Abstract

ERASMUS, E; CLAASSEN, JO  and  VAN DER WESTHUIZEN, WA. Catalytic wet peroxide oxidation of formic acid in wastewater with naturally-occurring iron ore. Water SA [online]. 2016, vol.42, n.3, pp.442-448. ISSN 1816-7950.  http://dx.doi.org/10.4314/wsa.v42i3.09.

The catalytic wet oxidation of formic acid, using hydrogen peroxide as the oxidizing agent over naturally-occurring iron ore, was explored. Firstly, the decomposition of hydrogen peroxide to its hydroxyl radicals (HO^- and HOO^-) over naturally-occurring iron ore was investigated. The reaction was monitored by ATR FTIR by following the disappearance of the O-H peak of H₂O₂ at 2 860 cm^-1. Decomposition occurred according to the Fenton mechanism and resulted in observed first-order rate constants one order of magnitude faster than that without the catalyst. Turnover frequencies (TOF) of 1.97-8.85 x 10^-9 s^-1 were obtained for the decomposition of H₂O₂. The wet oxidation of formic acid using hydrogen peroxide as the oxidizing agent over naturally-occurring iron ore reaction was also monitored by ATR FTIR, following the disappearance of the carbonyl stretching frequency of formic acid at 1 727 cm^-1. Experiments were performed at different hydrogen peroxide (2, 4, 6 and 8M) and formic acid (1.26, 2.52, 6.3 and 12.6 M) concentrations as well as with varying amounts of naturally-occurring iron ore catalyst, at pH = 2. Elevated hydrogen peroxide and formic acid concentrations led to increased observed first-order kinetics, as high as k_obs= 21.75 x 10⁴ min¹ with a TOF = 1.73 x 10^-8 - 1.12 x 10^-6 s^-1.

Keywords : iron ore; catalytic wet oxidation; formic acid; Fenton; hydrogen peroxide.

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