The expansion of industrialization and household use of synthetic compounds has generated significant wastewater containing toxic heavy metals. In developing countries, this wastewater is often discharged untreated due to the high cost of advanced treatment technologies. This study used sodium hydroxide as a low-cost, readily available precipitation agent to remove selected metal ions from mono- and binary-component solutions. Unlike most studies focusing on pH and initial ion concentration, this work investigated operational parameters such as stirring speed (0–800 rpm) and time (0–30 min) while keeping pH and concentration constant. Results showed that higher stirring speeds and longer stirring times enhanced metal ion removal, with Pb(II) efficiency increasing from 86.64% at 100 rpm to 94.33% at 800 rpm. In binary mixtures, similar improvements were observed. These findings highlight that simple, low-cost operational adjustments can significantly improve metal removal efficiency, which is particularly relevant for water treatment in resource-limited settings. The two-way ANOVA without replication showed that the type of metal or mixture had a significant effect on removal efficiency, while stirring speed and time within the investigated ranges did not have a statistically significant effect. These results indicate that differences in removal efficiency are primarily due to the metals’ chemical properties rather than the operational parameters.

Rapid industrialization has led to the creation of large amounts of wastewater containing various pollutants, among which heavy metals stand out. Heavy metals such as Cd (II) ions cause serious chronic diseases and even death if they are present in high concentrations. Therefore, this manuscript investigates the possibility of Cd (II) ion removal by precipitation method using Ca(OH)2. In order to optimize the precipitation process, the following were investigated: initial pH, initial concentration of Cd (II) ions, dose of added Ca(OH)2, stirring speed and contact time, as well as the influence of competing ions on the removal efficiency of Cd (II) ions. The optimization of the precipitation process was performed by varying one operational parameter at a time, while keeping all other parameters constant. Results of Cd(II) ion removal efficiency and optimal conditions are: pH 5 (99.961%), stirring speed of 0 rpm (99.985%), contact time metal-precipitant 5 minutes (99.965%), added dose of Ca(OH)2 60 mg (99.965%). Complete removal of Cd (II) ions was achieved at a Cd(II) ion concentration of 10 ppm, and high removal efficiency was achieved at concentrations of 50-300 ppm (98.231-99.994%). The removal efficiency of over 99% of Cd (II) ions was achieved during individual tests of ion competitiveness. Therefore, it can be concluded that under the tested conditions, Ca(OH)2 is an effective agent for removing Cd (II) with an efficiency above 99%.

Optimal process conditions for carbonate precipitation of selected heavy metal ions were tested in laboratory conditions using Na2CO3. To the prepared synthetic monocomponent and binary multicomponent solutions of heavy metals with initial concentrations of 500 mg/L, Na2CO3 was added in certain doses at selected mixing speeds (0, 100, 300 and 800 rpm) and mixing time (0, 15, and 30 minutes). The results show the removal efficiency at optimal mixing speeds for monocomponent metal solutions were: Cu(II) 96.394% (300 rpm), Ni(II) 94.594% (0 rpm and 800 rpm), Pb(II) 75.968% (0 rpm ), Zn (II) 99.311% (0 rpm). In binary multicomponent mixtures Cu(II)-Ni(II) and Pb(II)-Zn(II) the removal efficiency results at optimal mixing speeds were: Cu(II) 96.394% (100 rpm), Ni(II) 95.528% (800 rpm), Pb(II) 99.536% (300 rpm), Zn(II) 98.945% (100 rpm). Also, the results of the efficiency of heavy metal removal due to the influence of the contact time of the precipitant and heavy metal ions in monocomponent solutions show the following values: Cu(II) 99.940% (0 min), Ni(II) 94.612 % (0 min), Pb(II) 77.925 % (15 min), Zn(II) 99.324% (30 min), while in binary multicomponent mixtures Cu(II)-Ni(II) and Pb(II)-Zn(II) they were for Cu(II) 96.247% (30 min), Ni(II) 95.521% (0 min), Pb(II) 99.350% (30 min) and Zn(II) 98.944% (0 min). Examination of the influence of the mixing speed of monocomponent solutions showed that the efficiency of removing heavy metal ions was in most cases the best without mixing. Effect of metal-precipitant contact time on the efficiency of heavy metal ion removal showed that in half of the examined metals, the optimal values ​​were chosen as the best (0 and 30 min). It can be concluded that this method based on chemical precipitation using Na2CO3 with optimal parameters such as contact time and mixing speed, can be used in the treatment of industrial wastewater.

Nigella sativa is a herb that has been used for centuries to treat various ailments, including infectious diseases. The aim of this work was to show in laboratory conditions the influence of different temperature regimes and methods of storage of Nigella Sativa oils on their physicochemical properties and microbiological stability. Analyzes have established that the temperature and method of storage have a significant influence on the change in the quality of the oil, especially when it comes to the total acidity of the oil and the peroxide value, where the values increased with the time of storage. The lowest obtained value for the peroxide number was at the first measurement, Pb = 9.99, which meets the prescribed standards for safe use, then the highest obtained value was 34.47 for the sample that was constantly exposed to the sun in a bright bottle. Also, the values of the iodine number increased with time, where the lowest value obtained was 14.56, and the highest was 102.48. Therefore, it is extremely important that the oil is stored in suitable packaging in dark glass bottles, and that it is protected from direct sunlight and high temperatures.

