The rapid growth of the global population has increased the consumption of chicken eggs, leading to the generation of significant quantities of eggshell waste. The sustainable valorization of this biowaste represents an important environmental and resource management challenge. In this study, CaO was synthesized from waste chicken eggshells via calcination at 800 °C and evaluated as a green precipitating agent for the removal of toxic Pb(II) from aqueous solutions. The effects of key precipitation parameters, including initial pH, stirring speed, contact time, and CaO dosage, were systematically investigated. The results showed that the removal efficiency increased with increasing pH, mixing intensity, contact time, and CaO dosage, reaching a maximum Pb(II) removal of 90% under investigated conditions of initial pH 9, stirring speed of 500 rpm, contact time of 15 min, and CaO dosage of 500 mg. In the presence of the competing ion Fe(III), the removal efficiency further increased to 99.99%, indicating a potential synergistic effect in the precipitation process. FT-IR analysis confirmed the successful formation of CaO and revealed significant spectral changes after Pb(II) precipitation, including shifts and disappearance of characteristic absorption bands, indicating the formation of insoluble hydroxide and carbonate phases. These findings demonstrate that eggshell-derived CaO is an effective and environmentally sustainable material for Pb(II) removal from aqueous media and represents a promising approach for the valorization of eggshell waste.

The paper deals with the assessment of risks related to drinkingwater quality, the analysis of physicochemical and microbiological parameters that are key to assessing human safety and health. Through a detailed analysis of these parameters, the paper investigates whether the appropriate physicochemical and microbiological parameters are within the framework defined by the regulation, and whether they may pose a threat to human health.Physicochemical parameters include aspects such as pH values, electrical conductivity, oxidizability, concentrations of various chemical compounds (such as nitrates, nitrites, ammonia, chlorides, heavy metals, etc.) and represent the degree of pollution bychemicals that may pose a threat to human health, while microbiological parameters relate to the presence of pathogenic bacteria, viruses and parasites that can cause various diseases in humans.The paper uses data from laboratory analyses of water samples monitored at 32 locations in the Tuzla Canton during two seasons. Through this assessment, the paper highlights the importance of regular monitoring of drinking water quality, as well as the implementation of adequate measures to prevent potential health hazards for users.KEYWORDS:public water fountains, physical-chemical analysis, microbiological analysis

Cadmium is recognized as one of the most hazardous heavy metals, ranking among the top ten in terms of toxicity. With the growing industrial reliance on cadmium for various manufacturing processes, concerns have risen within the scientific community regarding its presence in wastewater and the challenges associated with its removal. This research investigates the potential for removing Cd(II) ions from a synthetic aqueous solution by utilizing NaHCO3as a precipitating agent. The removal efficiency exceeded 99%, with the most effective conditions identified as: pH 8, a stirring speed of 300 rpm, a stirring duration of 5 minutes, and a precipitation agent of 90 mg. Additionally, removal efficiencies of 96.256% and 91.234% were achieved at cadmium concentrations of 150 mg/L and 300 mg/L, respectively. The removal of Cd(II) ions was found to be more efficient in a mixture of metals, with an efficiency above 98%, compared to when individual metals were considered in isolation.KEYWORDS:Cd(II) ions, most effective conditions, removal efficiency

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%.

Zeolites are particularly suitable adsorbents due to their pronounced ion-exchange capacity, high efficiency, stability, and the ability to be regenerated and reused multiple times. Their characteristic crystalline structure enables the exchange of sodium, potassium, calcium, and magnesium ions with heavy metal cations present in solution. For the successful application of zeolites under industrial conditions, a detailed understanding of the adsorption mechanisms and kinetics is essential, as it allows for process optimization and identification of key limiting factors. Experimental approaches typically involve varying the adsorbent mass and the initial concentration of the adsorbate in order to determine the optimal conditions for achieving maximum adsorption efficiency. A moisture content of 3.95% and ash content of 91.28% indicate high thermal and structural stability of the zeolite, while the presence of Na⁺ ions (0.2435 mmol g⁻¹) in the material confirms that cation exchange is the dominant mechanism. Adsorption of heavy metals was investigated in a batch reactor at initial concentrations of 10, 50, and 100 mg/L, at a constant temperature of 298 K, with stirring at 200 rpm for 60 minutes. The amount of adsorbed ions was found to increase with rising equilibrium concentrations in the solution. Metal ion concentrations were determined using atomic absorption spectrophotometry. The highest adsorption was observed for Cu(II) ions within 5 minutes, while Cr(III) and Ni(II) ions reached their maximum adsorption within 20 minutes. The experimental data fit best to the Langmuir isotherm model, and the adsorption efficiency followed the order: Cu(II) > Cr(III) > Ni(II).

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.

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.

In accordance with consumer requirements, the water must be adequately purified, and the corresponding parameters within the defined values. Various methods are used for this purpose, of which the ion exchange method can be highlighted as the simplest, most efficient and economically profitable. Ion exchange is a reversible process of ion exchange between a solid phase and an electrolyte solution. The ion exchanger is a macromolecular insoluble material that has chemically bound electrified groups and mobile, oppositely charged ions that compensate for this electrification. Ion exchangers are usually used in the form of compact or granular beds that fill the column through which the solution with the ions to be exchanged flows.They usually contain phenolic, carboxylic, sulfonic amino and other groups, which is why the treatment also results in decarbonization, softening, demineralization and denitrification of water. As the assessment of water quality is based on the most significant physico-chemical parameters, the aim of the work is the analysis of drinking water before and after treatment with an ion exchanger.For this purpose, organoleptic parameters such as smell, taste and color were first analyzed. After that, physico-chemical parameters were analyzed: pH values, electrical conductivity, m-alkalinity, p-alkalinity, water hardness, organic matter content, chloride content, iron and manganese content. An ion exchanger based on resin was used, which after use was regenerated by washing with NaClsolution.The analysis of the water sample, before and after the ion exchange treatment, showed that the treatment process was effective and that the decarbonization and softening of the water was carried out, whereby the water was categorized as soft water (water <9⁰dH).The analyzed water is tasteless, odorless and colorless before and after treatment. The results of the analysis showed that all the values of the analyzedphysico-chemical parametersare in accordance with the Rulebook on the Healthiness of Drinking Water(Official Gazetteof Federation of Bosnia and Herzegovina No.40/10) arebelow the maximum allowed values. KEYWORDS:water, ion exchange, physical-chemical parameters; water treatment

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.