The document discusses the toxic effects of hexavalent chromium on humans and aquatic life, highlighting its use in various industries and the large quantities discharged as waste. It describes an experimental setup for reducing chromate using a flow method through a packed column of granulated slag and glass beads, with measurements taken to determine chromate concentration. This reduction process aims to mitigate environmental impacts caused by chromium compounds from industrial processes.

1. REDUCTION OF CHROMATE
By sreeremya.s
Asst professor,sree narayana guru
college,cbe

2. • Hexavalent chromium is toxic not only to man
but
• also to fish for which 1.2 - 5.0 ppm of
chromate have
• been found to be fatal

3. • They are employed in the manufacture of
paint
• pigments, in chrome tanning, aluminium
anodizing and
• other metal cleaning, plating and
electroplating
• operations. The concentrations (mg/1) of
chromium (VI)
• have been reported to be as follows

4. • Wood
• preserving 0.23-1.5, cooling tower blow down
10-60,
• leather tanning 40, electroplating bath 15-70,
anodizing
• bath 15000-52000, dip bath 2000-75000.

5. • The amount of chromium compounds
discharged through the waste streams of
metal finishing industry is estimated to about
2.81 x 107 kg/year 8. 2 X 106 kg (as sodium
dichromate). Approximatelyof chronium (as Cr
• 2o3) are lost as waste from sodium
dichromate manufacture each year.

6. • Chromate Reduction By the Flow Method
• A glass column (ht. 50 em, dia 2.5 em) was packed
• with 25 g of granulated slag (2-4 mm) from a steel plant.
• While packing, the same weight (25 g) of glass beads was ~
• added to the slag to facilitate a convenient flow within
• the column. Distilled water (20 ml) was then placed in
• the column to s~bmerge the contents of the column. The
• chromate solution of known concentration and acidity was
• placed in a separatory funnel, and the chromate solution
• was allowed to flow at a rate of 4.2-5.2 ml/min. The
• first collection (20 ml) of the effluent which contained
• mostly distilled water was rejected.

7. • vessels, and the concentrations of chromate were
• determined titrimetrically using standard ferrous
• ammonium sulfate solution, and ferroin as
indicator. The
• experiment was repeated using different
concentrations
• of chro'~ ite solutions, each time using a freshly
packed
• column.