Sawdust Derivative for Environmental Application: Chemistry, Functionalization and Removal of textile dye from aqueous solution.

The adsorption of Violet Remazol 5R (VR 5) on wood sawdust modified with succinic anhydride (SSA) as a function of contact time, pH, and initial dye concentrations was investigated using a batch technique under ambient conditions. The SSA obtained was confirmed by IR spectroscopy, thermogravimetry and 13C NMR, and degrees of substitution (DS) were calculated. A study on the effect of the pH on the adsorption of VR 5 showed that the optimum pH was 2.0. The interactions were assayed with respect to the pseudo-first-order and pseudo-second-order kinetic models, and were found to follow closely the pseudo-second-order. The isotherm was adjusted to the Langmuir, the Freundlich and the Temkin sorption models. SSA is a promising material for the removal of dye textile from aqueous solutions, and under conditions studied the removal percentage achieved was 51.7%.

Free amino and imino-bridged centres attached to organic chains bonded to structurally ordered silica for dye removal from aqueous solution.

Ordered mesoporous SBA-15 type silica was synthesized by sol gel polymerization and reacted with 3-aminopropyltriethoxysilane (AP) or triethylenetetramine (TE), to attach pendant chains or bridging molecules, with basic centres. The materials were characterized by elemental analysis, infrared spectroscopy, and nuclear magnetic resonance in the solid state, X-ray diffractometry, scanning and transmission electron microscopy. The nitrogen sorption/desorption data for SBA-15 and the organofunctionalized SBA-15AP and SBA-15TE silicas resulted in IV type isotherms with hysteresis loops of the H1 type, surface areas of 800; 213 and 457 m(2) g(-1) and average pore diameters of 8.0; 3.2 and 6.8 nm, respectively. The ordered structural features of the mesoporous silica remained preserved after post-functionalization with pendant and bridged organic chains. Sorption data for organofunctionalized silicas gave highly selective sorption capacities for anionic water soluble Reactive Blue dye, with 0.064 and 0.072 mmol g(-1). Negligible sorption was observed with the unmodified mesoporous silica. The results suggest that organofunctionalized silica can be a simple, efficient, inexpensive and suitable method for the effective and selective removal of anionic organic dye pollutants from aqueous solutions.

Triplet state of 4-methoxybenzyl alcohol chemisorbed on silica nanoparticles.

The knowledge of photochemical kinetics in colloidal systems is important in understanding environmental photochemistry on dispersed solid surfaces. As model materials for the chemically sorbed organic compounds present in natural environments, modified silica nanoparticles (NPs) were obtained here by condensation of the silanol groups of fumed silica nanoparticles with 4-methoxybenzyl alcohol. These particles were characterized by different techniques. To evaluate their toxicity, the inhibition of the natural luminescence emission of the marine bacterium Vibrio fischeri in suspensions of the particles was measured. Laser flash-photolysis experiments (λ(exc) = 266 nm) performed with NP suspensions in acetonitrile-aqueous phosphate buffer mixtures showed the formation of the lowest triplet excited state of the chemisorbed organic groups (λ(max) = 390 nm). DFT calculations of the absorption spectrum of this radical support the assignment. From the calculated triplet energy, a thermodynamically favorable energy transfer from these triplet states to oxygen to yield singlet molecular oxygen is predicted. A value of 0.09 was measured for the quantum yield of singlet molecular oxygen generation by air-saturated suspensions of the nanoparticles in the mixture of solvents acetonitrile-aqueous phosphate buffer. The quantum yield of singlet molecular oxygen generation by the free 4-methoxybenzyl alcohol in the same solvent is 0.31.

The removal of reactive dyes from aqueous solutions using chemically modified mesoporous silica in the presence of anionic surfactant-the temperature dependence and a thermodynamic multivariate analysis.

