Specific Surface Area Of Clay Research Articles

RSM optimization studies for cadmium ions adsorption onto pristine and acid-modified kaolinite clay

Clay has been reported as an active absorbent for the removal of toxic heavy metals from aqueous medium. In this study, pristine and acid modified kaolinite clays (PKC and AMKC) were prepared, characterized using various analyses, and tested for Cd2+ ion adsorption from textile industry wastewater. After acid modification, the specific surface area of clay increased from 84.2 to 389.4 m2/g. Adsorption isotherm, kinetics and thermodynamics behaviour process were examined. The pH at (pHpzc) of 8.5 indicate that AMKC surface is positively charged for pH below the pHpzc attracting anions. Response surface methodology was used to investigate the effect of adsorption process factors on Cd2+ ion removal uptake. At the optimum process conditions of 45.3 °C temperature, 0.63 g/L adsorbent dosage, and 120.9 min contact time, the percentages of Cd2+ adsorbed by PKC and AMKC were 77.82% and 99.19%, respectively. Various models were employed to analyzed the kinetic and equilibrium data. The Pseudo-first order, Pseudo-second order and Intra-particle diffusion were used to evaluate the kinetic data, while the Langmuir, Freundlich and Temkin isotherm models were applied to analyzed the equilibrium data. The sorption kinetics was found to be best described by Pseudo-second order considering the high correlation coefficient (R2), smaller Chi-square (ᵪ2) and sum of square error (SSE). The Freundlich model was the most accurate in describing the equilibrium data followed by Langmuir and Temkin respectively. The thermodynamic reveal that the reaction is spontaneous and endothermic in nature, and increase in randomness between the adsorbent and adsorbate. The obtained activation energy (Ea) value suggest that the adsorption mechanism of Cd(II) is a physisorption dominated.

Mineral characteristics of volcanic ash‐derived soils affecting boron adsorption

AbstractVolcanic ash‐derived soils are naturally deficient in the essential micronutrient B, but they also have maximum adsorption capacities (bB) that are as much as 40 times greater than in nonvolcanic soils, further exacerbating B availability. Because short‐range‐order (SRO) aluminosilicates (allophane and imogolite) and iron (Fe) oxyhydroxides are the main clay‐sized minerals in these soils, we hypothesized that their relative abundances would explain variations in boron sorption capacity (bB). We characterized 23 volcanic ash‐derived soils (Andisols and non‐Andisols) from the Pacific coastal plain of Guatemala by X‐ray diffraction, oxalate and pyrophosphate extractions, and thermal analysis, with four selected soils further examined by Mössbauer spectroscopy (MBS). Only soils with andic character (high SRO Si–Al content) contained considerable amounts of imogolite, with allophane in the clay fraction. Overall, soil SRO Al–Si phases were strongly correlated with clay B adsorption capacity (R = 0.65, p < 0.001) and clay specific surface area (R = 0.88, p < 0.001) suggesting that SRO Al–Si phases are the dominate influence on B behavior in these soils. Fe mineral composition was dominated (39%–71% of total Fe) by SRO Fe(III) oxyhydroxides (nanogoethite and ferrihydrite) of various crystallinities. In low allophane soils, SRO Fe phase abundance correlated with bB as did the abundance of low crystallinity kaolinite phases, suggesting these phases are important when SRO Si–Al content is low. Any efforts to predict B behavior or plan soil fertility treatments in volcanic‐influenced soils needs to consider the impact of SRO phases.

