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Granular Activated Carbon (GAC), a commercial adsorbent for the removal of heavy metals was treated chemically with potassium bromate for it's surface modification and it's adsorption capacity was investigated with nickel ions. There was an increase in the adsorption capacity of the modified carbon by 90-95% in comparison to the raw granular activated carbon towards nickel ion adsorption. Potassium Bromate oxidation treatment was employed for a period of about 30 mins initially followed by 60 mins and the oxidized carbons were adsorbed with nickel ions. Metal sorption characteristics of as received and modified activated carbons were measured in batch experiments. Batch adsorption was successfully modeled by Langmuir Isotherm Model which indicates monolayer adsorption. The adsorption isotherms also fit well to the Freundlich Model. Effects of pH of initial solution, time of oxidation and mode of treatment on the adsorption process were studied. Experimental results showed that metal uptake increased with an increase in pH and oxidation time. The samples were characterized by Scanning Electron Microscope (SEM) studies and surface area analyzer.

The adsorption of Chromium(VI) from aqueous solutions was studied on different commercial grades of granular activated carbon namely Filtrasorb F‐400, F‐300, F‐200 and F‐100. The adsorption of Chromium (VI) on F‐400 carbon was found to be maximum in comparison to the other grades of carbon. The Chromium (VI) adsorption process in dilute aqueous solutions agreed with the Langmuir and Freundlich models and also obeyed first order kinetics. Metal sorption characteristics of as received activated carbons were measured in batch experiments. The maximum removal (60–65%) for different grades of raw carbon was observed at 25 °C with an initial concentration of 15.16 mg dm−3. It is evident from the study that granular activated carbon holds a particular promise in the removal of metal ions from aqueous solutions.

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