Determination Of Cation Exchange Capacity Research Articles

The effect of ammonia activation on the desalination potential of natural zeolite

Despite the abundance of water bodies on Earth, there is a limited amount of potable water. Therefore, the desalination process is of great interest. Adsorption of the main contaminants of saline water (Na+, K+, Cl– ions) is an alternative process of desalination. In the present work, a sorbent based on natural zeolite (NZ) modified with ammonium chloride (NH4Cl) is obtained and the effect of modification on the removal of Na+ and K+ ions from saline water is studied. According to the Brunauer-Emmett-Teller (BET) analysis, the modification of zeolite with NH4Cl leads to an increase in its surface area (7.85 to 8.09 m2/g). According to the results of the cation exchange capacity (CEC) determination, the modification leads to a decrease in total CEC of zeolite (431.67±29.01 to 300.88±31.86 meq/100 g). According to the obtained results, ammonia modification enhances the adsorption ability of NZ to extract Na+ and K+ ions from saline water. The extraction degree (E) of Na+ ions by NH4-Z increases from 7.93±1.63 to 10.44±1.52%, while for K+ ions it increases about 2 times (27.69±2.45 to 56.46±3.71%). These results indicate that the ammonia-modified NZ can potentially be used as a desalination agent for the removal of Na+ and K+ ions from saline water.

Sorption study of long-lived 94Nb on laterite: Effects of physicochemical parameters on sorption

Zr–Nb alloy is used as the pressure tube in pressurized heavy water reactors (PHWR). Prolonged neutron irradiation of the pressure tubes leads to the formation of a long-lived radioisotope 94Nb. Thus, the discharged pressure tubes possess huge 94Nb activity which persists for a prolonged period.If these discharged pressure tubes come in contact with ground water, 94Nb isotope may leach and migrate and this can lead to a long-term radiological impact in the environment.In the present study, we have explored the capability of laterite as a filler material for the containment and retarding the migration of 94Nb. In this regard, detailed characterization of the laterite soil was carried out using energy dispersive X-ray fluorescence (EDXRF), X-ray diffraction (XRD), fourier transform infra-red spectrometry (FTIR), total cation exchange capacity determination, zeta potential measurement and thermogravimetric analysis (TGA). The sorption study of 94Nb on laterite was carried and the effects of different physico-chemical parameters like pH, ionic strength, temperature and equilibration time were evaluated. Ionic strength, temperature and time dependent sorption studies assist to explore the probable sorption mechanism of 94Nb on laterite, which helps in understanding the migration behaviour of 94Nb in natural aquatic environment. This study suggests that laterite is a promising material in containment of 94Nb isotope owing to its good cation exchange behaviour in the acidic medium and ability to form surface complex in the neutral medium.

Mapping Cation Exchange Capacity (CEC) Across Sugarcane Fields with Different Comparisons by Using DUALEM Data

