SCHOOL OF MECHANICAL ENGINEERING SEMINAR Monday, March 26, 2012 at 15:00 Wolfson Building of Mechanical Engineering, Room 206

M.Sc. student of Dr. Hadas Mamane Steindel, School of Mechanical Engineering, Tel-Aviv University

The global shortfall in availability of potable water, escalates the need for treatment technologies that produce high quality water that do not cause detrimental effects to human beings or the environment. Novel treatment methods based on nanotechnology have very promising potential to provide drinking water from previously unusable water sources. This research is a part of an international collaborative project titled: Nano-structured TiON photo-catalytic membranes for water treatment (NATIOMEM). The project main purpose is the development of an efficient thin film N-doped titanium (TiO2) coatings for mineralization of micro-pollutants by UV-visible light activation and eventually, using the best technology to incorporate these into a novel nanostructured photocatalytic membrane for water treatment systems. Photocatalytic experiments on the chosen pharmaceutical pollutant Carbamazepine (CBZ) were conducted using N-doped TiO2 coated glass slides under a solar simulator. Out of various methods examined, the most efficient deposition technique was found to be the "sol-gel" (solid phase formed through gelation of a colloidal suspension (sol)) deposited substrates. Photocatalytic efficiency were tested on samples annealed at different environments (air, N2 and ammonia) and it was determined that annealing in air and N2 prevails ammonia even though the nitrogen concentration was higher (4 times), probably due substitutional N-doping as opposed to interstitial. No sorption of the catalyst to variously charged molecules was found, as further confirmed by XPS and SIMS analysis of the catalyst surface. Reusing the catalyst several times showed no reduction in catalytic efficiency confirming that there is no reduction in the active surface over time. However, photocatalytic degradation kinetics of CBZ modelled using the Langmuir-Hinshelwood (L-H) equation showed that the sorption-desorption mechanism exists while the catalyst is "active" under light irradiation. It was found that although sol-gel N-doped TiO2 has some reactivity under visible light (λ > 400 nm), its reactivity sharply increased under UVA/UVB irradiation. Finally, reduced photocatalytic efficiency was found with wastewater effluents as opposed to surface water due to scavengers and high organic content.

M.Sc. student of Dr. Hadas Mamane Steindel, School of Mechanical Engineering, Tel-Aviv University

Reverse osmosis (RO) membranes are the leading technologies for desalination installations applied to salt water resources as sea-water and brackish-water. The increase in desalination technologies for large-scale applications should parallel with an evaluation of the concentrate disposal from an environmental, technical and economical perspective. Reverse osmosis concentrate is disposed by several means as surface water discharge, sewers discharge, deep well injection, evaporation ponds and zero liquid discharge. This research aimed at reclaiming an RO concentrate using softening process as part of the reject recycle system (RRS) used to reduce potential fouling salts in RO systems (e.g. calcium, magnesium and silica). Appling RRS resulted in secondary RO (SRO) at high recoveries (>90%) using sodium hydroxide (NaOH) and soda ash (Na2CO3) as softening chemicals, and sodium aluminate (NaAlO2) as a softening-aid. The experiments examined the optimum combination of chemicals, type and concentration, which resulted in the best salt sedimentation and hence provided better SRO feed water. SEM images combined with elemental analysis were examined for the softening sludge with the various chemical combinations. Integration of RRS/SRO system enabled increasing the overall water recovery from 90% to 97%. The improved recovery was demonstrated theoretically using a commercial RO system design. Comparing economic expenses between RRS/SRO systems to the conventional alternative showed a 15% difference in favor of first one.

Removal of Pharmaceutical Pollutants by Nano-structured TiON Photo-Catalytic Thin Film Surfaces

Inna Horovitz