Background: Releasing of heavy metals in the environment caused by industrialization and urban, is a concern worldwide. Cadmium ion is toxic contaminants for Humans, Animals and plants that the maximum allowable concentration in water (0.005 mg/l) is defined by WHO. Different methods for removing heavy metals have been studied. In recent years, the use of low-cost adsorbent for removal of these metals has been considered by researchers. In this study, removal of cadmium ions from aqueous solutions with continues flow method was studied by prepared adsorbent from barley stems.

Methods: This experimental- laboratory study done in 2011. Barley stem particles in the range of 1.19 to 2 mm were investigated for removal of cadmium ions with continues down-flow by a column. All tests performed at constant pH of 6 and temperature of 27°C. The effective variables such as initial concentration, adsorbent bed height and inlet flow rate was studied for removal of cadmium ions. For each trial, value of 6 ml samples was collected at every 30 minutes of the output column. Cadmium ion concentration in each sample was measured with atomic absorption spectrophotometer.

Results: Test results showed that the absorption breakthrough curve related to the studied variables. Increasing flow rate and input concentration decreases the saturation point and breakthrough time but increase the depth of adsorbent bed makes it longer. Maximum uptake of cadmium ions was obtained 10.07mg/g in a flow3ml/min, bed depth 30cm, and initial concentration 30mg/l.

Conclusion: According to obtained results, increasing flow rate decreases the maximum of uptake of cadmium ions per gram of absorbent and the absorption efficiency. The input flow 2 ml/min on the adsorbent column with Barley stem was removed cadmium ions as well and also has a large absorption capacity. It is recommended that continuous flow method with the obtained parameters in this study be used in the chemically refining process.