The sugarcane growing soil in far-north Queensland is sandy, and infertile. To ensure productivity, nutrient guidelines recommend lime application rates based on soil cation exchange capacity (CEC). However, laboratory determination of CEC is expensive. Because CEC is often correlated with soil apparent electrical conductivity (ECa, mS/m) measured from electromagnetic induction (EM) instruments, ECa can be used to predict CEC. Using ECa may lead to uncertainty in prediction, but estimates of true electrical conductivity (σ, mS/m) generated from inversion of ECa, can be correlated with depth-specific CEC. In this study, we compared linear regression (LR) between ECa from a DUALEM-421S and CEC at specific depths ( i.e., topsoil [0–0.3 m], subsurface [0.3–0.6 m], subsoil [0.6–0.9 m] and deep subsoil [0.9–1.2 m]), with a LR of σ using a quasi-2d (q-2d) or quasi-3d (q-3d) inversion of DUALEM-421S ECa and CEC at all depths. The use of a multiple linear regression (MLR) to predict CEC, using σ with depth and location ( i.e., Easting and Northing) is also explored along with σ from the other EM products ( i.e., DUALEM-1S and DUALEM-21S). The minimum number of calibration sample locations ( i.e., n = 165, 150,…, 15) is also investigated. The LR between ECa ( e.g., 1mPcon) and CEC were very weak (R2 = 0.27) and weak (0.36) in the topsoil and subsurface, respectively, but moderate in the subsoil (0.57) and deep subsoil (0.67). The LR between σ, estimated from q-2d (R2 = 0.66) and q-3d (0.64) inversion of DUALEM-421S ECa, and CEC at all depths was moderate. In terms of prediction agreement, the Lin's concordance correlation coefficient (LCCC) was moderate for q-2d (0.79) and q-3d (0.75). Using a MLR with depth, coordinates and σ, led to an improvement in calibration using q-2d (R2 = 0.71) or q-3d (0.67), with prediction agreement substantial for q-2d (LCCC = 0.83) and moderate for q-3d (0.78), with comparable agreement from DUALEM-1S and DUALEM-2S (0.77) estimates of σ. The minimum number of calibration samples for a strong MLR R2 (>0.7) and substantial and good agreement was 15 for q-2d and 30 for q-3d, respectively. The final digital soil mapping of topsoil CEC developed using MLR and σ estimated from q-3d of DUALEM-421S ECa could be used to apply the Australian sugarcane industry lime application guidelines with areas with intermediate (3–6 cmol[+]/kg) and small (<3 cmol[+]/kg) topsoil CEC requiring 4 and 2.25 t/ha, respectively.

Determination of Cation Exchange Capacity of Calcareous Soils: Comparison of Summation Method and Direct Replacement Method

ABSTRACT The purpose of this study was to compare cation exchange capacity (CEC) values obtained by direct measurement and by summing the exchangeable base cations (EBCs) in calcareous soils. The seven soils used in this study were collected in Nassau, Bahamas, and in south Florida. The collected soils were analyzed for pH, organic matter, calcium carbonate, CEC, and EBCs. The CEC was determined using Bower’s method with slight modification, which featured 1 M sodium acetate at pH 8.2 as saturating solution, 70% ethanol for washing, and 1 M ammonium acetate at pH 8.2 for extracting adsorbed sodium ions. The extracted sodium ions were quantified using an inductively coupled plasma-optical emission spectrometer (ICP-OES). The exchangeable base cations were extracted using 1 M ammonium acetate solution at pH 8.2 and quantified by ICP-OES. The cation exchange capacity values determined by the direct method and summation method were comparable for all the soils used in this study. Summation CEC was not significantly different from the measured CEC (p < 0.05) for all the soils. These results imply that the summation method based on EBCs extraction with 1 M ammonium acetate at pH 8.2 may be a viable choice for soil testing laboratories to accurately estimate CEC in calcareous soils.

Elements’ Content in Stream Sediment and Wildfire Ash of Suburban Areas in West Attica (Greece)

The composition of sediments and other materials occurring in streams, geochemical processes within the drainage basin, and various land uses are among the main factors influencing stream water composition. Stream sediment and wildfire ash samples were gathered from the area studied. The applied methodology consists of aqua regia and Diethylene-Triamine-Penta-Acetic acid (DTPA) chemical extraction; Cation Exchange Capacity (CEC), pH, and soil organic matter (OM) determination; a Geographic Information System (GIS) database; factor analysis; and determination of the contamination factor (CF) for the assessment of contamination degree. This study aimed to evaluate the elements’ content in stream sediments of Kineta and Nea Peramos areas (West Attica, Greece) and investigate any relationship between elements (aqua regia and DTPA extracted) in stream sediment and ash in wildfire and flood-impacted areas. The stream sediments’ properties, the bioavailable forms of copper (Cu), iron (Fe), manganese (Mn) and zinc (Zn), and the total content of other potentially toxic elements in wildfire ash samples, are discussed. This research estimated moderate contamination for FeDTPA, MnDTPA and ZnDTPA in stream sediments of the study area. Contamination for CuDTPA and moderate contamination for ZnDTPA in the stream sediments of the Nea Peramos area was recorded. Factor analysis results suggested that the contents of FeDTPA, MnDTPA, CuDTPA and ZnDTPA in the study area’s stream sediments may affect the chemistry of stream water.

