Structural Characteristics and Adsorption Properties of Alkali Activated Blends Ashes/Metakaolin

The aim of this paper is to show the possibility of using waste materials, blends of (wood ash, fly ash, from thermal power plant, and metakaolin) for the production of alkali activated materials that can be used to purify wastewater from different kinds of pollutants such as heavy metals. Heavy metals are toxic, especially cadmium, so they must be removed from wastewater to prevent or minimize contact with the environment and humans. The synthesis of the alkali activated materials was performed by mixing solid precursors with a liquid alkali activator. Two- and three-component systems of wood ash, fly ash and metakaolin (wood ash/fly ash, wood ash/metakaolin, fly ash/metakaolin and wood ash/fly ash/metakaolin) were used as precursor materials. The alkali activator solution was a mixture of sodium silicate solution and sodium hydroxide solution of concentrations (6M and 12M). The characterization of alkali activated materials was studied by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDS). XRD measurements of investigated samples showed a characteristic halo between 18 and 35º 2 with a dominant crystal phase of quartz. FTIR spectroscopy showed that the main vibration band of all investigated samples appeared between 1037-996 cm-1, and corresponds to Si-O-Si/Si-O-Al bands. SEM/EDS analysis was used to determine the microstructure of the samples. The adsorption efficiency of the investigated alkali activated materials for removing cadmium ions from aqueous solution was tested under different conditions: initial concentration of cadmium ions in the range of 20-100 mg/l, pH values from 3 to 7 and mass of adsorbents from 0.02-0.05 g

Upotreba letećeg pepela u industriji građevinskog materijala

In this study, fly ash (FA) from the active and passive cassette TENT A (Nikola Tesla power plant, Obrenovac) is characterized from physicochemical and radiological aspects.Samples of FA consisted of amorphous phase followed by quartz, mullite, plagioclase, K-feldspar, hematite and calcite. As indicated by laser granulometry, the fraction D50 of investigated samples are about 80μm, so based on the above, they belong to coarse ashes.Very important parameter which defines chemical composition of the fly ash as precursor material of clinker or alkali activated materialsis presence of organic matter which is expressed by total organic content (TOC).Assessment of radiation exposure during coal combustion depends on the concentration of radioactive elements in the coal and in the resulting fly ash. Fly ash as industrial waste contains certain concentrations of natural radionuclides that are considered naturally occurring radioactive materials (NORM). The results showed that fly ash has satisfactory radiological properties and can be used as an addition to clinkers, but also as a potential precursor of a new class of alkaline activated materials that can be used in the construction sector.Procena izloženosti zračenju pri sagorevanju uglja zavisi od koncentracije radioaktivnih elemenata u uglju i u letećem pepelu koji nastaje. Uzorci letećeg pepela se sastoje od amorfne faze praćene kvarcom, mulitom, plagioklasom, K-feldspatom, hematinom, kalcitom. Kao rezultat laserske granulometrije, frakcija D50 za ispitivane uzorke je približno 80 μm, tako da na osnovu navedenog, leteći pepeli predstavljaju pepele krupnih čestica. Veoma važan parametar je prisustvo organske materije koje se izražava ukupnim organskim sadržajem. Leteći pepeli kao industrijski ostaci sadrže određene koncentracije prirodnih radionuklida koji se smatraju prirodnim radioaktivnim materijalima (NORM). U ovojm istraživanju, leteći pepeo iz aktivne i pasivne kasete TENT A (termoelektrana Nikola Tesla, Obrenovac) karakteriše se sa radiološkog i fizičko-hemijskog aspekta. Rezultati su pokazali da leteći pepeo ima zadovoljavajuća radiološka svojstva i da se može koristiti kao dodatak klinkerima, ali i kao potencijalni precursor nove klase alkalno aktiviranih materijala koji se mogu primeniti u građevinskom sektoru.XXXII Simpozijum Društva za zaštitu od zračenja Srbije i Crne Gore, 4-6. oktobar 2023; Budva, Crna GoraProceedings: [https://vinar.vin.bg.ac.rs/handle/123456789/11602

Radiological and Structural Characterization of Raw and Alkali-Activated Wood Ash and Metakaolin Blends

