Novel carrageenan-based hydrogel nanocomposites containing laponite RD and their application to remove cationic dye

Novel hydrogel nanocomposites were synthesized by solution polymerization of acrylamide in the presence of carrageenan biopolymer and laponite RD clay. Laponite was used as an inorganic cross-linker. Ammonium persulfate was applied as an initiator. The structure and morphology of the nanocomposites were investigated using XRD, scanning electron microscopy, and transition electron microscopy techniques. The influence of both laponite nanoclay and the carrageenan content on the swelling degree of nanocomposites was studied and it was found that all nanocomposites containing carrageenan component have a high swelling degree compared to a nanocomposite without carrageenan. The obtained nanocomposites were examined to remove a cationic crystal violet (CV) dye from water. The effect of carrageenan and clay contents on the speed of dye adsorption revealed that while the rate of dye adsorption is enhanced by increasing the clay content, it was depressed as the carrageenan content increased in nanocomposite composition. The results showed that the pseudo-second-order adsorption kinetic was predominant in adsorption of CV onto nanocomposites. The experimental equilibrated adsorption capacity of nanocomposites was analyzed using Freundlich and Langmuir isotherm models. The results indicated that the experimental data fit the Langmuir isotherm best. Maximum adsorption capacity was obtained for carrageenan-free nanocomposite with 79.8?mg?g^?1 of adsorbed CV onto nanocomposite.     

Synthesis of kappa-carrageenan-g-poly(acrylamide)/sepiolite nanocomposite hydrogels and adsorption of cationic dye

In this study, nanocomposite hydrogels from grafting of acrylamide onto kappa-carrageenan biopolymer were prepared in the presence of sepiolite clay. Methylenebisacrylamide and ammonium persulfate were used as cross-linker and initiator, respectively. The sepiolite nanoclay was introduced into hydrogel matrix without any chemical treatment. The structure of nanocomposites was investigated by FTIR, SEM, TEM, and TGA techniques. The TEM image showed that sepiolite exists as individual needle’s shape. The swelling of hydrogels were studied in distilled water, salt solutions, and various pHs. The obtained nanocomposites were evaluated to remove of cationic crystal violet (CV) dye from water. The kinetic and isotherm of adsorption of dye onto nanocomposites were studied and analyzed according to kinetic and isotherm models. The results showed that the pseudo-second-order adsorption kinetic was predominated for the adsorption of CV onto nanocomposites. The experimental equilibrated adsorption capacity of nanocomposites was analyzed using Freundlich and Langmuir isotherm models. The results corroborated that the experimental data fit the Langmuir isotherm the best. By varying the pH of initial dye solution, while the clay-free hydrogel showed relatively pH-independent adsorption behavior, the nanocomposites depicted pH-dependent adsorption.     

Dye Adsorption on Cubic Polyhedral Oligomeric Silsesquioxane-Based Poly(acrylamide-<Emphasis Type="Italic">co</Emphasis>-itaconic acid) Hybrid Nanocomposites: Kinetic,Thermodynamic and Isotherms Studies

In the present study, poly(acrylamide-co-itaconic acid) hybrid nanocomposites were synthesized via free radical copolymerization method. Octavinyl polyhedral oligomeric silsesquioxane (OV-POSS) with different weight ratio (0, 4, 8, 12 and 14 wt%) was utilized as a cross-linker. Dye adsorption properties of the as-prepared hybrid nanocomposites were investigated for crystal violet (CV) elimination from aqueous solution. The effect of various parameters, such as OV-POSS content, adsorbent amount, pH, temperature, contact time and initial dye concentration, on the adsorption of CV was studied. Moreover, adsorption kinetic, isotherm and the thermodynamic of the CV adsorption on the so-called hybrid nanocomposites were studied.     

