Graphene-modified melamine sponges (RGO-MSs) were prepared, as adsorbents with photothermal conversion ability, utilizing solar energy to achieve heavy oil temperature rise, viscosity reduction, and efficient adsorption recovery of highly viscous oil. The RGO-MSs were prepared through a simple impregnation method. The photothermal performance and heavy oil adsorption performances of RGO-MSs with different densities and thicknesses were observed. It was found that as the density increases, the thermal conductivity of RGO-MS increases too, leading to the increase of the average oil absorption rate. The reduction of thickness is beneficial to improving of the adsorption rate. The prepared RGO-MS with a density of 21.5 mg/cm−3 and a height of 1 cm (RGO-MS-3-1) shows excellent mechanical properties and fatigue resistance. Cyclic adsorption–desorption of RGO-MS-3-1 was achieved through extrusion/ ethanol washing. After 10 cycles of reuse through extrusion, the adsorption capacity decreased from 52.90 to 50.02 g g− 1, with a loss of 5.4%. The material was then washed with petroleum ether and ethanol in turn. Its adsorption capacity can restored to 98.8% of the initial value, showing a promising application prospect on heavy oil leakage treatment. The easily prepared RGO-MS exhibits excellent light absorption and photothermal oil adsorption properties, providing a good solution for the problem of heavy oil leakage at sea.

Easily prepared graphene-modified melamine sponge and its solar-aided adsorption performance on viscous oil
    Abstract
        Graphical abstract
    1 Introduction
    2 Materials and methods
        2.1 Materials and apparatus
        2.2 Preparation of graphene-modified melamine sponge
        2.3 Calculation of porosity and pore volume of graphene-modified melamine sponge
        2.4 Photo-thermal performance evaluation
        2.5 Heavy oil adsorption performance observation
    3 Results and discussion
        3.1 Photo-thermal performance
        3.2 Light-aided heavy oil adsorption
            3.2.1 Graphene-modified melamine sponge with different porosities
            3.2.2 Graphene-modified melamine sponge with different thickness
        3.3 Characterization
            3.3.1 Light absorbance
            3.3.2 SEM
            3.3.3 FT-IR
            3.3.4 XRD
            3.3.5 Hydrophobic performance
        3.4 Mechanical property and reusing of the composite material
    4 Conclusions
    Acknowledgements 
    References

• Mingkan Fan(State Key Laboratory of Heavy Oil Processing, China University of Petroleum (East China), Qingdao 266580, Shandong Province, People’s Republic of China)
• Huie Liu(State Key Laboratory of Heavy Oil Processing, China University of Petroleum (East China), Qingdao 266580, Shandong Province, People’s Republic of China)
• Qilin Guo(State Key Laboratory of Heavy Oil Processing, China University of Petroleum (East China), Qingdao 266580, Shandong Province, People’s Republic of China)
• Yingbo Zhang(State Key Laboratory of Heavy Oil Processing, China University of Petroleum (East China), Qingdao 266580, Shandong Province, People’s Republic of China)
• Shuang Chen(State Key Laboratory of Heavy Oil Processing, China University of Petroleum (East China), Qingdao 266580, Shandong Province, People’s Republic of China)
• Wanqing Zhang(State Key Laboratory of Heavy Oil Processing, China University of Petroleum (East China), Qingdao 266580, Shandong Province, People’s Republic of China)
• Qi Shen(State Key Laboratory of Heavy Oil Processing, China University of Petroleum (East China), Qingdao 266580, Shandong Province, People’s Republic of China)
• Xiangyan Dou(State Key Laboratory of Heavy Oil Processing, China University of Petroleum (East China), Qingdao 266580, Shandong Province, People’s Republic of China)