We have optimized the synthesis of the nanofique catalytic bionanomaterial and developed a prototype batch reactor. Initially, the synthesis of the nanofique comprised a series of 5 stages between the conditioning of the fibers and subsequent immobilization of the iron oxide nanoparticles to obtain the final material. In order to reduce time and cost in the preparation of the nanofique, crucial parameters were evaluated at each stage of the synthesis. Once all the parameters were evaluated in detail, the number of stages to obtain the nanofique was reduced to 3 stages making unnecessary the conditioning of the fibers (brushing and cleaning) and discarding the use of hydrochloric acid in the alkalinization stage. In addition, the fiber load for the synthesis of nanofique was increased from 10% to 12.5%, and discarding the final drying process of the nanofique fibers allowed its use in a direct manner. The new nanomaterial was characterized by spectroscopic techniques such as SEM, EDX, XRF, UV-VIS, and XRD. The optimized nanofique was able to remove up to 90% of color from an indigo carmine solution at a concentration of up to 500 ppm in approximately 2 minutes. Furthermore, reusability testing in an indigo carmine simulated solution demonstrated that the new material can degrade the dye for up to 20 cycles without losing nanofique catalytic properties. It is worth noting that this new methodology was applied to obtain 1 kg of nanofique at a laboratory scale using commercial rather than analytical grade reagents reducing costs. color removal in a test solution of indigo carmine was not affected by the up-scaling of the synthesis or the use of commercial-grade reagents.
Once the synthesis and color removal parameters were optimized, a prototype of a batch reactor was designed based on the deliverable D4.2. The design contemplated the incorporation in the reactor of a perforated grid-type basket where the nanofique is loaded so that it is in continuous contact with the dye solution. the design also contemplated the inclusion of an inlet and an outlet valve to simulate the entrance of the textile wastewater into the reactor and the subsequent exit of the treated water. Successful color removal tests were performed on 100 ppm indigo carmine solutions at 1 L scale in the reactor using aeration instead of mechanical agitation. A series of experiments were conducted to find the optimal conditions for the batch prototype to be operational. Once optimized, the technical team tested the process on a prototype reactor (5 L/h) located at the Konya Technical University. The operating conditions for color removal with Nanofique were optimized using aqueous solutions of indigo carmine as model wastewater. However, for the actual testing of the prototype, real wastewater samples from the textile industry supplied by ERAK (Denim Manufacturing and Development Center, Turkey) were used following the optimal operating conditions of the experimental design.
Overview of results:
A new synthetic procedure was validated to obtain nanofique in fewer steps and with better performance than traditional synthesis. Furthermore, this new method was applied in the scale-up synthesis of nanofique up to 1 Kg.
Critical variables such as temperature, hydrogen peroxide concentration, and nanofique loading were found to be the most important parameters for the color removal capability of the nanofique system according to the experimental results carried out at a laboratory scale as well as on a small pilot scale.
Color removal of real textile wastewater samples from the ERAK industry was performed successfully in a small pilot reactor at Konya Technical University removing up to 90% of the color in a 30 L wastewater volume scale.
Key costs for obtaining nanofique material were analyzed. It was found that it is possible to synthesize nanofique with low-cost commercial grade reagents without losing catalytic performance. Also, synthetic steps were eliminated as it was shown that they do not affect the material obtaining and catalytic activity.
