Wastewater treatment, inorganic chemicals process wastes

Miscellaneous. Hydrochloric acid is used for the recovery of semiprecious metals from used catalysts, as a catalyst in synthesis, for catalyst regeneration (see Catalysts, regeneration), and for pH control (see Hydrogen-ION activity), regeneration of ion-exchange (qv) resins used in wastewater treatment, electric utiUties, and for neutralization of alkaline products or waste materials. In addition, hydrochloric acid is also utilized in many production processes for organic and inorganic chemicals. 

Oxidation of organic and inorganic species in aqueous solutions can find applications in fine chemical processes and wastewater treatment. Here, the oxidant, often either air or pure oxygen, must undergo all the mass transfer steps mentioned above in order for the reaction to proceed. During the last decade, increased environmental constraints have resulted in the application of novel processes to the treatment of waste streams. An example of such a process is wet air oxidation. Here, the simplest reactor design is the cocurrent bubble column. However, the presence of suspended organic and inert solids makes the use of monolith reactors favorable. 

Even if care is taken to minimize waste, there will still be waste to treat. Currently used wet finishing processes produce waste containing organic as well as inorganic compounds. The efflnents are rich in chemicals of which some are persistent or resistant to water treatment methods. Table 2.1 lists typical examples of finishing waste that resists biodegradation. Removal of these substances from wastewater is expensive and difficult to achieve. Because of this, the effiuent segregation and source reduction methods are preferred as economically attractive alternatives. 

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