Catalytic reductive dechlorination of p-chlorophenol in water using Ni/Fe nanoscale particles

Nanoscale bimetallic Ni/Fe particles were synthesized from the reaction of sodium borohydride （NaBH4） with reduction of Ni^2＋ and Fe^2＋ in aqueous solution. The obtained Ni/Fe particles were characterized by TEM （transmission electron microscope）, XRD （X-ray diffractometer）, and N2-BET. The dechlorination activity of the Ni/Fe was investigated using p-chlorophenol （p-CP） as a probe agent. Results demonstrated that the nanoscale Ni/Fe could effectively dechlorinate p-CP at relatively low metal to solution ratio of 0.4 g/L （Ni 5 wt%）. The target with initial concentration ofp-CP 0.625 mmol/L was dechlorinted completely in 60 rain under ambient temperature and pressure. Factors affecting dechlorination efficiency, including reaction temperature, pH, Ni loading percentage over Fe, and metal to solution ratio, were investigated. The possible mechanism of dechlorination ofp-CP was proposed and discussed. The pseudo-first- order reaction took place on the surface of the Ni/Fe bimetallic particles, and the activation energy of the dechlorination reaction was determined to be 21.2 kJ/mol at the temperature rang of 287-313 K.

Assessing the effectiveness of nanoscale zero-valent iron particles produced by green tea for Cr(VI)-contaminated groundwater remediation

Nanoscale zero-valent iron particles(NZVI) produced by using green tea(GT) extract as a reductant can remove Cr(Ⅵ) from water effectively,which can be utilized in groundwater remediation.In order to define the reaction mechanism and removal effect in the aquifer,in this study,GT-NZVI particles were prepared and measured by some characterization methods to define their surface performance,and then batch and one-dimensional experiments were carried out to reveal the reaction properties of GT-NZVI and Cr(Ⅵ) in groundwater.The results showed that the prepared GT-NZVI particles were regular spherical with a diameter of 10-20 nm,which could disperse in water stably.The main component of GT-NZVI wasα-Fe with superficial polyphenols as a stabilizer.GT-NZVI suspension had good ability to reduce the Cr(Ⅵ) to Cr(Ⅲ) in water.When the concentration of GT-NZVI was 1 g/L,the removal efficiency of Cr(Ⅵ)with an initial concentration of 100 mg/L reached 92.8% in 1 h reaction.In column tests,GT-NZVI passed through the natural sand column successfully with an average outflow percentage of 71.2%.The simulated in-situ reaction zone(IRZ) with GT-NZVI was used to remediate Cr(Ⅵ) contaminated groundwater.The oufflow concentration of Cr(Ⅵ) kept in 0.14-0.32 mg/L corresponding to the outflow rate below 0.32%within 15 days,and the removal efficiency of Cr(Ⅵ) by IRZ with GT-NZVI decreased with the increase of aquifer medium particle size,groundwater flow rate and ionic strength.Most of Cr(Ⅲ) as reduzate was adsorbed or immobilized on the surface or in the lattice of GT-NZVI,which indicated effective immobilization for chromium.

Al_(80)Ni_6Y_8Co_4Cu_2 GLASS ALLOYS CONTAINING NANOSCALEPARTICLES BY ISOTHERMAL ANNEALING OR QUENCHING

Al80Ni6 Y8 Co4 Cu2 amorphous ribbons were isothermally annealed and a mixed structure consisting of α-Al particle with a size of less than 15nm and Al3Ni compound with a size of about 30nm was obtained. The crystallization kinetics of Al80Ni6 Y8 Co4 Cu2 amorphous alloy shows that the precipitation of α-Al particles is the growth process controlled by diffusion of the solute elements rejected from the growing crystals. By quenching at different cooling rates, a mixed structure consisting of nanoscale α-Al particles and the remaining glass matrix or structure consisting of nanoscale particle (Al phase or Al3Ni compound) with a size of about 100nm was formed. The addition of Co elements and Cu elements to Al-Ni-Y alloy systems increases the glass formation ability of the alloy and the thermal stability of the supercooled liquid region against crystallization, which results from significant difference of atomic size, strong bonding nature among constituent elements and the low diffisivity of the solute elements due to the concentration gradient in the growing front of crystals.

Synthesis of Nanoscale Shell-core Titania Coated Silica Particles in the Presence of Polyether Polyamine and the Phase Transition

The nanoscale titania coated silica was prepared via a two-step precipitating approach, where the nanoscale silica nuclei were first prepared by passing an aqueous solution of sodium silicate through an ion-exchange resin bed, then coated with the precipitation from hydrolyzed butyl titanate in an ethanol-hexane mixture at a low pH value in the presence of poly(ethylene oxide) polyamine salt(PPA) at a high temperature of 90 ℃. In the second-step precipitating process, the spontaneously precipitated titania shell on the silica nuclei was stabilized in the suspension solution with the help of the adsorption of PPA on the particles. A possible precipitating mechanism was suggested. Furthermore, the amorphous titania shell could undergo crystallization from the amorphous to the anatase structure at a high temperature of 650 ℃, and a further phase transition from the anatase to the rutile structure in the different sintering processes at a rising temperature of 750 ℃.

