Organo-modified Montmorillonite Clay Research Articles

Fabrication and evaluation of organoclay-reinforced epoxidized natural rubber nanocomposites: A comprehensive study

The objective of this study is to assess the impact of incorporating a dual-functionalized organoclay with amine groups on the morphology and thermal characteristics of nanocomposites based on epoxidized natural rubber (ENR). To achieve this, organomodified montmorillonite clay (Cloisite30B) underwent treatment with 3-aminopropyltriethoxysilane (APS) via a silanization reaction, aiming to promote better interaction and compatibility between the two components. The structural and thermal properties of the resulting amine-functionalized Cloisite30B (f-C30B) were analyzed using infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Subsequently, various amounts of f-C30B (0, 1, 2.5, 5, 7.5, or 10 phr) were dispersed successfully in the ENR matrix using a solvent blending technique to create ENR/f-C30B nanocomposites. Standard techniques, including XRD, transmission electron microscopy (TEM), and TGA, were employed to analyze the nanocomposites for their structure and morphology. The morphological analysis revealed a uniform distribution of f-C30B throughout the ENR matrix. Moreover, TGA analysis indicated higher decomposition temperatures for ENR with f-C30B: 341 °C, 339 °C, 341 °C, 348 °C, and 352 °C for 1, 2.5, 5, 7.5, and 10 phr f-C30B, respectively, enhancing thermal stability. Char residues also rose accordingly: 2.3%, 1.9%, 3.7%, 4.9%, and 7.8%, respectively.Overall, this study highlights the potential of f-C30B as effective reinforcing agents in ENR-based nanocomposites, offering enhanced thermal stability, homogeneity, and valuable insights for the development of advanced ENR nanocomposites.

PREPARATION AND FLAME RETARDANT APPLICATION OF CLAY POLYURETHANE NANOCOMPOSITES

In recent years, clay-based organic thermosetting polyurethane polymer nanocomposites have more attracted attention in academia and industries because they exhibit different properties from conventional materials. In this study, we investigated novel thermoplastic Polyurethane (TPU) by adding nanoparticles of clay as a fire-retardant property. By employing an in-situ polymerization technique with a 2:1 ratio of tolylene 2,4-diisocyanate (TPI) and polyethylene glycol (PEG2000), the NCO terminated TPU prepolymer was created. Cloisite 25A (C25A), an organo-modified montmorillonite clay, was utilized to provide sufficient compatibility with the PEG/TPI matrix. The synthesized nanocomposite was examined using thermogravimetric analysis (TGA), SEM analysis, and X-ray diffraction (XRD). FTIR analysis provides information on functional groups. Compared to pure polyurethane, the nanocomposites showed superior thermal stabilities, as determined by thermogravimetric analysis (TGA). The results from X-ray diffraction and Scanning Electron Microscopy confirm the successful formation of an exfoliated polymer clay nanocomposite under all conditions, evidenced by the absence of the distinct peak (2θ = 4.79º) corresponding to the d-spacing of the organoclay. The relationship between clay loading and TPU matrix type and the mechanical characteristics of nanocomposites was examined. As the amount of clay in the Young's TPU/Cl25A nanocomposites grew, so did their tensile strength and modulus. The fire-retardant experiment was studied by a cone colorimeter. There have been notable advancements in the fire-retardant qualities, including smoke, CO output, and heat release rate. Comparing polyurethane integrated with 5-weight percent organoclay to ordinary polyurethane polymer, a noteworthy 53% reduction was observed.

Structure, thermal and mechanical properties of poly (ε-caprolactone)/organomodified clay bionanocomposites prepared in open air by in situ polymerization

The first example of the usefulness of titanium (IV) butoxide, as initiators for open air in-situ intercalative polymerization of ε-caprolactone (ε-CL) in the presence of organoclay is herein reported. The bionanocomposites based on poly(ε-caprolactone) (PCL) were prepared by in-situ Ring Opening Polymerization (ROP) of ε-caprolactone in the presence of different organomodified montmorillonite clay (ODA-MMT) loading (1, 3 and wt%). Structural, thermal and mechanical characterizations of the resulting bionanocomposites were investigated. The presence of the nanoclay increased PCL crystallinity, melting temperature and thermal stability, whereas some decrease in Tg was observed. TEM analyses confirmed the good dispersion of ODA-MMT with 1 and 3 wt% content into the PCL polymer as already asserted by XRD diffraction. Finally, the Young's modulus of the PCL nanocomposites was higher compared to the neat PCL, while a decrease of stress and strain at break for materials with different filler content was observed.

