Melissa Gurgel Adeodato Vieira

Sorption kinetics and equilibrium for the removal of nickel ions from aqueous phase on calcined Bofe bentonite clay.

In this paper the kinetics and dynamics of nickel adsorption on calcined Bofe bentonite clay were studied. The clay was characterized through EDX, surface area (BET) and XRD analysis. The influence of parameters (pH, amount of adsorbent, adsorbate concentration and temperature) was investigated. Kinetic models were evaluated in order to identify potential adsorption process mechanisms. The Langmuir and Freundlich models were utilized for the analysis of adsorption equilibrium. Thermodynamic parameters were assessed as a function of the process temperature. The kinetics data were better represented by the second-order model. The process was found to be strongly influenced by the factors studied. The Bofe clay removed nickel with maximum adsorption capacity of 1.91 mg metal/g of clay (20 degrees C; pH 5.3) and that the thermodynamic data indicated that the adsorption reaction is spontaneous and of an exothermal nature. The Langmuir model provided the best fit for sorption isotherms.

Removal of nickel on Bofe bentonite calcined clay in porous bed.

Bentonite clays have been showing good adsorbing characteristics and are used as an alternative material in the removal of heavy metals. The purpose of this study is to evaluate the removal of nickel on Bofe bentonite calcined clay in porous bed. Firstly, a study was conducted to define the operation outflow, based on the minimum mass transfer zone (MTZ) obtained, useful (q(U)) and total adsorbed (q(T)) removal amounts and total nickel removal percentage (Rem (%)). Assays of nickel adsorption on clay were conducted according to a 2(2) factorial design with three central points to evaluate the effect of the particle diameter and initial adsorbate concentration on variables q(U), q(T) and Rem (%). Tests to obtain the adsorbent physical and chemical characteristics were performed on samples of Bofe clay in natura, calcined, and calcined submitted to nickel adsorption. This clay was characterized according to the following techniques: Energy Dispersive Spectroscopy (EDS), Thermogravimetry (TG), Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), Fourier Transformed Infrared Spectroscopy (FTIR), Physisorption of N(2) (BET), Helium Picnometry and Scanning Electron Microscope (SEM) with metal mapping.

Characterization and use of in natura and calcined rice husks for biosorption of heavy metals ions from aqueous effluents

Heavy metal removal by adsorption using rice husks as a bioadsorbent was evaluated as an alternative for wastewater treatment. Batch equilibrium experiments and kinetic sorption studies were performed using monocomponent solutions of Ni(II), Cd(II), Zn(II), Pb(II) and Cu(II) in surface samples of in natura(RH) and calcined rice husks (RHA). RHA showed higher potential for removing lead and copper. Experimental data for adsorption isotherms of lead and copper were adjusted by Langmuir, Freundlich and Dubinin-Radushkevick (D-R) models, being better represented by the Langmuir model. The calcination of RH increased its surface area, improving its adsorption properties. From a morphological analysis obtained by SEM and diffraction patterns (XRD), a longitudinal fibrous and amorphous structure was observed for RH. TGA resultsindicated a total mass loss of around 60% for RH and 24.5% for RHA.

Removal of Cadmium(II) and Lead(II) ions from aqueous phase on sodic bentonite

before and after chemical modification and thermal activation was characterized by different techniques including X-ray diffraction, thermal analysis, Fourier transform infrared, surface area, helium pycnometry, cation exchange capacity and scanning electron microscopy. Pseudo-first order, pseudo-second order and intra-particle diffusion models were used to analyze the kinetic curves. Equilibrium data were analyzed using Langmuir and Freundlich models. The thermodynamic study indicated that lead adsorption process is endothermic and interactions between clays and solutions of lead occurred spontaneously, while cadmium adsorption revealed an exothermic and spontaneous nature. The maximum removal efficiencies were 97.62% for Cd(II) using

Adhesion of an Aqueous Polymeric Suspension to Inert Particles in a Spouted Bed

Abstract Among the several unit operations that seek the modification of superficial characteristics of solid particles, the spouted bed appears as efficient technology for coating of coarse particles (d p >1 mm). This work aimed at investigating the fluid-dynamics of the conventional spouted bed during a coating process, using several inert particles such as polystyrene, polypropylene, polyethylene of low density, ABS®, placebo tablet and glass beads, and analyze the influence of the physical properties of the particles and of the polymeric coating suspension on the fluid dynamics. The suspension was characterized by the surface tension, density, rheology, and contact angle between the suspension and the solid surface. It was verified that the particles having a high contact angle with the suspension (polystyrene, polypropylene, and low-density polyethylene) were not coated, and drying of the suspension was obtained in these cases. For the other particles (ABS, tablet, and glass beads), coating efficiencies in the range of 76–90% were obtained. The shape, angle of repose, and density of particles affected the fluid-dynamic during the coating, and also the inter-particle friction and the particle circulation velocity in the bed.

