Removal of furfural using zero gap electrocoagulation by a scrap iron anode from aqueous solution

[Display omitted] •A new electrochemical reactor for the removal of furfural was employed.•The distance between the scrap iron anode and the cathode is about zero-gap.•The complete removal of the furfural without the use of any chemical was obtained.•The electrocoagulation process exhibited low current density and energy consumption at neutral pH.•The most abundant intermediates derived from furfural degradation were maleic acid, acetic acid, and formic acid. In the present study, furfural removal by a new electrochemical reactor with a zero-gap distance between the scrap iron anode and the cathode from aqueous solutions was investigated. The effects of the operational parameters, including initial furfural concentration (100–600 mg/L), current density (0.68–3.44 mA/cm2), solution pH (4–11), and hydraulic retention time (5–180 min), were evaluated.The experimental results indicated that a current density of 2.75 mA/cm2, an initial furfural concentration of 100 mg/L, and a pH of 7.0 were the most favorable conditions for the complete removal of furfural (>88 %) within 120 min of hydraulic time. Based on the LC-MS analysis, furan-2-carboxylic acid, furan-2-yl hydrogen carbonate, furan-2-ol, furan-2(5H)-one, maleic acid, acetic acid, oxalic acid, and formic acid were the main intermediates identified in furfural degradation. The TOC and COD removal rates were 64.75 and 75.62 % in the zero-gap electrocoagulation (ZG-EC) system under the optimized conditions, respectively. According to the kinetic results, the rate of furfural removal by the ZG-EC process followed the pseudo-first-order kinetics (R2 > 0.9). Finally, the degradation pathway of furfural using the ZG-EC process is proposed.