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Abstract
The imposition of more stringent legislation governing the disposal and utilisation
of sewage sludge, coupled with the growth in its generation and the loss of traditionally
accepted disposal routes, has prompted a drive for alternative uses for sewage sludge.
One option that exhibits special promise, due to its potential to valorise the sludge,
is the conversion of the sludge into adsorbents. This paper seeks to review the published
research in this field: it covers the means of production, the characteristics and
the potential applications of sewage sludge-based adsorbents (SBAs). The literature
has indicated that chemical activation utilising alkali metal hydroxides is the most
effective technique for producing high surface area SBAs. In addition, acid washing
is highly effective at raising the BET surface area of SBAs, especially when coupled
with physical activation. Due to their relatively low microporosity, the phenol uptake
of SBAs produced by physical activation is low, but through a combination of their
favourable surface chemistry and relatively high mesoporosity, the best of these adsorbents
can attain high uptakes of organic dyes. The SBAs produced by carbonisation, through
their high cation exchange capacity, generally exhibit a high metal cation capacity.
For further research, the following investigations are recommended: the utilisation
of alternative chemical activation reagents; the optimisation of the most effective
chemical activation techniques; the combined utilisation of different activation and
surface chemistry modification techniques to produce application-specific adsorbents.