Methylene Blue Adsorption on Natural and Modified Clays

Toxic methylene blue dye is removed from water by accumulating it on the surface of clay minerals. Clay adsorbents are obtained from kaolinite, montmorillonite, and their acid activated forms. The adsorption experiments are carried out in a batch process in environments of different pH, initial dye concentration, amount of clay, interaction time, and temperature. Adsorption of dye is best described by second order kinetics. In the temperature range of 303 to 333 K, the Langmuir monolayer capacity for three kaolinite species increased from 45.5 to 56.5 mg g^?1, 45.9 to 57.8 mg g^?1, 46.3 to 58.8 mg g^?1, and for three montmorillonites species from 163.9 to 181.8 mg g^?1, 166.7 to 188.8 mg g^?1, and 172.4 to 192.3 mg g^?1. The interaction is an endothermic process driven by entropy increase and spontaneous adsorptive accumulation is ensured by favorable Gibbs energy decrease. It is found that acid activation enhances the adsorption capacity of kaolinite and montmorillonite.     

Uptake of Ni(II) Ions from Aqueous Solution by Kaolinite and Montmorillonite: Influence of Acid Activation of the Clays

Abstract

Kaolinite and montmorillonite were treated with 0.25 M H₂SO₄ and the acid activated clays along with the parent clays were tested for their uptake capacity for Ni(II) ions from aqueous solution. The batch adsorption experiments were conducted under a set of variables (concentration of Ni(II) ion, amount of clay, pH, time and temperature of interaction). Increasing pH favored Ni(II) uptake till the ions were precipitated as the insoluble hydroxides at pH > 8.0. The uptake was rapid up to 40 min and equilibrium was obtained within 180 min. The kinetics of the process was evaluated by subjecting the results to a number of models like the pseudo-first order, second order, Elovich equation, liquid film diffusion, and intra-particle diffusion and it was found that the data more closely resembled a second order process. The experimental data conformed to both Langmuir and Freundlich isotherms showing that the interactions were mostly chemical in nature. The clays had reasonable monolayer adsorption capacity of 10.4, 11.9, 28.4, and 29.5 mg g^?1 for kaolinite, acid activated kaolinite, montmorillonite, and acid-activated montmorillonite respectively. Montmorillonite had much better adsorption capacity than kaolinite and the acid activation boosted the adsorption capacity of both kaolinite and montmorillonite. The interactions were exothermic in nature, accompanied by decrease in both entropy and Gibbs energy. The results have established good potentiality for kaolinite, montmorillonite and their acid-activated forms to take up and separate Ni(II) from aqueous medium through adsorption-mediated immobilization.     

Adsorption and biodegradation of carbaryl on montmorillonite, kaolinite and goethite

Bioavailability of pesticides adsorbed on mineral surfaces is an important determinant of their environmental fate. Carbaryl (1-naphthyl-N-methylcarbamate) was used as a model compound to illustrate the impact of adsorption characteristics and microbial activity on the bioavailability of organic compound adsorbed on clay minerals and goethite. Batch experiments were applied to determine the sorption isotherms and biodegradation kinetics. Metabolic activity of Pseudomonas putida in the absence and presence of montmorillonite, kaolinite or goethite was monitored by microcalorimetry. Adsorption mechanisms of carbaryl were studied by Fourier Transform Infrared Spectroscopy (FTIR). Montmorillonite presented a higher adsorption capacity for carbaryl than goethite and kaolinite. Degradation of adsorbed carbaryl by P. putida followed the sequence montmorillonite > kaolinite > goethite, which is in accordance with the binding strength of carbaryl on the minerals. The presence of montmorillonite enhanced the activity of P. putida and ultimately stimulated the bioavailability of carbaryl. Goethite displayed an inhibitory effect on bacterial activity and reduced carbaryl degradation. The biodegradation of mineral-adsorbed carbaryl was mainly controlled by the activity of the degrading microorganisms.     

