Organisation of the Analytical, Stoichiometric, and Thermodynamic Information for water Chemistry Calculations

A common feature of the chemical processes of the hydrosphere and water treatment plants is that essentially the same types of chemical equilibrium reactions occur in both fields. These equilibria could be acid/base, complexation, redox, precipitation, and interfacial processes. Since these reactions may also occur in combination, the aqueous environments are unavoidably multispecies systems. Due to multiple equilibria, the state of aggregation, the state of oxidation, as well as the electric charge of the species may changedramatically. Calculation of the equilibrium concentration of the species is facilitated by the availability of analytical, stoichiometric, and thermodynamic information that are consistently organised into an ASTI matrix. The matrix makes it possible to apply a uniform algebraic treatment for all occurring equilibria even, if later on, further reactions have to be included in the chemical model. The use of the ASTI matrix enables us to set up the necessary mass balance equations and equilibrium relationships, which together form a non-linear system of equations (NLSE). The goal of our paper is to show that the use of the ASTI matrix approach in cooperation with the powerful engineering calculation software, MATHCAD14, results in fast and easy handling of the NLSE-s and, consequently, the calculations of speciation in aqueous systems. The paper demonstrates the method of application in three examples: the calculation of the pH dependence of the solubility of calcite in closed and open systems, the calculation of the pH and pε in a system where acid/base reactions, complexation equilibria, and redox equilibria occur, and a study of adsorption of lead ions on aluminium oxide

Formázószerek jelenlétének hatása a talajoldat szervesanyag-tartalmára

The forming agents Supragil WP (anionic) and CTAB (cationic) were investigated in model soil solution systems because these compounds are frequently used in different products (pesticides, vaccines, cosmetics etc.) that can become environmental contaminants. The colloidal system was characterized by surface tension and zeta potential measurements. The humic substances form associates with both agents and the system is able to be stabilized either with negative (in case of Supragil) or with positive charge (in case of CTAB). This indicates the risk of the application of these compounds especially near either to the groundwater level or to any surface water. Adsorption of Supragil on different soils resulted in two-step of isotherms. The formation of two layers is indicated also by zeta potential measurements

Fertőtlenítés szerepe diclofenac-kal szennyezett víz kezelése során

The drug active ingredient “diclofenac” is one of the most frequently identified micropollutants in water resources. Since the addition of chlorine as disinfectant has to be used in the last step of water treatment, its chemical reaction with diclofenac was investigated in the presence of natural organic matter at pH=7. Chlorination and oxidation are parallel reactions but the latter is very slow. The decay of the drug is slower in the presence of humic substances than in their absence but the clay mineral content of the extract prepared from sandy soil can accelerate the chlorination reaction

Elimination of 4-nitrophenol from water by oil shale

In this work, oil shale was used for elimination of a model potential anthropogenic pollutant, 4-nitrophenol. Sorption experiments were utilized under various different conditions; oil shale was pretreated with sodium azide to inhibit the microorganisms’ activity, and the results were compared to those without pretreatment of oil shale. After a 24-hour equilibration time, in the presence of sodium azide pretreated oil shale, the concentration of 4-nitrophenol was higher than in the case of unpretreated oil shale, which indicates that during the sorption process not only sorption, but also decay of 4-nitrophenol took place. Desorption isotherm was also determined. Degradation experiments were applied to investigate how this persistent molecule transforms in the presence of oil shale. Sodium azide pretreated oil shale and MnCl2 additive were also used to examine the effect of microorganisms and manganese(II) ion on the transformation of 4-nitrophenol. It was found that the presence of manganese(II) ion speeded up, while the sodium azide slowed down the transformation of the model molecule