Role of silt and clay fractions in organic carbon and nitrogen stabilization in soils of some old fruit orchards in the Nile floodplain, Sohag Governorate, Egypt

PurposeStudy the effect of both silt and clay fractions on stabilizing organic carbon and total nitrogen in soils of some old cultivated fruit orchards in Sohag, Egypt.MethodsEleven surface soil samples (0–15 cm) were collected. Silt (63–2 μm) and clay (< 2 μm) fractions were separated from soils and analyzed for cation exchange capacity (CEC), organic carbon (OC), total nitrogen (TN), specific surface area (SSA), X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopic analysis were determined using the standard analysis methods.ResultsThe silt and clay were responsible for 77.49 to 93.34% of soil CEC. The SSA of clay was twice the silt, and the phyllosilicates (%) average was 29.83% and 62.70% in silt and clay. Other minerals, such as quartz, feldspar, and carbonate minerals, were detected in these fractions. The phyllosilicate species of clay were smectite-illite mixed layers (44.4–88.9%), Smectite (1.0–6.4% except one sample recorded 45.7%), Kaolinite (3.7–10.5%) and kaolinite/smectite mixed layers (2.0–8.2%). The average OC-silt and clay were 6.79 and 8.96 g OC kg−1 soil (38.01 and 50.28% of soil OC). On average, the total nitrogen (TN) in silt and clay particles was 0.817 and 1.156 g N kg−1 soil (35.88 and 50.66% of soil TN). The OC and N content significantly and positively correlated with CEC, SSA, and phyllosilicates in the fine fractions.ConclusionResults showed that the soil's capacity to sequester OC and N is affected significantly by its fine particles' content, characteristics, and mineralogy.

The analysis of clay soil shrinkage

The paper presents the analysis of the capillary and water-colloidal theories of clayey soil shrinkage. The method by which the volumetric shrinkage of the clay soil was determined is that the soil sample is made conical, with an angle at the top of 45-75º, and it is dried in a container geometrically similar to the sample with permeable walls. With kaolinite clays, the shrinkage process has a duration of one week, with hydromicaceous clay of around two weeks, and with montmorillonitic clays three weeks. There is a parabolic dependence between the duration of clay shrinkage and the specific surface area of clay. A series of experiments and calculations have been performed, based on Kulchitsky-Usyarov clay soil model, to determine the limit values of capillary pressure in montmorillonite, hydromicaceous and kaolinite clays using the Laplace formula. At the limit of normal shrinkage, the total porosity for Ca-montmorillonite is 0.45, for Ca-hydromica - 0.25, for Na-kaolinite - 0.385. Calculations showed that during shrinkage the capillary pressure reaches: for Ca-montmorillonite – 48.6 MPa; for Ca-hydromica 8 MPa; for Na-kaolinite - 5.2 MPa. The results obtained practically coincide with the results obtained by K. Terzaghi. Studies on the cyclic “moisture-drying” of clays selected at an experimental site in Ujar (Azerbaijan) showed that after the first “swelling-shrinkage” cycle, with secondary moistening, the swelling of the samples was 12-18 times higher than the primary value.

Oscillatory Briggs‐Rauscher Reaction as “Fingerprint” for Bentonite Identification: The Fine‐Tuning of Oscillatory Dynamics with Addition of Clay

AbstractThe oscillatory Briggs‐Rauscher (BR) reaction was applied on solid insoluble materials i. e. bentonite clays. Under the same BR experimental conditions, the addition of identical masses of bentonite of different origin resulted in different effects on oscillatory time duration (τ): no influence, quenching, or prolongation. It was found that the following bentonite properties: montmorillonite/beidellite ratio; cation exchange capacity; principal exchange cation; extent of iron leaching in acidic environment of BR reaction; and specific surface area of clay were not exclusively responsible for observed behavior. On the other hand, the influence of added mass, for all investigated clays, resulted in the same behavior pattern. The increase of the mass of added clay increased τ up to the certain maximal value (τmax, mmax) characteristic for each clay. Further increase of mass resulted in quenching. Therefore, (τmax, mmax) pair can be regarded as the “fingerprint” characteristic of bentonite useful for identification of its origin. Furthermore, the addition of naturally occurring and non‐toxic clay in an oscillatory reaction can offer a versatile approach to tune the oscillation dynamics of nonlinear chemical systems.

