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Hardness
Published in Pradyot Patnaik, Handbook of Environmental Analysis, 2017
EDTA and its sodium salt readily react with calcium, magnesium, and certain other metal cations to form soluble chelates. Certain dyes, such as Calmagite or Eriochrome-Black T used as color indicators, also react with these metal ions, especially, Ca2+ and Mg2+ forming colored complexes. Thus, Ca and Mg ions combine with the indicator molecules, producing a wine red color at the pH 10. Thus, the sample pH is adjusted to 10 by using a buffer and made wine red before the titration by adding the indicator solution to it. The addition of titrant forms more stable Ca-EDTA and Mg-EDTA complexes, displacing Ca2+ and Mg2+ from their respective chelates with the indicator. Thus, the end point of titration signifies the completion of chelation of all Ca and Mg ions in the sample with the titrant EDTA. This results in the dissociation of all metal–indicator complex molecules. The wine red color turns blue. To enhance the sharpness of the end point, a small amount of magnesium salt of EDTA is added to the buffer.
Chemical Methods
Published in Somenath Mitra, Pradyot Patnaik, Barbara B. Kebbekus, Environmental Chemical Analysis, 2018
Somenath Mitra, Pradyot Patnaik, Barbara B. Kebbekus
Eriochrome Black T is the indicator used. In the presence of Mg2+ a wine-red-colored complex forms. When all the Ca2+ and Mg2+ are complexed with EDTA, the indicator reverts to its uncomplexed blue color.
Sono-assisted enhanced adsorption of eriochrome Black-T dye onto a novel polymeric nanocomposite: kinetic, isotherm, and response surface methodology optimization
Published in Journal of Dispersion Science and Technology, 2021
Akash Deb, Animesh Debnath, Biswajit Saha
Environmental pollution from synthetic dyes is a significant concern worldwide due to its toxic, carcinogenic, teratogenic or mutagenic nature.[1] Dyes are very recalcitrant compounds as they are stable to light, temperature and microbial attack. Besides, dyes may be proven dangerous due to their complex aromatic structure, high organic content and non-biodegradable nature. The presence of a small amount of dye in waterbody will block the sunlight and thus hindering photosynthetic activity, disquieting re-oxygenation capability, and creates an anaerobic condition that will stop the growth of plants. Dyes are generated and applied in various industries such as textile, paper pulp mills, food, cosmetics and leather.[2] Approximately 0.7 million tons of dyes are produced annually with 10,000 different types of varieties, among which most of them are azo dyes. Azo dyes are an organic compound containing the functional group − N=N − which acts as a chromosphere on the chemical structure.[3] Azo dyes are a well-known carcinogen and very difficult to degrade even at low concentrations. Hence it is essential to treat the wastewater containing azo dyes before discharging into water bodies. Eriochrome Black-T (EBT) is an azo dye that used as an indicator in titration and also used to identify rare earth materials.[4] Several treatment technologies are practiced for removal of dyes from an aqua matrix such as chemical oxidation, catalysis, membrane filtration, electrochemical treatment, and adsorption, etc..[5–7] Among them, adsorption technology has been proved one of the most popular, simple and efficient methods for the removal of dyes from wastewater matrix.