Percent oxygen in air

Martins, George

doi:10.1021/ed064p809

Cited by 9 publications

(11 citation statements)

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“…Table 5 shows clearly that from the six most recent studies using SW, just one of seven possible previous peer-reviewed articles is referenced in two of six articles. This evidences the fact that SW is just qualitatively used as a Fe 0 -based material as it this been the case in classroom demonstrations of the oxygen content of air (approximately one-fifth of the dry air) for several decades [142][143][144][145]. For example, Birk et al [142] allowed acid-washed steel wool to rust in an air-filled container inverted in water; the decrease of air volume is measured.…”

Section: Current Use Of Steel Wool For Water Treatmentmentioning

confidence: 80%

Technologies for Decentralized Fluoride Removal: Testing Metallic Iron-based Filters

Ndé-Tchoupé

Crane

Mwakabona

et al. 2015

Water

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Since the realization in the 1930s that elevated fluoride concentrations in drinking water can have detrimental effects on human health, new methods have been progressively developed in order to reduce fluoride to acceptable levels. In the developing world the necessity for filtration media that are both low-cost and sourced from locally available materials has resulted in the widespread use of bone char. Since the early 1990s metallic iron (Fe 0 ) has received widespread use as both an adsorbent and a reducing agent for the removal of a wide range of contaminant species from water. The ion-selectivity of Fe 0 is dictated by the positively charged surface of iron (hydr)oxides at circumneutral pH. This suggests that Fe 0 could potentially be applied as suitable filter media for the negatively charged fluoride ion. This communication seeks to demonstrate from a theoretical basis and using empirical data from the literature the suitability of Fe 0 filters for fluoride removal. The work concludes that Fe 0 -bearing materials, such as steel wool, hold good promise as low-cost, readily available and highly effective decentralized fluoride treatment materials.

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Section: Current Use Of Steel Wool For Water Treatmentmentioning

confidence: 80%

Technologies for Decentralized Fluoride Removal: Testing Metallic Iron-based Filters

Ndé-Tchoupé

Crane

Mwakabona

et al. 2015

Water

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“…In particular, each visually thin strand of SW is made of thousands of metal fibres that are very reactive [15,16]. The rapid kinetics of SW corrosion justifies its use in scholar practical demonstrations [17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Steel Wool for Water Treatment: Intrinsic Reactivity and Defluoridation Efficiency

Hildebrant¹,

Ndé-Tchoupé

Lufingo

et al. 2020

Processes

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Studies were undertaken to characterize the intrinsic reactivity of Fe0-bearing steel wool (Fe0 SW) materials using the ethylenediaminetetraacetate method (EDTA test). A 2 mM Na2-EDTA solution was used in batch and column leaching experiments. A total of 15 Fe0 SW specimens and one granular iron (GI) were tested in batch experiments. Column experiments were performed with four Fe0 SW of the same grade but from various suppliers and the GI. The conventional EDTA test (0.100 g Fe0, 50 mL EDTA, 96 h) protocol was modified in two manners: (i) Decreasing the experimental duration (down to 24 h) and (ii) decreasing the Fe0 mass (down to 0.01 g). Column leaching studies involved glass columns filled to 1/4 with sand, on top of which 0.50 g of Fe0 was placed. Columns were daily gravity fed with EDTA and effluent analyzed for Fe concentration. Selected reactive Fe0 SW specimens were additionally investigated for discoloration efficiency of methylene blue (MB) in shaken batch experiments (75 rpm) for two and eight weeks. The last series of experiments tested six selected Fe0 SW for water defluoridation in Fe0/sand columns. Results showed that (i) the modifications of the conventional EDTA test enabled a better characterization of Fe0 SW; (ii) after 53 leaching events the Fe0 SW showing the best kEDTA value released the lowest amount of iron; (iii) all Fe0 specimens were efficient at discoloring cationic MB after eight weeks; (iv) limited water defluoridation by all six Fe0 SW was documented. Fluoride removal in the column systems appears to be a viable tool to characterize the Fe0 long-term corrosion kinetics. Further research should include correlation of the intrinsic reactivity of SW specimens with their efficiency at removing different contaminants in water.

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“…Facts that conflict with traditional explanations can teach a great deal about the scientific process. However, other experiments are more appropriate to show that air contains 21% oxygen (5,6 ).…”

mentioning

confidence: 99%

"Experiment with a Candle" without a Candle

Krnel

Glažar

2001

J. Chem. Educ.

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In the popular experiment in which a burning candle in an airtight cylinder purports to demonstrate the percentage of oxygen in the air, the main reason for the change in volume is the expansion and contraction of gases because of warming up or cooling down, not because the oxygen is used for burning. To support this explanation we have devised two experiments, the results of which are similar to the classic experiment with a candle, although a candle is not used. The experiments demonstrate that burning cannot be the only reason for the reduction of volume of gases in the cylinder.

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Percent oxygen in air

Cited by 9 publications

References 0 publications

Technologies for Decentralized Fluoride Removal: Testing Metallic Iron-based Filters

Technologies for Decentralized Fluoride Removal: Testing Metallic Iron-based Filters

Steel Wool for Water Treatment: Intrinsic Reactivity and Defluoridation Efficiency

"Experiment with a Candle" without a Candle

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