Fabrication and characterization of functionally graded nanoclay/glass fiber/epoxy hybrid nanocomposite laminates

In this work, hardness, tensile, impact, bearing strength and water absorption tests were performed to study the mechanical properties of stepwise graded and non-graded hybrid nanocomposites. Three different stepwise graded nanocomposites and one non-graded (homogeneous) nanocomposite with the same geometry and total nanoclay content of 10 wt% were designed and prepared. Moreover, one neat glass fiber laminate was manufactured. The results of the tests indicated that addition of the graded and non-graded nanoclay improves hardness over neat glass fiber reinforcement. The maximum increase in hardness of about 53% over neat specimen is obtained for specimens that have the highest weight percentage (2 wt%) of the clay nanoparticles on its surface (S-specimen and the side of F-specimen that reinforced with 2 wt% nanoclay). The gradation process results in an increase in hardness of about 11% compared with non-graded (homogeneous) specimen. In addition, an improvement of 11.9% in strain-to-failure is achieved with specimen having greatest amount of nanoclay in the middle over neat glass fiber/epoxy composite. The other nanoclay-filled glass fiber composites have strain-to-failure close to neat glass fiber/epoxy. The addition of nanoclay reinforcement has insignificant effect on ultimate tensile strength, tensile modulus, water absorption, bearing strength and impact strength compared with neat glass fiber/epoxy.     

Porous Carrageenan-<Emphasis Type="Italic">g</Emphasis>-polyacrylamide/bentonite superabsorbent composites: swelling and dye adsorption behavior

A novel superabsorbent composite based on kappa-Carrageenan (κC) was prepared by graft copolymerization of acrylamide (AAm) onto κC in the presence of bentonite powder using methylenebisacrylamide (MBA) as a crosslinking agent, ammonium persulfate (APS) as an initiator, and sodium carbonate as a pore-forming agent. The swelling behavior in distilled water and in solutions with different pH values was investigated. The results indicated that with increasing carrageenan/bentonite weight ratio, the swelling capacity is increased but the gel content is decreased. The swelling rate of the hydrogels was improved by introducing sodium carbonate as pore-forming agent. The prepared superadsorbent composites were used as adsorbent for a cationic dye, methylene blue. Isotherm of adsorption and the effect of pH, adsorption dosage, contact time and initial dye concentration on dye adsorption were also studied. The results showed that maximum adsorption capacity of methylene blue on the prepared adsorbents is 156.25 mg g^?1 and adsorption is well-described by Langmuir isotherm model.     

Magnetic and K+-cross-linked kappa-carrageenan nanocomposite beads and adsorption of crystal violet

Biopolymer-based magnetic beads, composed of kappa-carrageenan (κ-Car) and Fe₃O₄ nanoparticles, were synthesized. The magnetic beads were prepared through in situ precipitation of Fe²⁺/Fe³⁺ ions in the presence of carrageenan and subsequently treating with K⁺ solution. The structure of magnetic kappa-carrageenan beads (mκ-Carb) was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometer, and thermal gravimetric analysis techniques. According to SEM micrographs, an undulant and coarse structure with cubic-shaped sections was obtained when the magnetic nanoparticles were incorporated in composition of beads. The TEM image confirmed the formation of magnetic nanoparticles with an average size of 3–7 nm. The synthesized beads were examined as adsorbent to remove crystal violet dye from aqueous solutions. It was found that due to coarse surface, the rate of dye adsorption on magnetic beads can be improved slightly. The experimental adsorption kinetics was analyzed according to pseudo-first-order and pseudo-second-order kinetic models and the adsorption kinetics followed well the pseudo-second-order model. Isotherm adsorption data of dye on beads were modeled according to Langmuir and Freundlich isotherm models. The results revealed that the experimental data have the best fit to Langmuir isotherm model, and maximum adsorption capacity of beads for dye obtained was 84.7 mg/g. The influence of pH on the variation of adsorption capacity of beads for crystal violet was not considerable. The thermodynamic parameters indicated that the adsorption of CV dye on beads is spontaneous.     

Mechanical response and rheological properties of polycarbonate layered‐silicate nanocomposites

The effect of clay loading on the mechanical behavior and melt state linear viscoelastic properties of intercalated polycarbonate (PC) nanocomposites was investigated. At low frequencies, the linear dynamic oscillatory moduli data revealed diminished frequency dependence with increasing nanoclay loading. The 3.5 and 5 wt% clay nanocomposites exhibited dramatically altered relaxation behavior, from liquid‐like to pseudo‐solid–like, compared to the pure PC and the 1.5 wt% clay nanocomposite. Thermal degradation of PC resulted from the melt compounding of organo‐modified nanoclays was evident from the reduction in the glass transition temperature and molecular weight of the PC nanocomposites. These nanocomposites also exhibited a significant decrease in the extent of tensile elongation and ductility with respect to the nanoclay incorporation. A concomitant decrease in the rheological properties at high frequencies was also observed, and was consistent with the lowering of the molecular weight of PC, particularly near or above the percolation threshold of nanoclay. These nanocomposites, nevertheless, exhibited elastic‐plastic deformation in compression, regardless of nanoclay content. Polym. Eng. Sci. 44:825–837, 2004. © 2004 Society of Plastics Engineers.     

