Sodic Bentonite Research Articles

Removal of ciprofloxacin from an aqueous medium by adsorption on natural and hydrolyzed bentonites

Two bentonites (sodic bentonite, BSN, and calcic bentonite, BCN) were treated with nitric acid to improve the adsorption capacities using ciprofloxacin (CIP) as an adsorbate. The results demonstrated that nitric acid treatment enhances the specific area and increases the pore volume of both bentonites. The mechanism of adsorption of CIP was investigated using a kinetic model, isotherms, and pH influence. The adsorption capacity for BSN increased from 294.1 mg.g−1 to 416.6 mg.g−1 after acid treatment, while the increase in the adsorption capacity of BCN was minor. The increase in CIP removal may be due to an increase in the specific area and the presence of acidic surface functional groups. The adsorption mechanism of CIP on all adsorbents was governed by external diffusion, internal diffusion, and adsorption to reach equilibrium. The adjustment of strong adsorbents to the BET model indicated multilayer adsorption. The best adsorbent is sodic bentonite with nitric acid treatment. The study of the pH effect showed that the mechanism of CIP adsorption is hydrogen bonds and electrostatic interaction. Therefore, the acid treatment was found promising to improve the adsorbent characteristic of clays for removing CIP from water.

Malachite green dye and its removal from aqueous solution by clay-chitosane modified

The main purpose of this work is to study the adsorption of malachite green, a cationic dye, in aqueous solution using chitosan-modified natural clay. This material was synthesized via the intercalation of chitosan into sodic bentonite, and then characterized using techniques such as Fourier transform infrared (FT-IR) spectroscopy, X-ray Diffraction (XRD) analysis, and X-ray fluorescence analysis. The effects of some process parameters such as contact time, initial dye concentration and pH of solution on the sorption of malachite green were also thoroughly investigated. In addition, it was found that the pseudo-second-order kinetic model provided the best fit to the experimental data for the adsorption of malachite green by the modified clay. Moreover, the experimental results indicated that the adsorption equilibrium data fitted quite well with the Langmuir isotherm, and the adsorption capacity was found equal to 96%.

Swelling deformation of Na-bentonite in solutions containing different cations

Investigation of the effect of salt solution on the swelling properties of compacted bentonite is of great importance for evaluation of the properties of behavior of engineering barrier in deep geological repository for disposal of high-level radioactive waste. In the present work, a multitude of swelling deformation tests were performed on sodic bentonite using NaCl, KCl, and CaCl2 solutions. It is revealed from the results that the swelling strains of the tested samples in variety of saline solutions follow the order of NaCl > KCl > CaCl2 at the concentration of 0.1 mol/L (M), whereas the order was NaCl > CaCl2 > KCl at 1.0 M concentration. The fractal em–pe relations for swelling deformation of Na-bentonite in different solutions were estimated, where em is the smectite void ratio at saturation, pe is effective stress incorporating osmotic suction depicting the effects of ionic concentration on swelling. In addition, the effect of the cation exchange is described using the smectite swelling coefficient K. The estimation values fit well with the experimental data. In NaCl solutions, the coefficient K is basically unchanged due to the weak cation exchange reaction. On the contrary, Ca2+ can much easily replace Na+ even at low concentrations and the CaCl2 solution exhibits the highest values of osmotic suction, the swelling coefficient and swelling deformation of the samples in the 0.1 M CaCl2 solution are smaller than that of samples in other 0.1 M solutions. However, at high concentrations, Na+ can be fully replaced by both Ca2+ and K+. The hydration energy of K+ is comparatively lower due to which the swelling coefficient of the samples in the 1.0 M KCl solution significantly decreased thereby resulting in least swelling deformation.

Comparative study on thorium (İv) sorption onto sodic bentonite and magnetic bentonite

In this paper, the liquid-solid extraction of Thorium (IV) is made by Sodic bentonite and Magnetic bentonite. Magnetic adsorbent can be quickly separated from a medium by a simple magnetic process, in view of these properties; some parameters were studied to assess the performance of maghemite nanocomposite clay for the removal of Thorium ions. The operating variables studied are initial La(III) concentration, pH, ionic strength, temperature and contact time. The time needed for magnetic bentonite to adsorb the maximum of Th (IV) is 45 minutes and 60 minutes for sodic bentonite. For magnetic bentonite, optimal extraction yield was achieved in a initial pH equal at 6.2 and for sodic bentonite, the variation of initial pH has no influence on the extraction yield. The sorption capacities of sodic bentonite and magnetic bentonite are 41.24 and 31.34 mg.g -1 respectively. Adsorption equilibrium data were calculated for Langmuir and Freundlich isotherms. It was found that the sorption of Th (IV) on sodic and magnetic bentonite was better suited to the Langmuir adsorption model. Thermodynamics data leads to endothermic and spontaneous process for magnetic bentonite and exothermal for sodic bentonite. The quantitative elution study of Thorium can be realized with acetic acid for sodic bentonite and sulfuric acid for magnetic bentonite.

