Comparison of activated carbon and iron impregnated activated carbon derived from Gölbaşı lignite to remove cyanide from water

The ability of lignite-activated carbon (LAC) and iron-impregnated activated carbon (FeAC) obtained from Gölbaşı lignite to remove cyanide ions from aqueous solution by adsorption was researched and compared with each other. The same process was applied also with commercial activated carbons which are in both granular (CAC-1) and powder forms (CAC-2). The morphologies, structures and properties of the activated carbons were determined by BET, XRD, XRF, SEM, zeta meter and magnetometer, respectively. The effects of various experimental parameters, such as initial cyanide concentration, pH, adsorbent type and particle size were researched in a batch adsorption technique at a temperature of 25 °C. BET surface area of LAC is determined as 921 m2/g. The obtained magnetic activated carbon has high surface area of 667 m2/g with 19 wt.% Fe3O4 coated and perfect magnetic separation performance. Langmuir model was found to be the best representative for cyanide-adsorption. The maximum monolayer adsorption capacities of LAC and FeAC are 60.18 mg/g and 67.82 mg/g at pH values of 7–7.5 and 64.10 mg/g and 68.02 mg/g at pH values of 10–10.5, respectively. Kinetic evaluation indicated that the cyanide adsorption onto the obtained activated carbons followed the pseudo-second order rate reaction. The diffusion-controlled kinetic models on the cyanide-adsorbent system showed that the removal rate was controlled not only by intraparticle diffusion but also by film diffusion. All experimental results point out that the LAC and FeAC are viable candidates for the removal of cyanide from water and wastewater.

► Magnetic activated carbons have attracted great attention owing to separation from the medium by a simple magnetic process.
► Plain and magnetic activated carbons were obtained from Turkish lignite.
► Cyanide becomes a matter of considerable debates in Turkey.
► Cyanide is removed from an aqueous solution using plain and iron impregnated coal based activated carbons.