Estimating cation exchange capacity and clay content from agricultural soil testing data

Clay content and the ability to reversibly retain cations affect many essential chemical and physical properties of soil, such as pH buffering and carbon sequestration. Cation exchange capacity (CEC) and base saturation are also commonly used as criteria in soil classification. However, determination of CEC and particle-size distribution is laborious and not included in routine soil testing. In this study, pedotransfer functions including soil test cations (STCat; Ca2+ + Mg2+ + K+), pH and soil organic carbon (SOC, %) as explanatory variables were developed for estimating CEC, titratable acidity (TA; H+ + Al3+) and clay content (clay, %). In addition, reference values for potential CEC and its components were determined for Finnish mineral and organic soils. The mean of potential CEC extracted by 1 M ammonium acetate at pH 7.0 ranged from 14 (range 6.4−25) in coarse soils to 33 (21−45) cmol(+) kg-1 in heavy clay soils, and from 42 (24−82) in mull soils to 77 (25−138) cmol(+) kg-1 in peat soils. The average CEC of clay and SOC were 27 and 160 cmol(+) kg-1, respectively. Titratable acidity occupied 53% and around 40% of the CEC sites in organic and mineral soils, respectively, evidencing that it is a prominent component of the potential CEC in these predominantly acidic soils. STCat, pH and SOC explained 96% of the variation in potential CEC. STCat and pH can be used in estimating the clay content especially for soils containing over 30% clay. In coarse textured soils, in contrast, SOC hampers the STCat based estimation of clay content.

Evaluation of Mehlich‐3 for determination of cation exchange capacity in Kansas soils

AbstractSoil testing laboratories across the United States have implemented the Mehlich‐3 (M3) extraction method for phosphorus (P) and other nutrients. Though M3 is known to work well as a multinutrient extractant, it raises concerns for measuring exchangeable cations, particularly in calcareous soils. The objectives of this study were (a) to evaluate M3 as an extractant for base cations for Kansas soils, (b) to identify a range of soil pH where M3 may be a suitable replacement for ammonium acetate (AA), and (c) to examine the relationship between cation exchange capacity (CEC) summation and CEC displacement. A study was conducted evaluating 308 soils collected from across Kansas and extracted using both the M3 and AA soil extraction methods. Cation exchange capacity was estimated using the summation approach from measurements of both the M3 and AA, and the displacement method. Results indicate a strong correlation among M3 and AA methods for K, Mg, and Na (R2 = .98, .96, .97, respectively). However, these relationships were considerably weaker for extractable Ca (R2 = .78), where extractable Ca was higher in the M3 extracts for high pH soils. Estimated CEC was also affected by soil pH for the M3 method, with an estimated critical pH value of 7.3. Extractable Ca and CEC for soils with a pH below 7.3 showed a strong correlation between M3 and AA methods (R2 = .9). Using M3 as a multinutrient extractant can improve turnaround time for sample analysis in soil testing laboratories. However, the use of the M3 procedure in soils with a pH of 7.3 or above will likely result in overestimation of exchangeable Ca and CEC.

PERFORMANCE OF LINEAR MODELS IN PREDICTING CATION EXCHANGE CAPACITY OF CALCAREOUS SOILS

Determination of soil cation exchange capacity (CEC) in lab is cumbersome, time consuming, and costly. Accordingly, this article attempted to formulate pedotransfer functions for predicting it using some soil physical and chemical properties e.g., sand (SA), silt (SI), clay (CL), organic matter (OM) and calcium carbonate (CC). This research included four steps: preparing soil database; selecting independent variables which are related to CEC value; formulating models using NCSS 12.0.2 software, and the last step is to achieve specific objective of the research which is the comparsion among models by a series of efficiency criteria: root mean square error (RMSE), Nash-Sutcliffe model efficiency coefficient (EF), average absolute percent error (AAPE), and percentage of improving model efficiency (PIME). The statistical results of the research indicated that CEC of calcareous soils could be predicted from models that have one variable (CL), two variables (CL and OM), and three variables (CL, OM, and CC) with slight decrease in the RMSE (2.95402, 2.81180, and 2.79268) respectively, and slight increase in the EF (0.887360, 0.898448, and 0.90023) respectively. While the reliable models to predict soil CEC are formulated from the fewer number of independent variables with having the lowest points of the standardized residual of CEC that greater than +2 cmolc kg-1).

