Synthesis, characterization, and performance analysis of carbon molecular sieve-embedded polyethersulfone mixed-matrix membranes for the removal of dissolved ions

The asymmetric polyethersulfone (PES-15 wt.%) mixed-matrix membranes were prepared by incorporation of carbon molecular sieve (CMS) with varying concentrations (1, 3, and 5 wt.%). Physicochemical characterization of synthesized membranes was carried out using field emission scanning electron microscope, atomic force microscopy, contact angle, thermogravimetric analysis, zeta potential analyzer, porosity, and mean pore sizes. Performance analysis of synthesized mixed-matrix membranes was carried out by varying the operating parameters such as pressure (2-10 bar), feed concentration (100-1,000 mg/L), and cations type (Na⁺ , Ca²⁺ , Mg²⁺ , and Sn²⁺ ). Effect of operating parameters and CMS concentration was investigated on pure water flux (PWF), permeate flux, and rejection of membranes. It was found that mixed-matrix membrane containing 15 wt.% PES with 1 wt.% CMS displayed the superior physicochemical characteristics in terms of hydrophilicity (37.9°), surface charge (-13.8 mV), mean pore diameter (6.04 nm), and thermal properties (T_g  = 218.5°C), and overall performance. E5C1 membrane showed 1.5 times higher PWF (75.5 L m^-2  hr^-1 ) and incremented in rejection for all salts than the nascent membrane. PRACTITIONER POINTS: Carbon molecular sieve-embedded mixed-matrix membranes were synthesized by phase inversion method. The resultant membranes experienced improved hydrophilicity, roughness, surface charge, porosity, and mean pore diameter with 1 wt.% CMS loading. The pure water flux was improved from 55.77 to 75.05 L m^-2  hr^-1 when 1 wt.% CMS was added in pure PES. The observed rejection of a mixed-matrix membrane with 1 wt.% CMS was the maximum for all salts.

Efficient sampling in 3-D stereologic volumetry

Present 3-D stereology techniques use fixed grid sampling where the sampling grid of test points is randomly placed in 3-D. In order to increase randomness of sampling, in this paper we propose random grid sampling scheme where grid sections are placed randomly over 2-D cross-sections. A random grid sampler has superior efficiency and accuracy compared with fixed grid sampling. Using MR head scans we demonstrate the use of random grid sampling in volumetry of structures in 3-D biomedical images.