Enhancing adsorption capacity of nano-adsorbents via surface modification: A review

In this review, the role of surface modification of nanoparticles to enhance their performance as adsorbents was explored. Performance was assessed by comparisons on adsorption capacities of differently modified nanoparticles (silica, iron, and alumina based nanoparticles) on different heavy metal ions (Cu, Cd, Co, Ni, Pb, As, Cr, Zn, Mn, and Hg). A comparison of pure and modified materials revealed that the modified materials gave superior adsorption capacities. A close relationship was observed between the various modification methods and the adsorption capacities of particles synthesized by hydrothermal methods giving the highest adsorption capacities. Surface modification also had a direct effect on the specific surface area which decreased with the degree of functionalization. The adsorption capacity was however generally observed to increase with the degree of functionalization.