Authors: M. Mullett and L. Mohamed
CHEMECA 2009, September 28, 2009
Abstract
It has been estimated that 6000 tons per year of mercury are released into the
environment, 4000 tons from anthropogenic sources. The adverse effects of mercury on
both human and animal health have led to regulators enforcing increasingly stringent
discharge limits. Limits as low as 10 μg/L are typical in many jurisdictions. A proven
technique for removing and immobilising mercury from wastewaters is adsorption onto
activated carbon. The adsorption capacity for mercury onto the carbon is significantly
influenced by the concentration of mercury in the solution phase. Therefore more
efficient use of the carbon would arise from increasing the concentration of the mercury
in the stream presented to the carbon bed. This investigation assessed the viability of
using cross-flow reverse osmosis filtration (RO) to concentrate the mercury in a smaller
aqueous stream. A series of flat-sheet membrane tests were conducted at pH 2 and 7
using a feed solution with a concentration of 30 mg/L Hg. The data produced was
modelled and a filtration plant design determined. For each pH tested, it was predicted
that RO will concentrate the mercury from at a range of feed concentrations into a low
volume retentate stream using a multi-pass configuration. The resulting permeate stream
would achieve the strict regulatory mercury discharge limit of < 10 μg/L.
