Poly(amidoamine) dendrimer (PAMAM) grafted on thin film composite (TFC) nanofiltration (NF) hollow fiber membranes for heavy metal removal

This study provides a facile and effective method to modify thin film composite (TFC) hollow fiber nanofiltration (NF) membranes by grafting poly (amidoamine) dendrimer (PAMAM) on the interfacially polymerized layer of polyethersulfone (PES) membranes for heavy metal removal. The PAMAM grafting not only decreases the pore size of the composite membrane, but also provides the positively charged functional groups, such as tertiary amino groups (RH₃N⁺ and R₃HN⁺), on the membrane surface to improve the hydrophilicity and water permeability of the TFC membrane without compromising rejection. The resultant membrane possesses rejection over 99% against most tested heavy metals like Pb²⁺, Cu²⁺, Ni²⁺, Cd²⁺, Zn²⁺ and As⁵⁺, with an outstanding pure water permeability (PWP) greater than 3.6Lm^-2h^-1bar^-1 at 10bar. The rejection of the membrane to As³⁺ is also impressive. It can reach 97% by changing the solution pH. Moreover, the membrane shows stable performance for at least 72h under continuous testing. This PAMAM grafted TFC membrane may have great potential for heavy metal removal and other water treatment applications.