Effects of surface-extended inorganic particles on phase transitions and luminescence properties of 5CB liquid crystal

Effects of different inorganic fillers with surface-extended anisotropic particles, such as carbon nanotubes (NT), organomodified montmorillonite clay mineral platelets (OMMT) and hybrid (NT–OMMT) dopants, on the 5CB aggregate state sequences and phase transition temperatures have been investigated in a wide temperature range and analyzed in a comparison with the properties of the 5CB in the bulk. The observed phenomena have been explained by structure peculiarities of the composite materials, studied by polarizing microscopy and luminescence spectroscopy methods. Large clusters of NT do not influence the 5CB nematic alignment, while OMMT and NT–OMMT particles form inorganic networks of uniformly distributed dopants, disturb the 5CB ordering, and the OMMT prevents formation of a glass-like state at cooling, as in pure 5CB.

Fire Retardancy, Thermal Stability and Irradiation Studies of Modified Poly (Vinyl Chloride) composites for Industrial Applications

Poly(vinyl chloride) (PVC)composites were prepared by compounding different concentrations of antimony trioxide Sb2O3 (ATO) and Organo-modified montmorillonite clay (OMMT) as fillers under the effect of gamma irradiation in order to improve its fire retardancy properties. The fire retardacny of the prepared PVC composites were evaluated by measuring ofthe limiting oxygen index (LOI). The mechanical properties, thermal stability by using of the thermogravimetric analysis (TGA) and the electrical conductivity were also investigated. The results indicated that the addition of ATO alone up to 3 phr or the mixture of ATO 1.5 phr/ OMMT 1.5 phr enhances the fire retardancy properties, accompanied with a decrease in the mechanical properties, without effective change in the thermal and electrical conductivity. Moreover, it was found that the mechanical properties and the gel content of the prepared PVC composites were enhanced accompanied with a decreasing in the swelling ratio, as a function of the irradiation with gamma rays up to 50 kGy.

Dielectric and Electrical Properties of Poly (?-Caprolactone)/ Organomodified Clay Bionanocomposites Prepared in Open Air by in Situ Polymerization

Dielectric and electrical properties of bio-nanocomposites based on poly (?-caprolactone) (PCL) with different amounts of organomodified montmorillonite clay (MMT-ODA) were investigated by broadband dielectric spectroscopy in the frequency range from 1Hz to 1MHz and in the temperature range from -100 to 25°C. These nanocomposites were prepared by in situ Ring Opening polymerization of ?-caprolactone in open air by using titanium alkoxide as a catalyst. Due to the semicrystalline structure of PCL, the high number of modes and its overlap, the relaxation patterns observed on dielectric spectra were complicated. These relaxation data were modeled using the H-N empirical equation with the contribution of conductivity. The local dynamics of PCL were unaffected by the increase of nano-clay amount, in agreement with the DSC values of glass transition temperature. The PCL/MMT-ODA 3 wt% exhibited the lowest value of dielectric strength, indicating the strongest adhesion between PCL matrix and organo-modified clay. As for PCL/MMT-ODA 5 wt%, the presence of agglomerate made the adhesion between PCL and MMT-ODA very weak. The obtained findings were congruent FTIR and XRD results. The electrical conductivity of PCL was analysed according to the Jonscher’s law. The obtained exponent s values referred to three models corresponding to different temperature ranges.

Dielectric and Electrical Properties of Poly (?-Caprolactone)/ Organomodified Clay Bionanocomposites Prepared in Open Air by in Situ Polymerization

Dielectric and electrical properties of bio-nanocomposites based on poly (?-caprolactone) (PCL) with different amounts of organomodified montmorillonite clay (MMT-ODA) were investigated by broadband dielectric spectroscopy in the frequency range from 1Hz to 1MHz and in the temperature range from -100 to 25°C. These nanocomposites were prepared by in situ Ring Opening polymerization of ?-caprolactone in open air by using titanium alkoxide as a catalyst. Due to the semicrystalline structure of PCL, the high number of modes and its overlap, the relaxation patterns observed on dielectric spectra were complicated. These relaxation data were modeled using the H-N empirical equation with the contribution of conductivity. The local dynamics of PCL were unaffected by the increase of nano-clay amount, in agreement with the DSC values of glass transition temperature. The PCL/MMT-ODA 3 wt% exhibited the lowest value of dielectric strength, indicating the strongest adhesion between PCL matrix and organo-modified clay. As for PCL/MMT-ODA 5 wt%, the presence of agglomerate made the adhesion between PCL and MMT-ODA very weak. The obtained findings were congruent FTIR and XRD results. The electrical conductivity of PCL was analysed according to the Jonscher’s law. The obtained exponent s values referred to three models corresponding to different temperature ranges.