Effect of acid activation on the CO2 adsorption capacity of montmorillonite

Montmorillonite, a natural and abundant clay, was subjected to acid treatments in HCl solutions for different times to enhance its physicochemical properties for CO2 adsorption. Acid activated montmorillonites were characterized by elemental analysis, XRD, FTIR, nitrogen physisorption, TGA, and NMR to evaluate the physicochemical changes due to the acid treatment. Besides, these samples were examined as CO2 adsorbents, evaluating the influence of the modified textural characteristics on the affinity of montmorillonite towards CO2 capture. After 3 h of acid treatment, the specific surface area of clay increased from 39 to 202 m2/g, while the pore volume increased from 0.05 to 0.31 cm3/g. CO2 adsorption isotherms were carried out at 0, 15, and 30 °C, showing that acid activated clays were much more efficient for CO2 adsorption than raw materials. Further studies on the CO2 adsorption process were performed: experimental equilibrium data were correlated by using Langmuir, Freundlich, and Sips models, and the isosteric heat of adsorption was calculated from the Clausius–Clapeyron equation.

In-Situ Determination of Specific Surface Area of Clays

There are many methods to determine the specific surface area (SSA) of clay minerals. Some of these methods lack accuracy and some are time consuming. There are no methods available for the determination of in situ SSA. In this paper a new approach to predict the SSA of clays is proposed, which has been verified in the laboratory. This method is based on the electrical properties of soils. In this paper the experimental set up and the estimation of specific surface area is presented on the basis of variation of the dielectric constant and the conductivity of the clay–water system when subjected to alternating current in the frequency range of 1–100 MHz. The dielectric constant and conductivity respond differently for different soils with varying surface area corresponding to their mineralogy. When dielectric constants and conductivity were measured for sandy soils, there were no effects with the change of input frequency. The electrical method can identify clays and separate them from fine grained silts. Data are presented which shows a linear correlation between the magnitude of dielectric dispersion and SSA for various clay mixtures. The clay structure determines the value of in situ dielectric dispersion of the clay (Δeo) and hence the SSA, making this a good in situ method to estimate SSA of clays.

Impact of Exposure to Pressure of 50 MPa on the Specific Surface Area of Clay

The paper presents results of laboratory tests conducted to determine the impact of pressure of 50 MPa on specific surface area of clay. These tests were carried out in an original, high-pressure test stand. The specific surface area of clay extracted directly from an open pit mine was compared with the specific surface area of the same clay subjected to the pressure of 50 MPa in a high-pressure chamber. The study found that the specific surface area of the clay subjected to the pressure of 50 MPa increased distinctly by over 35 %. The increase in specific surface can be a result of changes in the microstructure of clay particles and microstructural alteration in the soil skeleton, caused by the pressure.

Effect of polycarboxylate superplasticiser adsorption on fluidity of cement–clay system

Clay reduces fluidity and increases fluidity loss of concrete added with polycarboxylate superplasticiser. Sometimes it cuts down concrete durability. Fluidity of clay–cement paste with the addition of polycarboxylate superplasticiser, adsorption amount of polycarboxylate superplasticiser and ζ-potential has been tested to understand the effect of polycarboxylate superplasticiser on cement–clay systems. The results show that cement particles have a smooth surface; there are lots of layered or sheet structure existing on the surface of clay; when the particle size distribution is little different, the specific surface area of clay is 17 times that of cement; it is the reason why polycarboxylate superplasticiser adsorption on clay is much greater than that of cement. Initial adsorption amount and equilibrium adsorption amount of polycarboxylate superplasticiser on clay are 3–4 times that of cement; strong PC adsorption of clay is the main reason why the presence of clay reduces fluidity and increases fluidity loss of cement paste.

The Effect of 200 MPa Pressure on Specific Surface Area of Clay

Abstract The paper presents the results of laboratory studies of the 200 MPa pressure effect on specific surface area of clay. The original high-pressure investigation stand was used for the pressure tests. Determination of the specific surface area was performed by the methylene blue adsorption method. The results of the specific surface area test were compared for non-pressurized clays and for clays pressured in a high-pressure chamber. It was found that the specific surface area of pressurized soil clearly increased. This shows that some microstructural changes take place in the soil skeleton of clays.

