Removal of vegetable tannins to recover water in the leather industry by ultrafiltration polymeric membranes

Abstract

The leather tanning industry consumes large amounts of water and produces, consequently, significant volumes of wastewater with high concentration of chemicals and organic matter. One of the main chemicals present in effluents is the vegetable tannin, which causes a severe environmental impact. With the aim of predicting the performance in chemicals separation of two ultrafiltration (UF) polymeric membranes (OT050 and GR60PP) for potential use in the purification of the waste stream of vegetable tanning liquors, a synthetic wastewater was prepared. Trials were carried out at laboratory scale using a flat cell with an effective area of 0.004m2. The effect of transmembrane pressure in the permeate flux was studied. Flux decline, fouling resistance and fouling index of the membranes were analyzed. The efficiency of different membranes was assessed using the rejection coefficient for tannins, non-tannins and total solids. Analysis of the wastewater treated by UF showed 83% of tannin retention and a recovery of the water flux after cleaning the membrane GR60PP with water of 41-45%. The rejection coefficient observed for the GR60PP membrane was higher than for the OT050. There are no previous studies related to the removal of vegetable tannins in exhausted vegetable tanning bath by using UF polymeric membranes. This study sets a precedent because the results obtained are very promising regarding permeate flux and rejection observed.