INHIBITING EFFECT OF CRYSTAL VIOLET DYE ON ALUMINUM CORROSION IN ACIDIC AND ALKALINE MEDIA

Crystal violet dye (CV) was studied as a corrosion inhibitor for aluminum in hydrochloric acid (1 mol dm^?3) and potassium hydroxide (0.5 mol dm^?3) solutions in the temperature range 30°–60°C using the gravimetric technique. The effect of iodide ions on the inhibiting efficacy of CV was also assessed. CV was found to inhibit Al corrosion in both aggressive media, exhibiting greater inhibition efficiency in 1 M HCl (83.6%) than in 0.5 M KOH (23.0%). Inhibition efficiency in 0.5 M KOH was, however, synergistically increased in the presence of iodide ions to attain values up to 85.3%. Inhibition efficiency in the acidic and alkaline solutions increased with CV concentration but decreased with rise in temperature, suggesting physical adsorption of CV on the Al surface. The calculated values of activation energy (E_a), free energy of adsorption (ΔG_ads), and heat of adsorption (Q_ads) confirm the physisorption mechanism. The inhibitor adsorption characteristics were approximated by the Freundlich adsorption isotherm.     

Sound isolation properties of polycarbonate/clay and polycarbonate/silica nanocomposites

The soundproofing properties of polycarbonate (PC)/nanoclay and PC/nanosilica nanocomposites were studied through testing and theoretical analysis. Nanocomposite sheets with a 3 mm thickness were fabricated by direct hot-compression molding process. The nanoclay and nanosilica particles were incorporated into the PC matrix by a twin-screw extruder. The dispersion efficiency of 1, 3 and 5 wt% nanoclay and nanosilica in the PC matrix was investigated by transmission electron microscopy. Dynamic mechanical analysis was performed for evaluation of mechanical properties of nanocomposites. Sound transmission loss (STL) was measured by an impedance tube over the frequency range of 1600–6300 Hz, and further employed in sound proofing characterizations of nanocomposites. A new finite element model was developed to model the sound transmission loss in impedance tube test. The results showed that the PC/3 wt% nanoclay and 3 wt% nanosilica nanocomposites had an average maximum increase of 5.5 and 6 dB in STL values in the stiffness control region (1600–3600 Hz), respectively. On the other hand, the PC/3 wt% nanoclay and PC/3 wt% nanosilica nanocomposites showed the same sound isolation characteristics in the frequency range of 1600–3600 Hz. In addition, the finite element model developed for modeling the sound transmission loss in the impedance tube demonstrated a good correlation between the theoretical curves and the experimental results in the stiffness control region for both nanocomposites.     

Bio-based Sulfonated Epoxy/Hyperbranched Polyurea-modified MMT Nanocomposites

Hyperbranched polyurea modified nanoclay was used for the preparation of vegetable oil modified sulfone epoxy nanocomposites at different loadings (1–5 wt%) for the first time. The bio-based nanocomposites were characterized by XRD, SEM, TEM, and FTIR techniques. These nanocomposites showed an enhancement of thermal stability up to 48°C as revealed by thermo-gravimetric analysis. The nanocomposites with 5 wt% of nanoclay exhibited more than 300 percent improvement in tensile strength, though the elongation at break decreases with the increase of nanoclay loading. Thus the studied nanocomposites possess better performance over the pristine system.     

Improvement of Tensile and Flexural Properties in Epoxy/Clay Nanocomposites Reinforced with Weave Glass Fiber Reel

The tensile strength, tensile modulus, flexural strength and flexural modulus properties were investigated on epoxy/clay nanocomposites to assess the influence of nanoclay. Mechanical properties were significantly increased due to an increase in clay content up to 5 wt%, and decreased with a further increase in clay content. Optimal improvement of properties was observed with increased clay content up to 5 wt%. Duo properties of the glass fiber were improved by clay addition due to the improved interface between the glass fiber and epoxy. SEM analysis was conducted on different fractured surfaces to study the mechanical behavior.     