The three-parameter Sips adsorption model was successfully employed to modeled equilibrium adsorption data of a yellow and a red dye onto a mesoporous aminopropyl-silica, in the presence of the surfactant sodium dodecylbenzenesulfonate (DBS) from 25 to 55 degrees C. The results were evaluated in relation to the previously reported surface tension measurements. The presence of curvatures of the van()t Hoff plots suggested the presence of non-zero heat capacities terms (Delta(ads)C(p)). For the yellow dye, it is observed that the values of Delta(ads)H are almost all positive and they decrease in endothermicity, in the absence and in the presence of DBS, from 25 to 55 degrees C. For the red dye, there is an increase in endothermicity in relation to the temperature increase. The negative Delta(ads)G values indicate spontaneous adsorption processes. Almost all adsorption entropy values (Delta(ads)S) were positive. This suggests that entropy is a driving force of adsorption. The adsorption thermodynamic parameters were also evaluated using a new 2(3) full factorial design analysis. The multivariate polynomial modelings indicated that the thermodynamic parameters are also affected by important interactive effects of the experimental factors and not by the temperature changes alone.

The use of molecular probes for the characterization of dispersions of functionalized silica nanoparticles.

Butoxylated silica nanoparticles (BSN) were prepared by esterification of the silanol groups of fumed silica nanoparticles with butanol and characterized by 13C and 29Si NMR and thermogravimetry. The molecular probes benzophenone (BP) and safranine-T were used to investigate the BSN suspensions in water:acetonitrile. Laser flash-photolysis experiments at lambda(exc)=266 nm performed with BSN suspended in acetonitrile:aqueous phosphate buffer supported previous results of our group obtained by time-resolved phosphorescence experiments and showed that only free and adsorbed excited triplet states of BP and diphenylketyl radicals contribute to the signals. The UV-vis spectroscopic and photophysical properties of safranine-T are strongly solvent-dependent. Thus, the analysis of the emission spectra and fluorescence lifetimes yielded information on the localization of this probe molecule in suspensions of BSN and of the bare silica nanoparticles. The values of the equilibrium constant for the adsorption of the ground-state safranine-T on the particles were found to be (9.2+/-0.8)x10(4), (7.2+/-0.8)x10(5), and (3.0+/-0.1)x10(4) for the BSN in 1:1 acetonitrile:water, SiO2 in 1:1 acetonitrile:water, and SiO2 in acetonitrile, respectively.

Polysaccharide-based hydrogels: preparation, characterization, and drug interaction behaviour.

Oxidized alginate (ADA) and oxidized alginate blended with chitosan (ADA-Chit) were prepared in the presence of borax and CaCl 2, and their interactions with an antifolate drug, pyrimethamine (PYR), have been investigated. Tablets with a mean diameter of 1.2 +/- 0.06 cm were produced and drug interactions were performed in dimethyl sulfoxide (DMSO) using isothermal titration calorimetry (ITC). From ITC responses, the enthalpy changes of interaction PYR/materials, Delta int H, have been determined and were found to be -11.73 +/- 0.517 kJ mol (-1) for ADA and -4.86 +/- 0.156 kJ mol (-1) for ADA-Chit. The PYR encapsulation of approximately 75% was achieved for both materials, as measured by UV spectrometer.

A new generation of more pH stable reversed phases prepared by silanization of zirconized silica.

To further extend our studies in the search for reversed phases with enhanced durability at high pH, zirconized silica has now been explored as an alternative support. The synthesis of the new stationary phases involves silanization of a zirconium-modified silica support with a C(18) trifunctional silane, followed by endcapping. The chromatographic properties of the C(18) phases based on zirconized silica are similar to their titanized silica counterparts. Accelerated high pH stability tests, using phosphate mobile phases and elevated temperature, have shown that the zirconized silica phases have promising advantages not only over similarly prepared non-metalized phases but also over titanized silica C(18) phases.

Designed pendant chain covalently bonded to silica gel for cation removal.

