Abstract
The present research work had as study variables the current density of 20, 40 and 80 mA/cm2 and residence times of 10, 20, 40 and 60 minutes, within these evaluation parameters values were taken of pH, conductivity and Fe2+ removal percentage before and after the electrocoagulation process of artisanal acid mine drainage samples (AMD), the amount of AMD sample per test was 350 mL per test, from the results obtained it could be observed that For the current density of 80 mA/cm2 and a time of 40 minutes, the highest percentage of removal was obtained (76.20%), likewise a minimum percentage of removal of 17.97% was obtained at 20 mA/cm2; The removal percentages are attributed to the effect of the current density of the electrocoagulation process, which allows increasing the initial pH values of the effluent, which in turn allows the formation of precipitates and co-precipitates, in this case of Fe2+.
Highlights
Acid Mine Drainage (AMD) is one of the most serious types of water pollution, due to its nature, extent and difficulty of resolution, as well as the economic costs of its traditional remediation; The rivers affected by this type of pollution are characterized by their acidity, as well as by the high content of sulfates and heavy metals in their waters and by the metallic content of their sediments
2.1.- Preparation of the working electrodes: As working electrodes, AISI 304 steel and 1000 series aluminum plates were adapted, they will be cleaned superficially, until they do not have any contaminants such as oils, grease or dust, as well as the lids of each of the plastic containers used as cells, they were drilled with the help of a metal or hot plate, in order to mount all the accessories of the equipment necessary to carry out the electrocoagulation process
Reduction percentage of divalent iron: Table 4 and Figure 2 show the average values of the Fe2+ removal percentage from the acid mine drainage, with respect to time and current density used in the electrocoagulation process
Summary
Humanity has had the need to use metals and has always sought methods to extract them; In this way, since those remote times, mining has existed and with it the effects of the process, whether in the air, soil or bodies of water, which are being attended to with increasing intensity; A very particular case is that of the generation of acidic waters from mining and extractive activities; This phenomenon occurs due to the release of mineral sulfur agents to the water and in combination with the air (oxidation) they alter the initial conditions of the water, such as pH, to values lower than 7, in a similar way this acidification process occurs due to the high dissolution of sulfates in bodies of water, this runs the risk of significantly altering and / or modifying river habitats. Remediation treatments generally achieve their objectives due to the use of chemical agents, which should be used in a controlled way according to their need, which does not happen, since we almost always use chemical compounds in excess in order to achieve the expected modifications In this way, substances are added that the bodies of water did not have, there are treatments that follow the principles of chemical neutralization but with the advantage of the controlled use of reactants and products, such processes are called electrochemicals, which generate in situ the agents necessary for the control processes, in this case of acidic waters, but that can be used in theory in all bodies of water to be treated, with the difference of the control of electrolyte conductivity, initial pH, anodes and cell cathodes , electrical parameters of the process, volume of water body, among others; Among these methods we have the so-called electrocoagulation, which in our case was used in search of reducing the cation content and increasing the initial pH of the water samples. The basic principle of electrocoagulation is the electrolysis process; During electrocoagulation, the most important chemical reactions involve the dissolution of metal cations at the anode and the formation of hydroxyl ions and hydrogen gas at the cathode, the current passes through a metal electrode, oxidizing the metal to its cation, simultaneously, the water is reduced to hydrogen gas and the hydroxyl ion (OH-), in this way electrocoagulation introduces metal cations in situ, using sacrificial anodes (typically iron or aluminum) that need to be periodically replaced; cations destabilize colloidal particles by neutralizing charges, in addition to producing complex species of monomeric and polymeric hydroxide as coagulants; These coagulants form amorphous metal hydroxide precipitates; its high adsorption properties confer a strong affinity for dispersed particles and dissolved contaminants; the pollutants can be separated from the aqueous phase by coagulation, the hydrogen bubbles in the cathode promote turbulence in the system and bind with the pollutants, reducing their relative specific weight, they improve the separation process by flotation ( Mollah, et al, 2001)
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