Composite Gel Polymer Electrolytes Based on Organo-Modified Nanoclays: Investigation on Lithium-Ion Transport and Mechanical Properties.

Composite gel polymer electrolytes (GPEs) based on organo-modified montmorillonite clays have been prepared and investigated. The organo-clay was prepared by intercalation of CTAB molecules in the interlamellar space of sodium smectite clay (SWy) through a cation-exchange reaction. This was used as nanoadditive in polyacrylonitrile/polyethylene-oxide blend polymer, lithium trifluoromethanesulphonate (LiTr) as salt and a mixture of ethylene carbonate/propylene carbonate as plasticizer. GPEs were widely characterized by DSC, SEM, and DMA, while the ion transport properties were investigated by AC impedance spectroscopy and multinuclear NMR spectroscopy. In particular, 7Li and 19F self-diffusion coefficients were measured by the pulse field gradient (PFG) method, and the spin-lattice relaxation times (T1) by the inversion recovery sequence. A complete description of the ions dynamics in so complex systems was achieved, as well as the ion transport number and ionicity index were estimated, proving that the smectite clay surfaces are able to “solvatate” both lithium and triflate ions and to create a preferential pathway for ion conduction.

Sorption Properties of Organo Modified Montmorillonite Clay for the Reclamation of Chromium (VI) from Waste Water

The natural Montmorillonite (Mt) clay was modified with three newly synthesized cationic surfactants such as 2-(dodecanoyloxy)-N,Nbis(2-hydroxyethyl)-N(oxiran-2-ylmethyl)ethane-1-ammonium chloride, 2-hydroxy- N- (2-hydroxyethyl) - N (oxiran-2-ylmethyl)-N-(2-(tetradecanoyloxy) ethyl) ethane-1-ammonium chloride and 2-hydroxy- N- (2-hydroxyethyl)-N-(oxiran-2-ylmethyl)-N- palmitoyloxy)ethyl) ethane-1-ammonium chloride to get organo OMt-I, OMt-II and OMt- III respectively. The three modified clays were characterized by Fourier Transform Infrared Spectroscopy (FT-IR), Thermo gravimetric Analysis (TGA), X - Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) techniques. The three modified OMts were utilized to reclaim Cr (VI) from wastewater and batch adsorption studies were conducted with various operational parameters such as initial Cr (VI) concentration, pH, amount of adsorbent dosage and agitation rate. The effect of pH on the adsorption of Cr (VI) indicates that the adsorption was favorable in the pH range of 6. As the amount of adsorbent dosage increases, the efficiency in the removal of Cr (VI) ions increases. Langmuir and Freundlich adsorption isotherm best fitted with the experimental isotherm data. The results show that the modified Mt has a good affinity toward the reclamation of Cr (VI) ion and the degree of the efficacy was in the order of the surfactant modified OMt III > OMt II > OMt I. This can be attributed to the increasing hydrophobic chain length of cationic surfactants.

Moisture Absorption Behaviour of Biopolymer Polycapralactone (PCL) / Organo Modified Montmorillonite Clay (OMMT) biocomposite films

Bio composite materials were fabricated using mixing biodegradable polymer polycaptalactone (PCL) and Organo Modified Montmorillonite Clay (OMMT) through solution casting. Various samples of bio composite films were prepared by varying the OMMT wt% composition by 0.1%, 0.5%, 1% and 1.5%. Thereafter, the density and water absorption of the composites were investigated with respect to immersion time in water. The moisture absorption results show that with an increase in weight percentage (from 0.1 to wt 1.5%) of OMMT within the bio polymer films, the absorption value of bio-nanocomposite films reduced rapidly from 34.4% to 22.3%. The density of hybrid composites also increased with increase in weight percentage of OMMT. The swelling characteristic of PCL increased with increasing % of OMMT clay. These results indicate that the optimized composition of constituents in composite membrane could effectively reduce the anhydrous conditions of bio-composite film.

