Investigation On The Deep Treatment Of Pulping Effluent By Heterogeneous Catalytic Ozonation Process

Technology of heterogeneous catalytic ozonation with high utilization rate of ozone,relatively low processing cost and without secondary pollution etc, has good prospects ofdevelopment.In order to develop an effective γ-Al2O3 supported catalyst in the treatment ofpulping effluent with catalytic ozonation,at first,advanced treatment of pulping effluent withozone catalyzed by γ-Al2O3 and each factors on effluent degradation of effect wasinvestigated.Then selected optimal γ-Al2O3 supported type of single metal,binary metalcombination and catalyst preparation parameters, the prepared catalyst wascharacterized.Finally,investigate effect of pulping effluent degradation with catalyticozonation.The results showed that the ozonation catalyted by γ-Al2O3 can significantly improveremoval rate of CODCr. With the increase of the initial p H of the solution, catalytic ozonationwith γ-Al2O3 can increase the the removal rate of CODCr at first, then decreased slightly. Theremoval rate of CODCr increased at first with the increase of temperature, then decreasedquickly when temperature was 45℃.With the increase of ozone concentration and amount ofcatalysts, the removal rate of CODCr increased significantly, the amplitude of CODCr reductionfirst increased then decreased. The catalytic ozonation with γ-Al2O3 can also improve theremoval rate of AOX and the biodegradability of pulping effluent.Using p-chlorophenol as model pollutant to select single metal species supported onγ-Al2O3 which has the best catalytic performance.The results showed that the catalyticproperties:Mn/γ-Al2O3 >Fe/γ-Al2O3 > Ni/γ-Al2O3 > Cu/γ-Al2O3 > Zn/γ-Al2O3≈γ-Al2O3, theoptimum preparation conditions for Mn/γ-Al2O3 catalyst were : in 1 mol/L Mn(NO3)2solution by isometric impregnation, dried and roasted 4h under 700℃. The Mn/γ-Al2O3 wascharacterized, and the results showed that manganese ion was mainly in the form of Mn3O4 loading in γ-Al2O3 surface; after loading, the crystallinity,specific surface area,pore volumeand pore size of γ-Al2O3 decreased slightly; Mn loading was 4.84%. Under experimentconditions of p H 8, catalyst dosage 7 g/L, ozone concentration 35 mg/L, CODCr reduction ofpulping effluent reached 68%, BOD5 /CODCr is 0.62 at the same time, the removal rate ofAOX content reached 85.0%.Using p-chlorophenol as model pollutant to select binary metal species supportedon γ-Al2O3 which has the best catalytic performance.Results showed that catalytic activity were Mn-Ni/γ-Al2O3>Mn-Fe/γ-Al2O3>Mn-Zn/γ-Al2O3>Mn-Cu/γ-Al2O3.Mn-Ni/γ-Al2O3 The optimal preparation conditons of Mn-Ni/γ-Al2O3 was that: solution ratio of Mn(NO3)2and Ni(NO3)2 was 3:2 by a co-impregnation method,the calcination temperature was500℃,the calcination time was 6h. The prepared catalyst Mn-Ni/γ-Al2O3 was characterized, results showed that manganese and nickel ion dispersed well on the surface ofγ-Al2O3, the supported γ-Al2O3 maintained good mechanical strength and stability, the loading of Mn and Ni were 4.66% and 2.73% respectively. The response surface methodology was used to optimize advanced treatment of pulping wastewater by Mn-Ni/γ-Al2O3 catalytic ozonation.when p H was 8.71, the dosage of catalyst was 9.15 g/L, ozoneconcentration was 29.6 mg/L,reaction was 30 min, the removal rate of CODCr canreach 74.7%.The catalytic ozonation had obviously depressed action on the structure of aromaticcompounds、carbonyl structure、phenols and alcohols in wastewater. GC-MS analysis showedthat the γ-Al2O3 loading metal catalytic ozonation degraded organic pollutants and hard partlybiodegradable organic matter in wastewater effectively. On the whole catalyst had goodstability and repetition. The oxidation system of Mn/γ-Al2O3 and Mn- Ni/γ-Al2O3 catalyticozonation followed the hydroxyl free radical mechanism.