Lignin-derived carbon materials as catalysts for wet peroxide oxidation
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resumo
Lignin is one of the most abundant organic polymers in the nature, and is obtained in large amounts
as a residue in paper and cellulosic bio-ethanol production industries (5-36x108 T/year) [1,2]. A
major part of this industrial lignin is incinerated for energy production [3]. Nevertheless, the
utilization of lignin as a fuel is not economically rational [3], and the development of alternative
uses for lignin has been increasing in interest over the recent years. Due to its high carbon content
and to a structure similar to that of bituminous carbon [2], it seems to be an adequate precursor for
the production of activated carbon materials. Several examples can be found in the scientific
literature regarding the preparation of activated carbons from lignin, using different procedures
[4-6]. Highly porous materials have been developed, with specific surface areas (SSA) ca.
2000 m2 g-1 and adsorbent capacities comparable to those reported for a number of commercial
activated carbons [7].
Advanced oxidation processes, primarily based on the action of hydroxyl radicals (HO) to oxidize
organic pollutants, are regarded as promising solutions for the treatment of aqueous effluents
containing recalcitrant and non-biodegradable compounds [8,9], typically found in wastewaters of
several industries (pharmaceutical, petrochemical, dyes, paper…). These type of compounds are
particularly difficult to remove by conventional biological processes, mainly when present at high
concentrations (1-10 g L-1) [10]. Among advanced oxidation processes, catalytic wet peroxide
oxidation (CWPO) uses hydrogen peroxide (H2O2) and a suitable catalyst to promote the formation
of the HO, for the degradation of the organic species, under relatively mild operation conditions
(0.1-0.2 MPa, 20-130º C).
