Activated carbon prepared from coirpith, an agricultural solid waste by-product, has been used for the adsorption of Cd(II) from aqueous solution. Parameters such as the agitation time, metal ion concentration, adsorbent dose and pH were studied. The adsorption data fit well with the Langmuir and Freundlich isotherm models. The adsorption capacity (Q0) calculated from the Langmuir isotherm was 93.4 mg Cd(II)/g at an initial pH of 5.0 at 30 °C for the particle size 250–500 μm. The percent removal increased with pH from 2 to 4 and remained constant up to pH 10. Desorption studies were performed with dilute hydrochloric acid. Quantitative recovery of the metal ion is possible. The mechanism of adsorption seems to be ion exchange. As coirpith is discarded as waste from coir processing industries, the carbon is expected to be an economical product for metal ion remediation from water and wastewater.
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