Removal of Various Pollutants from Wastewater Using Plasma-Modified Lignocellulose-Derived as a Low-Cost Adsorbent: An Overview

In their search for an alternative to commercial adsorbents, much research is turned to the local biomass-based materials such as agricultural residues and assimilated derivatives. However, natural biomass due to its low specific surface area must first undergo several pre-treatments. Among the newly emerging electric techniques for environmental applications, those who operate at atmospheric pressure (Non-thermal plasma) have recently found many breakthrough applications arising from their easy use with no extra additional reagents and their high reactivity. The Non-thermal plasma treatment of biomass is one of the promising developed approaches mainly due to significant effects including the formation of micro and macrospores, the increase of surface roughness, and surface functionalization. The most used plasma is non-thermal, so as not to denature the biomass, likewise the hot plasma can burn and/or destroy high contains carbon biomaterials. Especially, the gliding arc plasma obtained using moisten air as feeding gas, which is known to induce acidifying and oxidizing effects in an aqueous target. The primary species HO• radicals [E° (HO•/H2O) = 2.85 V/SHE] mainly formed in the arc will be with the dimer H2O2 [E°(H2O2/H2O) = 1.76 V/SHE] the determining agents for the chemical reactions induced. Exposure of a target to this kind of environment is likely to promote great surface transformations. This approach has some advantages: (i) the merit of not using commercial chemical reagents, the reactive species being in situ generated; (ii) the risks related to the manipulation of the products, the plasma reactor is robust and can be modulated to treat large quantity; (iii) the efficiency of the bi-functionality of the plasma (acidifier and oxidative). In this review, we will highlight the main changes induced by exposure of biomass to plasma treatment and also make a comparative study between chemically and plasma-activated materials in the removal of various pollutants from aqueous solution; and finally, we summarize the findings in the existing literature.