Specific Surface Area of Clay Using Water Vapor and EGME Sorption Methods

Specific surface area (SSA) is a valuable intrinsic property of clayey soils that can be directly related to more general properties and engineering behavior, including plasticity, cation exchange capacity, and swelling behavior, among many others. Laboratory methods available for estimating SSA, however, remain somewhat complicated and are not routinely used in geotechnical practice. This paper evaluates and compares methods for determining SSA using the conventional ethylene glycol monoethyl ether (EGME) method and various approaches involving sorption of water vapor under controlled humidity conditions. Surface areas estimated from water vapor adsorption and desorption isotherms are comparable for non-expansive clays with SSA values less than about 100 m2/g. Measurements are appreciably different for soils containing expansive clay minerals, where the SSA estimated via Brunauer–Emmett–Teller (BET) analysis of desorption isotherms is consistently about twice the SSA determined from adsorption isotherms. Surface areas estimated from water vapor and EGME methods are comparable at SSAs less than 100 m2/g, but measurements obtained using water vapor for larger SSAs are consistently about half of the EGME-based values. Simplified one-point methods for estimating SSA using water vapor sorption compare well with BET-based methods for SSAs less than 150 m2/g. Recommendations are provided for applying water vapor and EGME sorption methods in geotechnical practice.

Preparation and characterization of nano porous bentonite for regeneration of semi-treated waste engine oil: Applied aspects for enhanced recovery

Abstract The present investigation studies the regeneration of waste engine oil by active Ca-bentonite powder. The porous adsorbents were prepared by acidification in the presence of nitric and sulfuric acid solutions at different residence times. The methylene blue adsorption test was applied to evaluate the acidification. The characteristics of normal and treated powders were also characterized by ICP, XRD, FTIR and BET techniques. The optimum condition was determined in which the methylene blue adsorption reached the maximum value. In this condition, the specific surface area of clays activated in the presence of nitric and sulfuric acids were determined to be 109.0 and 89.0 m2 g−1, respectively. The change in specific surface area was found to be due to formation of new nano-pores in the range of 10–12 nm, according the N2 adsorption isotherms. The feasibility of active powders for removal of contaminants from waste oil has been studied in the next part. The modified powders had higher adsorption capacity for removal of contaminants from waste oil. It was demonstrated that the adsorption of methylene blue by active clay yields the valuable information about minimizing the powder content in recovery of waste oil by semi-treated process.

A comparison of methods used to characterize the soil specific surface area of clays

In the present study the dry end of the soil water characteristic curve (SWCC) was used to estimate the specific surface area (SSA) of 90 engineering soil samples, using the Tuller and Or (2005) model. The results of SSA obtained by measurements using a WP4-T dew point potentiometer were compared with those obtained by means of traditional BET (Brunauer, Emmett, and Teller) surface area and the methylene blue (MB) techniques. An analysis of the results discussed in terms of the representative literature data showed that the SWCC method could provide a reliable estimation of the specific surface area in the case of fine grained inorganic soils with a total specific surface area greater than 5m2/g. A Hamaker constant with a value of 6×10−20J was found to be a good approximation, in the case of SSA calculations. The study also shows that karstic clay — terra rossa exhibits specific behavior which was not investigated in detail in the study, but clearly shows that further research is needed in order to modify the Tuller and Or (2005) model to a wider range of engineering soils with more complex mineralogical composition and texture.

A Direct SAXS Approach for the Determination of Specific Surface Area of Clay in Polymer-Layered Silicate Nanocomposites

The interfacial area between the matrix and the filler is a key parameter which shapes the performance of polymer-based composites and nanocomposites, even though it is difficult to quantify. A very easy SAXS method, based on the Porod equation, is proposed for measuring the specific surface area of nanofillers embedded in a polymer matrix. In order to assess its reliability, this approach was applied to natural rubber- or styrene butadiene-based samples containing different types of montmorillonite clay. A wide range of specific surfaces was detected. SAXS data were compared to complementary X-ray diffraction and TEM information, obtaining a good agreement. Interpretation of the tensile properties by theoretical models and comparison with the literature corroborated the validity of the specific surface area measurement. The possibility to quantify this feature of composites allows the rational design of such materials to be improved.

