Adsorption of amyloglucosidase from Aspergillus niger NRRL 3122 using ion exchange resin

Amyloglucosidase enzyme was produced by Aspergillus niger NRRL 3122 from solid-state fermentation, using deffated rice bran as substrate. The effects of process parameters (pH, temperature) in the equilibrium partition coefficient for the system amyloglucosidase - resin DEAE-cellulose were investigated, aiming at obtaining the optimum conditions for a subsequent purification process. The highest partition coefficients were obtained using 0.025M Tris-HCl buffer, pH 8.0 and 25ºC. The conditions that supplied the highest partition coefficient were specified, the isotherm that better described the amyloglucosidase process of adsorption obtained. It was observed that the adsorption could be well described by Langmuir equation and the values of Qm and Kd estimated at 133.0 U mL-1 and 15.4 U mL-1, respectively. From the adjustment of the kinetic curves using the fourth-order Runge-Kutta algorithm, the adsorption (k1) and desorption (k2) constants were obtained through optimization by the least square procedure, and the values calculated were 2.4x10-3 mL U-1 min-1 for k1 and 0.037 min-1 for k2 .

Adsorption characteristics of carbonized bark for phenol and pentachlorophenol

The potential of using carbonized slash pine bark as a substitute for activated carbon was examined in this study. The bark was carbonized by slow heating in nitrogen for 6.5 h to 672 degrees C. The BET-N-2 surface area, average micropore and mesopore diameter, and micropore volume were 332 m(2) g(-1) 21.7 Angstrom, and 0.125 cm(3) g(-1), respectively. The adsorption capacities for phenol and pentachlorophenol (PCP) at pH 2 and pH 8 were evaluated. The Langmuir equation provided a slightly better fit than the Freundlich equation to two sets of phenol data. The calculated Freundlich constants, K = 0.41 - 0.58 mmol/g/(mmol dm(-3))(1/n) and 1/n = 0.30 - 0.41, were lower and higher, respectively, than literature values for activated carbons. The adsorption capacity of the carbonized bark was much lower for PCP than for phenol. The protonated and anionic PCP isotherms were Type II or III, respectively, in the Brunauer classification. The BET equation provided the best fit to protonated PCP isotherm data. The anionic PCP data were fitted to both the BET model and an equation used in the literature to represent phosphate adsorption on activated carbons. Nonlinear regression of the data for both phenol and PCP adsorption with the Freundlich, Langmuir and BET equations generally gave more accurate parameters, compared with the use of linearized equations to obtain the parameters. (C) 1998 SCI.

Comparison of adsorption capacity of p-Cresol & p-Nitrophenol by activated carbon in single and double solute

Adsorption of p-Cresol and p-Nitrophenol by untreated activated carbon in single and multisolute solutions was carried out at 301 K and at controlled pH conditions. In acidic conditions, well below the pK(a) of both solutes, it was observed that the adsorbate solubility and the electron density of aromatic rings influenced the extent of adsorption by affecting the extent of London dispersion forces. The fitted parameters obtained from single-solute Langmuir equation show that Q(max) and the adsorption affinity of carbon for the compound with low pK(a) decrease more significantly. In higher solution pH conditions, on the other hand, it was found that electrostatic forces played a significant role on the extent of adsorption. The presence of another compound decreases Q(max) and the adsorption affinity of carbon for the principal compound. The effect of pH, on the carbon surface and on the solute molecules, must be considered. Adsorption of the solute at higher pH values was found to be dependent on the concentration of anionic form of the solute. The isotherm data were fitted to the Langmuir isotherm equation for both single and double solute solutions.

Parâmetros termodinâmicos da reação de adsorção de boro em solos tropicais altamente intemperizados

The driving force of boron adsorption on some tropical soils was evaluated by means of thermodynamic parameters. The batch method was employed, and the reaction was monitored at different pH values. The Langmuir equation successfully fitted the experimental results and provided reasonable isotherm parameters. Boron adsorption increased as a function of the pH of the soil solution and the concentration of added boron. The reaction was favorable and proceeded spontaneously, being strongly exoergic, as indicated by a negative free energy (deltaG) and a separation factor (K R) < 1. The boron adsorption phenomenon and the soil-solution interface were thermodinamically described using a theoretical model.

Quimissorção de cátions divalentes em sílica gel modificada com ácido tioglicólico: a influência do pH e força iônica

A novel type of heavy metal adsorbent was prepared by the covalent grafting of thioglycolic acid molecules on a silica gel surface previsiouly modified with 3-aminopropyltrimethoxysilane. The amount of thioglycolic acid immobilized was 1.03 mmol per gram of silica. This material displayed a chelating moiety containing nitrogen, sulfur, and oxygen basic centers which are potentially capable of extracting from aqueous solutions cations such as Cu(II), Ni(II), Co(II), influenced by pH and ionic strength. This process of extraction was carried out by the batch method when similar chemisorption isotherms were observed for all cations. A modified Langmuir equation describes the experimental data.

