Heterogeneous catalytic activation of persulfate for the removal of rhodamine B and diclofenac pollutants from water using iron-impregnated biochar derived from the waste of black seed pomace

Waste reutilization in environmental remediation is highly desired as a new strategy in the scientific community for environmental applications. Industrial biowaste has been used significantly to produce biochar, which can be used in environmental remediation. In this study, a low-cost iron-impregnated modified biochar (FeBS800) was successfully prepared using a one-step pyrolysis method with waste black seed pomace as a “waste-to-resource” strategy and applied to activate peroxydisulfate (PDS) for the degradation and mineralization of rhodamine B (RhB) and diclofenac (DCF) in water. The physicochemical properties of the FeBS800 catalyst were investigated by various characterization analytical methods. The developed FeBS800 catalyst exhibits excellent catalytic activity and good stability in PDS activation. In the FeBS800/PDS system, the degradation efficiency within 10 min reached up to 98.2 % and 88.3 %, while the mineralization efficiencies within 30 min reached 48 % and 68.7 % for 20 mg/L RhB and DCF, respectively, with slight iron ions leaching of less than 3 mg/L. The optimum removal conditions of the FeBS800/PDS system were found to be 1.5 g/L catalyst dose and 10 mM PDS initial concentration at circumneutral pH solution. Moreover, the radical quenching experiment revealed that the main reactive oxygen species (ROS) responsible for the pollutants’ degradation in FeBS800/PDS system are in the order of 1O2 > •OH > O2•- > SO4•-, while singlet oxygen plays a leading role. The degradation kinetics of both pollutants (RhB and DCF) were well-fitted to the pseudo-first-order model. Furthermore, a possible mechanism pathway of PDS activation for generation ROS in the FeBS800/PDS system was proposed. Overall, the research results suggested that the modified FeBS800 could have a promising potential in activating PDS for the removal of refractory organic pollutants from water.