In this article, the novel carbon materials (carbon nanotubes (CNTs) and graphene) with high-specific area and superior mechanical behavior are employed to strengthen the specific capacitance and cyclical stability of manganese dioxide (MnO 2) for supercapacitors. The electrode material, synthesized by the CNTs, reduced graphene oxide (RGO), and MnO 2 (CNTs-RGO-MnO 2 composite), is characterized by scanning electron microscope, transmission electron microscope, and X-ray powder diffraction. The results indicate that the MnO 2 particles are compactly distributed on the surface of the RGO and CNTs. The state of MnO 2 in the CNTs/RGO/MnO 2 composite is d-MnO 2. The electrochemical test results indicate that the specific electric capacities of the CNTs/RGO/MnO 2 composite are 404 F/g, 255 F/g, and 82 F/g, respectively, at 1 A/g, 3 A/g, and 10 A/g ampere densities, which illustrate that the addition of the CNTs and RGO greatly hoists the specific capacitance of the MnO 2. Moreover, the long-time charge-discharge test results indicate that the specific capacitance of the CNTs/RGO/MnO 2 composite remains 70% after 5000 circles under the big current density of 30 A/g. The electrochemical impedance spectroscopy test results show that the RGO and CNTs can remarkably reduce the electric charge shifting resistance; at the same time, the electrolyte resistance and electric charge shifting resistance after the charge-discharge test are scarcely increasing, showing that the CNTs/RGO/ MnO 2 composite is a kind of supercapacitor electrode material with stable structure, which has the prospect of industrialization.

Magnesium ammonium phosphate (MAP) crystallization could be utilized for the recovery of phosphorus from wastewater. However, the effectiveness of the recovery is largely determined by the crystallization process, which is very hard to be directly observed. As a result, a specific ultrasonic device was designed to investigate the crystallization characteristics of MAP under various ultrasonic conditions. The results demonstrated that the metastable zone width (MZW) narrowed along with the rising of the ultrasonic power. Similarly, for the 6mM MAP solution, with the ultrasonic power gradually enhanced from 0W to 400W, the induction time was shortened from 340s to 38s. Meanwhile, the crystallization rate was accelerated till the power reached 350W, and then remained a constant value. It can be observed from the scanning electron microscopy (SEM), the MAP crystal became bigger in size as well as the crystal size distribution (CSD) became broad and uneven, with the increase of ultrasonic power. The results indicate that the crystallization process enhanced by power ultrasound could be used as an effective method to eliminate and recover the phosphorus from wastewater.

In this paper, we have successfully synthesized a cellulose acetate/graphene/MnO 2 (CA/G/MnO 2) composite, which is further employed as an electrode material for supercapacitors. This novel composite material can fully utilize the conductivity of the graphene and the dense internal structure of the cellulose acetate (CA) to increase the specific capacitance of the MnO 2. At the current density of 0.1 A/g, the specific capacitance of the CA/G/MnO 2 composite is 1181 F/g, which is very close to the theoretical capacitance. Moreover, the capacitance of the CA/G/MnO 2 composite finally stabilizes at 93 F/g, after 5000 cycle charge and discharge test under the high current density of 30 A/g. Its capacitance retention rate is 67.4%, which is great higher that the capacitance retention rate of the MnO 2 (44.2%). These results fully indicate that the CA/G/MnO 2 composite has broad application prospects in the field of super capacitor electrode materials.

At present, the crystallization method has become a hotspot in the field of wastewater treatment. The crystallization method not only remove phosphorus effectively in wastewater, but the phosphorus also can be recycled. The crystallization method includes ammonium magnesium phosphate crystallization method, calcium hydroxy calcium phosphate crystallization method, vivianite crystallization method and so on. The study introduced the principle of phosphorus removal and the influencing factors of the three crystallization methods, and discussed the effects of pH, ion concentration and stirring conditions on the crystallization. pH has the greatest influence on crystallization among of them. The best pH of the vivianite crystallization is between 7 and 9, and it is easier to form crystals in the general wastewater than MAP and HAP. In a certain concentration range, the phosphorus removal rate increased with the increase of ion concentration. In the case of air stirring or cyclical stirring, crystallization can be instantly formed, effectively increasing the crystallization rate. Finally, the application prospect of crystallization method in the treatment of phosphorus wastewater is prospected, which provides technical and theoretical support for the removal and recovery of phosphorus in wastewater.

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