Adsorption of Bezathren dyes onto sodic bentonite from aqueous solutions

Abstract The aim of the present work was to investigate the adsorption of synthetic textile dyes, such as Bezathren-Blue, Bezathren-Green and Bezathren-Red onto sodium bentonite (Bt-Na+). Adsorption experiments were performed under batch process, to assess the performance of Bt-Na+ for the removal of Bezathren-dyes, using initial dyes concentrations, pH of solution, contact time and temperature as variables. According to results, the uptake of Bezathren-dyes by Bt-Na+ was rapid and the maximum sorption was observed at lowest pH. The maximum uptake capacities (qm) for Bezathren-Blue, Bezathren-Green and Bezathren-Red were 35.08 mg/g, 32.88 and 48.52 mg/g respectively. Different types of adsorption isotherms and kinetic models were used to describe the Bezathren-dyes adsorption behavior. The experimental results fitted Freundlich model and the pseudo-second order kinetic models well. The results suggested that Bt-Na+ is suitable as a sorbent material for recovery and adsorption of Bezathren dyes from aqueous solutions.

Evaluation of Filtration Properties of Clay Suspensions under Different Thermic Conditions

In clay suspensions designed for drilling, the sodic bentonite clay is commonly chosen for its better hydration capacity compared to the other kinds. The sodium bentonite clay is essentially composed by montmorilonite, a clay mineral that belongs to the group of smectites. This work aims to evaluate the behavior of clay suspensions under different thermic conditions. For that, were studied suspensions prepared with sodium bentonite clay, in concentrations varying between 2.5% and 6.4%, under different temperatures and also types of aging. The suspensions were tested based on a matrix of experimental planning. The filtration properties were determined by the filtrate volume, the relation of filtrate volume with time of filtration, the mudcake thickness and the permeability of the mudcake. The results exhibited that the high temperature promotes a gelification state of the suspensions, being therefore responsible for the high values of the filtration properties.

Mineralogical and geochemical study of bentonite deposits of Garhi Chandan area, District Nowshera, Khyber Pakhtunkhwa, Pakistan

The Pliocene-Pleistocene Ghari Chandan Formation consists of lacustrine-fluvio-deltaic deposits exposed in the Attock-Cherat Range. Three beds of bentonite deposits occur in the upper part of the formation. An average thickness of each layer ranges from 0.4 to 1 m with a total strike length of ~5 Km. Montmorillonite and saponite clay minerals with admixtures of quartz, feldspar, muscovite, biotite, and hornblende were identified in these samples. Compositionally these beds are similar and comprised of dioctahedral smectite. The differential thermal analyses of bentonite reveals high thermal stability of the deposits. Detailed mineralogical and geochemical investigations suggest that the Garhi Chandan deposit is a mixture of calcic and sodic bentonite derived from andesitic and trachyandesitic source rock. Heavy metal concentration reduces the overall adsorbing capacity of the deposit.

Removal of Cadmium(II) and Lead(II) ions from aqueous phase on sodic bentonite

before and after chemical modification and thermal activation was characterized by different techniques including X-ray diffraction, thermal analysis, Fourier transform infrared, surface area, helium pycnometry, cation exchange capacity and scanning electron microscopy. Pseudo-first order, pseudo-second order and intra-particle diffusion models were used to analyze the kinetic curves. Equilibrium data were analyzed using Langmuir and Freundlich models. The thermodynamic study indicated that lead adsorption process is endothermic and interactions between clays and solutions of lead occurred spontaneously, while cadmium adsorption revealed an exothermic and spontaneous nature. The maximum removal efficiencies were 97.62% for Cd(II) using

Compostos poliméricos como aditivos de argilas bentoníticas

Este trabalho tem por objetivo avaliar o efeito da utilização de compostos poliméricos na aditivação de bentonitas de Boa Vista, PB, consideradas de qualidade inferior, para utilização em fluidos de perfuração à base de água, visando a melhoria das suas propriedades reológicas e de filtração. Foram estudadas uma amostra de argila bentonítica e três amostras de aditivos poliméricos, sendo uma de poliacrilamida parcialmente hidrolisada e duas de carboximetilcelulose de diferentes graus de viscosidade. O dimensionamento das composições do composto polimérico foi obtido por meio da metodologia de delineamento de misturas, sendo definidas dez composições. O composto polimérico foi misturado à argila seca, em diferentes concentrações e, em seguida, preparados os fluidos de perfuração e determinados as viscosidades aparente e plástica, o limite de escoamento e o volume de filtrado segundo normas da Petrobrás. Os resultados mostram que a aditivação da argila bentonítica com o composto polimérico melhora as suas propriedades, adequando-a às especificações da Petrobrás para utilização em fluidos de perfuração à base de água.