Catalytic dechlorination of o-chlorophenol by nanoscale Pd/Fe

Transformation of chlorophenols by nanoscale bimetallic particles represents one of the latest innovative technologies for environmental remediation. Nanoscale Pd/Fe bimetallic particles were synthesized in the laboratory for treatment of o-chlorophenol. Most of the nanoscale particles are in the size range of 20—100 nm. BET specific surface area of the nanoscale Pd/Fe particles is 12.4 m2/g. In comparison, a commercially available Fe powder(<100 mesh) has a specific surface area of just 0\^49 m2/g. Batch experiments demonstrated that the nanoscale Pd/Fe bimetallic particles can effectively dechlorinate o-chlorophenol. Dechlorination efficiency is affected by the mass fraction of Pd in the bimetal, nanoscale Pd/Fe mass concentration and mixing intensity.

Dechlorination of disinfection by-product monochloroacetic acid in drinking water by nanoscale palladized iron bimetallic particle

Nanoscale palladized iron(Pd/Fe)bimetallic particles were prepared by reductive deposition method.The particles were characterized by X-ray diffraction(XRD),X-ray fluorescence(XRF),scanning electron microscope(SEM),transmission electron microscope(TEM),and Brunauer-Emmett-Teller-nitrogen(BET-N_2)method.Data obtained from those methods indicated that nanoscale Pd/Fe bimetallic particles containedα-Fe^0.Detected Pd to Fe ratio by weight(Pd/Fe ratio)was close to theoretical value. Spherical granules with diame...

High-ductility fine-grained Mg-1.92Zn-0.34Y alloy fabricated by semisolid and then hot extrusion

The combination of semisolid and hot extrusion processing was applied to refine the icosahedral quasicrystalline phase(I-phase) in an extruded Mg-1.92Zn-0.34Y(wt.%) alloy for the first time. The semisolid isothermal heat treatment transformed the micron-sized I-phase particles into nano lamellar eutectic(α-Mg + I-phase) with a lamellar spacing of ?86 nm. After subsequent hot extrusion at 250 ℃, the nano lamellar eutectic phases were broken into uniformly dispersed nanoscale I-phase particles. What’s more, the matrix microstructure was significantly refined with an equiaxed average grain size of 2.59 ± 0.81 μm, and an unusual texture component(most of the grains’ c-axis is parallel to the extrusion direction) was observed. The processed alloy exhibited a high tensile elongation to failure(EL) of 44 ± 2.6%with an ultimate tensile strength(UTS) of 258 ± 2.0 MPa and a tensile yield strength(TYS) of 176 ± 1.6 MPa at room temperature.The high ductility from the combined effects of the grain refinement, dispersion of nanoscale I-phase particles, and the unusual texture.The uniform dispersion of nanoscale I-phase particles could promote grain refinement by particle stimulated nucleation mechanism, and thus bring the unusual texture(where the c-axis is aligned parallel to the extrusion direction during dynamic recrystallization, which contributed to ductility).

Nanocrystallization of Al_(80) Ni_6Y_8Co_4Cu_2 amorphous alloy

Nanoscale α (Al) phase with a size of 15 nm was precipitated from Al 80 Ni 6Y 8Co 4Cu 2 amorphous ribbons after annealing. The microhardness increases with increasing the crystallization volume fraction of nanoscale α (Al) phase. The combination effect of alloy strengthening and dispersion strengthening is main reason for the increase of microhardness. The formation of intermetallic compound (Al 3Ni) with a small volume fraction leads to the decrease of microhardness resulting from the depletion of the solute elements in the residual amorphous matrix and the weakening of alloy strengthening. With increasing the volume fraction of intermetallic compound, microhardness increases again due to dispersion strengthening of nanoscale intermetallic compound. [

Optimizing synthesis conditions of nanoscale zero-valent iron （nZVI） through aqueous reactivity assessment

Nanoscale iron particles （nZVI） is one of the most important engineered nanomaterials applied to environmental pollution control and abatement. Although a multitude of synthesis approaches have been proposed, a facile method to screen the reactivity of candidate nZVI materials produced using different methods or under varying synthesis conditions has yet been established. In this study, four reaction parameters were adjusted in the preparation of borohydride-reduced nZVI. The reductive properties of the resultant nanoparticles were assayed independently using two model aqueous contaminants, Cu （II） and nitrate. The results confirm that the reductive reactivity of nZVI is most sensitive to the initial concentration of iron precursor, borohydride feed rate, and the loading ratio of borohydride to ferric ion during particle synthesis. Solution mixing speed, in contrast, carries a relative small weight on the reactivity of nZVI. The two probing reactions （i.e., Cu（II） and nitrate reduction） are able to generate consistent and quantitative inference about the mass-normalized surface activity of nZVI. However, the nitrate assay is valid in dilute aqueous solutions only （50 mg.L~ or lower） due to accelerated deactivation of iron surface at elevated nitrate concentra- tions. Additional insights including the structural and chemical makeup of nZVI can be garnered from Cu（II） reduction assessments. The reactivity assays investigated in this study can facilitate screening of candidate materials or optimization of nZVI production parameters, which complement some of the more sophisticated but less chemically specific material characterization methods used in the nZVI research.