Enhancing mechanical properties of polyvinyl alcohol/sodium alginate gel beads by graphene oxide for the aerobic sludge immobilization in wastewater treatment

Abstract

This study reinforced polyvinyl alcohol/sodium alginate (PVA/SA) gel beads immobilizing aerobic sludge with graphene oxide (GO) as a nanofiller. The different types of beads were made by various concentrations of GO (0.02, 0.2, 2, 20, and 200 mg/L). The effect of GO on beads structure was observed by comparing the mechanical properties of chemical oxygen demand (COD) and NH₄⁺-N removal efficiencies. The results showed that the PVA/SA/GO gel carriers have excellent reinforcement properties compared to non-GO gel carriers, while sphericity factor and methylene blue absorption are the same. The strongest carrier contains 200 mg/L GO, referred to as GO6. In addition, the highest COD and NH₄⁺-N removal efficiencies of GO6 gel carriers were 97 and 96.67%, respectively, which is higher than a non-GO PVA/SA (GO1) gel carrier. The addition of GO (200 mg/L) was thus an effective way to improve the mechanical strength of PVA/SA gel beads due to the strong interaction between GO and the PVA/SA matrix. It can also promote COD and NH₄⁺-N removal efficiency of immobilized bacteria inside the beads.