Characterisation of a nanoporous polymers for water treatment

Abstract

Materials which have structural dimensions between 1 nm and 100 nm are called nanomaterials. These materials have unique geometric, physicochemical and mechanical properties. As a result of their properties, nanomaterials can be tailored for specific applications. Polymers Synthesized from High Internal Phase Emulsions (PolyHIPEs) are a type of porous material with high specific surface area due to their nanoscale structure which have the ability to function as ion exchange media that can remove contaminants from water. PolyHIPEs can therefore be used in ion exchange modules to remove metals from wastewater. The advantage of using PolyHIPEs is that fewer steps are necessary compared with traditional filtration methods, and they are more economic and more selective than the traditional materials. A high internal-phase emulsion (HIPE) contains both oil and aqueous or dispersed phases. The oil phase has monomers such as styrene, a cross-linker such as Divinylbenzene (DVB), and non-ionic surfactants while the aqueous phase consists of deionized water and polymerisation initiators such as potassium pyrosulphate. The emulsion is subjected to the polymerization process, usually at 60˚C and pores are produced within the polymer due to the presence of the aqueous phase. The polyHIPE is then washed with propanol to release the residual surfactant and unreacted monomer. In this work, we used different HIPE mixing times (10, 15, 20, 25, and 30 minutes, respectively) in order to change the pore size distribution. After synthesis the PolyHIPEs are subjected to a sulphonation process which changes the PolyHIPE character from hydrophobic to hydrophilic. Finally, ion exchange experiments have been conducted by using sulphonated PolyHIPE beads as is and coated with iron oxide. As simulated contaminated water nickel and copper solutions were used during this process. The results show the removal efficiency of the metal ion from solution was much higher with sulphonated beads at range of pH (6, 7, 8 and 9). Changing the pH allowed the metals to be removed from the PolyHIPE for recovery and filter regeneration but the amount of metals after the regeneration process is low compared with initial concentration.