TY - JOUR
T1 - Surface grafting with diverse charged chemical groups mitigates calcium phosphate scaling on reverse osmosis membranes during municipal wastewater desalination
AU - Rathinam, Karthik
AU - Modi, Akshay
AU - Schwahn, Dietmar
AU - Oren, Yoram
AU - Kasher, Roni
N1 - Funding Information:
The extent of calcium phosphate scaling on the different membranes was determined by monitoring the decrease in water flux following introduction of the SSE solution. The flux normalized to the initial flux, J/J0, is shown in Fig. 6A as a function of filtration time. Fig. 6B shows the percent decrease in average flux for each membrane after 40 h. The pristine membranes showed a decrease of 59.1% ± 7.4%, which was significantly higher than that of the grafted membranes, suggesting that graft polymerization by all methacrylate monomers effectively inhibited calcium phosphate scaling. The p(HEMA) (25.6% ± 2.3%) and p(SPM-co-MOETMA) (27.6% ± 6.7%) modified membranes showed the lowest decrease in flux and thus the best antiscaling performance. Grafting with MOETMA (44.1% ± 6.9%) and with MA (40.8% ± 2.9%) gave lower antiscaling performance, but the membranes still outperformed the pristine membrane. The results of the RO filtration experiments and the membranes’ scaling tendencies were supported by SEM analyses after scaling (Fig. S1, Supplementary Information). Particles and crystals were observed on the surfaces and were most prevalent on the pristine membrane, which was entirely covered by a layer of particles. The HEMA grafted membrane had fewest surface particles, in agreement with the scaling experiments (Fig. 6) showing it to exhibit the lowest decrease in flux.The authors acknowledge the Israel Science Foundation, Israel (ISF; grant No. 3237/19) for financial support. K.R. and A.M. thank the Jacob Blaustein Center for Scientific Cooperation (Ben Gurion University of the Negev, Israel) for a postdoctoral fellowship.
Funding Information:
The authors acknowledge the Israel Science Foundation , Israel (ISF; grant No. 3237/19 ) for financial support. K.R. and A.M. thank the Jacob Blaustein Center for Scientific Cooperation (Ben Gurion University of the Negev, Israel) for a postdoctoral fellowship.
Publisher Copyright:
© 2022
PY - 2022/4/5
Y1 - 2022/4/5
N2 - Calcium phosphate scaling on reverse osmosis (RO) membranes during the desalination of municipal wastewater remains a major problem. This study modified RO membranes by graft polymerization using hydrophilic methacrylate monomers to reduce scaling and investigated the effects of surface charge and exposed functional groups on scaling during municipal wastewater desalination. Grafting was performed using negatively charged, neutral, positively charged, and mixed charge monomers. Testing the modified membranes during RO desalination of a solution simulating treated domestic wastewater effluents from the Shafdan wastewater reclamation plant in Israel revealed improved antiscaling performance by grafted membranes compared with the pristine (unmodified) membrane. In particular, membranes grafted using neutral and mixed charge monomers showed the best antiscaling tendencies: 25.6% and 27.6% decrease in flux, respectively, compared with a 59.1% decrease using the pristine membrane. These results, together with physico-chemical characterization, suggested that calcium phosphate precipitation and scaling on the grafted RO membranes are driven mainly by electrostatic and dipole–dipole interactions between charged chemical groups exposed on the membrane surface and ionic species in the test solution; these interactions are minimized in membranes grafted with neutral or mixed charge poly (methacrylate) groups, resulting in enhanced antiscaling performance. This study provides insight into the antiscaling mechanisms of hydrophilic poly (methacrylate) chains grafted on RO membranes, and thus can potentially aid efforts to mitigate calcium phosphate scaling during RO desalination of municipal wastewater.
AB - Calcium phosphate scaling on reverse osmosis (RO) membranes during the desalination of municipal wastewater remains a major problem. This study modified RO membranes by graft polymerization using hydrophilic methacrylate monomers to reduce scaling and investigated the effects of surface charge and exposed functional groups on scaling during municipal wastewater desalination. Grafting was performed using negatively charged, neutral, positively charged, and mixed charge monomers. Testing the modified membranes during RO desalination of a solution simulating treated domestic wastewater effluents from the Shafdan wastewater reclamation plant in Israel revealed improved antiscaling performance by grafted membranes compared with the pristine (unmodified) membrane. In particular, membranes grafted using neutral and mixed charge monomers showed the best antiscaling tendencies: 25.6% and 27.6% decrease in flux, respectively, compared with a 59.1% decrease using the pristine membrane. These results, together with physico-chemical characterization, suggested that calcium phosphate precipitation and scaling on the grafted RO membranes are driven mainly by electrostatic and dipole–dipole interactions between charged chemical groups exposed on the membrane surface and ionic species in the test solution; these interactions are minimized in membranes grafted with neutral or mixed charge poly (methacrylate) groups, resulting in enhanced antiscaling performance. This study provides insight into the antiscaling mechanisms of hydrophilic poly (methacrylate) chains grafted on RO membranes, and thus can potentially aid efforts to mitigate calcium phosphate scaling during RO desalination of municipal wastewater.
KW - Antiscaling
KW - Calcium phosphate scaling
KW - Graft polymerization
KW - Municipal wastewater
KW - Reverse osmosis membrane
UR - http://www.scopus.com/inward/record.url?scp=85123680809&partnerID=8YFLogxK
U2 - 10.1016/j.memsci.2022.120310
DO - 10.1016/j.memsci.2022.120310
M3 - Article
AN - SCOPUS:85123680809
SN - 0376-7388
VL - 647
JO - Journal of Membrane Science
JF - Journal of Membrane Science
M1 - 120310
ER -