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The aim of the present study was to investigate the effect of ageing of mechanochemically synthesized clay and its TiO2composite on the simultaneous removal of Pb(II), Cd(II), Cu(II) and Zn(II) ions from acidic aqueous solutions. The effect of different ageing times on sorption behavior of 1, 2, 10 and 19 h milled clays, as well as the clay composite with 20 wt% of amorphous TiO2(TiO2,a), was investigated. Ageing of the milled clays has stronger influence on the removal of Zn(II) and Cd(II) than on the removal of Pb(II) and Cu(II) ions. Ageing is particularly pronounced for the samples milled for 1, 2 and 10 h (which lost enhanced sorption properties after 3 months of ageing), and less pronounced for the samples milled longer period of time, 19 h (which retained sorption properties until 6 months). After these periods of time sorption capacities became nearly the same as the sorption capacities of the raw (unmilled) clay. The different responses on the ageing process of milled clays and composite are a consequence of microstructural changes such as recrystallization of montmorillonite phase and decrease in particle sizes. Slower ageing of composite compare to the milled clays can be related to the stabilization effect of TiO2particles which are dispersed in the clay matrix thus preventing recrystallization of the sample particles. Only a slight tendency towards the formation of agglomerations was noticed after 12 months of ageing. © 2014 Elsevier Ltd and Techna Group S.r.l.

The removal of Pb(II), Cd(II), Cu(II), and Zn(II) from aqueous solutions using (un)modified Serbian interstratified montmorillonite/kaolinite clay as an adsorbent was investigated. The clay was modified by mechanochemical activation for different time periods. X-ray diffraction patterns and particle size distributions were used to characterize the samples. Batch adsorption studies were conducted to optimize various conditions. The adsorption equilibrium was established within 60 min, and the maximum adsorption occurred in the pH range of 4.5–6.5. The milled clays exhibited greater equilibrium adsorption capacities (qe) for all of the metals than the raw clay. A difference in qe values for clays milled for 2 and 19 h could be observed only for initial concentrations (Ci) of ≥100 mg dm–3. This was related to the amorphization (i.e., exfoliation) of 19-h-milled clay particles. The adsorption equilibrium data of heavy metals on both raw and modified clays fit the Langmuir equation, although there were changes in the microstructure of the clay. The mechanochemical treatment of the clay reduced the amount of adsorbent necessary to achieve a highly efficient removal of heavy metals by a factor of 5. Thus, the mechanochemically treated interstratified clay can be considered as an efficient adsorbent for the simultaneous removal of divalent heavy metals.

In this paper, the impacts of some meteorological parameters on the SO2 concentrations in the City of Obrenovac are presented. The City of Obrenovac is located in the north-west part of Serbia on the banks of the River Sava. The observed source emission, the power plants TENT A and B are situated on the bank of the Sava River in the vicinity of Obrenovac. During the period from January to November 2006, the concentrations of sulfur dioxide in the air at 4 monitoring sites in Obrenovac were measured. It was noticed that the maximal measured daily concentrations of sulfur dioxide ranged from 1 μg m-3 (16th November, 2006) to 98 μg m-3 (29th January 2006) and lie under the maximal allowed concentration value according to the Serbian Law on Environmental Protection. The measured sulfur dioxide concentrations mostly showed characteristics usual for a daily acidification sulfur dioxide cycle, excluding the specificities influenced by the measuring site itself. Sulfur dioxide transport was recorded at increased wind speeds, primarily from the southeast direction. Based on the impact of meteorological parameters on the sulfur dioxide concentration, a validation of the monitoring sites was also performed from the aspect of their representivity., U radu su predstavljeni rezultati monitoringa koncentracije SO2 u vazduhu u Obrenovcu koji se nalazi na severozapadu Srbije na obalama reke Save. Posmatran je uticaj meteoroloških parametara na koncentraciju SO2 emitovanog iz termoelektrana TENT A i B koji se smatraju najvećim izvorima emisije. U periodu od januara do novembra 2006. godine praćene su koncentracije sumpor-dioksida u vazduhu na 4 merna mesta lokalizovana na različitim udaljenostima od izvora emisije. Maksimalne izmerene dnevne koncentracije sumpor-dioksida su se kretale od 1 μg m-3 (16. novembra, 2006) do 24 μg m-3 (29. januara, 2006). Izmerene promene koncentracija sumpor-dioksida uglavnom pokazuju uobičajene karakteristike dnevne acidifikacije ciklusa uz razlike koje potiču od osobenosti mernih mesta. Transport sumpor-dioksida zabeležen je pri pojačanom vetru prvenstveno iz jugoistočnog pravca. Na osnovu korelacionih odnosa između koncentracije sumpor-dioksida i odgovarajućih meteroloških parametara izvršena je karakterizacija mernih mesta u pogledu njihove reprezentativnosti za merenje sumpor-dioksida.