Usability of modified end-of-life membranes for purification of waters from pulp and paper mills
Jalilian, Yasaman (2023)
Diplomityö
2023
School of Engineering Science, Kemiantekniikka
Kaikki oikeudet pidätetään.
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe2023062057026
https://urn.fi/URN:NBN:fi-fe2023062057026
Tiivistelmä
Nowadays, the global disposal of reverse osmosis membranes (RO) modules is occurring at an alarming rate, and the negative effects are intensifying. This prospective study was designed to investigate the technical feasibility of recycling end-of-life (EoL) RO membranes and their reuse as ultrafiltration (UF) and nanofiltration (NF) membranes as a new platform in the pulp and paper industry.
This thesis intends to determine the extent to which the polyamide (PA) layer of EoL membrane can be chemically oxidized via sodium hypochlorite (NaOCl) facilitated by chloride (CaCl2) as accelerating catalyst in terms of application, recycled membranes can be effectively utilized for purifying the alkaline filtrate from the pulp mill. Moreover, this study seeks to explore the influence of post-modification of oxidized membranes via layer-by-layer (LbL) polyelectrolyte deposition technique in filtration performance of oxidized membranes. Herein, two strong, pH-independent polyelectrolytes Poly(diallyldimethylammonium chloride) (PDADMAC) and poly(polystyrenesulfonic acid) (PSS) were utilized as polycation and polyanion during the self-assembly of polyelectrolyte multilayers (MPLs). The effectiveness of different oxidation levels of PA layer and further MPLs post-modification technique were evaluated in terms of pure water permeability (PWP), MgSO4 salt rejection, and total dissolved carbon (TDC) removal and conductivity rejection of alkaline filtrate as pulp and paper mills effluent before and after each step of modification. This study has identified the possibility of systematically controlling the chemical oxidation level of the polyamide (PA) layer to produce UF/NF membranes with various molecular weight cut-offs (MWCO). One of the more significant findings to emerge from this study is that with higher degradation of PA layer and further MPLs post-modification, a NF membrane with higher PWP and similar MWCO can be achieved, compared to less oxidized one at the same polyelectrolyte bilayers modification.
Taken together, the findings from this study can be employed as a reasonable approach to address the environmental impacts of EoL membranes and take the relevant economical advantages of recycled membranes in various applications, such as purification of effluents from pulp and paper mills.
This thesis intends to determine the extent to which the polyamide (PA) layer of EoL membrane can be chemically oxidized via sodium hypochlorite (NaOCl) facilitated by chloride (CaCl2) as accelerating catalyst in terms of application, recycled membranes can be effectively utilized for purifying the alkaline filtrate from the pulp mill. Moreover, this study seeks to explore the influence of post-modification of oxidized membranes via layer-by-layer (LbL) polyelectrolyte deposition technique in filtration performance of oxidized membranes. Herein, two strong, pH-independent polyelectrolytes Poly(diallyldimethylammonium chloride) (PDADMAC) and poly(polystyrenesulfonic acid) (PSS) were utilized as polycation and polyanion during the self-assembly of polyelectrolyte multilayers (MPLs). The effectiveness of different oxidation levels of PA layer and further MPLs post-modification technique were evaluated in terms of pure water permeability (PWP), MgSO4 salt rejection, and total dissolved carbon (TDC) removal and conductivity rejection of alkaline filtrate as pulp and paper mills effluent before and after each step of modification. This study has identified the possibility of systematically controlling the chemical oxidation level of the polyamide (PA) layer to produce UF/NF membranes with various molecular weight cut-offs (MWCO). One of the more significant findings to emerge from this study is that with higher degradation of PA layer and further MPLs post-modification, a NF membrane with higher PWP and similar MWCO can be achieved, compared to less oxidized one at the same polyelectrolyte bilayers modification.
Taken together, the findings from this study can be employed as a reasonable approach to address the environmental impacts of EoL membranes and take the relevant economical advantages of recycled membranes in various applications, such as purification of effluents from pulp and paper mills.