Reactive Rinsing

Water from the nickel rinse tank can be fed back into the acid dip rinse tank, allowing nickel plating solution dragged out of the process bath to be dragged back into it. This will not harm the rinse, and will allow the water feed to the acid rinse tanks to be turned off. Thus, both water and process chemicals are conserved, and the quantity of toxic process chemicals in the effluent is reduced. 

The acid rinse can be further recycled to the alkaline cleaner rinse tank. This conserves water by allowing the fresh water feed to the alkaline rinse to be turned off, and also improves rinsing efficiency by helping to neutralize the dragged in alkaline solution. This will prolong the life of the acid bath because the rinsewater dragged into it will already be partially neutralized. Thus the acid bath will not have to be dumped as often. 

While reactive rinsing can help to save water and improve rinsing efficiency, it must be used with caution, because precipitation problems can occure when acid and alkaline solutions are mixed. 

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After rinse solutions become too contaminated for their original purpose, they may be useful for other rinse processes. For example effluent from a rinse tank that follows an acid cleaning bath can sometimes be reused as influent water to a rinse tank following an alkaline cleaning bath. This reactive technique was discussed in Section 1322.3. Reactive rinsing must be used with caution, however, for it can lead to precipitation problems. 

Cold Exhaust Dyeings Fiber-Reactive Dyes. Start at 25—30°C optionally with a sequestrant and maintain. The dye is added over 5 min, then there is portionwise addition of salt every 10—15 min, increasing the size of the addition each time over 1 h. The amount of salt used (10—100 g/L) depends on the depth of shade. After the final addition of salt, wait 15 min, portionwise add soda ash (10—20 g/L) over 15 min, and continue dyeing for 30—45 min. Drop dyebath, cold water rinse, and use a sequence of hot washes to remove all loose "unfixed" dye. 

Chemical Reactivity - Reactivity with Water No reaction Reactivity with Common Materials Corrosive, particularly when diluted. Attacks most common metals, including most stainless steels. Excellent solvent for many synthetic resins or rubber Stability During Transport Stable Neutralizing Agents for Acids and Caustics Dilute with water, rinse with sodium bicarbonate solution Polymerization Not pertinent Inhibitor of Polymerization Not pertinent. 

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