Adsorção de fenol sobre carvão ativado em meio alcalino

The present study describes phenol adsorption on commercial active carbon (CAF) under alkaline conditions in the concentration range of 0.01 to 2.08 mmol L-1. Surface characterization has been performed by means of surface area measurements, IR spectroscopy and Boehm titration. The effect of temperature on the adsorption equilibrium isotherm was investigated at 23, 30, 40, 50 and 60 °C. The results showed that adsorption capacity decreased with increasing temperature. The adsorption kinetics and the role of surface characteristics on the adsorption of phenol also discussed.

Aplicação de adsorção para remover amônia de efluentes suinícolas pré-tratados

The aim of this work is to evaluate the use of natural zeolites to remove the NH4+ that remains in effluents from swine facilities which were submitted to physico-chemical and biological treatments. Experiments were made in batch made adding 5% (w/w) of adsorbent (0.6-1.3 and 3.0-8.0 mm) to synthetic and real swine facilities effluents. The results show that ammonium removal is influenced by adsorbent particle size and the presence of other ions in the effluent. The adsorption equilibrium was described by Langmuir as well as Freundlich isotherms and the kinetic data fitted well a pseudo-second order model.

Adsorção competitiva de inibidor de corrosão usado em poços de perfuração de petróleo sobre aço, esmectita e arenito

A commercial corrosion inhibitor used in petroleum production was characterized by means of infrared spectroscopy and energy dispersive spectroscopy (EDS). Predicting the adsorption behavior of corrosion inhibitor onto steel, sandstone and esmectite is the key to improve working conditions. In this study, the adsorption kinetics of inhibitor formulations in HCl 15% or in Mud Acid (HCl 13,5% and ammonium bifluoride) onto steel, sandstone and esmectite was determined by means of spectrophotometry. Kinetic parameters indicated that adsorption of inhibitor in the presence of bifluoride was favored. Moreover, the adsorption constant rate was the largest when the substrate was esmectite.

Elimination of dyes from aqueous solutions using iron oxides and chitosan as adsorbents: a comparative study

This work investigates the adsorption of Alizarin, Eriochrome Blue Black R and Fluorescein using chitosan, goethite and magnetite as adsorbents. For Alizarin, the best adsorbent is chitosan with a Langmuir parameter of 15.8 mmol dye/g adsorbent. For Eriochrome Blue Black R only 1.94 mmol dye/g chitosan is adsorbed. Langmuir parameters for the Alizarin adsorption on both iron oxides display one or two orders of magnitude lower than for chitosan and two orders of magnitude lower in the case of Eriochrome Blue Black R. Fluorescein does not adsorb in appreciable amounts on chitosan and it presents the lower affinity on the iron oxides.

Remoção de metais de solução aquosa usando bagaço de caju

The metal ions removal on cashew bagasse, a low-cost material, has been studied by batch adsorption. The parameters chemical treatment, particle size, biosorbent concentration, and initial pH were studied. In this study the maximum ions removal was obtained on the cashew bagasse treated with 0.1 mol/L NaOH/3 h, at optimum particle size (20-59 mesh), biosorbent concentration (50 g/L) and initial solution pH 5. The kinetic study indicated that the adsorption metal follows pseudo-second order model for a multielementary system and equilibrium time was achieved in 60 min for all metal ions.

Removal of copper(II) from sugar-cane spirits employing chitosan

A method employing chitosan as complexant agent in the removal of copper(II) ions generally present in the Brazilian cachaça samples is herein proposed. The efficiency of this method is attributed to its high capacity of metal cations adsorption, mainly due to presence of hydroxyl and amine groups that can serve as chelating sites. The removal of copper(II) ions from this alcoholic beverage was efficient employing either in column and batch system. The analysis were carried out employing the flame atomic absorption spectrometry and the remaining copper(II) concentrations in the treated cachaça were lower than LOD of FAAS technique.

Adsorption of glyphosate in a forest soil: a study using Mössbauer and FT-IR spectroscopy

We studied the adsorption of glyphosate (GPS) onto soil mineral particles, using FT-IR and Mössbauer spectroscopy. From IR measurements for samples collected under native vegetation of a forest reserve, bands at 1632 and 1407 cm-1 could be attributed to the interaction between the carboxylic group of GPS and structural Al3+ and Fe3+ on the surface of mineral particles; bands at 1075 and 1000 cm-1 were observed only for cultivated soil. Mössbauer spectra for these soils were definitely fitted using a broad central doublet in addition to the magnetic component. This multiple quadrupolar component may be attributed to all non-magnetic Fe3+ contributions, including that of the GPS/Fe3+ complex.

Rejeito de mineração de carvão como adsorvente para remoção da acidez, Fe (III), Al (III) e Mn (II) em drenagem ácida

This study aimed the use of coal mining waste as a new adsorbent for H3O+ and removal of Al (III), Fe (III) and Mn (II) from acid mine drainage. Data from kinetic and equilibrium of the adsorption of H3O+ followed the pseudo second-order and Langmuir isotherm models. The maximum adsorption capacity of H3O+ was 316 mmol kg-1. The adsorbent removed 100% of Al (III), 100% of Fe (III) and 89% of Mn (II), suggesting its use as an alternative for the treatment of acid mine drainage.

