Efficient removal of sixteen priority polycyclic aromatic hydrocarbons from textile dyeing sludge using electrochemical Fe2+-activated peroxymonosulfate oxidation-A green pretreatment strategy for textile dyeing sludge toxicity reduction

It is urgent to remove polycyclic aromatic hydrocarbons (PAHs) from textile dyeing sludge (TDS) before its final deposal due to their recalcitrant nature and generation of toxic byproducts during TDS treatment . In this study, an electrochemical Fe 2+ -activated peroxymonosulfate (PMS) oxidation process for removing 16 priority PAHs from real TDS was firstly investigated. The results showed that the removal efficiency of the ∑16PAHs in TDS was positively correlated to the concentration of Fe 2+ released from sacrificial iron anode and the concentration of electroregenerated Fe 2+ in the cathode by the reduction of Fe 3+ within the applied voltage range of 3–7 V, but a higher voltage of 10 V did not lead to further improvement in ∑16PAHs removal due to the radical scavenging reaction resulted from the excessive accumulation of Fe 2+ . 64.7% and 16.1% of the ∑16PAHs were removed in the anodic and cathodic chamber under the optimum reaction conditions of 400 mg/g PMS/VSS, pH 3 and applied voltage 7 V, respectively. low-ring PAHs were preferentially degraded compared to high-ring PAHs. The O ⋅ H ${}^{\cdot }\mathrm{O}\mathrm{H}$ played a major role while SO 4 ⋅ — ${\mathrm{SO}}_4^{\cdot —}$ had a minor role in PAHs degradation in TDS. The intracellular PAHs released from cracked sludge cells were found to undergo further degradation under free radical attack.