Kinetics of Cr(VI) adsorption from aqueous medium onto bentonite

Because of its abundance and toxicity, heavy metals have become a seriousenvironmental problem. The presence of heavy metals, such as Cr(VI), in thewatercourses leads to numerous health problems in humans and animals. Cr(VI) ishighly toxic, even in low concentrations. Because of its carcinogenic, mutagenic andteratogenic effects on human beings, Cr(VI) is considered one of the most criticalpollutants. Due to this, it is necessary to remove Cr(VI) from wastewater prior to itsdischarge into the recipient.This paper studied the possibility for application of bentonite as an adsorbent forCr(VI) from aqueous medium. The characterization of bentonite was determined withchemical composition, specific surface, XRD method and FTIR. Optimal parameterssuch as pH of solution, adsorbent weight, time of adsorption and temperaturewere examined. Values of those parameters were: initial pH value of solution pH=2,adsorbent weight 2 g, time of adsorption 60 min, temperature 308 K. Experimentaldata were obtained by Freundlich and Langmuir isotherm adsorption models as wellas pseudo-first and pseudo-second order kinetics. Results were best described withFreundlich isotherm adsorption model and pseudo-second order kinetics

Synthesis of apatite-type Ce4.67(SiO4)3O via glycinenitrate combustion

The pure Ce4.67(SiO4)3O with the apatite-type of structure was obtained for the first time from cerium nitrate, glycine and tetraethyl orthosilicate (TEOS) through the self-combustion of the gel. The solution of the reactants with the molar ratio of TEOS to water 1: 42 and glycine to NO3 ¯ 1: 3 was transformed into gel. During combustion of the gel the ash containing nanostructured CeO2 and noncrystalline SiO2 was formed. The phase identification and the measurement of the crystallite size was done by XRD diffraction. Ce4.67(SiO4)3O was synthesized from the ash subsequently fired in argon at 1200 °C.Physical chemistry 2008 : 9th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 200

Performance of ternary cement binders containing high volume of fly ash and fluid catalytic cracking catalyst residue

The use of binders based on waste materials in construction industry has both ecological and economic advantages over the use of commercial Portland cements (PC). Preserving the natural resources needed for PC production, as well as reusing waste materials instead of disposing them in landfills, contributes significantly to the protection of the environment. Also, the price of waste materials is usually much lower than the price of raw materials used for production of PC. Coal combustion in thermal power plants produces huge amounts of fly ash (FA). It is estimated that 500-750 million tonnes of FA are generated worldwide annually, with a global utilization rate of only 25 %. Due to pozzolanic properties of this aluminosilicate waste material, FA has been used as PC component for decades. However, the broad use of binders made of high volume of FA (>50%) is limited by their relatively long setting time and low early strength. The other waste material of interest in this work was fluid catalytic cracking catalyst residue (FC3R), a by-product from petrol refineries, which primarily consists of zeolite and amorphous aluminosilicates and also shows pozzolanic activity. Due to relatively small quantities of FC3R produced (~160000 tonnes per year globally), landfilling is usually considered as the most economical option for its disposal. The aim of this work was to investigate the performance properties of ternary binder containing high volume of the two different waste materials, FA and FC3R. The binder consisted of FA, FC3R, and PC (commercial CEM I) mixed in a 49:21:30 mass ratio. Both waste materials were mechanically activated prior to the binder synthesis. Characterization of raw and mechanically activated waste materials via determination of particle size distribution, morphology and mineral composition, was conducted. Analyses of the ternary binder properties showed that using FC3R as the binder component resulted in acceleration of cement hydration and pozzolanic reaction. The ternary binder had shorter setting time and higher early strength than the control binder synthesized with 70 mass% of FA and 30 mass% of PC

Use of sodium oxalate and calcium formate for chemical activation of high volume fly ash (HVFA) binders

This study investigates hydration mechanism of a high volume fly ash (HVFA) binder, comprising 70 wt.% of fly ash (FA), chemically activated by using sodium oxalate (Na2C2O4) and calcium formate (Ca(HCOO)2). Prior to the binder synthesis, mechanical activation of FA was employed. Effects of the activators on the properties of the HVFA binders were determined by measuring setting times and compressive strength of the binders. Heat of hydration, pore solution composition, bound water and portlandite content, mineral composition, and microstructure of HVFA binder pastes were analyzed in order to compare the hydration mechanisms of the HVFA binders activated with the selected activators. The obtained results indicated that using of the two different activators led to the enhancement of the properties of the HVFA binders, but it was achieved in two distinct ways. It was found that the use of Ca(HCOO)2 mitigated adverse effects of the high alkalinity of the pore solution of chemically activated HVFA binder on hydration process and strength development in the later period. Therefore, it was concluded that Ca(HCOO)2 was more suitable for chemical activation of HVFA binders, compared to Na2C2O4

Possibility to use spent fluid catalytic cracking catalyst as component of Portland cement binders

