ABSTRACT
The MIL-53(Al)-NH2 was designed to remove fluoride with hierarchical hollow morphology. It was used as an adsorbent for fluoride removal at a wide pH range (1-12) due to the positive zeta potential of MIL-53(Al)-NH2. The pH did not significantly influence the fluoride adsorption into MIL-53(Al)-NH2. However, the adsorbent indicated good adsorption capacity with maximum adsorption of 1070.6 mg g-1. Different adsorption kinetic and thermodynamic models were investigated for MIL-53(Al)-NH2. The adsorption of fluoride into MIL-53(Al)-NH2 followed the pseudo-second-order model and a well-fitted Langmuir model indicating chemical and monolayer adsorption process. When mass transfer model was used at initial concentrations of 100 ppm and 1000 ppm, the rates of conversion were 8.4 × 10-8 and 4.7 × 10-8 m s-1. Moreover, anions such as [Formula: see text], [Formula: see text], [Formula: see text], Cl-, and Br- also had less effect on the adsorption of fluoride. Also, experimental and theoretical calculations on adsorption mechanism of MIL-53(Al)-NH2 revealed that the material had good stability and regenerative capacity using alum as regenerant. In a nutshell, the dominant crystal face (1 0 1) and adsorption sites Al, O, and N combined well with F-, HF, and HF2- through density functional theory. It opens a good way of designing hollow MOFs for adsorbing contaminants in wastewater.
Subject(s)
Water Pollutants, Chemical , Water Purification , Adsorption , Fluorides , Hydrogen-Ion Concentration , Water Pollutants, Chemical/analysisABSTRACT
Heteroatoms doping is an important modification method in carbon electrode for CDI technology. In this study, a new facile approach of homogeneous phosphorus doping in carbon matrix was proposed via crosslinking polymerization of m-phenylenediamine and phytic acid. The carbonized composites (NPC) showed the characteristics of phosphorus/nitrogen co-doping with excellent hydrophilicity, high electrochemical performance, lower inner resistance and good cycling stability, far beyond that of carbon without phosphorus doping. Compared with reported similar materials and commercial carbon, the chloride adsorption capacity of NPC used as electrode for deionization capacitors was significantly improved (21.4 mg g-1 in a 500 mg L-1 Cl- solution at 1.2 V). Particularly, based on the charge distribution analysis of phosphorus doping in carbon matrix by using Material Studio calculation, the possible enhanced dichlorination mechanism of the carbon composites as electrode for deionization capacitors was carefully explored. The phosphorus/nitrogen co-doped carbon displayed a promising prospect for chloride removal in the application of CDI technology.
ABSTRACT
The present research developed a direct in situ heterogeneous method to synthesize UiO-66-poly(m-phenylenediamine) core-shell nanostructures by inducing assembly of m-phenylenediamine radical on UiO-66 surfaces. The strong interaction between negative charged UiO-66 and positive radical from the oxidation of monomer is the major driving force. The produced UiO-66-poly(m-phenylenediamine) composites exhibited a distinct core-shell morphology with controllable surface features. The UiO-661-PmPD0.5 showed a uniform PmPD shell with a thickness of 40-60 nm and the nanocomposite exhibited a high specific surface area of 319.77 m2 g-1. Moreover, the Cr(VI) adsorption amount of the polymeric shell in the nanocomposites can reach as high as 745 mg g-1, far beyond the performance of the original PmPD. The adsorption tends to be equilibrium within 300 min. This research opens a hopeful window for facile and large-scale fabrication of core-shell nanostructures with controllable core-shell configuration, exhibiting high prospect in heavy metal removal from water.
