Neutralization of waste

Other developing or potential appHcations for lime are neutralization of tail gas from sulfuric acid plants, neutralization of waste hydrochloric and hydrofluoric acids and of nitrogen oxide (NO ) gases, scmbbing of stack gases from incinerators (qv), and of course, from small industrial coal-fired boilers. 

Figure 7-10 A control system for the neutralization of waste by reagent R.

The problem of the neutralization of waste water from the manufacture of TNT, and the possibility of utilizing the dinitrotoluenesulphonic acids present in them acquired a considerable importance during World War II, owing to the enormous output of TNT. In Germany alone the production of TNT was over 20,000 tons a month, whereas during the World War I it averaged merely 3000 tons a month. 

Commercially, spray towers are suitable for hquid-hquid processes in which rapid, irreversible chemical reactions occur, as in neutralization of waste acids. The substantial hterature of flooding, holdup, mass transfer and axial mixing in small spray towers is reviewed by Laddha and Degaleesan (1978, pp. 221-255) and more briefly by Cavers (in Lo et al., 1983, pp. 320-328). 

An alternative to the concentration of waste acid and reuse thereof, is neutralization of waste acid with calcium carbonate and using the gypsum formed either in the construction industry or for land infill, depending upon purity. 

Only a fraction of the lime employed in such processes is chemically consumed. The residual calcium oxide, comprising up to two-thirds of weight of the precipitator catch, provides the inexpensive and convenient source of base for neutralization of waste but unrecoverable sulfuric acid. By using the residual chemical activity of both waste streams, the disposal problems and costs of dealing with each of them are decreased. 

MAJOR USES Component in food processing used in environmental applications for pH control, neutralization of waste streams, treatment and general cleaning used in industries of electroplating, leather tanning, steel pickling and photography antiseptic toilet bowl cleaner. 

C 400-93 Test methods for quicklime and hydrated lime for neutralization of waste acid . 

Elementary neutralization of waste that is hazardous only because of the characteristic of corrosivity. 

The rate of the reaction was found to be high, reducing the concentration of test samples from 7000 to less than 10 ppm In 0.5 h. This level Is deemed satisfactory for neutralization of waste and spills. 

The obtained dependence shows that pH of the cellulosic sorbent changes slightly with respect to the initial solution. The use of carbonate rocks increases this index to pH 6.5-7.7 depending on the weight. This takes place because of the increased content of hydroxyl groups when hydrolysing carbonates. This is an important characteristic when selecting a sorbent for the neutralization of waste waters in the purification process of industrial acidic drains. 

Protection of the environment from the impurities originating from industrial wastes and transportation means is a very important and current problem. Adsorbents play a significant role in neutralization of waste gases and sewages and at the same time in capturing valuable components found in wastes. Compared with other methods, adsorbents allow for the most thorough purification of raw materials with relatively low costs. 

---