Dyes and pigments are important organic pollutants of the water environment. Dyes may be removed from wastewater by using one of the most efficient methods for wastewater treatment-adsorption onto porous (natural and waste) minerals or organogenie substances. Feasibility of using smectite-clay, co-occurring in brown coal deposits, for removal of direct dyes was investigated. The Freundlich linear regression model was better in modeling of sorption direct dyes onto smectite-clay; it yielded better fit of the theoretical isotherm to the experimental data. The electrostatic interactions and hydrogen bonds were shown to play the most important role in adsorption of direct dyes onto smectite-clay.

The sorption isotherm and sorption kinetics of NH4+ by the Fen River reservoir sediment were investigated for a better understanding of the NH4+ sorption characteristics and parameters. The results showed that Q (adsorption content) increased with the increase of Ceq (equilibrium concentration), sorption isotherms could be described by Freundlich equation (R2 from 0.97 to 0.99). Cation exchange capacity (CEC) had a significant correlation with the parameters K and n (R2 was 0.85 and 0.95, respectively). The ENC0 (Ceq as Q was zero) of S1, S2, S3 and S4 was 1.25, 0.57, 1.15 and 1.14 mg L-1, respectively, and they were less than the NH4+ concentrations in reservoir water. The sediments released NH4+ to the Fen River reservoir water and acted as a pollution source, in the form of complex and heterogeneous adsorbents. The NH4+ adsorption kinetic process was composed of ‘fast’ and ‘slow’ reaction patterns and could be fitted using both Elovich equation and Pseudo second-equation. More than one-step may be involved in the NH4+ sorption processes, and interior diffusion was not dominant ion action.

The compost derived from cellulosic material coming from the Public Utility Company in Zabrze

(Poland) was investigated for its capability for adsorbing acid dyes from aqueous solution at various concentrations of the dyes and the compost dosages. Four acid dyes were investigated: Acid Red 18 (AR-18), Acid Blue

9 (AB-9), Acid Green 16 (AG-16) and Acid Black 1 (ABk-1). The adsorption isotherms were determined by

comparing the experimental data with the isotherm models (Freundlich, Langmuir and Dubinin–Radushkevich

models). The sorption capacity of the compost depended on the initial concentrations of dyes in the solution,

compost dosage, and on the structure of dyes. The maximum sorption capacities of the compost for adsorbing

particular dyes may be ordered as follows: ABk-1 > AG-16 > AB-9 > AR-18. The amounts of bound and the

percentages of removed acid dyes from effluent depended on the adsorbent dosage. The growth of the dye removal percentages with growing adsorbent mass may be attributed to the growth of the adsorbent uptake surface

with growth of the adsorbent mass. The dyes were bound onto the surface of compost through the electrostatic

interaction between the surface (negatively charged at pH > pHPZC) and the dye cations (AG-16), and/or through

the hydrogen bond between the functional groups of the humic matter in compost (–OH, –COOH) and the

functional surface groups of AR-18, AB-9 and ABk-1 dyes (–OH, –NH2

). At the experiment conditions, the

Freundlich and Dubinin-Raduskevich adsorption isotherm models fitted the equilibrium data very well (much

better than the Langmuir one). The values of 1/n in the Freundlich equation and E in the Dubinin-Raduskevich

one indicate the favourable adsorption. The studied compost may be used as a low-cost sorbent for the removal

of acid dyes from wastewater released by textile industries. However, elevated values of chemical oxygen demand (COD) in the final solutions may enhance the solubility of humic compounds.

The main purpose of the present paper is to distinguish water located in various types of pores contained within cement paste. The water sorption isotherm is the starting point of the experimental analysis. The investigation was conducted employing the conventional gravimetric method on cement paste composed with w/c=0.5. The investigation was conducted for the following relative humidity values: 11%, 54%, 75%, 84%, 93%, 97% and 100%. Once samples reached the equilibrium water content they were investigated by means of differential scanning calorimetry (DSC), which enabled us to record exothermic peaks corresponding to the crystallization of different water portions. Moreover, we intended to investigate the thermodynamic characteristics of the liquid phase confined within cementitious materials. Hence, the artificial pore solution was prepared. In order to determine the phase transition temperature and the amount of formed ice, the solution was used to saturate silica gel, which is a chemically passive material. Then the thermal analysis was conducted.