Vermiculite enriched by Fe(III) oxides as a novel adsorbent for toxic metals removal

Expanded vermiculite (EV) was modified by deposition of different spinel ferrite composites on the outer surface of EV 2:1 layers in order to improve its adsorptive properties. Modifications were made by deposition of: magnetite, manganese ferrite, cobalt ferrite and chromium oxide/hematite. The characterization of modified materials was performed by: scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) methodology, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), magnetization measurements, as well as determination of cation exchange capacity (CEC) and pH point of zero charge (pHPZC). Obtained samples were used as adsorbents for Pb2+, Ni2+and Cd2+ ions from an aqueous solution in a batch system. Results showed that adsorption capacity was strongly dependent on physical and chemical changes induced by specific chemical modification. Hydrothermally produced manganese and cobalt ferrites caused significant surface changes and altered the interlayer cation balance. Among the others, EV-Mn/Co-ferrite(s) samples possessed the highest adsorption capacity towards Ni2+ (33.06 mg g-1), along with an increase of the CEC. Freundlich's adsorption isotherm model provided the best fit of obtained experimental data, while kinetic studies showed that the adsorption rate follows the pseudo second-order model, implying heterogeneous adsorbents surface. Thermodynamic and kinetic parameters indicated that the mechanism of cations removal efficacy was dominantly followed by the ion exchange. This study confirmed that doped ferrites, produced by solvothermal method, improve surface properties of EV and increase adsorption potentials towards heavy metals.

Predicting biochar cation exchange capacity using Fourier transform infrared spectroscopy combined with partial least square regression

Determination of cation exchange capacity (CEC) in biochar by applying traditional wet methods is laborious, time-consuming, and generates chemical wastes. In this study, models were developed based on partial least square regression (PLSR) to predict CECs of biochars produced from a wide variety of feedstocks using Fourier transform infrared spectroscopy (FTIR). PLSR models used to predict CEC of biochars on weight (CEC-W) and carbon (CEC-C) basis were obtained from twenty-four biochars derived from several origins of feedstock, as well as compositions and mixtures, including four reference biochar samples. Biochars were grouped according to their CEC-W values (range of 4.0 to 150 cmolc kg−1) or CEC-C values (range of 6.0 to 312 cmolc kg−1). FTIR spectra highlighted features of the main functional groups responsible for biochar's CEC, which allowed a high prediction capacity for the PLSR models (R2pred ~ 0.9). Regression coefficients were associated to spectral variables of the organic matrix polar functional groups that contributed positively and negatively for biochar CEC. Phenolic and carboxylic were the main functional groups contributing to a higher biochar CEC, while CH and CC groups decreased the density of negative charges on the charred matrices. Chemometric models were highly robust to estimate biochar CEC, mainly on a weight basis, in a fast, reliable and economic way, compared to CEC conventional laboratory methods.

Determination of cation exchange capacity and analysis of cation availability in hemic and sapric peat with different preparation and extraction methods

The use of mineral soil analysis procedures in peat soils is considered unsuitable. Peat soil is vulnerable to disturbance, which leads to the damage of peat inert structure, such as the sifting and drying process. The objective of this study was to obtain the proper methods of preparation and extraction to be used in peat soils that can reflect the conditions on field. The experiment was carried out in the laboratory of Soil Science Department UGM by using the peat soil samples taken from Padang Island, Riau, arranged in a factorial randomized block design with three factors (peat soil preparation, the extraction method, and the levelof peat maturity). The variables observed included the available cation and Cation Exchange Capacity (CEC) of the peat soil. The results showed that there was no significant effect of the treatment interactions on each variable observed. The preparation method for original soil at each level of peat maturity reflected more of the physical condition on the field more than other methods. Meanwhile, sapric peat showed significant effect on cations and CEC. After being converted to bulk density (BD) values at each level of peat maturity, the result of the leaching extraction method showed that the value of available cation and CEC that reflected more of the value on the field. The peat soil analysis method should be carried out without air drying and shaking extraction treatment for further research.

