Cationized sawdust as ion exchanger for anionic residual dyes

Using the same procedure as recently described for cotton fiber, the preparation of cationized wood sawdust was performed by treating alkali sawdust with epoxy propyl trimethyl ammonium chloride (EPTMAC) in a nonaqueous medium (dimethylformamide, DMF). The fixation of ammonium groups onto sawdust was monitored by weight uptake, nitrogen content determination, and infrared spectroscopy. EPTMAC-sawdust with a 0.5 wt % nitrogen content is then used as adsorbent for acid dyes (Acid Blue 25, Acid Yellow 99, Reactive Yellow 23, and Acid Blue 74). The adsorption capacity, determined by spectrometric measurement of the residual dye in the treated solution, decreases with increasing temperature. The modeling of the adsorption isotherms using Langmuir, Freundlich, and General relations allows the determination of isotherm constants. Globally, EPTMAC-sawdust has a behavior similar to EPTMAC-cotton, and its use for depollution of waste waters from dyeing industries presents advantages over cotton, such as a larger availability and a lower price. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 31–37, 2001     

Removal of Phenol Using TDTAB- and HDTAB-Bentonites

Abstract

In this study, the use of modified bentonites for the removal of phenol was investigated. Two alkylammonium derivatives, tetradecyl trimethyl bromide (TDTAB) and hexadecyl trimethylammonium bromide (HDTAB), were used in the modification in amounts equivalent to 100% of CEC. Crude and modified bentonites were subjected to XRD analyses to see the changes in basal spacing (d _L ) depending on modification. The increases observed in basal spacing are 8.93 Å and 8.55 Å for TDTAB- and HDTAB-bentonites, respectively. Batch adsorption studies were carried at pH of 5.5 and 20°C. Adsorption isotherms of TDTAB- and HDTAB-bentonites have similar shape, and two regions are observed in isotherms. Adsorption behavior was modelled using Langmuir, Freundlich, BET, Bradley, Halsey, Henderson, Oswin, and Smith equations. The equations fitted better when the isotherm was divided into two concentration ranges. Adsorption efficiencies were defined in terms of relative increase in adsorbed amounts, and HDTAB-bentonite was found to be better.     

The Physical Characterization and Sorption Isotherm of Rice Bran Oil Powders Stabilized by Food-Grade Biopolymers

Rice bran oil (RBO) is used in several products in the food, cosmetics, and pharmaceutical industries due to its desirable health, flavor, and functional attributes. The formation and physicochemical properties of microencapsulated RBO stabilized by different biopolymers were investigated. Oil-in-water emulsions (10% RBO, citrate buffer pH 7) stabilized by either 3.5% whey protein isolate (WPI) or 7.0% modified starch (MS) containing maltodextrin (DE18) as a carrier agent were initially prepared. The diameter of emulsion droplets produced by WPI and MS were considerably smaller than 300 nm and 25 μm for dried particles. The resulting powders had poor to fair flowability and high cohesiveness characteristics: Carr index (27–37) and Hausner ratio (1.4–1.6). The microencapsulation efficiency of the spray-dried powders ranged from 92–95%. Moisture sorption isotherms of the powders were determined by a gravimetric method, while their glass transition temperatures (T_g) were determined by differential scanning calorimetry. The experimental water adsorption data were fitted to BET and GAB models. The GAB model fitted better the measured moisture isotherm than the BET model (R² = 0.99). Powders produced with MS showed higher water adsorption than those stabilized by WPI. Powders produced with WPI had a higher glass transition temperature than those produced with MS. Measurements of lipid deterioration in the RBO powder during storage showed that the reaction order was different for WPI-stabilized (n = 1) and MS-stabilized (n = 0) RBO powder. These results have important consequences for the creation of food-grade powders containing functional lipids such as RBO application.     

Biosorption of heavy metals and radionuclide from aqueous solutions by pre-treated arca shell biomass

In this study biosorption potential of pre-treated arca shell biomass for lead, copper, nickel, cobalt and cesium was explored from the artificially prepared solution containing known amount of metals. The effects of pH, initial concentration, biosorbent dosage and contact time were studied in batch experiments. Effects of common ions like sodium, potassium, calcium and magnesium on the sorption capacity of pre-treated arca biomasses were also studied. To analyse the homogeneity of the biomaterial, experiments were performed for eight lots arca shell biomass for all the studies elements and it was observed that relative standard deviation in uptake capacity was within 10% for all elements. At equilibrium, the maximum total uptake by shell biomaterial was 18.33+/-0.44, 17.64+/-0.31, 9.86+/-0.17, 3.93+/-0.11 and 7.82+/-0.36 mg/g for lead, copper, nickel, cesium and cobalt, respectively, under the optimised condition of pH, initial concentration, biosorbent dose and contact time. Effect of all the common ions jointly up to concentration of 50 ppm was negligible for all the elements but at higher levels the cations affects the uptake capacity. Sorption isotherms were studied to explain the removal mechanism of both elements by fitting isotherms data into Lagergren, Freundlich and Langmuir equations. Halls separation factor estimated under optimised condition also favours the sorption potential of these elements using arca shell biomass. Arca shell biomass can be effectively and efficiently employed for removal of studied elements after optimisation of parameters.     

