Heavy Metal Removal from Industrial Effluents by Natural Fibers

The abilities of low-cost adsorbents such as waste leaves of tea, walnut shells, wheat straw, and rice straw to remove a range of metal ions from aqueous solution were evaluated. Studies were conducted as batch adsorption assays and adsorption experiments were carried out by shaking 0.5, 0.9, and 1.3g of adsorbents with 100 ml of synthetic wastewater. At the end of a preselected reaction time, one hour, the adsorbent were separated. The remaining concentration of heavy metal ions in each sample after adsorption was determined (in the case of cadmium and chromium using atomic absorption spectrometric method and in the case of aluminum using the Eriochrome cyanine R method). The abilities of these adsorbents to remove the heavy metal ions cadmium, chromium (VI), and aluminum from solution at three different concentrations, 5, 10, and 15mg/l were compared. The most useful adsorbents for the adsorption of cadmium, aluminum, and chromium (VI) for the metal ion with initial concentration of 5mg/l and the adsorbent dosage of 0.5 g were waste leaves of tea (max. 97.1%), walnut shells (max. 63.3%), and waste leaves of tea (max. 87.7%), respectively. The amount of adsorbed metal ions was dependent on their species and initial concentrations. The amount of adsorbed metal ions per unit weight of adsorbents increased with increasing concentration. The batch adsorption kinetics and adsorption equilibrium were examined and described by a first order reaction and Freundlich isotherm respectively.