Analysis of synergistic effect of nanozinc/nanoclay additives on the corrosion performance of zinc‐rich polyurethane nanocomposite coatings

The aim of this study was to analyze the synergistic effect of clay and zinc nanopigments. Therefore different percentages of Montmorillonite clay nanolayers were added to zinc‐rich polyurethane nanocomposites. Ultrasonication process was used to prepare polyurethane/nanozinc/nanoclay nanocomposites. Then coatings were applied on steel panels with composition of 10 wt% nanozinc and 0.5, 1, 1.5, and 2 wt% nanoclay. TEM and XRD were used to analyze the structural characteristics of the nanocomposites. The results of the structure analysis revealed the size of nanomaterials and confirmed the appropriate dispersion in polymer matrix. The anticorrosive properties of the nanocomposites were investigated using salt fog test and electrochemical impedance spectroscopy (EIS). The results of EIS showed that addition of clay nanolayers improves the corrosion resistance of coatings and the best corrosion performance obtained for the nanocomposite sample with 2 wt% nanoclay. Also, according to the results of the salt spray test, the sample with 2 wt% nanoclay showed the least H₂O penetration and exfoliation adjacent to the scratches. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Adsorptive polyHIPE composites based on biosorbent immobilized nanoclay: Effects of immobilization techniques

Styrene/divinyl benzene‐based macroporous polyHIPE composites were prepared from water‐in‐oil (w/o) high internal phase emulsion (HIPE) templates by using both organo‐modified montmorillonite (MMT) and a nonionic surfactant. For this purpose, Spirulina (Sp) microalgae was immobilized onto Na‐MMT clay by using two different modification techniques. They are based on conventional adsorption in solution (SOL) and novel cryoscopic expansion (C‐XP) assisted adsorption. Highly porous nanocomposites were prepared by using different percentages of modified nanoclays (SpSOLM/SpXPM) with a constant internal phase volume of 80%. The emulsion stability, morphology, and dye adsorption capacities were discussed by paying attention to nanoclay immobilization techniques, clay loading degree and surfactant concentration. The critical amount of nonionic surfactant for formation of the stable neat HIPE template was found to be only 5 vol% with respect to volume of organic phase. However, this amount was further reduced to much less value (2 vol%) with Sp immobilized nanoclays via help of cooperative interactions of Sp and MMT nanoclay. The C‐XP assisted modification of clay led to nanocomposites with 580% higher adsorption capacity for cationic dye. This remarkable benefit was obtained with even 0.5% clay loading and only 2% surfactant concentration. POLYM. ENG. SCI., 58:1229–1240, 2018. © 2017 Society of Plastics Engineers     

EFFECT OF TEMPERATURE ON THE ADSORPTION OF METHYLENE BLUE DYE ONTO SULFURIC ACID–TREATED ORANGE PEEL

The present study explains the preparation and application of sulfuric acid–treated orange peel (STOP) as a new low-cost adsorbent in the removal of methylene blue (MB) dye from its aqueous solution. The effects of temperature on the operating parameters such as solution pH, adsorbent dose, initial MB dye concentration, and contact time were investigated for the removal of MB dye using STOP. The maximum adsorption of MB dye onto STOP took place in the following experimental conditions: pH of 8.0, adsorbent dose of 0.4 g, contact time of 45 min, and temperature of 30°C. The adsorption equilibrium data were tested by applying both the Langmuir and Freundlich isotherm models. It is observed that the Freundlich isotherm model fitted better than the Langmuir isotherm model, indicating multilayer adsorption, at all studied temperatures. The adsorption kinetic results showed that the pseudo-second-order model was more suitable to explain the adsorption of MB dye onto STOP. The adsorption mechanism results showed that the adsorption process was controlled by both the internal and external diffusion of MB dye molecules. The values of free energy change (ΔG ^o) and enthalpy change (ΔH ^o) indicated the spontaneous, feasible, and exothermic nature of the adsorption process. The maximum monolayer adsorption capacity of STOP was also compared with other low-cost adsorbents, and it was found that STOP was a better adsorbent for MB dye removal.     

