Permeation characteristics of electrolytes and neutral solutes through titania nanofiltration membranes at high temperatures.
Nanoporous titania membranes with controlled pore sizes ranging from 0.7 to 2.5 nm, which had molecular weight cutoffs (MWCO) ranging from 500 to 2000, were successfully prepared by sol-gel processing, and the transport characteristics were evaluated across a temperature range of 30-80 degrees C. With increasing temperature, the permeate flux increased 2- to 3-fold, depending on the pore size. The water permeation mechanism was found to be different from viscous flow and was explained by the state of the water (free water/bound water/nonfreezing water) inside confined pores. The rejection of neutral solutes such as raffinose, the separation mechanism of which is molecular sieving (steric hindrance), decreased with temperature whereas that of electrolytes (MgCl(2) and NaCl), the separation mechanism of which is the charge effect (Donnan exclusion), was approximately constant. The temperature dependence of neutral and electrolyte solutes was analyzed using the Spiegler-Kedem equation by combining the Arrhenius equations for diffusivity and viscosity, which we obtained DeltaE(m), the activation energy of diffusion, after eliminating the effect of viscosity. For large DeltaE(m), which corresponds to the rejection of neutral solutes on the basis of molecular sieving, rejection decreased with temperature but remained unchanged for small DeltaE(m), which corresponds to the rejection of electrolytes based on the charge effect.
Rejection of small solutes by reverse osmosis membranes for water reuse applications: A pilot-scale study
Abstract N-nitrosamines and boron are small solutes of particular concern during water recycling applications. Here, we evaluated the rejection of seven N-nitrosamines and boron under a range of operating conditions and feed solution characteristics. The evaluation was conducted using a pilot-scale reverse osmosis (RO) system to appropriately simulate hydrodynamic conditions of full-scale RO installations. The rejection of seven N-nitrosamines by the pilot RO system varied significantly in the range from 31 to 94%, and rejection increased in the increasing order of their molecular weight. Rejection values obtained from this pilot-scale study were lower than those previously reported in laboratory-scale studies. These discrepancies were attributed to a difference in RO system operating condition (i.e. recovery) between the pilot-scale study (25%) and laboratory-scale study (
“Family” Support for Family Violence: Exploring Community Support Systems for Lesbian and Bisexual Women Who Have Experienced Abuse
ABSTRACT “Family” is a euphemistic term that lesbian, gay, bisexual, and transgender (LGBT) people use among ourselves to designate membership in lesbian, gay, bisexual, and transgender communities. Ironically, this “family” may be the most sought, yet least successful, support for dealing with the intimate partner violence that occurs within LGBT families. This study of 11 lesbian and bisexual women's experiences seeking support revealed several tiers of unmet needs within the LGBT community. They rarely used services in the general community, although these services are often the focus of both criticism and efforts to build support systems for LGBT victim/survivors. A model presents the different stages and potential sources of support.