Preparation Of Catalysts With Attapulgite Supported And Application On Degradation Of Organic Pollutants

Advanced oxidation technology,is a kind of organic waste water treatment method with simple reaction condition,strong oxidation and complete degradation,uses hydroxyl radical(·OH)to effectively destroy organic pollutants structure.However,this oxidation technology suffers from narrow pH range and secondary pollution defects.At present,many scholars used bentonite,carbon nano materials,graphene and fly ash with a relatively large surface area of the material as a carrier.And heterogeneous Fenton catalysts were prepared with loading the metal oxide particles on the carrier to overcome these two challenges.Attapulgite(ATP)is a magnesium silicate mineral with a special chain structure,a large number of microporous channels and a high specific surface area,which gives the material a better adsorption for contaminant.In this paper,a novel magnetic heterogeneous Fenton catalysts were prepared by using ATP as carrier and Fe3O4 and Ce/Fe oxides as supports,respectively.The microstructure and crystal type of materials was observed by various characterization techniques.Investigation of catalytic performance by using ethidium bromide and rhodamine B(RhB).The main results of this thesis are as follows:(1)Attapulgite(ATP)was impregnated with Fe3O4 nanoparticles via precipitation.The as-prepared ATP-Fe3O4 nanocomposites were characterized with scanning electron microscope,transmission electron microscopy,X-ray diffractometer,etc.The characterization techniques confirmed Fe3O4 particles with an average size of about 15 nm were successfully embedded in matrix of ATP.Comparison of pre-treatment ATP preparaed materials degradation efficiency,The activated ATP-Fe3O4(A-ATP@Fe3O4)composites has better catalytic activity and adsorption of ethidium bromide(EtBr).This is mainly because of larger surface area of A-ATP@Fe3O4 that increases the reactive sites,produced a rich OH for the A-ATP@Fe3O4/H2O2 catalytic system.Meanwhile,the optimal operation parameters include T=323K,pH=2.0,30 mM H2O2,1.5 g/L A-ATP@Fe3O4.EtBr degradation kinetic studies indicated that,pseudo-first-order kinetic constant was 2.445 min-1 under optimal condition.Moreover,regeneration study suggested that A-ATP@Fe3O4 maintained over 80%of maximal EtBr degradation capacity after five successive cycles.Both radical scavenging experiment and Electron Paramagnetic Resonance confirmed that both hydroxyl(·OH)and superoxide anion(·O2-)radicals were involved in EtBr degradation system.(2)Nanoscaled CeO2/Fe2O3-ATP composites with different molar ratios of Ce3+ to Fe3+were prepared by impregnation method as a heterogeneous Fenton-like catalyst for RhB degradation and characterized by SEM,HTEM,XRD and XPS.The catalytic activity was evaluated in view of the effects of various processes,molar ratios of Ce3+ to Fe3+,pH value,catalyst addition,hydrogen peroxide concentration,and temperature,respectively.Our results showed that C8F2A nanoparticles with an average size of 8～10 nn were uniformly dispersed on the surface of ATP.With the increase of molar ratios of Ce3+ to Fe3+,the degradation rate of RhB increased firstly than decreased.And the pseudo-first-order kinetic constant of 5.175min-1 with removal rates of 98%was obtained for RhB degradation at T=323K and pH 1.5 with 15 mmol·L-1 H2O2,1.0 g·L-1 C8F2A,and 80 mg·L-1 RhB after 900 s.Meanwhile,the conversion rate of TOC reached about 48%under the standard reaction conditions.(3)Combined visible light and Fenton Technology(heterogeneous-Photo-Fenton)to study the degradation efficiency of RhB by Fe3O4@ATP and CeO2/Fe2O3@ATP under relatively mild external environment(pH=4.5,T=298 K).Fe3O4@ATP(96%)had higher removal rate than CeO2/Fe2O3@ATP(46%)under the system of visible photo-like-Fenton,which mainly due to a relatively narrow band gap of Fe3O4@ATP that has a greater ability to excite electrons.The Box-Behnken design was used to evaluate the influence of RhB initial concentration,Fe3O4@ATP catalyst,H2O2 concentration and reaction time at pH = 4.5 on RhB degradation efficiency.The results showed that the maximum RhB degradation efficiency of 96%was obtained at 0.5 g/L Fe3O4@ATP catalyst,15 mmol/L H2O2,40 mg/L RhB and after 5 h reaction time.The removal efficiency of total organic carbon(TOC)reached 30%with only 0.217 mg/L of release of iron,and the degradation reaction of Fe3O4@ATP for RhB degradation.Besides,since the magnetism of Fe3O4@ATP is much stronger than CeO2/Fe2O3@ATP,the separation and reuse of Fe3O4@ATP are easier and more convenient.The prepared Fe3O4@ATP nanoparticles still retained its stability and activity(90%of RhB removal efficiency)after four times cycles,which was a potential catalyst in practical applications.