Experimental Study on Treatment of Formic Acid Wastewater by Chemical Oxidation
The mineralization of formic acid(FA)wastewater produced by nitrate catalytic reduction reaction was studied based on ultraviolet and electrochemistry.The results showed that although the direct photolysis process could not completely mineralize formic acid,the mineralization of formic acid was significantly improved when heterogeneous photocatalysis(HP),photo-assisted electrochemical oxidation(PEO)and electrochemical oxidation(EO)were used.It was shown that the mineralization of formic acid was controlled by electrochemical processes,which played a dominant role.In the presence of added nitrate,all treatment processes exhibited an increase in formic acid mineralization,especially for the direct photolysis process.For UV-based treatment processes,this increase could be attributed to the production of hydroxyl radicals(HO·)by photolysis of nitrate.On the other hand,the increase in mineralization during electrochemical oxidation was associated with an increase in charge transfer,arguing that the oxidant generation was a rate-limiting process,showing pseudo-zero order constants for DP and HP,whereas photo-assisted electrochemical oxidation and electrochemical oxidation processes showed pseudo-first order reactions.Optimal FA mineralization with minimal energy consumption was obtained by the electrochemical process.Furthermore,the EO process was not negatively affected by nitrate addition.
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