Impacts of sodium bicarbonate and co-amine monomers on properties of thin-film composite membrane for water treatment

Polyamide (PA) thin-film composite (TFC) nanofiltration (NF) membranes are widely used for the treatment of water and wastewater treatment. However, the membrane surface properties could be further modified during interfacial polymerization (IP) process to achieve higher water flux and salt rejection. Herein, the effects of sodium bicarbonate (NaHCO3) and co-amine monomer—2-(2′aminoethoxy) ethylamine (AEE) on the characteristics of piperazine (PIP)-based TFC membranes were investigated for water purification and aerobically treated palm oil mill effluent (AT-POME) treatment. Characterizations based on field emission scanning electron microscopy (FESEM), Fourier transform infrared analysis (FTIR) and contact angle were carried out to provide support to the filtration results. Our findings showed that 0.5 wt% NaHCO3 was the best loading to be added to improve the membrane performance by enhancing water permeability by 37% without affecting Na2SO4 rejection. In the presence of 0.5 wt% NaHCO3, it is found that the introduction of AEE into PIP solution could further improve the Na2SO4 rejection of PIP-based membrane from 97.1 to 98.5% while producing a permeate of better quality. Further evaluation using AT-POME indicated that the AEE-modified membrane was able to enhance the separation performance of PIP-based membrane, increasing its conductivity, colour (ADMI) and COD reduction from 74.31, 92.79 and 83.4%, respectively, to 79.15, 94.26 and 89.3%. This work demonstrated the positive features of using inorganic additive and secondary amine monomer in improving characteristics of TFC membrane for water and wastewater treatment.