Estimating the fully developed diffuse double layer thickness from the bulk electrical conductivity in clay

The possibility of estimating the thickness ( t) of the fully developed diffuse double layer (DDL) and the specific surface area ( S) of clay from its bulk electrical conductivity (the composite electrical conductivity of the clay–water–air mixture), hereafter called the electrical conductivity and denoted by EC, was investigated. The assumption is that when a clay is wetted with distilled water, the fully developed DDLs around the clay particles create the maximum number of electrically conductive pathways that provide the highest electrical conductivity of the clay. This assumption was tested by measuring the electrical conductivity of 17 samples of different clays over a wide range of water content by time-domain reflectometry (TDR), and by using 2 relevant sets of data from the literature. Good agreement between the thicknesses of the DDLs estimated from the water content at fully developed DDLs, hereafter called the critical water content and denoted by w, and that calculated by the method of Schofield [Schofield, R.K., 1947. Calculation of surface areas from measurements of negative adsorption. Nature (London) 160, 408−410] for different samples proves the validity of our assumption. The critical water content being a direct function of the specific surface area of the clay and the thickness of the fully developed DDLs, provides a way of estimating any one of these two parameters when the other parameter is known. When the clay is wetted with salt solutions, the bulk electrical conductivity is governed by the electrical conductivity of both the DDLs as well as the salt solution outside the DDLs, and the above assumption does not hold true under such condition.

Measurement of the Specific Surface Area of Clays by Internal Reflectance Spectroscopy

AbstractThe specific surface area, S, of a clay is commonly measured by the adsorption of ethylene glycol monoethyl ether (EGME); however, this method can be tedious and time consuming, especially if the clay is saturated with a monovalent, highly hydrated cation. An alternative method for measuring S was developed involving infrared internal reflectance spectroscopy. This method is based on the discovery that the ratio of R1, the reflectance of a clay-HOD mixture at the frequency of O-D stretching, to R2, the reflectance of the mixture at the frequency of H-O-D bending, is linearly related to S. The correlation coefficient between R1/R2 and S, as measured by the adsorption of EGME, was 0.995. Consequently, a calibration curve of R1/R2 versus S was constructed, and the measured values of R1/R2 for any clay-HOD mixture were referred to it for the determination of S. Results were obtained in triplicate in about an hour; hence, this method of determining S is more rapid and convenient than that involving the adsorption of EGME. Moreover, it applies to clays in a natural condition, i.e., swollen in water.

The specific surface area of clays in lake sediments‐measurement and analysis of contributors in Lake Kinneret, Israel1

The specific surface area of Recent sediments of Lake Kinneret was measured and the contributions of various sediment components to it were evaluated. Most of the lake sediments had specific surface areas larger than 100 m2 g−1. Average SSA of the sediments is 181.8 ± 59.7 m2 g−1, whereas that of the noncarbonate fraction, constituting on the average 54.8 ± 12.3% by weight of the sediment, is 374.6 ± 106.9 m2 g−1. Despite their high proportion in the sediment, carbonates contribute only a very small fraction of the specific surface area; clay minerals in the 0–2‐µ size fraction, particularly smectite, contribute most of it.

The apparent and partial molal volumes of K-montmorillonite

AbstractThe partial and apparent molal volumes of K-bentonite in pure water and in 0·5 M KCl were determined using pycnometer density data. The values obtained were found to increase with particle concentration. Theoretical values of the electrostatic contribution to the volume of particles calculated from an assumed model based on the electric double layer theory, gave values different from those found experimentally. This is explained as due largely to the uncertainties in the value of the clay specific surface area as well as to the assumed ideality of the model used.