Mass Transfer
Radioactive nuclear waste is treated in

Mixer-settler extractor
Rotating-disc contactor
Bollman extractor
Pulsed column extractor

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Mass Transfer
Use of raschig rings in place of crushed stones as packing in packed beds (other things being same)

Increases pressure drop, decreases surface area
Decreases pressure drop, increases surface area
Increases pressure drop, increases surface area
Decreases pressure drop, decreases surface area

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