The present study dealt with the mechanism of competitive adsorption of Sb(Ⅲ)and Fe(Ⅱ)ions from a copper-containing aqueous solution on Purolite S957,a commercially available cationic ion-exchange adsorbent.Experime...The present study dealt with the mechanism of competitive adsorption of Sb(Ⅲ)and Fe(Ⅱ)ions from a copper-containing aqueous solution on Purolite S957,a commercially available cationic ion-exchange adsorbent.Experiments were conducted using aqueous copper sulfate solutions containing either single or conjoint ions,using both sedentary and batch adsorption techniques to ascertain the sensitivity of the adsorption process to variation in p H,mass of resin,contact time,and temperature as well as establishing the optimal range of variables for maximum ion removal.The data from single ion adsorption tests were fitted by non-linear regression techniques to Henry,Langmuir,Freundlich,Temkin,and Dubinin–Radushkevich isotherm models.Freundlich isotherm for Sb(Ⅲ)and Freundlich and Henry models for Fe(Ⅱ)solutions best express the adsorption equilibrium data;while for binary ion electrolytes,the extended Freundlich model fitted the data satisfactorily.The kinetic model adequately describing adsorption was shown to be the pseudo-first-order,underscoring the dominant role of physical adsorption playing in the process.Thermodynamic parameters for the adsorption process reveal differences in the Sb(Ⅲ)adsorption mechanism from single ion and Sb(Ⅲ)-Fe(Ⅱ)containing electrolytes.The adsorption of Sb(Ⅲ)alone is endothermic,whereas the process becomes exothermic in the Sb(Ⅲ)-Fe(Ⅱ)system.展开更多
The present study evaluates the reductive leaching of indium from indium-bearing zinc ferrite using oxalic acid as a reducer in sulfuric acid solution.The effect of main factors affecting the process rate,including th...The present study evaluates the reductive leaching of indium from indium-bearing zinc ferrite using oxalic acid as a reducer in sulfuric acid solution.The effect of main factors affecting the process rate,including the oxalic-acid-to-sulfuric-acid ratio,stirring rate,grain size,temperature,and the initial concentration of synergic acid,was precisely evaluated.The results confirmed the acceptable efficiency of dissolving indium in the presence of oxalic acid.The shrinking-core model with a chemical-reaction-controlled step can correctly describe the kinetics of indium dissolution.On the basis of an apparent activation energy of 44.55 kJ/mol and a reaction order with respect to the acid concentration of 1.14,the presence of oxalic acid was found to reduce the sensitivity to temperature changes and to increase the effect of changes in acid concentration.Finally,the equation of the kinetic model based on the factors under study is presented.展开更多
The leaching of rare earth elements （REEs） including cerium, lanthanum and neodymium from apatite concentrate obtained from iron ore wastes by nitric acid was studied. The effects of nitric acid concentration, soli...The leaching of rare earth elements （REEs） including cerium, lanthanum and neodymium from apatite concentrate obtained from iron ore wastes by nitric acid was studied. The effects of nitric acid concentration, solid to liquid ratio and leaching time on the recoveries of Ce, La and Nd were investigated using response surface methodology. The results showed that the acid concentration and solid to liquid ratio have significant effect on the leaching recoveries while the time has a little effect. The maximum REE leaching recoveries of 66.1%, 56.8% and 51.7% for Ce, La and Nd, respectively were achieved at the optimum leaching condition with 18% nitric acid concentration, 0.06 solid to liquid ratio and 38 min leaching time. The kinetics of cerium leaching was investigated using shrinking core model. It was observed that the leaching is composed of two stages. In the first stage a sharp increase in cerium leaching recovery was observed and at the longer time the leaching became slower. It was found that in the first stage the diffusion of reactants from ash layer is the rate controlling mechanism with an apparent activation energy of 6.54 kJ/mol, while in the second stage the mass transfer in the solution is the controlling mechanism.展开更多
文摘The present study dealt with the mechanism of competitive adsorption of Sb(Ⅲ)and Fe(Ⅱ)ions from a copper-containing aqueous solution on Purolite S957,a commercially available cationic ion-exchange adsorbent.Experiments were conducted using aqueous copper sulfate solutions containing either single or conjoint ions,using both sedentary and batch adsorption techniques to ascertain the sensitivity of the adsorption process to variation in p H,mass of resin,contact time,and temperature as well as establishing the optimal range of variables for maximum ion removal.The data from single ion adsorption tests were fitted by non-linear regression techniques to Henry,Langmuir,Freundlich,Temkin,and Dubinin–Radushkevich isotherm models.Freundlich isotherm for Sb(Ⅲ)and Freundlich and Henry models for Fe(Ⅱ)solutions best express the adsorption equilibrium data;while for binary ion electrolytes,the extended Freundlich model fitted the data satisfactorily.The kinetic model adequately describing adsorption was shown to be the pseudo-first-order,underscoring the dominant role of physical adsorption playing in the process.Thermodynamic parameters for the adsorption process reveal differences in the Sb(Ⅲ)adsorption mechanism from single ion and Sb(Ⅲ)-Fe(Ⅱ)containing electrolytes.The adsorption of Sb(Ⅲ)alone is endothermic,whereas the process becomes exothermic in the Sb(Ⅲ)-Fe(Ⅱ)system.
文摘The present study evaluates the reductive leaching of indium from indium-bearing zinc ferrite using oxalic acid as a reducer in sulfuric acid solution.The effect of main factors affecting the process rate,including the oxalic-acid-to-sulfuric-acid ratio,stirring rate,grain size,temperature,and the initial concentration of synergic acid,was precisely evaluated.The results confirmed the acceptable efficiency of dissolving indium in the presence of oxalic acid.The shrinking-core model with a chemical-reaction-controlled step can correctly describe the kinetics of indium dissolution.On the basis of an apparent activation energy of 44.55 kJ/mol and a reaction order with respect to the acid concentration of 1.14,the presence of oxalic acid was found to reduce the sensitivity to temperature changes and to increase the effect of changes in acid concentration.Finally,the equation of the kinetic model based on the factors under study is presented.
文摘The leaching of rare earth elements （REEs） including cerium, lanthanum and neodymium from apatite concentrate obtained from iron ore wastes by nitric acid was studied. The effects of nitric acid concentration, solid to liquid ratio and leaching time on the recoveries of Ce, La and Nd were investigated using response surface methodology. The results showed that the acid concentration and solid to liquid ratio have significant effect on the leaching recoveries while the time has a little effect. The maximum REE leaching recoveries of 66.1%, 56.8% and 51.7% for Ce, La and Nd, respectively were achieved at the optimum leaching condition with 18% nitric acid concentration, 0.06 solid to liquid ratio and 38 min leaching time. The kinetics of cerium leaching was investigated using shrinking core model. It was observed that the leaching is composed of two stages. In the first stage a sharp increase in cerium leaching recovery was observed and at the longer time the leaching became slower. It was found that in the first stage the diffusion of reactants from ash layer is the rate controlling mechanism with an apparent activation energy of 6.54 kJ/mol, while in the second stage the mass transfer in the solution is the controlling mechanism.
