Optimization of Chromium Removal from Tannery Effluents with Natural Zeolite Neonite

Chromium is the main constituent of the tanning salts used by tanneries for processing skins into leather, and considered as a pollutant in the effluents that this industry discharge. The present study aimed to evaluate the removal of chromium and other pollutants in effluents from the tanning industry applying the natural zeolite Neonite. Neonite is a commercially available zeolite, that was acquired from NEONITE S.A. Neonite was characterized through FTIR and XRD, identifying clinoptilolite as its main component. Treatment was applied to samples of real effluents from the tanning stage or chromium bath (CB) and a composite effluent (CE), an experimental design was carried out for each effluent. The designs correspond to 32 factorial designs, variables tested were the Neonite dosage (NE) measured in g/L, stirring time (StT) expressed in minutes and the pH of the sample, and the response variable was the Residual Chromium Content (RCC). Statistical analysis was performed through R-software version 4.2.3 and included Box-Cox transformation and ANOVA to determine the main effects and the behavior of the response variable in relation to the applied model and its optimization by response surface. In CB, a removal above 95 % was obtained for RCC, with optimization values at 32 g/L of NE and pH 7. In the CE, a removal of more than 98 % was obtained for RCC and values higher than 60 % for BOD, COD, TSS and Fats, being the optimal conditions 4.73 g/L of NE and 12.17 minutes of StT. These results demonstrate that the application of Neonite for the removal of chromium and other pollutants from tanning industry effluents has a great potential.