Desenvolvimento de compósitos bentonita/polímeros para aplicação em fluidos de perfuração

A aditivação polimérica dos fluidos usados na perfuração de poços de petróleo é prática comum e dentre os aditivos mais usados, destacam-se o carboximetilcelulose (CMC) e a poliacrilamida parcialmente hidrolisada (PHPA), que dependendo das suas características, desempenham diferentes funções e são adicionados individualmente. Este trabalho objetiva o estudo de composições binárias de polímeros celulósicos e não-celulósicos visando o desenvolvimento de compósitos bentonita/polímeros para uso em fluidos à base de água. Foi estudada uma amostra de argila bentonítica sódica da Paraíba e três amostras de polímeros (CMC de baixa e alta viscosidade e PHPA). O dimensionamento das misturas de polímeros foi elaborado de forma a explorar composições básicas (100%-0%; 50%-50% e 0%-100%) como passo inicial. Os compostos poliméricos em três diferentes concentrações foram misturados à argila seca e, em seguida, preparados os fluidos de perfuração. Após repouso de 24 h, foram determinadas as viscosidades aparente e plástica e o volume de filtrado de acordo com as normas da Petrobras. Os resultados evidenciaram que a mistura de polímeros celulósicos com os não-celulósicos se mostrou mais eficiente na melhoria das propriedades reológicas e de filtração dos fluidos de perfuração à base de água. Desta forma, torna-se viável a combinação de matérias primas de características diferentes para a obtenção de compostos poliméricos a serem adicionados a argilas bentoníticas para o desenvolvimento do compósito bentonita/polímero para uso na perfuração de poços de petróleo.

Cadmium removal from aqueous solutions by hydroxy-8 quinoleine intercalated bentonite

An Algerian bentonite was purified and modified by intercalation of 8-hydroxyquinolinium ion. These materials were characterized by X-ray diffraction, infrared spectroscopy, and thermal analysis. Comparative batch experiments were performed using bentonite–oxine complex (B–oxine) and sodic bentonite (B-Na) for removing cadmium from aqueous solutions. Kinetics study results of cadmium removal with B-Na and B–oxine fit a pseudo-second-order model. The adsorption isotherm data follow the Langmuir equation in which parameters were calculated. B–oxine has a better cadmium removal capacity (61.35 mg/g) than B-Na (29.41 mg/g). Calculated thermodynamic parameters using the van't Hoff equation showed that the removal process is endothermic with B–oxine and exothermic with B-Na. A mechanism of ion exchange followed by complexation–precipitation is suggested for cadmium removal with B–oxine.

Comportamento reológico de dispersões de argilas bentoníticas: efeitos do tipo de ferramenta, velocidade e tempo de agitação

Este trabalho teve como objetivo estudar a influência do tipo de ferramenta, da velocidade e do tempo de agitação nas propriedades reológicas de dispersões de quatro amostras de argilas bentoníticas sódicas industrializadas no Estado da Paraíba, Brasil. Foi realizado um planejamento fatorial do tipo 2³ para avaliar os fatores de entrada (tipo de ferramenta, velocidade e tempo de agitação) sobre as viscosidades aparente e plástica e o volume de filtrado. As dispersões foram preparadas na concentração de 4,86% em massa de argila (24,3 g de argila em 500 mL de água deionizada) utilizando ferramentas do tipo palheta corrugada e em forma de borboleta, duas velocidades (10.000 rpm e 17.000 rpm) e dois tempos de agitação (10 e 20 min). As viscosidades aparente e plástica foram determinadas em viscosímetro Fann 35A, e o volume de filtrado, em filtro prensa Fann. Através da regressão dos dados experimentais, verificou-se que as variáveis de entrada não apresentam influências estatisticamente significativas nas propriedades reológicas das dispersões estudadas, bem como, que dentre as quatro argilas estudadas apenas uma apresenta comportamento reológico de acordo com as normas vigentes para uso como agente tixotrópico para fluidos de perfuração à base de água doce.