Effect of clay dispersion methods on the mechano-dynamical and electrical properties of epoxy–organoclay nanocomposites

The effect of different clay dispersion methods on the mechano-dynamical and electrical properties of epoxy/clay nanocomposites was investigated. Three different clay dispersion methods (high-speed mechanical shearing, ultrasonication (US), and an optimal combination of high-speed shearing and US) were used for the dispersion of the clay in the epoxy resin. 3 wt% of an organoclay, cloisite 30B, was used as the nanoclay. Wide-angle X-ray diffraction technique and electron microscopic techniques (SEM and TEM) were used to study the morphology of the nanocomposites. Dynamic mechanical analysis was used to study the dynamo-mechanical properties. Studies on the dielectric breakdown strength (EBD) of the nanocomposites show that the EBD strongly depends on the clay dispersion time and clay dispersion method. Pulsed electro-acoustics method measurement shows that the space charge accumulation was considerably reduced in the nanocomposites. In particular, reduction in space charges after polarization depends on the dispersion of the nanofillers, the better the degree of dispersion, the lower the space charges observed.     

Radiation synthesis and characterization of styrene/acrylic acid/organophilic montmorillonite hybrid nanocomposite for sorption of dyes from aqueous solutions

Organophilic montmorillonite (OMMT) was synthesized by cationic exchange reaction of Na⁺‐MMT and vinyl benzyl triethyl ammonium chloride (VBTAC) as a reactive organic modifier in an aqueous solution. A series of styrene (St)/acrylic acid (AA)/OMMT nanocomposite hydrogel containing different wt% of OMMT was synthesized through in situ polymerization using γ‐ray. The samples were characterized using Fourier transform infrared (FTIR), X‐ray powder diffraction (XRD), and transmission electron microscope (TEM), whereas thermal stability was examined by thermogravimetric analysis (TGA). The adsorption capacity and rate for both Acid Green B (anionic) and Maxilon C.I. Basic (cationic) dye including adsorption kinetics and isotherm were investigated at 30°C. TEM measurements showed spherical nanosized particles of average diameter 30–40 nm and XRD suggested the formation of exfoliated nanocomposite. TGA measurements showed that the addition of OMMT did not enhance the thermal stability where the onset temperature of the degradation for all samples was around 125°C. The effect of some important parameters on dye adsorption such as solution pH, initial dye concentration, and contact time was investigated. The equilibrium data obtained in batch experiments were correlated to Langmuir and Freundlich isotherm equations. Results showed that the adsorption of Acid Green B fitted well to the Langmuir model while the adsorption pattern of Maxilon C.I. Basic followed the Freundlich isotherm, which suggests heterogeneity of the adsorption sites on the nanocomposite. POLYM. COMPOS., 35:2353–2364, 2014. © 2014 Society of Plastics Engineers     

Adsorption Behavior of Cationic and Anionic Dyes onto Acid Treated Coconut Coir

The adsorption of Methylene Blue (MB) and Acid Orange 7 (AO7) from aqueous solutions by acid treated coconut coir was investigated under laboratory conditions to assess its potential in removing cationic and anionic dyes. The acid treated coconut coir exhibited better adsorption capacity in cationic dye MB than anionic dye AO7 and the data obtained can be well described by both Langmuir and Freundlich isotherm models. According to the Langmuir isotherm model, the maximum adsorption capacities of MB and AO7 onto acid treated coconut coir were 121 mg/g and 10 mg/g, respectively. The adsorption behavior of MB and AO7 onto acid treated coconut coir was analyzed with first-order Lagergren model and pseudo-second order model.     

