Comparison of cadmium adsorption process on barley straw in batch and flow reactors

The aim of the study was to determine an influence of reactor types used in the cadmium adsorption process from aqueous solutions. During the study, a barley straw with the size in the range of 0.25-0.63 mm was used as a adsorbent. The adsorption was carried out in glass reactors with a capacity of 400 cm3 for the stationary process and in the plastic burettes with a capacity of 30 cm3 as flow reactors. The initial concentration of the solution was in the range of 5-30 mg/dm3. It was found that the optimum pH value for those reactions is 7 and the time necessary to achieve an adequate degree of purification is about 90 min for flow reactors and 2 h in the case of batch reactors. It was also found that for the process conducted in flow reactors, degrees of purification compared with batch reactors are much higher, and in the case of solutions with the pH 5, these differences can be up to 30%. Maximum cadmium removal from solution with the initial concentration 30 mg/dm3 was observed in the flow reactor at the pH of 7 and it was equal to 74.1% and for batch reactors that value was only 56.7%.