Fluid cracking catalyst residue (spent FCC) is a by-product from petrol refineries. It primarily consists of zeolite (in used sample - faujasite) and amorphous aluminosilicates. In this study, possibility to use spent FCC as a component of binders with low content of Portland cement (PC) have been investigated. Binders made with high volume of mineral additions are being developed in order to reduce the amount CO2 emitted by PC industry. Fly ash (FA), a by-product of coal combustion in thermal power plants, is one of the most commonly used raw material for these binders. The main shortages of binders with high volume of FA are long setting time and low early strength. In this work, mixtures of PC, FA and spent FCC were prepared. It was found that addition of spent FCC to low PC mixtures significantly shortened setting time and improved early strength of the binders. However, 28-day compressive strength of the ternary binder was lower than the strength of low PC binder synthesized with FA only, which indicated the need for further optimization of the binder composition

Synthesis and deposition of MAPbBr3 perovskite on titania nanotube arrays

The organo-inorganic perovskites are materials that have recently revolutionized the field of photovoltaics due to their low-cost fabrication and high optical absorption. The hybrid organoinorganic perovskite absorbs the visible part of the spectrum resulting in the creation of electron-hole pair. To decrease the recombination of charge carriers, the construction of solar cells requires the existence of separate layers for holes and for electrons. TiO2 is usually used as an electron transport layer because its conduction band (CB) lies under the CB of perovskite. In that way, electrons diffuse from CB of perovskite to CB of TiO2. For these experiments, TiO2 nanotubular structure was used as an electron transport layer due to its advantages compared to nanoparticular TiO2. TiO2 nanotubes can provide a one-dimensional transmission channel for the charge carriers, so it will reduce the recombination rate of the carriers and provide a channel for fast carrier transport. However, there is a problem with the contact surface between perovskite and TiO2 nanotubes. The aim of this study is to increase the contact surface of perovskite and TiO2 nanotubes by filling the nanotubes with perovskite material in order to improve electron transport. Methylammonium lead bromide perovskite (MAPbBr3) was deposited on anodically synthesized TiO2 nanotubes which were annealed at 450 °C for 1 h. After degassation of the sample under high vacuum for 3 h at 200 °C, the cooled sample was put in a solution of MAPbBr3 in dimethylformamide (DMF) and it was treated with inert gas (N2), which enabled the filling of the nanotubes with perovskite material to some extent. FESEM and XRD analyses were used for morphological and chemical characterization of the sample. The diffuse reflectance spectroscopy measurement of the sample proved that deposition of MAPbBr3 improves the absorption properties of TiO2 nanotubes. By measuring the I-V characteristics of the sample in the dark and under visible light, a hysteresis curve was obtained

Carbon Cryogel Magnetite Composites-Effective Adsorbents for the Phosphate and Phenol Removal from Water

Carbon cryogel (CC) was impregnated with magnetite to produce a multifunctional magnetic adsorbent capable of removing phenoles and phosphates from water. Adsorbents were prepared via co-precipitation of Fe2+ and Fe3+ ions in aqueous solution in the presence of CC. Non-treated or acid-activated CC was used. The CC: Fe3O4 ratios of 1:1 and 3:1 were applied. The addition of HCl in the synthesis process was also investigated. XRD confirmed the formation of nanocrystalline magnetite. BET analysis showed that the pre-treatment diminished the CC porous structure, reducing also specific surface area (Sp). Formation of magnetite decreases Sp and total volume of micro and meso pores, but their distribution remained unchanged. FTIR spectra revealed that magnetite was attached to the surface of the acid activated CC via C═O bond. DTA-TGA and SEM indicated that acid treatment and presence of HCl were beneficial for homogeneous nucleation and distribution of magnetite, increasing adsorption properties of composite. Batch adsorption proved that the maximum adsorption capacity for phenoles was accomplished with 3:1 ratio with non-treated CC. Samples synthesized with pre- treated CC, under 1:1 ratio, gave the best results for phosphate removal. The CC/magnetite composite was found as promising adsorbent for the simultaneous removal of both polutants.The book of abstract available at: [http://conf.univerzitetpim.com/wp-content/uploads/2022/06/Book-of-Abstracts_2022-1.pdf

Efficient removal of Cd2+ from aqueous solution using subgleba of mushroom Handkea utriformis

