Preparation And Its Application Of Graphene Based Catalyst For The Removal Of Carbamazepine

Cabamazepine is one of the representative compound of pharmaceutical and personal care products?PPCPs?.The long-term exposure of its residues after using to the environment poses a potential risk to the ecological environment and human health.Due to the refractory nature of carbamazepine,it is difficult to completely degrade it by the conventional processes of sewage treatment plants.Photocatalytic degradation,characterized with mild,efficient and energy-saving reaction conditions,has attracted more and more attention in the treatment of PPCPs.The existing photocatalysts have weaker visible light response and easy recombination of electron-hole pairs,resulting in lower catalytic efficiency.Graphene can be employed as a two-dimensional crystalline material with excellent electron conductivity,and an ideal photocatalyst carrier.Thus combining graphene with visible light response catalysts is expected to suppress the recombination of electrons and hole pairs through the excellent electron conduction properties of graphene,and improve the stability and photocatalytic performance of the catalyst.The comparison experiments were carried out to evaluate the performances of graphene/silver phosphate?rGO/Ag₃PO₄?and graphene/yttrium vanadate?rGO/BiVO₄?catalysts for photocatalytic degradation of carbamazepine,and the former one was preferred.After optimization,the preparation conditions of graphene doping amount of0.7%,hydrothermal temperature of 180°C,and hydrothermal time of 9 h were determined.The characterization results indicated that the combination of graphene and silver phosphate could control the growth and agglomeration of silver phosphate,and improve the specific surface area and visible light absorption capacity of the material,thus improving the photocatalytic performance of the material.The photocatalytic degradation of carbamazepine by rGO/Ag₃PO₄ was investigated.It was found that the combination of graphene and silver phosphate could greatly improve the photocatalytic activity of the catalyst and improve its stability.Complete degradation of 200?g/L carbamazepine could be achieved in 6 min when the following conditions were employed:pH of 5⁹,graphene doping amount of 0.7%,catalyst dosage of 200mg/L,and 300 W xenon lamp full-wave irradiation.The degradation rate of rGO/Ag₃PO₄photocatalytic system was greatly affected by the initial concentration of carbamazepine and the dosage of catalyst,but not by the temperature and pH.The coexisting substances such as Cl^-,SO₄²-,HCO₃^-and humic acid in water exhibited inhibitory effects on the degradation of carbamazepine.In order to facilitate the recovery and reuse of rGO/Ag₃PO₄,the author prepared the magnetic graphene composite catalyst?Fe₃O₄/rGO/Ag₃PO₄?by the introduction of nano-Fe₃O₄.Even though the photocatalytic activity of Fe₃O₄/rGO/Ag₃PO₄ decreased slightly when compared with that of rGO/Ag₃PO₄,it could also completely degrade 200?g/L carbamazepine in 32 min under the conditions of wide pH range of 5⁹,catalyst dosage of 200 mg/L,300 W xenon lamp full-wave irradiation.Also,similar influence variations of various factors were found for Fe₃O₄/rGO/Ag₃PO₄ reaction system.Fe₃O₄/rGO/Ag₃PO₄ had good recovery performance,with the magnetic separation recovery rate of 89%.After 5 cycles,the degradation performance could still reach over79%,showing excellent catalytic stability.