Barrier properties and structure of liquid crystalline epoxy and its nanocomposites

There is ever increasing demand for a suitable sealant material to protect electronic devices, in particular, different displays. We present a new approach to generate a liquid processible material that possesses excellent barrier properties and flexibility that can be used for electronic encapsulation. The liquid processable material is based on liquid crystalline (LC) epoxy diglycidyl ether of 4, 4′-dihydroxy-α-methylstilbene (DGE-DHAMS or EDHAMS) and its nanocomposite comprising organo-modified montmorillonite clay. The best-achieved water vapor transmission rate is 4.5 g-mil/m2-day at ambient pressure, which is more than 20 times better than that of a conventional bisphenol A epoxy. The improved barrier performance comes from the reduction in the water diffusivity. The diffusivity in the liquid crystalline epoxy is 1.25 × 10−9 cm2/s, one order of magnitude lower than that of bisphenol A epoxy. The addition of 1 vol% of organoclay further reduces the diffusivity by 2 times. The cavity size of the free volume of the liquid crystalline epoxy is much smaller than that of conventional bisphenol A epoxy as measured by positron annihilation lifetime spectroscopy, suggesting that the improved barrier property originates from this reduced free volume cavity size. The free volume cavity size of the film with an addition of 1 vol% of an organically modified montmorillonite clay is similar to that of the liquid crystalline epoxy. We hypothesize that the additional barrier performance improvement by the nanoclay is due to its effect on the liquid crystalline phase morphology (reduced LC phase domain sizes) or the tortuosity effect of the high aspect ratio particles. The material also has excellent adhesion, optical transparency, and thermal stability.

Enhancement of thermal and mechanical properties of poly(MMA-co-BA)/Cloisite 30B nanocomposites by ultrasound-assisted in-situ emulsion polymerization

This study reports synthesis and characterization of poly(MMA-co-BA)/Cloisite 30B (organo-modified montmorillonite clay) nanocomposites by ultrasound-assisted in-situ emulsion polymerization. Copolymers have been synthesized with MMA:BA monomer ratio of 4:1, and varying clay loading (1–5wt% monomer). The poly(MMA-co-BA)/Cloisite 30B nanocomposites have been characterized for their thermal and mechanical properties. Ultrasonically synthesized nanocomposites have been revealed to possess higher thermal degradation resistance and mechanical strength than the nanocomposites synthesized using conventional techniques. These properties, however, show an optimum (or maxima) with clay loading. The maximum values of thermal and mechanical properties of the nanocomposites with optimum clay loading are as follows. Thermal degradation temperatures: T10%=320°C (4wt%), T50=373°C (4wt%), maximum degradation temperature=384°C (4wt%); glass transition temperature=64.8°C (4wt%); tensile strength=20MPa (2wt%), Young’s modulus=1.31GPa (2wt%), Percentage elongation=17.5% (1wt%). Enhanced properties of poly(MMA-co-BA)/Cloisite 30B nanocomposites are attributed to effective exfoliation and dispersion of clay nanoparticles in copolymer matrix due to intense micro-convection induced by ultrasound and cavitation. Clay platelets help in effective heat absorption with maximum surface interaction/adhesion that results in increased thermal resistivity of nanocomposites. Hindered motion of the copolymer chains due to clay platelets results in enhancement of tensile strength and Young’s modulus of nanocomposite. Rheological (liquid) study of the nanocomposites reveals that nanocomposites have higher yield stress and infinite shear viscosity than neat copolymer. Nonetheless, nanocomposites still display shear thinning behavior – which is typical of the neat copolymer.

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)/Organomodified Montmorillonite Nanocomposites for Potential Food Packaging Applications

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) is a versatile, biobased and biodegradable copolymer from the family of polyhydroxyalkanoates. This study aims to further ameliorate its properties in order to enhance its applicability for food packaging purposes through preparation of organomodified montmorillonite clay (OMMT) nanocomposites. Nanocomposites based on pure PHBHHx as well as commercial PHBHHx granulate, after a previous dry-mixing with OMMT in concentrations of 1, 3, 5 and 10 wt%, were prepared using melt blending and compression molding. Investigation of the samples showed well dispersed nanofiller and highly intercalated nanocomposites, resulting in a continuous decrease in gas permeability, lowering O2, CO2 and water vapor permeability with about 5–7 % and approximately 40 % at OMMT concentration of 1 and 10 wt%, respectively. Besides gas permeability, other properties were affected as well. Thermal stability of the samples increased gradually up to 5 wt% nanofiller, but was reduced at 10 wt%. In order to investigate the effects of OMMT and molecular weights on PHBHHx crystallization, nanocomposites were also produced by solvent-casting and compared to those obtained by melt-blending. Crystallization was retarded, because of severe lowering of molecular weight due to processing-induced chain scission, catalyzed by OMMT moisture. However, this reduction was counteracted for a large part by using commercial PHBHHx granulate, which has shown better crystallization properties. The samples were rendered increasingly more brittle, displaying higher Young’s modulus and severely reduced elongation at break. From this study it appeared that, upon viewing all affected properties as a whole, the sample based on commercial PHBHHx and containing 3 wt% OMMT shows most promise for possible applications, however further research must be performed in order to exploit their fullest potential.

