Catalytic reduction of 4-nitrophenol using synthesized and characterized CoS@MorphcdtH/CoS@4-MPipzcdtH nanoparticles

CoS@MorphcdtH NPs and CoS@4-MPipzcdtH NPs were synthesized by precipitation method involving three mechanisms: inclusion, occlusion, and adsorption. The synthesized NPs were characterized with the help of UV-Vis spectroscopy, FESEM-EDAX, powder x-ray diffraction, TEM, ESIMS, TG/DSC analysis. The morphology of the CoS@MorphcdtH NPs and CoS@4-MPipzcdtH NPs were hexagonal and rectangular, and the particles were in the range 7–12 nm. UV–visible spectral measurements showed surface plasmon resonance at 320 nm–340 nm with band gap of 3.65 eV–3.86 eV. The catalytically active CoSNPs called were investigated for the reduction of 4-nitrophenol (4-NP) via hydrogenation using sodium borohydride (NaBH₄) as a reducing agent. Both the CoS NPs successfully reduced 4-NP to 4- aminophenol (4-AP) in a short time, catalytic performances are almost unchanged for the first five cycles. Herein, we report the preparation and characterizations of efficient active CoS NPs consisting carbodithioic acid framework as a support/capping material, along with catalytic property.     

The precipitation of iron (II) and nickel oxalates with alkaline-earth metal oxalates: Induction periods,nucleation rates and mechanisms

The coprecipitations of magnesium (and barium) iron(II) and nickel oxalate dihydrates were studied from excess magnesium and barium oxalate solutions. Nucleation rates were estimated from the induction periods for the coprecipitations. The nucleation rates in excess magnesium oxalate solutions first decreased with increasing excess oxalate anion concentration to minimum values and then increased with increasing magnesium cation concentration. At low to intermediate Mg/Fe(II) (and Mg/Ni) ratios the main nuclei were FeOx (and NiOx); at intermediate Mg/Fe(II) (and Mg/Ni) ratios the main nuclei were probably MgOx FeOx (and MgOx NiOx) mixtures and/or solid solutions of compositions Mg_αFe_{1 α}Ox (and Mg_αNi_{1 α}Ox); at high Mg/Fe(II) (and Mg/Ni) ratios the main nuclei were MgOx. The nucleation rates in excess barium oxalate solutions were similar to those for the precipitation of barium oxalate from supersaturated equivalent solutions. The main nuclei in most systems were BaOx.     

The precipitation of sparingly-soluble metal salts from aqueous solution: Heterogeneous nucleus numbers at low to intermediate supersaturation

The precipitation of series of alkaline-earth metal and transition hydroxides, sulphates, chromates and molybdates, hydrogen phosphate carbonates, oxalates and ‘oxinates’ were studied in aqueous solution of low to intermediate supersaturation. Heterogeneous nucleation probably occurred onto micro-crystalline particles of some siliceous mineral (of the trigonal, hexagonal or cubic system), dispersed in the solution. The heterogeneous nucleus numbers for these precipitations then depended on the rates of the heterogeneous nucleation onto these substrates and the rates of the mononuclear growth of nuclei to crystallites (during the induction periods). Generally, N_het values in polypropylene and glass beakers, at low supersaturation, varied from 10⁴ to 10¹³ dm⁻³: the N_het values then increased slightly with concentration and supersaturation according to the relation N_het = K_N^β, where K_N is a function of the metal salt surface energy and an ‘epitaxy’ factor; β = 0.4–0.5. In turn, at any supersaturation, log N_het = log N + Fσ, where N and F were constants for any precipitation: N_het values then increased from 10⁴ to 10⁸ times for increase in σ from 50 to 150 mJ m⁻². At any supersaturation and surface energy, N_het values increased in the order monoclinic < orthohombic < tetragonal < trigonal crystals.