Influence of contact time and pH on the removal of Fe (III) from acid mine drainage by adsorption with natural bentonite

Abstract

The main objective of the research was to remove iron ions from acid mine drainage, from the District of Ricrán, Province of Jauja, Junín region, controlling the pH and contact time, to later determine the adsorption model for this treatment. In the acid mine drainage, a sample was taken, which was analyzed by Atomic Absorption, in order to know the initial concentration of the metal, resulting in a concentration of 105.20 mg/l, this value exceeds the maximum permissible limits for the discharge of liquid effluents from metallurgical mining activities, where the annual average value is 1.6 mg/l and 2 mg/l for any sampling time. A mass curve was made, which gave knowledge about the appropriate dosage for adsorption, for this, different masses of natural bentonite were used, between 5 to 12.5 g, achieving equilibrium with 10 g of adsorbent. Controlling the pH and the contact time, the iron removal tests were performed. From 3 to 5 the pH was varied, and the contact time from 60 to 120 minutes. After the tests, the adequate contact time was 180 minutes at a pH of 5, with a removal percentage of 94.76 %. Experiments were carried out at different initial concentrations of iron ions, to find the model that determines the adsorption of iron with natural bentonite, which were between 20 to 100 mg/l. The model that best suited this treatment was the Freundlich isotherm, with R2 of 0.9533