Polycrystalline Zn-Mn-O samples with nominal manganese concentration x = 0.01 and 0.10 were synthesized by a solid state reaction route using (ZnC(2)O(4)·2H(2)O)(1-x) and (MnC(2)O(4)·2H(2)O)(x). Thermal treatment of the samples was carried out in air at temperatures of 673, 773 and 1173 K. The samples were investigated by x-ray diffraction, thermogravimetry, differential thermal analysis, transmission electron microscopy, magnetization measurements and electron paramagnetic resonance. Room temperature ferromagnetism is observed in Zn-Mn-O samples with x = 0.01 thermally treated at low temperatures (673, 773 K). It seems that the ferromagnetic phase could originate from interactions between Mn(2+) ions and acceptor defects incorporated in the ZnO crystal lattice during the thermal treatment of the samples.

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This study investigates the use of hard coal as an adsorbent for removal of mineral oil from wastewater. In order to determine the efficiency of hard coal as an adsorbent of mineral oil, process parameters such as sorption capacity (in static and dynamic conditions), temperature, pH, contact time, flow rate, and chemical pretreatment were evaluated in a series of batch and continuous flow experiments. There were significant differences in the mineral oil removal for various pH values examined. The adsorption of mineral oil increased as pH values diverged from 7 (neutral). At lower temperatures, the adsorption was notably higher. The wastewater flow rate was adjusted to achieve optimal water purification. Equilibrium was reached after 10 h in static conditions. At that time, more than 99% of mineral oil had been removed. At the beginning of the filtering process, the adsorption rate increased rapidly, only to show a minor decrease afterwards. Equilibrium data were fitted to Freundlich models to determine the water-hard coal partitioning coefficient. Physical adsorption caused by properties of the compounds was the predominant mechanism in the removal process.