Ayten Ates

The effect of various treatment conditions on natural zeolites: Ion exchange, acidic, thermal and steam treatments

Two different natural zeolites having different phase compositions were obtained from different regions of Turkey and modified by ion-exchange (0.5M NH(4)NO(3)) and acid leaching using 1M HCl. The natural and modified samples were treated at low temperature (LT), high temperature (HT) and steam (ST) conditions and characterised by XRF, XRD, BET, FTIR, DR-UV-Vis, NH(3)-TPD and TGA. Ion-exchange with NH(4)(+) of natural zeolites results in the exchange of the Na(+) and Ca(2+) cations and the partial exchange of the Fe(3+) and Mg(2+) cations. However, steam and acidic treatments cause significant dealumination and decationisation, as well as loss of crystalline, sintering of phases and the formation of amorphous material. The presence of mordenite and quartz phases in the natural zeolites increases the stability towards acid treatment, whereas the structure of clinoptilolite-rich zeolites is mostly maintained after high temperature and steam treatments. The natural and modified zeolites treated at high temperature and in steam were found to be less stable compared with synthetic zeolites, resulting in a loss of crystallinity, a decrease in the surface area and pore volume, a decrease in the surface acidity as well as dealumination, and decationisation.

Synthesis and characterization of hybrid iron oxide silicates for selective removal of arsenic oxyanions from contaminated water

A series of hybrid silicates containing iron oxides was synthesized by adding various amounts of iron into silica on the basis of using post precipitation mechanism from aqueous solutions in order to form hydrated iron oxide species (HFO). The obtained materials were characterized by XRD, SEM, TEM, FTIR, Zeta potential and low temperature nitrogen sorption. XRD analysis confirmed that HFO-Si was amorphous and iron oxide crystals in the silica cannot be detected due to the lower size of HFO, which is the probability of its occupied interstitial positions in the silicate matrix. However, TEM image showed the presence of nano-sized HFO located inside the silicate matrix. The adsorption properties and selective efficiency of the synthesized materials were examined with respect to the removal of As(V) and As(III) species from contaminated water under different experimental conditions and in the presence of competing anions. Increasing iron loading enhanced the arsenic adsorption capacity of HFO-Si; the maximum level of arsenic removal was 300mg As/g HFO-Si after 5 successive loads.

Influence of treatment conditions on decomposition activity of N2O over FeZSM-5 with high iron content

The influence of treatment on formation and activity of surface oxygen over FeZSM-5 with high iron content was studied by using a transient multipulse technique combined with temperature-programmed desorption (TPD) and steady-state kinetics. All samples after various treatments were characterised by N2 sorption, NH3-TPD, H2-TPR, and DR-UV–vis. Multipulse experiment results showed that the reductive and inert treatments increase the amount of surface oxygen species formed from N2O. However, the oxidative treatment inhibits almost half of the oxygen formation. High temperature treatment increases not only the surface oxygen amount but also steady-state decomposition of N2O. Based on TPD and CO oxidation with surface oxygen, the active oxygen species formed from N2O are desorbed at low temperature and their amounts increase with oxidative and vacuum treatments and decrease with high temperature treatment. Vacuum treatment in a batch system increases the amount of surface oxygen and prevents transformation of active oxygen species to inactive oxygen species.

Effect of alkali-treatment on the characteristics of natural zeolites with different compositions

A series of natural zeolites with different compositions were modified by post-synthesis modification with sodium hydroxide (NaOH) solution. Natural and modified zeolites were characterized by XRD, SEM, nitrogen adsorption, FTIR, zeta potential and temperature programmed desorption of ammonia (NH3-TPD). The adsorption capacities of these samples were evaluated by the adsorption of manganese from aqueous solution. The treatment with NaOH led to a decrease in the surface area and microporosity of all natural zeolites as well as partly damage of the zeolite structure depending on zeolite composition. In addition, the amount of weak, medium and strong acid sites in the zeolites was changed significantly by NaOH treatment depending on zeolite composition. The NaOH treatment resulted in a four-fold improvement in adsorption capacity of natural zeolite originated from Bigadic and a twofold decrease in that of the natural zeolite originated from Manisa-Gordes. Although the improved adsorption capacity might be mainly due to modification of porosity in the zeolites and formation of hydroxysodalite, the reduced adsorption capacity of the zeolite might be mainly due to a significant deformation of the zeolite structure. The pseudo-second-order kinetic model for the adsorption of manganese on all natural and modified zeolites fits well.

Production and characterisation of biochar from tea waste and its nickel removal capacity from aqueous solutions

Biochar, a carbon-rich solid product of slow pyrolysis of biomass, has gained interest due to its application in the various aims. Investigating of adsorption properties of biochar for removing pollutants from waste water is current research areas. The objective of this study is to obtain biochar from industrial tea waste, characterise it in detail and determine biochars heavy metal adsorption potential to Ni(II) ions. Biochar prepared at 300°C and 400°C and characterised by various methods; elemental analysis, TGA, XRD, XRF, SEM and FTIR. The surface area and pH were determined as well. It was found out that biochar is mesoporous and the structures show more cellulosic characteristics. Carbonisation and aromaticity increase with increasing temperature. The magnitude of adsorption potential is between 500 J/mol and 4000 J/mol and decreases with increasing Ni concentration from 85 ppm to 205 ppm. The adsorption capacities of biochar are much lower than origin of biomass.