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.

This paper describes the adsorption of Cd2+and Pb2+ions using sodic bentonite clay type Fluidgel modified. The Fluidgelbefore 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 Fluidgelmodified chemically and 91.08% for lead by Fluidgel modified chemical and thermally.

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.

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.

Cu (II) removal equilibrium from aqueous solutions using calcined clays "Bofe" and "Verde-lodo" has been studied by batch and fixed-bed in static and dynamic systems, respectively. Analyses were performed for physicochemical characterization of clays using the techniques: X-ray fluorescence (XRF), thermogravimetry (TG), N2 adsorption (BET) and Cationic Exchange Capacity (CEC). Batch experiments were performed at a constant temperature, adjusting the pH of the solution in contact with clays. Adsorption assays in fixed bed were conducted at the flow rate determined through mass transfer zone (MTZ). Langmuir and Freundlich models were adjusted to equilibrium data. The results of characterization indicated that the temperature of 500ºC is best suited for the calcination of the clays. The maximum adsorption capacity was higher for dynamic system than fixed bed compared to static system, enhancing from 0.0748 to 0.1371 and from 0.0599 to 0.22 mmol.g-1 of clay for "Bofe" and "Verde-lodo", respectively.

The marine algae Sargassum filipendula was collected from São 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 (pH ZPC). 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 pH ZPC 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.

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.