Modified layered double hydroxides by using Fe-rich porous biochar derived from petrochemical wastewater sludge for enhancing heterogeneous activation of peroxymonosulfate towards chloramphenicol degradation

Layered double hydroxides (LDHs) is one of the popular catalysts for peroxymonosulfate (PMS) activation, but LDHs has a challenge in particles aggregation that impacts their catalytical activity. Biochar carrier could effectively disperse LDH particles on its surface. This study for the first time used petrochemical sludge biochar (PSC) to prepare CoFe-LDH@PSC_x composites, the catalytic performances of which were evaluated by PMS activation towards chloramphenicol (CAP) degradation. Results suggested CoFe-LDH@PSC_1:2 had a sponge-like surface with high surface area (188.53 m² g⁻¹). CoFe-LDH@PSC_1:2/PMS system could quickly degrade 97 % of 20 mg L⁻¹ CAP from bulk solution within 20 min under the optimal reaction conditions (0.12 g L⁻¹ CoFe-LDH@PSC_1:2, 0.6 mM PMS, and pH 3.0). TOC removal in this system could reach 73.3 % at the same time. CAP degradation kinetic constant (k_obs) of CoFe-LDH@PSC_1:2/PMS system reached 0.129 min⁻¹ that was 2.8 and 4.4 times higher than that of CoFe-LDH/PMS and PSC/PMS system, respectively. The excellent degradation performance was attributed to the fast redox cycle of ≡Co(II)/≡Co(III), ≡Fe(II)/≡Fe(III) and redox-active groups of C=C/C=O on catalyst, facilitating electron transfer for PMS activation to more reactive species ([rad]OH, SO₄[rad]⁻, [rad]O₂⁻ or ¹O₂) for CAP degradation. Fe⁰ in catalyst was also beneficial for promoting ≡Co/≡Fe redox cycle. CAP degradation pathways were proposed based on intermediates identified by LC-MS. Overall, this work demonstrated CoFe-LDH@PSC_1:2 was a promising catalyst for PMS activation towards antibiotics degradation. Converting hazardous petrochemical sludge to “green” catalyst followed the concept of substantiable development.