25 research outputs found
Character of Humic Substances as a Predictor for Goethite Nanoparticle Reactivity and Aggregation
Natural organic matter
(NOM) is ubiquitous in surface water and
groundwater and interacts strongly with mineral surfaces. The details
of these interactions, as well as their impacts on mineral surface
reactivity, are not well understood. In this work, both the reactivity
and aggregation of goethite (α-FeOOH) nanoparticles were quantified
in the presence of well-characterized humic substances. Results from
monitoring the kinetics of reductive degradation of 4-chloronitrobenzene
(4-ClNB) by Fe(II) adsorbed onto the goethite nanoparticles with and
without added humic substances demonstrates that, in all cases, humic
substances suppressed Fe(II)–goethite reactivity. The ranking
of the standards from the least to most inhibitive was Pahokee Peat
humic acid, Elliot Soil humic acid, Suwannee River humic acid, Suwannee
River NOM, Suwannee River fulvic acid I, Suwannee River fulvic acid
II, and Pahokee Peat fulvic acid. Correlations between eight characteristics
(molecular weight, carboxyl concentration, and carbon, oxygen, nitrogen,
aliphatic, heteroaliphatic, and aromatic content) and 4-ClNB degradation
rate constants were observed. Faster kinetic rates of reductive degradation
were observed with increased molecular weight and nitrogen, carbon,
and aromatic content, and slower rates were observed with increased
carboxyl concentration and oxygen, heteroaliphatic, and aliphatic
content. With these correlations, improved predictions of the reactivity
of Fe(II)–goethite with pollutants based on properties of the
humic substances are possible