Ivona Nuić

The Effect of Zeolite Fixed Bed Depth on Lead Removal from Aqueous Solutions

Abstract The effect of zeolite bed depth on lead removal from aqueous solutions by the column method has been examined. The results indicate that the increase of bed depth delays the breakthrough point and exhaustion point, and increases the contact time of the zeolite – lead solution, and the height of the mass transfer zone, hz. The increase of the bed depth lowers the effect of axial dispersion on the mass transfer process. In order to predict the time necessary for exceeding the defined effluent concentration for a constant bed depth, the bed depth service time (BDST) approach has been used. Experimentally obtained breakthrough curves for the flow rate of 1 ml/min were used to derive the BDST approach equations. These equations were successfully used for modelling of the system for flow rates of 2 and 3 ml/min. The BDST equations have yielded modelled linear equations used for calculation of hz. The increase of the flow rate increases hz, which indicates that the zeolite–solution contact time is not sufficient. This may be attributed to the affect of axial dispersion on mass transfer on the solid-liquid interface.

Competitive removal of lead(II) and zinc(II) from a binary aqueous solution on a fixed bed of natural zeolite

Abstract The column method using a fixed bed of zeolite clinoptilolite was applied to remove lead and zinc ions from binary metal ions solutions. The raw zeolite sample used in this study was obtained from the Vranjska Banja deposit (Serbia) and contained more than 80% of clinoptilolite. The breakthrough curves have an S-shape for the total as well as for the single metal ions in binary solution. Lead and zinc ions bind simultaneously on the zeolite bed, and as the service cycle progresses lead ions displace a great portion of bound zinc. During the regeneration cycle, the quantity of lead desorbed is =15 times higher than the quantity of zinc, which means that mostly lead ions were bound on the zeolite. Breakthrough curves have been interpreted quantitatively by means of the Michaels method, and the results calculated have been compared with the results for single metal ions solutions.

Uptake of Pb and Zn from a binary solution onto different fixed bed depths of natural zeolite – the BDST model approach

Abstract The removal of lead and zinc from a binary solution by fixed bed depths (40, 80 and 120 mm) of a natural zeolite was examined at a flow rate of 1 mL/min. The results obtained were fitted to the Bed Depth Service Time (BDST) model and the parameters of the model (q and k) were used to design a column system for flow rates of 2 and 3 mL/min at a bed depth of 80 mm. The experimental results were in excellent agreement with those predicted and experimental breakthrough curves for the binary systems were obtained. This approach facilitates the design of effective binary column processes without additional experimentation. Two major design parameters, the Empty Bed Contact Time (EBCT) and the zeolite usage rate, were calculated. The highest EBCT value of 13.56 min represents the optimal conditions for the binary (Pb+Zn) solution.

Optimization of Removal Efficiency and Minimum Contact Time for Cadmium and Zinc Removal onto Iron-modified Zeolite in a Two-stage Batch Sorption Reactor

In highly congested industrial sites where significant volumes of effluents have to be treated in the minimum contact time, the application of a multi-stage batch reactor is suggested. To achieve better balance between capacity utilization and cost efficiency in design optimization, a two-stage batch reactor is usually the optimal solution. Thus, in this paper, a two-stage batch sorption design approach was applied to the experimental data of cadmium and zinc uptake onto iron-modified zeolite. The optimization approach involves the application of the Vermeulen’s approximation model and mass balance equation to kinetic data. A design analysis method was developed to optimize the removal efficiency and minimum total contact time by combining the time required in the two-stages, in order to achieve the maximum percentage of cadmium and zinc removal using a fixed mass of zeolite. The benefits and limitations of the two-stage design approach have been investigated and discussed.