Surface Basicity and Hydrophilic Character of Coal Ash-Derived Zeolite NaP1 Modified by Fatty Acids.

Zeolite NaP1 was found to display the highest affinity for CO2 in preliminary modifications of coal fly ash-derived zeolites (4A, Y, NaP1 and X) by four amines (1,3-diaminopropane, N,N,N',N'-tetramethylethylenediamine, Tris(2-aminoethyl)amine and ethylenediamine). In the second step, different fatty acid loaded NaP1 samples were prepared using palmitic, oleic and lauric acids. CO2 and H2O thermal programmed desorption (TPD) revealed changes in intrinsic basicity and hydrophilic character, expressed in terms of CO2 and H2O retention capacity (CRC and WRC, respectively). Infrared spectroscopy (IR), N2 adsorption-desorption isotherms and scanning electron microscopy allowed for correlating these changes with the type of interactions between the incorporated species and the zeolite surface. The highest CRC values and the lowest CO2 desorption temperatures were registered for NaP1 with the optimum content in palmitic acid (PA) and were explained in terms of the shading effect of surface acidity by the rise of basic Na+-palmitate salt upon cation exchange. The amine/fatty acid combination was found to paradoxically mitigate this beneficial effect of PA incorporation. These results are of great interest because they demonstrate that fatty acid incorporation is an interesting strategy for reversible CO2 capture.

Bibliometric approach to the perspectives and challenges of membrane separation processes to remove emerging contaminants from water.

The presence of contaminants in water is concerning due to the potential impacts on human health and the environment, and ingested contaminants cause harm in various ways. The conventional water treatment systems are not efficient to remove these contaminants. Therefore, novel techniques and materials for the removal of contaminants are increasingly being developed. The separation process using modified membranes can remove these micropollutants; therefore, they have attracted significant research attention. Among the materials used for manufacturing of these membranes, composites based on graphene oxide and reduced graphene oxide are preferred owing to their promising properties, such as mechanical resistance, thermal and chemical stability, antifouling capacity, water permeability, high thermal and electrical conductivity, high optical transmittance and high surface area. Membrane separation processes (MSP) can be used as secondary or tertiary treatment during the supply of wastewater. However, the efficient and accessible applications of these technologies are challenging. This study aims to demonstrate the main concepts of membrane separation processes and their application in the removal of emerging contaminants. This study reports bibliometric mapping, relevant data on studies using membranes as water treatment processes, and their viability in industrial applications. The main challenges and perspectives of these technologies are discussed in detail as well.

BTEX removal from aqueous solutions by HDTMA-modified Y zeolite.

Various technologies have been used for the treatment and remediation of areas contaminated by BTEX (benzene, toluene, ethylbenzene and xylenes), which are organic compounds that are of particular concern due to their toxicity. Potential applications of synthetic zeolites for environmental fieldwork have also been reported worldwide. In this work, a hexadecyltrimethyl ammonium (HDTMA) surfactant-modified synthetic zeolite was investigated for its efficiency in removing BTEX from aqueous solutions. Three surfactant-modified zeolites were synthesized, with amounts of surfactant corresponding to 50%, 100%, and 200% of the total cation-exchange capacity (CEC) of the synthetic zeolite Y. The results of the BTEX adsorption experiments onto both synthetic zeolite and surfactant-modified zeolites (SMZ) showed that the SMZ-100 (zeolite modified with surfactant levels at 100% of CEC) was the most efficient modified zeolite for BTEX removal. Kinetics studies indicated that the multicomponent adsorption equilibrium was reached within 6 h and followed pseudo-second-order kinetics. The Langmuir, Freundlich, Redlich-Peterson and Temkin models were used to evaluate the BTEX adsorption capacity by SMZ-100. The Temkin model was found to be suitable for all BTEX compounds in a multicomponent system. Regeneration cycles of the modified zeolite were also performed, and the results showed that the adsorbent could be used efficiently in as many as four adsorption cycles, except for benzene.

Production of zeolitic materials in pilot scale based on coal ash for phosphate and potassium adsorption in order to obtain fertilizer.

The use of different types of zeolites (X, Na-P1, and 4A) synthesized by different methods and scales were tested in this work to adsorb nutrients present in synthetic solutions and industrial effluents for later application as fertilizer. Modifications with calcium chloride were performed on the zeolite with the best performance to increase its adsorption capacity. The best performing zeolite was type X (ZXH) produced on a pilot scale by the hydrothermal process. Its adsorption capacity without modification was 149 mg P-PO4/g zeolite and 349 mg K/g zeolite. With the change, there was a fourfold increase in these results, which were up to threefold higher than reported in the literature. The kinetic model that best characterized the adsorption process was the intraparticle diffusion model, and the equilibrium isotherm was that of Freundlich. The adsorption tests performed with industrial effluent showed high removal of the nutrients of interest (> 90% for PO43- and > 95% for K+). The desorption tests with zeolites nutrient-loaded from synthetic solutions showed 13 to 24% PO43- and 14 to 47% K+ release within 24 h, while for zeolite nutrient-loaded from effluent the release were 7 and 100% for PO43- and K+, respectively. The results we obtained in this work indicated the potential use of zeolites in the treatment of effluent and its application as a fertilizer.

Alkydic resin wastewaters treatment by fenton and photo-Fenton processes.

