Synthesis and Performance of Nano Magnetic Modified Bentonite Materials
|School||Wuhan University of Science and Technology|
|Keywords||bentonite nano Fe3O4 Fenton-like recycled water coking wastewater|
Advanced oxidation processes, a kind of new wastewater treatment techniques boomed inrecent decades represented by Fenton-like technique, can efficiently eliminate refractory organics.Coking wastewater containing various non-biodegradable organics, such as Polycyclic AromaticHydrocarbons, is a classic sort of refractory organic wastewater. The chemical oxygen demand（COD） and chroma of the effluent of secondary bio-chemical treatment process barely meetindustrial wastewater emission standards. This study is designed to synthesize a newheterogeneous magnetic Fenton-like catalyst, which is then used in oxidation of simulationwastewater and advanced treatment of coking wastewater. The study is briefly summarized asfollow:（1） Al-pillared bentonite was synthesized via ion exchange method, with nature bentoniteused as raw material and Al-pillaring solutions. The optimum synthesis condition was Al/clay=10mmol/g, calcination tempreture=400℃. BET and XRD characterization results show thatthe basal spacing of bentonite grew up to1.82nm from original1.50nm, with BET surfaces areaincreasing from72.30m2·g-1to130.96m2·g-1.（2） Nano magnetic bentonite with two different Fe3O4contents （30%marked by M30and50%marked by M50） were prepared by in-situ synthesis method using Al-pillared bentonite assupport. The obtained materials were characterized by FTIR spectra, XRD, BET and SEM. Thespherical Fe3O4nanoparticles disperse on the surface of clay, with no obvious aggregation. Thespecific surface areas of M30and M50were128.16m2·g-1and103.83m2·g-1.（3） The synthesized catalysts were used in catalytic oxidation of simulation wastewater (0.5mmol·L-1Orange II solution). At optimal conditions,100%discoloration and80%of UV254removal were reached （after3h of reaction）, using M50in the following reaction conditions:catalysts dose0.7g·L-1, T=50℃, initial pH3.0and initial H2O2concentration=21.0mmol·L-1.COD decreased from336mg·L-1to44.27mg·L-1at the same condition. Two catalysts showedsimilar catalytic performance in contrast tests carried out in different temperatures and initial pH.（4） UV-irradiation can accelerate the catalytic oxidation. The synergistic effect between UV-H2O2system and Fe3O4NP–H2O2system further improved the degradation of OII.100%discoloration and97%UV254removal rate were achieved in the following reaction conditions:catalysts dose0.6g·L-1, T=30℃, initial pH3.0and initial H2O2concentration=21.0mmol·L-1.Reusability of the catalysts was improved obviously for temperate reaction conditions.（5） The COD of the effluent of the wastewater (COD=140mg·L-1, chroma=400) werereduced to54.44mg·L-1in the following conditions: catalyst dosage=0.7g·L-1, initial pH=2.5,T=40℃and initial H2O2concentration=17.6mmol·L-1. The chroma in all conditions reducedbelow30. The treated wastewater met the recycled water standards of GB/T19923-2005(COD≤60mg·L-1, chroma≤30). The removal rates of COD and chroma in4cycles remain stable.