Both reverse osmosis(RO) and nanofiltration(NF) membranes have been increasingly used for water purification and desalination. However, the salt rejection of NF membranes is quite different from that of RO membranes,w...Both reverse osmosis(RO) and nanofiltration(NF) membranes have been increasingly used for water purification and desalination. However, the salt rejection of NF membranes is quite different from that of RO membranes,which makes a significant distinction in their process designs. This work started from the performance investigation of a single NF membrane element and then focused on the process design of the NF system for surface water treatment. In experimental tests, it was found that the observed rejection of the NF element becomes nearly constant when the concentrate flow is large enough, while the membrane flux of the NF element is quite stable regardless of the water flow across the membrane surface. These findings can be used to instruct the process design of the NF system for surface water treatment. In process design, a two-stage arrangement is sufficient for the NF system to reach the highest water recovery, while the RO system requires a three-stage arrangement.展开更多
Investigation was made on the efficiency of two commercial membranes in removing via forward osmosis(FO)the low molecular weight organic compounds typical of coking wastewater. The membranes were supplied by Poten and...Investigation was made on the efficiency of two commercial membranes in removing via forward osmosis(FO)the low molecular weight organic compounds typical of coking wastewater. The membranes were supplied by Poten and HTI companies. The organics in the simulated coking water were indole and pyrridine. Under FO mode, the rejection to the organics by Poten membrane was around 50%, whereas that for HTI membrane was obviously higher, ranging from 65% to 74%. The response of the two membranes in terms of Water flux and reverse salt flux(RSF) towards changing feed/draw solution(DS) flow rates in FO mode showed similar tendency,but different degree. Generally, the flux in FO using HTI membranes was lower. For HTI membrane, FO operated with pressure retarded osmosis(PRO) mode was also performed and the overall rejection of the organics was slightly lower than that in FO mode. In the long term FO test within 15 days, both Poten and HTI membranes displayed flux reduction and rejection enhancement. But the variation with Poten membrane was much more obvious. Discussion was carried out about the reasons and the mechanisms behind the FO performance difference between two membranes and the variation in flux and rejection with operation conditions. Characterizations by SEM, FTIR, AFM, XRD and XPS were tried to support the proposed explanations.展开更多
A self-made PMIA asymmetric nanofiltration membrane was used for arsenic removal from drinking water by NF process. Effects of feed concentration, operating pressure, pH and existing ions on As(V) removal were investi...A self-made PMIA asymmetric nanofiltration membrane was used for arsenic removal from drinking water by NF process. Effects of feed concentration, operating pressure, pH and existing ions on As(V) removal were investigated. Experimental results showed that As(V) rejection was higher than 90% in the range of investigated As feed concentrations. The As(V) rejection increased slightly with pressure increase, As(V) rejection was higher than 90% in the pressure range of 0.4 MPa to 0.8 MPa. As(V) rejection increased significantly from 83% at pH 3 to 99% at pH 9. The presence of NaCl enhanced As(V) rejection in the range of feed concentration, and As(V) rejection can reach up to 99% at a feed As concentration of 100 μg/L, whereas there was a rejection decrease of 8% in the presence of Na2SO4 at every feed concentration. The results showed the As(V) detected in the permeate was lower than the EPA recommended MCL up to a feed As concentration of approximately 10 μg/L in the experimental research range.展开更多
基金Sponsored by the National Natural Science Foundation of China(51578485,L1422037)the National Basic Research Program of China(2015CB655303)+1 种基金the Research Fund for the Doctoral Program of Higher Education of China(No.20130101110064)the National Sustain Plan Program of China(2015BAB11B01)
文摘Both reverse osmosis(RO) and nanofiltration(NF) membranes have been increasingly used for water purification and desalination. However, the salt rejection of NF membranes is quite different from that of RO membranes,which makes a significant distinction in their process designs. This work started from the performance investigation of a single NF membrane element and then focused on the process design of the NF system for surface water treatment. In experimental tests, it was found that the observed rejection of the NF element becomes nearly constant when the concentrate flow is large enough, while the membrane flux of the NF element is quite stable regardless of the water flow across the membrane surface. These findings can be used to instruct the process design of the NF system for surface water treatment. In process design, a two-stage arrangement is sufficient for the NF system to reach the highest water recovery, while the RO system requires a three-stage arrangement.
基金National Natural Science Foundation of China(Project no.21176265)Hunan Provincial Science and Technology Plan(Project no.2014GK3106).
文摘Investigation was made on the efficiency of two commercial membranes in removing via forward osmosis(FO)the low molecular weight organic compounds typical of coking wastewater. The membranes were supplied by Poten and HTI companies. The organics in the simulated coking water were indole and pyrridine. Under FO mode, the rejection to the organics by Poten membrane was around 50%, whereas that for HTI membrane was obviously higher, ranging from 65% to 74%. The response of the two membranes in terms of Water flux and reverse salt flux(RSF) towards changing feed/draw solution(DS) flow rates in FO mode showed similar tendency,but different degree. Generally, the flux in FO using HTI membranes was lower. For HTI membrane, FO operated with pressure retarded osmosis(PRO) mode was also performed and the overall rejection of the organics was slightly lower than that in FO mode. In the long term FO test within 15 days, both Poten and HTI membranes displayed flux reduction and rejection enhancement. But the variation with Poten membrane was much more obvious. Discussion was carried out about the reasons and the mechanisms behind the FO performance difference between two membranes and the variation in flux and rejection with operation conditions. Characterizations by SEM, FTIR, AFM, XRD and XPS were tried to support the proposed explanations.
文摘A self-made PMIA asymmetric nanofiltration membrane was used for arsenic removal from drinking water by NF process. Effects of feed concentration, operating pressure, pH and existing ions on As(V) removal were investigated. Experimental results showed that As(V) rejection was higher than 90% in the range of investigated As feed concentrations. The As(V) rejection increased slightly with pressure increase, As(V) rejection was higher than 90% in the pressure range of 0.4 MPa to 0.8 MPa. As(V) rejection increased significantly from 83% at pH 3 to 99% at pH 9. The presence of NaCl enhanced As(V) rejection in the range of feed concentration, and As(V) rejection can reach up to 99% at a feed As concentration of 100 μg/L, whereas there was a rejection decrease of 8% in the presence of Na2SO4 at every feed concentration. The results showed the As(V) detected in the permeate was lower than the EPA recommended MCL up to a feed As concentration of approximately 10 μg/L in the experimental research range.
