Color removal from secondary treated pulp & paper industry effluent using waste driven Fe-TiO₂ composite

In the present study, the concurrent fixed-bed dual technology (photocatalysis and photo-Fenton) was performed as a polishing step for the color removal of tertiary treated agro-based paper & pulp industry effluent. For this purpose, the cheap and visibly dynamic Fe-TiO₂ composite was prepared using industrial waste materials which also promoted the idea of the circular economy. The effectiveness of the prepared composite and the dual process was evaluated in terms of color removal efficiency and rate constant along with optimizing the process factors. Various kinetic models namely Log-linear, Weibull, and Biphasic with shoulder were used for the comparative study of three different processes i.e. photocatalysis, photo-Fenton, and dual process. Several parameters such as pH (4.5), % surface area covered (100%), and H₂O₂ dose (525 mgL^-1) were optimized which gave the best output using dual-process i.e. 91.6% of color reduction along with good R² values i.e. 0.874, 0.981 and, 0.998 for Log-linear, Weibull and, Biphasic with Shoulder model respectively. The proposed composite was durable enough to retain its dual catalytic ability with minor activity reduction of 5-10% even after 50 recycles. Thus, this innovative technology with the dual effect of photocatalysis and photo-Fenton can be a potential bet as a tertiary treatment option in the existing industrial wastewater treatment system for removing color from the final treated effluent.