Effect of Nanoclay on the Mechanical, Thermal, and Water Absorption Properties of an UP-toughened Epoxy Network

Unsaturated polyester (UP)-toughened epoxy nanocomposites were prepared, and their effective mechanical and thermal properties were studied. Two types of organo-modified montmorillonite (OMMT) clays were used to prepare the nanocomposites. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis showed the formation of exfoliated silicate layers in the UP-toughened epoxy matrix. Mechanical tests revealed that nanocomposites (containing 1 wt% OMMT clay) showed an increase in tensile strength to 13.8%, flexural strength to 10%, and impact strength to 4% compared with an UP-toughened epoxy blend. The effect of different heating rates on the curing behavior of UP-toughened epoxy nanocomposites was investigated using non-isothermal differential scanning calorimetry. The data were interpreted using the Kissinger and Flynn–Wall–Ozawa models to find the curing reaction parameter. The water uptake behavior for nanocomposites increased with the addition of OMMTs. Scanning electron microscopy micrographs indicated morphological changes in the impact fractured samples of UP-toughened epoxy nanocomposites.

Synthesis and Characterization of Acrylated Epoxidized Castor Oil Nanocomposites

Renewable resource-based epoxidized castor oil (ECO) was synthesized and used as a prime material to develop acrylated epoxidized castor oil (AECO) networks. AECO nanocomposites were prepared by the sol-gel method from organo-modified montmorillonite (OMMT) clay and silane. It was found that the AECO/1 wt.% OMMT system increased in tensile strength from 28 to 37 MPa and flexural strength from 54 to 63 MPa as compared with the AECO system. The non-isothermal cure kinetics of the bio-based systems was studied using differential scanning calorimetry. The activation energy of the AECO/OMMT system obtained from Kissinger and Flynn-Wall-Ozawa models is lower than that of AECO system.

Influence of Organoclay Structure on Nanostructured Materials Based on Eva

This article reports the preparation of a series of EVA nanocomposites employing solution casting methods using different types of organo-modified montmorillonite clay. The effect of the organoclay type on the structural organization and thermal behavior of EVA nanostructured materials were systematically investigated. Regarding thermal behavior, the thermogravimetric analysis showed that the nanocomposites presented a slight decrease in thermal degradation temperature compared to EVA, while differential scanning calorimetry, in general, did not show a significant change in the thermal transition temperatures such as glass transition, melting temperature and crystallization temperature of the nanocomposites, regardless of the type and proportion of organoclay in the systems. With respect to structural aspect, the X-ray diffractograms showed that all systems presented a heterogeneous distribution of the nanoparticles, containing part intercalated. Nuclear magnetic resonance relaxometry data provided complementary information for the X-ray results, showing that the EVA systems containing 5 wt% of both studied organoclays presented a mixture of intercalated and exfoliated structures, evidencing that there was a surface interaction between polymer chains and clay lamellae.

Simultaneous removal of multiple pesticides from water: Effect of organically modified clays as coagulant aid and adsorbent in coagulation–flocculation process

Contamination of drinking water sources with agrochemical residues became a major concern in the twenty-first century. Coagulation–flocculation is the most widely used water-treatment process, but the efficiency to remove pesticides and other organic pollutants are limited compared to adsorption process. Thus, simultaneous action of adsorption on normal bentonite or organo-modified montmorillonite clays [modified with octadecylamine (ODA-M) and octadecylamine + aminopropyltriethoxysilane (ODAAPS-M)] followed by coagulation–flocculation by alum and poly aluminium chloride has been evaluated for removal of 10 different pesticides, namely atrazine, lindane, metribuzin, aldrin, chlorpyriphos, pendimethalin, α-endosulphan, β-endosulphan, p, p′-DDT, cypermethrin and two of its metabolites, endosulphan sulphate and p, p′-DDE, from water. The coagulation without integration of adsorption was less effective (removal % varies from 12 to 49) than the adsorption–coagulation integrated system (removal % varies from 71 to 100). Further, coagulation integrated with adsorption was more effective when organically modified montmorillonite was used as adsorbent compared to normal bentonite. The removal efficiency of organic clay depends upon the concentration of pesticides, doses of clay minerals, and efficiency was more for ODAAPS-M as compared to ODA-M. The combination of ODAAPS-M-clay with coagulants was also used efficiently for the removal of pesticides from natural and fortified natural water collected and the results exhibit the usefulness of this remediation technique for application in water decontamination and in treatment of industrial and agricultural waste waters.