New accurate, precise, and sensitive spectrophotometric method were developed for the assay of L-ascorbic acid in pharmaceutical preparations. The determination of L-ascorbic acid was based on its oxidation by potassium peroxydisulfate in the presence of Ag(I) as a catalyst. The molar absorptivity of the proposed method was found to be 8.61 · 103 L mol-1 cm-1 at 248 nm. Beer's law was obeyed in the concentration range of 0.46–20.0 μg mL–1. Other compounds commonly found in vitamin C and multivitamin products did not interfere with the determination of L-ascorbic acid. The proposed method was successfully applied for the determination of L-ascorbic acid in pharmaceutical formulations. The results obtained with the proposed method showed good agreement with those given by the titrimetric method using iodine.

Physical chemical milk is an emulsion of milk fat in an aqueous solution of proteins, milk sugar and mineral salts. The high molar conductivity of goat milk samples compared to cow's milk indicates a high content of mineral substances. That goat milk is rich in total proteins is also indicated by the protein content in the samples, which are higher than the cow's milk samples. However, higher fat content was recorded in cow's milk samples, which also results in higher surface tension of cow's milk. The freezing point and refractive index of goat milk are higher compared to literature data and cow milk samples. The acidity of goat's milk comes from the acidic properties of casein, citrate, phosphate, etc. it is lower than cow's milk and is in accordance with literature data. The viscosity of pasteurized goat's milk at all temperatures is also higher than that of cow's milk.

Waste water in the galvanic process contains high concentrations of heavy metals that pose a direct danger to humans and the environment. Conventional methods for their removal are quite expensive and generate a large amount of waste. The development of new and improvement of existing methods for the removal of heavy metals from galvanic wastewater are the subject of many studies. Compared to other purification methods, the adsorption is becoming an increasingly popular method of wastewater purification, especially if the adsorbent is cheap, easily available and does not require any other treatment before use. Therefore, the aim of the work was to investigate the possibility of using natural bentonite for the removal of heavy metal ions from multi-component water systems of the galvanic industry. For this purpose, the physico-chemical characterization of natural bentonite was performed, and then the influence of pH value, time and temperature on the adsorption efficiency was examined. The results of adsorption showed that natural bentonite can be used as an adsorbent for the removal of heavy metal ions from waste galvanic waters, and that at pH 5 it achieves the maximum removal efficiency for Cu(II):Cr(III):Ni(II) ions in the percentage ratio 100 : 99.990 : 99.998. The results showed that the highest removal efficiency for Cu (II) ions was achieved in the first 10 minutes, and 20 minutes for Cr (III) and Ni (II) ions. The maximum efficiency of Cu (II) removal was achieved at all temperatures, while for Cr (III) 99.99% and Ni (II) 100% maximum efficiency was achieved at 35°C, which indicates that the adsorption process is endothermic. The experimental results of the adsorption of Cu (II) metal ions are in good agreement with the Langmuir and Freundlich theoretical models, while for Cr (III) and Ni (II) ions they are in better agreement with the Langmuir adsorption model.

Medicinal plants have become an increasing subject of interest worldwide due to the large amount of biologically active substances that have potential beneficial health properties. One of the more interesting popular medicinal plants is hawthorn (Crataegusspp.), a deciduous branched shrub that is increasingly used for health purposes. Various parts of this plant, including berries, flowers and leaves, are rich in nutrients and beneficial bioactive compounds that are effective in the treatment of numerous diseases. Honey is a natural sweetener produced by bees from plant secretions. Known for its nutritional and medicinal values, it gives strength to the body, which is why it is indispensable in the human diet. The combination of these two ingredients represents a significant source of vitamins and minerals in daily use, but also for use in various pharmaceutical and medical purpose. Taking into account all of the above, the aim of the work is to test samples of the mixture of honey and hawthorn in different proportions and determine the physical and chemical characteristics: pH value, electrical conductivity, refractive index, viscosity, water activity, HMF, DPPH. Based on the analysis, appropriate conclusions will be drawn and more information will be obtained about their quality and possible use as a food supplement. On the basis of the conducted analyses, it can be concluded that the parameter values are within the permitted limits defined by the Rulebook (Official Gazette Bosnia and Herzegovina No. 37/09). The analysis of the mentioned parameters showed that the chemical composition of the sample plays a major role in the value of the measurement results, and that Sample III has the best antioxidant properties. KEYWORDS:physicochemical characteristics; honey; hawthorn (Crataegus spp.);mixture; food suplement

Various synthetic and natural antioxidants are used to reduce oxidation and its negative impact on the oil during the food frying process. Considering that some studies show the negative impact of synthetic antioxidants on the health of consumers, natural alternatives are being used more and more. BHA and BHT are synthetic antioxidants that are widely used in the food industryand a large number of natural compounds such as phenols, anthocyanins, flavonoids, vitamins, etc. show antioxidant properties. In this study, the antioxidant capacity of oregano and rosemary essential oil was tested and compared with the antioxidant capacity of BHA and BHT. The antioxidant capacity was evaluated by the removal of DPPH radicals and by iron reduction (FRAP). The results of this study showed that the studied essential oils exhibited antioxidant capacity. These oils have a high antioxidant capacity, however, compared to synthetic antioxidants, they show a significantly lower antioxidant capacity but they can be used as natural antioxidants during food processing. KEYWORDS:antioxidant capacity; essential oils; synthetic antioxidants; lipidoxidation

pH represents the concentration of free H+ in pine needles extracts (PNE) and is therefore an important initial parameter in quality control. Electrical conductivity and pH of samples of fresh and stored for 20 days of PNE with black cumin oil and olive oil had values of 0.00 due to the encapsulation of water molecules, pH and electrical conduction was not possible. The pH of the other samples was in a weakly acidic environment because the pH of natural pine needles is 3.8. Electrical conductivity values in all samples except pine needle extract and honey increased during storage. By monitoring the parameters of pH and electrical conductivity in the quality control of PNE, it gives us a significant insight into the physical state of the phases and the way of storage.