Improved hydrogen gas production in electrohydrolysis of vinegar fermentation wastewater by scrap aluminum and salt addition

Abstract

Scrap aluminum particles and salt (NaCl) were added to the vinegar fermentation wastewater to improve hydrogen gas formation by electrohydrolysis of the wastewater organics. The applied DC voltage and initial COD of the wastewater were constant at 4 V and 33.16 g L−1, respectively. The highest cumulative hydrogen gas formation (2877 mL) was obtained with scrap Al (1 g L−1) and NaCl (1 g L−1) additions within 72 h as compared to 1925 mL H2 gas formation from raw wastewater. Hydrogen gas formation from Al and NaCl added water was 302 ml as compared to 260 ml from raw water. The highest H2 gas formation rate (952 mL d−1), the yield (1660 mL H2 g−1 COD) and the highest current intensity (163 mA) were also obtained with combined effects of scrap Al and NaCl additions. Almost pure hydrogen gas (99%) was produced using the raw wastewater. Initial conductivity of the raw wastewater increased from 1.80 mS cm−1 to 5.01 mS cm−1 with the addition of scrap Al and salt for which the final conductivities were 4.0 mS cm−1 and 6.91 mS cm−1, respectively. The highest energy conversion efficiency was obtained with only scrap Al addition (37.8%) as compared to 30.5% efficiency obtained with Al and salt additions. Additions of NaCl and scrap Al particles was found to be very beneficial for H2 gas formation by electrohydrolysis of vinegar fermentation wastewater.