This paper presents the results of the study on chemical and the physical properties of waste phosphogypsum (PG) of apatite origin from the former chemical plant Wizow, Poland which are important for further processing and economic use. The research was carried out to verify whether the waste might be useful as a raw material for rare earth elements (REE) recovery and the manufacture of building materials. The following methods were chosen: X-ray diffraction, scanning electron microscopy with an energy-dispersive X-ray detector, atomic absorption spectrometry, inductively coupled plasma spectrometry, differential thermal analysis, thermogravimetry, and gamma spectrometry with natural radioactive contamination analyzer. It has been proven that the chemical physical properties of phosphogypsum provide an opportunity to utilize this waste material as a source of REE and raw material for building purposes. PG contains an overall amount of REE in the interval of 0.343-0.637% by mass and does not show radioactivity level which would exclude it from construction purposes. The presented results serve as the basis for currently available technological directions in the management of apatite PG for useful trade products, which creates a chance for the elimination of its storage necessity by further processing.

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This work presents research on the neutralization of asbestos banned from military use and its conversion to usable products. The studies showed that asbestos can be decomposed by the use of phosphoric acid. The process proved very effective when the phosphoric acid concentration was 30%, the temperature was 90°C and the reaction time 60min. Contrary to the common asbestos treatment method that consists of landfilling, the proposed process ensures elimination of the harmful properties of this waste material and its transformation into inert substances. The obtained products include calcium phosphate, magnesium phosphate and silica. Chemical, microscopic and X-ray analyses proved that the products are free of harmful fibers and can be, in particular, utilized for fertilizers production. The obtained results may contribute to development of an asbestos utilization technique that fits well into the European waste policy, regulated by the EU waste management law.

Dehydrogenase activity is frequently used to assess the general condition of microorganisms in soil and activated sludge. Many studies have investigated the inhibition of dehydrogenase activity by various compounds, including heavy metal ions. However, the time after which the measurements are carried out is often chosen arbitrarily. Thus, it can be difficult to estimate how the toxic effects of compounds vary during the reaction and when the maximum of the effect would be reached. Hence, the aim of this study was to create simple and useful mathematical model describing changes in dehydrogenase activity during exposure to substances that inactivate enzymes. Our model is based on the Lagergrens pseudo-first-order equation, the rate of chemical reactions, enzyme activity, and inactivation and was created to describe short-term changes in dehydrogenase activity. The main assumption of our model is that toxic substances cause irreversible inactivation of enzyme units. The model is able to predict the maximum direct toxic effect (MDTE) and the time to reach this maximum (TMDTE). In order to validate our model, we present two examples: inactivation of dehydrogenase in microorganisms in soil and activated sludge. The model was applied successfully for cadmium and copper ions. Our results indicate that the predicted MDTE and TMDTE are more appropriate than EC50 and IC50 for toxicity assessments, except for long exposure times.