MDPI - Publisher of Open Access Journals

12 pages, 3933 KB

Open AccessArticle

Facile Adjustment of Exposed Crystal Facet of Hematite Derived-From Goethite to Enhance Cr (VI) Sorption

by Yuxin Li, Guocheng Lv, Limei Wu, Zhaohui Li and Libing Liao

Crystals 2023, 13(1), 79; https://doi.org/10.3390/cryst13010079 - 1 Jan 2023

Cited by 9 | Viewed by 3694

The (110) facets of hematite have excellent adsorption performance for chromium. We aim to obtain hematite with a large specific surface area and exposed (110) facets by using natural needle-like goethite as the precursor. The derived hematite shows a significant increment in the removal capacity of chromium by six times compared with goethite under the same experimental conditions. Structural model fitting of extended X-ray absorption fine structure (EXAFS) spectroscopy suggested that the interatomic distance of Cr-Fe was approximately 3.6 Å for the Cr (VI) coordinated hematite with exposed (110) facets, which was characteristic of the form of bidentate binuclear surface complex. Molecular dynamic simulations for the arrangement of Cr (VI) in (110) facets of goethite and hematite indicated the superiority of hematite adsorption for chromium. We optimized efficient and economic permeable reactive barrier (PRB) materials by crystal plane adjustment based on these experimental and theoretical results. It was found that the life span of the column even reached 610 PVs when the initial concentration of Cr (VI) was 20 mg/L, which indicates its potential application in the field of PRB medium material. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

► Show Figures

Figure 1

24 pages, 5264 KB

Open AccessFeature PaperArticle

Using Density Functional Theory to Model Realistic TiO₂ Nanoparticles, Their Photoactivation and Interaction with Water

by Daniele Selli, Gianluca Fazio and Cristiana Di Valentin

Catalysts 2017, 7(12), 357; https://doi.org/10.3390/catal7120357 - 24 Nov 2017

Cited by 36 | Viewed by 9765

Abstract

Computational modeling of titanium dioxide nanoparticles of realistic size is extremely relevant for the direct comparison with experiments but it is also a rather demanding task. We have recently worked on a multistep/scale procedure to obtain global optimized minimum structures for chemically stable spherical titania nanoparticles of increasing size, with diameter from 1.5 nm (~300 atoms) to 4.4 nm (~4000 atoms). We use first self-consistent-charge density functional tight-binding (SCC-DFTB) methodology to perform thermal annealing simulations to obtain globally optimized structures and then hybrid density functional theory (DFT) to refine them and to achieve high accuracy in the description of structural and electronic properties. This allows also to assess SCC-DFTB performance in comparison with DFT(B3LYP) results. As a further step, we investigate photoexcitation and photoemission processes involving electron/hole pair formation, separation, trapping and recombination in the nanosphere of medium size by hybrid DFT. Finally, we show how a recently defined new set of parameters for SCC-DFTB allows for a proper description of titania/water multilayers interface, which paves the way for modeling large realistic nanoparticles in aqueous environment. Full article

(This article belongs to the Special Issue Titanium Dioxide Photocatalysis)

► Show Figures

Figure 1

Search Results (2)

Further Information

Guidelines

MDPI Initiatives

Follow MDPI

Saved Queries

Search Filter Reset All

Years

Feature Papers

Subjects

Journals

Article Types

Countries / Regions

Search Results (2)

Further Information

Guidelines

MDPI Initiatives

Follow MDPI