Electrochemical Treatment for Wastewater Contained Heavy Metal the Removing of the COD and Heavy Metal Ions
Abstract
In this work, the goal for an optimum condition of the electrochemical oxidation technique which is used to treat the wastewater from the metal finishing process, was experimentally investigated and obtained. All the experiments were carried out with the effects of operational parameters such as pH value, current density, electrolysis time, chemical oxidation demand (COD), removal efficiency are determined. Because of the property of the wastewater itself which conclude a lot of metal ions, means we don’t have to use any of electrolyte solution, Carbon Cloth (5x5 cm) and Platinum wire were proved to be the best cathode and anode materials here respectively. The applied current density are from a solar penal (17 mA), when we don’t actually control the pH value, the percentage of COD removal reached 52%, and the removal efficiency of metal ions was 22.5%. Our work focused on decreasing the quantity of heavy metal ions of the wastewater, as long as achieving a high COD removal efficiency by controlling the four key factors which were electrodes, working temperature, pH value and a fixed value of applied current.
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Introduction
Since the 20th Century, our world was improving so fast with the rapid development of industries and technologies, such as power generation facilities, green energies, electronic device manufacturing units, metal industries, the more advance they provided, the more waste they released. During the last two decades, a huge amount of industrial wastewater was discharged into rivers, lakes and other areas. Industrial wastewater is one of the main pollution sources among the pollution of the water environment. Wastewater from metal finishing industries contains heavy metals and other species belongs to the group of persistent toxic substance, which is considered to be hazardous to the environment, human health, irritates plants and animals. Heavy metals are concerned because of their toxicity, which is typically present in metal finishing wastewater with cadmium, chromium, copper, lead, silver, zinc and tin.
Table 1 shows the EPA (the United States Environmental Protection Agency) best practical control technology, BPT, limits for metal finishing effluent [1]. In the present days, water has become a vital resource which is limited and in many cases, there will be not enough water with appropriate quality to supply for both domestic use and industrial at the same time. According to this situation, there is an urgent need to apply an effective, innovative and reasonable technique for the treatment of wastewater, especially the industrial wastewater.
In literature, there were several technologies can be used to treat those industrial flow streams, but electrochemical treatment seems to be a very promising and suitable technique which requires a minimal additives, high effectiveness, low maintenance cost, rapid achievement of results and less need for labor [2]. Previous researches indicates the relationship between those electrochemical processes which is believed to have three possible mechanism involved: EC (Electrocoagulation), EF (Electro-flotation), and EO (Electro-oxidation) [3].
In this work, we use the EC (Electro-coagulation) to treat the wastewater of the metal industry, in which contains heavy metal ions, without the supports of any electrolyte and additives. Our process is not only different with other conventional processes before, but also proved it’s effectively results with further room to improve. According to Chen et al [4], EC has many advantages over the others coagulation process, and has been proven to be one of the best process for wastewater treatment [5], The process is an electrochemical production of destabilization agents which usually is noble metal, the noble metal works as a couple of electrode that bring the neutralization of electric charge for removing pollutants. With the support from the electricity, the metal nano-particles can be charged and act like small magnets to form a mass. During the EC process, the coagulant is generated by the electrolysis oxidation of anode material; the charged ionic particles are removed by reaction among oppositely charged ions, or with flocs of metallic hydroxides [6].
Conclusion
The electrolysis has been long used as a very positive and reliable method to treat the wastewater contains heavy metal ions. The process itself was a cost effective process, moreover, electrolysis also has significant advantages such as its simple equipment, convenient operation and non-requirement of chemical substance. Our work focused on decreasing the quantity of heavy metal ions of the wastewater, as long as achieving a high COD removal efficiency by controlling the four key factors which were electrodes, working temperature, pH value and applied current. According to the results that we obtained, the whole process allows the wastewater treatment to reduce the organic contaminants, and also electrochemically oxidized without adding any additives, with the support of a small current density by solar cell, and thus we believe the process was not only saving energy but also a green eco-friendly process, that can be put in use for the advantage of an economic aspects in the near future.