Efficiency And Mechanism On Methyl Orange Degradation By Natural Schorl Catalyzed Fenton Reaction

Tourmaline, with special crystal chemistry structure and unique properties ofpiezoelectricity and pyroelectricity, has been attracted wide attentions in thefields of environmental protection and health care, owing to its functions ofemitting far infrared radiation, releasing negative oxygen ions and yieldingbiological current. Although there are abundant tourmaline ores in China, theadditional value for its exploration and utilization is so low that much tourmalineores have been exported to foreign countries as raw materials. Hence,fundamental investigations on the tourmaline application require to bestrengthened. At present, the studies on tourmaline’s application in the field ofenvironmental protection are mainly focusing on activating drinking water,adjusting the pH value in water, adsorbing heavy metal ions, purifying air and soon. However, related literatures about its application in Fenton system are rare. Inthis study, natural schorl, selected from the east of inner Mongolia, China, wasapplied as a heterogeneous catalyst in the Fenton system to catalyze H2O2formethyl orange (MO) degradation, and the affecting parameters and mechanismon MO degradation were also discussed furtherly.X-ray diffraction (XRD) result showed that the main phase of sample wasschorl, without any impurities. Fourier transform infrared spectroscopy (FT-IR)result revealed that the FT-IR absorption peaks attributed to [SiO4] tetrahedrongroup,[BO3] triangle group, hydroxyl, water and M-O octagonal group. Scanningelectron microscopy (SEM) result showed that the shape of schorl sample washexagonal column and the crystal boundary of schorl grown well. EngergyDispersive X-ray spectrometer (EDS) result revealed that, besides Si, Al, Na, O elements, the schorl sample contained Fe element, which suggested that thesample used in this study was natural schorl. Thermal analysis showed that theschorl sample had two obvious endothermic peaks at700℃and900℃,respectively.The experimental results revealed that MO could be efficiently discolored bythe natural schorl catalyzed Fenton reaction. The MO discoloration ratioincreased as the solution pH increasing. The optimum dosage of schorl and H2O2was1g and1mL, respectively. Increases in the reaction temperatures and MOinitial concentrations could lead to the MO discoloration ratio increasing. Afterrepeated usage for2times, MO discoloration ratio still kept at100%.Comparative investigations on the MO discoloration ratio in three differentconditions, namely (1) H2O2system;(2) schorl system; and (3) H2O2and schorlsystem, suggested that the MO discoloration was resulted by the mineral-catalyzed Fenton-like system of schorl and H2O2. It was found that the moreferric iron dissolved into the reaction solution from the surface of schorl was, themore·OH formed from H2O2catalyzed by ferric iron was, the higher the catalyticactivity of the system was, and the better MO discoloration ratio could beobtained. At the same time, the spontaneous polarization electric field on thesurface of natural schorl played an important role in enhancing the MOdiscoloration by the natural schorl Fenton system.