Fly ash based zeolite analogues: versatile materials for energy and environment conservation

Adsorption of Congo Red Dye on HDTMA Surfactant-Modified Zeolite A Synthesized from Fly Ash

Adsorption of anionic dyes Congo Red (CR) on HDTMA surfactant-modified zeolite A has been studied. The zeolite A, which is synthesized from coal fly ash, was modified with surfactant hexdeciltrimethylammonium bromide (HDTMA-Br) as much as 200% cation exchange capacity (CEC) of the zeolite. The effect of pH, contact time and initial concentration on the CR adsorption has been evaluated.The adsorption was carried out in a batch reactor at various pH, contact time and initial concentration on the given temperature. The amount CR adsorption varies as a function of pH, contact time and initial concentration of solution. Adsorption model of Langmuir and Freundlich from empirical data is used for this experiment. The Langmuir isotherm is more suitable for this adsorption. The experimental data fulfilled pseudo second-order kinetic models. The surfactant-modified zeolite A is more effective than zeolite A without modified on the adsorption of CR in aqueous solution.

Potassic zeolites from Brazilian coal ash for use as a fertilizer in agriculture

Brazilian coal has an ash content ranging from 30 to 50% by weight. Consequently, its use in coal-fired thermoelectric for power production generates a lot of waste. The construction sector is the largest consumer of coal ash, but it cannot absorb the entire amount generated. Thus, other applications for coal ash should be studied in aim to optimize the use of this industrial waste. This research had as focus to synthesize potassic zeolite from of the coal ash into on potassium fertilizer for the grown wheat plant. In this work, it was used a subbituminous coal from Mina do Leão (RS, Brazil) presenting 48.7% ash content on a dry basis. Concerning the synthesis of potassic zeolite, it was adopted the conventional method of hydrothermal treatment with potassium hydroxide. A schedule of experiments was conducted in order to define the optimum condition of zeolite synthesis that was then used an alkaline solution of 5M KOH with a reaction time of 24h at 150°C. According to this procedure, it was obtained a zeolite with a single crystalline phase, identified through X-ray diffraction as Merlinoite. Subsequently, it was performed a set of tests using potassic zeolite asa fertilizer for plants in a greenhouse. The synthesized potassic zeolite showed a good potential for its use as fertilizer in agriculture.

Synthesis of Zeolite A from Coal Fly Ash by Alkali Fusion and Hydrothermal

Zeolite A has been synthesized by a modified alkali fusion followed hydrothermal process. Hydrothermal was performed at a temperature of 90 °C for 4 h in a stainless steel reactor. Characterization of the synthesized zeolite was conducted using various techniques, i.e. X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) and measurement of cation exchange capacity (CEC). The characterization results showed that zeolite A was selectively obtained by this method. The diffract gram, SEM image, and IR spectra of the synthesized zeolite A showed a similarity with the commercially available zeolit A.

A comparison of basic dye adsorption onto zeolitic materials synthesized from fly ash

This investigation reveals the adsorption characteristics of two basic dyes, thionine (TH) and safranine T (ST), onto fly ash (FA) and its three zeolitized products prepared at different hydrothermal conditions. Typical two-step isotherms were observed for TH adsorption onto four adsorbents, whereas the isotherms of the larger ST molecules were S-shaped. The adsorption capacities of the zeolitized fly ash (ZFA) estimated from the first plateau region of the TH isotherms was nearly twice the FA capacity. The capacities increased by up to five times in the second plateau region. The adsorption capacity of FA for ST is equivalent that of TH, whereas the capacities of ZFA are lower than those found for TH. The equilibrium results were well-described by the Freundlich isotherm model. The kinetic data obtained in the temperature range of 298-318 K was analyzed using Paterson's and Nernst Plank's approximations based on the homogeneous surface diffusion model (HSDM). The thermodynamic functions for the transition state were evaluated from the temperature-dependence of the surface diffusion coefficients by applying the Eyring model.

Aplicação de material zeolítico sintetizado de cinzas de carvão como adsorvente de poluentes em água

Cinzas leve de carvão tratadas pelo método hidrotérmico foram usadas como adsorvente de baixo custo para a remoção de íons metálicos e corante de solução aquosa. As isotermas de adsorção das cinzas leve tratadas foram estudadas e os resultados foram ajustados pelos modelos de Langmuir e Freundlich. A isoterma de Freundlich descreveu melhor o processo de adsorção do azul de metileno. Os dados de equilíbrio para a adsorção dos íons zinco e cádmio se ajustaram melhor á equação de Langmuir. O valor máximo de capacidade de adsorção obtido foi de 0,78 (mg g-1)(L mg)1/n para o azul de metileno, 38,1 mg g-1 para o Zn2+ e 67, 5 mg g-1 para o Cd2+. Os materiais sintetizados exibiram capacidades de adsorção muito maiores do que as das cinzas leves usadas como matéria-prima. O estudo mostrou que o material zeólitico pode efetivamente adsorver azul de metileno e íons metálicos com eficiências de remoção na faixa de 82-99%.