The Coupling Of FePc-TiO₂ With PVDF Membrane And The Treatment Of Dye Wastewater

Dye wastewater is one of the most untreatable industrial contaminant because of its'high BOD, COD and chroma. Membrane separation process and advanced oxidation technology including catalytic wet oxidation (CWO) and photocatalytic method have received the widespread attention as the present dye wastewater treatment processes. As a biomimetic photocatalyst, metal phthalocyanine (MPc) compounds have a good absorption property in the visible light range and could effectively utilize sunlight to treat dye wastewater. But when the MPc is used alone in an aqueous solution, it is easy to reunite and deactivation. The photocatalytic degradation activity of MPc could be improved by loading it on the carriers like TiO2. The coupling of photocatalyst or CWO catalyst with membrane separation process, can not only keep the respective process characteristics and removal efficiency of their own, but also has a synergistic effect to improve the treating rate. Therefore, in this paper, iron phthalocyanine (FePc) was loaded on the TiO2 to prepare FePc-TiO2 photocatalyst, and then iron phthalocyanine-titanium dioxide/chitosan (FePc-TiO2/CS) material was made to improve catalytic properties of FePc-TiO2. The iron phthalocyanine-titanium dioxide/polyvinylidene fluoride (FePc-TiO2/PVDF) membrane and iron phthalocyanine-titanium dioxide/polyacrylic acid-polyvinylidene fluoride (FePc-TiO2/PAA-PVDF) membrane were prepared to realize the embedded and surface load type that coupling photocatalyst and membrane.The FePc-TiO2/CS material and millipore PAA-PVDF membrane were utilized to get a suspending catalyst-membrane reactor, which can realize the coupling of CWO and membrane separation process.In this paper, the sol-gel method was adopted to get FePc-TiO2 photocatalyst. We carried on the related characterization, took the Acid Orange 7 as the research object, and roughly explored the optimal experimental conditions of dye solution treatment and related mechanism of photocatalytic reaction. The iron phthalocyanine-TiO2/chitosan composite material was firstly prepared by freezing desiccation method. The as-prepared sample was characterized by the field emission electron microscopy(FESEM), fourier transform infrared spectroscopy(FTIR), thermogravimetric analysis(TGA) and used as a catalyst to degrade Acid Orange 7 dyes in aqueous solution. The results showed that the structure of FePc-TiO2/CS was porous and multilayer by freezing desiccation method. FePc can act as the intermediate for the catalytic wet peroxide oxidation(CWPO) and TiO2 was the photocatalyst sensitive to the UV light. The synergistic effect of both and the excellent absorption capability of modified CS made FePc-TiO2/CS have a quick degradation rate to dye solution under the certain UV light, pH and H2O2 dosage. The composite material can degrade at least 90%dye molecules in the solution after 30 minutes. Compared with the industrial photocatalyst P25-TiO2 in the condition without H2O2, the degradation rate of material was increased by 8 times. And the sample also maintained the catalytic activity of degradation and had a good stability when used many times. The flocculent structure of material also made it easy to recycle.The FePc-TiO2 was firstly used to prepare FePc-TiO2/PVDF hybrid membrane and FePc-TiO2/PAA-PVDF membrane respectively by blending and UV illumination-surface grafted method. The structures and chemical properties of membrane surfaces were investigated through the FESEM, FTIR, contact angle measure(CAM) and so on. The photocatalytic decoloration experiments about dye solution, the pure water flux and the retention rate to dye solution of related membranes were carried out to study the actual treatment effect to dye wastewater. The hybrid membrane had a certain visible light catalytic degradation performance, but a poor repeatability and antifouling ability. The surface grafting membrane possessed good anti-pollution, but did not have the activity of photocatalytic degradation due to the low grafting rate of FePc-TiO2.The FePc-TiO2/CS material and millipore PAA-PVDF membrane with good repeatability and stable grafting rate were used to assemble a simple suspending catalyst-membrane reactor in a ultrafiltration cup.The influence of the factors, (such as pH, the concentration and kinds of dye solution) on the treatment effect to dye solution of coupling system were studied. The suspended CWO-membrane coupled method was compared with the sole CWO and membrane separation process about their removal efficiency to dye wastewater. The individual CWO requires several times filtering to reuse catalyst and has a loss of weight. But the membrane in suspension method which can effectively intercept catalyst overcame these problems.