Treatment of defense industry wastewater with electrocoagulation (ec) method

Industrial wastewater is the major source of hazardous bio-accumulative and highly soluble toxic heavy metals like arsenic, copper, chromium, cadmium, nickel, zinc, lead, and mercury in the aquatic environments. There has, therefore, always been a need for the removal and/or recovery of these toxic, non-biodegradable, and persistent heavy metals from the defense industry wastewater. The defense industry wastewater was treated with electrocoagulation (EC) using a sacrificial Fe, Al and hybrid Fe-Al electorode in a batch reactor. In EC process, TOC, toxicity, and heavy metal contents of the wastewater were decreased during 30 min retention time as a result of response surface methodology (RSM) optimization with following parameters; current density (10.0, 15.0 and 20.0 mA/cm2) supporting sodium sulfate electrolyte amount (0.0, 5.0 and 10.0 mM Na2SO4) and initial water pH (3, 6 and 9). It was observed that the main metal and heavy metal contents were Ni, Zn, Cu, Cr, Mn, Co, Ag, Pb ve As when their concentrations were listed in descending order at the level of mg/L, and these heavy metals were removed more efficiently in the EC process. The best TOC removal (99.476%) was seen at current density 15 mA/cm2, Na2SO4 0 mM, and influent wastewater pH 9.The FTIR-ATR spectrum of the sludge observed the strong peaks around 875 cm−1 and 884 cm−1 related to vibrations of the Fe–O bonds in iron oxide after the EC. This study showed that defense wastewater was successfully treated with EC first time in the literature even if it had high TOC, toxicity, and heavy metal contents.