Photoactivation and photoregeneration of TiO2/PAC mixture applied in suspension in water treatments: approach to a real application.

The process TiO2/PAC/UV-vis has been under study and compared with the isolated treatments of adsorption and photocatalysis determining possible synergies between adsorption and photocatalysis of target antibiotics: amoxicillin, enrofloxacin, sulfadiazine, and trimethoprim. The characterization of the TiO2/PAC mixture was carried out via FESEM and FTIR. Moreover, a kinetic study has been performed. The effect of UV-vis radiation and the type of matrix was analyzed in TiO2/PAC/UV-vis process. The performance of this treatment has been monitored during three cycles, evaluating also the regeneration of TiO2/PAC mixture by UV-vis light. TiO2/PAC/UV-vis process allowed the removal of the antibiotics in the range 90-100% (an average removal of 93% of the initial concentration) after 60 min of treatment. However, only amoxicillin showed a significant synergy applying TiO2/PAC/UV-vis process. Regarding matrix effect, no influence of the matrix type (ultrapure water or treated wastewater) was observed. Since PAC tends to be deactivated gradually, the TiO2/PAC/UV-vis process performance decreases after each cycle in a 15% average. Finally, regeneration via UV-vis light started to be effective after a total of 4 h of regeneration.

Antibiotics removal from aquatic environments: adsorption of enrofloxacin, trimethoprim, sulfadiazine, and amoxicillin on vegetal powdered activated carbon.

This study addresses the growing concern about the high levels of antibiotics in water, outlining an alternative for their removal. The adsorption of four representative antibiotics from commonly used families (fluoroquinolones, ß-lactams, trimethoprim, and sulfonamides) was performed over vegetal powdered activated carbon. The evolution of the adsorption was studied during 60 min for different initial antibiotic concentrations, not only individually but also simultaneously to determine competitive adsorption. Moreover, this research studied the adsorption isotherms and kinetics of the process, as well as the pH influence; FTIR of the activated carbon before and after adsorption was carried out. Trimethoprim and sulfadiazine showed more affinity for the adsorbent than amoxicillin and enrofloxacin. This trend might be attributed to their structure, capable of stablishing stronger π-π interactions with the adsorbent, which showed high affinity for the active sites of the adsorbent via FTIR. In addition, the sorption isotherms of trimethoprim followed a Langmuir type isotherm, amoxicillin followed a Freundlich type isotherm, and enrofloxacin and sulfadiazine followed both. The antibiotics followed pseudo-second-order kinetics. Sulfadiazine and amoxicillin gave better performances in acidic conditions. By contrast, the sorption of trimethoprim was favored in basic environments. Variations of pH had a negligible effect on the removal of enrofloxacin.

Performance comparison of commercial TiO2: separation and reuse for bacterial photo-inactivation and emerging pollutants photo-degradation.

This research aims to compare the disinfection and degradation effectiveness in water of a commercial suspension of nano-TiO2 (TiO2Levenger) with the standard TiO2Degussa P25. Photo-inactivation and photo-degradation experiments were conducted with UVA-vis light. Concerning the disinfection, the effects of TiO2 dose (0-2 g/l), water matrix, bacterium type (Gram-positive or Gram-negative), and bacterial regrowth after the photo-treatments were studied for each catalyst. The experimental results show that Enterococcus sp. (Gram-positive) was more resistant to the photo-treatments than Escherichia coli (Gram-negative) for both catalyst; however, postirradiation trends showed similar behavior for both bacteria, favoring regrowth for short-treated cells and decay for longer-treated ones. Caffeine was selected as a model substance of pharmaceuticals and personal care products. In terms of caffeine removal, the effects of TiO2 dose (0-2 g/l) and water matrix were analyzed. Besides, the comparison between mechanical coagulation-flocculation-decantation and simple decantation of TiO2 was carried out. The results show that simple decantation allowed the recovery of 97.5% of TiO2 Degussa P25 and TiO2 Levenger within 1 day of simple decantation, while applying the proposed mechanical coagulation-flocculation decantation 99.7% of recovery of both catalysts was achieved in 2 hours. Finally, the subsequent reuse of both catalysts was proved with little loss of efficiency in terms of photo-disinfection during the four cycles. Nevertheless, the standard TiO2 Degussa P25 photo-degradation efficiency of caffeine decreases considerably as compared to commercial suspension of TiO2 Levenger concerning the reutilization.