Assessment of Cyprinus carpio Scales as a Low-Cost and Effective Biosorbent for the Removal of Heavy Metals from the Acidic Mine Drainage Generated at Rosia Montana Gold Mine (Romania)

Abstract

In the present study, the biosorptive potential of Cyprinus carpio scales for the removal of Fe, Mn, and Zn ions from real acidic mine drainage (AMD) generated at the Rosia Montana gold mine (Romania) was explored for the first time. The collected AMD solution is very acidic, and the concentrations of Fe, Mn, and Zn ions exceed more than 34 to 56 times the disposal standards imposed by legislation. Batch adsorption experiments were carried out to study the effect of the sorbent dosage, sorbent particle size, pH, and contact time on the adsorption performance of the fish scales. Before and after the adsorption process, the biosorbent was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, and energy-dispersive X-ray spectroscopy (SEM-EDX). In the investigated experimental conditions, about 100%, 87.1%, and 100% of Fe, Mn, and Zn ions were removed from the AMD after 240 min of contact with the finest-grained Cyprinus carpio scale samples using a solid:liquid ratio of 20:1 (g:L). The adsorption data were analyzed using the pseudo-first order, pseudo-second order, intraparticle diffusion rate, and Elovich equations. The adsorption process was found to follow the pseudo-second-order kinetic model. The maximum adsorption capacities of the fish scales were about 2.46 mg/g for Mn and 0.85 mg/g for Zn ions, respectively. Aside from their significant efficiency in the removal of metals from AMD, Cyprinus carpio scales also have the potential to neutralize the acidic wastewater. Thus, the removal process of metal ions from AMD is ruled by a complex mechanism, including adsorption and iron precipitation. The recycled scales are still able to remove the metal ions from AMD with a better performance during the first regeneration cycle. Based on the obtained results, it might be assessed that the low-cost biowaste of Cyprinus carpio scales have great potential and could be effectively used for the remediation of real acidic mine drainage from a sustainable perspective.