Penapisan membran untuk penyingkiran asid humik merupakan cabaran dari segi penyumbatan membran yang berlaku melalui penyumbatan zarah asid humik dan bakteria yang terdapat dalam aliran suapan pada membran. Membran berpengisi tunggal mengalami masalah untuk mencapai sifat antisumbat dan antibakteria pada masa yang sama. Oleh itu, membran polietersulfona (PES) dwi pengisi dihasilkan melalui proses pemisahan fasa dengan mencampurkan zarah nano zink oksida (ZnO) dan tiub karbon nano dinding berlapis (MWCNT) pada pelbagai nisbah ke dalam larutan dop PES. Sebelum dicampurkan, MWCNT difungsikan (FCNT) dengan mengunakan asid nitric bagi menghasilkan kumpulan berfungsi hidrofilik hidroksil dan karboksilik pada permukan tiub. Oleh itu, kedua-dua pengisi nano tersebut digunakan untuk menghasilkan membran bersifat antisumbat dan antibakteria yang baik. Kesan sinergi kedua-dua pengisi nano akan dicirikan dari segi kelikatan larutan dop, morfologi, kekasaran permukaan, size liang membran dan keliangan membran, kehidrofilikan, kestabilan haba serta prestasi penapisan. Dapatan penyelidikan menunjukkan bahawa membran yang mengandungi dwi pengisi adalah lebih berliang berbanding dengan membran berpengisi tunggal dan membran PES yang tidak berpengisi. Di samping itu, peningkatan nisbah FCNT telah menyebabkan peningkatan kehidrofilikan membran. Penambahan kedua-dua pengisi nano didapati meningkatkan kelikatan larutan dop dan mengurangkan kekasaran permukaan membran. Fluks resapan meningkat dengan peningkatan nisbah FCNT. Apabila pengisi nano pada membran didominasi oleh FCNT (nisbah melebihi 0.5), penolakan asid humik (HA) tidak terjejas walaupun keluasan liang membran meningkat. Dapatan juga menunjukkan bahawa tanpa tindakbalas fotobermangkin, fungsi antibakteria disumbangkan oleh ZnO adalah dengan fungi antirekatan dan bukannya perencetan bakteria. Dari semua membran yang dihasilkan, FZ3 dengan nisbah FCNT dan ZnO yang sama dapat mencapai prestasi optima dengan fluks air tulen sebanyak 89.66 L/m2.h dan penolakan HA sebanyak 93.21%. Berpandukan pada perintang kotoran dan kurang pelekatan bakteria pada permukaan membran, FZ3 merupakan membran dwi pengisi bersifat antisumbat dan antibakteria yang terbaik. _______________________________________________________________________
Membrane filtration for humic acid removal faced challenges in term of fouling caused by solute itself and the bacteria found in the feed stream. There were a lot of studies showed great antifouling and antibacterial properties at the same time. Hence, dual nanofiller polyethersulfone (PES) membrane was synthesized via phase inversion method by blending different ratio zinc oxide (ZnO) and multiwalled carbon nanotube (MWCNT) into PES dope solution. Prior blending, MWCNT was functionalized using nitric acid to form hydrophilic hydroxyl and carboxylic group on the tube surface for dispersion. The combination of both MWCNT and ZnO was able to produce combined effect improved antifouling and antibacterial synergistic effect that does not require additional reaction or interaction between them. The synergistic effect of both nanofiller on the membrane properties was characterized in term of dope solution viscosity, morphology, surface roughness, membrane pore size and porosity, hydrophilicity, thermal stability and filtration performance. The results reveal that the membrane containing dual nanofiller was porous compared to single filler membrane and neat PES membrane. Furthermore, the increase of FCNT ratio caused the membrane hydrophilicity increased. The addition of both nanofiller was found to increase the dope solution viscosity and reduced the surface roughness of the membrane. As FCNT ratio in the membrane increased, higher permeate flux was recorded. When the nanofiller of the membrane was dominated by FCNT (i.e., ratio more than 0.5), the humic acid (HA) rejection was not affected much even though pore size of the membrane was increased. It was also been found that without photocatalytic reaction, the antibacterial properties contributed by ZnO was antiadhesion effect rather than inhibition of the bacteria. Out of all the fabricated membranes, FZ3 (dual nanofiller membrane produced with 1wt% of equal ratio functionalized MWCNT and ZnO mixture) was able to achieve optimum performance with pure water flux of 89.66 L/m2.h and HA rejection of 93.21%. Judging from its lower fouling resistance and less bacterial adhesion onto the membrane surface, FZ3 was the most antifouling and antibacterial dual nanofiller membrane.
Impregnation of mwcntzno dual nanofiller mixed matrix membrane_Pang Wen Yu_K4_2020_MYMY