Removal of chromium from electroplating wastewater by simple chemical treatment and ion exchange

Abstract EN

Wastewater from metal plating works was treated with lime-water suspensions at relatively small concentrations with continuous stirring.

Experiments were designed to allow a direct contact of lime suspension with the wastewater constituents for a period of time followed by settling and filtration through a sand filter.

The heavy metal content could be precipitated efficiently from the mother liquor by two mechanisms : reaction with calcium ions to yield calcium chromate and the precipitation of the chromium hydroxides in the alkaline medium.

Various parameters were studied to reach the optimum conditions for the removal of chromium from the wastewater.

It appeared that reasonable removal of chromium (80 _ 85(% could be achieved with lime : wastewater ratio of 40 mg / L and 50 min contact time.

After the removal of most of the chromium from wastewater, the level of the pollutant needed to be reduced to the acceptable limit by passing water through ion exchange column.

This final treatment gave treated water samples with chromium levels as low as 0.6 - 1.3 mg / L.