Heterogeneous Activation Of Peroxymonosulfate By Fe-Co Layered Doubled Hydroxide For Efficient Catalytic Degradation Of Rhoadmine B

Nowadays,increasing attention has been paid to the sulfate radical?SO₄^-·?due to its high oxidation efficiency for refractory organic pollutants.Compared with OH·,SO₄^-·has higher oxidation potential,wider p H range and higher degree mineralization for organic pollutants.Furthermore,no plenty of precipitate need to be disposed during the use of SO₄^-·.Peroxymonosulfate?PMS?with stronger self-oxidation and asymmetric structure usually is used as the precursor of SO₄^-·.Cobalt?Co?catalysts are considered as the promising approach to activate PMS.However,the practical application of homogeneous system with Co catalyst is significantly suppressed by the biological toxicity of leaching Co and the potential secondary pollution to the ecological environment.Therefore,the activation of PMS by heterogeneous cobalt sources has been given great attention.In heterogeneous catalytic oxidation,the catalyst is added into the system as a solid,which avoids the direct reaction between metal ions and wastewater.This study investigated the Rh B removal from the dye wastewater in Fe/Co-LDH/PMS system.A highly efficient heterogeneous catalyst Fe/Co-LDH was synthesized by the co-precipitation with Co and Fe.And the Rh B was high-efficiently degraded by SO₄^-·produced from the heterogeneous activation of PMS.Compared to homogeneous Co²⁺/PMS system,Fe/Co-LDH?1:2?/PMS system exhibited much superior degradation performance.The effect of various parameters,such as temperature,initial p H,initial Rh B concentration,PMS dosage and catalyst loading on the Rh B degradation was discussed in detail.Also,the major radical and degradation mechanism was studied.???Preparation of effective heterogeneous catalyst Fe/Co-LDHFe/Co-LDH with different Fe/Co ratio was prepared by double drop co-precipitation method.The prepared Fe/Co-LDH was characterized by XRD,FT-IR,SEM,TEM and XPS.The characterization results demonstrated that Fe/Co-LDH with Fe:Co ratio of 1:2 had high purity and crystallographic structure.And the XPS spectra of Fe/Co-LDH exhibit a satellite bands at records,imply that the Fe and Co in the Fe/Co-LDH exist metal elements Fe³⁺and Co²⁺,respectively.???Rh B degradation in Fe/Co-LDH?1:2?/PMS systemThe Fe/Co-LDH?1:2?/PMS system exhibited high activity to Rh B oxidation.Operational parameters,including catalyst amount,oxidant amount,p H,temperature,and initial Rh B concentration,all had influence on the degradation of Rh B.In the optimum condition:20 mg/L Rh B,0.02 g/L catalyst,and 0.015 g/L PMS,fully decomposition of Rh B could be achieved within 10 min.The Rh B oxidation in Fe/Co-LDH/PMS system can be described well by pseudo-first-order kinetic and the activation energy was calculated to 59.71 k J/mol.???Reaction mechanism and the stability of Fe/Co-LDH/PMS.The quenching experiments using ethanol and tertbutyl alcohol?TBA?as radical scavengers indicated that both SO₄^-·and OH·radicals were generated in Fe/Co-LDH/PMS system and SO₄^-·radicals acted as the predominant reactive species.Rh B was high-efficiently degraded by SO₄^-·which originated from the activation of PMS through the redox reaction between Fe and Co in Fe/Co-LDH catalyst.And Fe/Co-LDH maintained similar catalytic activity during forth runs,suggesting that the catalyst possessed good reusability and stability.Furthermore,more than 90%of Rh B degradation in Fe/Co-LDH/PMS system all was achieved in different water sources,demonstrating that Fe/Co-LDH/PMS system is a new type of advanced oxidation technology with high efficiency and practical application potential.