Effect of clay structure and type of organomodifier on the thermal properties of poly(ethylene terephthalate) based nanocomposites

In the current investigation, nanocomposites of poly(ethylene terephthalate) (PET) with different types of organo-clays were produced using the melt mixing technique. Two types of commercial inorganic clays (Laponite-synthetic hectorite and Kunipia-montmorillonite) were studied after cation-exchange with hexadecyltrimethylammonium bromide (CTAB) while two commercial organo-modified montmorillonite clays (Nanomer I.30E modified with primary octadecylammonium ions and Cloisite 10A modified with quaternary dimethyl benzyl hydrogenated-tallow ammonium ions) were also investigated. The structure of the nanocomposites was studied by X-ray diffraction measurements. A detailed crystallization analysis was carried out by means of both isothermal and non-isothermal (melt and cold) measurements. All data were analyzed using the simple Avrami equation along with advanced isoconversional methods. The nucleation activity of the filler was investigated in every case. Lauritzen–Hoffman analysis was employed to isothermal data to estimate the nucleation parameters. From all these measurements it was found that the organo-clay I.30E induces the higher crystallization rates and lower activation energy and is more effective regarding the PET crystallization compared to the other types of organo-clays. The I.30E organo-clay nanocomposite exhibited also the higher immobilized amorphous fraction and the higher nucleation parameter Kg in the Lauritzen–Hoffman analysis. This is due to its better dispersion and exfoliation of the clay nanolayers into the PET matrix, compared to the other organoclays.

Crystallinity study of nano-biocomposites based on plasticized poly(hydroxybutyrate-co-hydroxyvalerate) with organo-modified montmorillonite

The influence of nanofiller, plasticizer and hydroxyvalerate (HV) contents on the properties of poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV)/clay nano-biocomposites is studied.Analyses by wide-angle X-ray diffraction and differential scanning calorimetry showed that both the organo-modified montmorillonite clay and acetyl tributyl citrate plasticizer facilitate the crystallization process of PHBV. Despite its nucleating effect, the nanoclay hampers the spherulite growth and leads to a reduction in the copolymer crystallinity, while the addition of plasticizer induces the formation of thicker spherulites.For all studied systems, it was shown that the variation of mechanical properties of these nano-biocomposites is strongly influenced by their changes in crystallinity.

Removal of Mixed Pesticides from Aqueous Solutions using Organoclays: Evaluation of Equilibrium and Kinetic Model

Removal of mixed pesticides, namely alachlor, metolachlor, chlorpyriphos, fipronil, α-endosulfan, β-endosulfan, p,p'-DDT and two metabolites p,p'-DDE and endosulfan sulphate from aqueous solution by batch adsorption onto three commercial organo-modified montmorillonite clays [modified with octadecylamine (ODA-M), modified with dimethyl- dialkylamine (DMDA-M) and modified with octadecylamine and aminopropyltriethoxysilane (ODAAPS-M)] were investigated. Effect of process variables, mainly contact time and initial concentration of mixed pesticides, on adsorption phenomenon were evaluated. To understand the adsorption kinetic pseudo-first-order and pseudo-second-order models were tested. The pseudo-second-order model provided the best fit for explaining adsorption kinetics, on the basis of high correlation coefficient (r) and normalized percent deviation values. The adsorption equilibrium was explained by the Freundlich isotherm (r = 0.951-0.992). High values (0.17-0.52 mg g⁻¹) of Freundlich constant (K(f)) indicated higher affinity of pesticides towards all three organoclays, as a result of hydrophobic interaction between the adsorbent/adsorbate systems. Pesticides with high octanol-water partition coefficient (K(ow)) and low water solubility showed faster adsorption with higher K(f) values as compared to the pesticides with low K(ow) and high water solubility. The order of organoclays for removal efficiency of mixed pesticide was ODAAPS-M > DMDA-M > ODA-M. These findings may find application to decontaminate or treat mixed pesticide contaminated industrial/agricultural waste waters.