Centrifugal filtration of particulate systems

Analysis of centrifugal filtration is complicated by its formulation in radial-cylindrical coordinates and the inclusion of a significantly varying centrifugal force across the filter cake. The process often commences, however, with a filter cake of zero thickness so there will be a period of time during which one-dimensional, constant centrifugal force analysis of the process will be exact. It is important to understand the nature of flow during this time because it accurately represents the early stages of, and therefore a base from which to analyse, the more complicated system. In addition, it may emerge that, for some materials, the simplified analysis may be sufficient for practical purposes. For materials where the permeability and the effective stress are well-defined functions of the water content, the early stages of centrifugal filtration are described by a one-dimensional non-linear Fokker–Planck equation cast in a material coordinate based on the distribution of the solid phase. The analysis takes full account of the non-steady nature of flow and the non-linearity of the equations that describe it. It does not require common inaccurate assumptions that the flux of solid can be neglected nor that quasi-steady flow takes place. The analysis predicts, and experiments on a sodic bentonite confirm, that substantially non-uniform solid and liquid profiles are observed during ‘early stages’ of the process, which evolve in a manner which is effectively identical to those observed during constant pressure filtration. The generality of the approach is illustrated with material data for Red mud. Limits to the times during which flow might be regarded as one-dimensional rather than cylindrically axi-symmetric, and during which some centrifugal effects might be neglected, are discussed and shown to be readily calculated.

Plant Responses to Gypsum Amendment of Sodic Bentonite Mine Spoil

Abandoned bentonite mine spoils are extremely difficult to revegetate because of their high clay content, salinity, sodicity, low permeability, and the semiarid climate of the area where bentonite mining occurs. Recent research has led to the development of technology utilizing sawmill wastes (chips, bark, and sawdust) to enable the successful revegetation of these lands. The use of wood residue amendments increased water infiltration, leaching of soluble salts, and vegetation establishment; however, sodicity continued to be a problem and threatened to destroy the established vegetation. Surface application of gypsum was evaluated to determine its effectiveness in ameliorating the spoil sodicity and its effect on plant growth. In a 3-year field study, surficial gypsum amendment resulted in significant increases in perennial grass biomass (150%) and canopy cover (140%). These changes were not evident until the second or third year after gypsum amendment. Annual forb biomass did not respond to gypsum amendment; however, canopy cover did exhibit a significant increase in the second year at lower wood residue amendment rates. This research demonstrates that surface applied gypsum can be effective in ameliorating bentonite spoil sodicity when applied to established plant communities.

Short‐Term Effects of Surface‐Applied Gypsum on Revegetated Sodic Bentonite Spoils

Short‐Term Effects of Surface‐Applied Gypsum on Revegetated Sodic Bentonite Spoils

Short‐Term Effects of Surface‐Applied Gypsum on Revegetated Sodic Bentonite Spoils

AbstractThe high clay content and saline‐sodic characteristics of bentonite mine spoils result in an environment that is not conductive to sustainable plant growth. Use of wood residue amendments have enabled revegetation of these materials; however, sodic conditions persist or worsen, threatening the long‐term sustainability of these revegetated lands. Gypsum, 56 Mg/ha, was surface applied to these revegetated ecosystems to evaluate its effectiveness in ameliorating the spoil sodicity under a natural precipitation environment. The gypsum treatment significantly reduced the exchangeable Na and the exchangeable Na percentage of the 60‐cm spoil profile 3 yr after treatment. The gypsum amendment also significantly increased the spoil‐water storage in the 60‐cm spoil profile. Gypsum treatment resulted in a significant increase in the spoil electrical conductivity; however, this increase did not detrimentally affect the vegetation. Surface‐applied gypsum amendment effectively ameliorated the revegetated bentonite mine spoil sodicity under natural rainfall conditions in a semiarid environment.

Steam rapidly reduces the swelling capacity of bentonite

Sodic bentonite is widely used for industrial and scientific purposes, especially as a sealing agent1, because of its great ability to swell in water2,3. It has been proposed for use in high-level nuclear waste repositories as an impermeable barrier surrounding the waste package, or to fill tunnels, shafts and rooms. In some repositories, such as those planned in basalt, bentonite would be expected to be subjected to temperatures possibly up to 300 °C (refs 4, 5). As the waste would be approximately 600–900 m below the water table in fractured rock, the repository is expected to fill first with steam and then with liquid water4,6. Reaction of bentonite with liquid water produces a minimal loss of swelling capacity, but I show here that reaction with water vapour at 150–250 °C results in rapid irreversible loss of most of the swelling capacity. This causes very large increases in permeability of sand–bentonite mixtures7, thereby reducing the ability of a bentonite barrier to retard the flow of groundwater in proposed high-level nuclear waste repositories.