Hybrid metal and non-metal activation of Oxone by magnetite nanostructures co-immobilized with nano-carbon black to degrade tetracycline: Fenton and electrochemical enhancement with bio-assay

Electrochemically synthesized magnetite nanostructures (ESMNPs) as a metal activator and nano-carbon black (NCB) as a non-metal activator were co-immobilized by alginate natural polymer to activate Oxone for the degradation of tetracycline (TC) antibiotic. The formation of sulfate radical was indirectly confirmed during the Oxone/ESMNPs/NCB/alginate process via the addition of scavenging compounds. This study revealed the high reusability potential of the ESMNPs/NCB/alginate with a negligible decrease in the degradation rate from 5.7 x 10(-2) to 4.9 x 10(-2) min(-1) after four experimental runs. The release of iron ions into the effluent did not violate its discharge standard, indicating high stability of the catalyst due to the co-immobilization. The enhanced degradation rate of 6.7 x 10(-2) min(-1) was observed under basic conditions. Both Fenton (7.9 x 10(-2) min(-1)) and electrochemical (7.7 x 10(-2) min(-1)) processes improved the degradation effectiveness at hydrogen peroxide concentration of 30 mM and current density of 100 mA, respectively. Response surface methodological optimization of the bio-assessment was also performed. Accordingly, the optimized TC concentration of 68 mg/L, Oxone concentration of 1.6 mM and exposure time of 60 min resulted in the minimum inhibition percent (%) of 15.8%. Confirmatory real experiments demonstrated the results of numerical optimization. Possible degradation pathways along with the ECOSAR-based bioassay of the intermediates were also proposed.