氧化铜/海泡石催化过滤膜的制备及其过硫酸盐活化性能

Preparation of CuO/Sepiolite Catalytic Filtration Membrane and Its Activation Performance for Peroxymonosulfate

为了开发具有高活性、高稳定性和绿色环保的过硫酸盐催化剂,采用浸渍-过滤成膜-干燥-煅烧的方法制备一种CuO/海泡石催化过滤膜,并对其催化过硫酸盐的性能和活化机理进行了探究。通过X射线衍射仪、扫描电子显微镜、透射电子显微镜等手段详细表征了CuO/海泡石催化过滤膜的晶体结构、形貌、表面性质等,明确了制备催化过滤膜的最佳条件(煅烧温度为400℃、硝酸铜溶液的浓度为20 mmol/L)。经过连续催化降解15 L的10 mg/L的对硝基苯酚(PNP)溶液后,CS-400催化过滤膜的性能未出现明显下降且结构未被明显腐蚀。最后,通过自由基淬灭实验证明了羟基自由基(·OH)和单线态氧(^(1)O_(2))是此催化反应体系中降解PNP的主要活性物质,并提出了可能的催化机理。

Introduction Sulfate radical-based advanced oxidation processes(SR-AOPs)are a highly promising technology for water treatment,and their processing capacity is strongly influenced by the catalyst.However,the currently reported catalysts are mostly powder-based and cannot meet the requirements of recovery and mass transfer in practical applications.Catalytic filtration membrane is a functional membrane that combines catalysis and filtration.It not only provides support for the catalyst,ensuring its recovery,but also limits the reaction to pores,facilitating close contact between pollutants and active sites,thereby achieving efficient utilization of peroxymonosulfate.Sepiolite is an excellent catalyst carrier because of its excellent thermal stability,strong adsorption capacity,and abundant acid-base sites.In addition,sepiolite is a high-quality film-making material,with fibers interwoven into a mesh structure in the same or different directions.In the paper,we successfully prepared a novel CuO/sepiolite catalytic filtration membrane(CuO/sepiolite)with excellent catalytic performance according to the process route of impregnation-filtering coating-drying-calcination.Moreover,we have also explored its performance and activation mechanism for catalyzing peroxymonosulfate method.Methods Typically,0.1 g sepiolite was dispersed in 20 mL of 20 mmol/L Cu(NO3)2 solution to obtain suspension A.Suspension A was heated to 30℃and stirred continuously for 3 h.Then,the mixed suspension was filtrated through polyethylene(PE)microfiltration membrane(0.45μm)and dried at 60℃for 12 h to obtain precursor.The dried precursor was placed in a muffle furnace and heated to 400℃with heating rate of 5℃/min,and kept for 2 h to obtain a catalytic membrane.The catalytic membrane was cut into a circle with a diameter of 50 mm,named CS.A series of catalytic membranes were prepared by changing the calcination temperature(300,400,500,600 and 700℃),named CS-X,where X represents the calcination temperature.X-ray fluorescence spectrometer(XRF)(Panalytical,Axios MAX)was applied to measure the chemical composition.The Cu content was quantitatively measured using acid dissolution method combined with inductively coupled plasma atomic emission spectroscopy(ICP-AES)(PerkinElmer,Optima 8300).The crystal structure was obtained by using X-ray powder diffractometer (XRD) (Dandong Tongda, TD-3500). The functional groups on the surface of catalytic filtration membranes were detected throughusing Fourier transform infrared spectrometer (FTIR) (Thermo Fisher, Nicolet iS50). The microstructure and structural characteristicsof the membrane material were observed by using scanning electron microscopy (SEM) (TESCAN, MIRA3 XMU/XMH) andhigh-resolution transmission electron microscopy (HRTEM) (FEI, Talos F200X).A lab-made catalytic filtration system was established to evaluate the catalytic performance of the CS. The inside diameter offiltration is 50 mm and the valid test area of CS was around 19.6 cm2. The simulated wastewater flowed through the catalytic filtrationfrom top to bottom at a specific flow rate. Prior to catalytic degradation experiment, the feed PNP solution firstly flowed through thecatalytic filtration system to achieve adsorption-desorption equilibrium. Then, the catalytic reaction was started by adding a specificmass of peroxymonosulfate (PMS). After a specific interval, filtrate was collected for measurement of absorbance, ion leachingconcentration and TOC in alkaline conditions. The removal ratio (R) is calculated based on equation (1):0 t0C C100CR-= ´ (1)where C0 and Ct are concentrations of pollutants in feed and filtrate after reaction time t, respectively.Results and discussion The main conclusions of this paper are summarized as following. When the calcination temperature was400 ℃ and the concentration of copper nitrate solution was 20 mmol/L, the catalytic filtration membrane (CS-400) had the bestcatalytic performance. After the continuous catalytic degradation of 15 L of p-nitrophenol solution at a concentration of 10 mg/L, theperformance of CS-400 catalytic filtration membrane did not show any significant degradation, and its structure was not significantlydamaged. Hydroxyl radical was the main reactive oxygen species for the degradation of p-nitrophenol in this catalytic reaction system.The CuO/sepiolite catalytic filtration membrane is a potentially valuable peroxymonosulfate catalyst with promising applications inwastewater treatment.