The characterization of prepared organoclay materials (DDMA) and gas sorption of chlorobenzene

In this paper, adsorptive performance of Tunisian natural clay materials has been investigated as a potential adsorbent for Volatile Organic Compounds (VOCs). The materials used were taken from Aleg and Douiret formations in the south of Tunisia. Organoclay materials (OC) were prepared by intercalating didodecyldimethyl ammonium bromide on clay materials. This intercalation allowed the improvement of the porous texture of the studied materials. The adsorption isotherms showed that the intercalation of the didodecyldimethyl ammonium bromide on clay materials improved their adsorption capacities of chlorobenzene with an adsorption capacity up to 375 mg g⁻¹ for calcined modified clay of Douiret.     

Comparison of adsorption equilibrium of glycyrrhizic acid and liquiritin on C18 column

The adsorption isotherms of glycyrrhizic acid (GA) and liquiritin (LQ) on a C₁₈ column were compared and the competitive adsorption of the two compounds was investigated. The experimental parameters in the equilibrium isotherms were estimated by linear and nonlinear regression analyses. The adsorption equilibrium data were correlated into the linear, Langmuir, competitive Langmuir, Freundlich, and Langmuir–Freundlich isotherm models. Over a moderate concentration range, the competitive Langmuir isotherm provided the best fit to the experimental data. The regression coefficients of the competitive Langmuir adsorption isotherms were 0.9754 and 0.9855 for the mixtures of GA and LQ, respectively. The coefficients obtained for the five isotherm models confirmed the superiority of the competitive Langmuir isotherm for analyzing the adsorption data of solutes.     

Sorption of copper by a highly mineralized peat in batch and packed‐bed systems

BACKGROUND: The performance of peat for copper sorption was investigated in batch and fixed‐bed experiments. The effect of pH was evaluated in batch experiments and the experimental data were fitted to an equilibrium model including pH dependence. Hydrodynamic axial dispersion was estimated by tracing experiments using LiCl as a tracer. Six fixed‐bed experiments were carried out at copper concentrations between 1 and 60 mg dm^?3 and the adsorption isotherm in dynamic mode was obtained. A mass transport model including convection–dispersion and sorption processes was applied for breakthrough curve modelling. RESULTS: Maximum uptake capacities in batch mode were 22.0, 36.4, and 43.7 mg g^?1 for pH values of 4.0, 5.0, and 6.0, respectively. Uptake capacities in continuous flow systems varied from 36.5 to 43.4 mg g^?1 for copper concentrations between 1 and 60 mg dm^?3. Dynamic and batch isotherms showed different shapes but a similar maximum uptake capacity. Sorbent regeneration was successfully performed with HCl. A potential relationship between dispersion coefficient and velocity was obtained with dispersion coefficients between 5.00 × 10^?8 and 2.95 × 10^?6 m² s^?1 for water velocities ranging between 0.56 × 10^?4 and 5.03 × 10^?4 m s^?1. The mass transport model predicted both the breakpoints and the shape of the breakthrough curves. CONCLUSIONS: High retention capacities indicate that peat can be used as an effective sorbent for the treatment of wastewater containing copper ions. Copyright © 2009 Society of Chemical Industry     

Temperature and solvent effects on polyphenol extraction process from chestnut tree wood

Polyphenols are a group of chemical substances found in plants, characterized by the presence of more than one phenol unit or building block per molecule. Polyphenols are generally divided into hydrolysable tannins (gallic acid esters of glucose and other sugars) and phenylpropanoids, such as lignins, flavonoids, and condensed tannins.They are widely found in natural products, nowadays they are extensively used in food and beverage industry and in pharmaceutical and nutraceutical industry for their positive effects on human health.In conventional processes polyphenols are extracted from vegetable material using water as solvent in a temperature range from 40 to 90 °C.The aim of this work is to characterize chestnut tree wood in terms of total extractable polyphenols and assess the temperature and solvent type effects on the polyphenol extraction process. To this end, experimental data on equilibrium distribution of polyphenols between solid and liquid phases for different temperatures (ranging from 60 to 80 °C) and different solvent solutions (water and ethanol-water solutions) are reported. The obtained results have been correlated by means of Freundlich isotherm.Experimental data are also reported about the batch extraction kinetics of polyphenols from solid phase and analysed by a mathematical model to estimate the polyphenol diffusion coefficient inside the chestnut wood particles and the mass transfer coefficient in the liquid phase.     

Chemical components of mature areca nut husk extract as a potential corrosion inhibitor for mild steel and copper in both acid and alkali media

Mature areca nut husk (MAH) extract was tested for its efficacy anticorrosive property at electrode–electrolyte interface through chemical and electrochemical techniques. Results of weight loss study show that maximum inhibition action of MAH extracts for copper and mild steel in both acid and alkali media was observed at 303?K with the contact time of 1 hour (94.347% for mild steel in 0.5?M HCl medium, 91.666% for mild steel in 0.5?M NaOH medium, 93.750% for copper in 0.5?M HCl medium, and 90.000% for copper in 0.5?M NaOH medium). Protection efficiency values are inverse relationship with the temperature, which indicates the physical nature of protective film on the metal surface. Adsorption characteristics of the MAH extract on the electrode surface in a hostile fluid environment are consistent with the Langmuir isotherm model under study conditions, which indicates the monolayer formation of inhibitor on electrode surfaces. Results of Tafel study confirm that MAH extract acts as an effective anodic type of inhibitor for the system copper in 0.5?M NaOH system, in the rest of the cases, it acts as a mixed type of inhibitor. From the Nyquist plot, it is clear that increased depressed semicircle area with an increase in MAH extract concentration is an evidence of the inhibitory role of plant extracts on the metal surface. Further, Fourier transform infrared spectroscopy and scanning electron microscopy techniques clearly indicated the protective film-forming ability of the MAH extract on the metal surface.