Energy Efficiency and Drying Kinetics of Recycled Paper Pulp

In this work, the influences of the air temperature and velocity on the drying kinetics of recycled paper pulp were analyzed. The increase of both variables positively influences the process, concerning the final moisture content and the drying time. However, optical microscopy and visual observation showed worse quality of the paper for drying conditions of high air temperature and velocity, presenting less uniformity and overdried surfaces. The dryer energy efficiency was evaluated by performance parameters and the results were compared with the ones obtained for other types of industrial paper dryers, presenting good agreement.

Synthesis and application of natural polymeric plasticizer obtained through polyesterification of rice fatty acid

This study includes the synthesis of a new natural plasticizer obtained through esterification reaction of rice fatty acid and polyols, its physicochemical characterization and its preliminary application in polyvinyl chloride (PVC). Monopropylene glycol, octanol and diethylene glycol were used as polyols for esterification reaction. Catalyst Fascat ® 4100, was also added. Viscosity, acidity and hydroxyl index, moisture content, molar mass, chemical composition (by FTIR) and color were determined to characterize the natural plasticizer synthesized. The results were compared with a commercial plasticizer (DOA: di-octyl adipate) derived from petrochemical source and synthesized in laboratory. According to the results, except from color, the natural plasticizer presented similar properties of commercially available plasticizers, such as DOA. Mechanical tests indicated that the addition of the natural plasticizer to PVC films resulted in a significant increase on its elongation at break (371.2%) compared to pure PVC film, indicating a possible application for this plasticizer.

Equilibrium and Thermodynamic Studies of Zinc Adsorption on Expanded Vermiculite

Because of industrial growth, large amounts of effluents are generated, which need to be treated. Among the micropollutants usually present in industrial effluents, heavy metals are especially dangerous to aquatic environment because they are bioaccumulated along the food chain. This work aims to study the removal of zinc ions in aqueous solution by adsorbing them onto expanded vermiculite. In addition, equilibrium and thermodynamics studies were carried out to verify the spontaneity and the characteristics of the process. Langmuir, Freundlich and Dubinin–Radushkevichs models were applied to the data obtained from isotherms at temperatures of 273, 293, 313 and 333 K. Furthermore, experiments in static system were carried out to choose a suitable eluent to this process, to find the metal concentration and identify a method for effective recovery of the adsorbent. This adsorption process was found to be spontaneous, favourable, endothermic and physical. The best eluting agent was ethylenediaminetetraacetic acid (0.1 M); however, for cycle adsorption experiments the best agent was CaCl2 (0.1 M).

High Molecular Sericin from Bombyx mori Cocoons: Extraction and Recovering by Ultrafiltration

The present study focus on sericin extraction process from Bombyx mori cocoons using water in absence of chemical additives under different physical conditions aiming to obtain high molecular weight sericin. Separation and fractionation of sericin proteins to obtain high molecular weight material was also carried out using ultrafiltration process at different operating modes: batch, diafiltration and batch with back flushing water pulse. The molecular weight of extracted sericin protein using pure water showed in general a size distribution varying from 20 up to 400 kDa, with major peaks between 200 kDa and 100 kDa and peaks with fraction of sericin lower than 100 kDa, depending on conditions used in the extraction and concentration. The results demonstrated viability to separate sericin fractions having molecular size higher than 50 kDa, using the ultrafiltration process with 50 kDa cut-off membrane, however, a flux decline above 90 % was detected independent of operating mode. Increasing the concentration factor from 2 to 4 promotes the permeation of sericin molecules of high molecular weight, reducing the rejection coefficient of 71.1 % to 60.4 %.

Nickel, lead and zinc removal by adsorption process in fluidised bed.

This work presents an experimental study of nickel (II), lead (II) and zinc (II) metallic ions removal by adsorption in zeolite Baylith WE984. The experiments were conducted in a fluidised-bed rig with 300 grams of zeolite particles having diameter in the range 1 - 4mm. The volumetric flow rate of the fluidizing solution was 4.1 lmin−1. Metal concentrations in the solution were measured by atomic absorption and the breakthrough curves were obtained for concentrations of metals ranging from 5 to 30 ppm (pH= 2). Experimental results obtained were fitted to the Renken model for analysis of the mass transfer resistance and the kinetic of adsorption. It was verified that the kinetic of adsorption was the limiting factor for the metallic ion retention in fluidised bed. Competitiveness of the metals adsorbed into Baylith zeolite were also analyzed being found the following order of preference for the metal removals: nickel > zinc > lead. The competitiveness was evaluated simultaneously in the combination of 2 × 2 and the three metals.