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Mesoporous silica particles were prepared from highly basic sodium silicate solutions, having different silica modulus and SiO2 concentrations, by adding sulphuric acid at different temperatures. Pore structure of prepared silica particles (aggregates) is strongly influenced by processing conditions and easy controllable in broad range of the specific surface area, pore size, pore volume and size distribution. It is shown that there is a clear correlation between volume of absorbed oil and processing parameters used in preparation of silica aggregates. Thus, oil absorption is higher in the samples prepared from sodium silicate solution with higher SiO2 concentration and at higher synthesis temperature.

This paper presents the results of a survey carried out in 89 operating objects with food (restaurants, fast food restaurants, distribution centers, stores, etc.) in Bosnia and Herzegovina. The questions that the employees have been asked (owners, managers, workers) were related to good hygiene practices, good manufacturing practices and HACCP principles, and general knowledge about the production and preparation of food. The survey covered 520 people. Displayed knowledge level requires fast actions in taking a series of measures to improve it. The best and quickest results will be achieved by organizing a series of seminars tailored to the needs of individual sectors in the fi eld of catering services.

The aim of this research was to determine the influence of the SiO2/Al2O3 molar ratio on the specific commercial properties of NaA zeolite subtypes as final market products (4A,4A-AG and 4A-MS) under the real production and process conditions. The value of the SiO2/Al2O3 molar ratio, so-called silicate module, was set as independently variable and the effect on the physical and chemical properties of each of the subtypes of NaA zeolites was examined.The paper investigates how the SiO2/Al2O3 molar ratio affects specific properties of NaA powders, namely the ion exchange capacity, oil adsorption capacity and water adsorption capacity. Some previous theoretical and experimental studies have shown that the molar ratio plays a crucial role in the formation of these very similar but for final application different subtypes of NaA zeolite. The experimental part of this work was performed and tested in real production conditions, which can be considered as an advantage in relevance to the obtained results. Various analytical and instrumental testing methods were used for the analysis of the obtained powders, including SEM, XRD and PSD analyses.

Polazeći od I i II zakona termodinamike, primjenjenog upovratnim procesima, a kod kojih je postignuta ravnoteža pritiskai temperature, u radu je izveden izraz za ukupni maksimalnizaprmenski rad zatvorenih sistema. Radi potpunije interpretacijeove problematike za dva karakteristična slučaja, dat je grafičkiprikaz u p-v dijagramu, gdje se na očigledan način zapaža da senajveći rad širenja sastoji iz izenropskog i izotermnog rada kao irada protiv pritiska okoline. Na bazi izvedenog izraza, koristećiodgovarajuće termodinamičke relacije, izveden je izraz zaspecifični maksimalni rad koji je pogodan za analizu. Dobijeni izrazje posmatran kao dvodimenzioni problem odnosno kao funkcijadvije promijenive: početni pritisak i početna temperatura kaoprimarni parametri. Primjenom matematičke analize dokazano jepostojanje minimuma posmatrane funkcije, i dato njeno grafičkopredstavljanje u prostornom koordinatnom sistemu. Detaljnommatematičkom analizom pokazano je da u opštem slučaju funkcijamaksimalnog rada geometrijski predstavlja jednu konkavnupovršinu u prostoru.Radi efikasnijeg rješavanja i analizepostavljenog problema, složena funkcija maksimalnog radaposmatrana je kao dvije funkcije sa jednom promjenljivomodnosno dvodimenzioni problem sveden je na dvajednodimenziona problema. Pokazano je da i kodjednodimenzionih problema takođe postoji tačka u kojoj jemaksimalni rad minimalan a različit od nule. Na kraj rada, date sumogućnosti primjene kompleksne problematike maksimalnograda a koje se odnose na eksergijsku analizu i optimizacijutermodinamičkih procesa, kao i smjernice za naredna istraživanjaproblema za slučaj ostalih gasova, poluidealnih gasova i Van derWaals – ovog gasa. Može se tvrditi, da postupak analizetermodinamičke funkcije maksimalnog rada, prikazanog u radu,nije uobičajen u literaturi.