Adsorção do corante reativo laranja 16 de soluções aquosas por zeólita sintética

Coal fly ash, a waste generated in a coal-fired electric power plant, was used to synthesize zeolite by hydrothermal treatment with NaOH solution. This zeolite was used as adsorbent to investigate the adsorption kinetics and isotherm parameters of the reactive orange 16 (RO16) dye from aqueous solutions at different concentrations (1.3-15.4 mg L-1). Three kinetic models, the pseudo-first-order, second-order, and intraparticle diffusion were used to predict the adsorption rate constants. The kinetics of adsorption of the RO16 dye followed pseudo-second-order kinetics. The adsorption isotherm data were closely fitted to the Langmuir equation. Keywords: coal fly ash; zeolite; reactive dye adsorption.

Remoção de íons Zn2+, Cd2+ e Pb2+ de soluções aquosas usando compósito magnético de zeólita de cinzas de carvão

For this study, magnetic composite of zeolite-magnetite was prepared by mixing magnetite nanoparticles suspension with synthetic zeolite. The nanoparticles in suspension were synthesized by precipitating iron ions in a NaOH solution. The zeolite was synthesized from coal fly ash by alkaline hydrothermal treatment. The magnetic composite was characterized by XDR, SEM, magnetization measurements, IR, and BET surface area. Batch tests were carried out to investigate the adsorption of metal ions of Zn2+, Cd2+ and Pb2+ from aqueous solution onto magnetic composite. Adsorption isotherms were analyzed using Freundlich and Langmuir equations. The adsorption equilibrium data fitted well to the Langmuir equation with maximum adsorption capacities in the range of 28.5-127 mg g-1.

Assessment of the effect of time and temperature on the availability of residual phosphate in a glasshouse study of four soils using the Olsen method

The Olsen method is an indicator of plant-available phosphorus (P). The effect of time and temperature on residual phosphate in soils was measured using the Olsen method in a pot experiment. Four soils were investigated: two from Pakistan and one each from England (calcareous) and Colombia (acidic). Two levels of residual phosphate were developed in each soil after addition of phosphate by incubation at either 10degreesC or 45degreesC. The amount of phosphate added was based on the P maximum of each soil, calculated using the Langmuir equation. Rvegrass was used as the test crop. The pooled data for the four soils incubated at 10degreesC showed good correlation between Olsen P and dry matter yield or P uptake (r(2) = 0.85 and 0.77, respectively), whereas at 45 degreesC, each soil had its own relationship and pooled data did not show correlation of Olsen P with dry matter yield or P uptake. When the data at both temperatures were pooled, Olsen P was a good indicator of yield and uptake for the English soil. For the Pakistani soils, Olsen P after 45 degreesC treatment was an underestimate relative to the 10 degreesC data and for the Colombian soil it was an overestimate. The reasons for these differences need to be explored further before high temperature incubation can be used to simulate long-term changes in the field.

Biosorption of Cr(III) using in natura and chemically treated tropical peats

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Adsorção de selênio em latossolos

A retenção de Se pelos colóides do solo constitui importante processo para a manutenção da sanidade ambiental. A informação sobre a adsorção de Se em solos altamente intemperizados é restrita e existem poucos padrões quantitativos disponíveis para a definição de estratégias de remediação de áreas contaminadas. Quantidades crescentes de Se (5, 10, 25, 50, 100 e 250 mg L-1), na forma de Na2SeO3, foram adicionadas a amostras de dez Latossolos brasileiros [três Latossolos Vermelho-Amarelos (LVA-1, LVA-2 e LVA-3), dois Latossolos Vermelhos (LV-1 e LV-2), um Latossolo Vermelho eutroférrico (LVef), um Latossolo Vermelho acriférrico (LVwf), dois Latossolos Amarelos (LA-1 e LA-2) e um Latossolo Amarelo acriférrico (LAwf)]. Isotermas de adsorção foram construídas e foi verificado o ajuste dos resultados experimentais aos modelos de Langmuir e de Freundlich. A equação de Langmuir ajustou melhor os resultados de adsorção de Se do que a isoterma de Freundlich. Todas as isotermas apresentaram o formato tipo-L (exponencial), com exceção daquelas obtidas para o LVA-1 e para o LVA-2, que apresentaram comportamento tipo-C (linear). Valores de adsorção máxima (Ads máx), estimada pelo modelo de Langmuir, variaram de 135 (LVA-3) a 2.245 mg kg-1 (LA-1), enquanto os coeficientes de afinidade (K L) estiveram entre 0,002 (LVA-2) e 0,326 (LVA-3). A constante de afinidade estimada pelo modelo de Freundlich (Kf) variou de 13,7 (LVA-2) a 180,1 (LAwf). A adsorção máxima de Se foi mais elevada no LVef e nos Latossolos ácricos (LAwf e LVwf), enquanto os maiores valores de Kf foram encontrados no LV-2, LVef, LVA-3 e LVwf. Não houve correlação entre os atributos dos solos e as constantes de Langmuir. Valores de Kf correlacionaram-se com os teores de argila (r = 0,42*) e com a capacidade de troca de ânions (r = 0,64*).

