Adsorption and photoreduction of Cr(Ⅵ)via diatomite modified by Nb2O5 nanorods

We report the design and synthesis of Nb2Os@diatomite composite materials.The composite materials are prepared by the hydrothermal conversion of raw diatomite and activated niobic acid powder in ammonium oxalate aqueous solution,with various hydrothermal reaction durations.The specific surface area of the diatomite modified by Nb2Os nanorods reaches a maximum of 153 m2 /g,which is almost five times higher than that of raw diatomite.Insights are gained into the function of sodium dodecyl benzene sulfonate and the mechanism of loading Nb2O5 on diatomite in the solution phase.The controllable growth dynamics allow the morphology and production of the Nb2O5@diatomite structure to be controlled.Adsorption experiments indicate that the diatomite modified by Nb2O5 nanorods is an effective adsorbent for quickly removing Cr(Ⅵ) from wastewater at room temperature.The maximum adsorption capacity is 115 mg/g.The Cr(Ⅵ) removal capacity is further improved under ultraviolet light irradiation,owing to the synergistic effect of surface adsorption and Nb2O5 photoreduction.The composite therefore has potential practical application.

Nb_2O_5 nanowires in-situ grown on carbon fiber: A high-efficiency material for the photocatalytic reduction of Cr(Ⅵ)

Niobium oxide nanowire-deposited carbon fiber（CF） samples were prepared using a hydrothermal method with amorphous Nb2O5·nH2O as precursor. The physical properties of the samples were characterized by means of numerous techniques, including X-ray diffraction（XRD）, energy-dispersive spectroscopy（EDS）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, selected-area electron diffraction（SAED）, UV–visible spectroscopy（UV–vis）, N2 adsorption–desorption, Fourier transform infrared spectroscopy（FT-IR）, and X-ray photoelectron spectroscopy. The efficiency for the removal of Cr（VI） was determined.Parameters such as pH value and initial Cr（VI） concentration could influence the Cr（VI） removal efficiency or adsorption capacity of the Nb2O5/carbon fiber sample obtained after hydrothermal treatment at 160°C for 14 hr. The maximal Cr（VI） adsorption capacity of the Nb2O5 nanowire/CF sample was 115 mg/g. This Nb2O5/CF sample also showed excellent photocatalytic activity and stability for the reduction of Cr（Ⅵ） under UV-light irradiation： the Cr（VI） removal efficiency reached 99.9% after UV-light irradiation for 1 hr and there was no significant decrease in photocatalytic performance after the use of the sample for 10 repeated cycles. Such excellent Cr（VI） adsorption capacity and photocatalytic performance was related to its high surface area,abundant surface hydroxyl groups, and good UV-light absorption ability.

Fabrication and characterization of Ce_(0.7)Zr_( 0.3)O_2 nanorods having high specific surface area and large oxygen storage capacity

Nanorod-like Ce0.7Zr0.3O2 solid solutions were synthesized by a sodium dodecyl sulfate-assisted precipitation method. The samples were characterized by means of scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and specific surface area measurement. Typical Ce0.7Zr0.3O2 nanorods were 40 nm in average diameter and 450 nm in length, with specific surface area and oxygen storage capacity of 194 m2/g and 374 μmol/g, respectively.

Controlled synthesis of Zeolite adsorbent from lowgrade diatomite:A case study of self-assembled sodalite microspheres

Highly efficient and sustainable conversion technologies to generate uniform sodalite(Na8(AlSiO4)6(OH)2)zeolite micro spheres with low-grade waste natural diatomite as raw materials via a solution-mediated crystallization route were developed in the present study.The synthesis process can be considered as an in-situ zeolitization of diatomite precursor without involving any me so scale template and any post-synthetic modification.The mass ratios of diatomite and AlCl3·6 H2 O have remarkable effect on the morphology,crystal structure and porosity of sodalite zeolite product.The preferred sodalite microspheres with uniform mesoporous of size 3.5-5.5 nm and large surface area of 162.5 m2/g exhibit well removal performance for heavy metal ions(Pb(II),Cd(II),Zn(II),and Cu(II)),with the highest adsorption abilities for Pb(II)ions of 365 mg/g.In addition,the effect of contact time,initial ion concentration,competitive adsorption and solution pH were evaluated.The removal performance results from synergistic effects of dominating cation-exchange and additional surface chemisorption.The study may broadly help unveil chemical control reactions of the zeolitization processes of diatomite,and thus facilitates the development of promising zeolite materials for the use in natural and engineered aquatic environments by recvcling waste diatomite resources.

Flower-, wire-, and sheet-like MnO_2-deposited diatomites:Highly efficient absorbents for the removal of Cr(Ⅵ)

Flower-, wire-, and sheet-like MnO2-deposited diatomites have been prepared using a hydrothermal method with Mn（Ac）2, KMnO4 and/or MnSO4 as Mn source and diatomite as support. Physical properties of the materials were characterized by means of numerous analytical techniques, and their behaviors in the adsorption of chromium（VI） were evaluated. It is shown that the IvinO2-deposited diatomite samples with different morphologies possessed high surface areas and abundant surface hydroxyl groups （especially the wire-like MnO2/diatomite sample）. The wire-like MnO2/diatomite sample showed the best performance in the removal of Cr（VI）, giving the maximum Cr（VI） adsorption capacity of 101 mg/g.

Water-bathing synthesis of high-surface-area zeolite P from diatomite

Zeolite P was synthesized for the first time via a novel water-bathing route at 90℃ using scrubbed diatomite, sodium hydroxide, and aluminum hydroxide as precursor, with SiO2/Al2O3, SiO2/Na2O, and H2O/Na2O molar ratios of 7.43, 3.81, and 80.00, respectively. The as-fabricated samples were characterized by means of scanning electron microscopy, X-ray diffraction, and nitrogen adsorption measurements. This study showed that （i） treating the diatomite raw material with sodium hexametaphosphate could open the pores in the diatomite via removal of the clay clogged in its pores; （ii） tetragonal mesoporous zeolite P samples with a surface area of 56-60 m2/g could be generated after 6-24 h of water-bathing reaction at 90℃; （iii） extension of water-bathing reaction time could improve the mesoporous structure of zeolite P; and （iv） Ca2＋ adsorption capacity of the zeolite P sample was about 300 cmol/kg. Such high-surface-area porous zeolite P could be used as an effective adsorbent for the treatment of water containing calcium and magnesium ions.

Fabrication of nano-sized Ca(OH)_2 with excellent adsorption ability for N_2O_4

Uniform nano-sized calcium hydroxide （Ca（OH）2） monocrystal powder was synthesized from calcium oxide in a surfactant solution via a digestion method by decreasing the surface tension of the reaction system to control the growth of crystalline Ca（OH）2. The Ca（OH）2 monocrystal powder samples were characterized by means of scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, high resolution transmission electron microscopy （HRTEM）, X-ray diffraction （XRD）, Brunauer-Emmett-Teller （BET）, and Fourier transform-infrared spectroscopy （FT-IR）. The NOx adsorption ability of the samples was evaluated, and the influence of various types and concentrations of surfactants on powder agglomeration and then the specific surface area in the precipitation process were studied. The specific surface area of the samples was found as high as 58 m2/g and 92 m2/g and the particle size, 300-400 nm and 200-300 nm in the presence of 10 wt% PEG600 and 0.086 mL/L SDS at a reaction time of 5 h, respectively. The product has an exceptionally strong adsorption ability for NOx, which makes it a highly promising adsorbent for emission control and air purification.