Adsorção de chumbo, cádmio e prata em óxido de nióbio (V) hidratado preparado pelo método da precipitação em solução homogênea

This paper describes the adsorption of heavy metals ions from aqueous solution by hydrous niobium oxide. Three heavy metals were selected for this study: cadmium, lead and silver. Adsorption isotherms were well fitted by Langmuir model. Maximum adsorption capacity (Q0) for Pb2 +, Ag+ and Cd2 + was found to be 452.5, 188.68 and 8.85 mg g-1, respectively.

Adsorção de arsênio(V) pelo compósito magnético hidrotalcita: óxido de ferro

In this work, hydrotalcite, a layered double hydroxide, had its adsorption and ion exchange properties combined with the magnetic properties of iron oxide to produce a magnetic adsorbent, HT-Fe. The removal of As(V) by a HT-Fe adsorbent was evaluated under various conditions. The Kinetic process was well described by a pseudo-second order rate model. The maximum adsorption capacity, calculated with the Langmuir model showed to be dependent on pH, reaching values of 24.09, 10.19 and 7.44 mg g-1, respectively, for pH values of 4.0, 7.0 and 9.0. The inhibition by competition of anions is dependent on the type of ionic species.

Caracterización de la biomasa inactiva de Aspergillus niger O-5 como sorbente de Pb (II)

The inactive biomass of fungus Aspergillus niger O-5 obtained in Cuba was characterized as sorbent of Pb2+ by several structural analysis and others techniques. In addition, the biomass was studied for the separation / preconcentration of Pb2+ from aqueous solution. The maximum biosorption capacity was obtained for the contact time of 30 min and pH 5. The kinetic of sorption process occurred according to the model of Ho. The Freundlich or Langmuir models suitably described the experimental adsorption isotherms. The biomass can be used as sorbent for Pb2+ with a maximum capacity of 4.7 - 6.2 mg g-1. The pretreatment with NaOH solution improved its sorption capacity.

Validation of a spectrophotometric method to estimate the adsorption on nanoemulsions of an antimalarial oligonucleotide

This study describes the validation of a spectrophotometric method to estimate oligonucleotides association with cationic nanoemulsions. Phosphodiester and phosphorothioate oligonucleotides targeting Plasmodium falciparum topoisomerase II were analyzed at 262 nm. Linear response (r > 0.998) was observed from 0.4 to 1.0 nmol/mL, the relative standard deviation values for the intra- and inter-days precision were lower than 2.6% and the recovery ranged from 98.8 to 103.6% for both oligonucleotides. The association efficiency was estimated based on an ultrafiltration/centrifugation method. Oligonucleotides recovery through 30 kDa-membranes was higher than 92%. The extent of oligonucleotides association (42 to 98%) varied with the composition of nanoemulsions

Evaluation of pesticide adsorption in gas chromatographic injector and column

Components in complex matrices can cause variations in chromatographic response during analysis of pesticides by gas chromatography. These variations are related to the competition between analytes and matrix components for adsorption sites in the chromatographic system. The capacity of the pesticides chlorpyrifos and deltamethrin to be adsorbed in the injector and chromatographic column was evaluated by constructing three isotherms and changing the column heating rate to 10 and 30 ºC min-1. By using ANCOVA to compare the slope of calibration graphs, results showed that the higher the injector temperature (310 ºC) the lower the pesticide adsorption. Also, deltamethrin influenced the adsorption of chlorpyrifos on the column chromatographic.

Determinação dos parâmetros cinéticos e termodinâmicos da adsorção de L-cisteína em ouro por meio da técnica de microbalança a cristal de quartzo

This article discusses the adsorption kinetics of a L-cysteine monolayer onto a gold surface by means of information obtained through the QCM technique. The results indicate that the adsorption process is rapid and follows the Langmuir isotherm, in which adsorption and desorption are considered. From these measurements the following parameter values were obtained: k d = (4.2 ± 0.4) x 10-3 s-1, k a = 75 ± 6 M-1 s-1, Keq=(1.8 ± 0.3) x 10(4) M-1 and ΔGads = - (5.8 ± 0.2) kcal mol-1.

Avaliação do processo adsortivo utilizando mesocarpo de coco verde para remoção do corante cinza reativo BF-2R

This work used green coconut mesocarp as a bioadsorbent to remove Reactive Gray BF-2R dye. A 2³ factorial design was used to evaluate the influence of the variables adsorbent mass, particle size and stirring speed on the adsorptive process. Kinetic and adsorption equilibrium studies were performed. Results showed that the kinetic equilibrium was reached after 150 min. Using the Langmuir model, a q max of 21.9 mg g-1 and k of 0.30 L g-1 was obtained. The mesocarp of coconut, a residue of agribusiness, proved to be an effective alternative technique for the removal of dye in this study.