Adsorção do corante amarelo reativo BF-4G 200% por argila esmectita

This study aimed to evaluate the potential use of smectite clays for color removal of textile effluents. The experiments were performed by testing exploratory/planning method factorial and fractional factorial where the factors and levels are predetermined. The smectite clays were used originating from gypsum hub of the region Araripe-PE, and the dye used was Reactive Yellow BF-4G 200%. The smectite clay was collected and transported to the Laboratory of Soil Physics of UFRPE, where it held its preparation through air drying, lump breaking and classification in sieve to then submit it to the adsorption process. Upon completion of 22 complete factorial design it was concluded that the values of (96, 96,5 and 95,8%) corresponding to the percentage of of removal for "in-kind", chemically and thermally activated, respectively and adsorbed amounts of (4,80, 4,61 and 4,74 mg/g) for three clays. Showed that the activation processes used did not increase the adsorption capacity of smectite clay. The kinetic data were best fitted to the Freundlich isotherm, with an exponential distribution of active sites and that shows above the Langmuir equation for adsorption of cations and anions by clays. The kinetic model that best adapted to the results was the pseudosecond order model. In the factorial design study 24-1, at concentrations up to 500 mg/L obtains high percentage of color removal (92,37, 90,92 and 93,40%) and adsorbed amount (230,94, 227,31 and 233,50 mg/g) for three clays. The kinetic data fitted well to Langmuir and Freundlich isotherms. The kinetic model that best adapted to the results was the pseudosecond order model

Hexagonal mesoporous silica modified with 2-mercaptothiazoline for removing mercury from water solution

A method for the attachment of 2-mercaptothiazoline (MTZ) to modified silica gel has been developed. In the first step, a new silylant agent was synthesized, named SiMTZ, by the reaction between MTZ molecule and chloropropyltrimethoxysilane (SiCl). SiMTZ and tetraethylortosilicate were co-condensed in the presence of n-dodecylamine, a neutral surfactant template, to produce a modified ordered hexagonal mesoporous silica named HMTZ. The modified material contained 0.89 +/- 0.03 mmol of 2-mercaptothiazoline per gram of silica. FT-IR, FT-Raman, Si-29- and C-13-NMR spectra were in agreement with the proposed structure of the modified mesoporous silica in the solid state. HMTZ material has been used for divalent mercury adsorption from aqueous solution at 298 I K. The series of adsorption isotherms were adjusted to a modified Langmuir equation. The maximum number of moles of mercury adsorbed gave 2.34 +/- 0.09 mmol/g of material. The same interaction was followed by calorimetric titration on an isoperibol calorimeter. The HMTZ presented a high capacity for the removal of the contaminant mercury from water. The Delta H and Delta G values for the interaction were determined to be -56.34 +/- 1.07 and -2.14 +/- 0.11 kJ mol(-1). This interaction process was accompanied by a decrease of entropy value (- 182 J mol(-1) K-1). Thus, the interaction between mercury and HMTZ resulted in a spontaneous thermodynamic system with a high favorable exothermic enthalpic effect. (c) 2007 Elsevier B.V. All rights reserved.

4-amine-2-mercaptopyrimidine modified silica gel applied in Cd(II) and Pb(II) extraction from an aqueous medium

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Preconcentration and determination of Cu(II) in a fresh water sample using modified silica gel as a solid-phase extraction adsorbent

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Estudo do equilíbrio e cinética de adsorção de um corante aniônico em quitosana

The phenomenon of adsorption is of fundamental importance for the treatment of textile effluents and removal of dyes. Chitosan is characterized as an excellent adsorbent material, not only for its adsorption capacity but also the low cost production. Equilibrium and kinetic studies were developed in this study to describe the mechanism of adsorption of the anionic azo dye Orange G in chitosan, with the isotherms obtained from the variation of the concentration of dye in the continuous phase. The kinetics of the process was analyzed based on models involving the adsorption of molecules of the dye in nonpolar and polar sites. Adsorption experiments were carried out in water and in saline media with different NaCl concentrations, both for the determination of the equilibrium time as isotherms for making kinetic curves in which the amount of dye adsorbed measured indirectly varied with time. The experiments revealed the opening of the biopolymer structure with increasing concentration of Orange G, accompanied by high pH values and change on the type of interaction between the dye and the adsorbent surface, suggesting behavior advocated by the Langmuir equation in a certain range of concentration of the adsorbate and following the Henry's Law at higher concentrations, from the increased number of sites available for adsorption. The studies conducted showed that the saline medium reduces the chitosan s adsorption capacity according to a certain concentration, the occurrence of the cooperative adsorption process steps kinetic mechanism suggested as a new alternative for the interpretation of the phenomenon