Application Research Of Paper Mill Sludge-derived Activated Carbon In Heterogeneous Fenton Reaction

The treatment of dye wastewater has been a difficult problem in the field of printing and dyeing and sewage treatment industries for complex components, high chromaticity, 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, one of the hot spots is to develop stable, extensive and low cost catalyst support. Paper mill sludge, as a biomass resource, which was extensive with high content of inorganic substance and was difficult to handle, can be reprocesseed into paper mill sludge-derived active carbon which attributed to new technologies. The active carbon can be used for the preparation of heterogeneous Fenton catalyst support, promoting resource utilization of paper mill sludge.In this paper, a new method of sludge utilization and treatment of printing and dyeing wastewater was proposed. At first, paper mill sludge is used as the precursor to produce carbon through carbonization and activation processes, then heterogeneous catalyst was systhesized using paper mill sludge-derived active carbon and FeSO4·7H2O, CuSO4·7H2O as raw material via a facile method. A series of study on catalyst performance, operation condition and rection kinetics of heterogeneous Fenton degradation of Methylene Blue was carried out. Repeated degradation experiments were conducted to evaluate the stablity and serivice life of the as-systhesized catalyst. The main conclusions in the paper were as follows:1. The optimized preparation condition of sludge-derived active carbon was obtained. The best preparation condition of carbonization was under the protection of nitrogen, paper mill sludge in pipe type oven at lab, roasting 500℃ and 2h, then the best preparation condition of activation is sulfuric acid with the concentration which is about 5mol/L by the degradation effect and characterization results. The BET surface area of the paper mill sludge-derived active carbon was 231.21m2/g. Moreover, the active carbon has flourishing porous structure, higher absorb capability and rich surface functional group. SAC catalyst has its unique crystal structure of Fe1.33+2Fe0.67+3(SO4)2(OH)0.67·xH2O and 2Fe(OH)SO4, besides Fe2O3. More than that, this lower pH environment endow OH with a stronger oxidation capacity.2. The best preparation condition is FeSO4·7H2O and CuSO4·7H2O total molar quantities of 20mmol and ratio of 9:1, SAC catalyst support of 2g, roasting 500℃ and 2h by the degradation effect and characterization results. Under the same conditions, Cu2+ doping effect on SAC-Fe/Cu catalyst make the particle size decrease and particle distribution becomes narrow, then good for form of α-Fe2O3. The bimetals can show synergies in degradation of Methylene Blue with increased content of CuO. And it has excellent dispersion in solution.3. There was synergy between SAC-Fe/Cu-500℃ and H2O2, which has a good effect to methylene blue’s degradation and less in dosage. The best condition of heterogeneous Fenton in degradation of Methylene Blue which initial concentration is 100 mg/L, is that catalyst dosing is 0.1 g/L, H2O2 is 6mL/L, and initial pH=4. The decolorization rate can reach 100% after 80min, when TOC removal rate is about 71.14%, the effect of optimized reaction system for Methylene Blue treatment is good. There will not be a large number of sludge with iron after reaction. The catalyst has high value with the characteristic of stability and longevity.4. Methylene Blue was degradated in the reaction process, without absorption peak at 664 nm after 80min of the reaction, Methylene Blue decolorizing reaction basic completely, while TOC removal rate is about 71.14%, which indicated TOC removal lags behind Methylene Blue decolorization. The study of reaction mechanism suggested that it was the heterogeneous Fenton process not homegeneous Fenton process that play the important role for the degradation of Methylene Blue, and hydroxyl radical was the main radical. The reaction rate was positively correlated with catalyst dosing and H2O2 dosing, while negatively correlated with initial pH. The initial pH was a major affect on the reaction rate, and H2O2 dosing had the minimal impact on the reaction rate.