Zhengyong Zhang

Leaching zinc from spent catalyst: Process optimization using response surface methodology

The spent catalyst from vinyl acetate synthesis contains large quantity of zinc. The present study attempts to leach zinc using a mixture of ammonia, ammonium carbonate and water solution, after microwave treatment. The effect of important parameters such as leaching time, liquid/solid ratio and the ammonia concentration was investigated and the process conditions were optimized using surface response methodology (RSM) based on central composite design (CCD). The optimum condition for leaching of zinc from spent catalyst was identified to be a leaching time of 2.50 h, a liquid/solid ratio of 6 and ammonia concentration 5.37 mol/L. A maximum of 97% of zinc was recovered under the optimum experimental conditions. The proposed model equation using RSM has shown good agreement with the experimental data, with a correlation coefficient (R(2)) of 0.95. The samples were characterized before and after leaching using X-ray diffraction (XRD), nitrogen adsorption and scanning electron microscope (SEM).

Process Optimization for the Preparation of Activated Carbon from Jatropha Hull Using Response Surface Methodology

Abstract Preparation of activated carbon has been attempted using CO2 as the activating agent from Jatropha hull, one of the popular feed stocks for biodiesel manufacture. The response surface methodology technique is utilized to optimize the process conditions. The influences of the three major parameters, activation temperature, activation time, and CO2 flow rate on the properties of activated carbon, are investigated using analysis of variance to identify the significant parameters. The optimum conditions for preparation of activated carbon has been identified to be an activation temperature of 950°C, activation time of 40 min, and CO2 flow rate of 500 ml/min, an iodine number of 1,008 mg/g, and a yield of 18% were obtained, respectively. The BET surface area evaluated using nitrogen adsorption isotherm for the optimal sample corresponds to a 1,207 m2/g, with the pore volume of 0.86 cc/g. The activated carbon is heteroporous with the micropore volume contributing to 58%.

Effects of microwave pretreatment on zinc extraction from spent catalyst saturated with zinc acetate

Abstract A new technology for microwave pretreatment of spent catalyst on Zn extraction by HCl leaching was proposed and the temperature-change curve of spent catalyst under microwave irradiation was measured. The influence of microwave pretreatment temperature and microwave irradiation time on zinc extraction was investigated and the mechanism of microwave pretreatment for spent catalyst was analyzed. The results show that microwave pretreatment can greatly enhance the leaching rate of Zn. The Zn extraction reaches 96.58% under the conditions of microwave pretreatment temperature of 950 °C and the microwave irradiation time of 12 min. The blocked pores of spent catalyst can be opened through microwave pretreatment, increasing the contact area of leaching reagent and zinc.

Non-isothermal microwave leaching kinetics and absorption characteristics of primary titanium-rich materials

Abstract The non-isothermal leaching kinetics of primary titanium-rich material by microwave heating was investigated, and the temperature-pressure curves of leaching system and microwave absorption characteristics of mixture solutions before and after leaching were measured. The research of non-isothermal kinetics was evaluated by the leaching rate of Fe and the total apparent velocity equation of the non-isothermal kinetics of leaching for primary titanium-rich material by microwave heating was obtained. It is shown from the temperature-pressure curves that the high temperature and high pressure of closed leaching system are favorable to the enhancement of the leaching rate of Fe. Microwave absorption characteristics of mixture solutions before and after leaching show that there are abrupt changes of microwave absorption characteristics for 15% HCl solution and the mixture solution after leaching by 20% HCl.