Calcined tetrabutylammonium kaolinite and montmorillonite and adsorption of Fe(II), Co(II) and Ni(II) from solution

Kaolinite and montmorillonite were modified with tetrabutylammonium (TBA) bromide, followed by calcination. The structural changes were monitored with XRD, FTIR, surface area and cation exchange capacity measurements. The modified clay minerals were used for adsorption of Fe(III), Co(II) and Ni(II) ions from aqueous solution under different conditions of pH, time and temperature. The uptake of the metal ions took place by a second order kinetics. The modified montmorillonite had a higher adsorption capacity than the corresponding kaolinite. The Langmuir monolayer capacities for the modified kaolinite and montmorillonite were Fe(III): 9.3 mg g^− 1 and 22.6 mg g^− 1; Co(II): 9.0 mg g^− 1 and 22.3 mg g^− 1; and Ni(II): 8.4 mg g^− 1 and 19.7 mg g^− 1. The modified kaolinite interacted with Co(II) in an endothermic manner, but all the other interactions were exothermic. The decrease of the Gibbs energy in all the cases indicated spontaneous adsorption.     

Kaolinite, montmorillonite, and their modified derivatives as adsorbents for removal of Cu(II) from aqueous solution

Adsorption of metals by clay minerals is a complex process controlled by a number of environmental variables. The present work investigates the removal of Cu(II) ions from an aqueous solution by kaolinite, montmorillonite, and their poly(oxo zirconium) and tetrabutylammonium derivatives. The entry of ZrO and TBA into the layers of both kaolinite and montmorillonite was confirmed by XRD measurement. The specific surface areas of kaolinite, ZrO-kaolinite, TBA-kaolinite, montmorillonite, ZrO-montmorillonite, TBA-montmorillonite were 3.8, 13.4, 14.0, 19.8, 35.8 and 42.2 m²/g, respectively. The cation exchange capacity (CEC) was measured as 11.3, 10.2, 3.9, 153.0, 73.2 and 47.6 meq/100 g for kaolinite, ZrO-kaolinite, TBA-kaolinite, montmorillonite, ZrO-montmorillonite, TBA-montmorillonite, respectively. Adsorption increased with pH till Cu(II) ions became insoluble in alkaline medium. The kinetics of the interactions suggests that the interactions could be best represented by a mechanism based on second order kinetics (k₂ = 7.7 × 10⁻² to 15.4 × 10⁻² g mg⁻¹ min⁻¹). The adsorption followed Langmuir isotherm model with monolayer adsorption capacity of 3.0–28.8 mg g⁻¹. The process was endothermic with ΔH in the range 29.2–50.7 kJ mol⁻¹ accompanied by increase in entropy and decrease in Gibbs energy. The results have shown that kaolinite, montmorillonite and their poly(oxo zirconium) and tetrabutyl-ammonium derivatives could be used as adsorbents for separation of Cu(II) from aqueous solution.     

Characterization and use of acid‐activated montmorillonite‐illite type of clay for lead(II) removal

The natural local deposits of montmorillonite‐illite type of clay (MIC) were susceptible for acid activation. Raw clay was taken for experimentation, disintegrated on acid activation with sulfuric acid, which showed a particle size distribution. The montmorillonite and illite phases in the raw clay disappeared on acid activation and the activated clay, MIC(AA), showed with sodium‐aluminum‐silicate and beidellite phases apart from quartz (low) phase. The raw and acid‐activated clays were characterized using X‐ray powder diffractometry, X‐ray fluorescence, Fourier transform infrared spectrometry, and energy dispersive X‐ray, and their adsorption capacities were compared. When tested for adsorption of Pb(II) in aqueous solutions, the acid‐activated clay showed about 50% increased adsorption than raw clay. Sips adsorption isotherm and pseudo‐second‐order kinetic models were found to be best for the batch adsorption data. Kinetic studies showed the existence of film diffusion and intraparticle diffusion. A two‐stage batch adsorber was designed for the removal of Pb(II) from aqueous solutions. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

The adsorption behavior of Cu(II), Pb(II), and Co(II) of ethylene vinyl acetate‐clinoptilolite nanocomposites

