Synthesis And Performance Of Nano Magnetic Modified Bentonite Materials

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.