Wyniki wyszukiwania - Biblioteka Nauki

1

Response surface methodology (RSM) and its application for optimization of ammonium ions removal from aqueous solutions by pumice as a natural and low cost adsorbent

100%

Moradi M. , Fazlzadehdavil M. , Pirsaheb M. , Mansouri Y. , Khosravi T. , Sharafi K.

|

2016

|

tom Vol. 42, no. 2

33--43

EN

This research was conducted to study the adsorption of ammonium ions onto pumice as a natural and low-cost adsorbent. The physico-chemical properties of the pumice granular were characterized by X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Modeling and optimization of a NH4+ sorption process was accomplished by varying four independent parameters (pumice dosage, initial ammonium ion concentration, mixing rate and contact time) using a central composite design (CCD) under response surface methodology (RSM). The optimum conditions for maximum removal of NH4+ (70.3%) were found to be 100 g, 20 mg/l, 300 rpm and 180 min, for pumice dosage, initial NH4+ ion concentration, mixing rate and contact time. It was found that the NH4+ adsorption on the pumice granular was dependent on adsorbent dosage and initial ammonium ion concentration. NH4+ was increased due to decrease the initial concentration of NH4 and increase the contact time, mixing rate and amount of adsorbent.

2

Use of pumice and scoria aggregates for controlling alkali silica reaction

88%

Tapan M.

|

tom Vol. 50, iss. 2

467--475

EN

Turkey has important potential pumices reserves (68% of the reserve of the world) and 56 % of pumice reserve of Turkey is in the East Anatolia Region. It is important to assess huge pumice reserves in Eastern Turkey for its use in the cement and concrete industry. Use of acidic pumice and basic pumice (scoria) as cement additive or aggregate are gaining popularity because of their proven structural/durability properties. This paper presents the results of an investigation to assess the effectiveness of pumice and scoria aggregates in controlling alkali silica reaction (ASR) of alkali silica reactive aggregate using the following test methods: the accelerated mortar bar test (ASTM C 1260) and the scanning electron microscopy technique (SEM). The morphologies, structures and properties of the samples were determined by XRD, ICP-MS, XRF and thin section study. Mortar cubes were specially prepared according to ASTM standards using 10, 20 and 30% pumice or scoria aggregate as alkali silica reactive aggregate replacement. The results are compared with ASTM requirements to assess the suitability of pumice or scoria for preventing alkali silica reactivity. According to the results of these methods, pumice aggregates control the alkali silica reaction whereas scoria aggregates decrease expansion but is not as effective as pumice in preventing ASR. The results of SEM analysis showed alkali silica gel formation and serious decomposition of aggregate texture due to ASR in scoria added mortar bars.

3

Suitability and characterization of pumice, bauxite, and ferrochrome slag as alternative raw materials in vitrified ceramic industry

88%

Benkli Y. E. , Koca K.

|

2024

|

tom Vol. 60, iss. 2

art. no. 187967

EN

Since the natural raw materials used in the manufacture of clay-based ceramic products vary greatly in the sintering stage, the resulting products are quite heterogeneous. In addition, different types of waste could be used to make ceramic tiles and bricks. Therefore, this study aimed to investigate the effects of pumice, bauxite, and ferrochrome slag on the vitrified ceramic body. In this context, firstly, binary slip mixtures were prepared by composing 40% clay with 60% pumice, bauxite, and ferrochrome slag one by one, which was reduced to 150 μm in particle size. Then, the mixtures were shaped by slip casting method and sintered at 1000°C, 1100°C, 1200°C, and 1250°C. The qualitative XRD analysis was performed in order to see the phase variation, and physical properties were determined with shrinkage and water adsorption measurements. Since pumice transformed into a glassy phase after sintering at 1100°C, an amorphous phase was observed in all samples produced with pumice. In addition, the mullite development occurred in clay-pumice body composition with the temperature increment. However, tridymite and cristobalite phases were analysed in clay bauxite and ferrochrome body compositions. The shrinkage and water adsorption values, which were high in the samples sintered at 1000°C, began to reduce from 1100°C to 1250°C significantly. In particular, water adsorption reached 0% in the clay-pumice system which was suitable for a fully vitrified-high density standard (ISO13006-10545/98). Besides, the brighter colour was reached in the clay-pumice system while brown and black colour was seen in clay-bauxite and clay-ferrochrome bodies, respectively.

4

Effects of pumice additions on thermal and mechanical behaviors of epoxy resin

63%

Kırbaş İ.

|

tom Vol. 71, nr 4

art. no. e146286

EN

In this study, thermal conductivity, mechanical properties, and thermal degradation of pumice-added epoxy materials were investigated. 2%, 4%, 6%, 8%, and 10% of pumice was added to the epoxy resin (EP) % by weight. Various types of analyses and tests were conducted to determine the thermal conductivity, mechanical properties, and thermal degradation of these epoxy materials. The tests and analyses proved that the addition of pumice leads to a decrease in the thermal conductivity coefficient and density of the pure EP material. It also increases the degree of hardness. The addition of pumice had a positive effect on mechanical properties. Compared to pure EP, it increased the tensile strength, Young’s modulus, bending strength, and flexural modulus. As a result of TGA analysis it was determined that with the incorporation of pumice into the EP, its decomposition rate progressed more slowly. At 800_C, the carbon residue improved as a result of the addition of pumice.

5

The Effects of Additives to Lightweight Aggregate on the Mechanical Properties of Structural Lightweight Aggregate Concrete

51%

Khoshvatan M. , Pauraminia M.

|

tom Vol. 31, no. 1

139--160

EN

In the paper, the effects of different percentages of additives (perlite, LECA, pumice) on the mechanical properties of structural lightweight aggregate concrete were tested and evaluated. For the research, 14 mixing designs with different amounts of aggregate, water, and cement were made. Experimental results showed that the specific gravity of lightweight structural concrete made from a mixture of LECA, pumice, and perlite aggregates could be 25-30% lighter than conventional concrete. Lightweight structural concrete with a standard specific gravity can be achieved by using a combination of light LECA with perlite lightweight aggregates (LA) and pumice with perlite in concrete. The results indicated that LECA lightweight aggregates show more effective behavior in the concrete sample. Also, the amount of cement had a direct effect on increasing the strength regardless of the composition of LAs. The amount of cement causes compressive strength to increase. Furthermore, the stability of different experimental models increased from 156 to 345 kg m3 while increasing the amount of cement from 300 to 400 kg m3 in the mixing designs of LECA and perlite for W/C ratios of 0.3, 0.35, and 0.4. For a fixed amount of cement equal to 300 kg, the compressive strength is reduced by 4% by changing the water to cement ratio from 0.5 to 0.4. The compression ratios of strength for 7 to 28 days obtained in this study for lightweight concrete were between 0.67-0.8. rate of tensile strength to compressive strength of ordinary concretes, which is approximately 10, this ratio is about 13.5 to-17.8 in selected and optimal lightweight concretes in this research, which can be considered good indirect tensile strength for structural lightweight concretes.