Probabilistic estimation of specific surface area and cation exchange capacity: a global multivariate distribution

Specific surface area (SSA) and cation exchange capacity (CEC) are two fundamental clay properties. However, the determination of CEC and SSA is challenging due to inherent uncertainties and difficulty in experimental measurement. A popular approach is to employ transformation models for their estimation. However, most of the existing models were developed on limited sample sizes and quantification of uncertainty associated with the estimate is not possible. Therefore, this study proposes a multivariate probabilistic approach for estimation of CEC and SSA. First, a five-dimensional database (278 × 5) for the parameters liquid limit (LL), plasticity index (PI), clay fraction (CF), CEC, and SSA (labelled as CLAY/C-S/5/278) is developed. Thereafter, multivariate distribution for the five parameters in the database is constructed using the vine copula approach. Implementation of the proposed approach is demonstrated by updating the prior–unconditional probability density functions (PDFs) of CEC and SSA given single or multiple clay parameters using Bayes’ rule. The posterior or conditional PDFs of CEC and SSA are also summarized as practitioner-friendly analytical expressions. Two geotechnical application examples are shown as well. In the proposed approach, CEC and SSA are characterized by their complete joint distribution and therefore this approach is superior to the popular deterministic transformation approach in literature.

Experimental features of cation exchange capacity determination in organic-rich mudstones

To the petroleum industry, the cation exchange capacity (CEC) is one of the critical petrophysical parameters of the rock-gas-fluid system and the response of well logging tools. The widely used laboratory protocols for CEC determination (wet chemistry methods) came mainly from soil science, but with slight or even without modifications are being applied to organic-rich mudstones (shales). However, using such laboratory practice leads to large CEC errors in the presence of carbonate and gypsum minerals, high-salinity pore water, etc.The paper attempts to find optimal in terms of accuracy and reliability methods for measuring both CEC and exchangeable cations concentrations of organic-rich mudstones, along with sample treatment procedures including drying, extraction, and fraction size due to crushing. The paper presents a CEC data set obtained using both hexaamminecobalt(III) chloride (CoHex) and modified (NH4Cl)Alc methods for a representative collection of core samples of the Bazhenov shale formation (West Siberia, Russian Federation). The results show a) CEC growth inversely versus fraction size, and b) stable CEC measurements within fraction size 0.25–1.0 mm. The BET specific surface area (SSA) spans in the range of 0.25–6 m2/g. SSA follows the CEC trend in terms of fraction size with a growth ratio up to 3 times. The modified (NH4Cl)Alc method outperforms the CoHex method and reliably determines the concentrations of the exchangeable cations for a carbonate content of more than 5 wt%. Both direct [Co(NH3)6]3+ measurements in the CoHex method and the sum of exchangeable cation concentrations in the modified (NH4Cl)Alc method provide a fair estimate of the total CEC. Careful sample preparation, including drying or solvent extraction, is required for accurate CEC determinations. The measured CEC for the target rock samples varies from 2.87 to 6.43 cmol/kg and driven by the total clay content.

