Bentonite clay is a valuable material in various process industries, thanks to its specific properties. Easy availability, low cost and their effectiveness are the main factors that have made bentonite adsorbent in the edible oil industry. The textural characteristics of bentonite clay play an important role in its performance. In its natural form, as an aluminosilicate material, bentonite does not show satisfactory sorption and catalytic properties, and it needs to be activated. The main goal of this research is to increase the adsorption capacity of bentonite clay by modifying its properties by treatment with organic acid. Activation of bentonite clay in the experimental part was performed with different concentrations of sulfuric acid. The chemical composition of the natural bentonite sample was determined using XRF alongside the influence of acid activation of bentonite with H2SO4 on the surface characteristics (such as specific surface area, pore volume and average pore diameter, adsorption capacity and isotherm type) of bentonite clay. The XRF analysis of the natural bentonite, which contains 56.35% SiO2 and 19.82% Al2O3 as its primary components, confirms that it is an aluminosilicate material. Except for SiO2, which recorded a consistent increase in quantity from 56.35% to 74.15% with increasing acid concentration, the composition of other components, after activation slightly decreased or remained the same. The acid concentration that yielded the highest increase in specific surface area, as measured by the Brunauer–Emmett–Teller (BET) method, was selected as the optimal concentration for activating bentonite. The specific surface area almost tripled (from 95.519 m2/g to 346.467 m2/g)) by activation with 15% sulfuric acid, with an activation time of 3 hours and a bentonite: acid ratio of 1:5. The research results show the effectiveness of acid modification in terms of improving the characteristics of the porous structure of bentonite samples.

Water hardness and deposition of incrustation is a problem in households and industry. In this regard, several technologies have been developed with the purpose of water softening and preventing the deposition of incrustation. The ion exchange method is the most commonly used method and is considered a conventional method. However, due to the shortcomings of this method, there is a need to develop adequate alternative methods. The potential of the method using biosorbents such as moss Leucobryum glaucum and Spaghnum peat moss for the purpose of removing water hardness has recently become the subject of intensive research with growing interest. In this study, the method using Leucobryum glaucum as a biosorbent was tested and a comparison was made with the conventional method and previously conducted studies that used other biosorbents.

In this article, the corrosion inhibition of steel DIN 2391 St 37-4 in acidic medium 5% H2SO4 with and without the presence of eco inhibitors of leaf (Petroselinum Sativum) was examined. Inhibitory properties of parsley leaves (Petroselinum Sativum) on steel DIN 2391 St 37-4 were examined by potentiodynamic polarization - Tafel extrapolation, and FTIR method in order to categorize the oxide layer. The test was performed in static medium and with stirring at 600 rpm. By Tafel extrapolation based on changes in corrosion potential, the inhibitor behaves as mixed. Increasing the concentration of inhibitors increases the efficiency of inhibition. Corrosion processes are inhibited by adsorption of organic matter on the surface of steel DIN 2391 St 37-4, forming a film. The obtained results indicate that parsley leaf (Petroselinum Sativum) is an effective eco inhibitor for the tested steel in 5% sulfuric acid.

In this research, the results of bentonite characterization (pH value of bentonite suspension, point of zero charge, cation exchange capacity,  SEM, XRF, DTG) are presented. The results of lead (II) removal efficiency at initial lead (II) concentrations of 200, 300 and 400 mg/L, and biosorbent dosage of 1 gram in 50 ml of lead(II) solution,  are also presented, as well as the values of the Freundlich and Langmuir constants from the Freundlich and Langmuir adsorption isotherms. The obtained results showed that removal efficiency is high for all three examined initial lead (II) concentrations, and it is above 99%. The lead (II) removal efficiency slightly decreases with an increase in initial lead concentration. Experimental data obtained from adsorption experiment with contact time of 2.5 minutes, stirring rate 100 rpm, temperature 250C and pH value 5 are better fitted with the linearized Langmuir equation isotherm, giving an R2 value closest to unity (0.9994), than to linearized Freundlich equation (0.9886).

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%.