CHARACTERIZATION OF THE PRODUCTS OF ELECTROCOAGULATION AT IRON ELECTRODES FOR IMPROVEMENT OF WASTEWATER TREATMENT

摘要

Twenty-five years ago, to stimulate economic growth, Mexico encouraged foreign-owned companies to build facilities, known as maquiladoras, along the border for production and assembly of products for export to the United States. The passage of NAFTA made it easier for U.S. companies to build these facilities and now 60% to 70% of the maquiladoras are U.S. owned. Unfortunately, as pointed out by Jose Bravo of the Southwest Network for Environmental and Economic Justice, "Few follow U.S. or Mexican environmental law, therefore, unsafe and unhealthy working conditions, hazardous waste dumps, contaminated water, contaminated air, and uncontrolled contamination from industrial facilities dominate life in most border towns". Heavy metal contamination exists in aqueous waste streams of many industries, including metal plating facilities, printed circuit board manufacturing, coal-fired power plants, and industrial operations that involve the processing of ferrous and non-ferrous metals. The soils surrounding many military bases are also contaminated and pose a risk of metals in groundwater and surface water contamination. Some metals associated with these activities are cadmium (Cd), chromium (Cr), arsenic (As), lead (Pb), and mercury (Hg). The heavy metals are not biodegradable, and tend to accumulate in living organisms, causing various diseases and disorders. The purpose of this research is to investigate the use of a novel method for the minimization of toxic metals in the wastewater from the Mexico-U.S. border region. A very promising electrochemical treatment technique, which does not require chemical additions, is Electrocoagulation (EC). The EC process operates on the principle that coagulation of contaminants from an aqueous medium is caused by the combined effects of electrolysis gases (H_2 and O_2) and the electrolytic production of cations from iron and aluminum anodes that corrode during electrolysis. This study reports on the products of electrocoagulation as part of an effort to explore the parameters that can be most effectively manipulated to improve the overall process. Understanding the fundamental mechanisms of electrocoagulation will allow the design of more effective wastewater treatment processes.