Remoção de cadmio, chumbo e cobre utilizando zeolita natural clinoptilolita em coluna de leito fixo / Cadmium lead and Cooper removal using zeolite clinoptilolite in a fixed bed column

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

The removal of cadmium., lead and copper using natural zeolite Clinoptilolite was studied in a 13,3 em height and 1,4 em internal diameter fixed bed column. A prelirninary pH study was developed in order to detenninate the range in which ionic metal precipitation does not occur and pH 5 was found to be the adequate value for this purpose. A factorial design 22 with 3 center points was established in order to study the adsorption process of each metal individuaIly with what concerns the influence of the operation flow rate and feed concentration over the total metal removal capacity. The experimental design 1 was conducted to study cadmium removal. The lower values of flow rate and concentration factors were 10 mL/min and 200 ppm whereas the high values were 50 mL/min and 600 ppm respectively. The results were not satisfactOIyand a new design was set. The new experimental design 2 set lower factors to 15 mL/min and 400 ppm and higher values to 25mL/min and 600 ppm for cadnúum, lead and copper removal analysis. Concentration was found to be the most significant factor in the metais removal whilst higher concentrations result in bigher metal removal. The mass transfer zone (MTZ) was analyzed for the lead adsorption process, keeping the concentration constant and varying the flow rate. The lowest MTZ value was obtained with a flow rate of 20mL/min. The equilibrium data were correlated using Langmuir s isotherm model. The constants obtained were for lead removal: qmax = 200,54 mg of Leadlg of zeolite, b= 0,00223 mg/L; for cadmium removal: qmax = 84 mg of cadmium/g of zeolite, b= 0,0022 mg/L and for copper removal: qmax = 70,44 mg of copper/g of zeolite, b= 0,0021 mg/L. The model used to adjust the experimental results was proposed by Silva, 2001. Simulations were made on cadmium, lead and copper removal breakthrough curves. The equilibrium parameters used were based on experimental data obtained for the dynamic adsorption process of cadmium, lead and copper ofthe present work as well as Zambon s (2003) bateh lead adsorption. The simulation results involving the dynamic parameter data were satisfactory for ali the metais studied. In the case of lead simulations were also done based on the batch parameters and the results were not satisfactory. The mass transfer in the solid (K) was inHuenced by the initial concentration of all the metais in the studied range. The mixture tests were done using 15ml/min flow rate and a total metal concentration of 600ppm (113 and 2/3 ftactions). These data were ana1yzed in two distinct ways: first the metais synergic effects were evaluated, then a simplex-centroid design was developed. Through the analyzes of the synergic effects it was possible to notice that when the lead is present in the mixture with the other metais there is a great drop in their removal quantity up to more than 60%. The presence of the other metais in lead removal results in a removal capacity reduction of in to maximum of 25.24%. The simplex-centroid design indicated the lead is the most significant component in the mixture for total metal removal, the greater the lead concentration the greater the total meta! capacity removal is achieved. Cadmium and copper compositions also showed a significant positive effect over as well as the mixture of the three metais. The mixture of two metais of Cd+Cu and Cd+Pb on the other hand have a negative effect over the capacity removal

ASSUNTO(S)

modelos matematicos modeling zeolite clinoptilolite adsorção fixed bed adsorption metals mixture zeolitos metais pesados

ACESSO AO ARTIGO

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