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.

The samples of stinging nettle were collected during June in the Tuzla region. Aqueous extracts were prepared from fresh and dried leaves in order to determinate and compare content of bioactive components and antioxidant potential. Conventional soxhlet, ultrasound assisted extraction and traditional maceration extraction were used as extraction methods. Quantitative determination of phenols and flavonoids was carried out using spectrophotometric methods. Antioxidant activity of nettle aqueous extracts was determined using ferric reducing antioxidant power and DPPH free radical scavenging activity. Extracts obtained by Soxhlet extraction showed the highest total phenolic and flavonoid content and expected the highest antioxidant capacity, while extracts obtained by maceration gave the lowest results. KEYWORDS:stinging nettle extract;bioactive components;extraction;antioxidant

Various toxic heavy metals have become hazardous to human health as well as the environment. This research has been focused on a biosorption/bio-removal process of chromium (III), copper (II) and lead (II) ions from an aqueous solution by utilizing lignocellulosic biomass of Citrus limon peel (CLP) powder. CLP powder biomass was selected based on dietary fibre components having greater potential to remove target heavy metal ions in order to purify wastewater by following the eco-friendly biosorption method. At optimum conditions, the observed maximum removal efficiency of 97.47, 87.13 and 95.71% for Cr, Cu and Pb ions, respectively, was observed. An investigation has been made as a work of pH, CLP amount and temperature. The presented bio-removal processes by prepared CLP biosorbent manifested as a temperature-independent. Langmuir isotherm model was found an excellent fit of the isotherm data for tested systems with the calculated biosorption capacities of 111.11 (Cr), 76.92 (Cu) and 100.00 (Pb) mg/g. The positive ΔH values for selected target heavy metal ions, except lead ions, confirmed that the reaction was spontaneous and endothermic. A cooperative mechanism of second-order and intraparticle diffusion models during the adsorption processes of all three target ions was established with a higher coefficient of determination and more closely anticipated take-up (adsorption capacity). Furthermore, the interaction of -OH and -COOH functional groups of CLP that have a major role in the removal of Cr, Cu and Pb ions from single-ion aqueous solution and/or a surface biosorption was confirmed based on the results presented by SEM-EDS and FTIR analysis. Analysis from XRD revealed peak corresponding to amorphous cellulose type I as observed by FT-IR analysis.

The wastewater containing Cd, Co, Fe, Cu, Cr, Mn, Ni and Pb ions are trace metal pollutants. Water pollution caused by increment in industrialization and overpopulation reveals a major threat to human health. Adsorption is recognized as the effective and optimum method to remove water contaminations. The amorphous and porous form of silicon dioxide is silica gel widely used as an adsorbent. It can absorb moisture with traces of the target heavy metal ions. This research elaborates a simplistic, and reliable preconcentration column method highly developed for the determination of Cd2+, Fe3+, Co2+, Cr3+, Cu2+, Mn2+, Pb2+ and Ni2+ ions in model solutions and real water samples by flame atomic absorption spectrometry (FAAS). The proposed operation depends on the retention of the target ions from buffered model solutions on a silica gel filled up a column modified with vanadium(V) oxide sorbent followed by their desorption. SiO2/V2O5 is an efficient adsorbent due to its low cost, eco-friendly and high availability. The adsorbent morphological and interfacial physicochemical characterization was done using scanning electron microscopy, and Fourier transmission infrared spectroscopy, respectively. The 2.92 value achieved for the point of zero charges supports the experimentation for the heavy metal efficient adsorption. Quantitative recoveries were achieved at pH 10 with 50 mg of SiO2/V2O5 mass and adsorption capacity ranged from 28.96 μmol/g (Pb) to 214.86 μmol/g (Fe) with 1114.79 μmol/g in total. Simultaneous preconcentration effect was determined by the interference cations on the sorbent. The LOD varies from 8.42 to 50.56 μg/L and LOQ is achieved from 20.06 to 72.41 μg/L of 15 blank solutions. The developed preconcentration procedure was adequately implemented for the simultaneous analysis of eight metallic ions content in local river samples. The developed vanadium(V) oxide incorporated with silica gel is practicable as an economical and effective adsorbent to eliminate metallic ions from a liquid solution.

In this research, the possibility of using Ca(OH)2 in the form of commercial hydrated lime as a catalyst for the methanolysis of refined rapeseed oil was evaluated. Characterization of unused catalyst was performed by SEM-EDS, laser diffraction, XRF, BET, XRD and TG/DTG methods, and vegetable oil was analyzed for physicochemical characteristics. Within methanolysis, the effects of catalyst loading, reaction temperature and reaction time on methyl ester yield, density and viscosity of biodiesel, as well as the possibility of catalyst reuse were investigated. The obtained results showed that hydrated lime is an efficient catalyst for transesterification of vegetable oil, whereby the use of 3 wt% of catalyst relative to oil weight, at temperature 60℃ and mixing rate 1000 rpm after 120 min of transesterification reaction achieved a yield of methyl esters 98.76%. With three reuses of hydrated lime, without intermediate washing and regeneration procedures, the yield of rapeseed oil methyl ester remained above 90%.

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.

Abstract This study reveals novel data on adsorptive removal of Pb(II) from single metal solution, as well as from multi-metal solution containing Cd(II), Co(II), Cr(III), Cu(II), Fe(III), Mn(II), Ni(II) and Zn(II) ions along with Pb(II) using inorganic SiO2–MoO3 sorbent in a batch system. The results of multi-metal solution system were strongly pH-depended and due to occurred precipitation of Fe(III) in the form of hydroxide. The parameters affecting the sorption efficiency (contact time, sorbent dosage and initial analyte concentration) were evaluated for single solution system. The optimal conditions for SiO2–MoO3 sorbent indicated high affinity toward Pb(II) ions within following process parameters; pH value 3, sorbent dosage 50 ​mg and contact time 60 ​min for maximum Pb2+ concentration of 100 ​mg/L. The adsorption data for Pb(II) utilizing SiO2–MoO3 best fit to pseudo-second-order kinetic model (R2 ​= ​0.9998) and Langmuir isotherm model (R2 ​= ​0.9320) with an adsorption capacity of 222.20 ​mg/g and Reff >95%. According to thermodynamic study, the adsorption process is feasible, spontaneous and exothermic (ΔG ​= ​−18.6 ​kJ/mol, ΔH ​= ​−7.5 ​kJ/mol and ΔS ​= ​37.32 ​J/mol K). The results of present study demonstrated that SiO2–MoO3 material as a renewable sorbent for Pb(II) removal.