The aim of the presented research was to investigate the application possibility of wood ash and metakaolin to obtain alkali-activated materials as relatively new materials in the building industry. Thus, in order to assess the adequate use of these waste materials, structural and radiological characteristics should be considered. Until now, the focus has been on ash from thermal power plants produced by burning coal, but a large part of households in our country have individual fireplaces in which wood is used as the basic raw material; thus, it is very interesting to measure the activity concentration of radionuclide in wood ash as well as the possibility of reusing that ash for other purposes. All materials were studied, in terms of physical and chemical characteristics, by methods such as X-ray diffraction (XRD), Fourier transform infra-red (FTIR) spectroscopy, and scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDS). XRD measurements of wood ash samples showed that it consists of calcite and larnite. FTIR spectroscopy revealed a polymeric Si–O–Al framework in alkali-activated materials and Si–O bonding bands corresponding to silicon dioxide. Determination of radionuclide content was performed by means of gamma-ray spectrometry. Results showed that the alkaline activation process led to the decrease in the activity concentration of radionuclides detected in the measured samples. External radiation hazard index (Hex) for wood ash was reduced by more than 50% after alkali activation. The results of activity concentration measurements in alkali-activated materials indicate potential for their safe application in building construction

Pertraction of phenol in hollow-fiber membrane contactors

In this paper the multistage membrane pertraction (simultaneous extraction and reextraction) of phenol with linear monoalkyl cyclohexane (IMACH) as a carrier and sodium hydroxide solution as a strip, in laboratory scaled pertractors with polysulphone hollow-fiber membranes, was investigated. Two types of pertractors were used, one being "fiber-in-fiber" type, and the other "fiber-by-fiber" type, both with parallel countercurrent flow of three independent liquid streams (feed, extragent and strip). The best results were obtained with feed and strip flow rates low and equal, while the organic flow rate was four times higher. Efficiency is higher for lower phenol concentration in feed, and higher alkalinity of stripping solution. It was shown that the pertraction of phenol with IMACH as an organic carrier is an extraction step-limited process. For that reason the "fiber-by-fiber" type of pertractor offers better constructive possibilities, since it enables combining larger number of fibers for extraction step with a corresponding smaller number of fibers for the Stripping step, which is not possible in the case of the "fiber-in-fiber" type of pertractor

Adsorpcija kadmijumovih jona na kaolinitu modifikovanim histidinom i cisteinom

Continuous development of new technologies leads to increasing pollution of water, thus creating the need for new materials that could be used in the processes of its purification. Therefore, adsorbents prepared from agricultural waste, resins, silica gels, zeolites, clays, flying ash, aluminosilicates and other materials are being investigated as potential sorbents. Recently, research has focused on improving the adsorption capacity by modifying the material by binding or impregnating inorganic and organic molecules on the surface. In this paper, the kaolinite modification with amino acids, histidine and cysteine, was performed to improve the efficiency of adsorption of cadmium ion. Cation exchange capacity (CEC) of raw and modified kaolinite was determined by titration with methylene blue. The influence of operating parameters, such as adsorption time, pH value of the solution, initial metal concentration and temperature, on the capacity and adsorption efficiency were examined. Better agreement of experimental results with Freundlich's adsorption isotherm and the pseudo-second order kinetics model suggest that the adsorption of cadmium ions on the investigated adsorbents takes place by chemisorption mechanism. The change of Gibbs free energy has a negative value for both adsorbents, which shows that the adsorption process is spontaneous. The efficacy of cadmium removal from the aqueous solution onto histidine-modified kaolinite increased from 78.6% to 91.8%.Kontinualan razvoj novih tehnologija dovodi do povećanog zagađenja vode, čime se stvara potreba za novim materijalima koji se mogu koristiti u procesima prečišćavanja. Kao potencijalni, istražuju se adsorbenti pripremljeni od poljoprivrednog otpada, smola, silika gela, zeolita, gline, letećeg pepela, aluminosilikata i drugih materijala. Nedavna istraživanja su se fokusirala na poboljšanje adsorpcionog kapaciteta modifikovanjem materijala vezivanjem ili impregnacijom neorganskih i organskih molekula na površini. U ovom radu izvršena je modifikacija kaolinita aminokiselinama, histidinom i cisteinom, kako bi se poboljšala efikasnost adsorpcije jona kadmijuma. Kapacitet izmene katjona (CEC) sirovog i modifikovanog kaolinita određen je titracijom sa metilenskim plavim. Ispitivan je uticaj radnih parametara, kao što su vreme adsorpcije, pH vrednost rastvora, početna koncentracija metala, i temperatura, na kapacitet i efikasnost adsorpcije. Bolje slaganje eksperimentalnih rezultata sa Freundlich-ovom adsorpcionom izotermom i kinetičkim modelom pseudo-drugog reda sugeriše da se adsorpcija kadmijumovih jona na ispitivanim adsorbentima odvija putem hemisorpcionog mehanizma. Promena Gibsove slobodne energije ima negativnu vrednost za oba adsorbenta, što pokazuje da je proces adsorpcije spontan. Efikasnost uklanjanja kadmijuma iz vodenog rastvora na kaolinitu modifikovanim histidinom povećava se sa 78,6% na 91,8%

