Zinc Recovery from Wulagen Sulfide Flotation Plant Tail by Applying Ether Amine Organic Collectors

Separating oxidized zinc minerals from flotation tailings is always a challenge. In this study, a flotation tailing from Wulagen zinc mine in China (Zn grade < 1%) was processed using froth flotation with combinations of amines (OPA 10, OPA 1214, OPA 13, DDA) and Na2S to study the effects of these amines on the zinc recovery as well as their interactions with other reagents, aiming to screen out a proper reagent scheme to improve zinc separation from extremely low-grade zinc flotation tailings. The results show that different amines led to different flotation performance, and the collectors were ranked as OPA 1214, OPA 13, OPA 10 and DDA in a decreasing order based on flotation collectivity and selectivity. An increase in the concentration of each collector increased the zinc recovery but reduced the concentrate zinc grade. Interactions were also observed between different amines and Na2S and Na2SiO3, and OPA 1214 outdid the others in saving the usage of both the Na2S and Na2SiO3. The measured adsorption of collector onto smithsonite was found to correlate well with flotation test results. It was concluded that hydrocarbon chains can be held accountable for the difference in the flotation performance with different amines. The longer the hydrocarbon chain, the stronger the hydrophobic association ability of amine, which is conducive to the selective amine adsorption onto sulfurized smithsonite particles and hence the smithsonite flotation.

HYDRODENITROGENATION OF 2-METHYL QUINOLINE - EFFECT OF STERIC HINDRANCE IN LIQUID PHASE CATALYTIC HYDROGENATION

Hydrodenitrognation (HDN) of 2-methyl quinoline (quinaldine) and quinoline in liquid phase on S-NiMo/a-Al2O3 catalyst was carried out in a batch reactor at 3.0 - 10.0 MPa and 130 � 360oC in Poly alpha-olefin solvent. Hydrogenolysis and Hydrogenation results in formation of products such as 1,2,3,4-treta hydro Quinaldine (1-THQ), 5,6,7,8-terta hydro Quinaldine (5-THQ), Deca hydro Quinaldine (DHQ), Butyl cyclohexane (BCH), Butyl cyclo hexene (BCHE) and butyl benzene (BB). Under studied condition, amine rings of quinaldine was rapidly hydrogenated and it forms relevant quasi equilibrium with 1,2,3,4-treta hydro quinaldine (1-THQ), 5,6,7,8-terta hydro quinaldine(5-THQ) and Deca hydro quinaldine (DHQ). The quinaldine reaction path either 1-THQ or 5-THQ indicated dependent of temperature and independent of partial pressure. Over which amine adsorption on metal sites reduced due to steric hindrance of methyl-group adjacent to N-bonding and increases the rate of intermediate formation through benzene ring hydrogenation. Distinguished HDN hydrogenolysis mechanism of quinaldine and its intermediate compounds were studied and compared with quinoline HDN. Thus, 5-THQ to DHQ and C-N cleavage identified as rate limiting step through steric hindrance HDN mechanism.

Au/TiO2 nanobelts: thermal enhancement vs. plasmon enhancement for visible-light-driven photocatalytic selective oxidation of amines into imines

Au NPs improve the photocatalytic activity of TiO2 only in a low temperature range. Excessive Au NPs loaded on TiO2 inhibit the photocatalytic amine conversion due to the decreased oxygen vacancies and poor amine adsorption ability.

Eley–Rideal model of heterogeneous catalytic carbamate formation based on CO 2 –MEA absorptions with CaCO 3 , MgCO 3 and BaCO 3

The mechanism was proposed of heterogeneous catalytic CO 2 absorptions with primary/secondary amines involving ‘catalytic carbamate formation’. Compared with the non-catalytic ‘Zwitterion mechanism’, this Eley–Rideal model was proposed for CO 2 + RR′NH with MCO 3 (M = Ca, Mg, and Ba) with four elementary reaction steps: (B1) amine adsorption, (B2) Zwitterion formation, (B3) carbamate formation, and (B4) carbamate desorption. The rate law if determining step of each elementary step was generated based on ‘steady-state approximation’. Furthermore, the solid chemicals were characterized by SEM and BET, and this rate model was verified with 39 sets of experimental datasets of catalytic CO 2 –MEA absorptions with the existence of 0–25 g CaCO 3 , MgCO 3 and BaCO 3 . The results indicated that the rate-determining step was B1 as amine adsorption onto solid surface, which was pseudo-first-order for MEA. This was the first time that the Eley–Rideal model had been adopted onto the reactions of CO 2 + primary/secondary amines over alkaline earth metal carbonate (MCO 3 ).