The precursor 1,4-bis(3-aminopropyl)piperazine organofunctionalized silica gel reacted with methylacrylate to yield a new inorganic-organic chelating material, by adopting a heterogeneous and divergent synthetic approach. The synthesized materials were characterized through elemental analyses and spectroscopic techniques such as infrared, nuclear magnetic nuclei of carbon-13 and silicon-29. Due to the increment of basic centers attached to the pendant chains the metal adsorption capability of the final chelating material, was found to be higher than its precursor. The adsorption of metal ions from aqueous solution followed the order Cu(2+)>Ni(2+)>Co(2+). Both Langmuir and Freundlich models were found to be applicable for the adsorption of copper, with the equilibrium parameter value within zero to one. The competitive sorption behavior, with variation of pH, was favorable for the separation of copper from binary mixtures with nickel and cobalt. When sodium, potassium and magnesium cations are present in the medium little effects on adsorption were observed, thus suggesting that the synthesized material can be useful for removal of toxic/heavy metal ions from natural and wastewater systems.

Kinetics and modified clay thermodynamic from the Brazilian amazon region for lead removal.

Modified Brazilian smectite-bearing clay samples displayed ability for lead adsorption. The structure modification of smectite were obtained through pillaring process and functionalization with [3-(2-aminoethylamino)propyl]trimethoxysilane. The chemical modification process increases the basal spacing of the natural smectite from 1.354 to 2.364 nm. The Langmuir model was fitted to experimental data in linear regression. Kinetic studies showed an equilibrium adsorption time of 700 min on the modified clay. The experimental data were correlated with two distinct kinetic models were used: (i) external mass transfer diffusion and (ii) intraparticular mass transfer diffusion. However, the intraparticle mass transfer diffusion model gave a better fit to these experimental data. The energetic effects caused by lead interactions were determined through calorimetric titration at the solid-liquid interface and gave a net thermal effect that enabled the calculation of the exothermic values and the equilibrium constant.

Synthesized layered inorganic-organic magnesium organosilicate containing a disulfide moiety as a promising sorbent for cations removal.

A new-layered inorganic-organic magnesium organosilicate was synthesized through a single step template sol-gel route under mild conditions, using a new alkoxysilane, containing a 2-aminophenyldisulfide molecule. Elemental analysis data based on the nitrogen atom showed an incorporation of 1.97mmol of organic pendant groups for each gram of the hybrid formed. The X-ray diffraction patterns demonstrated that this nanocompound exhibited lamellar structure, in agreement with that found for natural inorganic silicates. Infrared spectroscopy and nuclear magnetic resonance for the (29)Si nucleus in the solid state are in agreement with the success of the proposed synthetic method. The presence of nitrogen and sulfur basic centers attached to the pendant groups inside the lamellar structure is used as basic centers to coordinate cations from aqueous solution at the solid/liquid interface. The isotherms were fitted to Langmuir and Freundlich models. The maxima adsorption capacities for copper, lead and cadmium, calculated from Langmuir model, were 3.28, 1.42 and 0.35mmol g(-1), respectively. These values are comparable to other adsorbing nanomaterials. This behavior suggested that this new inorganic-organic hybrid could be employed as a promising adsorbent for cation removal from polluted systems.

Adsorptive, thermodynamic and kinetic performances of Al/Ti and Al/Zr-pillared clays from the Brazilian Amazon region for zinc cation removal.

