Mirela Rožić

Sorption of HDTMA cations on Croatian natural mordenite tuff.

Sorption of the cationic surfactant, hexadecyltrimethylammonium cations (HDTMA), on the solid/liquid interface of the natural mordenite tuff (MT) was studied. The examined tuff originated from Croatia consisting of 30% of mordenite. SEM observations confirmed the crystalline nature of mordenite which can be described in terms of aggregates of many small platelets with diameters in the range of 1 μm. Studying the porosity properties of MT, it was found that the average pore diameter (4.42 nm) between mordenites platelets allows penetration of HDTMA cations. The measurements of zeta potential indicated that in MT samples with surfactant concentration in the range between 0.013 and 0.25 mmol/g, HDTMA cations fill the mesopores of MT. By further increase in HDTMA concentration, the surfactant sorbs on the external zeolite surface, as revealed by the SEM micrographs. Vibrational (FTIR and FT Raman) spectra showed that in the MT samples with initial HDTMA concentration from 0.013 to 0.25 mmol/g, alkyl chains adopt mainly gauche conformation, whereas in the MT samples with higher initial HDTMA concentrations trans conformers are predominant and form a highly ordered structure on the mordenite surface.

Wastewater from wood and pulp industry treated by combination of coagulation, adsorption on modified clinoptilolite tuff and membrane processes

Wastewater from the wood and pulp industry is of environmental concern. It contains high concentrations of organic and inorganic matter. In this work a combined method of coagulation, adsorption and nanofiltration/reverse osmosis (NF/RO) was investigated in the purification of biologically treated wastewater from wood processing. Coagulation with 0.8 g dm−3 AlCl3·6H2O and adsorption on 2.5 g m−3 modified clinoptilolite tuff resulted in removal efficiencies of total carbon (TC), total organic carbon (TOC) and inorganic carbon (IC) up to 67.1%, 77.4% and 49.5%, respectively. Almost complete removal of solutes was achieved after NF/RO treatment. The TOC removal efficiency with RO membrane (CPA-3, LFC-1, XLE) and tight NF membrane (NF90) was 98% and with highly porous NF membrane (DK), 88%. After the proposed treatment the purified water stream can be recycled into the process or safely disposed to the river.

Development and validation of an HPLC method for the determination of endocrine disruptors bisphenol A and benzophenone in thermochromic printing inks

ABSTRACT The endocrine disruptors bisphenol A (BPA) and benzophenone (BFN) could be important ingredients in thermochromic printing inks in significant amounts. Due to patent protection and use of the inks, manufacturers are not obliged to state their precise chemical composition. These substances in increasingly used thermochromic printing inks present a hazard for human health and environment in the case of inappropriate application and waste disposal. In this work we enabled identification of the inks that contain these hazardous substances by developing a new method for the analysis of BPA and BFN in thermochromic printing inks. The method is based on the reversed-phase liquid chromatography (LC) with UV detection at 226 and 254 nm. Ultrasound-assisted sample extraction in methanol was proven to be the most suitable and effective among several other solvents. The method was completely validated with satisfactory results. The specificity of the method was proven by the additional LC–tandem mass spectrometry analysis. A representative group of 15 ink samples from various manufacturers, curing and printing modes was analyzed. BPA was found in three samples with mass fractions of about 2% while BFN was found in two samples with mass fractions of 0.34 and 0.66%. GRAPHICAL ABSTRACT

Thermochromic ink - paper interactions and their role in biodegradation of UV curable prints

In this study, biodegradability aspects of UV thermochromic leuco dye print on three different paper materials (synthetic, recycled, and bulky) were studied using the soil burial test under anaerobic conditions. Biodegradation of UV curable thermochromic prints were evaluated for changes by visual examination, microbial growth assay, weight loss measurements, Fourier transform infrared spectroscopy, scanning electron microscopy and colorimetric measurements. Results showed a better absorption of ink into the bulky paper structure, followed by recycled paper. Synthetic paper is not absorbent. The ink binder altogether with classic pigment and microcapsules penetrates into the structure of bulky paper. Recycled paper absorbs ink binder mostly with classic pigment. Better adsorption of binder into the bulky paper structure results in thinner layer of ink binder on the paper surface. On non-absorbent synthetic paper, microcapsules are covered with thicker layer of ink binder. In the case of bulky paper, the highest rate of biodegradation was observed, resulting in a higher number of bacteria, higher weight loss, higher changes in colour (destruction of almost all microcapsules) and almost complete reduction in thermochromic effect of the prints. Results show that microcapsules, which penetrate into the structure of bulky paper, are promoting the rate of bulky paper biodegradation. The opposite behaviour was noticed for the penetration of classic pigment into the structure of recycled paper, which resulted in remarkable reduction of recycled paper biodegradation rate. The thicker layer of ink binder (containing classic pigment) on the surface of microcapsules on recycled paper resulted in slower rate of microcapsules degradation and smaller colour change of the print. The thickest layer of ink binder and classic pigment on synthetic paper surface causes the slowest rate of biodegradation of print.

Solvents interactions with thermochromic print

The thermochromic ink composition includes a thermochromic microcapsules and an ink vehicle. Thermochromic microcapsules usually consist of at least three components – the colorant, colour developer and solvent. In order to achieve desired effect, the components are mixed in precisely determined proportions and encapsulated in a polymer envelope in order to protect him against external influences (Kulčar et al., 2010).