comparing with natural bentonite, the intense endothermic peaks in differential thermal analysis (DTA)/Thermogravimetry (TG) curves of COB and MOB drifted to low temperature zone. Comparing with COB, the interlayer spacing of MOB was raised and the organic carbon content of MOB was increased 32.5% by microwave, which benefit to the sorption of organic compounds onto MOB from water.