Smectite clay samples from the Amazon region, Brazil, were pillarized by intercalating the species obtained from the chemical reactions: (i) AlCl3.6H2O/NaOH, (ii) titanium ethoxide in hydrochloric acid and (iii) direct use of ZrOCl2.8H2O solution. The natural matrices and the pillaring solutions were maintained under vigorous stirring at 298 K for 3 h and then subjected to calcination at temperatures of 723 and 873 K. Natural and pillared matrices were characterized by XRD, FTIR, TG-DTG and nitrogen adsorption-desorption isotherms. The resulting materials were used for zinc adsorption from aqueous solution at room temperature. The Langmuir, Freundlich and Temkin adsorption isotherm models have been applied to fit the experimental data and the Freundlich model is limited for higher concentrations. The pillaring process increases the thermal stability, the basal spacing of the natural clay sample (A1) from 1.55 to 2.06 nm and the surface area from 44.30 to 223.73 m2 g(-1). Kinetic studies demonstrated an equilibrium time of 180 min for zinc adsorption on the pillared matrices. Pseudo-first-order, Lagergren pseudo-second-order and Elovich equations demonstrated a better agreement with second-order kinetics was obtained with K2=4.17-10.43 x 10(-3)g mg(-1)min(-1) for the A1 sample.

Application of Brazilian pine-fruit shell as a biosorbent to removal of reactive red 194 textile dye from aqueous solution kinetics and equilibrium study.

The Brazilian pine-fruit shell (Araucaria angustifolia) is a food residue, that was used as biosorbent for the removal of non-hydrolyzed reactive red 194 (NRR) and hydrolyzed reactive red 194 (HRR) forms from aqueous solutions. Chemical treatment of Brazilian pine-fruit shell (PW), with chromium (Cr-PW), with acid (A-PW), and with acid followed by chromium (Cr-A-PW) were also tested as alternative biosorbents for the removal of NRR and HRR from aqueous effluents. It was observed that the treatment of the Brazilian pine-fruit shell with chromium (Cr-PW and Cr-A-PW) leaded to a remarkable increase in the specific surface area and average porous volume of these biosorbents when compared to unmodified Brazilian pine-fruit shell (PW). The effects of shaking time, biosorbent dosage and pH on biosorption capacity were studied. In acidic pH region (pH 2.0) the biosorption of NRR and HRR were favorable. The contact time required to obtain the equilibrium was 24h at 25 degrees C. The equilibrium data were fitted to Langmuir, Freundlich, Sips and Redlich-Peterson isotherm models. For NRR reactive dye the equilibrium data were best fitted to the Sips isotherm model using PW and A-PW as biosorbents, and Redlich-Peterson isotherm model using Cr-PW and Cr-A-PW as biosorbents. For HRR reactive dye the equilibrium data were best fitted to the Sips isotherm model using PW, A-PW and Cr-A-PW and the Redlich-Peterson isotherm model for Cr-PW as biosorbent.

Mesoporous silica originating from a gaseous ammonia epoxide ring opening and the thermodynamic data on some divalent cation adsorptions.

An organofunctionalized mesoporous HMS-like compound has been synthesized by reacting the silylating agent 3-glycidoxypropyltrimethoxysilane with gaseous ammonia. The reaction path leads to the opening of the three membered epoxide ring to incorporate ammonia to give the modified silylating agent. This new silylating agent was used to synthesize a mesostructure inorganic-organic hybrid through the neutral template directing agent, dodecylamine, using a co-condensation process, and exploring the ability of the silicon source tetraethoxysilane. The final solid named HMS-NH has been characterized through elemental analysis, X-ray powder diffraction, nitrogen gas adsorption, infrared spectroscopy and solid state NMR for the 29Si nucleus. An amount of 1.06+/-0.10 mmol of pendant groups is covalently bonded to the inorganic backbone. The attached basic centers adsorbed divalent cations to give the maxima adsorption capacity of 0.74+/-0.03, 0.55+/-0.06, 0.53+/-0.05 and 0.51+/-0.06 mmolg(-1) for copper, nickel, zinc and cobalt, respectively. From calorimetric determinations the quantitative thermal effects for all these cation/basic center interactions gave exothermic enthalpy, negative Gibbs free energy and positive entropy. These thermodynamic data confirmed the energetically favorable condition of such interactions at the solid/liquid interface for all systems.

Amine bridges grafted mesoporous silica, as a prolonged/controlled drug release system for the enhanced therapeutic effect of short life drugs.

