Design of Quinonoid-Enriched Humic Materials with Enhanced Redox Properties

Abstract

The primary goal of this work was to develop quinonoid-enriched humic materials with enhanced redox properties that could be used as potentially effective redox mediators and reducing agents for in situ remediation of soil and aquatic environments. Two different strategies were formulated and tested to derive these materials. The first strategy called for the oxidation of phenolic fragments associated with the humic aromatic core. In a second strategy, polycondensation of these phenolic fragments was carried out with hydroquinone and catechol. The oxidized derivatives and copolymers obtained were characterized using elemental and functional group analyses, and capillary zone electrophoresis. The redox properties were evaluated using ESR spectrometry and reducing capacity determinations. The reducing capacities of copolymers ranged between 1 and 4 mmol/g, which were much higher than the parent material and the oxidized derivatives. Hence, preference should be given to the copolycondensation approach. The quinonoid-enriched humics are nontoxic, water soluble, and resistant to biodegradation; thus, they could be applied as soil amendments to reduce highly mobile oxoanions of heavy metals and radionuclides, or as redox mediators to enhance in situ bioremediation. Otherwise, cross-linked copolymers could be created to serve as inexpensive reductants in permeable reactive barriers designed to remove highly oxidized contaminants from polluted groundwaters.

Pollutant toxicity and detoxification by humic substances: mechanisms and quantitative assessment via luminescent biomonitoring

“…Detoxifying properties of HS in solutions of oxidizers are generally attributed to HS reduction ability (Matthiessen 1996;Skogerboe and Wilson 1981); phenolic, SH, and other groups of HS macromolecules can be responsible for the reduction of oxidizers. Evidence has been accumulated that HSs, and their quinoid moieties, in particular, play an important role as electron shuttles in microbial redox reactions involved in biodegradation of pollutants (Perminova et al 2005;Osterberg and Shirshova 1997). As reported in (Perminova et al 2005), the values of formal electrode potentials for natural HSs vary from 0.328 to 0.78 V.…”

“…Evidence has been accumulated that HSs, and their quinoid moieties, in particular, play an important role as electron shuttles in microbial redox reactions involved in biodegradation of pollutants (Perminova et al 2005;Osterberg and Shirshova 1997). As reported in (Perminova et al 2005), the values of formal electrode potentials for natural HSs vary from 0.328 to 0.78 V.…”

“…Among the effects of HS in the environment, increasing evidence indicates that they can act as natural attenuators of toxicity of oxidizers (Tarasova et al 2011(Tarasova et al , 2012Fedorova et al 2007;Perminova et al 2005;Zhilin et al 2004;Gu and Chen 2003;Orlov 1997). Detoxifying properties of HS in solutions of oxidizers are generally attributed to HS reduction ability (Matthiessen 1996;Skogerboe and Wilson 1981); phenolic, SH, and other groups of HS macromolecules can be responsible for the reduction of oxidizers.…”

Effect of humic substances on toxicity of inorganic oxidizer bioluminescent monitoring

“…Interaction of xenobiotics with HS causes the formation of complexes of lower bioaccumulation and toxicity [13]; quinoid, phenolic, sulfhydryl, and other groups are responsible for redox activity of HS-macromolecules. Evidence has accumulated that HS, and particularly their quinoid moieties, can play an important role as electron shuttles in microbial redox reactions involved in biodegradation of pollutants [14].…”

Humic acid model substances with pronounced redox functionality for the study of environmentally relevant interaction processes of metal ions in the presence of humic acid

“…Matthiessen (1995) synthesized a HA from hydroquinone to determine the redox capacity of humic substances as a function of pH. Perminova et al (2005) developed quinonoid-enriched humic materials with enhanced redox properties by oxidation of phenolic fragments associated with the humic aromatic core or by polycondensation of these phenolic fragments with hydroquinone and catechol. These materials shall be used as effective redox mediators and reducing agents for remediation of soil and aquatic environments.…”