Liquidizing crystal MIL-100(Fe) to coating silica powder for purifying wastewater

Although MIL-100(Fe) was regarded as an ideal material for the environmental remediation, it could not be applied in practical because of the potential eco-environmental risk and cost. In this work, a novelty strategy of liquidizing crystal MIL-100(Fe) was posted for the first time through inhibiting the crystallization process and forming physical MIL-100(Fe) gel. Due to this MIL-100(Fe) sol–gel, MIL-100(Fe) could easy cover on the surface of silica powder (SiO 2 ) through simple soaking operation. MIL-100(Fe) covering on SiO 2 (MIL-100(Fe)@SiO 2 ) could be quickly separated from wastewater spontaneously owing to the carrier of SiO 2 , even in a tank of 2.0 m, which made it possible for purifying wastewater in practical. MIL-100(Fe)@SiO 2 could remove phosphate with a removing ratio of closing 100 % at an initial concentration of 10 mg/L, while more than 95 % towards methyl orange (MO). The removing ratio of MO by MIL-100(Fe)@SiO 2 did not obviously decrease when the concentration of MO increased to 100 mg/L. And the adsorption performance of phosphate did not affect by pH among 3.0–9.0. The adsorption amount exceeded 50 % of maximum adsorption capacity for phosphate within 30 min, while 90 % for MO. Monodentate mononuclear coordination could explain the adsorption of phosphate by MIL-100(Fe)@SiO 2 . The N atom in MO might be acted as Lewis acid to coordinate with MIL-100(Fe)@SiO 2 . After adsorption, the P-saturated and MO-saturated MIL-100(Fe)@SiO 2 could be effectively regenerated by the dilute HCl and NaOH solution, respectively. The recovery ratio of adsorption capacity for phosphate and MO were up to 97.7 % and 71.6 %.