In this study, ethylene vinyl acetate (EVA) was mixed with clinoptilolite (C), a natural zeolite, to prepare EVA‐C nanocomposites. The films were characterized by SEM‐EDS, XRD, and FT‐IR, and heavy metal removal was studied using the batch technique. The effects of the initial pH value and concentration of solutions, contact time, and filler dosage on the adsorption capacity of the composites were investigated. To study the influence of pretreatment on the filler, clinoptilolite was activated using KCl, NaCl, and HCl. Adsorption results show that equilibrium was reached after 24 h, and that sorption reached its maximum at pH values between 5 and 7. The selectivity trend was observed to be Pb > Cu > Co, which was consistent for both single and mixed metal‐ion solutions. Pretreatment significantly increased adsorption capacity of the composite, but was dependent on the conditioning reagent. Nanocomposites filled with HCl‐activated particles demonstrated a high adsorption capacity of between 70 and 80% for all three metals, while KCl‐activated particles were the least efficient with a maximum adsorption capacity of 69% for Pb(II), 54% for Cu(II) and 48% for Co(II). The adsorption data were then fitted to both Langmuir and Freundlich isotherms over the entire concentration range, and the Langmuir isotherm showed a better fit of the experimental sorption data than the Freundlich isotherm. The results obtained show that this simple methodology which can be up‐scaled has great potential for the preparation of a wide variety of similar particle‐filled adsorbent nanocomposites in other environmental remediation applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Optimization of kinetic data for two‐stage batch adsorption of Pb(II) ions onto tripolyphosphate‐modified kaolinite clay

BACKGROUND: Most adsorption studies consider only the adsorption of pollutants onto low cost adsorbents without considering how equilibrium and kinetic data can be optimized for the proper design of adsorption systems. This study considers the optimization of kinetic data obtained for the removal of Pb(II) from aqueous solution by a tripolyphosphate modified kaolinite clay adsorbent. RESULTS: Modification of kaolinite clay with pentasodium tripolyphosphate increases its cation adsorption capacity (CEC) and specific surface area (SSA) from 7.81 to 78.9 meq (100 g)^?1 and 10.56 to 13.2 m² g^?1 respectively. X‐ray diffraction patterns for both unmodified and tripolyphosphate‐modified kaolinite clay suggest the modification is effective on the surface of the clay mineral. Kinetic data from the batch adsorption of Pb(II) onto the tripolyphosphate‐modified kaolinite clay adsorbent were optimized to a two‐stage batch adsorption of Pb(II) using the pseudo‐second‐order kinetic model. Mathematical model equations were developed to predict the minimum operating time for the adsorption of Pb(II). Results obtained suggest that increasing temperature and decreasing percentage Pb(II) removal by the adsorbent enhanced operating time of the adsorption process. The use of two‐stage batch adsorption reduces contact time to 6.7 min from 300 min in the single‐stage batch adsorption process for the adsorption of 2.5 m³ of 500 mg L^?1 Pb(II) under the same operating conditions. CONCLUSION: Results show the potential of a tripolyphosphate‐modified kaolinite clay for the adsorption of Pb(II) from aqueous solution and the improved efficiency of a two‐stage batch adsorption process for the adsorption of Pb(II) even at increased temperature. Copyright © 2009 Society of Chemical Industry     

Adsorption Behavior of Iminodiacetic Acid Type of Chelating Gel Prepared from Waste Paper

Abstract

Adsorption gel was prepared from waste recycled paper by immobilizing iminodiacetic acid (IDA) functional group by chemical modification. The gel exhibited good adsorption behavior for a number of metal ions viz. Cu(II), Pb(II), Fe(III), Ni(II), Cd(II), and Co(II) at acidic pH. The order of selectivity was found to be as follows: Cu(II)>Pb(II)>Fe(III)>Ni(II)～Cd(II)～Co(II). From the adsorption isotherms, the maximum adsorption capacity of the gel for both Cu(II) and Pb(II) was found to be 0.47 mol/kg whereas that for Cd(II) was 0.24 mol/kg. A continuous flow experiment for Cd(II) showed that the gel can be useful for pre‐concentration and complete removal of Cd(II) from aqueous solution.     

