Lucija Foglar

Properties of UV protective films of poly(vinyl-chloride)/TiO2 nanocomposites for food packaging

This work studies the UV protection properties of poly(vinyl-chloride) (PVC) nanocomposites. A functional property of UV protection is achieved by adding the active component (titanium dioxide (TiO2) or titanium dioxide modified with silver nitrate and copper nitrate) to the PVC matrix. PVC nanocomposites were prepared by extrusion and then pressed into films. Prepared PVC nanocomposites were characterized by thermogravimetric analysis, UV–Vis spectroscopy, X-ray diffraction and scanning electron microscopy. The mechanical properties and antimicrobial activity were also studied. The results show that PVC nanocomposites’ thermal stability is improved in relation to a pure PVC polymer. The thermal stability and antimicrobial efficiency increase when higher silver nitrate content is used. The sample prepared with silver and copper nitrate shows the best thermal stability due to a modified mechanism of thermal degradation. Samples where nanoparticles are homogeneously dispersed in the polymer matrix show good mechanical properties. The results also show that adding the active component TiO2 modified with silver ions contributes to the improved UV protection property of nanocomposite materials.

The removal of arsenic from water with natural and modified clinoptilolite

The presence of increased arsenic concentrations in Eastern Croatia is a consequence of the geological composition of the soil. Because of its known harmful effects, arsenic removal is of high importance and adsorption represents an attractive and economically efficient approach to arsenic removal. The use of zeolites obtained from the Donje Jesenje deposit, Croatia (CZ) and the Zlatokop deposit in Vranjska Banja, Serbia (SZ) in Na- and Fe–Na-modified forms was investigated in order to effectively remove arsenate and arsenite from aqueous solutions. The adsorption kinetics of arsenic was studied as a function of the initial arsenate and arsenite concentrations (30–300 μg · L−1), equilibration time (3–48 h), pH (5–10) and in the presence of sulfate and phosphate at initial concentrations of 0.2–0.5 mg · L−1. In order to estimate sorption constants designating the sorption capacity and affinity of the zeolites samples, the experimental results were fitted to the Langmuir and Freundlich sorption isotherms. Desorption tests conducted with 1–3 mol · L−1 HCl indicated that arsenate sorption was irreversible. The results obtained indicated that use of the Serbian zeolite in the Fe–Na-modified form (Fe–Na-SZ) was favourable for arsenate removal from water containing up to 30 μg As · L−1.

Impact of ultrasound application on oxidative desulphurization of diesel fuel and on treatment of resulting wastewater

The ultrasound-assisted oxidative desulphurization (UAOD) process of diesel fuel has gained growing attention due to the strict regulation of sulphur content in the fuel. The goal of the present study was to investigate the impact of ultrasound (US) application for oxidative desulphurization (ODS) of hydrocarbon fuels and for the subsequent treatment of produced wastewater, since sonochemical processes are a new and interesting area of research with wide application in the field of environmental engineering. For that purpose, the model diesel fuel with initial sulphur concentration of 1220–3976 mg l−1 was used for ODS and UAOD tests, and hydrogen peroxide/acetic acid was applied as the oxidant/catalyst system, respectively. The comparison of the process performance revealed that US significantly reduced the oxidation reaction time. The conversions of dibenzothiophene during 30 min of ODS and UAOD tests were 36% and 87%, respectively. Moreover, subsequent extraction with acetonitrile resulted in the final sulphur removal of 96.5%. The obtained results clearly indicated that UAOD process is beneficial for effective sulphur removal from the model diesel fuel. Furthermore, subsequent experiments included the application of the sono-Fenton process for resulting wastewater treatment. Monitoring of dibenzothiophene sulphone concentration and total organic carbon during the sono-Fenton treatment of wastewater revealed the decrease of 70–75% and 53–66%, respectively. The hypothesis on the possibility of degradation of dibenzothiophene sulphone by •OH radicals was confirmed by observed generation of benzoic acid and aliphatic carboxylic acids during experiments. Accordingly, the wastewater was purified to a satisfactory degree, enabling the reuse of treated water.

Continuous-flow biological denitrification with zeolite as support for bacterial growth

Zeolite particles with bacterial culture (Bio-NPC) were used for nitrate removal from surface water (SW) and effects of Bio-NPC, and the methanol amount and the pH value of SW were investigated in the batch reactor and the process was then monitored in the continuous-flow stirred reactor. The application of Bio-NPC particles (10%w/w) in the batch reactor was efficient for the removal of 100mgNO3‐N/L from the SW, and the addition of methanol was optimal at CH3OH/N ratio of 2.5:1. The process was stable in the pH range of 5.85‐8.03, but the highest denitrification rate was obtained at the pH value of 7.13. In the continuous-flow stirred reactor, nitrate removal was investigated at different hydraulic retention times (HRTs) (37.04, 23.26, 10.53, 2.33 and 1.32h) and the efficient nitrate removal was achieved even at HRT of 1.32h with nitrate and organic removal higher than 99 and 79%, respectively. The volumetric denitrification rates during the first eightdays of continuous flow were in the range of 39.2‐51.28mgNO3‐N/Lh and then it fluctuated within the range of 63.47‐ 79.90mgNO3‐N/Lh. The use of Bio-NPC was demonstrated as an efficient method for complete nitrate removal from the surface water.