Potential Application of Laser‐Induced Breakdown Spectroscopy (LIBS) Data for the Determination of Cation Exchange Capacity (CEC) of Agricultural Soils

AbstractThe potential for Laser Induced Breakdown Spectroscopy (LIBS) technique to predict cation exchange capacity (CEC) values in agricultural soils, based on a partial least square (PLS) regression model, was investigated by analysing soils (N= 225) using a portable LIBS system. The prediction from the validation set was 0.75 and the RMSE was 5.4 cmol+/kg. Analysis of the PLS loading weights showed that emission lines that correlate with the exchangeable cations (Ca, Mg, K and Na) and clay (Al and Si) are significant. Good quality predictions could be obtained from the model as described by the ratio of performance to deviation (RPD) values calculated for calibration (RPDc =1.99) and validation (RPDv=2.02). The ratio of performance to interquartile distance (RPIQ) for calibration (RPIQc=3.20) and validation (RPIQv=3.32) indicated excellent prediction capability. It has been demonstrated that LIBS spectra coupled with multivariate data analysis could be used to predict CEC of agricultural soils which is considered fast and a chemical‐free technique.

Smectite quantification in hydrothermally altered volcanic rocks

In volcanic environments, the presence of smectite may indicate recent hydrothermal circulations. Smectite is also responsible for enhanced rock electrical conductivity, as well as mechanical weakening. Therefore, quantifying smectite is important in geothermal exploration. Smectite identification requires X-ray diffraction (XRD) but quantification based on XRD is time-consuming and not always accurate. In the present study, we investigate the use of an optimized unbuffered Cation Exchange Capacity (CEC) determination, by back-titration of the Copper-triethylenetetramine(II) “Cu-trien” molecule, to quantify the smectite content of altered volcanic rock samples. We establish that a satisfying trade-off between the instrument uncertainty and an independant systematic error is theoretically reached for a fraction of reactants consumed of about 30% at the end of the exchange reaction. We suggest a modification to classical protocols to fall in that range. Finally, we show that optimized CEC determination by Cu-trien are a direct measure of the smectite weight fraction in altered volcanic samples, with an average CEC of pure smectite of 90 ± 5 meq/100 g.

In-Situ Synthesis of Polymer–Clay Nanocomposites: Exfoliation of Organophilic Montmorillonite Nanolayers in Poly 2-ThiozylMethacrylamide

The aim of this work is the preparation and properties of poly 2-thiozyl methacrylamidevinylbenzyldimethyloctadecylammonium/montmorillonite (TMAAm-VBOA/MMT) nanocomposites. Firstly 2-thiozyl methacrylamide (TMAAm) monomer was synthesized by reacting 2-amino thiazole with methacryloyl chloride in the presence of triethylamine. Synthesis of nanocomposites were performed in three steps which are; purification and cation exchange capacity (CEC) determination of clay, preparation of organoclay and synthesis of nanocomposites. Nanocomposites with various amounts of TMAAm and VBOA/MMT were synthesized through in-situ and free radical polymerization using benzoyl peroxide as an initiator. Changes in the structure of the nanocomposites were examined through Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). Additionally, thermogravimetric analysis and BET analysis were conducted to investigate the thermal properties and particle size distribution of the nanocomposites. The results of X-ray and SEM analysis suggest that the exfoliated structure of the new nanocomposite materials. In addition, the thermal decomposition temperatures of nanocomposites were found to be higher than that of pure organoclay and poly(TMAAm) and thermally degradation rate decreased.

Non-woven composites intensification properties for air filters by plasma pre-treatment

The nonwovens use in the automotive industry has increased significantly. Nonwovens for air filters can be changed in a desired direction to have specific properties. The use of non-woven textiles in the automotive industry has the following advantages: it reduces the weight of the vehicle, increases comfort and provides improved insulation, fire retardancy and resistance to water, fuels, extreme temperatures and abrasion. The electrospinning process is one of the nanofibres, two-layer and multilayer composites with their participation obtaining methods. The low frequency plasma surface modification of needle-punched polyethilenthereftalat (PET) nonwoven fibres is good possibility to intensification the process and the rate of increase of the mass of nanolayer regarding to its’ hydrophobicity. The plasma physicochemical treatment type allows adhesion change and change of electro physical properties at the expense of new active centres formation that do not exist in the native fibre. In this study, different gases (Ar, O2 and air) and electrical conditions were employed. The surface changes of PET fibres were investigated by cation exchange capacity (CEC) determination and its influence on the mass nanofibres increase rate. Observation revealed the plasma treatment significantly change surface wettability of PET fibres. The effect of caused change on the electrospinning process is analysed.

