OPCIONES PARA EL TRATAMIENTO Y LA DISPOSICIÓN DE LOS LICORES ÁCIDOS AGOTADOS PROVENIENTES DEL DECAPADO DE HIERRO

The iron finishing industry in Mexico, employs sulfuric acid as a pickling agent to clean materials from scale, rust and dirt. Generaliy the industries do not treat or recycle the spent pickle liquors, and in most of the cases these acids are discharged directly to the drainage system acidifying the water streams. Alternatives of solution for this poliution problem were reviewed in the context of the Mexican industry, and a particular case was studied through the characterization of its spent pickle liquors. Proposed altematives are: neutralization, recycling and reuse (as reducing agent or saline-sodic soil reclamation agent) with no prior treatment of'the spent liquors. Recycling, either with H 2 SO 4 or HC1, is considered as the optimal solution. Analysis of the spent pickle liquors of the case study indicate an acid concentration of 5.7% w/v* and an FeSO 4 •7H 2 O concentration of 27% w/v, with coefficiients of variation of 15 and 8% respectively. These contents are in the low range of those found for similar industries in developed countries. Other metals are present in the mg/L level: Mn, Na, Zn, Ca, K, Pb, Al, Cr, Ni and Mg. These metals should be considered as posible impurities in the end-products of the different proceses proposed.