Calcium carbonate alkalizer

The presence of transition metal compounds as oxidation catalysts can cause rapid degradation of calcium carbonate-alkalized papers under humid conditions. Magnesium carbonate offers better protection than calcium carbonate. 

A variety of adverse effects have been reported following the use of antacids. If sodium bicarbonate is absorbed, it can cause systemic alkalization and sodium overload. Calcium carbonate may induce hypercalcemia and a rebound increase in gastric secretion secondary to the elevation in circulating calcium levels. Magnesium hydroxide may produce osmotic diarrhea, and the excessive absorption of Mg++ in patients with renal failure may result in central nervous system toxicity. Aluminum hydroxide is associated with constipation serum phosphate levels also may become depressed because of phosphate binding within the gut. The use of antacids in general may interfere with the absorption of a number of antibiotics and other medications. 

The various support materials have different effects on potential carbon formation. This seems to go in parallel with the Lewis/Bronsted acidity. The main commercially used catalyst supports can be ranked as follows in decreasing order of carbon forming tendency (and thus in decreasing order of the important minimum practical steam/ carbon ratio) a-alumina > magnesium aluminate (spinel) > calcium aluminate > alkalized calcium aluminate [419],... 

Corrosion in public water piping systems is responsible for large economic loss. In pipes of cast iron, steel and other metallic materials, corrosion may be prevented by use of coatings (Section 10.6) or by water treatment (addition of calcium compounds, alkalization or carbonation). Water distribution systems are further dealt with in Section 8.4, Corrosion in Soils. 

Aluminum and ferrosilicon anodes are suitable for the protection of hot water tanks. The use of aluminum anodes in a hot water apparatus has additional effects, an indirect protective action on subsequent piping, since a protective film (1-1.5 mm thick) is built up by anode-formed aluminum oxide hydrates. In addition to alkalization at the cathode, a shift in the calcium carbonate (CaCOj)-CO2 equilibrium leads to partial softening of water, with CaC03 being deposited at the cathode. 

Sodium, potassium and calcium salts of mono and polyphosphoric acids, incl. such salts when alkalized with sodium carbonate, sodium hydroxide or sodium silicate... 

Re-alkalization is another form similar to the electrochemical chloride extraction process, and is used to recreate the alkaline conditions which are lost due to carbonation. As stated in an earlier section, the ingress of carbon dioxide leads to the loss of alkalinity on the reinforcement because of the fall of pH firom 14 to 9 due to the combination of carbon dioxide with calcium hydroxide [Ca(OH)2] which means loss of alkalinity from the concrete. 

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