Microstructural Characterization and Adsorption Properties of Alkali-Activated Materials Based on Metakaolin

The microstructural characterization and adsorption properties of metakaolin (MK) and alkali-activated metakaolin, known as geopolymer materials (GP) were investigated. The structure and properties of the metakaolin and obtained geopolymer were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. Furthermore, based on the analysis of adsorption efficiency, microstructure and mineral structure, the difference between geopolymer and metakaolin on the performance of immobilizing heavy metals have been discussed. The kinetics of adsorption can be represented by pseudo-second order equation. The results of lead ions adsorption experiments were best fitted by Freundlich adsorption isotherm for both investigated adsorbents. The highest removal efficiencies of alkali-activated material based on metakaolin was found 97.5% at pH 4 and metakaolin removal efficiencies was found 92% at pH 5.5

Primena alumosilikatnih polimera na bazi metakaolina u adsorpciji jona kadmijuma iz otpadnih voda

Alumosilicate polymers (geopolymers) based on metakaolin as precursor and alkaline activators of different concentrations (2M, 4M, 6M and 8M NaOH/Na2SiO3) were used to remove ions of cadmium from wastewater. Experiments were carried out in a batch process at room temperature (23 ± 1 ° C) for different operating parameters: adsorption time, pH value of solution, initial concentration of metal and mass of adsorbents. It was found that the optimum pH value for all adsorbents is above 6.0. The adsorption efficiency increases with increasing pH of the solution. With an increase in the initial concentration of cadmium, the adsorption capacity increases and reaches a value of over 200.0 mg/g. The experimental results have better agreement with Freundlich's adsorption isotherm (surface heterogeneity, hemisorption mechanism) and the pseudo-second order model (the principle of the chemisorption mechanism and adsorption rate depend on the adsorbent concentration). Alumosilicate geopolymer samples were characterized using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Fourier-Transform Infrared Spectroscopy (FTIR).Za uklanjanje jona kadmijuma iz otpadnih voda korišćeni su alumosilikatni polimeri (geopolimeri) na bazi metakaolina kao prekursora i alkalni aktivator različitih koncentracija (2M, 4M, 6M i 8M NaOH/ Na2SiO3). Eksperimenti su vršeni u šaržnom procesu na sobnoj temperaturi (23±1 °C) pri različitim radnim parametrima: vreme adsorpcije, pH vrednost rastvora, početna koncentracija metala i masa adsorbenata. Utvrđeno je da je optimalna pH vrednost za sve adsorbente iznad 6,0. Efikasnost adsorpcije raste sa porastom pH vrednosti rastvora. Sa povećanjem početne koncentracije kadmijuma raste adsorpcioni kapacitet i dostiže vrednost preko 200,0 mg/g. Ekperimentalni rezultati su pokazali dobro slaganje sa Freundlich-ovom adsorpcionom izotermom i modelom pseudo-drugog reda. Karakterizacija geopolimera urađena je pomoću rendgenske difrakcije (XRD), skenirajuće elektronske mikroskopije (SEM) i infracrvene spektroskopije sa Furijeovom transformacijom (FTIR)

The Applications of New Inorganic Polymer for Adsorption Cadmium from Waste Water

Fundamental research of inorganic polymers prepared from available aluminosilicate precursors represent an innovative class of materials characterized by low energy consumption for production. This is just one of the reasons why their use is focused in protecting the environment for removing of heavy metals from aqueous solutions. The concentration of hydroxide as activator solution plays an important role in the geopolymerization process. The present study examined the use of geopolymer materials, obtained in reaction of geopolymerizations of metakaolin as precursor activated with NaOH concentration 2.0, 4.0, 6.0 and 8.0 mol/dm(3) for removal of cadmium ions from aqueous solutions. The structure and properties of the obtained geopolymer samples were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and diffuse reflection infrared spectroscopy (DRIFTS). To investigate the surface charge of geopolymers the zeta potential measurements were performed. Batch adsorption experiments conducted at room temperature (23 +/- 1 degrees C) showed that the adsorption pattern followed the Freundlich isotherm model. The maximum removal of cadmium obtained from batch studies was 84.1% for GP6M at pH approximate to 6.7. The results generally showed that geopolymer samples could be considered as a potential adsorbent for cadmium removal from aqueous solutions