The pretreatment for the removal of small molecules from poly(acrylic acid) sodium (PAAS) solution by continuous diafiltration was investigated using ultrafiltration membrane. The effects of PAAS concentration, pH, tr...The pretreatment for the removal of small molecules from poly(acrylic acid) sodium (PAAS) solution by continuous diafiltration was investigated using ultrafiltration membrane. The effects of PAAS concentration, pH, trans-membrane pressure and pretreatment time on the permeate concentration and permeate flux were studied. The results show that the necessary pretreatment time (NPT) increases with PAAS concentration, decreases with TMP. The change trend of permeate flux with time is affected by pH. The permeate fluxes rapidly decrease from the start, and then increase gradually to stable values at pH 5.0, pH 7.0 and pH 9.3. However, it decreases gradually with time till a state value at pH 3.0 (iso-electric point, IEP). The removal of small molecules is easy at pH greater than iso-electric point (IEP). The change of filtration potential with time indicates the similar trend to that of permeation concentration, but the former is more convenient for indication of NPT.展开更多
The extraction of cobalt ions from dilute aqueous solutions was investigated by ultrafiltration with the help of poly(acrylic acid)sodium salt(PAASS).Polysulfone and polyethersulfone hollow fiber ultrafiltration membr...The extraction of cobalt ions from dilute aqueous solutions was investigated by ultrafiltration with the help of poly(acrylic acid)sodium salt(PAASS).Polysulfone and polyethersulfone hollow fiber ultrafiltration membranes were employed in this process.The kinetics of complexation reaction was studied for PAASS with Co^(2+).Results showed that,under a large excess of PAASS,it takes 65,55 and 40 min at pH 5,6 and 7,respectively,to get the equilibrium of complexation.The reaction kinetics can be described by a pseudo-first-order equation.Then,the effects of various parameters on the extraction of Co^(2+)were examined in detail.Results indicated that loading ratio,pH value and low-molecular competitive complexing agent affect significantly cobalt rejection coefficient R.Furthermore,a concentration experiment was carried out at pH 7.With increasing volume concentration factor,membrane flux declines slowly,and R value is always about 1.The concentrated retentate was used further for a decomplexation experiment.The decomplexation ratio of cobalt-PAASS complex reaches as high as 90.1%.After the decomplexation step,a diafiltration experiment was performed at pH 2.5.Cobalt ions can be extracted satisfactorily from the retentate,and a purified PAASS is obtained.展开更多
基金Projects(21176264,21476265)supported by the National Natural Science Foundation of China
文摘The pretreatment for the removal of small molecules from poly(acrylic acid) sodium (PAAS) solution by continuous diafiltration was investigated using ultrafiltration membrane. The effects of PAAS concentration, pH, trans-membrane pressure and pretreatment time on the permeate concentration and permeate flux were studied. The results show that the necessary pretreatment time (NPT) increases with PAAS concentration, decreases with TMP. The change trend of permeate flux with time is affected by pH. The permeate fluxes rapidly decrease from the start, and then increase gradually to stable values at pH 5.0, pH 7.0 and pH 9.3. However, it decreases gradually with time till a state value at pH 3.0 (iso-electric point, IEP). The removal of small molecules is easy at pH greater than iso-electric point (IEP). The change of filtration potential with time indicates the similar trend to that of permeation concentration, but the former is more convenient for indication of NPT.
基金supported by the National Natural Science Foundation of China(Grant No.20976040)the financial support from Project Supported by Science and Technology Planning Project of Hunan Province,China(No.2009SK3036).
文摘The extraction of cobalt ions from dilute aqueous solutions was investigated by ultrafiltration with the help of poly(acrylic acid)sodium salt(PAASS).Polysulfone and polyethersulfone hollow fiber ultrafiltration membranes were employed in this process.The kinetics of complexation reaction was studied for PAASS with Co^(2+).Results showed that,under a large excess of PAASS,it takes 65,55 and 40 min at pH 5,6 and 7,respectively,to get the equilibrium of complexation.The reaction kinetics can be described by a pseudo-first-order equation.Then,the effects of various parameters on the extraction of Co^(2+)were examined in detail.Results indicated that loading ratio,pH value and low-molecular competitive complexing agent affect significantly cobalt rejection coefficient R.Furthermore,a concentration experiment was carried out at pH 7.With increasing volume concentration factor,membrane flux declines slowly,and R value is always about 1.The concentrated retentate was used further for a decomplexation experiment.The decomplexation ratio of cobalt-PAASS complex reaches as high as 90.1%.After the decomplexation step,a diafiltration experiment was performed at pH 2.5.Cobalt ions can be extracted satisfactorily from the retentate,and a purified PAASS is obtained.