Arsenic adsorption mechanism on clay minerals and its dependence on temperature

In the present study, the As(V) removal efficiency of different clay minerals was investigated as a function of solution pH, time, As(V) concentration, and temperature. Arsenic mobility was also investigated by determining the As(V) released from the loaded samples by leaching with various aqueous solutions. The kinetics of adsorption was observed to be fast and reached equilibrium within 3 h. As(V) adsorption on studied clays was pH dependent and maximum adsorption was achieved at pH 5.0. The maximum adsorption capacity was calculated by fitting the Langmuir equation to the adsorption isotherms and found to be 0.86, 0.64, and 0.52 mg As(V)/g of kaolinite, montmorillonite, and illite, respectively. The negative effect of temperature on As(V) adsorption showed the interactions to be exothermic. Based on the results, it was found that among the studied clay minerals, kaolinite was the best As(V) adsorbent and montmorillonite had strong retention capacity. The electrokinetic behavior of kaolinite and montmorillonite was modified in the presence of As(V), indicating that adsorption involves inner sphere surface complexation and strong specific ion adsorption.     

不同粘土矿物与聚羧酸减水剂相互作用机理研究

通过X射线衍射(XRD)、红外光谱(IR)、有机碳吸附(TOC)、饱和吸水率以及净浆流动性等试验方法,研究了不同粘土矿物与聚羧酸减水剂的相互作用机理.结果表明:聚羧酸减水剂的侧链可进入粘土矿物蒙脱石的层间,发生插层反应,即层间吸附,而其侧链结构不进入伊利石、高岭土、海泡石等粘土矿物的层间,仅发生表面吸附,且吸附量大小为蒙脱石>高岭土>海泡石>伊利石;饱和吸水率试验显示,粘土矿物的饱和吸水率大小为蒙脱石>高岭土>海泡石>伊利石;流动度试验表明,粘土矿物对水泥-减水剂体系净浆流动度均有不同程度的影响,且蒙脱石影响程度最大.由此可知,粘土矿物对自由水和聚羧酸减水剂的吸附是造成流动度损失的主要原因.     

页岩中黏土矿物吸附特性分子模拟

页岩的吸附解吸特性对页岩气资源开发具有重要意义。为深入了解页岩中黏土矿物微观吸附机理, 利用Material Studio 分子模拟软件构建了伊利石、蒙脱石和高岭石3种黏土矿物分子模型, 采用巨正则Monte Carlo(GCMC)方法对3种模型的等温吸附量和吸附热进行了模拟计算。研究表明, 在相同温度和压力条件下3种黏土矿物对CH₄分子的吸附量大小顺序是伊利石>蒙脱石>高岭石;随压力增大3种黏土矿物对CH₄分子的吸附量均有所增加, 而且伊利石和蒙脱石对CH₄分子的吸附量对压力变化更为敏感;3种黏土矿物的等量吸附热均小于42 kJ·mol^-1, 对CH₄的吸附为物理吸附;随着温度的升高, CH₄分子的吸附热和吸附量均减小。     

Delamination of montmorillonite in serum—A new approach to obtaining clay-based biofunctional hybrid materials

Adsorption of proteins on the surface of smectites (e.g. montmorillonite—MMT) is a well established method for selective removal of some proteins from mucosal fluids. In this paper we report on an investigation of structural aspects of the adsorption of proteins occurring in normal human serum (NHS) on montmorillonites. Extensive structural studies, involving X-ray scattering (WAXS and SAXS) and electron microscopy (TEM) techniques, revealed that adsorption of proteins from normal human serum (NHS) causes montmorillonite to exfoliate, in a similar manner as in exfoliated polymer-layered silicate nanocomposites. Although the mechanism of exfoliation was not finally explained, the results indicate that it relies on synergistic adsorption of proteins on the surface of the clay. Apart from exfoliated, SAXS and TEM revealed occurrence of intercalated particles with extremely large distance between subsequent platelets (approx. 10–14 nm). As confirmed by tests of bacterial growth kinetics (with six Salmonella strains), after treatment with MMT, the serum loses its bactericidal properties due to removal of lysozyme. On the other hand, preliminary results indicate that adsorption of lysozyme on the clay surface imparts antibacterial properties to the obtained nanohybrids. The results reported in the paper clearly indicate that adsorption of proteins from natural systems can be considered as a facile route of obtaining exfoliated montmorillonite–protein systems.     