Effect of bis[2-(methacryloyloxy)ethyl] phosphate as a crosslinker on poly(AAm-co-AMPS)/Na-MMT hydrogel nanocomposite as potential adsorbent for dyes: kinetic,isotherm and thermodynamic study

In the present study, synthesis of poly(AAm-co-AMPS)/Na-MMT hydrogel nanocomposite with different amount of bis[2-(methacryloyloxy)ethyl] phosphate as a crosslinker was successfully carried out for the removal of crystal violet (CV), methylene blue (MB) and methyl red (MR) from aqueous solution. Hydrogel nanocomposite was characterized by FT-IR, SEM, EDS, XRD and TGA analysis. Several important parameters were investigated to obtain maximum adsorption capacity. Adsorption behavior of hydrogel nanocomposite was investigated for the adsorption of dyes and it was found to remove about 80% for CV, 89% for MB and 51% for MR in 50 mg/L of dyes solutions at pH 7 and about 86% for CV, 93% for MB and 23% for MR at pH 12. Kinetic studies revealed that the applicability of pseudo-first-order and pseudo-second-order model for the adsorption of CV, MB and MR. The adsorption isotherm was studied in 25, 35, 45 and 55 °C using Langmuir, Freundlich, Temkin and Jovanovic models and the adsorption data were well described by Freundlich isotherm model. Hydrogel nanocomposite showed 155, 176 and 113 mg/g maximum adsorption capacity for CV, MB and MR respectively. Negative values of ΔG⁰ for all three dyes suggested the feasibility of dyes removal and support for spontaneous adsorption of CV, MB and MR on hydrogel nanocomposite. Desorption of dyes from the dye loaded hydrogel nanocomposite was simply done in ethanol. The results indicate that the prepared poly(AAm-co-AMPS)/Na-MMT hydrogel nanocomposite is an efficient adsorbent with high adsorption capacity for the aforementioned dyes.

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Graphical abstract Graphical abstract illustrating the preparation and dye adsorption processes of the poly(AAm-co-AMPS)/Na-MMT hydrogel nanocomposite

     

Adsorption of poly (4‐sodium styrene sulfonate) on kaolinite clays

The adsorption of polymer on clay particles has great importance in many industrial applications. This work aimed to study the adsorption of anionic polymer, poly (4‐sodium styrene sulfonate), on kaolinite clay surfaces. Three different Egyptian kaolinite clay samples were used. The kaolinite clays were saturated with sodium or calcium cation. It was found that the Freundlich isotherm is applicable for this polymer adsorption on kaolinite. The parameters of the Freundlich equation are very close, indicating a comparable nature for the binding behavior between the different samples of kaolinite and the adsorbed polymer. The adsorption process was examined at different pH values (3, 6, and 9 ± 0.1) to cover the range below and above the point of zero charge of kaolinite surfaces. It was found that, below this point, the polymer adsorption increased, while above it the polymer adsorption decreased. The polymer adsorption on calcium kaolinite was higher than that of sodium kaolinite at the same pH value. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1712–1719, 2006     

Electrospun PVDF/MWCNT/OMMT hybrid nanocomposites: preparation and characterization

Electrospinning technique was employed to prepare neat PVDF, nanoclay-PVDF and carbon nanotube (MWCNT)-PVDF nanocomposites, and nanoclay-carbon nanotube-PVDF hybrid nanocomposites. A mixture of dimethyl formamide/acetone (60/40) was used to fluidize the polymer and nanofillers. Electrospinning process was conducted under optimized conditions. Maximum modification was achieved at 0.15 wt% nanofiller. Rheological measurements on the prepared solutions revealed decreased material functions in the presence of nanoclay, whereas the rheological properties of MWCNT-PVDF solution did not show any significant reduction compared with those of neat PVDF solution. The behaviors of the hybrid nanocomposite solutions, though dependent on their composition and their material functions, increased with MWCNT concentration. These differences, together with variations in electrical properties of nanoclay and MWCNT, led to changes in morphology of the fiber during electrospinning process. Under electrospinning conditions designed for neat PVDF solution, mats with beads and with the highest fiber diameter were produced. Meanwhile, incorporation of both nanoclay and MWCNT into the solutions resulted in bead-free fibers with thinner diameter. Fourier transformed infrared spectrophotometry (FTIR) and X-ray diffractometry (XRD) were used to measure the β-phase crystalline content in electrospun mats. Complete agreement was found between the FTIR and XRD results. The lowest and highest β-phase contents were obtained for neat PVDF mat and hybrid nanocomposite mat containing 0.1 wt% clay, respectively. The mixing procedure of nanofillers and the PVDF solution was also found to be important. In case of hybrid nanocomposites, more β-crystals were formed when the nanoclay was first mixed in the absence of MWCNT.