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Magnetic carbonate hydroxyapatite/graphene oxide (M-CHAP/GO) was successfully prepared by loading magnetic carbonate hydroxyapatite (M-CHAP) onto graphene oxide sheets and was found to be an ideal adsorbent for heavy metal (Pb(II)) and dye (methylene blue). The obtained adsorbent was characterized by SEM, FTIR, XRD, BET, TGA, XPS and zeta potential, respectively. M-CHAP/GO nano-particles possessed a favorable and stable morphology. Moreover, the good magnetic properties of M-CHAP/GO made it simple to recover from water with magnetic separation. The equilibrium adsorption capacity was 277.7 mg g À1 for Pb(II) and 546.4 mg g À1 for methylene blue under the optimal conditions. The pseudosecond-order equation and the Langmuir model showed good correlation with the experimental data and explained well the mechanism of adsorption. It was found that the adsorption process was accomplished mainly via chelation and ion exchange. Thermodynamic studies (DG < 0, DH > 0, DS > 0) implied that the adsorption process was endothermic and spontaneous in nature. The other adsorption mechanisms are further researched in this article. All the experimental results show that M-CHAP/GO nano-particles have potential application in the future of environmental management.

Combined floating offshore wind platform and wave energy converter (WECs) systems have the potential to provide a cost-effective solution to offshore power supply and platform protection. The objective of this paper is to optimize the size and layout of WECs within the hybrid system under a given sea state with a numerical study. The numerical model was developed based on potential flow theory with viscous correction in the frequency domain to investigate the hydrodynamic performance of a hybrid system consisting of a floating platform and multiple heaving WECs. A non-dimensional method was presented to determine a series of variables, including radius, draft, and layout of the cylindrical WEC at a typical wave frequency as the initial design. WECs with larger diameter to draft ratio were found to experience relatively smaller viscous effects, and achieve more wave power, larger effective frequency range and similar wave power per unit volume in the same sea state. The addition of WECs reduced the maximum horizontal force and pitch moment on the platform, whereas the maximum vertical force increased due to the increasing power take-off force, especially at low frequencies. The results presented in this paper provide guidance for the optimized design of WECs and indicate the potential for synergies between wave and wind energy utilization on floating platforms.

Highlights  HPA-GO was firstly prepared for Pb(II) and methylene blue removal.  The pseudo-second-order model and Langmuir model fitted the adsorption process.  The thermodynamics implied the adsorption was endothermic and spontaneous.  The adsorption mechanisms were discussed.  HPA-GO could be recycled efficiently in the adsorption-desorption cycles.

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