Synthesis of Calcium Silicate Hydrate Compounds From Wet Flue Gas Desulfurization (FGD) Waste

In this study Calcium silicate hydrate based products (CSHP) were synthesized from wet flue gas desulfurization waste (FGD) by alkali fusion followed by hydrothermal treatment. The effect of various factors on the formation of products, such as mineralizing agent, fusion temperature and time, crystallization time and addition of Ca and Si were studied as well as the conditions optimized. The FGD and synthesized materials were characterized by using X-Ray (XRD), Scanning Electron Microscope (SEM), X-ray fluorescence (XFR), among other methods. A fusion temperature of 600 °C with NaOH, fusion duration of 1 h, and a subsequent hydrothermal temperature of 100 °C for a reaction of 24 h were found to be the optimal conditions. In these synthesis conditions, CSHP containing tobermorite and Al-tobermorite was the major phases. The synthesized CSHP revealed high selective uptake for Cs+ in water. The maximum adsorption capacity of Cs+ onto the synthesized material, as calculated from the Langmuir model, was 1949 µmol g-1. The performance on the Cs+ removal in the presence of high Na+ contents was also evaluated. The adsorbent material showed a high Cs+ adsorption capacity in deionized water and a decrease of 56% and 62% in saturated media with the Na+ ions and seawater, respectively. Therefore, CSHP as a higher value-added product can be obtained from a by-product of a coal-fired power plant, which has wide range applications, including for Cs+ removal from wastewater

Pyrolytic temperature evaluation of macauba biochar for uranium adsorption from aqueous solutions

Macauba (Acrocomia aculeata) is a palm tree native to the tropical regions of America. In Brazil, it is prevalent in the savannah, known as “cerrado”. A valuable natural and renewable source of vegetable oil for food and cosmetic industries (nut oil) and for biodiesel (mesocarp oil), macauba has the potential to become the new “green gold” of Brazil, not only for its oil quality, but because it could solely be destined for commercial purposes, since it doesn’t compete with food market industry such as soybean and sugar cane. The dark stiff part that protects the nut, called “endocarp”, is generated as a residue in a considerable amount after the processing of the nut oil. Please click on the file below for full content of the abstract

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

Adsorption of Acid Orange 8 Dye from Aqueous Solution Onto Unmodified and Modified Zeolites

The adsorption of the acid dye Acid Orange 8 (AO8) onto unmodified and modified zeolites from coal fly ash and bottom ash was evaluated. The coal fly ash and bottom ash used in the synthesis of the zeolites by alkaline hydrothermal treatment were collected in the Thermoelectric Complex Jorge Lacerda, located in the Santa Catarina State, Brazil, the largest coal burning thermoelectric complex of Latin America. The modified zeolites were modified using the surfactant hexadecyltrimethylammonium bromide. The zeolitic materials were characterized predominantly as hydroxysodalite and NaX. The kinetics studies indicated that the adsorption followed the pseudo-second order kinetics. Linear and non-linear regression methods were used to determine the best fit of equilibrium data. The Freundlich model was better adjusted to the experimental data for all systems studied. The parameters of adsorption isotherms were used to predict the design of the equipment for performing adsorption discontinuous single stage. DOI: http://dx.doi.org/10.17807/orbital.v7i4.76

Sulfonated Polyaniline Coated Mercury Film Electrodes for Voltammetric Analysis of Metals in Water

The electrochemical polymerization of 2-aminobenzenesulfonic acid with and without aniline has been carried by cyclic potencial sweep in sulfuric acid solution at the glassy carbon electrode. The polymer and copolymer formed have been characterized voltammetrically. The sulfonated polyaniline coated mercury thin-film electrodes have been evaluated for use with anodic stripping voltammetry. The electrodes were tested and compared with a conventional thin-film mercury electrode. Calibration plots showed linearity up to 10-7 mol L-1. Detection limits for zinc, lead and cadmium test species are very similar at around 12 nmol L-1. Applications to analysis of waters samples are demonstrated

Remoção de azul de metileno de solução aquosa usando zeólitas sintetizadas com amostras de cinzas de carvão diferentes Removal of methylene blue from aqueous solution using zeolite synthesized from different coal fly ashes samples

<abstract language="eng">Batch sorption experiments were carried out to remove methylene blue from its aqueous solutions using zeolites synthesized from fly ashes as an adsorbent. The adsorbents were characterized by XFR, XRD and SEM. Nearly 90 min of contact time are found to be sufficient for the adsorption of dye to reach equilibrium. Equilibrium data have been analyzed using Langmuir and Freundlich isotherms and the results were found to be well represented by the Freundlich isotherm equation. Adsorption data were fitted to both Lagergren first-order and pseudo-second-order kinetic models and the data were found to follow pseudo-second-order kinetics

Utilization of zeolites synthesized from coal ash for methylene blue removal from water

<div align="justify"><p>The adsorption of methylene blue from aqueous solution was carried out using zeolites synthesized from coal ash as low-cost adsorbents. The coal ash sample was converted to zeolites by hydrothermal treatment using different synthesis parameters. The materials were characterized by physical-chemical analysis, XRD and SEM studies. The adsorption isotherms can be fitted by Freundlich model. The values of the adsorption capacity of adsorbents were similar for adsorbents. Kinetic studies indicate that the adsorption follows pseudo-second-order kinetic model.</p></div