Advanced oxidation processes are an emerging option to treatment of the painting industry effluents. The aim of this study was to compare the effectiveness of the Fenton and photo-Fenton processes in chemical oxygen demand (COD), total organic carbon (TOC) and phenolic compounds removal from wastewaters generated during alkydic resins manufacture. The optimized treatment conditions are the following: pH 3.0, 15.15x10(-3)molL(-1) FeSO(4) and 0.30molL(-1) H(2)O(2) for a reaction time of 6h. photo-Fenton experiments were carried out in the presence of sunlight or artificial radiation and complementary additions of H(2)O(2) were made for all experiments. The best results were obtained with photo-Fenton process assisted with solar radiation, with reductions of 99.5 and 99.1% of COD and TOC levels, respectively. Fenton and photo-Fenton (with artificial irradiation) processes presented lower but not insignificant removals, within 60-80% reduction for both COD and TOC. In addition, an excellent removal (95%) of total phenols was obtained using photo-Fenton process assisted with artificial irradiation. This study demonstrated that the use of photo-Fenton process on alkydic resins wastewater treatment is very promising especially when solar light is used.

Decontamination of CCA-treated eucalyptus wood waste by acid leaching.

Preservatives such as chromated copper arsenate (CCA) are used to increase the resistance of wood to deterioration. The components of CCA are highly toxic, resulting in growing concern over the disposal of the waste generated. The aim of this study was to investigate the removal of Cu, Cr and As present in CCA-treated eucalyptus wood from utility poles removed from service in southern Brazil, in order to render them non-hazardous waste. The removal was carried out by acid leaching in bench-scale and applying optimal extractor concentration, total solid content, reactor volume, temperature and reaction time obtained by factorial experiments. The best working conditions were achieved using three extraction steps with 0.1 mol L(-1) H2SO4 at 75°C for 2h each (total solid content of 15%), and 3 additional 1h-long washing steps using water at ambient temperature. Under these conditions, removal of 97%, 85% and 98% were obtained for Cu, Cr and As, respectively, rendering the decontaminated wood non-hazardous waste. The wastewater produced by extraction showed acid pH, high organic loading as well as high concentrations of the elements, needing prior treatment to be discarded. However, rinsing water can be recycled in the extraction process without compromising its efficiency. The acid extraction is a promising alternative for CCA removal from eucalyptus wood waste in industrial scale.

Integrated synthesis of zeolites 4A and Na-P1 using coal fly ash for application in the formulation of detergents and swine wastewater treatment.

Several researchers have reported zeolite synthesis using coal ash for a wide range of applications. However, little attention has been given to green processes, including moderate synthesis conditions, using waste as raw material and effluent reuse or reduction. In this study, Brazilian coal fly ashes were used for integrated synthesis of zeolites 4A and Na-P1 by two different routes and under moderate operating conditions (temperature and pressure). Both procedures produced zeolites with similar conversions (zeolite 4A at 82% purity and zeolite Na-P1 at 57-61%) and high CEC values (zeolites 4A: 4.5meqCa(2+)g(-1) and zeolites Na-P1: 2.6-2.8meqNH4(+)g(-1)). However, process 1 generated less effluent for the zeolite mass produced (7mLg(-1)), with low residual Si and Al levels and 74% of the Si available in the coal fly ash incorporated into the zeolite, while only 55% is used in process 2. For use as a builder in detergents, synthetic zeolite 4A exhibited conformity parameters equal to or greater than those of the commercial zeolite adopted as reference. Treatment of swine wastewater with zeolite Na-P1 resulted in a high removal capacity for total ammoniacal nitrogen (31mgg(-1)).

Alternative spectrophotometric method for standardization of chlorite aqueous solutions.

The chlorite ion is the principal by-product of the treatment of drinking water by chlorine dioxide. In function of the chlorite salt instability, standard solutions of this ion need standardization by iodometric titration, which is a reliable method although labor intensive and time consuming. An alternative method to standardization of aqueous chlorite solutions, based on its direct UV absorption measurement, was presented. Besides the maximum absorption (260 nm) generally used in other studies, the minimum (239 nm) and isosbestic (248 nm) wavelengths were proposed as supplementary points to chlorite quantification and their molar absorptivity coefficients were estimated (155.2+/-0.6, 104.5+/-1.0 and 69.0+/-1.2 L cm(-1) mol(-1), respectively). The direct spectrophotometric determination of chlorite could be made selectively even in the presence of high concentration of major contaminants (chorine dioxide, chloride and chlorate), being a simple and rapid method, consuming very low volume of sample and generating low quantities of laboratory wastes.

Avaliação in vitro da liberação de níquel por braquetes metálicos / In vitro nickel release from metallic orthodontic brackets

O aço inoxidável austenítico é utilizado para confecção de dispositivos ortodônticos e contém cerca de 8-10% de níquel em sua composição, metal este responsável por reações alérgicas de hipersensibilidade. Acredita-se que a liberação de níquel dos dispositivos metálicos pode provocar dermatites de contato em pacientes suscetíveis. Este estudo laboratorial avaliou a influência de três variáveis na liberação de níquel: 1)o tipo de liga do braquete; 2)o tipo de solução de imersão e 3) o esforço mecânico nas canaletas dos braquetes de aço inoxidável austenitico. Foram avaliados seis grupos experimentais e dois grupos controle. As amostras foram imersas em tubos de ensaio contendo saliva artificial ou solução salina, sendo mantidas sob agitação e temperatura constante (37°). A quantidade de níquel presente nas soluções foi avaliada com espectrofotômetro de absorção atômica (Varian - Spectra A55) em dois momentos: após uma semana e após duas semanas. Os resultados revelaram que os braquetes de aço inoxidável com baixo teor de níquel apresentaram menor liberação deste elemento. Foi possível constatar que o tipo de solução alterou o padrão de liberação de níquel pelos dispositivos avaliados. O esforço mecânico aplicado sobre os braquetes de aço inoxidável austenitico não alterou a quantidade de níquel liberada.