Hybrid mesoporous silica SBA-15, with surface incorporated cross-linked long hydrophobic organic bridges was synthesized using stepwise synthesis. The synthesized materials were characterized by elemental analysis, infrared spectroscopy, nuclear magnetic resonance spectroscopy, nitrogen adsorption, X-rays diffraction, thermogravimetry and scanning and transmission electron microscopy. The functionalized material showed highly ordered mesoporous network with a surface area of 629.0m2g-1. The incorporation of long hydrophobic amine chains on silica surface resulted in high drug loading capacity (21% Mass/Mass) and prolonged release of ibuprofen up till 75.5h. The preliminary investigations suggests that the synthesized materials could be proposed as controlled release devices to prolong the therapeutic effect of short life drugs such as ibuprofen to increase its efficacy and to reduce frequent dosage.

Influence of the TiO2 content on the chromatographic performance and high pH stability of C18 titanized phases.

To extend pH stability, protective metal oxide layers, such as titanium oxide, that are more stable in alkaline medium, can be chemically bonded to the chromatographic silica surface prior to reaction with silanes. In the present work, the influence of the titanium oxide content on the chromatographic performance was investigated by synthesizing a C18 phase onto a doubly-titanized silica support and comparing its chromatographic performance with a C18 phase on singly-titanized silica. The Engelhardt and Tanaka test mixtures were used for chromatographic characterizations using short HPLC columns. The column lifetimes of these titanized phases were also compared by performing accelerated aging tests at 50 degrees C using aggressive phosphate mobile phases at pH 10.

Preparation of ethylenediamine-anchored cellulose and determination of thermochemical data for the interaction between cations and basic centers at the solid/liquid interface.

Cellulose was first modified with thionyl chloride, giving 99% substitution at C6, and then reacted with ethylene-1,2-diamine to produce 6-(2'-aminoethylamino)-6-deoxy-cellulose. From the 8.5% of nitrogen incorporated in the polysaccharide backbone, the amount of ethylene-1,2-diamine anchored per gram of modified cellulose was determined to be 3.03+/-0.01mmol. This chemically immobilized surface was characterized by FTIR, TG, (13)C NMR, and SEM techniques. The available basic nitrogen centers covalently bonded to the biopolymer skeleton were studied for copper, cobalt, nickel, and zinc adsorption from aqueous solutions and the respective thermal adsorption effects were determined by calorimetric titration. The ability to adsorb cations gave a capacity order of Co(2+)>Cu(2+)>Zn(2+)>Ni(2+) with affinities of 1.91+/-0.07, 1.32+/-0.07, 1.31+/-0.02, and 1.08+/-0.04mmol/g, respectively. The net thermal effects obtained from calorimetric titration measurements were adjusted to a modified Langmuir equation and the enthalpy of the interaction was calculated to give the following exothermic values: -20.8+/-0.05, -11.72+/-0.03, -7.32+/-0.01, and -6.27+/-0.02kJ/mol for Co(2+), Cu(2+), Zn(2+), and Ni(2+), respectively. With the exception of the entropic value for copper, the other thermodynamic data for these systems are favorable for cation adsorption from aqueous solutions at the solid/liquid interface, suggesting the use of this anchored biopolymer for cation removal from the environment.

Some features associated with organosilane groups grafted by the sol-gel process onto synthetic talc-like phyllosilicate.

