Meuris Gurgel Carlos da Silva

Biosorption of chromium by alginate extraction products from Sargassum filipendula: investigation of adsorption mechanisms using X-ray photoelectron spectroscopy analysis.

The alginate extraction products from Brazilian brown seaweed Sargassum filipendula were studied for chromium biosorption. Batch experiments were conducted at pH 2 and 3 and 20°C to determine the sorption capacity of this biosorbents for chromium (VI) and (III). The biomass was characterized before and after metal binding by X-ray photoelectron spectroscopy (XPS) in order to determine the mechanisms of chromium biosorption. The residue has a high adsorption capacity, close the value obtained with seaweed and higher than that of alginate for both Cr(III) and Cr(VI). XPS analysis of the biosorbents revealed that carboxyl, amino and sulfonate groups are responsible for the binding of the metal ions. The analysis also indicated that the Cr(VI) bound to the biomass was reduced to Cr(III).

Characterization and evaluation of copper and nickel biosorption on acidic algae Sargassum Filipendula

The marine algae Sargassum filipendula was collected from Sao Paulo seashore (Brazil) and submitted to treatment with acid. The biosorption mechanisms of Cu2+ and Ni2+ ions onto acidic algae Sargassum filipendula were examined using various analytical techniques: Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and potentiometric titration (pHZPC). The effect of acidic treatment on algae by hydrochloric acid (pH 2.0, 3.0, 4.0 and 5.0) was evaluated for Cu2+ and Ni2+ adsorption. Alginate was extracted from raw algae and the two types of acids present in the biomass (β-D-mannuronic (M) and α-L-guluronic (G) acid) were characterized by 13C NMR. The M/G ratio was found to be 0.50. According to the pHZPC analysis, at a pH higher than 5.5 the acidified algae surface presents a negative charge. The FT-IR analyses showed that the main chemical groups involved in the biosorption were carboxylic, alcoholic, sulfonate and amino groups.

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

Sargassum filipendula alginate from Brazil: Seasonal influence and characteristics

The aim of this work is focused on the extraction and characterization of the Brazilian seaweed Sargassum filipendula alginate. Alginates obtained at different seasons were characterized by liquid state nuclear magnetic resonance spectroscopy and scanning electron microscopy. The alginate extraction efficiency was about 20%. Different seasons of the year and different stages in the life cycle of Sargassum sp. in southeastern Brazil influenced the M/G and, consequently, the technological properties of extracted alginates.

Extraction of alginate biopolymer present in marine alga sargassum filipendula and bioadsorption of metallic ions

This paper studies the bioadsorption of Pb2+, Cu2+, Cd2+ and Zn2+ ions by marine alga Sargassum filipendula and by the alginate biopolymer extracted from this alga. The objective is to evaluate the importance of this biopolymer in removing different metallic ions by the marine alga S. filipendula. In the equilibrium study, the same affinity order was observed for both bioadsorbents: Pb2+ > Cu2+ > Zn2+ > Cd2+. For Pb2+ and Cu2+ ions when the alginate is isolated and acting as bioadsorbents, adsorption capacities greater than those found for the alga were observed, indicating that it is the main component responsible for the removal of metallic ions. For Zn2+ and Cd2+ ions, greater bioadsorption capacities were observed for the alga, indicating that other functional groups of the alga, such as sulfates and amino, are also important in the bioadsorption of these ions.

Comprehensive Characterization of Sugarcane Bagasse Ash for Its Use as an Adsorbent

This study provides a full characterization of ashes generated from the combustion of bagasse at two different sugarcane ethanol plants, one in the state of Pernambuco, Brazil (SBA1), and the other in Villa Clara, Cuba (SBA2), with a view to examining their usage as adsorbing agents for the removal of heavy metals and various organic impurities. The ash samples were analyzed for both chemical composition and for structural features that would aid their use. Chemical characterization was done spectrally, through the examination of X-ray fluorescence and diffraction, Fourier transform infrared spectroscopy, and thermally, through thermogravimetric and differential thermal analysis. Structural and surface characterization was carried out by examining N2-physisorption, helium pycnometry, and scanning electron microscopy. The results of each analysis were compared to those of recognized or potential adsorbent materials. Both ashes have structural similarities, heterogeneous morphologies, irregular surfaces, and a prevalence of superficial polar groups (carbonyl, carboxyl, and hydroxyl). Based on their physical and chemical characteristics, ashes could be used as adsorbent for both, organic (e.g., dyes, phenols, etc.) and inorganic (e.g., heavy metals) compounds.

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 %.

Characterization of Brazilian Bentonite Organoclays as sorbents of petroleum-derived fuels

This work focused on preparing and characterizing Brazilian bentonite clay through the use of quaternary ammonium salt so as to apply it as a sorbent for petroleum-derived fuels. Bentonite clay was organophilizated by the intercalation of quaternary ammonium salts such as cetyl-pyridinium chloride and benzalkonium chloride. The resulting materials were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, N2 physisorption and infrared spectroscopy techniques. The clay similarity with petroleum-derived fuels, gasoline and diesel oil were defined by sorption and swelling tests. The increase in basal spacing and the appearance of absorption bands related to the CH2 and CH3 groups confirm the efficiency of Brazilian organoclays. Removal percentages between 50 and 60 for benzene, toluene and xylene indicate the potential of organoclay in the remediation of areas contaminated by petroleum-derived fuels.

Dynamic adsorption of chromium ions onto natural and crosslinked chitosan membranes for wastewater treatment

Water pollution with heavy metals is a matter of major concern for public health and also for natural resource management. The present study investigated the effect of chemical modifications on biopolymeric adsorbents (based on chitosan membranes) for chromium removal using fixed-bed dynamic adsorption technique. Parameters such as flow rate, initial concentration and crosslinking agents were evaluated, from a practical point-of-view, in order to optimize the adsorption capacity of natural, glutaraldehyde and epichlorohydrin crosslinked chitosan membranes. The adsorption capacity of natural and epiclorohydrin-crosslinked chitosan membranes were very close to each other; however, glutaraldehyde-crosslinked chitosan membranes presented nearly twice the adsorption capacity compared to the other membranes, being the most promising adsorbent in such mass-transfer systems.

A kinetic and equilibrium study of zinc removal by Brazilian bentonite clay

This paper aimed to study the removal of zinc using bentonite clay from the Northeastern Brazil, as an adsorbent. A study of the clay subjected to thermal and chemical treatment was performed in order to evaluate the optimization of the adsorption capacity of this material. For the evaluation of the kinetic equilibrium of the process, experimental tests were carried out in a finite bath system. The maximum amount of metal adsorbed was 0.151 mEq of metal per gram of calcined clay and 0.257 mEq of metal per gram of sodium saturated clay. The kinetic models of pseudo-first order, pseudo-second order and intraparticle diffusion were fitted to experimental data, and the pseudo-second order model provided the best result. The Langmuir and Freundlich models were used for the adsorption equilibrium analysis, and the Langmuir model provided the best fit for sorption isotherms. The physicochemical characterization of clay involved X-ray diffraction, scanning electron microscopy, chemical analysis by energy-dispersive X-ray spectroscopy, helium pyconometry and thermogravimetric analysis. The modified clay has potential use for removing Zn2+ ions replacing more expensive adsorbents, since good adsorption properties will be also associated with great availability and low cost.