טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentAltai Bach
SubjectWater Purification by Advanced Oxidation Processes
Using Nano Particles
DepartmentDepartment of Chemical Engineering
Supervisor Professor Emeritus Semiat Raphael
Full Thesis textFull thesis text - English Version


Abstract

Municipal and industrial wastewater treatments generate high amounts of residual dissolved organic contaminants (DOC) that must be removed in order to achieve the desired degree of quality for reuse. Water scarcity and environmental considerations are leading the search for alternatives to industrial and urban wastewater reclamation.

The objective of this research was to study the fundamentals and applicability of the Fenton like process innovative technique (H2O2/nano-iron oxide) in order to mineralize DOC from wastewater as an alternative or complementary technique for biological treatment. The research focused on mineralization of DOC, such as phenol, ethylene glycol and municipal wastewater using the advanced oxidation process in the presence of iron oxide nanoparticles, originated from hydrolysis of FeCl3×6H2O, as a catalyst and H2O2 as an oxidant.

The mineralization mechanism and kinetics of phenol using H2O2/iron oxide system was studied initially. Rate constants for the degradation of H2O2 and the mineralization of phenol were determined and correlated with the generation of hydroxyl radicals and iron species. Approximately 30 moles of H2O2 were required in order to mineralize one mole of phenol. The optimal weight ratio between H2O2 and total iron, resulting in 85% phenol mineralization, was found to be 7.

Reuse of iron oxide nanoparticles, as a catalyst of DOC in H2O2/ iron oxide mineralization process, was investigated. The results indicate that at least seven cycles of catalytic mineralization-recovery were feasible without any reduction in the catalytic properties of the iron oxide.

Regeneration of exhausted granular activated carbon (GAC) was investigated by saturating it with filtered municipal wastewater followed by H2O2/ iron oxide oxidation. Results showed high efficiency of the catalytic recovery of the exhaust GAC by the H2O2/ iron oxide oxidation, enabling relatively inexpensive reuse of the adsorbent.

GAC was also used as a support to the iron oxide nanoparticles. The immobilized iron was supposed to catalyze the oxidation reaction inside the GAC pores by reacting with the H2O2 which diffuses from the bulk solution. Regeneration displayed a decreasing efficiency down to nearly 50% after four cycles.

Finally, the GAC catalytic properties in the GAC/iron oxide/H2O2 system were evaluated. It was found that the GAC accelerated the formation rate of ferrous ions, (which is known to be the rate-limiting constituent in hydroxyl radical production), compared to H2O2/ iron oxide system in the Fenton process. It was shown that ethylene glycol mineralization rate was increased by more than 50% in the presence of GAC.