## 1 Introduction  
Uranium, as an important resource of nuclear fuel [1], could be released into the aquatic ecological environment through various sorts of nuclear-related procedures including waste treatment, spent fuel reprocessing, nuclear accidents, and so on [2; 3; 4; 5]. Uranium primarily exists in the form of uranyl (\(\text{U}\text{O}_{2}{}^{2+}\)) ion with good solubility and fluidity [6; 7] at pH \(\leq\) 5, which has high toxicity and carcinogenicity even with trace amounts and has an exceedingly long half-life of \(-10^{8}\) years [2; 8; 9; 10]. Therefore, there is an urgent need to develop functional materials to capture U(VI) from radioactive water. Adsorption methods, as diffusely utilized wastewater treatment approaches, have received much attention due to their excellent removal performance, high availability and ease of operation [11; 12; 13; 14; 15]. So far, various materials have been exploited for removal of U(VI), such as metal organic frameworks (MOF) [16; 17; 18; 19], functionalized mesoporous silica [20; 21; 22], carbon-based nanomaterials [23; 24; 25; 26], and natural polymers [24; 27]. In general, superior adsorbents should meet the combined requirements of high adsorption capacity, ultra-fast removal rate, high selectivity, stability, and recyclability. However, few of the adsorption materials mentioned above could cover all these characteristics. Importantly, the adsorption selectivity of U(VI) is a significant characteristic, due to the co-existing metal ions in the wastewater that could also compete with U(VI) on the adsorption sites of the adsorbents [4; 20; 28; 29]. Furthermore, the conventional preparation of U(VI) adsorbents is multiplex, costly, and not eco-friendly. Therefore, it is highly imperative to exploit a facile strategy to fabricate efficient adsorbents for U(VI) with high selectivity.  
Cellulose, as the most abundant natural polymer, could be obtained from various natural resources including plants, woods, and so on. Because of its exceptional characteristics such as environmentally friendly, biodegradability, and low cost, it can be employed as adsorbents [30; 31; 32]. Moreover, cellulose has an abundance of hydroxyl groups [33; 34; 35], which could be modified with functional groups such as sulpho groups, carboxyl groups, and amino groups [36; 37; 38]. Pumpkin planting is very common and there is abundant waste pumpkin vine in rural China, which is an abundant feedstock to derived cellulose. In this research, in view of the above environmental requirements, a reasonable synthetic strategy is developed to fabricate a novel phosphonic acid and acrylic acid functionalized pumpkin vine based cellulose adsorbent (PVKAP) for efficient elimination of U(VI) with high selectivity. Owing to the strong complexation between phosphonate sites (P=O) in the polymeric matrix and U(VI) [39], the PVKAP probably shows excellent selectivity and high removal performance to U(VI). Therefore, a series of characterizations are carried out to analyze the physico-chemical characteristics of pumpkin vine cellulose (PVK) and PVKAP. Batch experiments and ICP-AES are adopted to explore the adsorption behavior and selectivity of PVK and PVKAP to uranium under different conditions. Furthermore, the potential adsorption mechanism was, in detail, revealed by FTIR and XPS techniques. This work demonstrates a novel and important strategy to obtain excellent adsorbents with high selectivity and capacity for capturing U(VI) in aqueous solution.