Adsorption of nickel (II) from aqueous solutions with clay-supported nano-scale zero-valent iron synthesized from green tea extract

Nano zerovalent iron (nZVI) supported adsorbents have been reported as suitable candidates for adsorption of water contaminants. However, the role of and interplay between surface chemistry, functional group density and textural properties has largely been unexplored. In this work, green tea derived nano zerovalent iron (nZVI) supported clay hybrid material (CnZVI) was used as a novel adsorbent for the removal of Ni2+ ions from water. The unmodified natural clay (Arg) and the CnZVI composite were characterized using FTIR, SEM, TGA and BET techniques. Incorporation of nZVI ameliorated the specific surface area from 16.88 to 30.46 m(2)/g, translating to similar to 80 % increase. This translated to similar to 69 % increase in maximum adsorption capacity from 8.47 to 14.38 mg/g, respectively. The addition of nZVI in the clay decreased the affinity (K-F) for Ni2+ by similar to 48 %. The disparity between the percent increase in surface area (similar to 80 %) and the adsorption capacity (similar to 69 %) implies the adsorption of Ni2+ was significantly controlled by textural properties compensating for the antagonistic effects of functional group density. The kinetic rates were best predicted by the pseudo-first-order and Elovich's models for the Arg and CnZVI, respectively, implicit evidence of the role of surface chemistry. A maximum adsorption capacity of 14 mg/g was achieved for 100 mg Ni2+/L in 120 min for CnZVI.