In-situ dual effect studies using novel Fe-TiO2 composite for the pilot-plant degradation of pentoxifylline

An inexpensive sunlight responsive Fe-TiO2 composite has been fabricated for the in-situ photo-degradation of an environmentally persistent pharmaceutical drug, pentoxifylline (PEN). There was sustainable leaching of iron into the solution through composite under acidic conditions thus exhibiting in-situ dual effect (photocatalysis and photo-Fenton) at the same time in the treatment unit. Scale-up studies were performed in a simple non-concentrating fixed-bed reactor using these Fe-TiO2 composite with total volume handling of 5 L. The main strength of the study lies in the demonstration of reduction in treatment time to nearly half with overall synergy (32.4%) of dual process over individual processes. The process was intensified with proper optimization of all operating parameters like flow rate, number of baffles, catalyst and oxidant dose. The photonic efficiency of the system incorporating dual effect employing Fe-TiO2 composite under all optimized conditions was increased to 1.62% with almost 93% removal of PEN after 4 h of treatment. The Fe-TiO2 composite was durable enough to be successfully recycled for more than 35 runs without any significant reduction in degradation efficiency. The recycled composite retained the TiO2 nanoparticles along with existence of iron as confirmed through various characterization techniques like SEM/EDS, XRD, DRS, FTIR and Raman spectroscopy. The generation of various anions, evolution of CO2 and reduction in COD and TOC along-with formation of various intermediates (confirmed through GC-MS analysis) were studied to validate the mineralization of PEN. An approximate cost of the overall process has also been evaluated to envisage the commercial applications of the studied technique.