Ce(IV)-Based Metal–Organic Gel for Ultrafast Removal of Trace Arsenate from Water

As a potential replacement for metal–organic frameworks (MOFs), constructing metal–organic gels (MOGs) is an appealing but challenging topic since MOGs are a kind of shapeable MOF gels. Also, the rapid adsorption of trace heavy metal ions in aqueous media remains a serious challenge. Herein, a simple strategy for the synthesis of Ce­(IV)-based metal–organic gel (Ce-MOG) was first developed for the rapid adsorption of trace As­(V). The (NH4)2Ce­(NO3)6 obtains hydroxide bridges after adding apposite NaOH, leading to [Ce6O4(OH)4]12+ clustering and inducing fast and excessive nucleation rates, which also leads to coordination disturbance of MOF nanocrystals to obtain Ce-MOG. The Ce–OH groups are the key to gel formation through hydrogen bonding and are the active site for the ultrafast adsorption of As­(V). As expected, the resultant Ce-MOG has an excellent adsorption rate, making it possible to effectively decontaminate 500 ppb of As­(V) to below the World Health Organization (WHO) recommended threshold for drinking water (10 ppb) within 1 min. It achieves equilibrium adsorption in 10 min, and the final arsenate-removing efficiency reaches 99.8%. For Ce-MOF, the effluent concentration of As­(V) is higher than the drinking water standard, while equilibrium adsorption takes 60 min. The initial adsorption rate of Ce-MOG, h(k 2 q e 2) is calculated and indicated to be 67.67 mg g–1 min–1, about 19.96 times that of Ce-MOF (3.39 mg g–1 min–1). As such, the excellent As­(V) decontamination rate, selectivity, and reusability of Ce-MOG indicate its great potential for practical drinking water purification.