Evaluation with scanning electron microscopy of Cd, Cu, and Zn removal from aqueous solutions by ash from gasification of poultry feathers

This study investigated the adsorption of heavy metals (Cd, Cu, Zn) as single or mixed pollutants from aqueous solutions. Ash from gasification of poultry feathers was used as the adsorbent. Batch experiments were performed at an adsorbent dosage of 1g·L-1, an adsorption time of 2h and an agitation speed of 100 rpm. In each variant, the total concentration of individual metals or their mixture was assumed to be around 500mg·L-1. The morphology and composition of ash before and after adsorption were characterized with X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The ash was rich in Ca, P and Si. Diffraction revealed the presence of calcium carbonate, calcium phosphate and calcium phosphate hydroxide. Microscopy confirmed the presence of Cd, Cu, and Zn on the ash surface after adsorption. Adsorption efficiency was higher for single metals than for their mixture. Spectroscopy revealed changes in ash composition that could be related to the mechanism of metal adsorption. Taking into account the high initial concentrations of metals, ash from poultry feathers is an attractive option for metal removal from wastewater.