Adsorption Capacity of Vitamin B12 and Creatinine on Highly-Mesoporous Activated Carbons Obtained from Lignocellulosic Raw Materials

Abstract

<jats:p>Enterosorbents are widely-used materials for human body detoxification, which function by immobilizing and eliminating endogenous and exogenous toxins. Here, activated carbons, obtained from the lignocellulosic raw vegetal materials of indigenous provenance, have been studied. Walnut shell and wood from local species of nuts and apple-trees were carbonized, and further activated at high temperatures with water vapors in a rotary kiln. A second activation was carried out, in a fluidized bed reactor, but for shorter times. The textural properties of the samples were determined from the adsorption isotherms of nitrogen at 77 K, allowing the obtaining of highly mesoporous materials, while the adsorption capacity permitted an essential rise of six to seven times in the maximal adsorption values of the metabolites, which was determined by the reactivation process. A kinetic study of vitamin B12 and creatinine immobilization was performed, the optimal immobilization time for the apple-tree wood reactivated carbons being 2 times longer than for those originating from walnut shells. An additional investigation was also performed in specific conditions that simulate the real environment of immobilization: the temperature of a febrile human body (at the temperature T = 38 °C) and the characteristic acidity of the urinary tract and stomach (at the pH of 5.68 and 2.53, respectively). The activated carbonic adsorbents studied here, together with the results of the immobilization studies, show that these procedures can conduct a good incorporation of some endogenous metabolic products, such as vitamin B12 and creatinine, therefore presenting a good opportunity for their use as forthcoming commercial enterosorbents.</jats:p>

Adsorption of uremic toxins using biochar for dialysate regeneration

“…The results indicate that RAC has a graphitelike structure, which is consistent with the XRD analysis results [40]. The peaks at 288.58 eV belonged to -COOH, which can form a hydrogen bond with creatinine and uric acid [38]. The N 1 s spectrum in Fig.…”

“…2C). The characteristic absorption peak at 3435 and 1625 cm −1 was attributed to the stretching vibration of the hydroxyl group, carbonyl, and the skeletal vibration of aromatic C = C bonds [37], while the adsorption bands of 2930 and 2853 cm −1 could be attributed to -CH 2 and -CH 3 groups [38]. These results indicated that the surface of the sample was rich oxygen-containing functional groups, which might form hydrogen bonds with creatinine and uric acid.…”

“…4D, it can be known that the adsorption process took place very quickly in the initial contact time (0 ~ 20 min) and then rapidly reached to the equilibrium state after 30 min, indicating that RAC has rapid creatinine removal efficiency. Normally, the pseudofirst-order and pseudo-second-order kinetics exhibit the information of reaction dynamics and adsorption types, e.g., chemisorption and physisorption [38]. From Fig.…”

“…6), experimental data, and kinetic and thermodynamic fitting results to elucidate the multiple interactions between the adsorbent and the adsorbate (Fig. 6): (i) the adsorption has occurred both because of interaction between the creatinine and uric acid dipole and the dipole induced in the porous surface, as well as because of dipole-dipole interaction between surface oxygen groups on the activated carbon surface and the uremic creatinine and uric acid [47]; (ii) the hydroxyl and carbonyl groups on the inner/outer surface of RAC would form with creatinine and uric acid by hydrogen bonding [38].…”

Mesoporous Carbons of Well-Organized Structure in the Removal of Dyes from Aqueous Solutions

“…The simple method of preparation of mesoporous activated carbons is a direct pyrolytic carbonization, followed by physical activation with gaseous agents (carbon dioxide, water vapour) [ 36 ]. To improve the mesoporous structure of the final product the second activation is advisable in a fluidized bed reactor [ 37 ]. The synthesis process conditions such as type of raw material, temperature, time and activation agent affect development of the internal structure of adsorbents.…”