This work aimed to describe the synthesis and characterisation of two anionic Ru(III) complexes of the general formula Na[Ru - Cl 2 ( N -4-Cl-Ph-salim) 2 ] and Na[RuCl 2 ( N -3-Br-Ph-salim) 2 , their associated ligands, and determine their antioxidant activity. The ligands N- 4-Cl-phenylsalicylidenimine ( N -4-Cl-Ph-salimH, HL a ) and N- 3-Br-phenylsalicylidenimine ( N -3-Br-Ph-salimH, HL b ), Schiff bases, were synthesised from salicylaldehyde and chloroaniline or bromoaniline. The compounds were characterised us - ing IR spectroscopy and ESI ToF mass spectrometry. The following was confirmed: coordination of ligands on the Ru(III) centre, the molecular formulas, and the corresponding M − ions: [C 26 H 18 N 2 O 2 Cl 4 Ru] − ion, (m/z: 631.9173) and [C 26 H 18 N 2 O 2 Cl 2 Br 2 Ru] − ion, (m/z: 719.8283). The antioxidant activity was determined by the ABTS (2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) and DPPH (1,1-diphenyl-2-picrylhydrazyl) assays. In contrast to the ligands, both complexes proved to be strong scaven - gers of the ABTS and DPPH radicals with IC 50 (half maximal inhibitory concentration) values comparable to those of Trolox. As such, they present valuable candidates for further research related to their biological properties.

Efforts to reduce air pollution in developing countries may require increased use of biomass fuels. Even biomass fuels are a sustainable alternative to fossil fuels there is limited quantitative information concerning heavy metal content in their ashes. Therefore, this study focuses on the determination of the heavy metal concentrations in wood pellet ash obtained from the combustion of 10 pellet brans from Bosnia and Herzegovina and Italy, the effects of adding the ashes to soils, and the assessment of health risk assessment. Ash content was determined by gravimetric method. The amount and composition of ash remaining after combustion of wood pellets varies considerably according to the type of biomass and wood from which the pellet is made. Samples were prepared by wet digestion using HNO3, and heavy metals are determined by atomic absorption spectroscopy-flame and graphite furnace. The results showed that the lowest concentration in ashes was obtained for Co 0.01 mg kg−1 and the highest for Fe 571.63 mg kg−1. The Hazard Index (HI), calculated for non-cancerous substances for children was 2.23E−01, and the total Risk index was 4.54E−05. As for adults, HI was 1.51E−02, while the Risk index value was 3.21E−06. Human health risk calculated through HI and Risk index for children and adults associated with analyzed pellets is not of significant concern. The calculated enrichment factor and metal pollution index for wood pellet ashes indicate the risk of soil contamination with heavy metals. From this point of view, analyzed samples of ashes could be a serious contaminant of soil, so further monitoring is required.

Chemical precipitation is a useful conventional process to remove heavy metals from aqueous solutions. In this work, a waste sludge from the Solway process was used as a precipitation agent for the precipitation of Cu (II), Ni (II), Pb (II) and Zn (II) ions with an initial concentration of 50 mg/L. The results of the research showed that the waste sludge from the Solway process completely removed Pb (II) ions from the solution in the pH range of 8.39 -11.74, also good efficiency was shown in other cations. The maximum precipitation efficiency for Cu (II) is 99.890% at pH 10.98, Ni (II) 99.940% at pH 11.81, Zn (II) 99.616% at 10.1. Waste sludge is proved to be a good precipitate for cation separation.

In addition to soda, the Solway production process yields large amounts of waste sludge that contains a high percentage of CaCO3 and Ca(OH)2. In this paper, solid waste sludge from a soda factory in Bosnia and Herzegovina of a certain granulation was used to remove metal ions from the binary system initial concentrations of 500 mg/L. The research results showed that the precipitation efficiency for the binary system Cu - Ni was 99.810% at a pH of 11.42 for Cu2+ and 99.896% for Ni2+ at a pH of 10.86, while for the binary system Pb - Zn it was 99.84% at the same pH value of 10.64. This research has shown that it is very difficult to separate and remove metal precipitation from binary systems because the optimal pH for one metal does not correspond to another metal.