Abstract
In a practical double nickel plating process, nickel concentration tends to increase in the bright bath, but to decrease in the semi-bright bath. For this process, the following recycle was studied; the first brightener containing sulfur was removed from a Watts type bright bath by an adsorption process through a column packed with polymeric adsorbents, and the bright bath treated with the adsorbents was utilized as a part of the semi-bright bath. In this work, sodium p, p′-ditoluensulfonimide (DTI) was used as the first brightener and Amberlite XAD-7 (XAD-7) as the polymeric adsorbent. The concentration of DTI was measured by optical absorption. As a result of treating the bright bath by means of the column method, it was found that DTI is removed by adsorption on XAD-7, and DTI adsorbed on XAD-7 is desorbed by water. In the range of 0.8 to 6.7g/l of DTI, the adsorption amount was 25g/l-XAD-7 until DTI leakage became 20mg/l. Besides, the adsorption capacity of XAD-7 is not decreased by the repeated cycles of adsorption and desorption of DTI. The adsorption of DTI on XAD-7 mainly results from the salt-out effect of nickel salt in the bath.