Critical issues in the determination of the bentonite cation exchange capacity

The swelling pressure and transport properties of bentonites are controlled by the electric charge density of solid particles, which is commonly estimated from the laboratory measurement of the cation exchange capacity (CEC). However, the standard ammonium displacement method for CEC determination does not take into account the fabric changes that occur in bentonites under exposure to high salt concentration solutions. A series of laboratory tests was conducted to assess the relevance of such a critical issue, by varying the concentration of the extracted potassium chloride (KCl) solution with respect to that of the standard test. The obtained results show that the release of the adsorbed ammonium cations depends on the bentonite fabric, which is controlled by the potassium chloride concentration. As a consequence, the ammonium displacement method may provide an unrepresentative estimate of the CEC of bentonites. The methylene blue titration method, despite its apparently more limited accuracy, instead, seems to provide a more reliable estimation of the CEC, as the bentonite fabric is maintained dispersed during the test.

Synthesis and characterization of kaolinite coated with copper oxide and its effect on the removal of aqueous Lead(II) ions

The removal of Lead (Pb2+) ions from waste water in the aquatic environment by copper oxide–kaolinite composite forms an important step involved in the reduction of Lead ions in the environment. The study investigated the synthesis, characterization, and application of copper oxide–kaolinite composite in the removal of Lead ions from aqueous systems. The synthesis of the composite involved a trimetric process to produce the copper oxide (CuO)–kaolinite composite. The characterization involved the determination of cation exchange capacity, specific surface area, and spectral analysis by sodium saturation method, nitrogen gas adsorption techniques, and scanning electron spectroscopy, respectively. The determination of parameters affecting the reaction mechanism and reaction kinetics involved the use of batch mode techniques. The findings indicated a reaction mechanism that was less than one proton coefficient, higher mass transfer rates when compared with uncoated kaolinite. Here, the intraparticle diffusion was higher than the value for the uncoated kaolinite. The reactions based on Pb2+ initial concentration indicated that the coated kaolinite gradually became saturated as the concentration was increased. The reactions based on solid concentration (Cp) demonstrated a complex change in the capacity of adsorption over different Pb2+ concentrations (10–40 mgL−1) and solid concentrations (2–10 gL−1). Here, the reduction in specific surface area, particle size increase, mineral aggregation, and concentration gradient effect controlled the complex changes in adsorption. In conclusion, the copper oxide–kaolinite composite significantly enhanced the adsorption of Pb2+ ions.

Late-Holocene palaeoenvironmental changes at Lake Esmeralda (Vega Island, Antarctic Peninsula) based on a multi-proxy analysis of laminated lake sediment

We have studied laminated sediments from Lake Esmeralda, Vega Island, in order to reconstruct its history. We describe both inorganic and organic components of the sediment using a combination of the following analytical methods: x-ray fluorescence (XRF), x-ray diffraction (XRD), magnetic susceptibility measurement, chemical analysis for determination of cation exchange capacity, grain size determination, geochemical analyses (total inorganic carbon (TIC), total organic carbon (TOC), total sulphur (TS)), spectrophotometry, high-pressure liquid chromatography, and diatom assemblage and faunal remains characterization. The geochronology of the core was based on modelling optically stimulated luminescence ages and supported by laminae counting. The dating results imply a maximum age of ~400 years for the 177-cm long core and a period covered of ~200 years, suggesting (quasi-)annual laminae formation. Such a young age contradicts previous findings based on radiocarbon dating. Geomorphological evidence indicates that river capture isolated the lake catchment from upslope sediment delivery, effectively terminating accumulation ~230 years ago. Conversely, our short-term palaeoenvironmental record yields a subdecadal temporal resolution, which is unparalleled in comparison with other Antarctic palaeolimnological studies. Our interpretations of the geochemical and mineralogical proxy data give us insight into the past lake catchment and waterbody evolution, and lead us to recognize periods of enhanced weathering, bottom anoxia and to distinguish major lake level changes.