Search

Environmental protection and sustainable agricultural production require the use of inexpensive and environmentally acceptable soil supplements. Objectives of this study were to investigate the influence of the addition of the natural zeolite – clinoptilolite (NZ) and its iron(III)-modified form (FeZ) on the potassium and nitrate leaching from sandy, silty loam and silty clay soils. The zeolites were added in two amounts: 0.5 (FeZ) and 1.0 wt. % (NZ and FeZ). The experiments were carried out in columns organized in eight experimental systems containing unamended (control specimens) and amended soils. The concentration of K+ and NO3–N in the leachates was monitored during 7 days. The obtained results indicate that the K+ and NO3–N leaching mainly depends on the soil type and pH of the soil. The NZ and FeZ addition has the highest impact on the K+ retention in the acidic sandy soil. The highest NO3–N retention is obtained with FeZ in acidic silty loam soil. The K+ leaching kinetics for all the studied soils follow the Avrami kinetics model with the parameter n < 1. This study demonstrates that NZ and FeZ can be a good soil supplement for the K+ retention for all studied soils and in the NO3–N retention for silty loam and silty clay soils. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172018]

The multidrug resistant bacteria Acinetobacter baumannii cause serious hospital infections. Commercial poly(vinyl chloride) (PVC) used for endotracheal tubes was modified in order to obtain the composite with antibacterial effect towards clinical isolate of A. baumannii ST145. The composites were prepared by addition of different amounts of copper-containing zeolite tuff (CuZ) and by successive impregnation with D-Tyrosine (D-Tyr) solution. The composites which were obtained by addition of CuZ (CuZ-PVC) only did not exhibit antibacterial effect. The impregnation of the CuZ-PVC by D-Tyr resulted in an antibacterial effect which is explained by a synergistic effect of CuZ and D-Tyr. Rheological tests confirmed that the modification of PVC by CuZ does not affect its processability and reformability. [Projekat Ministarstva nauke Republike Srbije, br. 172018]

The clinoptilolite-rich tuff (NZ) from Zlatokop deposit (Vranjska Banja, Serbia) has been studied as a nitrogen carrier for grass production. Mechanism of binding ammonium cations present in water solutions by NZ has been examined as well as possibility of adsorption of ammonia released in fresh cattle manure during its fermentation. The NH4+ binding from solutions proceeds via an ion-exchange process which follows the pseudo-second-order kinetics. Adsorption isotherms studied at 298-318 K follow the Freundlich isotherm equation. The NZ readily adsorbs ammonia liberated from manure and an addition of 10 wt.% of NZ to manure can preserve up to 90% of ammonia. The potential benefit of this effect has been examined in greenhouse pot experiments with the Italian ryegrass (Lolium multiflorum, var. Macho) using three different types of soil (silty, clayey and sandy). The zeta potential measurements show that stability of their colloidal dispersions differs mutually and that addition of the NZ differently affects the stability and nitrogen cycling. All results indicate that NZ can be applied in grass production. [Projekat Ministarstva nauke Republike Srbije, br. 172018 and Norwegian Programme in Higher Education, Research and Development HERD]

In this work, different metal oxides (MO) supported on two types of zeolites: 1) natural clinoptilolite (NZ) and 2) synthetic zeolite, ZSM-5 were prepared and tested as catalysts in the fast pyrolysis of hardwood lignin. NZ was modified with the CaO and MgO by a simple two steps procedure consisting of an ion exchange reaction and a subsequent calcination at 773 K. The synthetic ZSM-5 was modified with several MO species (Ni, Cu, Ca, Mg) by a wet impregnation and calcination at 873 K. Тhe prepared catalysts were characterized by X-ray diffraction analysis (XRD), scanning electron microscopy and energy dispersive X-ray analysis (SEM/EDS) and measurement of specific surface area (BET method). Acid sites were characterized and quantified by pyridine (py) absorption using Fourier transform infrared spectroscopy (FTIR). The catalysts exhibit catalytic activity depanding on modification, reaction temperature and of the MO contents. The highest yield of useful phenol in bio-oil was obtained with NiO/ZSM-5 (34.8 wt.%) which exhibits the highest specific surface area and the highest concetration of Brönsted and Lewis acid sites. The studied catalysts did not increase significantly the content of polycyclic aromatic hydrocarbons (PAHs) and heavy compounds compared to non-catalytic experiment. [Projekat Ministarstva nauke Republike Srbije, br. 172018]

