Synthesis and modification of nanofiltration membranes with dendrimer-modified graphene oxide to remove lead and cadmium ions from aqueous solutions

This study explored the use of graphene oxide modified with dendrimer (GO/MDA) to enhance the hydrophilicity and reduce the clogging of nanofiltration membranes, aiming to remove lead and cadmium from aqueous solutions. The synthesis involved multiple steps for creating graphene oxide (GO) nanoparticles and dendrimer (MDA), with FT-IR and EDX tests confirming the successful fabrication of GO/MDA and its application in nanofiltration membranes. Four types of membranes were designated based on the concentration of GO/MDA used: nanofiltration without nanoparticles (NF), nanofiltration with 0.25% weight of nanoparticles (NF-0.25), nanofiltration with 0.5% weight of nanoparticles (NF-0.5), and nanofiltration with 1% weight of nanoparticles (NF-1). The results showed a significant decrease in contact angle from 68.2° to 51.6° with the increase of GO/MDA concentration from 0.25% to 1%, illustrating improved hydrophilicity. Moreover, the pure water flow rate increased, with the NF-1 membrane achieving the highest flow rate of 121 L/m².h, compared to 86 L/m².h for the standard NF membrane. The study also established that the removal efficiencies for lead and cadmium improved with rising pH levels, peaking at pH 6, where the NF-0.5 membrane achieved optimal removal rates of 89.45% for Pb²⁺ and 92.58% for Cd²⁺. Additionally, the incorporation of GO/MDA nanoparticles effectively reduced irreversible fouling, with the NF-0.5 membrane displaying a remarkable flux recovery percentage of 97.21%. Overall, the findings confirm that the incorporation of GO/MDA nanoparticles successfully enhanced the performance of nanofiltration membranes in removing heavy metals.