Advantages

These include the following:

1. Very little change to production process

2. More consistent product quality

3. Easier monitoring of the amounts of water and process chemicals used

4. Much reduced chromium content in the effluent waters.

Collected spent tanning liquor

Add magnesium oxide and polyelectrolyte control acidity stir

Stop stirring let settle

Collected spent tanning liquor

Add magnesium oxide and polyelectrolyte control acidity stir

Sulfuric

1

acid

A

c

H

1 1

STËPS

► Ready for use as tanning agent

Decant lean layer

Control acidity and stir

Stop stirring let settle

Decant lean layer

Control acidity and stir

► Ready for use as tanning agent

FIGURE 1.9 Five-step batch process for chromium recycling. (From Wang, L.K. et al. Case Studies of Cleaner Production and Site Remediation, Training Manual DTT-5-4-95, United Nations Industrial Development Organization, Industrial Sectors and Environment Division, Vienna, Austria, April 1995.)

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DIY Battery Repair

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