Interaction of metal ions with clays: I. A case study with Pb(II)

Pb(II) adsorption was studied under different conditions (pH, time, metal ion concentration, clay amount, temperature) on kaolinite, montmorillonite, and their poly(hydroxo)zirconium (ZrO–kaolinite, ZrO–montmorillonite) and tetrabutylammonium (TBA–kaolinite, TBA–montmorillonite) derivatives. All samples were calcined (ZrO-derivatives at 773 K, TBA-derivatives at 973 K) before using as adsorbents. The data were interpreted assuming first- and second-order kinetics. The rate constants including the pore diffusion rate constant are reported. The adsorption data could be fitted with Freundlich and Langmuir isotherms, and the coefficients indicated favorable adsorption of Pb(II) on the clays. Determination of the thermodynamic parameters, ΔH, ΔS, and ΔG showed the adsorption to be exothermic accompanied by decrease in entropy and Gibbs energy.     

活性炭吸附法处理对苯二甲酸废水研究

选择了4种不同类型、不同粒度的活性炭作为吸附剂,对苯二甲酸废水的吸附行为进行了研究。对苯二甲酸浓度采用紫外分光光度法测定。实验结果表明粒度为20-40目的A活性炭的吸附性能最好。活性炭吸附量随溶液pH值升高而降低,pH值为6时的吸附量约为DH为14时的4倍。搅拌可以缩短活性炭达到平衡吸附的时间,但对平衡吸附量影响很小。     

Adsorption of sulfur dioxide onto activated carbons prepared from oil‐palm shells impregnated with potassium hydroxide

Adsorption of sulfur dioxide (SO₂), a gaseous pollutant, onto activated carbons prepared from oil‐palm shells pre‐treated with potassium hydroxide (KOH) impregnation was studied. Experimental results showed that SO₂ concentration and adsorption temperature affected significantly the amount of SO₂ adsorbed and the equilibrium time. However, sample particle sizes influenced the equilibrium time (due to effect of diffusion rate) only. Desorption at the same temperature of adsorption and a higher temperature of 200 °C confirmed the presence of chemisorption due to pre‐impregnation. Impregnation with different activation agents was found to have limited effect on the inorganic components of the sample. Compared with the activated carbon pre‐treated with 30% phosphoric acid (H₃PO₄) that had larger BET and micropore surface areas, the sample impregnated with 10% KOH had a higher adsorptive capacity for SO₂, which was closely related to the surface organic functional groups of the sample. In general, the activated carbon prepared from oil‐palm shell impregnated with KOH was more effective for SO₂ adsorption and its adsorptive capacity was comparable to some commercial activated carbons. © 2000 Society of Chemical Industry     

Hexafunctional poly(propylene glycol) based hydrogels for the removal of heavy metal ions

Two types of degradable poly(propylene glycol) (PPG) hydrogels that are suitable for the absorption of heavy metals have been presented. The PPG‐O‐P(O)Cl₂ fragments obtained by treating hexafunctional PPG with phosphorous oxychloride (POCl₃) react with 1,3‐propanediamine (PDA; Gel‐1 ) or PDA together with 1,2‐ethanedithiol ( Gel‐2 ), to yield cross‐linked and water‐swellable hydrogels in a one‐pot method. This protocol for the fabrication of PPG hydrogels exhibits promising advantages over prior methods including a short reaction time, mass‐production, easy separation, and high yield. A series of heavy metal ions were employed to test the adsorptive properties of the hydrogels. Gel‐2 shows better adsorption capacity than Gel‐1 for all the metal ions and the metal ions adsorption efficiency of the two types of hydrogels is in the order of Fe(III) > Pb(II) > Cd(II) > Zn(II) > Cu(II) > Ni(II) > Co(II) > Hg(II). The amounts of metal ions adsorbed increases with metal ion concentration and hydrogel dosage, but decreases with temperature. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40610.     

