Roman Marsalek

Comparative study of CTAB adsorption on bituminous coal and clay mineral

Adsorption of cetyltrimethylammonium bromide (CTAB) onto bituminous coal (BC) and a clay mineral, montmorillonite (MMT), was studied. Simultaneous measurements of the CTAB adsorption and zeta potential determination of the adsorption suspensions were carried out. The adsorption isotherms were found to be of the typical Langmuir type; values of the CTAB adsorption capacities were calculated (am = 0.65 mmol g−1 for coal and am = 3.24 mmol g−1 for MMT). The shape of the adsorption isotherms was correlated with zeta potential values at the adsorption equilibrium. The adsorption properties of both sorbents were studied by voltammetry on carbon paste electrodes (CPE) modified with coal-CTAB and MMT-CTAB system, respectively. Open circuit sorption with differential pulse voltammetry was performed in order to compare the sorption properties of the systems with the unmodified sorbents. The Cu2+ adsorption on BC and MMT decreased to approximately 50 % and 40 %, respectively. The surface adsorption mechanism of CTAB on coal based on hydrophilic interactions was proposed. In the case of montmorillonite, the CTAB intercalation is expected via ion exchange into the inter-layer space forming a double- or triple-layer arrangement.

The Influence of Surfactants on the Zeta Potential of Coals

Abstract The surface of three different kinds of coal was modified by three surfactants (cationic, anionic, and non-ionic). Changes on coal surface were examined by the zeta potential technique. The influence of the dispersion of pH, concentration of surfactants, and contact time were investigated. The most significant change in zeta potential resulting from adding surfactants was observed in activated coal (hydrophobic surface, largest BET surface area). Adding the cationic surfactant led to an increase of the zeta potential, contrary to measuring done in water. The anionic surfactant decreased the value of the zeta potential; however, this change was not too remarkable. The results proved that even a very low concentration of the cationic surfactant (0.01 mmol/L) causes a remarkable change of the zeta potential. On the other hand, a similar effect was observed until the concentration of the anionic surfactant reached about 10 mmol/L. The mechanism of binding surfactants is not simple, but preferential hydrophobic interactions were discovered.

Immobilization of Heavy Metals and Phenol on Altered Bituminous Coals

Abstract This article evaluates adsorption ability of the altered bituminous coals to remove heavy metals and/or phenol from aqueous solutions. As for heavy metals, copper (II), cadmium (II) and lead (II) cations were used. In addition to phenol, cyclohexanol and 2-cyclohexen-1-ol were also examined. Adsorption experiments were conducted in the batch mode at room temperature and at pH 3 and 5. To characterize the texture of coal samples, adsorption isotherms of nitrogen at −196°C, enthalpies of the immersion in water, and pH values in aqueous dispersions were measured. Coal hydrogen aromaticities were evaluated from the infrared spectrometric examinations (DRIFTS). Based on the investigations performed, cation exchange was confirmed as the principal mechanism to immobilize heavy metallic ions on coals. However, apart from carboxylic groups, other functionalities (hydroxyl groups) were found to be involved in the adsorption process. During adsorption of phenol, π-π interactions between π-electrons of phenol and aromatic rings of coal proved to play the important role; however, no distinct correlation between adsorption capacities for phenol and hydrogen aromaticities of the coal was found. Probable involvement of oxygenated surface groups in the immobilization of phenol on coal was deduced. As a result, for waste water treatment, oxidative altered bituminous coal can be recommended as a suitable precursor, with the largest immobilization capacities both for metallic ions and phenol, as found in the studied samples.

Application of Electrochemistry for Studying Sorption Properties of Montmorillonite

© 2012 Navratilova and Marsalek, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Application of Electrochemistry for Studying Sorption Properties of Montmorillonite

Adsorption of the SDS on Coal

Simultaneous measurements of the sodium dodecyl sulphate (SDS) adsorption on coal and zeta potential determination of the (adsorption) suspensions were carried out. Three samples of sub-bituminous, bituminous and oxidative altered bituminous coal were investigated. The adsorption isotherms were found to be of typical Langmuir type, values of the SDS adsorption capacities have been calculated. Shape of the adsorption isotherms was correlated with zeta potential values of the suspensions in (adsorption) equilibrium. The results indicate that adsorption of SDS on coal is going mainly through hydrophobic interactions between the surfactant molecules and the coal surface.

Immobilization of Heavy Metal Ions on Coals and Carbons

Adsorption of heavy metals from the aqueous phase is a very important and attractive separation techniques because of its ease and the ease in the recovery of the loaded adsorbent. For treatment of waste as well as drinking water, activated carbons are widely used (Machida et al., 2005; Guo et al., 2010). Due to an increasing demand on thorough purification of water, there is a great need to search for cheaper and more effective adsorbents. Thus, alternative resources for manufacturing affordable activated carbons are extensively examined (e.g. Guo et al., 2010; Qiu et al., 2008; Giraldo-Gutierrez & MorenoPirajan, 2008). Simultaneously, natural coals are investigated as economically accessible and efficient adsorbents to remove heavy metals (Kuhr et al., 1997; Zeledon-Toruno et al., 2005; Mohan & Chander, 2006). Radovic et al. (2001) published a principal comprehensive review of the adsorption from aqueous solutions on carbons with incredible 777 references. Their analytical survey covers adsorption of both organic and inorganic compounds (including heavy metals) and, certainly, it remains a basic source of information on the topics. This chapter is concerned with the immobilization of heavy metals on carbonaceous surfaces, and, it attempts to compare adsorption behaviour of activated carbons with that of natural coals. Here, references published in the last decade are mainly reported, the literature findings being immediately confronted with experimental data as obtained from laboratory examinations of two natural coals. First, a brief insight into adsorption kinetics is given, followed by a survey of models to describe adsorption at equilibrium. The issue of thermodynamics of heavy metals adsorption follows. Finally, the possible immobilization mechanisms of heavy metals on carbons/coals are carefully considered and discussed.

Adsorption of Selected Ions on Ferro-Precipitates from Aqueous Solutions

The main aim of the paper is to evaluate ferro-precipitate as an immobilization agent for various ions from aqueous solutions. Heavy metals, namely lead, copper and chromium were adsorbed as well as arsenate and phosphate. In addition, the adsorption of surfactants, sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) was carried out. Linear as well as non-linear regression of adsorption isotherms confirmed the Langmuir model applicability. Adsorption capacities (am) were calculated. The highest adsorption capacity was found for arsenate and phosphate respectively (am = 1.36 mmol g−1 for arsenate and 0.70 mmol g−1 for phosphate). Lower but still enough adsorption capacity was found for heavy metals (am = 0.76 mmol g−1 for lead, 0.58 mmol g−1 for copper, 0.38 mmol g−1 for chromium, and the lowest values were shown for surfactants (a = 0.38 mmol g−1 for CTAB and 0.21 mmol g−1 for SDS).