This study investigated a low-energy-consuming procedure for the synthesis of zeolite materials from coal fly ash (CFA). Materials containing zeolite phases, namely Na–X, Na–P1, and zeolite A, were produced from F–class fly ash, using NaOH dissolved in distilled water or in wastewater obtained from the wet flue gas desulphurization process, under atmospheric pressure at a temperature below 70 °C. The influence of temperature, exposure time, and alkaline solution concentration on the synthesized materials was tested. In addition, chemical, mineralogical, and textural properties of the obtained materials were determined by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and cation exchange capacity (CEC). Cd(II), Ni(II), NH4+ cation, and Se(VI) anion sorption experiments were conducted to compare the sorption properties of the produced synthetic zeolites with those of the commercially available ones. Zeolitization resulted in an increase of CEC (up to 30 meq/100 g) compared to raw CFA and enhanced the ability of the material to adsorb the chosen ions. The obtained synthetic zeolites showed comparable or greater sorption properties than natural clinoptilolite and synthetic Na–P1. They were also capable of simultaneously removing cationic and anionic compounds. The structural, morphological, and textural properties of the final product indicated that it could potentially be used as an adsorbent for various types of environmental pollutants.

Among the various technologies tested for removing the anionic species resulting from arsenic contamination, sorption methods have received unflagging interest. Being potential sorbent materials, clay minerals modified by cationic surfactants are often examined for this purpose. Among the clay minerals tested, information regarding sorption properties of expanded vermiculite modified with surfactants is scarce. Therefore, the present study aims to prepare organo-vermiculites modified with hexadecyltrimethylammonium (HDTMA) and benzyldimethylhexadecylammonium (HDBA) at surfactant concentrations of 0.5, 1.0, and 2.0 cation exchange capacity. Modified sorbents were identified and characterized using the analytical methods that can determine phase composition and textural properties of the samples. The sorption of As(III) and As(V) as a function of initial pH value, initial concentration of As(III, V), and initial dosage of sorbent was investigated. The results show that HDTMA and HDBA affect the properties of raw vermiculite. For instance, increase in the concentration of surfactants is often accompanied by a change in interlayer space or textural properties of vermiculite. It was observed that tested organo-minerals adsorbed As(V) to a greater extent compared to As(III). Various analytical studies were carried out and the results revealed the successful synthesis of organo-vermiculite. Moreover, the study also showed that the structure of organo-vermiculite has a significant impact on the uptake of As(III) and As(V) anions.In the last decades, various technologies for removing As from contaminated water have been investigated, such as oxidation, coagulation, ion exchange, precipitation, membrane filtration, biological treatment, and sorption [9][10][11]. However, most of these methods have drawbacks, including high costs, deficient removal, generation of waste products, or high reagent and energy requirement. Among the methods mentioned earlier, adsorption seems to be the most effective method [1,12]. For removal by adsorption technique, activated carbon, metal-organic frameworks, zeolites, bog iron ores, water treatment residuals, and activated alumina have been proven to be promising adsorbents for arsenic removal [13][14][15][16][17].Clay minerals are low-cost and nontoxic sorbents. Raw clays are able to sorb cations owing to their negatively charged surface; however, they display low sorption efficiency for negatively charged contaminants such as arsenic [18]. Nevertheless, clays can be chemically modified by organic surfactants, which change the charge on the clay surface from negative to positive [19]. The organo-clays are hydrophobic materials that can effectively sorb anions and organic compounds. Modified kaolinite, montmorillonite, and illite are the most popular clay minerals that are used as sorbents [20][21][22]. However, only a few studies have focused on using organo-vermiculites to sorb anions [23,24].Vermiculite is a 2:1 phyllosilicate mineral having a sandwiched structure with two tetrahedral shee...

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<p>The occurrence of dyes in wastewater is a threat for environment and living organisms. Therefore many studies have focused on investigation of diverse sorption materials to develop effective adsorption methods of removing these organic compounds (Yagub et al., 2014). Among the wide range of materials, the low-cost sorbents such as clay minerals, fly ash or lignite have received unflagging interest. However, the novel approach is to mix low-cost sorbents, clay minerals with fly ash or lignite, which could promote efficiency of removing chemically varied dyes and impact the modification of sorbent mixtures properties. Thus, the aim of this study is to investigate and compare features of hybrid sorbents: halloysite-fly ash, palygorskite-lignite before and after sorption reactions of selected dyes and evaluate influence of modified properties on their sorption mechanism. The obtained reactions’ products, as well as hybrid and selected raw sorbents after reactions, were studied by Fourier-transform infrared spectroscopy (FTIR), thermal analysis (DTA/TG) coupled with the measurement of evolved gases composition by mass spectrometer (QMS). The morphology of raw sorbents was analyzed by scanning electron microscopy (SEM) equipped with an energy dispersive spectrometer (EDS) for elemental microanalysis. The results show that sorbents features, especially the presence of organic functional groups, negative surface charges, have distinct impact on their sorption behaviour. Each componnent of hybrid sorbents affects the efficiency of dyes sorption. The obtained results revealed that mixing of various low-cost sorption materials may present unexpected properties.</p><p> </p><p>Acknowledgments.</p><p>The studies results have been presented with the partial financial support from the EU project of POWR.03.02.00-00-I038/16-00.</p><p>Literature:</p><p>Yagub M. T., Kanti Sen T., Afroze S., Ang H.M. (2014) Dye and its removal from aqueous solution by adsorption: A review, Advances in Colloid and Interface Science, 209, p. 172-184.</p>

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