Three-dimensional (3D) titanates hierarchical macro/nano-architectures constructed by one-dimensional (1D) nanobelts are successfully synthesized by a hydrothermal-calcining process using metal Ti particles as a precursor. Their morphology and structure are characterized, and their photocatalytic reactivity to tetracycline hydrochloride (TC) is evaluated under visible-light irradiation. The results show that the 1D nanobelts are formed through hydrothermal reaction, and then those 1D nanobelts encircle the metal Ti particles precursor to form 3D macro/nano-architectures. The products with different phase composition, from hydrated titanium oxides to sodium titanates, are obtained by increasing the post-calcining temperatures from 200 degrees C to 800 degrees C. The photocatalytic degradation of TC is observed for all samples under visible-light irradiation, and the sample calcined at 600 degrees C achieves the best photocatalytic reactivity. The visible-light performance of as-synthesized catalysts is considered as a charge-transfer mechanism initiated by the photoexcitation of the surface-complex between TC molecules and titanates, and then followed by the photosensitization mechanism. Two intermediates are identified in the photodegradation process using liquid chromatography combined with mass spectrometry. In addition, the as-synthesized titanates are stable and can be used repeatedly, showing their promising prospect in the practical applications.
With chitosan and sodium alginate as the main raw material, the sponge adsorbents were satisfactorily prepared by freeze-drying and curing molding by CaCl2. The structure of sponge was characterized by FTIR and SEM and its physical property was measured.
In this paper, the electrochemical oxidation and differential pulse voltammetry (DPV) determination of catechol (CC) and hydroquinone (HQ) are studied at a novel carbon nano-fragment (CNF) modified glassy carbon electrode (CNF/GCE). The CNF modifier is prepared using the graphite cycled in lithium-ion batteries as the raw material through a ball mill process. The redox reactions of CC and HQ at the CNF/GCE are a two proton and electron process and controlled by the diffusion step. Compared to the GCE, the as-prepared CNF/GCE shows enhanced electrocatalytic activity and a peak potential difference of about 104 mV towards the oxidation of CC and HQ in a 0.1 mol L−1 acetate buffer solution (ABS, pH = 5.9), which makes it suitable for simultaneous determination of CC and HQ by DPV. Under the optimized conditions, the oxidation peak current of CC is linear over a range from 2.0 × 10−6 mol L−1 to 2.0 × 10−4 mol L−1 in the presence of 5.0 × 10−5 mol L−1 HQ with a detection limit of 1.0 × 10−7 mol L−1 (S/N = 3). Correspondingly, the oxidation peak current of HQ is linear over a range from 6.0 × 10−6 mol L−1 to 2.0 × 10−4 mol L−1 in the presence of 5.0 × 10−5 mol L−1 CC with a detection limit of 2.5 × 10−7 mol L−1 (S/N = 3). In addition, this CNF/GCE exhibits high selectivity, reproducibility and stability, showing its promising application prospect.
In this study, crashed autoclaved aerated concrete (CAAC) was recycled as a solid waste for the removal of low concentration of phosphate (1 mg/L). The effects of dissolved calcium (Ca2+) and pH on phosphate removal were investigated. The materials including calcium chloride (CaCl2) and calcium carbonate (CaCO3) were selected to investigate the removal mechanism of low concentration of phosphate by CAAC. X-ray fluorescence, X-ray diffraction patterns, FT-IR, SEM, and EDS analyses were used to characterize the surface shape, contained elements, and internal structure of CAAC. Results showed that the removal rate of phosphate was increased according to the increase in pH. The CAAC showed poor effect on phosphate removal at acidic condition, but had great removal efficiency in the pH range of 10–12 due to the formation of hydroxyapatite (HAP, Ca5(OH)(PO4)3) corresponding to characterization. Dissolved calcium and insoluble calcium compounds in CAAC can combine with the phosphate and hydroxyl groups to form HAP in alkaline condition and subsequently remove the phosphate. SEM images exhibited the surface of CAAC including some pieces of irregular crystal. After phosphate removal, its surface was covered with a layer of agglomerations confirmed to be HAP according to characterization. To avoid adjusting the pH of solution to strong alkalinity, CAAC was modified by sodium hydroxide solution (NaOH) to increase its activity. Modified products showed a high efficiency for phosphate removal (98.67%). Collectively, the present results demonstrated that the employment of crystallization using CAAC could be a promising technology for the advanced treatment of phosphate from low concentration in municipal secondary effluent.
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