Will nano-biosorbents break the Achilles’ heel of biosorption technology?

Abstract

Release of toxic substances into public waterways continues unabated, despite concerted efforts to minimize environmental pollution. In particular, heavy metals and dyes are problematic due to their toxicity and persistence in the environment. As a consequence, remediation technologies such as biosorption have been designed, but biosorption applications have rarely been used at industrial levels. More recently, research has sought to harness the unique properties of nanotechnology by developing biosorbents at nanoscale, e.g. nano-biosorbents. Here I review principles and applications of nano-biosorbents. The major points are the following: (1) nano-biosorbents offer unique properties such as high surface area, which boosts the chemical activity and adsorption capacity, increase surface binding energy, and reduce internal diffusion resistance; (2) performances of nano-biosorbents are improved by encapsulation of nano-biosorbents in materials such as alginate polymers, chemical and biological modification of the raw biomass, and magnetic modification by incorporating materials such as magnetite; (3) use of nanoparticles with magnetic properties allows for rapid and efficient separation by using an external magnetic field, thus presenting a possibility for online separation and point-of-use water purification as well as sorbate and biosorbent recovery; (4) green engineered nanoscale zero-valent metals such as zero-valent iron and zero-valent silver have shown greater potential due to their high reducibility and large specific surface area; and (5) nano-biosorbents have shown great potential for the removal of dyes and heavy metals, and for the recovery of precious metals.