The natural zeolitic tuff from the Zlatokop mine (Vranjska Banja deposit) has been investigated as a starting material for obtaining a low cost adsorbent for the removal of nitrate from water media. The tuff riched with zeolite - clinoptilolite was modified by simple procedures by several oxides: iron(III), manganese(IV) and magnesium in order to make clinoptilolite surface accessible for binding the nitrate ions. The obtained oxide-modified zeolite samples were characterized by scanning electron microscopy and energy dispersive X-ray analysis (SEM/EDS), powder X-ray diffraction (PXRD), infrared spectroscopy (FTIR) and by measurement of specific surface area. The effects of the adsorbent dosage (0.5, 1.0, 1.5 and 2.0 g), temperature (25, 35 and 45 °C) and initial nitrate concentration (C0= 100, 200 and 300 mg dm-3) on the binding efficiency were also studied. For all adsorbents the efficiency increases with temperature. The type of oxides effects the adsorption mechanism and Fe(III) oxide modified zeolite exhibits the best binding ability. For this adsorbent the adsorption kinetics was studied and found that it is best represented by the pseudo-second-order model. [Projekat Ministarstva nauke Republike Srbije, br. 172018]

3-methylaminopropylamine (MPA) has been studied as a structure-directing agent (template) in the synthesis of open-framework phosphate-based materials. The influence of temperature, molar ratio of reactants, crystallization time and presence of fluoride ions on the crystallization of aluminophosphate, transition metal-substituted aluminophosphate [transition metal - Mn(II), Cr(III) and Co(II)] and zincophosphate has also been investigated. MPA exhibits the templating role and in all as-synthesized crystalline products and it is entrapped in an inorganic lattice interacting with the framework via hydrogen or/and electrostatic interactions. According to detailed thermal analysis the type of interactions seems to be crucial for thermal behaviour of MPA and also for the thermal stability of the organic-inorganic crystal system. Structural analysis suggested that the formed crystalline structures have no mutual structural analogy. This indicates that precise role of the organic (guest) component in nucleation process for the open-framework phosphates (host) is very complex as well as the nucleation process itself. [Projekat Ministarstva nauke Republike Srbije, br. 172018]

The thermal degradation of cetyltrimethylammonium bromide (CTMAB) inside the mesoporous SBA-3 was studied under non-isothermal conditions. There are two distinct and complex kinetic processes which partly overlap, each consisting of one dominant and three minor individual processes. The two dominant processes can be described by the Sestak-Berggren model. The main decomposition step (the first dominant process) involves the overcoming of weak interactions between CTMAB and the silica network and proceeds with a lower Ea value (116±2 kJ mol-1) than the second dominant process (153±5 kJ mol-1), which can be explained by the size reduction of the pore openings due to the contraction of the SBA-3 unit cell caused by the removal of CTMAB.

This review is a brief summary of open-framework aluminophosphates and their transition metal-substituted modifications. The materials exhibit structural and compositional diversity, as well as a wide range of pore openings, which are crystallographically ordered and can be tuned by an appropriate choice of synthesis conditions. The diameters of the apertures, cages and channels fall in the range of 0.4 to about 1.5 nm, which recommends aluminophosphates for a novel area of application-nanocatalysis. Isomorphous substitution of the framework elements by transition metal ions which possess redox ability creates active sites inside the aluminophosphate lattice and opens routes towards shape selective bi-functional catalysis. In order to obtain an insight into the location of the transition metal ions, different characterization techniques have to be used.

A novel layered zincophosphate (ZnPO–MPA) was prepared by hydrothermal crystallization using 3-methylaminopropylamine (MPA) as a structure-directing agent. The structure consists of macroanion [Zn2P3O8(OH)3]2- layers which are built up of 4-membered ring channels. The channels (of about 3.7 Å diameter) arise through the connection of the neighbouring rings by two oxygen bridges. The negative charge of the layers is compensated by diprotonated MPA molecules which are stacked parallel to the ring channels. ZnPO–MPA is stable up to 300 °C. At higher temperatures MPA decomposition begins followed by a dehydration, which occurs through condensation of the framework hydroxyl groups. The activation energy of the MPA decomposition is high due to the fact that the layers and MPA cations are held together by strong hydrogen bonds.

1,3-Diaminopropane (DAP) was used as a structure-directing agent for the hydrothermal synthesis of an organically templated iron phosphate. During crystallization at 180 ºC, iron phosphate (FePO-DAP) with a layered structure was formed after one day. Longer crystallization yielded a mixture of FePO-DAP and leucophosphite, raising the question whether a transformation of FePO-DAP to leucophosphite occurs, or whether DAP decomposes under hydrothermal conditions resulting in leucophosphite formation. Lattice energy and free energy calculations strongly support the supposition that a decomposition of DAP occurs prior to the formation of leucophosphite.