Two new lamellar inorganic-organic magnesium silicates have been successfully synthesized by using sol-gel based processes under mild temperature conditions. The talc-organosilicates derived using two silylating agents as the silicon source, (i) 3-chloropropyltrimethoxysilane, and (ii) from the attachment of 5-amino-1,3,4-thiadiazole-2-thiol molecule to this precursor agent, yielded PhMg-Cl and PhMg-Tz phyllosilicates. These organoclays were characterized through elemental analyses, infrared spectroscopy, X-ray diffractometry, surface area, thermogravimetry, and carbon and silicon solid state nuclear magnetic resonance spectroscopy. The results confirmed the presence of organic moieties covalently bonded to the inorganic silicon sheet network of the 2:1 class of phyllosilicates, with a density of organic molecules of 6.6+/-0.1 and 2.7+/-0.2 mmol g(-1) anchored on the inorganic layer and with interlayer distances of 1158 and 1628 pm, respectively. The nuclear magnetic resonances results in the solid state are in agreement with the sequence of carbons distributed in the pendant chains of the original silylating agents and the silicon bonded to oxygen atoms or carbon atoms of the inorganic sheets, as expected for the organically functionalized phyllosilicates. The enhanced potential of the new compound PhMg-Tz as a multi property material was explored in adsorbing cations from aqueous solution. The basic sulfur and nitrogen centers attached to the pendant chains inside the lamellar cavity can coordinate mercury, by presenting an isotherm saturated at 0.19 mmol g(-1) of this heavy metal. The functionality of this organoclay-like material expresses its potential for heavy cation removal from an ecosystem.

Hydroxyapatite organofunctionalized with silylating agents to heavy cation removal.

Hydroxyapatite surface silylation with organosilane derivatives (H3CO)3SiR, R being the corresponding organic moieties CH2CH2CH2NH2, CH2CH2CH2NHCH2CH2NH2, and CH2CH2CH2NHCH2CH2NHCH2CH2NH2, was carried out to yield organofunctionalized nanomaterials, named HApR1, HApR2, and HApR3, respectively. The products were characterized by elemental analysis, infrared spectroscopy, X-ray diffraction, thermogravimetry, and (1P and 13C NMR in the solid state. The amounts of groups grafted onto surfaces were 0.75+/-0.05, 2.35+/-0.14, and 2.48+/-0.18 mmolg(-1) for HApRx (x=1,2,3) surfaces, respectively. Linear correlations between elemental analysis, mass loss, (31)P chemical shift data, and the characteristics of the chain of each alkoxysilane were observed. The organic basic centers distributed onto the external surface have the ability to adsorb divalent copper and cobalt cations from aqueous solution. The degree of adsorption obtained from batchwise processes showed the best performance of these synthesized nanomaterials when compared with the pristine hydroxyapatite.

Use of Ponkan mandarin peels as biosorbent for toxic metals uptake from aqueous solutions.

Waste Ponkan mandarin (Citrus reticulata) peel was used as biosorbent to extract Ni(II), Co(II) and Cu(II) from aqueous solutions at room temperature. To achieve the best adsorption conditions the influence of pH and contact time were investigated. The isotherms of adsorption were fitted to the Langmuir equation. Based on the capacity of adsorption of the natural biosorbent to interact with the metallic ions, the following results were obtained 1.92, 1.37 and 1.31 mmol g(-1) for Ni(II), Co(II) and Cu(II), respectively, reflecting a maximum adsorption order of Ni(II)>Co(II)>Cu(II). The quick adsorption process reached the equilibrium before 5, 10 and 15 min for Ni(II), Co(II) and Cu(II), respectively, with maximum adsorptions at pH 4.8. In order to evaluate the Ponkan mandarin peel a biosorbent in dynamic system, a glass column was fulfilled with 1.00 g of this natural adsorbent, and it was fed with 5.00 x 10(-4)mol l(-1) of Ni(II) or Co(II) or Cu(II) at pH 4.8 and 3.5 ml min(-1). The lower breakpoints (BP(1)) were attained at concentrations of effluent of the column attained the maximum limit allowed of these elements in waters (>0.1 mg l(-1)) which were: 110, 100 and 130 bed volumes (V(effluent)/V(adsorbent)), for Ni(II), Co(II) and Cu(II), respectively. The higher breakpoints (BP(2)) were attained when the complete saturation of the natural adsorbent occurred, and the values obtained were: 740, 540 and 520 bed volumes for Ni(II), Co(II) and Cu(II), respectively.