Abstract

An industrial process for extracting arsenic from solutions through scorodite crystallization at 70 °C was designed and simulated using METSIM software. Using equilibrium information from the phase diagram of the system As(V)/Fe(III)/H2O at 50 and 70 °C, experimental tests were carried out of crystallization of scorodite at 50, 70, and 95 °C, as well as crystallization at 170 °C in an autoclave. This information provides the preliminary operational conditions for the process. The tests show that temperature influences the quality of crystals and the velocity of scorodite crystallization (residence time between 3 h and 3 days). The simulated process allows for the analysis of different evaporation ratios (42.5, 71.97, and 86.7%), determining the material and energy balances and the quality of the products and residues, thus providing important information for potential industrial applications. The energy requirements for each evaporation ratio are 21 568, 33 747, and 39 836 Mcal/h, and the sums of the total flows are 11 588.60, 8876.28, and 7520.11 tons/day, respectively. This last variable is related to the size of the equipment used in the process. Molar Fe/As ratios of 1, 0.9, and 0.8 result in yields of 93, 88, and 78%. © 2009 American Chemical Society.