Thin film composite membranes consisting of hyperbranched polyethyleimine (HPEI)-cysteamine layer for heavy metal removal

M.Sc. (Nanoscience)Abstract: Lack of clean water is one of the major challenges worldwide. This is due to prevalence of toxic pollutants disposed into our water systems, which includes both organic and inorganic pollutants. The sources of these pollutants are both industry and basic human activities. Heavy metals fall amongst major contaminants found in water, the toxicity and persistence of metals in the environment became well known in the 1970’s and unlike other pollutants, heavy metals cannot be degraded. Particularly cadmium (Cd2+) which has effects such as hypertension and kidney failure. Water treatment facilities in rural areas lack effective sufficient equipment for water purification. Thus it is very important to find new ways to efficiently remove these metals from water. Membrane technology amongst other water treatment methods has shown the ability to efficiently remove heavy metals. The thin film composite membranes were prepared via an interfacial polymerization between polyethersulfone (PES), hyperbranched-polyethylenimine (HPEI), trimesoyl chloride and cysteamine. The characterizations of membranes were carried out using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscope (SEM-EDX), atomic force microscope(AFM), contact angle, water intake capacity, batch adsorption, anodic stripping voltammetry (ASV) and inductive coupled plasma-optical emission spectroscopy (ICP-OES). FTIR spectra showed that there was a development of polyamide thin film on the surface of the membrane. The appearance of S-H peak in the FTIR and Raman spectrum further affirmed the functionalization of polyamide membrane layer with the cysteamine molecule. The modified membrane (PES/HPEI-SH) showed improved hydrophilicity as compared to the unmodified PES membrane. At constant transmembrane pressure of 900 kPa the flux of pristine PES, 8% PES/HPEI and PES/HPEI-SH was 191.10 L / h cm2, 10.27 L / h cm2, 10.9 L / h cm2 respectively. The batch experiments quantification analysis revealed that 22%, 53% and 99% Cd2+ removal for PES, PES/HPEI and PES/HPEI-SH respectively after 20 minutes..