Tetyana M. Kuznicki

Natural clinoptilolite composite membranes on tubular stainless steel supports for water softening.

Disk membranes generated from high-purity natural clinoptilolite mineral rock have shown promising water desalination and de-oiling performance. In order to scale up production of these types of membranes for industrial wastewater treatment applications, a coating strategy was devised. A composite mixture of natural clinoptilolite from St. Cloud (Winston, NM, USA) and aluminum phosphate was deposited on the inner surface of porous stainless steel tubes by the slip casting technique. The commercial porous stainless steel tubes were pre-coated with a TiO2 layer of about 10 μm. Phase composition and morphology of the coating materials were investigated using X-ray diffraction and scanning electron microscopy. Water softening performance of the fabricated membranes was evaluated using Edmonton (Alberta, Canada) municipal tap water as feed source. Preliminary experimental results show a high water flux of 7.7 kg/(m(2) h) and 75% reduction of hardness and conductivity in a once-through membrane process at 95 °C and feed pressure of 780 kPa. These results show that natural zeolite coated, stainless steel tubular membranes have high potential for large-scale purification of oil sands steam-assisted gravity drainage water at high temperature and pressure requirements.

Separation of Argon and Oxygen by Adsorption on a Titanosilicate Molecular Sieve

Abstract A titanosilicate molecular sieve adsorbent, Ba-RPZ-3, was synthesized and tested for its use in the separation of O2+Ar mixtures at room temperature. A clean resolution of both gases was achieved in pulse chromatographic experiments using a standard column (0.25″ OD, 3.5 grams of adsorbent). In another experiment, using a column containing 30 grams of adsorbent and a continuous O2+Ar feed at 10 cm3/min, argon breakthrough was detected more than 5 minutes before the oxygen breakthrough, and the separation was sufficiently sensitive to achieve quantitative separation of mixtures with low argon content (5% Ar). Equilibrium adsorption isotherms and isosteric heats of adsorption for oxygen and argon were found to be almost identical at room temperature. The thermodynamic selectivity was found to be mildly in favor of oxygen (∼1.1–1.2). However, the adsorption of oxygen was observed to be much faster than argon, indicating that the separation of the O2+Ar mixtures was based on the sieving properties of the adsorbent and the difference in sizes of O2 molecules and Ar atoms. This indicates that a suitably-oriented oxygen is physically smaller than argon, despite the fact that many references assume that oxygen is larger than argon.