Greener and facile synthesis of Cu/ZnO catalysts for CO2 hydrogenation to methanol by urea hydrolysis of acetates

Sodium- and nitrate-free hydroxy-carbonate precursors were prepared via urea hydrolysis co-precipitation of acetate salt, which is simpler with fewer steps, even without the need for a washing and pH control, rendering the synthesis more sustainable.

Chemical precipitation of heavy metals from wastewater by using the synthetical magnesium hydroxy carbonate

Heavy metal pollution has become one of the most serious environmental problems today. The preparation of magnesium hydroxy carbonate from low-grade magnesite, and the chemical precipitation of heavy metal wastewater with magnesium hydroxy carbonate as precipitating agent were undertaken. The removal efficiencies of heavy metals were improved by increasing the dose of magnesium hydroxy carbonate, and the applicable dose of magnesium hydroxy carbonate was 0.30 g for 50 mL of the wastewater (6,000 mg/L). The precipitation reactions proceeded thoroughly within 20 min. At this time, the removal efficiencies of heavy metals were above 99.9%. The final pH value was 7.1, the residual VO2+, Cr3+ and Fe3+ concentrations were 0.01, 0.05 and 1.12 mg/L, respectively, which conformed to the limit of discharge set by China (0.5–2.0 mg/L, GB 8978–1996). The precipitate was mainly composed of Fe2O3, V2O5 and Cr2O3, which can be recycled as secondary raw material for metallurgical industry. The treatment of the heavy metal wastewater with magnesium hydroxy carbonate was successful in decreasing the concentrations of VO2+, Cr3+ and Fe3+ in wastewater.

Contrasting In Vitro Apatite Growth from Bioactive Glass Surfaces with that of Spontaneous Precipitation

Body-fluid-exposed bioactive glasses (BGs) integrate with living tissues due to the formation of a biomimetic surface layer of calcium hydroxy-carbonate apatite (HCA) with a close composition to bone mineral. Vast efforts have been spent to understand the mechanisms underlying in vitro apatite mineralization, as either formed by direct precipitation from supersaturated solutions, or from BG substrates in a simulated body fluid (SBF). Formally, these two scenarios are distinct and have hitherto been discussed as such. Herein, we contrast them and identify several shared features. We monitored the formation of amorphous calcium phosphate (ACP) and its crystallization into HCA from a Na 2 O–CaO–SiO 2 –P 2 O 5 glass exposed to SBF for variable periods out to 28 days. The HCA growth was assessed semi-quantitatively by Fourier transform infrared spectroscopy and powder X-ray diffraction, with the evolution of the relative apatite content for increasing SBF-exposure periods evaluated against trends in Ca and P concentrations in the accompanying solutions. This revealed a sigmoidal apatite growth behavior, well-known to apply to spontaneously precipitated apatite. The results are discussed in relation to the prevailing mechanism proposed for in vitro HCA formation from silicate-based BGs, where we highlight largely simultaneous growth processes of ACP and HCA.

Composition-dependent in vitro apatite formation at mesoporous bioactive glass-surfaces quantified by solid-state NMR and powder XRD

Solid-state NMR and powder XRD are employed to quantify the ACP (amorphous calcium phosphate) and HCA (hydroxy-carbonate apatite) components grown from three mesoporous bioactive glasses with variable compositions.

Morpho-structural and luminescence investigations on yttrium silicate based phosphors prepared with different precipitating agents

Yttrium silicate doped with cerium (Y2SiO5:Ce) was obtained from Y-Ce-Si based precursors prepared by the simultaneous addition of reagents (SimAdd) technique. The synthesis of the precursors was done in well controlled conditions using ammonium oxalate, ammonium carbonate or urea as precipitating agents. Results regarding the influence of precipitating agents on the morpho structural and photoluminescent characteristics of Y2SiO5:Ce are reported. The TG analysis in correlation with EGA, FT-IR and XRD investigations reveals the formation of oxalate, hydroxy-carbonate or hydroxy-nitrate based compounds, the same as the conversion of the precursors to well crystallized yttrium silicate. XRD patterns show that the precursors are amorphous except for the sample prepared with ammonium oxalate. Depending on the precipitation conditions, the phosphors phase composition varies from single phase (X2-Y2SiO5) to a mixture of phases (X2-Y2SiO5, X1-Y2SiO5, Y2O3). Under UV excitation, phosphors exhibit the specific blue emission of cerium with an intensity that varies from 175.8% (urea) to 96.0% (ammonium carbonate) and to 78.5% (ammonium oxalate). The emission intensity depends on the phase purity and order degree of the phosphors. PACS Classification codes:78.55 Hx, 81.20Fw