Bio-Based Ceramic Membranes for Bacteria Removal from Water

Abstract

Bio-based ceramic membranes were elaborated from kaolinite clays, coconut husks and eggshells to retain E. coli bacteria present in water intended for human consumption. Their characterization and removal performances are investigated in this work. These bio-ceramic membranes were obtained by heating the formulation containing 75% clay, 15% coconut husk and 10% eggshell at 900 °C or 1000 °C, at different temperature rates, to give S1, S2 and S3 materials. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), mercury porosimetry and scanning electron microscopy (SEM) were used to characterize these membranes. Water flux density, bacterial removal and biofouling were also assessed. Water flux density was shown to depend on material porosity. Bacteria retention was 90% (with 1 log-removal) for S1, 80% (with 0.7 log-removal) for S2 and 100% (with 3.3 log-removal) for S3. Membranes S1 and S2 presented reversible biofouling, while no fouling was evidenced for S3 in the tested conditions. This work shows that the best bio-ceramic membrane in terms of bacterial removal and flux density was S3. Its water flux density was 2123 ± 72 L/h/m2 at an initial pressure of 0.2 bar. This material is particularly interesting because its production protocol is quite simple, fast and without the addition of chemical additives. Moreover, it can be used to efficiently remove bacteria from drinking water.

Cationic cellulose filter papers modified with ZnO/Ag/GO nanocomposite as point of use gravity-driven filters for bacterial removal from water

“…Dopamine, as a highly reactive molecule, can form a polycationic PDA layer on organic or inorganic surfaces, including cellulose filter papers, by self-polymerization. The optimum conditions for forming uniform PDA coatings on membranes, e.g., PD concentration and pH, have been the subject of several studies 36 , and the conditions in the present study have been chosen accordingly. In the dopamine-containing Tris buffer, dopamine molecules can react with the hydroxyl groups of cellulose papers via their catechol groups to form stable chemical bonds and subsequently a PDA stacking layer 37 .…”

“…Therefore, the increase in the positive surface charge of the filters after the formation of the PDA layer was small because PDA is amphoteric 40 . However, PDA, thanks to its abundant chemical reaction sites, can function as an intermediate layer to permit the filter to be more modified using other molecules 36 . Thus, PEI was used to form a layer with higher positive charge.…”

“…However, large-pore blockage has not happened, and the filters can still work under atmospheric pressure. Pore blockage and the subsequent significant flux decline after PDA grafting on UF or NF membranes are very probable 36 . For 3 sheets of PDA/PEI modified papers, the flow rate was 1.7 mL min -1 .…”