Hard Water and Soft Soap: Dependence of Soap Performance on Water Hardness. A Classroom Demonstration

Osorio, Viktoria Klara Lakatos; Oliveira, Wanda de; Seoud, Omar A. El; Cotton, Wyatt; Easdon, Jerry

doi:10.1021/ed082p257

Cited by 11 publications

(11 citation statements)

References 1 publication

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“…Water hardness in general can be attributed to multivalent cations and most often to calcium (Ca 2+ ) and magnesium (Mg 2+ ) that are typically abundant in groundwater. While hard water is generally not considered a health hazard, water of a high level of hardness undermines the efficacy of detergents and promotes surface scaling that is detrimental to water infrastructure and power plants. Hardness can be reduced by water softening using either chemical precipitation (i.e., lime-soda softening) , or ion exchange. − However, these processes either inherently require the use of chemicals or consume chemicals for regeneration.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of Selective Ion Removal in Membrane Capacitive Deionization for Water Softening

Wang

Lin

2019

Environ. Sci. Technol.

134

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Capacitive deionization (CDI) is an emerging technology capable of selective removal of ions from water. While many studies have reported chemically tailored electrodes for selective ion removal, the selective removal of divalent cations (i.e., hardness) over monovalent cations can simply be achieved using membrane CDI (MCDI) equipped with ion exchange membranes (IEMs). In this study, we use both experimental and modeling approaches to systematically investigate the selective removal of Ca2+ over Na+. Specifically, the impacts of current density, hydraulic retention time, and feed composition on the selectivity of Ca2+ over Na+ were investigated. The results from our study suggest a universal correlation between the ratio of molar fluxes and the ratio of spacer channel ion concentrations, regardless of operating conditions and feed composition. Our analysis also reveals inherent and universal trade-off relationships between selectivity and the Ca2+ removal rate and between selectivity and the degree of Ca2+ removal. This fundamental understanding of the mechanism of selective ion removal in MCDI can also be applied to flow-electrode CDI processes that employ IEMs.

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Section: Introductionmentioning

confidence: 99%

Mechanism of Selective Ion Removal in Membrane Capacitive Deionization for Water Softening

Wang

Lin

2019

Environ. Sci. Technol.

134

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“…Water hardness measures the total amount of divalent cations dissolved in water, , but usually only Ca(II) and Mg(II) ions are taken into consideration because they are the major cations present in drinking water. Water hardness is an important parameter to determine water quality and is widely considered the main cause of incrustation in industrial and domestic water plants and of the sequestration of soaps in clothes and crockeries cleaning . For these reasons, water analysis is one of the major topics of the Italian Chemical Technical School, taught to the students in the analytical courses from the third to the fifth year of high school.…”

Section: Introductionmentioning

confidence: 99%

Working in a Team: Development of a Device for Water Hardness Sensing Based on an Arduino–Nanoparticle System

Zarantonello¹,

Mancin

Bonomi³

2020

J. Chem. Educ.

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This work describes a two-year project carried out in an Italian technical high school. Through integrated work, the activity involved the efforts of different teachers and students, particularly those in the Chemical, Electronic, and IT departments. They merged their complementary skills to create an inexpensive device that quickly measures water hardness. The pedagogical aspect of this work aimed to support and reinforce development of the key competences for lifelong learning recommended by the European Commission, especially by strengthening the logical–mathematical, digital, and social skills of the students. The device made is based on an Arduino board connected to a red LED and an optical sensor. The device is able to read the intensity of light transmitted through the sample and to independently convert this output into the water hardness expressed in French degrees. The color change used as information transducer is due to the aggregation of negative gold nanoparticles induced by the bivalent cations in solution. Working in school laboratories under teacher supervision, students connected and troubleshot the hardware system, synthesized and characterized the gold nanoparticles, and developed the software. Finally, the system was assembled inside a box composed of a rigid container, a sample holder, and a touchscreen display. Instructions for replicating this instrument are reported in the paper, while further details and explanations for instructors and students are provided in the Supporting Information.

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“…Por esse motivo, os sabões produzidos no país não são preparados para espumar em água dura. 7 Sendo assim, quando, ocasionalmente, a água apresenta dureza, é necessário um tratamento para a sua remoção. Alguns métodos utilizados para a remoção da dureza da água utilizam flotação por ar dissolvido (FAD), com oleato de sódio, ou processos de troca iônica.…”

Section: Figuraunclassified

“…2 Em aulas experimentais, existem tentativas para remoção dos íons Ca 2+ e Mg 2+ utilizando EDTA ou carbonatos solúveis. 7 Inicialmente, a produção industrial do ácido aconteceu a partir do citrato de cálcio obtido do limão. Outro método para a síntese do ácido é a via fermentativa, a partir de cana-de-açúcar ou beterraba, utilizando o fungo Aspergillus niger, sendo atualmente esse processo o responsável por 90% da sua produção.…”

Section: Figuraunclassified

Citric Acid Extraction from Lemon and its Use for Removal of Hard Water: An Alternative Method for Chemistry Classes

Scopel¹,

Conti²,

Dalmaschio³

et al. 2017

Rev. Virtual Quim.

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The hard water has cations Ca 2+ or Mg 2+ dissolved at concentrations that difficult for soap to foam or lather well. Some known methods for softening of water hardness, such as those using precipitant or complexing agents. This study proposes an alternative method, which can be used in chemistry classes, for the water hardness removal, with the calcium ions precipitation, from the addition of citric acid to the solution. The citric acid is present in citrus fruits, as lemon, and it can be extracted with the addition of Ca(OH) 2 to the lemon juice and thereafter addition of sulfuric acid to the precipitate formed. The experiment has applicability in chemistry teaching, in content as chemistry reactions, stoichiometry, water hardness treatment, among others.

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Hard Water and Soft Soap: Dependence of Soap Performance on Water Hardness. A Classroom Demonstration

Cited by 11 publications

References 1 publication

Mechanism of Selective Ion Removal in Membrane Capacitive Deionization for Water Softening

Mechanism of Selective Ion Removal in Membrane Capacitive Deionization for Water Softening

Working in a Team: Development of a Device for Water Hardness Sensing Based on an Arduino–Nanoparticle System

Citric Acid Extraction from Lemon and its Use for Removal of Hard Water: An Alternative Method for Chemistry Classes

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