Preparation Of Heterogeneous Fenton Catalyst Derived From Paper Mill Sludge And Study On Catalytic Performance

The treatment of dye wastewater has been a big challenge in the field of industrial wastewater treatment for high chromaticity, complex components, biological toxicity. Recently, heterogeneous Fenton process has developed rapidly and exhibits a promising application prospect in treatment of dye wastewater. The key of heterogeneous Fenton technology lies in the catalysts. Thus, it is pivotal to find stable, extensive and low cost catalyst. Paper mill sludge, which was extensive, with high content of inorganic substance and was difficult to handle, can be used for the preparation of heterogeneous Fenton catalyst, promoting resource utilization of paper mill sludge.This paper put forward a new thought about preparation of heterogeneous Fenton catalyst derived from paper mill sludge for treatment of dyeing wastewater. Paper mill sludge-derived nanocomposite heterogeneous catalyst was synthesized using paper mill sludge and FeSO4·7H2O as raw material via a facile method. A series of study on catalyst performance, operation condition and reaction kinetics of heterogeneous Fenton and heterogeneous photo-Fenton degradation of Methylene Blue was carried out. Repeated degradation experiments were conducted to evaluate the stability and service life of the as-synthesized catalyst. The main conclusion in the paper are as follows:1. Preparation of heterogeneous Fenton catalyst derived from paper mill sludge. Nanocompostite catalyst (PMS-Fe-400) with high stability and catalytic ability was synthesized using paper mill sludge and FeSO4·7H2O as raw material. The optimum parameters (FeSO4·7H2O/paper mill sludge mass ratio 0.4:1, calcination temperature 400℃, calcination time 60 min) for preparation of the catalyst were obtained by single factor experiments. The as-prepared catalyst was fully characterized by SEM、 XRD、EDX、BET、FT-IR、DSR characterization methods. The results indicated that iron element was present in the catalyst in the form of α-Fe2O3, and new chemical bonds Si-O-Fe were formed between iron element and silicon dioxide. The BET surface area of the catalyst was 19.37 m2/g, and many 2-10 nm mesoporous was observed. The catalyst can response to visible light and UV, and it has excellent dispersion in solution, which has good magnetic performance and can be withdrawn by magnetic field.2. Degradation of Methylene Blue by heterogeneous Fenton using catalyst derived from paper mill sludge. The catalytic activity of PMS-Fe-400 was evaluated by degradation of Methylene Blue under PMS-Fe-400/H2O2 heterogeneous Fenton system. Under optimum conditions (1 g/L of catalyst,2 mL/L of 3% H2O2,50 mg/L of Methylene Blue, initial pH=4),92.4% discoloration and 75.6% mineralization were achieved within 90 min, and the process was pseudo first-order. The study of reaction mechanism suggested that it was the heterogeneous Fenton process not homogeneous Fenton process that play the important role for the degradation of Methylene Blue, and hydroxyl radical was the main radical. Moreover, leaching tests indicated that the leached iron is negligible (<0.5 mg/L).The reusability and stability of PMS-Fe-400 were evaluated in five repeated runs, which suggested that PMS-Fe-400 manifested excellent stability of catalytic activity.3. Degradation of Methylene Blue by heterogeneous photo-Fenton using catalyst derived from paper mill sludge. Visible light was introduced into PMS-Fe-400/H2O2 heterogeneous Fenton syetem to optimize the reaction parameter, and the catalytic activity of PMS-Fe-400 was evaluated by degradation of Methylene Blue under PMS-Fe-400/H2O2 heterogeneous photo-Fenton system. Under optimum conditions (0.6 g/L of catalyst,1 mL/L of 3%H2O2,20 mg/L of Methylene Blue, initial pH=5), 98% discoloration and 85% mineralization were achieved within 120 min, and the process was pseudo first-order. Methylene Blue could be efficiently degraded at a pH range from 2 to 8 in the heterogeneous photo-Fenton system. The study of reaction mechanism suggested that it was the heterogeneous Fenton process not homogeneous Fenton process that play the important role for the degradation of Methylene Blue, and hydroxyl radical was the main radical. Moreover, leaching tests indicated that the leached iron is negligible (<0.21 mg/L). The reusability and stability of PMS-Fe-400 were evaluated in five repeated runs, which suggested that PMS-Fe-400 manifested excellent stability of catalytic activity.