Polyvalent metal ion adsorption by chemically modified biochar fibers

Uranium Isotope (U-232) Removal from Waters by Biochar Fibers: An Adsorption Study in the Sub-Picomolar Concentration Range

“…The interaction of uranium with biochar-based adsorbents has been widely studied using different biomass types as starting materials [ 1 , 2 , 3 , 4 ], including plant fibers, which in addition to their abundance and low value present desirable adsorbent properties such as a tubular structure and large external surface, allowing for fast material exchange and increased sorption capacities [ 5 , 6 , 7 , 8 , 9 ]. These physical properties remain almost intact after carbonization and chemical oxidation by nitric acid.…”

Removal of 241Am from Aqueous Solutions by Adsorption on Sponge Gourd Biochar

“…The associated kinetic data are summarized in Figure 1 and reveal that equilibrium was reached after 24 h. Therefore, subsequent experiments have been carried out allowing for 24 h contact time to assure equilibrium. In the sub-picomolar concentration range, equilibrium was reached after 24 h contact time, which is a significantly higher contact time compared to the few hours required at increased radionuclide/metal ion concentrations [ 7 , 8 , 9 , 24 , 38 ]. This is because at very low concentration levels, the diffusion of the radionuclide cations to the biochar surface is the adsorption rate determining step, and the mass transfer phenomena are reduced.…”

“…The solution pH strongly affects the sorption efficiency ( K d values), since both the Am 3+ species distribution in solution and the protonation/dissociation of the surface-active moieties of the biochar materials depend on the proton concentration. The latter applies to the π system–proton interaction and carboxylic dissociation for unmodified and oxidized biochar, respectively [ 20 , 21 , 22 , 23 , 24 ]. A schematic illustration of the interaction of Am 3+ cations with the aromatic (π-system) and the carboxylic groups on the biochar surface is given in Figure 2 .…”

“…The effect of pH on the Am 3+ adsorption by biochar fibers has been investigated and the corresponding log 10 K d values are summarized in Figure 3 . The oxidized biochar fibers (BC_ox) showed a much higher adsorption affinity for Am 3+ than their non-oxidized counterpart (BC), which may be attributed to the presence of a significantly higher concentration of oxygen-containing moieties (e.g., carboxylic groups) on the BC-ox surface [ 20 , 21 , 22 , 23 , 24 ]. Oxygen-containing moieties (e.g., phenolic, carboxylic groups) are hard Lewis bases and therefore exhibit a higher affinity for hard Lewis acids such as the Am 3+ cationic species.…”

“…A wide spectrum of physical, chemical, and biological processes has been developed and applied for the removal of radionuclides from the nuclear process and contaminated wastewaters including membrane and osmosis technologies, sorption and ion exchange, chemical precipitation, electroremediation, and bioremediation [ 8 ]. Adsorption technologies are of particular interest since effective adsorbents such as metal organic frameworks [ 9 ], aerogels [ 10 , 11 , 12 ], silica-based materials [ 13 ], polymers [ 14 , 15 ], biomasses [ 16 , 17 , 18 , 19 ], and carbon-based composites [ 20 , 21 , 22 , 23 , 24 , 25 ] can be prepared easily and at low-cost. One such material is biochar, prepared by the pyrolysis of residual dry biomass and agricultural waste.…”