Adsorptive bleaching of soybean oil with non-montmorillonite Zambian clays

As an alternative to montmorillonite clay, three local Zambian clays have been used to bleach soybean oil. The bleaching action of the natural clays was poor when compared with commercial acid-activated montmorillonite (M-C) and activated charcoal (A-C) adsorbents. However, acid-activation of the Zambian clays profoundly increased their adsorptive activity. Reduction of 88% in soybean oil color (Lovibond Red) by each of the three activated Zambian clay samples represented an efficiency close to that of montmorillonite (94%) and better than activated charcoal (63%). Peroxide value (PV) of the oil was reduced by 85% (M-C) and 78% (A-C) while 68% was the highest reduction for the activated Zambian clays. After 12 wk of storage at ambient temperature, the bleached soybean oil samples showed some oxidation. Consideration of the totox values indicated that the Zambian clay-bleached oil was more stable over this length of storage when compared with the M-C bleached oil. The bleaching action shown by aluminum-exchanged clays was closely related to their acid-activated counterparts. These results demonstrate a dependency of adsorptive bleaching with Zambian clays on proton availability. Comparative powder x-ray diffraction analysis of the clays showed that quartz was the major mineral present, followed by kaolinite. No montmorillonite was detected. It was concluded that by appropriate treatment to generate Brönsted acidity (protons), Zambian clays can be converted into potent adsorbents for soybean oil impurities.     

Adsorption of Phenol and Nitrophenol Isomers onto Montmorillonite Modified with Hexadecyltrimethylammonium Cation

ABSTRACT

Single- and two-component competitive adsorptions were carried out in a batch adsorber to investigate the adsorption behavior of phenol and 2-, 3-, and 4-nitrophen-ols in aqueous solution at 25°C onto hexadecyltrimethylammonium (HDTMA)-treated montmorillonite. HDTMA cation was exchanged for metal cations on the montmorillonite to prepare HDTMA—montmorillonite, changing its surface property from hydrophilic to organophilic. Effective solid diffusivity of HDTMA cation in the montmorillonite particle was estimated to be about 3 × 10^?12 cm²/s by fitting the film-solid diffusion model to a set of HDTMA adsorption kinetic data onto mont-morillonite. Adsorption affinity on HDTMA—montmorillonite was found to be in the order 3-nitrophenol = 4-nitrophenol > 2-nitrophenol > phenol. The Langmuir and the Redlich—Peterson (RP) adsorption models were used to analyze the single component adsorption equilibria. The ideal adsorbed solution theory (IAST) and the Langmuir competitive model (LCM) were used to predict the multicomponent competitive adsorption equilibria. These models yielded favorable representations of both individ-ual and competitive adsorption behaviors.     

Adsorption of diquat, paraquat and methyl green on sepiolite: experimental results and model calculations

Adsorption of the divalent organic cations paraquat (PQ), diquat (DQ) and methyl green (MG) on sepiolite was determined experimentally and investigated with an adsorption model. The largest amounts of DQ, PQ and MG adsorbed were between 100% and 140% of the cation exchange capacity (CEC) of sepiolite. In previous experiments with monovalent organic cations (dyes), the largest amounts of dyes adsorbed were about 400% of the CEC of sepiolite. Consequently, it was proposed that most of this adsorption was to neutral sites of the clay. The large differences between the adsorption of these divalent organic cations and the monovalent dyes may indicate that there is almost no interaction between DQ, PQ and MG and the neutral sites of sepiolite. This assumption was confirmed by infrared (IR) spectroscopy measurements, that did not show changes in the peaks arising from the vibrations of external Si---OH groups of the clay when the divalent organic cations were added. Adsorption results were compared with calculations of an adsorption model that combines the Gouy–Chapman solution and specific binding in a closed system. The model considers cation adsorption on neutral sites of the clay, in addition to adsorption to mono- or divalent negatively charged sites, forming neutral or charged complexes. The model could adequately simulate the adsorption of the divalent organic cations DQ and PQ when added alone, and could yield good fit for the competitive adsorption experiment between the monovalent dye methylene blue and DQ. In competitive adsorption experiments, when total cationic charges exceeded the CEC, monovalent organic cations were preferentially adsorbed on the clay at the expense of the divalent cations.