Conversion of Untanned Proteinaceous Solid Wastes from Tanneries into Aerogel and Its Application in Batch and Continuous Fixed-Bed Adsorption of Acid Red 97

Abstract

Gelatin-based aerogel (G-Aerogel) from untanned proteinaceous solid wastes was applied as an adsorbent in batch and fixed-bed column systems to remove acid red 97 (AR97) from water. Adsorption was evaluated as a function of pH, adsorbent mass, contact time, temperature, and initial dye concentration. Maximum removal of AR97 was achieved at pH 3 after about 4 h. The pseudo-second-order equation provided the best adsorption kinetic model. The adsorption of AR97 onto G-Aerogel was best described with the Langmuir model, and the maximum adsorption capacity was about 196 mg·g−1. A thermodynamic study showed an exothermic and spontaneous adsorption process. It was also demonstrated that G-Aerogel can be reused several times. The column study showed that breakthrough and saturation times decreased with increasing initial AR97 concentration. Thomas and Yoon-Nelson kinetic models were applied to the experimental data to predict the breakthrough curves and determine the characteristic parameters of column adsorption. Tannery solid wastes composed mainly of collagen are very abundant and constitute a material that should be valorized. In this study, we examined the transformation of untanned proteinaceous wastes into a biomaterial [Gelatin-based aerogel (G-Aerogel)] of environmental interest. The results demonstrated the promise of this material for dye adsorption because of its advantages in terms of its ease of preparation, its containing functional groups that are able to attract dye, its ability to be reused several cycles, and its high adsorption capacity. In addition to studying adsorption in static mode, we also studied dynamic adsorption, because the common industrial practice is to pass water to be treated through a column packed with an adsorbent, allowing the transport of the pollutant from the liquid to the solid. In summary, G-Aerogel can be applied as an environmentally friendly and efficient adsorbent for the removal of dyes from contaminated water.