Even though nanoscale zero valent iron (nZVI) has been intensively studied for the treatment of a plethora of pollutants through reductive reaction, a quantification of nZVI reactivity has not been standardized. Here, we developed series of colorimetric assays for determining reductive activity of nZVI and its composite with granular activated carbon (GAC). The assay focused on analysis of reaction products rather than its mother compounds, which gives more accurate quantification of reductive activity. The colorimetric assays were developed to quantify three reaction products, ammonia, phenol, and aniline, generated as results of reduction of nitrate, halophenols, and nitrobenzene, respectively. The color reactions are simple and versatile since same types of reagents are able to be applied for all reactions. The colorimetric assays were further miniaturized and optimized into 96-well microplate having 230 μL of sample volume and 2 h of reaction time. The three groups of compounds, nitrate, nitrobenzene, and para-positioned halogenated phenols, showed graduated reactivity and were possible to distinguish a reaction mechanism between normal reduction and catalytic behaviour of second metal. The applicability was successfully proven by determining reactivity of GAC/Fe(0) composite prepared in various reduction conditions. It was shown that reactivity of GAC/Fe(0) was significantly influenced by reduction conditions, i.e. pH and reduction time, and addition of second metal further increased its reactivity. The preliminary results of GAC/Fe(0) reactivity obtained by suggested assay would be useful to determine suitable reaction condition for remediation work and estimate efficiency and required time. Therefore, suggested reactivity test with different compound combined with multiwell microplate based color assay will be useful and simple tool in various nZVI related research topics, e.g. different stabilization, immobilization, etc.

Microplate based colorimetric assays for characterization of redox reactivity of nano materials for water treatment

254th National Meeting (2017)

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