Mushrooms are widely investigated and recognized as perspective materials for the removal of various pollutants from wastewater effluents. In this study, mosaic puffball Handkea utriformis was tested as a new biodegradable, but relatively stable material for Cd2+ adsorption from aqueous mediums. The fruiting body of Handkea utriformis goes through the process of autodigestion, during which their inside – gleba is turned into a powdery, sporebearing mass, and the lower portion of the fruiting body – subgleba, into a dark, dry, spongy mass. The impurities and spores present on the surface of the subgleba can be removed in a simple process of purification with acidic and alkaline solutions. The purification decreases the hydrophobicity of the surface of this material, and therefore increases the number of surface functionalities, knowing that subgleba consists of sugars, proteins and polymeric pigments (melanins). The subgleba purified with 0.1M HCl and 0.1M NaOH (Sp) was used for the removal of Cd2+ from the aqueous solution. The efficiency of the material for adsorption of Cd2+ was investigated in a batch system under the constant initial concentration of adsorbate and pH and different concentrations of the adsorbent. Composition and surface morphology were characterized by using FT-IR spectroscopy, SEM and EDX analysis. Concentrations of Cd2+, before and after adsorption, were determined by using Atomic Absorption Spectroscopy (AAS). The Langmuir and Freundlich isotherm models, as well as kinetic models, were evaluated to correlate experimental data. The results showed that kinetic data were well fitted by a pseudo-second-order model. Isotherms studies revealed that the best fit was achieved with the Langmuir isotherm model with a maximum adsorption capacity of 15.2, 19.1 and 25.0 mg g-1 at 25, 35 and 45ºC, respectively

Analiza abiotičkih stresova u sortama Panonske nizije: suša, hladnoća i toplota

Environmental stresses such as drought, cold and heat in Pannonia Basin significantly endanger the cell activity, plant growth and yields in wheat, which is one of the most strategic cereal grain crops in the world. As science and technology advance, new tools are developed while old ones are refined for use by breeders. Higher agronomical efficiency is possible by combining new and old tools to bridge the abiotic stress issues. Five cultivars of winter wheat (Simonida, Petrija, Ljubica, Zvezdana and NS Mila), were used in the study carried out at our experimental field (Novi Sad as a center of Pannonia Basin) across three consecutive growing seasons to assess genetic interaction and the level of tolerance and adaptability of different cultivars to abiotic stresses like drought conditions, cold and heat. Four quantitative yield components and grain yield were analized to assess expression of adapted genotypes in the region. Among the cultivars, Simonida, which has been in use for the longest period, exhibited the most consistent yield response. Additionally, it demonstrated some degree of partial tolerance to abiotic stress conditions, possibly due to the integration of stress memory into its genetic code, supported by statistical analysis findings.Stres izazvan ekološkim činiocima kao što su suša, niske i visoke temperature u Panonskom basenu značajno ugrožavaju ćelijsku aktivnost, rast biljaka i prinos pšenice, koja predstavlja jednu od najvažnijih strateških žitarica u svetu. Kako nauka i tehnologija napreduju, novi alati se razvijaju, dok se stari usavršavaju i stoje na raspolaganju oplemenjivačima. Ipak, postizanje veće agronomske efikasnosti je moguće ako se napravi zajednička veza između njih, kako bi se premostili problemi nastali pod uticajem abiotičkog stresa. U ovom istraživanju, koje je sprovedeno na našem oglednom polju (Novi Sad kao centar Panonskog basena), je korišćeno pet sorti ozime pšenice (Simonida, Petrija, Ljubica, Zvezdana i NS Mila), u tri uzastopne vegetacione sezone, kako bi se procenila genetička interakcija i nivo tolerancije i prilagodljivosti različitih sorti pšenice na abiotičke stresove kao što su suša, niske i visoke temperature. Prinos i četiri kvantitativne komponente prinosa su analizirane kako bi se procenila ekspresija prilagođenih genotipova u ovom regionu. Rezultati statističke obrade podataka su potvrdili da sorta koja je najduže u upotrebi, Simonida, ima najkonzistentniju reakciju na prinos, i da poseduje određeni stepen delimične tolerancije na uslove abiotičkog stresa, koju je ugradila preko stres memorije u svoj genetički kod

Improving the contact surface between TiO2 nanotubes and MAPbBr3 to make perovskite solar cells

The organo-inorganic perovskites are extraordinary materials that have recently revolutionized the field of photovoltaics due to their low-cost fabrication and high optical absorption. In a short period, they reached great efficiency. Many parameters which affect the quality of perovskite films can be optimized, so the efficiency of these devices can be further improved. In perovskite solar cells, the perovskite layer is an active layer that absorbs the visible part of the spectrum, resulting in the formation of the electron-hole pair. To decrease the recombination of charge carriers, the construction of solar cells requires the existence of two additional layers in order to separate the holes and electrons. TiO2 could be used as an electron transport layer because its conduction band (CB) lies under the CB of perovskite. In that way, electrons diffuse from CB of perovskite to CB of TiO2. For these experiments, TiO2 nanotubular structure provides a one-dimensional transmission channel for the charge carriers, which resulting in faster carrier transport. Perovskite methylammonium lead bromide (MAPbBr3) was coupled with TiO2 nanotube arrays which were synthesized by anodization of Ti foil and annealed at 450 °C. The most used methods for deposition of perovskite materials on mesoporous and planar TiO2 are: one-step deposition, two-step sequential deposition, and vapor-assisted solution processing. Disadvantage of these methods is a small contact area between TiO2 and perovskite. The aim of this research was to increase the contact surface of the perovskite and TiO2 nanotubes by filling the nanotubes with the perovskite material in order to improve electron transport